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blandy

Rear brake bias

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blandy

I have a bias valve in my car (lever type).. 

 

what level of bias are you guys running on track and can anyone explain why more or less is preferred? I understand the rears do less braking etc but want to play with the balance but intreguied as to the reasoning why more or less is preferred 

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petert

Typically a 205 at rest will have 280Kg on a front wheel and 130Kg on a rear wheel. Thus straight away, you can see why less braking is needed on the rear. Under heavy braking, weight transfer will change that ratio dramatically. Even though we always try to brake in a straight line, there are circumstances when a rear wheel will become near fully unloaded under brakes, whether from corner, road camber etc. Thus rear wheel loading may vary from 0-130Kg. My first track 205, not built by me, had two bias valves in series; a lever and screw type. It worked very well. After I sold that, I re-built somebody else's project and fitted just a screw type. It was always very delicate to get the right balance. My third attempt uses a pedal box, which is a lot easier to adjust. To get the balance in the range, set the car up on 4 stands. Using a torque wrench, with the front brakes just locked, you should still be able to rotate a rear wheel. You'll need to fine tune on the track. Some FWD race cars which aren't allowed bias valves, cheat by fitting a ball bearing in the rear brake line, effecting giving 100/0% ratio.

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blandy

Thanks couldn’t of asked for any better. much appreciated I’ll give it a go 

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Tom Fenton

In practise I would use as much rear bias as you can get away with, without locking the rear wheels. As standard the cars are set with very little rear brake effort. You can usefully increase the work the rear brakes do, it all contributes to stopping the car. Main difference is wet/dry as to how much you can use. Can’t say I’ve ever set it up statically as described above, just by altering the setup bit by bit while driving the car.

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allanallen

Something to bare in mind when setting up is what pads you have in each end and how quickly they warm up. I’ve caught myself out several times barrelling into corners with cold front (race ) pads (standard rears), stamping on the brakes to find massive rear bias and laterly big streaks of s*it in my underpants! 

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petert

Agreed and don't get conned into buying expensive pads for the rear. As they won't be really doing anything, standard pads work just fine.

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blandy

Mmm maybe a tad late for that I picked up a cheap set of new unused ds2500’s for the rears as recommended previously on Facebook to go with my ds3000’s in 4pots on the front.. about ten secs before miles said exactly the same of just going for standards.

 

Is it reallly a bad idea to run these? I’m due on a day out on Monday lol 

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Richie-Van-GTi

Having the expensive pads isn't necessarily a bad thing, just a waste of money.

I tweak mine to be able brake pretty flat in the dry and knock it back a notch for wet. That's with a 7 position lever valve.

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