wilwood brake kit, rotors warping, what's wrong?
 

I bought this setup used from another forum member. IT's a wilwood 6 piston billet superlight caliper with (from what I can tell) SV or GT directional vane rotors, and EBC green pads, the pads are basically new and have only a couple thousand miles of use from what I can see.

They had moderate heat markings on them when I first got them, resembling a flywheel that's been hot. No cracking though, and upon a testdrive, they were vibration free. The heat marks looked bad though, and I suspected they might not have been bedded in properly.

I wound up taking them off because I had an offer to buy them, but that didnt work out. While they were off, I sent them out to be machined. The guy doing the work, an acquiaintance of mine, recommended we try surface grinding them for greater accuracy than turning. I took his word and told him to go ahead, it was after all free. They came back looking great, but you could faintly see the pattern of surface grinding.

I put them on and started the bedding procedure as described on wilwood's site. Almost immediately I noticed the rotors began to wobble indicating warpage, they most certainly had not been hot. I hadn't driven 10 minutes but by the time I got back and shut it off, the rotors were smoking lightly even though I hadn't done anything short of what you'd do in normal 40mph stop and go traffic. I also immediately noticed the heat marks had returned.

What am I doing wrong here? IS this a problem inherent to this set of rotors, or are they just "*that* sensitive? I've never before had a problem like this. I'm thinking that surface grinding is not the way to go with these, and will probably try and get them turned instead.

I have had the same kind of problem as you; after getting my Wilwood rotors turned, then they were worse than to begin with. My problem turned out to be that the people with the brake lathe did not turn the rotors true to the same axis that the rotors spin on my car. The problem turned out to be the adapters they put between my hub and their brake lathe shaft; their lathe adapters would permit them to set the rotors up with a little wobble. When they turned the rotors on their crooked setup, then they would end up crooked on my car and pulse and shake the car bad.

My solution was to put the rotor on my car spindle, and measure it with my dial indicator. Then I slowly turn the rotor, and write on the face of the rotor the high spot in thousands of and inch, and the low spot. Then I take the rotor to a brake lathe man who is patient and understanding, and we set the rotor up on his lathe until we duplicate the same runout that the rotor has on my race car. Only after it is setup properly, then do we turn the rotors down with the lathe. This method solved my Wilwood brake rotor problems on my RX-7 road racer.

Was the surface grinder a rotational one? Or a 2 axis planar type? You can only use the rotational/rotary ones. Else you would suffer the same problem as speedturn about not having the face orthogonal to the axis that the hub spins on.

Yep; the surface grinding is what ruined them. Proof again that anything can be done incorrectly.

Im pretty sure it was not a rotational grinder, as the surface marks appear like ))))))) across the entire rotor. When I got them back I though it was odd that he chose to do it that way too, but I'm not the machinist, he is.

Im going to use some different guys this time, and hopefully get it right. IF not, I guess I'll be buying a new set of 13" rotors.

Thanks for the help guys.

If you can turn them, then i would recomend using an on the car lathe. It helps eliminate runout problems that might cause vibration problems in the future. Basicially, as speedturn found out, all brake lathes have run out, and every car hub has run out. If you add the two together then you get quite a lot of runout, depending on the car of course. On an on the car lathe, it measures the runout with the rotor on the car, adjusts the brake lathe so that you have minimum runout, usually around .005" if i remember correctly, then resurfaces them. It is by far the best way to resurface a rotor.

These rotors are not that expensive anymore. Personally I have found that the turning just doesn't work. I buy new rotors and I buy the heavier models(these will resist warping) which for some reason are the cheaper models. I don't know what the turning costs in your area, but the new rotor are about $33 to $65 depending on size and mounting pattern. I would buy a new set and forget the turning. If you spend $10-$20 a rotor and a couple hours to get them turned and if you have to do this more than once it is no bargain. Stockcar Products even has free shipping right now on rotors. http://www.stockcarproducts.com/brakes14.htm

Lol, i work at a shop that does a lot of brake work. I would say one out of every ten rotors that we receive we end up turning anyways. Why you might ask? Well, there is no telling how long the rotors have been sitting and where they were located in the stack of rotors: for instance, they might have been sitting at the bottom of the stack with ten other rotors stacked on top of them, maybe even more. With all that weight on them the will warp over time and cause a vibration when installed. Alot of times we will turn a new rotor just to make sure they are true just to eliminate waranty work down the road.

It could just be pad transfer. I've had very similary experiences many time and that's what it was. Even if you follow the proper procedure it's common for some types of rotors and pads to transfer a lot of material initial and get a vibration. Try driving it around and using the brakes a lot (or running it on the track a a bit) and see if that helps.

After a few days of easy braking with light vibration and heat marks, I thought the same thing. So I took it up to 120 and did a 120-50 brake over the course of about 10 seconds then cruised a 1/4 mile and came to a stop from 50-0 over the course of about 5 seconds, neither was all that harsh of a stop. The wheel vibrated badly during both and when I stopped a shitload of smoke was coming from the front brakes, I thought the damn car was on fire. So it's only going to get worse, I'll probably take them off before I drive the car anymore so the rotors don't sustain any permanent damage.

I have experimented with Wilwood and other brands on brake lathes with bad results. I use to race NASCAR Late Model Stock Cars and crew on a Craftsman Truck and we tried everything to reuse the rotors once they were taken off the cars. The manufacture process does not really allow for re-machining of the surface. We had catastrophic failures will both options ending up with replacing hubs and spindles.

I suggest throwing them away and but new ones. Go with a less aggressive pad for the street since you have a larger brake surface to reduce the heat build up and wear on the rotor surface. A ggressive pad isn't always the best answer.

Having a rotor break in half would be a bad thing to happen!

EBC greens are hardly a really agressive pad, the worst thing about them is a bit more dusting and squealing. I dont think it's the pads causing the problem.

Definitely a grinding problem. On top of that you have to remember that since you have 6-piston calipers, any warpage will be more noticable since the pad is pushed to the rotor more evenly.

I have never had a problem resurfacing powerslot rotors, stock rotors, or aftermarket replacements. The EBC pads are definitely not at all aggressive. The machinist is the problem for sure. As an aside, I had a problem with a set of 4 rotors turned by a machinist, as opposed to an automotive shop, not one was true,these were "flycut", took them to Les Schwab, and now they are perfect. Russ, I have never heard of a problem with resurfacing rotors as a rule, not Brembo, Stoptech, Wilwood, Baer, or the rotors previously mentioned, what brand of rotors are you refering to? I am sure most of those are not the OEM, but you see my point. Carl

Russ is very correct and the OEM type rotors are definately a different construction and as a general rule the stock car crowd up and down the pit lane change rotors and don't resurface. I have resurfaced thousands of OEM type rotors in my career with good results, but each time I have tried it with the two piece rotors they have had the problems RotaryResurrection is experiencing. I turned the rotors myself and they were true as possible and the vibration developed immediately both times. I changed the rotors to new units, kept the pads, and no problems. I use a set of pads and rotors about every two years of racing, so on a street car these should last a lifetime. spend $60 and solve the problem. I also like the Wilwood pads over many other more popular brands. I have never used EBC on a car, they did work well for a couple motorcyles I owned.

Buy new and cryogenically treat them immediately.

I ran my 1982 12A RX-7 on:-

10.25" x 1"vented discs - 4 port AP Racing solid back calipers
Mintex M191/1191, Ferodo DS11, then PF Blues
Ford Capri standard disks 300miles £80 ($100)
AP racing discs 1000 miles £300 ($400)
Ford Capri + cryo £80+£50 ($200) 2 seasons (2000miles)

no cracks no warping

My response to the pads was generic in terms. Wasn't saying the pad you were using was aggressive. Contact Wilwood direct and talk to a tech about surfacing of a rotor. They can give you all the technical info on them. I was just telling you about our experiences trying to resurface Wilwood and AP rotors. Generally race car rotors are a throw away item and are not meant to be resurfaced.