Professor Helmüt Tester

When it rains, an easily-adjustable brake bias diddle is REALLY important.

Bryan Watts

If the sun is revolving around the moon while the deer breasts lay in the lillies, does popcorn pop in a vaccum? What if the vacuum is a Hoover? If no one is around to see the popcorn pop, does it really pop? Choices: A or B

mark kibort

thanks Ken and Bryan.

Im getting excited to see what happens. Ill probably do some testing at sears, as too much rear brakes at sears can be a problem.

mk

PedroNole

I've noticed a very big difference coming from my very light 911 with Tilton Dual Master with adjustable bias vs. my 996 Cup with fixed bias and ABS.

Like Larry, in my 911 I trail brake into most of the corners at a given track. However, with the Cup (at least so far) I find that I can't drive the same line/style because I get rear lock and just generally less stablity when trying to turn and brake. It's not the geometry of the car because obviously the cup car is superior but I would actually dial OUT some rear in the Cup if I could. I know it would be faster for the way I DRIVE. However, since I can't do that, I'm having to adjust my driving style to fit the set-up.

Premier Motorsp

Not WAY too high. Just a hair too high. This is the highest I have seen on any Porsche.

IcemanG17

MK
I thought stock was 17? I don't even have a stock one...just the one thats in there? All I know is the brakes seem to work just fine! So much so that I find myself having to tighten up the harness more and more as I use more of the brakes.....didn't have that problem in the street cars!

Remember Anderson took the bias bar OUT when he put the big brakes on the front!!! So he gets the same pressure all around!!! Seems crazy, but clearly his brakes work just fine....

mark kibort

Like I said, i dont know the bar level, but mine is stock for an 86.

Anderson really runs full pressure to the rears? I guess he can do that when he runs the F50 , 14" rotors up front.

what ever i have for the rear, im going to turn it up. its got to be too light, as i havent changed my rear pads in over 50 race days!

mk

Bryan Watts

Sheesh. What particular Porsche? Are we talking a flat bottomed, large rear wing ALMS car? I could see those approaching 2...but it's still sounds pretty high for longitidinal G's based on what I've seen out of high end club racing sedans and winged open wheel and sports racers. Based on the way the braking G's get lower and lower steadily as the car is losing speed, it would seem to be a case of some downforce contributing to the braking grip (and maybe adding some drag at high speed as well).

Did the driver got his foot hung on the throttle a bit at around the same point he hit his maximum braking G's? What's the purple line at the bottom of the plot?

mark kibort

where was that and what kind of "porsche"? Yours?

mk

Premier Motorsp

Yeah it is my car. 993 RSR w/o significant downforce (has some though, normal big wing and splitter). It stops well because it is light, draggy, ***-heavy, and has big front tires compared to a 996/997 Cup car. It also has very effective ABS.

My foot (size 14) is kinda big so often I have a little throttle on during braking. I know it isn't good.

The purple line is brake pressure in bar. It tapers off after the initial hit because I braked too early, as I always do.

This is braking for 10a at Road Atlanta. The downhill is adding to the negative long G a little bit. I think the pavement is really good there. I usually cannot get over about 1.65G under braking.

Chris Cervelli
Spline Technologies

Bryan Watts

Downhill would add to the "recorded" G's of the accelerometer, but should actually decrease your braking ability, right? I wonder just how much the downhill is playing into the readings, because 1.99 seems really high comparatively. Even 1.65 sounds really high for what I would expect. I would expect numbers more around 1.2-1.3 like the 997 Cup car data from this year's Daytona 24 posted on the first page of this thread. What data acq system are you running? That's scary good braking for a tin top.

I don't have any data saved on my work laptop...makes me anxious to see what sort of braking G's we're hitting at 10A as compared to flatter braking zones at other tracks.

For what it's worth, the left side of the track at T10 is even grippier and less bumpy than the right. But you can really only use it in the wet because it blows your 10A entry in the dry. I love the 10A/B complex for some reason...one of my favorite turns on any track when I'm going through there well.

Larry Herman

I would see 1.3~1.4 on my RSA with 993TT brakes and Hoosiers. I used a G2X data logger.

Veloce Raptor

Yup, we would see 1.3 on our Grand Am Cup 330i with Hoosiers and PFC01's.







Professional Racing and Driving Coach

PedroNole

So, you obviously need to adjust your bias mechanism....

Veloce Raptor

Hahahaha! If only we were allowed one. Actually, truth be told, that car SUCKED in braking, until we went to PFC01's at the Glen. Then, I could brake at just before the 100 marker, and the car was perfect.







Professional Racing and Driving Coach