Z-man

Using the motor to slow down? Um - like Racer pointed out - maybe on cars from the 50's and 60's, but it really isn't a good idea to use the tranny to help you slow down. Last I checked - rotors and pads are cheaper than tranny rebuilds. That applies even in panic / over cooking situations. If I overcook a corner, I can always carry the braking into the corner via trailbraking. May not be appropriate for the given corner, but it will get me slowed down. More beneficial than using the tranny.

ABS - I treat it as a safety net. 99% of the time, it doesn't engage on me. Only on some really bumpy spots does it kick in - like North Course Pocono entry onto the straight. It's good to know ABS is there, but better not to get into it - smoother is better. Oh - as for SLAMMING on the brakes - I do not advocate slamming on the brakes anywhere on the track, unless it is an emergency situation...

Regarding downshifting 5-4-3-2 or 5-2: I row through the gears. Simple reason: less chance of a mis-shift. Then again, I've been known to do the 5-3 downshift, and the 4-2 downshift from time to time.... I suppose it depends on the track, the corner, the entry speed, my mood, and if I ate chili for lunch.

-Z-man.

Larry Herman

That's my typical line for a corner. Not much room left if I overcook it.

Jim, you are most likely experiencing an incorrectly set rebound on your shocks. My car has the same ABS and ridiculously stiff springs. Once I got the rebound right, I rarely get into the ABS. For Summit, you need to go a little softer on the rebound so that the tires can stay planted on the track. If they get unloaded due to the bumps, and then cannot "rebound" because the setting is too stiff, then you lose grip.

Mike Murphy

Except that if you skip, you're using only 1 synchro to bring the gears up to speed instead of multiple synchros. Which means that 1 synchro will be more wear than the others.

I have to agree with that.

Mike Murphy

This is very impressive driving, and his car is extremely fast, but I do have one question, and go easy on me since I have not raced...

During some downshifting for turns, I noticed that the engine sounds like it is running faster than the redline. You can see the shift light come on during this time. A specific example is at 5:56, he downshifts for a left-hander and he does this immediately after hitting the "redline." I'm just wondering if that won't ultimately damage the engine? Or maybe he just has the shift light set low? If I understand it correctly, a rev limiter can not save you if you grab too low a gear at too fast a speed...

forklift

Thanks Larry!

SundayDriver

Two observations...

Many pros go through all the gears and many skip. There is clearly no right answer. However, skipping gears will result in much lower rear brake temps than rowing through all and letting out the clutch. Just because you see or hear one pro do it one way, does not mean that is the right answer. There are many, many ways to go fast. If you don't believe that, then try to find overlay data from different pros on the same track.

Slamming on the brakes (and smoothness) is overrated and misunderstood. I had the chance this week to look at a LOT of pro data and spend time with a top level data engineer. He says: you can NOT apply the brakes too fast you can only apply too much pressure. I agree. Pros go from zero pressure to max in less than 0.2 seconds - This surely qualifies as slamming on the brakes from a time standpoint. If you need gentle braking, you still go to whatever pressure very quickly. If you later need more, then add pressure at that time.

Veloce Raptor

I completely disagree about rear brake temps.

TD in DC

Why?

Veloce Raptor

Because there is no evidence, nor reason, why rear brake temps would be higher going thru the gears vs. skipping them.

SundayDriver

Well, it may not be universally true, but that was one example used in the data aq & vehicle dynamics class. We were asked why the brake data was so different between two pro drivers. The data showed that one rowed the gears and the other skipped shifts on a couple of corners. At other corners where both rowed the gears, brake temps were identical.

Do you disagree based on your thoughts or do you have hard data? (Not meant as an attack, just a question.)

Another thing that became clear in this class is that much of what we "think" we know, is dead wrong. Especially in the area of tire temps and what really happens based on data.

Veloce Raptor

Based on my thoughts. If you rev match PROPERLY, the same resistive force (i.e., braking) is exerted on all 4 corners as when you skip gears. If you use engine braking, which pros tend to avoid because they know better, then your supposition might be correct.

TD in DC

This is one of the many reasons why this sport -- and data -- fascinate me . . .

SundayDriver

And I thought the same thing. But then I saw data. Engine braking is when you are engaged and the engine is helping to slow the car - that always happens with a downshift, even if perfectly rev matched. I assumed that it didn't matter what the engine did, the brakes would do the same thing because of the pressure and bias, but that is not the case. Again, this was pro data from a top level enduro team, not a bunch of hacks like me.

Here was one of my favorites:
An Indy car in T1 at Indy has the following ride heights:
F 0.875" R 0.125" down the straight which provides lowest drag. But in T1
F 1.250 R 1.875 for good downforce. Realize this car is now seeing 2+ g's straight down just from the banking, plus the aero downforce.
So how in the world can it raise the ride height under far greater downward forces? (There is no active suspenion.)

Again, we don't really know what we think we know, especially when it comes to race cars.

SundayDriver

Ed Zachary

Veloce Raptor

But I still do not understand/believe that even a tiny amount of engine braking would have any effect on rear brake temps. I have a suspicion that the data you saw may have been related to driver style & braking inputs.