dat240z Posted October 27, 2012 Share Posted October 27, 2012 Hey looking for some advice on my locking rears Im going through eningeering and the discs on the back are locking up before the fronts. Engineer wont be happy. Have tried a prop valve but its still biting first. Any ideas/suggestions guys? Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted October 27, 2012 Share Posted October 27, 2012 Just a few thoughts: Is the proportioning valve plumbed the correct way? Screw it in the opposite rotation and see what happens. Can it be set to 'fully disengaged'? If you got it from Arizona Z let me know and I'll visually inspect mine (still in the packet after 4 years!) to see if it can. Are the 'fronts' fully bled? How close to the M/C is the proportioning valve? What M/C are you using? Make sure it doesn't have a built-in proportioning valve. Quote Link to comment Share on other sites More sharing options...
jamo240 Posted October 27, 2012 Share Posted October 27, 2012 You also need to be sure the ratio of front/rear piston diameters is within the authority of the prop valve...by that I mean the prop valve does not have infinite ability to reduce the pressure to the rears to nothing, so if youre front/rear ratios are too far out by design (ie rear pistons are too big), the prop valve may not be able to reduce the pressure enough. In that case, you either need larger diameter pistons at the front, or smaller at the rear. I had the opposite problem on mine originally...when I had VS Commorodore rear calipers (36mm dia), no matter how much pressure i fed them I could not lock up the rears, so I went to VT calipers (44mm dia), and then I could. From there, i could use the prop valve to balance them up so i have the fronts locking first. Cheers Jamo Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 27, 2012 Author Share Posted October 27, 2012 Thanks guys, its a arizona z car prop valve yeah. Im using a 15/16 master cylinder off a 280zx i think. I have the 4 piston calipers all round (dynalite + superlite). The fronts are visibly larger but both 4 piston. Prop valve is on the rear line a few feet from the m/c NOt 100% on bleeds or if it has a prop built in. Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted October 27, 2012 Share Posted October 27, 2012 The Wilwood + Wilwood has been fitted many many times so it might be worthwhile to look on HybridZ to see if this issue has been raised and solutions offered. I can't offer a specific thread but see if 'search' offers up something. What are you doing for a handbrake? Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 27, 2012 Author Share Posted October 27, 2012 Yeah that was my next stop. Handrake has been based on woz's kit of using a spot caliper and custom mounting plate/handbrake cable. It works ok, but will be useless if i need other rears.... Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 27, 2012 Share Posted October 27, 2012 I am keen to see the outcome of this, I do have some issues, though I think I'm just going to take it to ACT Brakes and get a bias adjuster installed while I'm at it. Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted October 27, 2012 Share Posted October 27, 2012 I've just dug out my proportioning valve and it still has seals on the ports and knowing the rate of progress on my project (it could be another four years before it gets fitted!) I don't want to break the seals just yet... apologies. It may not have been much help anyway but at least you could have checked if your front are working properly. (edit) The Wilwood web site indicates that you can only alter the rate from 0 to 57% so you can't block off the rears completely. http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-8419 Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 27, 2012 Author Share Posted October 27, 2012 Thanks guys for all your help. This bias adjuster sounds interesting..........? Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 27, 2012 Share Posted October 27, 2012 You can pick up Wilwood bias adjusters for around $90, but they would have to redo some of your brake lines too and aren't road legal. Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 29, 2012 Author Share Posted October 29, 2012 So the adjustable prop valve didnt work well enough, so now my only other idea is to get rid of the stock prob valve all together and see what happens. if this fails, it looks like a r31 rear replacement:( for engineer rego Quote Link to comment Share on other sites More sharing options...
jamo240 Posted October 29, 2012 Share Posted October 29, 2012 If you are using a combination that is well proven on other people's cars, I would look a little further before replacing anything else. Why don't you get a couple of brake hose clamps (available from tool shops) and clamp the rear lines off at the calipers and make sure you can actually lock the fronts up at all. It would be good to diagnose which part isn't working before changing anything else. Cheers Jamo Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 29, 2012 Author Share Posted October 29, 2012 Yeah I am waiting for a reply from the seller in USA but removing the stock prop valve may be the answer. Its not that anything isnt working properly, its just the rears are too powerful. Will find out in a few days Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted October 29, 2012 Share Posted October 29, 2012 I'm with Jamo on this, you really need to check the front brakes and M/C to see if there is an issue there. Just some basic points: are the front calipers mounted with the nipples up, and, did you bleed them both? Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 30, 2012 Share Posted October 30, 2012 Consider if you need to swap the lines front to back leading into the MC. Quote Link to comment Share on other sites More sharing options...
Jk_zeder Posted October 30, 2012 Share Posted October 30, 2012 This is a common occurrence with the wilwood setup from AZC. Even when running a bias with all fronts and zero back you will still find a problem. A lot of the guys up here have ended up running a 1" cylinder and smaller rear pads so you can still have some adjustment with the bias. Quote Link to comment Share on other sites More sharing options...
620Z Posted October 30, 2012 Share Posted October 30, 2012 OK something you probably never considered. What is the toe in on your rear wheels. Have they ever been adjusted to with in .5 of a deg. I they are out 5-7 deg then yes you will lock up every time when running the car hard. As I used to on the track. Sure I put the brake bias in and it worked great. But after I aligned the rear wheels the problem was solved and now my front to rear brake bias has not been used in 8-10 years. Just something else to consider. Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 30, 2012 Author Share Posted October 30, 2012 Thanks for all the suggestions fellas. I took the car out to get a quote for paint and panel yesterda, but will be back at the mechanics tommorrow to sort this issue out. All the ideas thrown out are plausable and will be used until a resolution is found. The nipple and orientated in the correct position. I think what we will do is ensure the fronts can lock up but isolating line. After that, new softer pads on rear. Swap lines (front - back from MC) and adjust toe/camber etc. When I purchased the brades off AZC I also got the 3 way adjustable coilovers so maybe thats thrown the angles out slightly aswell.... On a good note, quoted $4-5k paint/panel/replace all weatherstrips and reassemble.... Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 30, 2012 Share Posted October 30, 2012 Good to hear its coming along. Who is doing the body work? Scott? Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 30, 2012 Author Share Posted October 30, 2012 I took the z out for a spin out to Braidwood and met Dave (Dingo Dave) from the forum. He has all facilities out on Station Rd and owns a 260 2+2. That also includes smoothing rear end (removing bumper) and a month turn around. Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 31, 2012 Share Posted October 31, 2012 Oh ok, cool. He has a lot of skill with metal work and he's a good guy. I don't think I have seen his painting yet. Quote Link to comment Share on other sites More sharing options...
dat240z Posted October 31, 2012 Author Share Posted October 31, 2012 Yeah hes a nice bloke, and definatley more talented than me. Car just dropped to my mechanic, hopefully brakes sorted/engineer/paint by jan/feb. Quote Link to comment Share on other sites More sharing options...
sco_aus Posted October 31, 2012 Share Posted October 31, 2012 Good stuff, you going to christen it at the Nationals? Quote Link to comment Share on other sites More sharing options...
dat240z Posted November 1, 2012 Author Share Posted November 1, 2012 Ok so in order to elimate the AZC Willwood rear brakes issue this is whats required. Install adjust prop valve from kit Remove stock prop valve from near m/c And its all done!! I took it for a spin and fronts lock up everytime now. Cannot operate with two valves. I even think its stopping harder and faster than before, which is saying something considering the brakes were great before. Thanks for all your help and advice guys, love this forum! When are the nationals and where? Are any ACT zedders making a convoy? Quote Link to comment Share on other sites More sharing options...
sco_aus Posted November 1, 2012 Share Posted November 1, 2012 Good stuff mate. I'll keep that in mind when I get mine done. I only have the R31 (mine are from a Canadian Maxima, but same thing) rear disk setup which changes things a little. Quote Link to comment Share on other sites More sharing options...
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