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Old 11-27-2009, 01:16 PM   #32 (permalink)
Mergnthwirker
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Join Date: Jun 2009
Location: Connecticut USA
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Drives: '09 370Z PW MT6 S
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Quote:
Originally Posted by Slynky View Post
This seems as good a place as any to ask since it's been mentioned in here so...

Wheel/tire size differences: Means you don't rotate tires and, what, you just replace the front ones more often than the rear?

And, heel/toe rev-matching. That refers to having your foot on the brake/gas at the same tiime, but seriously, unless you're "racing" for some kind of reason, wouldn't you just leave the brake alone when downshifting and just "feather" the gas most of the time (assuming you were in a car with no SRM)?

Wheels/tires: No, you can't rotate the tires. I suppose you could unmount the rears and swap them right-for-left, and unmount the front tires from the rim and do the same thing. But conventional wisdom has it that once the tires have been rotating in one direction, it is unwise to switch them to rotating in the other direction b/c the belts take a "set" and switching can upset the plies. So No. And BTW, you are much more likely to wear out the rear tires before the front, so you will likely end up replacing them in pairs (if you keep the same brand). Otherwise if you replace all 4, you end up throwing away two tires with life still in 'em.

Heel/toe: without the synchro-rev, when you are braking for a corner with your toe on the brake, at the same time --while you are braking--you can rotate your heel to the accelerator pedal to "blip" the throttle to match the revs to the speed of the drivetrain in the lower gear that you will need when exiting the corner at a lower speed.

At Bondurant's high-performance driving school, they taught us to ease off on the brake and "trail brake" to keep the car down on its suspension in the corner, which helps rotate the car in the corner. Then ease up on the brake in last part of the corner, and smoothly accelerate as the weight shifts towards the rear so you can maximize traction throughout the turn. Tires have a limit to their traction, so you want to use them to their best advantage based on where you are in the turn. Heel-and-toe braking lets you do this by controlling both the braking and the application of the throttle at the same time.

The rev-matching feature is extremely nice b/c it always gets the right engine speed based on the speed the drivetrain is rotating, so there are never any jerks to upset the chassis balance in the middle of the corner. I spent a lot of time learning how to heel/toe, so I avoided using the synchro-rev for the first couple of months I owned my Z. But I found when I took it autocrossing that my times were actually better when I let the system rev match and I focused instead on hitting my braking points and steering the best line. Maybe if I were a better driver, I would not have discovered this... But on a 3:35 course, I was more than 5-10 seconds faster with the system on.

YMMV
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