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Old 12-03-2012, 03:20 AM   #1
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Default Brake Bias Questions

I am posting this here because it relates to race brakes.

When using a prop valve the rear brakes can be adjusted (assuming adequate hardware) to prevent lockup before the fronts. I understand the valve works by adjusting the knee point. What about below the knee point? Should you size the rear brakes to get better rear bias prior to the knee point for better overall braking?
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Old 12-03-2012, 03:43 AM   #2
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Hardware alteration will adjust the slope of the line, so it's best to dial it in as close as possible and then use the **** to make the fine adjustments.
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Old 12-03-2012, 10:20 AM   #3
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Hardware alteration will adjust the slope of the line, so it's best to dial it in as close as possible and then use the **** to make the fine adjustments.
This. I really need to post that spreadsheet for sizing brake components. Ideally you find your weight distribution under full braking acceleration and set that as your natural brake bias, but I've only ever run these calcs for cars that use balance bars rather than prop valves.
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Old 12-03-2012, 11:27 AM   #4
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Ya'll postin in an SJMarcy thread!
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Old 12-03-2012, 12:37 PM   #5
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Hardware alteration will adjust the slope of the line, so it's best to dial it in as close as possible and then use the **** to make the fine adjustments.
How would you evaluate that? I am guessing that the less bias **** adjustment needed (closer to full open) the closer the hardware is to ideal.
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Old 12-03-2012, 03:14 PM   #6
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Dumb theory question (for your amusement):

Is there any chance of getting too much rear brake so a knee-point adjuster would not be enough.
I'm thinking about locking up the rears before you reach knee-point pressure?
Or are the slopes set up so this would never happen on a weight balanced car?

I guess that would mean piston areas that would be absurdly off.

My plan for 11.75" went into repairing the house so I'll have to make use of NB stock + M-tuned rears another year.

The reason for asking is that I only have experience with three setups, NB, NB03 and the current one. None have been able to give too much rear bias (but the current one with almost fully open valve is close to balanced).

I.e. how easy is it to get too much rear brakes by not using the brain while picking rear calipers?
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Old 12-03-2012, 05:03 PM   #7
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How would you evaluate that? I am guessing that the less bias **** adjustment needed (closer to full open) the closer the hardware is to ideal.
Personal preference. You're right that running the **** full open and then altering components to get as close to perfect as possible gives you the closest thing to ideal braking from 0% to threshold braking. Having said that, I would much rather have the bias **** set in the middle of the adjustment, which allows me to make adjustments based on different tracks and conditions.

IMO, it's not particularly important to have bias be close to perfect when you're only using 50% of the available braking anyway, and I certainly wouldn't give up adjustment range to get better bias at sub-threshold braking levels.
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Old 12-03-2012, 05:05 PM   #8
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I.e. how easy is it to get too much rear brakes by not using the brain while picking rear calipers?
Easy. Go beyond 2:1 F/R piston area ratio and you'll quickly screw it up.
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Old 12-03-2012, 05:15 PM   #9
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Yeah you want at least some ability to add in more rear bias with your adjustability (be it a prop valve or balance bar). Because you're going to want to be able to give the car more rear bias in the rain and other low grip situations to prevent the fronts from locking.
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Old 12-03-2012, 05:40 PM   #10
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Personal preference. You're right that running the **** full open and then altering components to get as close to perfect as possible gives you the closest thing to ideal braking from 0% to threshold braking. Having said that, I would much rather have the bias **** set in the middle of the adjustment, which allows me to make adjustments based on different tracks and conditions.

IMO, it's not particularly important to have bias be close to perfect when you're only using 50% of the available braking anyway, and I certainly wouldn't give up adjustment range to get better bias at sub-threshold braking levels.
Excellent points! I will set things up to allow for a fair amount of rear bias adjustment.

Thanks!
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Old 12-03-2012, 05:45 PM   #11
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Thread synopsis: Buy our 11.75 kit and our prop valve kit and mate it to our upcoming lightweight rear kit, stock calipers + M-Tuned brackets, or a full rear OEM Sport setup.
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Old 12-03-2012, 06:03 PM   #12
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Your 11.75 kit is what I really wanted but cash is still tight. I ended up trading some injectors I had and a little cash (very little really) for a 11" wilwood kit with 949 rotors. I have sport rears sitting on the shelf along with sport master/booster. I am going to use some of the above parts for the time being then do the TSE upgrade kit when I am ready for rotors.

With your kit rotor temps front and rear (sport rotors) ended up almost the same. That is ideal. Also bias split looks great using same compound pads front and rear. Another huge plus!
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