69sroadster Posted March 24, 2011 Share Posted March 24, 2011 Wow, there is some great teaching material on here from everyone sharing their experience and feedback (good or bad). I've learned that the reason my hood wobbles back and forth at the trailing edges is more than likely due to high pressure air trapped underneath. I'll fix that in time. I've also replaced my brake lines, rotors, calipers, and pads (porterfield? or hawk I can't remember). Also stepped up to the 17" Rota's with Nitto NT-05 235/40/17 up front and 275/40/17 in the back. I realize now that I could probably fit 255's up front with no problems. Well, I haven't messed at all with the proportioning valve and was wondering if this could help out some more after reading through a few articles about changing setups. It seems like my ZX is now a bit off balance into braking and I may need to swap out the prop valve for an adjustable unit. Without having some fancy tools, can I find my new sweet spot just doing some brake tests in a clear area or track? What would be the objective and subjective measurements to look at besides stopping distance? I guess a better way to ask that is what would I want the brakes to behave like at their optimum? Slight front bias? What would that look like? Thanks again. Maybe I'll just go to the AZC upgrade kit for the track work I want to get into. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 24, 2011 Share Posted March 24, 2011 (edited) The "optimum" bias point shifts around with grip conditions. Those vary with temperature, humidity, and tire temps and other factors. That is the very reason prop valves for racing are adjustable. On the street you don't need to be balanced to 10/10'ths of braking potential at all times. You just need to make sure that the rear wheels don't lock up before the front ones do, in panic stop situations. And you need to make sure that you CAN lock up the rear wheels, after the front ones do. You can test that carefully in a safe place. You want to be sure that in all possible conditions you could meet on the street, the rears don't lock up first. You will end up dialing in a lot more front bias than you would optimally have on a track (where the conditions for that track session don't vary so much so you can dial-in for that session). To my surprise, rain, will allow you to push the bias well to the back wheels, because the car does not un-weight the rear end so much due to limited tire bite. Test your car in a variety of dry conditions to make sure the rear end isn't locking up first, and that you can actually lock all four if you have to. Then decide if you need an adjustable prop valve. They are fun to play with but remember, you can't dial in MORE rear brake, you can only dial OUT pressure. Most pro racers use a balance bar mechanical system which is more precise than the hydraulic prop valves. Edited March 24, 2011 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
69sroadster Posted March 25, 2011 Author Share Posted March 25, 2011 Cool thanks. I'm out of town for a while, but when I get back I'll have to test this out. I don't think the rears are doing as much as they should from what I remember. I don't recall them locking up but maybe I didn't give it enough pedal pressure either. It seems to me like they haven't worn down much at all over the last year after the brake system rebuild. If this is the case and based on the tips you gave, I guess that would mean taking out the prop valve and putting in an adjustable one with less pressure restriction dialed in. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 25, 2011 Share Posted March 25, 2011 ...Assuming the rear circuit and brakes is working properly. Adding rear pressure to compensate for bad rear brakes would not be good... Quote Link to comment Share on other sites More sharing options...
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