Different compounds on front and rear?
09-14-2007, 05:47 PM
#1
Melting Slicks
Thread Starter
Different compounds on front and rear?
So I was wondering why people like to run different pad compounds on the front than on the rear for racing purposes? The main reason I ask is cause I see some people saying run x10 front and x12 rear, and some saying the opposite?
Initial thinking would be to run the same compound on all 4 corners, but then every time I have spun was under hard braking and the rear came around - so that would lead me to want to run a slightly less agressive compound on the rear, right?
Just getting started here so sorry if these are stupid questions...
Initial thinking would be to run the same compound on all 4 corners, but then every time I have spun was under hard braking and the rear came around - so that would lead me to want to run a slightly less agressive compound on the rear, right?
Just getting started here so sorry if these are stupid questions...
09-14-2007, 08:45 PM
#2
Drifting
XP12 front and XP10 rear is pretty popular. I have run same compound front and rear, but would probably not run higher grip pads in the rear. I suppose ABS might fix a potential bad bias set-up, but I would not chance it. If the rears do a disproportionate amount of braking I think you will spin.
09-16-2007, 07:06 AM
#4
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Hi guys. I'm new here but i've been autocrossing for almost 2 years now and have a little experience with this.
When the factory builds a car they engineer the brake bias safe as possible, at factory ride height with factory shocks and springs most cars will lock a front wheel slighly before the rear, but high performance cars need more brakes so they have to add rear bias to get more braking force.
The old Porsche i race now(hoping to replace with a c-4 shortly) will lock a front evey now and then, the sts2 Miata that I've been co-driving had severe braking issues! After changing springs and shocks and alignment and new hawk pads all the way around the car would lock the front wheels and drive straight off course!! These cars have excessive front bias and as we made it stiffer we made that condition worse, the fix was really aggressive rear race pads and the cheapest autozone front pads available. So thats why we're taking a car to nationals next week with autozone front pads!! I think thats why some cars can get away with the same all around and some can't, different shocks, springs, driving style. Its all about finding balance.
When the factory builds a car they engineer the brake bias safe as possible, at factory ride height with factory shocks and springs most cars will lock a front wheel slighly before the rear, but high performance cars need more brakes so they have to add rear bias to get more braking force.
The old Porsche i race now(hoping to replace with a c-4 shortly) will lock a front evey now and then, the sts2 Miata that I've been co-driving had severe braking issues! After changing springs and shocks and alignment and new hawk pads all the way around the car would lock the front wheels and drive straight off course!! These cars have excessive front bias and as we made it stiffer we made that condition worse, the fix was really aggressive rear race pads and the cheapest autozone front pads available. So thats why we're taking a car to nationals next week with autozone front pads!! I think thats why some cars can get away with the same all around and some can't, different shocks, springs, driving style. Its all about finding balance.
09-16-2007, 06:20 PM
#5
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I think the reason most run the different compounds is operating temps. The rears simply don't get quite as hot as the fronts.
In the case of a Miata (NA and NB), they are terribly defaulted to strong front bias. In my years of campaigning them, I eventually ran no brake bias valve, just straight through couplers. It made a HUGE difference. In the case of earlier NA models, you can just gut the stock valve and get much more rear bias without the pain of sourcing those couplers.
In the case of a Miata (NA and NB), they are terribly defaulted to strong front bias. In my years of campaigning them, I eventually ran no brake bias valve, just straight through couplers. It made a HUGE difference. In the case of earlier NA models, you can just gut the stock valve and get much more rear bias without the pain of sourcing those couplers.