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914World.com _ 914World Garage _ Rear Brake Hop

Posted by: nine14cats Sep 8 2003, 10:31 PM

Hey Guys,

Here's a question on braking bias and how to solve a little occasional rear hopping. First the stats on the car:

911T Front Suspension including rotors and calipers
'87 944 Front rotors and 914-4 Front calipers on rear.
23mm torsion bars front, 250lb springs rear
Bilstein shocks all around.
22mm Front Swaybar, 16mm sway rear.
Prop valve replace by brass T.
Porterfield R-4's (fronts) all around

Issue:

On the track I love the brakes...not fading (I know, i'm not going fast enough) and it feels really balanced. On auto-x courses under HARD braking I get rear wheel hop. I have to admit that with more seat time I'm getting smoother and even my braking is getting better and the hopping is going away. But it's still there a little.

My question is: is it all driver modulation related? or is the mechanical balance off? On the tracks it's great, but I get it occasionally on the auto-x courses.

Thanks,

Bill

Posted by: Brad Roberts Sep 8 2003, 10:33 PM

In a straight line ?? Loaded or unloaded side ??

B

Posted by: nine14cats Sep 8 2003, 10:35 PM

Hi B,

Only when the rear unloads and in a straight line. If there is any weight on the rear (either side) it doesn't happen.

Got me an answer?

I'm betting it's driver

Bill

Posted by: Brad Roberts Sep 8 2003, 10:40 PM

The T is too much rear bias in this case. It will go away with the LSD.

If you want to cure it for autoX.. run stock 914 pads in the rear calipers (poor mans bias adjust after installing a T)

B

Posted by: nine14cats Sep 8 2003, 10:43 PM

Thanks B,

I have a nice set of stock pads in the garage. I'll throw them on and let you know how they did at next weeks auto-x. I won't be getting to the LSD until the season is over.

Bill