overal does it actually harm the clutch but save the tranny? Ive been pondering this lately.

 

It's purpose is to save the clutch and tranny by matching the RPM of the engine and tranny, thereby reducing the load on both during the downshift.

 

Actually the purpose is to eliminate sudden transitions of weight when entering a corner. You're already transfering weight forward by braking, so downshifting without matching the revs can easily bring the back end around in a racing situation.

 

Actually...........it is to allow the driver to both brake and downshift at the same time w/o upsetting the balance of the car before getting to the corner.. Allowing the car to be in the proper gear for the corner.

 

Actually, I'd simplify it even more... The purpose of heel-toe shifting is to smoothly move from one gear to a lower gear while simultaneously braking.

Apply that statement to racing, and it means that you don't upset the balance of the car (from the 'smoothly', above) as you are preparing for or entering a turn so the available friction from the tires is available for other purposes like turning the car, accelerating or braking. The 'downshift' puts you in the proper gear as you exit the turn and the 'simuntaneously braking' gets you to the proper speed to enter/handle the turn.

Apply that statement to the mechanicals of the car and it means that you are putting less stress on the clutch and tranny than a simple downshift. It makes sense that your components should last longer with smoother transitions. By rev matching, you should be saving the clutch by having the transmission and engine spinning at similar speeds. One might even make the argument that there would be no clutch plate wear if the engine and tranny speeds were perfectly matched when the clutch was engaged, but the odds of that are slim to none.

You might also be dragging into this the concept of engine braking (using the engine to slow the car, not the brakes). My ideas on this have changed slightly, lately, thanks to a few good threads from a month or so ago. I like to know how to engine brake and will let the engine do so if I need to slow down and I am already in the right gear. If I would need to downshift to engine brake, I just clutch-in and use the brakes to slow the car... that's what they are for (and it's cheaper to replaces the brakes than the clutch ). I like to know how to downshift to engine brake and it's useful for some situations (slippery roads, steep downhill grades), but the whole point of heel-toe is to slow the car w/ the brakes and have the transmission ready to 'go, go, go!' when you exit the turn.

 

I understand the heeltoe and why you do it, it jus seems like it would be bad on the clutch in the long run.

 

Are you sure you understand what it is? Hell and toe is the technique of braking and blipping the throttle with the same foot while downshifting. Why would that be hard on the clutch? Matching revs between downshifts actually minimizes wear to the clutch.

 

yes I understand how it works, and I can feel it as well. and its obvious its easier on the tranny with no harsh downshifts as well. but im talking about on track at a high rpm. But thats all I needed to know is that its not. thanks for the info

 

No problem!

 

I'm Taking it ya'll haven't driven a car with out syncro's

 

That would make an excellent topic for discussion -

 

well actually heeltoe and double clutching I learned when I was small on tractors.

 

Odds are, then, justintime HAS spent some time in VEHICLES without synchros... the handling isn't very good, but the torque and ground clearance rocks!

As long as you select the proper gear (no amount of rev-matching is going to help you downshifting into first at 90 MPH) for your next gear, rev matching is all about minimizing the wear on the clutch. If the engine is spinning at the same speed as the transmission, the clutch plate should not see any wear at all as there will be no slipping.

Track time is by its' nature harder on the engine, clutch and transmission, but the rev-matching of heel-toe is good for all of the components (and good for your lap times).

 

top end was never good either, but I could almost go over anything

 

I raced my GT-5 mini for 10 years, about 60 race weekends, and never had to change the clutch disc. I wore out syncros, before I went to a dog box, but never had a clutch problem. I always used a heel & toe technique on downshifts, and always at high rpm's. I talked to a new mini racer at the daytona national in may who lost a clutch in just several weekends, apparently from not using a heel & toe on downshifts. In my new race Mini I have and will contiue to heel & toe on downshifts and save my clutch..

 

I learned this on the first car I drove regularly, my mother's Fiat 500 which had an entirely unsychronized 4-speed gearbox. You either learned to double clutch and rev match or you just stuffed it in and ignored the graunching noises. I chose to follow Plan A (unlike the rest of the family...). Fortunately with just 500 cc and a pavement-ripping 22 hp you weren't likely to break anything either way.

The cool thing is that once you get used to the technique on an unsynchronized gearbox you can change gear, up or down, without using the clutch.

Many years later I did a Skip Barber 3-Day Racing School in a Formula Ford, also with a non-synchro gearbox. A couple of decades of double-clutch and heel/toe shifting really came in useful.

Neil
05 MCS
96 M3

 

I use to shift without the clutch on my old jeep. I wouldn't do that on the MC

DAVE thats what I wanted to hear. just curious what kinda mini??

 

like was just typed....IT SAVES THE CLUTCH!!!!!

 

The first race mini is a 71 shell, semi tube frame, 1310 cc full race engine, it uses weber carb, electromotive crank fire ignition,13.5 to 1 compression SC/CR dog box, goodyear slicks. The new race mini is my 2006 Mini Cooper S SSC racer

 

im liking it =]