sportster98xls

Hi,

I have a 40th Anniversary.

I upgraded the brakes to 6 pot GT3 Mk 2 front and rear.

Do i have to refresh the Ecu of the ABS for this upgrade?

The reason i ask is, the ABS seems to come on too early when i brake hard thereby increasing the stopping distance.

Please advice,

Thanks

Ray S

I'd start by making sure the ABS sensors are clear.

Tippy

Im assuming the front tires are sliding first causing the ABS to activate, I wonder if a proportioning valve could cure this problem as my car has the same issue. Add more braking pressure to the rear and less to the front.

10 GT3

Do you mean you upgraded to GT3 brakes (front and rear) or did you pout GT3 6-piston front brakes on the rear of your car? If it is the latter, your problem isn't ABS; but too much rear bias. To run that big of a caliper in back and you will need an adjustable proportioning valve to reduce rear bias.

Ed Newman

I think he may have put the fronts but not rears on and is getting too much front bias. Brakes are a system and need to be upgraded evenly or proportioned otherwise. I am running GT3 MkII brakes on my C2 with the stock and there are no ABS issues. Acutally, it ABS's less with them and the bigger brakes are easier to modulate.

sportster98xls

Hi Tippy,

I think you are right ! The distribution ratio is affected !

Has anybody changed their proportioning valve before ?

Do you have the part number ?

I have 6 pots front and 2 pots rear (complete set of GT3 mk2) brakes.

thanks

Ed Newman

Ok, if you are running a complete set of GT3 MK II brakes you should not need to change anything else. What tires/sizes are you running and what brake pads are you running? Is the ABS activating on the fronts or the rears?

arenared

If you're front 6-pots just bolted on, you have the larger wheel carrier bolt centers and then probably had the 330mm F&R setup before. Assuming you went steel, going to a 350/330mm setup will give you more front brake bias (~6%). (The rear 4-pots didn't change.) Additionally, the 6-pots have a hair (<1%) additional front bias due to their particular piston configuration.

Changing the brake/ABS hydraulic unit is going to cost a fortune (several $K). I really wish there was a brake god out there who knew how to mix/match the various units along with the electronics dependencies. The traction control and PSM are done there as well. It's not something you can adjust or tinker with. Anyone know somebody?

Your best bet is to play with pad compounds. There are several threads on brake pads. A second alternative would be to fit the 350mm rear PCCB calipers and use the 997 350mm steel rotors. Don't quote me on the exact rear rotors. They could be cup or something, but you can find them over on the GT2/3 boards.

LVDell

Never understood why some feel the need to upgrade the brakes like mentioned here. You can get phenomenal braking by utilizing the PROPER compound for the intended purpose. I run RS19's in my 996CAB on the track and can make your eyeballs pop out of their sockets. No need to "upgrade" the braking system other than pads and fluid. Granted the brakes in my GT3 stop even better (not significant but still better) running RS19's as well. Unless you have totally upgraded your suspension and are running r-Comps or slicks, then why even waste the money on MkII brakes on a standard C2? Seat time will get you faster.

sportster98xls

Hi Ed,

225/40/18 front

285/30/18 rear

standard GT3 pads ( P yellow )

ABS comes up too early on the fronts !

Ohh mighty Brake God, pls give me the part number for the diverter valve !

Cheers

Ed Newman

Trust me you don't want to get into a diverter valve. You are looking for trouble. What brand tires are you running? Michelin Pilots, MPSC, Hoosiers, etc. I would also think about an aftermarket pad. The stock pads are designed for street use, not track. And not to ask the stupid question, you are talkign about this problem occurring on the track at a DE or the like, right?

sportster98xls

Hi Ed,

ok, will not go there. thanks

Pirelli (0) Rosso

I am going to do that, use better bite pads for the rear. Any recommendations?

er... it was on the street. it happened when the lights turned red when i least expected it to ! Slamped on the brakes and was very dissapointed with the stopping distance !!

Did not notice this problem when i brought the car to the track...

Thanks again !

Cheers