rags Posted July 22, 2011 Share Posted July 22, 2011 Well I went ahead and installed the 6 piston setup for the front that AZC sells to help with the brake over heating codition I was experiencing with the Toyota 4 pots. I did make some modification to the kit as I wanted to use a slip over lug design rotor hat. Everything fit perfectly. What I am noticing now is brake bias front to rear is really screwed up! I am using MM 240SX rear disk setup which did the job previously but now seems to be woefully under powered. Front brakes lock very easily now and it doesn't seem like the rears are even getting a chance to do anything with the amount of pressure needed to lock the fronts. Obviously an adj prop valve won't help here. Could there be something wrong with the stock prop valve or are the new front calipers just that much better than the rears? My thinking doesn't want to believe the latter! Joe Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 22, 2011 Share Posted July 22, 2011 So wait, do you have an adjustable proportioning valve? If you don't, why wouldn't it help? Quote Link to comment Share on other sites More sharing options...
rags Posted July 22, 2011 Author Share Posted July 22, 2011 No prop valve. Putting one in will only reduce the amount of braking to the rear. Right now I don't have enough rear braking! Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 22, 2011 Share Posted July 22, 2011 Couldn't you attach the prop valve to the front brake line instead of the rear brake line? Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted July 22, 2011 Share Posted July 22, 2011 (edited) I'm confused if youre running no proportioning valve or the stock one. If youre running the stock one, it would be worth removing it and running full pressure to the rear, or putting in an adjustable valve and adjusting it so it gives more pressure than the stock valve. Aside from that I think that the Willwood 6 piston calipers are much more powerful than the 240sx rear calipers. Even with full line pressure to the rear it will not be enough to get rid of the huge brake bias. It will take additional work to get the balance more ideal with this setup. Putting a proportioning valve in the front could work but really kind of defeats the purpose of going to Wilwood 6 piston calipers in the first place in my opinion Edited July 22, 2011 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 22, 2011 Share Posted July 22, 2011 (edited) Need more info. Like others have brought up, We need to know what pads you are using, existing factory components, rear disk make and model, etc. I am thinking that this is a mismatched system at best. You might be able to change pad types and get better bias, but the temperature would become a critical part of the equation since many high friction compounds don't grip until they are HOT. Edited July 22, 2011 by bjhines Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2011 Share Posted July 22, 2011 Never put a prop valve in the front! I suspect that the options are: a. bigger rear brakes or b. dual masters. Quote Link to comment Share on other sites More sharing options...
wheelman Posted July 22, 2011 Share Posted July 22, 2011 (edited) Never mind, Jon beat me to it. Edited July 22, 2011 by wheelman Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 22, 2011 Share Posted July 22, 2011 Pardon my ignorance but why don't you proportion the front? I'm sure there's a good reason, I would imagine it has to do with, you're just limiting total braking power, but if you could explain I'd appriciate it. Quote Link to comment Share on other sites More sharing options...
rags Posted July 22, 2011 Author Share Posted July 22, 2011 Prop valve in the front is not an option as Jon stated. The rear calipers and rotors are from a 240SX and part of the MM offering. Pads in the rear are Hawk HP plus. Front pads? No idea. Whatever comes with the AZC kit. Jon, when you say bigger rear brakes, are you referring to piston area or pad area? Joe Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2011 Share Posted July 22, 2011 Pardon my ignorance but why don't you proportion the front? I'm sure there's a good reason, I would imagine it has to do with, you're just limiting total braking power, but if you could explain I'd appriciate it. It's all here. The short version is that prop valves aren't actually proportional, so if you put one in the front, the harder you stepped on the brakes the more rear braking you would get. http://www.stoptech.com/tech_info/wp_proportioning_valves.shtml Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 22, 2011 Share Posted July 22, 2011 Good read. Thanks for the info John! Quote Link to comment Share on other sites More sharing options...
rags Posted July 22, 2011 Author Share Posted July 22, 2011 One question I have from the read, how can rotor diameter effect brake bias?? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2011 Share Posted July 22, 2011 Larger rotor diameter is in effect a bigger lever, so the same caliper will have more effect on a larger rotor. Quote Link to comment Share on other sites More sharing options...
rags Posted July 22, 2011 Author Share Posted July 22, 2011 Ahh got it. Further out from the center the easier it is to stop the disk! I kept thinking heat dissipation was the only reason for a larger rotor. I'm glad I asked Quote Link to comment Share on other sites More sharing options...
mark Posted July 22, 2011 Share Posted July 22, 2011 Pull the pads. Front and rear. Brand and compound will be on the back of the pad for any decent pad. Post what you got. I'm betting most of this can b e fixed with changing pad compound. Are you using the stock proportion valve?. Quote Link to comment Share on other sites More sharing options...
mark Posted July 22, 2011 Share Posted July 22, 2011 How does the piston area compare between the 6 pot wilwoods and the 4x4 callers? Anyone know? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2011 Share Posted July 22, 2011 If memory serves, Dave is using this caliper: http://www.wilwood.com/Calipers/CaliperList.aspx?subname=Billet%20Narrow%20Superlite%206%20Lug%20Mount so the piston diameters would be 1.62, 1.12, and 1.12. I think the Toyota calipers had staggered pistons as well, would need the diameters there to get a comparison. Quote Link to comment Share on other sites More sharing options...
EvilC Posted July 22, 2011 Share Posted July 22, 2011 Ahh got it. Further out from the center the easier it is to stop the disk! I kept thinking heat dissipation was the only reason for a larger rotor. I'm glad I asked Guess you had to read it on the internet to believe me, we won't get into the issue of number of pistons in the caliper and how that effects braking also. For right now, as we know.....you need to change the rear pads and do another "brake test". Also need to do it on the same pavement setting and near the same road temp. With the stock setup right now and the 6 piston fronts/240sx rears.....I believe the fronts are doing 90% of the stopping. I rears don't even get a chance to lock up when applying the brakes. I believe it was probably a 3/4 pedal effort for the fronts to lock. 1 Tuff Z went through something similar with have MM 13 inch rotors upfront and 240sx rears. In the long run he had to get LARGER rear brakes. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 22, 2011 Share Posted July 22, 2011 Seems timely as I just brought it up on another post, but here again is Neil Robert's suggestion on how to test bias, which doesn't require flat spotting tires: http://forums.hybridz.org/index.php/topic/99500-tail-wagging-under-hard-braking/page__view__findpost__p__932930 Quote Link to comment Share on other sites More sharing options...
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