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Author: Subject: Help solve my brakes problem...
james h

posted on 29/4/09 at 08:19 PM Reply With Quote
Help solve my brakes problem...

Hi all,

Wondering if you could help me with my brakes issue...

Front brakes are Wilwood Powerlite 4pot, on 257mm solid discs.

Rear brakes are Wilwood Powerlite handbrake calipers (4pot again) on 273mm solid discs.

So my rear brakes are larger, ie more powerful it seems than my front ones.

What can I do to reduce the braking power of my rear brakes, or do I get bigger front ones?

James

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clairetoo

posted on 29/4/09 at 08:23 PM Reply With Quote
How about swopping the front and rear disc's around ?





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mookaloid

posted on 29/4/09 at 08:23 PM Reply With Quote
fit an adjustable brake bias valve so you can adjust the braking to get the optimal setting front and rear.





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StevieB

posted on 29/4/09 at 08:23 PM Reply With Quote
You could fit a bias adjuster to the rear brake circuit to reduce the braking effort and balance things out again.

You could also consider fitting better pads to the front than the rear.

On a recent trackday with my own car, a very experienced mate took my car out and reckoned that the sierra master cylinder didn't allow enough brake feel. A twin cylinder setup might be the way around this, with the added bonus of being able to adjust front/rear braking effort via a balance bar.

I'm considering fitting an OBP pedal box to my Infy and fettling the bulkhead to accept twin m/c's

Bigger discs don't increase braking effort, they simply aid cooling under constant hard braking, it's the brake circuit, the caliper and the pad that effect the amount of effort under braking.

[Edited on 29/4/09 by StevieB]

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blakep82

posted on 29/4/09 at 08:33 PM Reply With Quote
also with twin m/cs, you can have different size m/cs on the front and rear





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james h

posted on 29/4/09 at 08:37 PM Reply With Quote
I can't swap the discs around, the bells on them are different depths unfortunately.

I thought bias adjusters needed inputs from front and rear brake lines into the bias adjuster. So infact I can simply run the bias adjuster in just the rear brake line then?

But then I also have to think about my SVA retest...

As long as I don't drive the car before SVA, what about the pads suggestion? More worn pads on the back? Very effective pads on the front?

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StevieB

posted on 29/4/09 at 08:43 PM Reply With Quote
Have you got a set of standard sierra calipers you could fit for SVA?

I;m not sure on the rules of brake bias adjusters, but IIRC as long as it can;t be adjusted from the drivers seat it should be OK - I would get confirmation that this is the case first though.

Rally Design now sell Mintex pads to fit the powerlights, so you get the best sticky pads they have to offer for the front and the cheapest ones for the rear, but I;m not sure how effective this would be in balancing things out.

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minitici

posted on 29/4/09 at 08:47 PM Reply With Quote
Do the front and rear calipers have different size pistons?
This needs to be factored into the equation along with pad / disc areas and front and rear master cylinder sizes.......

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james h

posted on 29/4/09 at 08:52 PM Reply With Quote
Ah right so I could have a bias adjuster then? Will have to check up on the rules then.

I have just got the standard pads that came with the powerlite kit, will need to see exactly what they are.

Dual MCs sound good but I don't have the money for them at the moment, unless some good bargains come up at Stoneleigh.

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james h

posted on 29/4/09 at 08:54 PM Reply With Quote
quote:
Originally posted by minitici
Do the front and rear calipers have different size pistons?
This needs to be factored into the equation along with pad / disc areas and front and rear master cylinder sizes.......


Standard sierra MC, so if its piston diameter is what you mean, then they will be the same.

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brianthemagical

posted on 29/4/09 at 09:21 PM Reply With Quote
Disk dia does make a differnece. the pads provide a braking torque to the disk, the magnitude of which is, T=FxR, R being the mean radius of the disk, thus, a bigger mean radius produces more braking effort at the wheel.
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ashg

posted on 30/4/09 at 07:17 AM Reply With Quote
get a fiat rear bias valve. they can be found on the older punto cinquecento, bravo and tipo. they basically have a spring to a fixed point that adjusts the rear brake power depending on the weight over the rear axle.

you can either make a bracket so the spring adjusts the braking bias or just set it in the position you want and lock it off.

[Edited on 30/4/09 by ashg]





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