Wilwood Superlites pulling right and sometimes left

[z boy mn]

Hello everyone. The snow is on the ground in northern MN, so it's time to park the Z and get it ready for spring.

 

First on my list is this tricky brake problem. The previous owner purchased the Wilwood brake kit for both front and rear of my 240Z from Design Prodicts in CA, and while they were on the car, I've removed and checked them as he bought them a long time ago (1999) and the car sat until 2012 when I bought it. I've got about 7,000 miles on the car now, post the complete restoration.

 

But, they do this annoying thing...sometimes, more in early part of the season, they pull mostly right but sometimes left when you step on the brakes. I've flushed the system and bled the lines a couple times now, and I've inspected the calipers. They look...well...brand new. The lines were replaced, too, as was the master cylinder. It doesn't happen every time...just now and then. The brake pedal is firm. My plan this winter was to bleed the lines again...and again...thinking maybe there's air trapped somewhere, but I'm new to this...so...

 

I was also thinking that maybe the calipers were "sticking," but these brakes are so simple I don't see how that could be the case. It's just four pistons. Could they need to be lubricated somehow (but aren't they lubricated with brake fluid)? Nothing leaks, so I'm thinking the seals are fine. Maybe the pads themselves are sticking somehow?

 

One thought...I also have a Wilwood proportioning valve...could that be the culprit? I've never understood how to adjust this, so right now it's just in the "middle" (it goes 10 turns left and right, so I've got it "set" at 5).

 

Anyway, I've read through the forums here but most of the posts are with stock brakes, sticky guide rails, etc. I had the car on the track last fall, and the brakes were amazing in terms of stopping the car, not over-heating, and absolutely no brake fade...it's just sometimes it'll surprise you! (I've learned just to grip the steering wheel really hard--which isn't much of solution, but this is the first car I've worked on so I'm not much of a mechanic yet either.)

 

Thoughts/comments/suggestions are welcome and greatly appreciated!

 

P.S. I've attached some photos of the front brakes when I painted them a couple years ago. Not sure the photo is helpful, but just in case...

[z boy mn]

One correction/addition. I found the receipt and they're Superlite II's in the front and Dynalite II's in the rear (both are 4-piston brakes).

[Patcon]

When you say inspected, does that mean you looked at them or took them off and disassembled them and inspected the piston bores?

[John Coffey]

You have aftermarket ball and socket TC rod mounts on the car.  Check them to make sure they are not worn or loose.

[z boy mn]

Thanks for the feedback....I can answer a few questions...

 

Charles, I took them off the car and looked them over carefully. I removed the pads and inspected everything I could see, but I didn't compeletly disassemble them. At that point, they had somewhere around 250 miles on them so they were basically brand new. Since then, I haven't noticed any leaks or changes, though the mileage has gone up.

 

John, I noticed the non-stock TC rods, too, and looked them over when I redid the suspension (adding progressive springs). They seemed adequate. Since that time, the car has been aligned professionally (using the specs you posted, I think), and it's continued to hold that alignment and feel stable on the road.

 

I called Design Pro in Huntington yesterday, and he's thinking I should try bleeding everything again. Maybe I didn't get both sides of the caliper bled properly, for example. He also suggested that if my pads are too hard, they may not be heating things up enough to work like they should as it seems to happen more when the car is cool...but not always.

[Patcon]

Well my first thought was corrosion in the bores from sitting with moisture in the system, but you won't be able to tell without disassembly...

[Zed Head]

I had a similar problem with stock calipers long ago and it was loose wheel bearings, and bad roads.  Depending on what side of the highway rut I was on the bearings would let the wheel ride up one rut or the other.  

 

After I fixed that problem, I was down to pulling only one way some times.  That was caused by an old caliper matched to a new one.  The pistons are pulled back in to the bore slightly by the elasticity of the seals.  I assume that my seals behaved differently.  Replaced the old caliper with a match for the new one and it's been fine.

 

The seals in your calipers are 16 years old if got the details right.  But loose parts, like those John Coffey suggested, or wheel bearings, are likely.

 

Here's some stuff on seals, just for entertainment - http://www.autozone.co.za/index.php/function-of-caliper-seals

[z boy mn]

Thanks for all your suggestions...I am finishing up my semester and will get the Z up on blocks as soon as it's over. I'll look for anything that's loose as well as disassemble the brakes and see if anything looks suspicious. I won't get to test it all out until the spring, but maybe if I do a careful job I can correct the problem for May!

[Pop's Z]

FWIW, I had those ball/socket TC rods on my car for about 10,000 miles. I replaced them with stock rubber bushings as there was a lot of uneven road surface feedback in the steering. It worked and the feedback went away. BUT what I found when I removed the ball/socket was the nylon pieces had big cracks in both units. I don't know if this might be your problem, but those are worth looking into.

 

Cheers, Mike

[Chickenman]

It certainly wouldn't hurt to rebuild the calipers as ZH mentioned.16 years is a long time ago, especially if they were sitting.

 

Buy new seals for all of the calipers.  While they may not be leaking, the seals may have lost some of their " elasticity " and may be allowing one side to drag on the rotor. It's a common problem with old seals. They are cheap and you can buy them direct from WilWood. Summit and Jegs also stock them.

 

You may also need to polish the bores due to corrosion. Even a slight amount bof corrosion in the bores will cause a pistoon to stick slightly. That will cause a pulling situation. Hand polish with " Crocus " cloth ( Also called: " Machinist cloth".  2,000 to 3,000 grit ) soaked in brake fluid. Hand polish the Caliper pistons as well with the same material and procedures.

 

If the rotors aren't brand new, get them turned so they are flat and have a good surface finish. Modern pads are sensitive to pad deposits on the rotors. If you change pads brands you should surface the rotors, unless the pads have a special " break-in coating " that will scour off the old pad deposits off of the rotors. Semi-metallic pads aren't sensitive to this, but a lot of " Ceramic " pads and Carbon or Polymatrix pads are. 

 

What pads do you have in there? I'll tell you right now from experience that most of the WilWood " Street compounds aren't that great ". They do tend to grab right or left. Especially in the rain. 

 

 

Fortunately the Superlites and Dynalights have a huge selection of pads to choose from. Hawk HPS compound is a decent Hi Performance street pad. Suitable for any street use and Autocross. PFC also makes a good Hi Perf street pad for these calipers.

 

If you run Track days you should go with a dedicated set of proper Race pads and a spare set of rotors bedded to those specific pads.

Edited December 10, 2015 by Chickenman

[z boy mn]

Hey Chickenman and Mike--great suggestions. I'd much rather work on things now when the car is parked so I can drive it when the sun shines...and there's no snow on the ground.

I don't have it on blocks yet, but if the seals aren't expensive it makes sense to replace them. Don at Design Pro was very helpful on the phone, so I'll probably order them from him as I like working with people who are helpful. When I pull the pads, he also said there might be some kind of number on the back and we could look up what they are for a compound. I do notice that in the rain it doesn't brake that well at all, so maybe another kind of pad would work better for my application.

Also, I'll look for corrosion and make sure everything is clean when it goes back together. I've seen a video about replacing the seals, and it doesn't look like I can mess it up too badly if I take my time.

I didn't think about the surface of the rotors making a difference, but that also makes sense. If I replace the pads, I'll definitely get them resurfaced.

I had the TC arms apart not that long ago, but to your point, Mike, I'll see if there are any broken pieces. I'd like to replace them with something that allows me to adjust caster anyway...

It sounds like the adjustable proportioning valve isn't a likely suspect in all of this as it hasn't come up yet in your comments. But, I was wondering now if maybe I have it set properly or how to set it. With smaller calipers in the back and larger tires, it doesn't seem likely I'd be able to lock up the rears anyway, so I should probably have as much pressure heading to the rears as possible. But...is that turned all the way "up" or all the way "down?" I'll have to check out more YouTube videos I think!

[Patcon]

When you rebuild them do one side at a time. That way you have a complete unit for reference.

 

It is my understanding you want the fronts to lock before the rears to prevent snap spins. Typically the more you thread it in, the less pressure to the rear. May or may not work that way...I have heard of getting on a dirt or gravel road and adjusting your brake bias there as you don't have to be going very fast to lock up the wheels to determine your bias.