Honda Car Forum

Randolph <trash@junkmail.com> floridly penned in
news:41AAA7CB.5F86998E@junkmail.com:


> Doing it on a car with a synchronized transmission does not reduce
> wear on the clutch, but it reduces wear on the synchros. If your
> synchros are already worn out, double-clutching will allow you to
> shift with less clunking and grinding, particularly on down-shifts.
>


Double-clutching specifically does not reduce wear on the clutch, but the
throttle-press that is used in double-clutching is also used when rev-
matching the clutch, so that DOES reduce clutch wear.

--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

Abeness <news@nada.x> floridly penned in news:17SdnSKFO-5gAjfcRVn-
3A@rcn.net:

> TeGGer® wrote:
>> As of today, 237,811 miles (and counting) on my original. Owned the car
>> since new, too.
>
> Whew! Sure wish I could take a ride with you to learn how to do it
> properly! Not that I've worn out a clutch yet, but the previous owner
> had hers replaced at a mere 81K, I bought it at 112K, and have no
> illusions that I'm an expert at shifting--I may be doing it right, might
> be less-than-perfect. At least I don't ever smell that clutch-burning
> smell... ;-) Anyway, I'm still working out the occasional kinks after 8
> yeasr with an automatic.
>


Driving environment helps too. My driving is mostly highway, so the clutch
gets little use until I've left the highway.

jimbeam's tips are right-on, though; he says what I already do; the clutch
is NOT a hill-holder and it is NOT a brake pad.

What you're trying for when you do use the clutch is to use it sparingly
and with minimal slip. You want the quickest, smoothest engagement possible
with the least slip you can achieve. When you're stopped at a light, the
shifter is in neutral and your foot is OFF the pedal.

If you're timing your shifts right, there will be essentially zero wear on
the clutch when the car is moving. The only wear will occur when you're
actually getting the car started from rest. Keep that wear down and the
clutch will last ages.

I knew a guy who used to wear out his clutches every 90K miles or less. I
used to wonder why until I went for a ride with him once, then I saw
*exactly* why he wore them out: Everything jimbeam says NOT to do, he was
doing it! He was one of those people who used the clutch to hold the car
still on inclines, letting the car roll back, then blipping the clutch to
bring it forwards again, roll back, blip forwards, etc, etc, etc. Yeesh.


--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

"jim beam" <nospam@example.net> wrote
> Abeness wrote:
> > TeGGer® wrote:
> >> "Downshifting" without double-clutching is not smart. You are NOT
> >> supposed to use the clutch as a brake pad.
> >>
> >> Downshift properly and there is zero wear on the friction disc.
> >
> >
> > I've heard here that double-clutching means putting it in neutral
> > between shifts and letting the clutch out (i.e., releasing the pedal),
> > but wouldn't the point be to simply rev-match (approximately, after long
> > experience) before engaging at the lower gear, to reduce the wear on the
> > clutch?
>
> there's no real wear on the clutch from shifting, whether just relying
> on synchros or double clutching. clutch wear comes from drive-away from
> a standstill, holding it on the clutch on hills, "resting" a foot on the
> clutch pedal on the freeway, etc. if you don't peel away from lights,
> use the parking brake on hills & rest your foot on the floor, there's no
> reason a clutch won't last like tegger's is doing. also don't under
> rate a dealer's hunger for recommending unnecessary work.

Before I saw Jim's post and mention of the "synchro," I was torn about

1. wear on clutches from shifting
2. the need to double-clutch

Speaking as someone who's never "DIY replaced" a clutch, the "synchro" piqued my
interest. The reports I am seeing say that modern synchros (about the last
twenty years or so?) preclude the need to double clutch (as many of you I'm sure
have heard). For example:

1.
"In modern cars double-clutching is replaced by a synchronizer."
http://www.angelfire.com/hiphop3/ppd.../ManTrans.html

2.
"Manual transmissions in modern passenger cars use synchronizers to eliminate
the need for double-clutching." http://auto.howstuffworks.com/transmission6.htm

3.
"Today, all manual transmissions have 'synchros,' so double clutching is
completely unnecessary. And in fact, it DOES put extra wear and tear on the
clutch because you're using it twice for every shift instead of once."
http://www.cartalk.com/content/colum...cember/11.html

4.
" 'Synchronizers' in manual transmissions in modern passenger cars, eliminate
the need for double-clutching." http://www.automotiveforchicks.com/?page=tips

I did see some arguments (one?) about using double clutching to spare wear on
the synchro. OTOH, the synchro might be something that lasts the life of a car.
I didn't quite get resolution on this.

At the moment I am under the impression that the really big wear item in, say,
circa 1988-1995 Civics with manual transmissions (which seems to include my 91
Civic and possibly going back a few years more) may be the clutch release
bearing. It wears with every depress-and-release of the clutch pedal. Also
riding the clutch pedal between shifts or keeping it depressed at stops will
wear it.

I am still a little intrigued about the argument that 'the clutch is being used
as a brake pad when one downshifts.' Seems to me that engine inertia is being
used as a brake pad, and engines are iron horses that can take it for a design
life of say 15 years and 250k miles plus.. For now, I suppose the real argument
against downshifting as a means of slowing the car down is that many, when
downshifting from 5th gear to 1st to neutral, will use the clutch say five
times. Compare this to shifting from 5th to neutal and using the disc/drum
brakes on the wheels; the clutch is used once. Downshifting translates to using
the release bearing several times more each time the car comes to a stop.

And again, correct me if I'm wrong, but apart from downshifting, driving style
will have an impact on clutch life as well. E.g. shifting very quickly.

Caroline wrote:
> "jim beam" <nospam@example.net> wrote
>
>>Abeness wrote:
>>
>>>TeGGer® wrote:
>>>
>>>>"Downshifting" without double-clutching is not smart. You are NOT
>>>>supposed to use the clutch as a brake pad.
>>>>
>>>>Downshift properly and there is zero wear on the friction disc.
>>>
>>>
>>>I've heard here that double-clutching means putting it in neutral
>>>between shifts and letting the clutch out (i.e., releasing the pedal),
>>>but wouldn't the point be to simply rev-match (approximately, after long
>>>experience) before engaging at the lower gear, to reduce the wear on the
>>>clutch?
>>
>>there's no real wear on the clutch from shifting, whether just relying
>>on synchros or double clutching. clutch wear comes from drive-away from
>>a standstill, holding it on the clutch on hills, "resting" a foot on the
>>clutch pedal on the freeway, etc. if you don't peel away from lights,
>>use the parking brake on hills & rest your foot on the floor, there's no
>>reason a clutch won't last like tegger's is doing. also don't under
>>rate a dealer's hunger for recommending unnecessary work.
>
>
> Before I saw Jim's post and mention of the "synchro," I was torn about
>
> 1. wear on clutches from shifting
> 2. the need to double-clutch
>
> Speaking as someone who's never "DIY replaced" a clutch, the "synchro" piqued my
> interest. The reports I am seeing say that modern synchros (about the last
> twenty years or so?) preclude the need to double clutch (as many of you I'm sure
> have heard). For example:

changing a clutch is a procedural pita because of access, but it's not
technically hard. the cam belt is technically much more involved even
though access is much easier.

>
> 1.
> "In modern cars double-clutching is replaced by a synchronizer."
> http://www.angelfire.com/hiphop3/ppd.../ManTrans.html
>
> 2.
> "Manual transmissions in modern passenger cars use synchronizers to eliminate
> the need for double-clutching." http://auto.howstuffworks.com/transmission6.htm
>
> 3.
> "Today, all manual transmissions have 'synchros,' so double clutching is
> completely unnecessary. And in fact, it DOES put extra wear and tear on the
> clutch because you're using it twice for every shift instead of once."
> http://www.cartalk.com/content/colum...cember/11.html
>
> 4.
> " 'Synchronizers' in manual transmissions in modern passenger cars, eliminate
> the need for double-clutching." http://www.automotiveforchicks.com/?page=tips

hmm, automotiveforchicks propagating old lore about the 3000 mile oil
change & changing transmission fluid "every 100,000 kms or 32,500 miles"
has got to challenge their credibility.

>
> I did see some arguments (one?) about using double clutching to spare wear on
> the synchro. OTOH, the synchro might be something that lasts the life of a car.
> I didn't quite get resolution on this.

generally, synchros do last the life of the car. some of the old types
of synchro, notably some of the early porsche designs, were great for
racing & fast forced shifts, but they wore quickly, particularly if
there were problems with insufficient clutch disengagement [clutch plate
not being sufficiently free to "float" on the drive pinion], then they'd
check out pretty darned quick. the current cone clutch design of
synchro just shrugs off bulk abuse.

if you want a conclusive demo on the value of synchros/double-clutching,
drive something like a cement truck. the transmissions on those things
are fully synchroed, but you need to be built like arnie to shift them
unless you double-clutch. so, yes, double-clutching spares some of the
spinning gear momentum the synchros would otherwise have to deal with,
but on something like a honda, with a light transmission, light
viscosity gear lube and pretty much "fool proof" design, i wouldn't
waste any bandwidth worrying about it.

>
> At the moment I am under the impression that the really big wear item in, say,
> circa 1988-1995 Civics with manual transmissions (which seems to include my 91
> Civic and possibly going back a few years more) may be the clutch release
> bearing. It wears with every depress-and-release of the clutch pedal. Also
> riding the clutch pedal between shifts or keeping it depressed at stops will
> wear it.

the thrust bearing should last at least the life of the clutch. if a
clutch is badly adjusted or the driver "rides" the clutch pedal all the
time, it will wear more quickly, but i wouldn't worry about it. you've
got this far, so i doubt your driving habits are bad.

>
> I am still a little intrigued about the argument that 'the clutch is being used
> as a brake pad when one downshifts.' Seems to me that engine inertia is being
> used as a brake pad, and engines are iron horses that can take it for a design
> life of say 15 years and 250k miles plus..

correct, it's the engine that does the braking, not the clutch.

> For now, I suppose the real argument
> against downshifting as a means of slowing the car down is that many, when
> downshifting from 5th gear to 1st to neutral, will use the clutch say five
> times. Compare this to shifting from 5th to neutal and using the disc/drum
> brakes on the wheels; the clutch is used once. Downshifting translates to using
> the release bearing several times more each time the car comes to a stop.

shifting down through the gears is not that big a deal. consider the
principle of the relative loads; can you "chirp" the drive wheels
downshifting? no? then there's not as much load as chirping on the
up-shift.

you don't "need" to go 5-4-3-2-1 by the way. 5-3-1 is perfectly ok.
braking in neutral is potentially very dangerous. not only are you in
no position to apply power if required, you also have no engine braking.
again, going back to the cement truck, losing brakes on a fully loaded
vehicle because they've overheated on a big descent is no joke. trust
me on that. engine braking may not be "necessary" in all situations,
but to get out of the habit is a big no-no.

>
> And again, correct me if I'm wrong, but apart from downshifting, driving style
> will have an impact on clutch life as well. E.g. shifting very quickly.

shifting fast has a positive effect on the clutch [if any] but negative
on the synchros.

"Caroline" <caroline10027remove@earthlink.net> floridly penned in
news:SSIqd.3692$6K5.3562@newsread2.news.atl.earthl ink.net:


> Before I saw Jim's post and mention of the "synchro," I was torn about
>
> 1. wear on clutches from shifting
> 2. the need to double-clutch
>
> Speaking as someone who's never "DIY replaced" a clutch, the "synchro"
> piqued my interest. The reports I am seeing say that modern synchros
> (about the last twenty years or so?) preclude the need to double
> clutch (as many of you I'm sure have heard). For example:
>


<snip links>


> I did see some arguments (one?) about using double clutching to spare
> wear on the synchro. OTOH, the synchro might be something that lasts
> the life of a car. I didn't quite get resolution on this.


Synchros have changed relatively little since 1928, when they appeared for
the first time on a Cadillac. In operation, sychro components rub together
in an oil bath and drag the mainshaft and countershaft speeds so they match
each other before the dog teeth are allowed to mesh. Since synchros work by
abrasion, it stands to reason that they are a consumable; eventually they
will wear out no matter what.

Second gear is usually the first one to wear out. It gets the most use,
experiences the most rotational difference when used, so also experiences
the most frictional force.

When you double-clutch, you use the clutch to bring things into
synchronization (most of the way, anyway), and remove some of the
responsibility from the synchros. There *is* a tiny bit more wear on the
clutch when you do this, but is is a *tiny* bit. The mass being moved when
double-clutching is less than 0.1% of the mass of the car itself, so wear
is correspondingly less.

A clutch's greatest wear by far is experienced when starting up from a
standstill.


>
> At the moment I am under the impression that the really big wear item
> in, say, circa 1988-1995 Civics with manual transmissions (which seems
> to include my 91 Civic and possibly going back a few years more) may
> be the clutch release bearing. It wears with every depress-and-release
> of the clutch pedal. Also riding the clutch pedal between shifts or
> keeping it depressed at stops will wear it.


Release bearings wear from excessive use, not from normal use. Riding the
clutch, "blipping" at stop lights, and failure to maintain proper
adjustment is what does it.

Normal day-to-day up shifting and downshifting will not cause excessive
wear.


>
> I am still a little intrigued about the argument that 'the clutch is
> being used as a brake pad when one downshifts.'


Not quite: The clutch CAN be used as a brake pad, but that is the WRONG way
to downshift. The right way does not use the clutch as a brake pad, but
matches clutch and countershaft rotational speeds before the clutch is
reengaged, so the engine becomes the brake pad.





> Seems to me that
> engine inertia is being used as a brake pad,


See above.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

"jim beam" <nospam@example.net> wrote
> Caroline wrote:
> > "jim beam" <nospam@example.net> wrote
> >
> >>Abeness wrote:
> >>
> >>>TeGGer® wrote:
> >>>
> >>>>"Downshifting" without double-clutching is not smart. You are NOT
> >>>>supposed to use the clutch as a brake pad.
> >>>>
> >>>>Downshift properly and there is zero wear on the friction disc.
> >>>
> >>>
> >>>I've heard here that double-clutching means putting it in neutral
> >>>between shifts and letting the clutch out (i.e., releasing the pedal),
> >>>but wouldn't the point be to simply rev-match (approximately, after long
> >>>experience) before engaging at the lower gear, to reduce the wear on the
> >>>clutch?
> >>
> >>there's no real wear on the clutch from shifting, whether just relying
> >>on synchros or double clutching. clutch wear comes from drive-away from
> >>a standstill, holding it on the clutch on hills, "resting" a foot on the
> >>clutch pedal on the freeway, etc. if you don't peel away from lights,
> >>use the parking brake on hills & rest your foot on the floor, there's no
> >>reason a clutch won't last like tegger's is doing. also don't under
> >>rate a dealer's hunger for recommending unnecessary work.
> >
> >
> > Before I saw Jim's post and mention of the "synchro," I was torn about
> >
> > 1. wear on clutches from shifting
> > 2. the need to double-clutch
> >
> > Speaking as someone who's never "DIY replaced" a clutch, the "synchro"
piqued my
> > interest. The reports I am seeing say that modern synchros (about the last
> > twenty years or so?) preclude the need to double clutch (as many of you I'm
sure
> > have heard). For example:
>
> changing a clutch is a procedural pita because of access, but it's not
> technically hard. the cam belt is technically much more involved even
> though access is much easier.

I'm just figuring I'm going to need some kind of hoist to do it right. (Maybe
I'm wrong. I studied what you said before and the manual on this.) Not sure I'll
feel so inspired to go spend some serious bucks on something I think I will only
use once every say 15 years.

> > 1.
> > "In modern cars double-clutching is replaced by a synchronizer."
> > http://www.angelfire.com/hiphop3/ppd.../ManTrans.html
> >
> > 2.
> > "Manual transmissions in modern passenger cars use synchronizers to
eliminate
> > the need for double-clutching."
http://auto.howstuffworks.com/transmission6.htm
> >
> > 3.
> > "Today, all manual transmissions have 'synchros,' so double clutching is
> > completely unnecessary. And in fact, it DOES put extra wear and tear on the
> > clutch because you're using it twice for every shift instead of once."
> > http://www.cartalk.com/content/colum...cember/11.html
> >
> > 4.
> > " 'Synchronizers' in manual transmissions in modern passenger cars,
eliminate
> > the need for double-clutching."
http://www.automotiveforchicks.com/?page=tips
>
> hmm, automotiveforchicks propagating old lore about the 3000 mile oil
> change & changing transmission fluid "every 100,000 kms or 32,500 miles"
> has got to challenge their credibility.

Aside: They called this a rule of thumb. In closing on this, the site says:
"Bottom line: Maintain the practice of changing engine oil at recommended
intervals."

I'm not saying any of the above sites are perfect. I am saying there does seem
to be a consensus re synchros greatly improving clutch life and performance
(probably performance was the bigger motivation, as far as I can tell). That's
why someone thought of the synchro, right?

> > I did see some arguments (one?) about using double clutching to spare wear
on
> > the synchro. OTOH, the synchro might be something that lasts the life of a
car.
> > I didn't quite get resolution on this.
>
> generally, synchros do last the life of the car. some of the old types
> of synchro, notably some of the early porsche designs, were great for
> racing & fast forced shifts, but they wore quickly, particularly if
> there were problems with insufficient clutch disengagement [clutch plate
> not being sufficiently free to "float" on the drive pinion], then they'd
> check out pretty darned quick. the current cone clutch design of
> synchro just shrugs off bulk abuse.
>
> if you want a conclusive demo on the value of synchros/double-clutching,
> drive something like a cement truck.

My 1.5 liter, under two ton Civic is not a cement truck, so I see your point but
am not sure this would say anything terribly meaningful... Very different
engineering and needs being satisfied...

> > At the moment I am under the impression that the really big wear item in,
say,
> > circa 1988-1995 Civics with manual transmissions (which seems to include my
91
> > Civic and possibly going back a few years more) may be the clutch release
> > bearing. It wears with every depress-and-release of the clutch pedal. Also
> > riding the clutch pedal between shifts or keeping it depressed at stops will
> > wear it.
>
> the thrust bearing should last at least the life of the clutch. if a
> clutch is badly adjusted or the driver "rides" the clutch pedal all the
> time, it will wear more quickly, but i wouldn't worry about it. you've
> got this far, so i doubt your driving habits are bad.

Aside: I'd like to see more reports from others here who have had clutch parts
replaced.

> > I am still a little intrigued about the argument that 'the clutch is being
used
> > as a brake pad when one downshifts.' Seems to me that engine inertia is
being
> > used as a brake pad, and engines are iron horses that can take it for a
design
> > life of say 15 years and 250k miles plus..
>
> correct, it's the engine that does the braking, not the clutch.
>
> > For now, I suppose the real argument
> > against downshifting as a means of slowing the car down is that many, when
> > downshifting from 5th gear to 1st to neutral, will use the clutch say five
> > times. Compare this to shifting from 5th to neutal and using the disc/drum
> > brakes on the wheels; the clutch is used once. Downshifting translates to
using
> > the release bearing several times more each time the car comes to a stop.
>
> shifting down through the gears is not that big a deal. consider the
> principle of the relative loads; can you "chirp" the drive wheels
> downshifting? no? then there's not as much load as chirping on the
> up-shift.

What is the meaning of the (I suspect highly technical) term "chirp"?

> you don't "need" to go 5-4-3-2-1 by the way. 5-3-1 is perfectly ok.

Yes, I do this often. Just depends on the situation. I think over the years I
have come to operate by what has perhaps become fortuitous feel. In general, I
avoid letting the engine spike high or low in RPMS all of a sudden.

> braking in neutral is potentially very dangerous. not only are you in
> no position to apply power if required, you also have no engine braking.

Ha. Interesting point.

Plus, maybe here or somewhere else on the net I read recently it's illegal in
many areas to let the car coast (say to a stop) in neutral, for the reason you
give.

> again, going back to the cement truck, losing brakes on a fully loaded
> vehicle because they've overheated on a big descent is no joke. trust
> me on that. engine braking may not be "necessary" in all situations,
> but to get out of the habit is a big no-no.

I should toss in at this point that Tom 'n' Ray, despite their comments above,
say not to downshift to brake unless one is on a very steep hill. Then use the
engine to brake to keep the brake fluid from boiling (in the extreme), etc.

I'm not sure they're fully up-to-date, for one. Or there's a lot of variation
from one car make to another re how well clutch parts are designed.

> > And again, correct me if I'm wrong, but apart from downshifting, driving
style
> > will have an impact on clutch life as well. E.g. shifting very quickly.
>
> shifting fast has a positive effect on the clutch [if any] but negative
> on the synchros.

I'm not sure we mean the same thing when we say "shift fast."

"Fast shifting will place greater strain on synchronizers as will marginal
lubrication and the presence of dirt or particulate in the transmission fluid."
http://www3.bc.sympatico.ca/Volvo_Books/trans1.html

But like I said, this is just google stuff that is not all entirely in
agreement, and I haven't put my hands on the guts of the parts about which we're
talking. So I'm all eyes if people have more to say on this.

"TeGGer®" <teggeratistopdotcom@changetheobvious.invalid> wrote
> "Caroline" <caroline10027remove@earthlink.net> floridly penned
Ha! :-)
> > I did see some arguments (one?) about using double clutching to spare
> > wear on the synchro. OTOH, the synchro might be something that lasts
> > the life of a car. I didn't quite get resolution on this.
>
>
> Synchros have changed relatively little since 1928, when they appeared for
> the first time on a Cadillac.

Something's changed, else I wouldn't see so many reports of how better modern
clutches are. My take is double-clutching was strongly recommended before
something like 1985.

> In operation, sychro components rub together
> in an oil bath and drag the mainshaft and countershaft speeds so they match
> each other before the dog teeth are allowed to mesh. Since synchros work by
> abrasion, it stands to reason that they are a consumable; eventually they
> will wear out no matter what.

Depends on what you mean by "eventually." Before the engine needs a ring job?

snip
> > At the moment I am under the impression that the really big wear item
> > in, say, circa 1988-1995 Civics with manual transmissions (which seems
> > to include my 91 Civic and possibly going back a few years more) may
> > be the clutch release bearing. It wears with every depress-and-release
> > of the clutch pedal. Also riding the clutch pedal between shifts or
> > keeping it depressed at stops will wear it.
>
>
> Release bearings wear from excessive use, not from normal use.

Yes, it's used excessively, arguably, when downshifting.

> Riding the
> clutch, "blipping" at stop lights, and failure to maintain proper
> adjustment is what does it.

Though I saw some commentary on how practically all new cars have a clutch
self-adjusting feature that may obviate your point on adjustment...

> > I am still a little intrigued about the argument that 'the clutch is
> > being used as a brake pad when one downshifts.'
>
>
> Not quite: The clutch CAN be used as a brake pad, but that is the WRONG way
> to downshift.

Seems like you're talking about some totally crazed way of using (abusing) the
clutch that would fail the intuitive sense test as well as the common sense
test... Now I'm sure there are some young drivers who do this, but I suspect
there's a whole repertoire of other abuse that accompanies and even overshadows
this.

In any event, you clarified your original position. I suspect we're all
practically on the same page...

Caroline wrote:
> "jim beam" <nospam@example.net> wrote
>
>>Caroline wrote:
>>
>>>"jim beam" <nospam@example.net> wrote
>>>
>>>
>>>>Abeness wrote:
>>>>
>>>>
>>>>>TeGGer® wrote:
>>>>>
>>>>>
>>>>>>"Downshifting" without double-clutching is not smart. You are NOT
>>>>>>supposed to use the clutch as a brake pad.
>>>>>>
>>>>>>Downshift properly and there is zero wear on the friction disc.
>>>>>
>>>>>
>>>>>I've heard here that double-clutching means putting it in neutral
>>>>>between shifts and letting the clutch out (i.e., releasing the pedal),
>>>>>but wouldn't the point be to simply rev-match (approximately, after long
>>>>>experience) before engaging at the lower gear, to reduce the wear on the
>>>>>clutch?
>>>>
>>>>there's no real wear on the clutch from shifting, whether just relying
>>>>on synchros or double clutching. clutch wear comes from drive-away from
>>>>a standstill, holding it on the clutch on hills, "resting" a foot on the
>>>>clutch pedal on the freeway, etc. if you don't peel away from lights,
>>>>use the parking brake on hills & rest your foot on the floor, there's no
>>>>reason a clutch won't last like tegger's is doing. also don't under
>>>>rate a dealer's hunger for recommending unnecessary work.
>>>
>>>
>>>Before I saw Jim's post and mention of the "synchro," I was torn about
>>>
>>>1. wear on clutches from shifting
>>>2. the need to double-clutch
>>>
>>>Speaking as someone who's never "DIY replaced" a clutch, the "synchro"
>
> piqued my
>
>>>interest. The reports I am seeing say that modern synchros (about the last
>>>twenty years or so?) preclude the need to double clutch (as many of you I'm
>
> sure
>
>>>have heard). For example:
>>
>>changing a clutch is a procedural pita because of access, but it's not
>>technically hard. the cam belt is technically much more involved even
>>though access is much easier.
>
>
> I'm just figuring I'm going to need some kind of hoist to do it right. (Maybe
> I'm wrong. I studied what you said before and the manual on this.) Not sure I'll
> feel so inspired to go spend some serious bucks on something I think I will only
> use once every say 15 years.
>
>
>>>1.
>>>"In modern cars double-clutching is replaced by a synchronizer."
>>>http://www.angelfire.com/hiphop3/ppd.../ManTrans.html
>>>
>>>2.
>>>"Manual transmissions in modern passenger cars use synchronizers to
>
> eliminate
>
>>>the need for double-clutching."
>
> http://auto.howstuffworks.com/transmission6.htm
>
>>>3.
>>>"Today, all manual transmissions have 'synchros,' so double clutching is
>>>completely unnecessary. And in fact, it DOES put extra wear and tear on the
>>>clutch because you're using it twice for every shift instead of once."
>>>http://www.cartalk.com/content/colum...cember/11.html
>>>
>>>4.
>>>" 'Synchronizers' in manual transmissions in modern passenger cars,
>
> eliminate
>
>>>the need for double-clutching."
>
> http://www.automotiveforchicks.com/?page=tips
>
>>hmm, automotiveforchicks propagating old lore about the 3000 mile oil
>>change & changing transmission fluid "every 100,000 kms or 32,500 miles"
>>has got to challenge their credibility.
>
>
> Aside: They called this a rule of thumb. In closing on this, the site says:
> "Bottom line: Maintain the practice of changing engine oil at recommended
> intervals."
>
> I'm not saying any of the above sites are perfect. I am saying there does seem
> to be a consensus re synchros greatly improving clutch life and performance
> (probably performance was the bigger motivation, as far as I can tell). That's
> why someone thought of the synchro, right?
>
>
>>>I did see some arguments (one?) about using double clutching to spare wear
>
> on
>
>>>the synchro. OTOH, the synchro might be something that lasts the life of a
>
> car.
>
>>>I didn't quite get resolution on this.
>>
>>generally, synchros do last the life of the car. some of the old types
>>of synchro, notably some of the early porsche designs, were great for
>>racing & fast forced shifts, but they wore quickly, particularly if
>>there were problems with insufficient clutch disengagement [clutch plate
>>not being sufficiently free to "float" on the drive pinion], then they'd
>>check out pretty darned quick. the current cone clutch design of
>>synchro just shrugs off bulk abuse.
>>
>>if you want a conclusive demo on the value of synchros/double-clutching,
>>drive something like a cement truck.
>
>
> My 1.5 liter, under two ton Civic is not a cement truck, so I see your point but
> am not sure this would say anything terribly meaningful... Very different
> engineering and needs being satisfied...

but caroline, you're an engineer. example of extreme is meant to
illustrate the principle. braking in neutral is pretty generally
inconsequential in a car, but very very dangerous in a truck. the value
of synchros in a car, especially to a driver that may never have tried
anything without them, is, imo, not appreciated until a different kind
of vehicle is experienced. a big truck, where synchros merely assist,
not override the gear change procedure, is easier/better experience to
get than finding some old stick-shifting banger with straight cut gears.

>
>
>>>At the moment I am under the impression that the really big wear item in,
>
> say,
>
>>>circa 1988-1995 Civics with manual transmissions (which seems to include my
>
> 91
>
>>>Civic and possibly going back a few years more) may be the clutch release
>>>bearing. It wears with every depress-and-release of the clutch pedal. Also
>>>riding the clutch pedal between shifts or keeping it depressed at stops will
>>>wear it.
>>
>>the thrust bearing should last at least the life of the clutch. if a
>>clutch is badly adjusted or the driver "rides" the clutch pedal all the
>>time, it will wear more quickly, but i wouldn't worry about it. you've
>>got this far, so i doubt your driving habits are bad.
>
>
> Aside: I'd like to see more reports from others here who have had clutch parts
> replaced.

most shops just replace everything - clutch, pressure plate, thrust
bearing, pilot bearing, and often skim the flywheel too. personally,
i'm happy just replacing the clutch plate if everything else is ok. if
the flywheel is skimmed, the bolt mounting surface needs to be skimmed
also to maintain the same degree if differential with the friction
surface that it had when new. frequently, that's not done so people
wonder why the clutch goes again so soon again after... insufficient
pressure can be brought by the pressure plate.

>
>
>>>I am still a little intrigued about the argument that 'the clutch is being
>
> used
>
>>>as a brake pad when one downshifts.' Seems to me that engine inertia is
>
> being
>
>>>used as a brake pad, and engines are iron horses that can take it for a
>
> design
>
>>>life of say 15 years and 250k miles plus..
>>
>>correct, it's the engine that does the braking, not the clutch.
>>
>>
>>>For now, I suppose the real argument
>>>against downshifting as a means of slowing the car down is that many, when
>>>downshifting from 5th gear to 1st to neutral, will use the clutch say five
>>>times. Compare this to shifting from 5th to neutal and using the disc/drum
>>>brakes on the wheels; the clutch is used once. Downshifting translates to
>
> using
>
>>>the release bearing several times more each time the car comes to a stop.
>>
>>shifting down through the gears is not that big a deal. consider the
>>principle of the relative loads; can you "chirp" the drive wheels
>>downshifting? no? then there's not as much load as chirping on the
>>up-shift.
>
>
> What is the meaning of the (I suspect highly technical) term "chirp"?

on the change up from 1-2, [& 2-3 if you have a powerful motor], floor
the gas, then slam the clutch into the gear. it'll "chirp" the wheels
as they spin momentarily with the engine's momentum. it's an immaturity
thing.

>
>
>>you don't "need" to go 5-4-3-2-1 by the way. 5-3-1 is perfectly ok.
>
>
> Yes, I do this often. Just depends on the situation. I think over the years I
> have come to operate by what has perhaps become fortuitous feel. In general, I
> avoid letting the engine spike high or low in RPMS all of a sudden.
>
>
>>braking in neutral is potentially very dangerous. not only are you in
>>no position to apply power if required, you also have no engine braking.
>
>
> Ha. Interesting point.
>
> Plus, maybe here or somewhere else on the net I read recently it's illegal in
> many areas to let the car coast (say to a stop) in neutral, for the reason you
> give.
>
>
>> again, going back to the cement truck, losing brakes on a fully loaded
>>vehicle because they've overheated on a big descent is no joke. trust
>>me on that. engine braking may not be "necessary" in all situations,
>>but to get out of the habit is a big no-no.
>
>
> I should toss in at this point that Tom 'n' Ray, despite their comments above,
> say not to downshift to brake unless one is on a very steep hill. Then use the
> engine to brake to keep the brake fluid from boiling (in the extreme), etc.
>
> I'm not sure they're fully up-to-date, for one. Or there's a lot of variation
> from one car make to another re how well clutch parts are designed.

you can get away with all kinds of bad behavior in modern cars. the
reason i gave the cement truck analogy is because heavy equipment like
this is not abuse tolerant. riding the clutch, bad shifting, no engine
braking - all get you stuck at the side of a road with a rapidly
hardening cargo in no time at all. repairing the vehicle is one thing.
crawling inside the hopper with an air hammer to remove all that
concrete is something else.

>
>
>>>And again, correct me if I'm wrong, but apart from downshifting, driving
>
> style
>
>>>will have an impact on clutch life as well. E.g. shifting very quickly.
>>
>>shifting fast has a positive effect on the clutch [if any] but negative
>>on the synchros.
>
>
> I'm not sure we mean the same thing when we say "shift fast."
>
> "Fast shifting will place greater strain on synchronizers as will marginal
> lubrication and the presence of dirt or particulate in the transmission fluid."
> http://www3.bc.sympatico.ca/Volvo_Books/trans1.html

yes, but modern synchros won't let you abuse them, unlike some of the
older designs. you /can't/ shift until it's synched. the old porsche
design [had kind of a baulk ring that ran directly against the dog] was
great if you really needed to shift asap because you could just force
it, but was just not abuse/bad driver tolerant.

>
> But like I said, this is just google stuff that is not all entirely in
> agreement, and I haven't put my hands on the guts of the parts about which we're
> talking. So I'm all eyes if people have more to say on this.
>

hopefully your car maint class will allow you to get your hands on the
workings of a gearbox. alternatively, visit a junk yard some time -
great places to learn.

"Caroline" <caroline10027remove@earthlink.net> floridly penned in
news:JOKqd.3811$6K5.3644@newsread2.news.atl.earthl ink.net:

> "TeGGer®" <teggeratistopdotcom@changetheobvious.invalid> wrote
>> "Caroline" <caroline10027remove@earthlink.net> floridly penned


>>
>> Synchros have changed relatively little since 1928, when they
>> appeared for the first time on a Cadillac.
>
> Something's changed, else I wouldn't see so many reports of how better
> modern clutches are. My take is double-clutching was strongly
> recommended before something like 1985.


Synchros were always meant to be used, and always meant to be used without
double-clutching. Their very reason for existence was to eliminate the need
for double-clutching. Earl Thompson sold the idea to Cadillac in 1924 on
that very point.

Also, keep in mind that almost everything on or in a car lasts far longer
now than it used to. Synchros in a 1955 Pontiac might have lasted less than
100K, but the engine didn't last much past 100K before needing a rebuild.

Synchros in a modern Civic may last over 250K, but then so does the engine.


<snip>


>> > At the moment I am under the impression that the really big wear
>> > item in, say, circa 1988-1995 Civics with manual transmissions
>> > (which seems to include my 91 Civic and possibly going back a few
>> > years more) may be the clutch release bearing. It wears with every
>> > depress-and-release of the clutch pedal. Also riding the clutch
>> > pedal between shifts or keeping it depressed at stops will wear it.
>>
>>
>> Release bearings wear from excessive use, not from normal use.
>
> Yes, it's used excessively, arguably, when downshifting.


Not at all; you're not on it long enough. Riding the pedal and incorrect
adjustment means the bearing is constantly loaded, several hundred
(thousand?) percent more load-time than if properly used. That's abuse.


<snip>


>> Not quite: The clutch CAN be used as a brake pad, but that is the
>> WRONG way to downshift.
>
> Seems like you're talking about some totally crazed way of using
> (abusing) the clutch that would fail the intuitive sense test as well
> as the common sense test...


Like the old saying goes, common sense isn't too common.

People will move the lever down to the next gear, then simply let the
clutch out, letting the car drag the engine up to speed. Very common. This
guy that wore his clutches out in 90K did that.



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

"jim beam" <nospam@example.net> wrote
snip
> >>if you want a conclusive demo on the value of synchros/double-clutching,
> >>drive something like a cement truck.
> >
> >
> > My 1.5 liter, under two ton Civic is not a cement truck, so I see your point
but
> > am not sure this would say anything terribly meaningful... Very different
> > engineering and needs being satisfied...
>
> but caroline, you're an engineer. example of extreme is meant to
> illustrate the principle.

I agree it illustrates a principle. But, techies that both you and I are, I
trust you agree that practically speaking not double clutching on a 91 Civic may
have negligible effect on it compared to the life of its other parts.

Not so for the cement truck, it would seem.

> braking in neutral is pretty generally
> inconsequential in a car, but very very dangerous in a truck. the value
> of synchros in a car, especially to a driver that may never have tried
> anything without them, is, imo, not appreciated until a different kind
> of vehicle is experienced. a big truck, where synchros merely assist,
> not override the gear change procedure, is easier/better experience to
> get than finding some old stick-shifting banger with straight cut gears.

Okay. I appreciate the "art of the synchro" here. Seriously!

> > Aside: I'd like to see more reports from others here who have had clutch
parts
> > replaced.
>
> most shops just replace everything - clutch, pressure plate, thrust
> bearing, pilot bearing, and often skim the flywheel too.

Ya but when, and how come someone else with a 91 Civic may have been through a
clutch after only 100k miles?

We've certainly touched on this. Looking for still more empirical data. I did
google the archives a bit and it seems it does happen to Hondas of this vintage.

> personally,
> i'm happy just replacing the clutch plate if everything else is ok. if
> the flywheel is skimmed, the bolt mounting surface needs to be skimmed
> also to maintain the same degree if differential with the friction
> surface that it had when new. frequently, that's not done so people
> wonder why the clutch goes again so soon again after... insufficient
> pressure can be brought by the pressure plate.

I gotta do this sometime... I don't want to hit age 70 without having taken
apart a clutch and having put it back together... :-)

> > I should toss in at this point that Tom 'n' Ray, despite their comments
above,
> > say not to downshift to brake unless one is on a very steep hill. Then use
the
> > engine to brake to keep the brake fluid from boiling (in the extreme), etc.
> >
> > I'm not sure they're fully up-to-date, for one. Or there's a lot of
variation
> > from one car make to another re how well clutch parts are designed.
>
> you can get away with all kinds of bad behavior in modern cars. the
> reason i gave the cement truck analogy is because heavy equipment like
> this is not abuse tolerant. riding the clutch, bad shifting, no engine
> braking - all get you stuck at the side of a road with a rapidly
> hardening cargo in no time at all. repairing the vehicle is one thing.
> crawling inside the hopper with an air hammer to remove all that
> concrete is something else.

Okay.

> > I'm not sure we mean the same thing when we say "shift fast."
> >
> > "Fast shifting will place greater strain on synchronizers as will marginal
> > lubrication and the presence of dirt or particulate in the transmission
fluid."
> > http://www3.bc.sympatico.ca/Volvo_Books/trans1.html
>
> yes, but modern synchros won't let you abuse them, unlike some of the
> older designs. you /can't/ shift until it's synched. the old porsche
> design [had kind of a baulk ring that ran directly against the dog] was
> great if you really needed to shift asap because you could just force
> it, but was just not abuse/bad driver tolerant.

Okay.

> > But like I said, this is just google stuff that is not all entirely in
> > agreement, and I haven't put my hands on the guts of the parts about which
we're
> > talking. So I'm all eyes if people have more to say on this.
> >
>
> hopefully your car maint class will allow you to get your hands on the
> workings of a gearbox.

Yes, I was going to take the manual transmission course but stuff happened.

> alternatively, visit a junk yard some time -
> great places to learn.

Yes, I was thinking of seeing what I could pick up for five bucks at my favorite
import junkyard...