How you downshift matters...I don't know about how BAD it could be put popping the shifter in a gear lower and dropping the clutch isn't making your car happy, thats for sure

Look into the so called "heel-toe" downshifting, its what all the cool racer guys do, and it'll allow you to gently downshift...


CCC

 

...its what all the cool racer guys do, and it'll allow you to gently downshift...

CCC

In everyday driving, there's not really much call for downshifting, but we just about all do it anyway. If you are gonna downshift, there's no reason *not* to rev match.

As for driving on a road course -- it's a basic skill that you *must* learn to progress as a driver. Your car will TELL you that you need to rev match. I'm just getting the hang of heel-toe (more like ball off foot/side of foot); I don't think coolness has much to do with it. It's definitely a benefit for your engine, clutch, and transmission to rev match when down shifting. If you have ever chirped your tires in a threshhold braking/downshift situation--you've gotta know that the car is not liking it much.

 

when i downshift i do it like if i was shifting normal you don't feel it i don't let the rpm go over 4 i think it better the being in 5th taking it out of gear slowing down the going to 2nd. if you go one gear lower and slowly let out the clutch u slow down with out hitting the brake.

 

I read in a magazine where downshifting in traffic is bad for the clutch and throw out bearing. Not sure if that is really true

The article just said to use the brakes instead of downshifting

 

The act of going to the next lower gear is not the problem. The problem is using the clutch to slow your car down. If you are slipping the clutch, you are wearing out your clutch. Same with taking off. The less you slip the clutch the better for it.
Of course, on the opposite end of the spectrum you have popping the clutch which is really rough on the rest of the drivetrain. You need to use the quickest slip needed to make it smooth.
When downshifting the best way to have the quickest clutch slip is to rev-match. As you're downshifting, blip the throttle to bring the RPMs up a bit. Then slip it into gear and let out the clutch. The engine will provide some drag to slow you down, but that really is the brakes job.

Slip your clutch less and it will thank you by providing many more miles of service.

 

So what is cheaper brake pads or a clutch?

 

Pads

 

clutches are for changing gears - brakes are for stopping the car. You downshift to slow the car and the energy goes out the clutch in the form of premature wear. This was highlighted in a recent Sport and Compact Car mag.

Brakes are cheaper than clutches by far.

 

So I guess the article I read was write you should use the brakes to slow the car down instead of using the clutch. It makes sense. Not to mention brake pads are a lot cheaper then clutch parts.

 

Yeah, typically when I DS, I rev match to prevent any damage and the sudden jerk of my passenger's head

. It's always a real smooth transition doing it this way. I try to do it to keep the brakes from wearing down so quickly. Of course autoXing doesn't really help my brakes out, but that's another story.

 

thats why i d/s its much smoother. it not like i down shift and the car jerks i'll bring and down a gear then match the rpm with the gear then start letting out the clutch with out the gas. but now that i know thats its not good i'll stop.

 

Yeah, typically when I DS, I rev match to prevent any damage and the sudden jerk of my passenger's head

. It's always a real smooth transition doing it this way. I try to do it to keep the brakes from wearing down so quickly. Of course autoXing doesn't really help my brakes out, but that's another story.

So you think replacing a clutch is cheaper then replacing brake pads?

 

Downshifting doesn't wear the clutch at all if you rev match and don't slip. Let the clutch ALL THE WAY OUT and the engine slows you down, not the clutch. Downshifting does, however, wear out your syncros if you don't double clutch with a throttle blip (heal-toe technique does this while braking). This keeps the syncros spinning with the output shaft.

 

Every time you disengage and/or engage the clutch it causes wear. There is no getting around it. It is the whole reason a clutch works, friction.

No matter how close you think you match RPM's when the clutch friction material comes in contact with the flywheel there is also slippage.

BTW heal and toe down shifting is not double clutching. And there is no reason to double clutch a transmission with syncros.

 

If you are that concerned about friction wear on your clutch, I guess you always start off very slow and never accelerate faster than 0-60 in 4 minutes. Downshifting while matching revs does way less to wear the clutch than starting from a stand still, even if your driving like a granny.

I didn't say heel-toe was double clutching, I said that's how you double clutch with trhottle blip while braking.

And there definitely IS a reason to double clutch a tranny with syncros - double clutching with a throttle blip on downshift is what SAVES your syncros - that's why you do it.

 

I never said I was concerned about clutch wear. I already have the money for a new clutch put aside for when it goes. But, I drive my focus at a fair amount of HPDE, and autocross'.

Why are you speaking so redundantly. Double clutching includes a throttle blip. There is no other way to double clutch. If you do it a different way then you are not double clutching. And, the reason for double clutching is for transmissions with out syncros so it will go in gear.

For daily driving downshifting to slow down is just plain stupid. So is double clutching. You are not perfect (no one is) so again any down shift with or without a double clutch or throttle blip will not match 100%. So you will be doing additional wear to the clutch and syncros. The granny comment is completely inappropriate. If you dive you have to accelerate by using the clutch. You do not have to use the clutch to slow down.

Look in summary:
If you want to keep your car expenses to a minimum use the brakes to stop. Save the heel and toe downshifts for the track or spirited back road adventures. Just be willing to accept the extra clutch wear when you do so. And for god sake don't be a ricer and downshift from 6th to 5th to 4th to 3th to 2nd to 1st when coming up to a red light.

 

I'm not being redundant, I want to be clear. Yes, double clutching includes a throttle blip, and typically you are braking at the same time, which is why I mentioned heel-toe. If I save the heel-toe braking/downshifting only for the track, I would be lousy at it. I practice on the street whenever I can.

And I somewhat agree that downshifting JUST to slow down to a stop is kind of silly - if the light turns red, use the brakes. But downshifting to slow down knowing you might need that gear (not stopping) is not silly, whether driving on the street or road racing.

And yes double clutching is a requirement for trannys without synchros - but for the very same reason it SAVES synchro wear on trannys that have synchros. A clutch disk is cheap compared to replacing synchros. Downshifting with a double-clutch/blip does not wear the synchros.

I still maintain that given what I have said above, you will never notice any additional clutch wear from downshifting (correctly); what mostly wears the clutch is starting from a stop. Chirping the tires on downshift, yes, that is dumb and will wear everything. Otherwise, one hard start off the line will use up more clutch disk than years of downshifting correctly.

 

Supersonic - "Downshifting doesn't wear the clutch at all if you rev match and don't slip."

You don't really understand how a clutch works, do you?

You are giving bad and wrong advice.

 

Supersonic - "Downshifting doesn't wear the clutch at all if you rev match and don't slip."

You don't really understand how a clutch works, do you?

You are giving bad and wrong advice.

So then explain how a clutch works. If the engine rpm is matched to the rpm of the clutch, then there is no slippage as the clutch mates up to the flywheel. Without slippage, how does the clutch wear?

Perhaps you're the one that doesn't really understand how a clutch works.

The following is from http://auto.howstuffworks.com/clutch.htm

"The clutch only wears while the clutch disc and the flywheel are spinning at different speeds. When they are locked together, the friction material is held tightly against the flywheel, and they spin in sync. It is only when the clutch disc is slipping against the flywheel that wearing occurs. So if you are the type of driver who slips the clutch a lot, you will wear out your clutch a lot faster."

 

Can anybody rev match exactly to the 1 RPM? NO.
That means the clutch will slip some to make up the 20, 50, 100, 500 rpm that you are off.
If someone here can blip their throttle precisely enough so that there is no clutch slippage, then I bow down.

Does rev matching help reduce clutch wear compared to using the clutch to bring the engine up? Yes.
However, I stand with Primaris on this. In everyday driving situations downshifting just to use the engine to slow you down is pointless and a waste of clutch.

Save the aggressive downshifting for the track where it makes sense to apply the proper heel-toe rev matching shifts.
Note: Even here, you still are not using the engine to slow you down, the downshift is to supply more power to the wheels for forward acceleration.

 

Agreed. There's a little clutch wear on each downshift, but I bet a good driver lets the clutch slip no more than a single revolution. As long as it is reved close enough, I just dump the clutch. The 2-piece fly (sprung clutch on other cars) absorbs the slight difference and there is virtually no slippage. I agree that it's usually pointless to use downshifting to slow the car. It should only be used to select the proper gear.

 

I don't quite agree - dumping the clutch will wear the surface also. It's physics - the work of the engine has to be transfered thru the clutch, whether you take 50 milliseconds to clutch or 1000 milliseconds. It is possible that dumping the clutch could do more damage to the disk than slipping. I suppose there is some "ideal" timing and pressure plate force for minimum wear, but who knows what it is and we couldn't do it anyway.

 

Save the aggressive downshifting for the track where it makes sense to apply the proper heel-toe rev matching shifts.
Note: Even here, you still are not using the engine to slow you down, the downshift is to supply more power to the wheels for forward acceleration.

Actually it's so you don't upset the balance of the car.

 

Mike-SVT - maybe you misunderstand my posts, or maybe you don't understand how a clutch works. My last street/track car had 133,000 miles on the original factory clutch (no slipping) when I sold it. I've never gone less than 100k miles on a clutch, even including autox, and EVEN DOWNSHIFTING!!!!. I have been a mechanical engineer for 21 years, and considering my age, I'd would also be willing to bet that I have spent a lot more time using clutches than the average ricer.

Clarification:"downshifting" - some folks think downshifting includes snapping the clutch after grabbing a lower gear. That's pretty dumb. But properly downshifting means negligible clutch wear compared to other clutch events unless you're "aggressively" downshifting, which I don't ever see a need for (street or track). On the track, using the engine to slow you down makes sense to save/cool your brakes or to set up for a turn. On the street, downshifting to use the engine to slow you down also makes sense sometimes - especially in traffic and especially to grab some torque. It also makes sense to practice downshifting on the street to be good on the track.

Synchro's - you don't even have to release the clutch to wear the synchros - you wear them whenever you shift to a lower gear while you are rolling. They wear much less if you keep the shafts spinning at roughly the same speed in the tranny, so that is why you double clutch/blip - to get it into a lower gear without as much wear on the synchro's (even if you don't let the clutch back out after you have downshifted!)

 

I don't quite agree - dumping the clutch will wear the surface also. It's physics - the work of the engine has to be transfered thru the clutch, whether you take 50 milliseconds to clutch or 1000 milliseconds.

Hey supersonicsvt, I'm on your side. j/k

Actually, I think there's a difference. If the revs are matched closely and you dump the clutch, a significant portion of the energy will be absorbed in the spring/damper of the flywheel. If you slowly let out the clutch, virtually all of it will be transfered to the clutch as heat, which is the primary cause of wear. Quickly engaging the clutch when revs are close won't hurt anything because the dual mass flywheel or sprung clutch is designed to absorb the energy. But what do I know, I'm an electrical engineer.