RLY240 Posted August 25, 2014 Share Posted August 25, 2014 I'm starting to experience very bad pad knock back in the 240 during track sessions at Mallala. It's not something that has been a problem before but since moving to the wilwood setup it is quite pronounced. Even doing some weaving on the warm up lap is enough to make the pedal drop significantly. I have new wheel bearings front and rear with the front's tightened to factory specs (20ft/lb I think then minus 60deg) and there is no play to be felt either front or rear. A quick tap is enough to get the pedal back up but it's quite disconcerting. Anyone else experienced this with the wilwood setup? Roger Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 25, 2014 Share Posted August 25, 2014 How are the discs on runout? Could be an idea to get them onboard skimmed. I get knock off about 3 laps in, combination of things, but i pull handbrake on just 1 notch, and this helps, then 3 laps later, pedal teavel is a lot, again, it takes a quick tap tap with left foot, then full pedal right foot hard for the big brake corners.. Using stock Z calipers, i find a fresh set of caliper seals helps reduce it, due to stiffness of new seals, which are designed to pull piston back a touch, but not overly much. Quote Link to comment Share on other sites More sharing options...
Gordo Posted August 25, 2014 Share Posted August 25, 2014 Since I went to Willwoods I have experienced the same thing. Haveing to tap the peddle befor braking. I've tightened the bearings and bleed the brakes . I've found this set up very hard to bleed convincingly . I'm using hydrolic thread locker on the bleed nipples because was leaking through the thread. Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 25, 2014 Share Posted August 25, 2014 Hearing other cars using Willwoods also have similar issues, what is it with them, maybe our caliper ear mount pisition is not right? The weeping threads thing is def not right! Quote Link to comment Share on other sites More sharing options...
zzzzed Posted August 25, 2014 Share Posted August 25, 2014 I get it to. Quote Link to comment Share on other sites More sharing options...
Riceburner Posted August 26, 2014 Share Posted August 26, 2014 240 or 260 hubs, Could they be flexing slightly? Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 26, 2014 Share Posted August 26, 2014 Not so much the hubs, thats a runout thing, heat or disc warping. The stub axles DO flex relative to strut. Ie, a wide sticky semi tyre will try to "tuck under" when cornering, ie go into a more pisitive camber angle. The wheel can deflect by up to 5 mm relative to the strut. I know! With 5 mm clearance between tie rod end and rim lip, after a teack day, i discover the tierod end has galled alloy attached, and the rim lip has a very slight gouge out of it all way round. Static clearance was 5 mm! But i have now solved that problem! Quote Link to comment Share on other sites More sharing options...
d3c0y Posted August 26, 2014 Share Posted August 26, 2014 I have heard from a couple of sources that Wilwood calipers do flex a fair bit, which could account for the symptoms above? Quote Link to comment Share on other sites More sharing options...
luvemfast Posted August 26, 2014 Share Posted August 26, 2014 It's sounding like Wilwoods aren't all they're cracked up to be...... :-\ Quote Link to comment Share on other sites More sharing options...
RLY240 Posted August 26, 2014 Author Share Posted August 26, 2014 I'm running 260 hubs. Run-out isn't an issue as the knock back only occurs after cornering, 10kms country road drive and the pedal is still firm. Calliper flex shouldn't be an issue here, the calliper or mount will only move if something else (rotor) moves it first. Sure the Wilwoods are a cheap racing calliper though. In my mind it's either the hub moving on the bearing or the spindle flexing relative to the strut. I never has this issue with the previous setup (Hilux) which leads me to think that perhaps the Wilwoods do a worse job of recovering from knock back than factory style callipers. But I couldn't say why (seals perhaps?). There are a few ways to combat this (residual pressure, springs in the pistons, larger master etc) but I'd like to know what the actual problem is and short of having someone hanging under the car with a dial gauge I'm not sure what else I can do. Might try a go-pro under the guard somewhere... Appreciate the replies guys. Roger Quote Link to comment Share on other sites More sharing options...
PZG302 Posted August 26, 2014 Share Posted August 26, 2014 Nope, they are a cheap caliper. If you really want to be disappointed at the quality, pull one apart to do a service on it. My old dynalites were basically pulled apart and checked every year or so as they didn't have piston seals so the pistons and bores had to be checked regularly. The quality of the finish on the calipers left a lot to be desired. Most wilwoods don't have piston seals in them so that could be main culprit as the pistons arent pushed back by the seals. Having said that, they are a cheap caliper, and for the price point do a good job. As has been said above, the standard mounts may also help in letting the calipers flex. On my old race car I had custom mounts made out of heavy steel to try to limit any flex, it seemed to work OK, but the pedal always felt long, even though the brakes worked brilliantly once I got the pad compound sorted. Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 26, 2014 Share Posted August 26, 2014 Got some alloy full backed AP race calipers on the front of the 120Y and the RX7 Sports Sedan ( did i mention that's for sale!) They all have a fairly strong spring in behind the piston, along with a square section piston seal, that sits in a groove in the caliper. They certainly stop pad knock off! Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted August 27, 2014 Share Posted August 27, 2014 ... Most wilwoods don't have piston seals in them ... Can you elaborate on that? Is there some diaphragm arrangement? http://www.autolifers.com/wilwood-bbk-rebuild/ Quote Link to comment Share on other sites More sharing options...
PZG302 Posted August 27, 2014 Share Posted August 27, 2014 The racing calipers don't have any seals on the pistons. Do something silly like mash the brake pedal with the pads out and you end up with four pistons on the ground and a lot of fluid on the floor. Basically the pistons just sit in the caliper bore. From memory, and it has been a long time since I pulled them apart, there was a rubber o ring to seal the piston against the bore and that was it. no dust boots or proper seals to keep grit and crap out of the calipers. Also remember, my calipers were around 15 years old and the original dynaltes, so I don't know how much they have changed from what I was using. Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted August 27, 2014 Share Posted August 27, 2014 Okay, so you are stating they don't have dust seals rather than they don't have O rings to seal the brake fluid. Dust seals would never force the pistons back but O rings can roll as the piston moves and their elasticity can then draw the piston back when the fluid pressure is released. However, this doesn't appear to be the issue here as it only occurs after cornering. It might be worthwhile fitting springs behind the pistons (they are available in various tensions) to overcome what appears to flex somewhere in the calliper or mounting. Quote Link to comment Share on other sites More sharing options...
RLY240 Posted August 27, 2014 Author Share Posted August 27, 2014 In talking to people about this today I was told about a "stub axle stiffener" that was available from Otomoto or AZC or similar. Basically a bearing spacer sandwiched between the inner and outer bearings inside the hub similar to how the rear hubs are done. I can't find anything from either of those companies so has anyone else seen this sort of setup on a Zed? Roger Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted August 27, 2014 Share Posted August 27, 2014 Here you go. http://www.msfracingcomponents.com.au/stubstiffenerbearingspacers/ If you get a set let's know how you got on, I'd be very interested. Thanks Quote Link to comment Share on other sites More sharing options...
Riceburner Posted August 27, 2014 Share Posted August 27, 2014 Maybe with a group buy we could get them a little cheaper? I'm keen for a set too Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 27, 2014 Share Posted August 27, 2014 I use those on the stubs on the race cars, does take a bit of fiddling to get bearing preload correct. On the Z, have also had welded onto back of stub mount plate to strut tube, a pair of wedges/plates, to more strongly "tie" the strut tube to the front spindle/axle mount plate thingy. Plates are 2mm thick, approx 30mm x 40mm shaped to suit the area, welded well! Quote Link to comment Share on other sites More sharing options...
Gordo Posted August 27, 2014 Share Posted August 27, 2014 I'd like to see someone prove this works before I'd go down this path. I have wielded in a gusset, triangular pice of steel in between the strut tube and stub axel to stop flexing. Quote Link to comment Share on other sites More sharing options...
Gordo Posted August 27, 2014 Share Posted August 27, 2014 Great minds think alike. lol Quote Link to comment Share on other sites More sharing options...
RLY240 Posted August 27, 2014 Author Share Posted August 27, 2014 Here you go. http://www.msfracingcomponents.com.au/stubstiffenerbearingspacers/ If you get a set let's know how you got on, I'd be very interested. Thanks Thanks Peter, ordered these today so will see how they go. Roger Quote Link to comment Share on other sites More sharing options...
PeterAllen Posted August 27, 2014 Share Posted August 27, 2014 I use those on the stubs on the race cars, does take a bit of fiddling to get bearing preload correct. On the Z, have also had welded onto back of stub mount plate to strut tube, a pair of wedges/plates, to more strongly "tie" the strut tube to the front spindle/axle mount plate thingy. Plates are 2mm thick, approx 30mm x 40mm shaped to suit the area, welded well! I can see where tying the strut tube to the large flange face of the stub axle may be effective in holding camber as the whole of the stub axle moves under load, but, the issue we are trying to address is the presumed flex of the axle shaft either itself or relative to the mounting points of the brake calliper. That is where I see stub stiffeners coming in to play. I'm really concerned about this as my wire wheels are 16" dia and weigh a bloody tonne. Quote Link to comment Share on other sites More sharing options...
dat2kman Posted August 27, 2014 Share Posted August 27, 2014 Can take some pics of a stub axle, with a crack, on the topside, and another stub, snapped off, just down from the inner bearing. Thats why i then machined up the bearing spacers, but i stepped mine and gave them a biggere surface area on which the stock inner races shoulder up to, compared to MSF's ones. Re flex, se my post above, about the wheel rim lip deflecting the 5mm to then grind itself on the tie rod end. Was kinda WTF, when saw that. SWR has been wedging and plating the struts for 35 years! Quote Link to comment Share on other sites More sharing options...
chris240 Posted August 27, 2014 Share Posted August 27, 2014 Interesting that the ACT Govt RTA and local engineer have not accepted wilwoods on modified cars, because the lack of seal breaches the national guidelines for vehicle modifications, Ive read the sentence. We have the strictest RTA staff in the world down here ! Quote Link to comment Share on other sites More sharing options...
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