Double Clutching

[Terry Stapley]

What is the purpose of double clutching while on the track?

I have double clutched while driving a big rig but wonder what double clutching a cobra is used for on the track!!

[Three Peaks]

Terry,

Double clutching, or heel-and-toe is done to keep from upsetting the balance of the car while entering a corner under speed. Anything that can help the driver keep the car smooth in the corners is going to help lap times.

Bob

PS- When you coming back up for Beaches Cruise In?

[rdorman]

Double cluthing is used for non synchronized boxes and used to match the rotational speed of the input shaft to the gear you are selecting. No point on a synchronized box. Heal/toe is a different story, definiately needed for the track. Actually what is needed is to match the engine rpm/box/rear/tires as one in order to, like what was said, not 'upset' the car.

[Excaliber]

Double clutching can be used on the track to save your transmission from damage/abuse, but it WILL cost you lap time.

At Hawaii Raceway Park there is a hair pin at the end of the straight. Your coming down from a 100 plus and high gear to 1st gear. I don't downshift through the gears (into 3rd then into 2nd). I brake HARD and when making my 4th to 1st gear shift I would on occasion double clutch to 'save the synchromesh'. After all, lap after lap shifting so many times your really putting a LOT of wear on your trans. If I wasn't in hot pursuit, I'd rather give up a little time in favor of racing again someday AND getting my trans home in one piece!

I know many of the older 'sports cars' I had over the years had VERY weak 1st gear synchros, shifting them hard into 1st could ruin a synchro pretty darn quick! I always double clutched my Austin Healey, 1st gear synchro was all ready gone when I bought the car. Triumph's were also notorious for loosing the 1st gear synchro (this from personal experience). I learned to drive in a VW with non synchro 1st, so it comes kind of natural to me anyway.

Double clutch, save the synchros!

[01yelrt]

Double clutching will help even with a syncro trans. The effect of rotating everything before shifting will place less stress on the syncros and make the car go into gear with far less effort. Your syncros will last longer. The shift can be made sooner, really- "too early" if you aren't careful. You want to wait till the braking is mostly completed before shifting gears while heal toe downshifting, it is safer and easier on the car. If you double clutch you can get the gear lever to move easier at speeds that the syncros wont like to accomodate, this is not really good technique. Try this take the car up to a good relatively high speed in 3rd gear then get off the gas and put the clutch in, now at a speed that is very fast for 2nd gear just pull the shift lever gently against 2nd gear position without sliding it all the way into 2nd. (DO NOT LET THE CLUTCH OUT YOU WILL SPIN OUT OF CONTROL!!!) That high pitched whine you hear is the syncros trying to catch up to the wheel speed. They whine 'cause they're not happy. Also feel that you can pull pretty hard on the lever without the car going down into 2nd gear. Now repeat the sequence accelerating thru 3rd, apply the clutch , rev the engine to slightly higher than what will match the RPM you should be traveling in 2nd with the clutch out and the car in neutral then reapply the clutch and move the lever into Second you'll find the syncros are matched by engine revs and that the lever moves into second MUCH easier. Be careful again not to let the clutch out at high speed with the car in too low of a gear you'll lock the rear wheels relative to the car speed and spinout!

[CHANMADD]

The whole thing with racing is "smoothness",the smoother you are the faster you are.If you downshift without getting the motor up to speed you will upset the balance of the car and spinout ,like 01yelrt said.With modern synchro trannies you can shift from 5th to 1st as long as everything is rotating at the same speed.Also I have found in my car I can increase my braking effect by using the motor as well as the brakes, which in turn also helps to save the brakes which we all know on Cobras get pretty hot!You should be in the correct gear for the corner before the apex so that at the apex you can get back on the gas.

[Excaliber]

The debate about using downshifting in conjunction with the brakes or brakes alone has continued since racing began! There is sound principal to be found on both sides of the issue.

For myself, having tried both ways in numerous cars, I prefer brakes alone for maximum slowing/stopping effect. I like to focus on brake modulation, braking right to the point of 'lock-up' without going over that point. Extremely difficult to do while heel/toe application is also happening. Braking alone is of course the quickest way to over heat your brakes, but I believe it is also the quickest way around the track. I use heel/toe only to get into the final selected gear at the last critical mili second. I may downshift through the gears while braking and even double clutch when I'm taking it easy to preserve the car.

Heal/Toe is primarily a way to rev the engine WHILE braking to keep 'soften' the impact of letting the clutch out in a lower gear. The engine wants to 'rev up' to match the new trans gear ratio to the speed of the tires, so rev the engine and THEN let off the gas just as the clutch re-engages while still braking hard. MUCH easier said than done! Heel/toe can also be used effectivly to double clutch, when done RIGHT it has the same impact as heel/toe alone, softens the impact of clutch re-engagement.

Once when my brakes FADED to the point of GONE, I slammed it into 2nd gear going WAY to fast to 'lockup' the rear as a method of braking. The rear end came around, threatening a spin, which I was ready for. I went into the corner sideways and came out looking like a 'pro' (but needing a change of underwear and worried about damaged 'parts' on the car)! Calculated risk, I figured it was better to break something than hit the wall.

In fact here is a picture of the corner and the car (taken on a different day). Note the extreme angle of the front wheels, I was 'drifting' that day on purpose.