Dan Martinic

While changing front rotors, I had to pretty much crack one of them to get it off. The hub had major build-up of corrosion. I didn't realize they were aluminum or that they even had these bumps / raised mating surfaces all around--it was that bad looking to be unrecognizable (and I don't even remember last time I changed these rotors--maybe once when I first got the car!). I took a small grinding wheel and cleaned away, not realizing just how much material I was taking off. The result is I've made a mess: the hub's edge surface is now the opposite of smooth and round. It's full of valleys... bumps.. and barely-recognizable.

I did the other side next and of course it was fine, which is how I realized what they are supposed to be like.

Anyway... how important is it to have the hub circumference in good shape (literally ie. smooth & round)? If the rotor's inner circumference surface (sides of the "hat") no longer contacts the hub fully--which I'm sure it doesn't as I ground down most of those raised pieces--what can happen? The face of the hub and all the studs are fine and the rotor + wheel bolt up as usual.

A quick search shows finding one good hub might not be easy. Lart has a pair of good ones for 200USD plus almost 70USD to ship up here.. not crazy money but after all my recent unexpected work, I need to stop the bleeding a bit!

bonus12

How bad?
I can't 100% tell but it sounds like the surface you are talking about is one that spins. If that's true, any unevenness will spin unevenly and take its toll.. Do you feel any new vibration at highway speed?

Dan Martinic

Yes: there is some vibration at speed, something I've always attributed to wheel balance or warped (old) rotors. Though addressing those two has lessened it considerably, some vibration remains. I guess I know why now lol

V2Rocket

do the rotors have the little flat-head screw that holds it to the hub?

i dont think the rotors are so much hub-centric like a wheel would be. with the little screw(s) in place there's really only 1 way for them to sit on the hub (the flathead countersink self-centers).

Dan Martinic

Yes, rotors have the little centering screws; I figure safety-wise, all is good. Question is would an irregular hub edge cause problems or vibration....

V2Rocket

you mean as if it were out of balance because of removed material?
technically yes it will matter but probably a small amount, it's not a very large diameter and not a lot of mass removed.

do they make tire balancers that work with the tire on the car? if so that might be able to zero it out.

FrenchToast

Maybe I am wrong, but I think the outer milled nubs are for balancing.

IMO, with corrosion or material removal I would toss it. The hubs are sketchy enough normally.

I would also have them both crack tested.

Dan Martinic

The raised parts along the edge are for balancing? I'm not sure what you mean; they seem to be evenly spaced as if they are there so the rotor sits on them instead of the entire edge surface. All the pics of these that I've seen appear to have the same raised nubs. In any case, my one hub is now pretty rough along this edge... doesn't seem right. I'm currently in the middle of securing replacements

FrenchToast

I always thought they were milled down to the required dimension for rotor hat ID, then they milled further to correct the balance of the piece.

Your theory makes more sense, I never thought of it that way. Now that I think about it, the center bore of the rotor hat is far larger than the center boss on the hub? So there is no other way to center the rotor.

GPA951s

Dan, i have a set somewhere if you really need one or two.. If you can pick then up at Mantis I can get them at least that far without shipping because Earnie comes down here all the time to pick up stuff..

Post a Pic of where the damage is..

Dan Martinic

Hey Thanks!! But.. I already ordered a set from Lart. I sent payment so I guess it would be a bonehead move to try and cancel now

Even better: I'm currently in Windsor and just realized I could have had then shipped across the border here for free instead of the 67 USD I paid extra for shipping to Toronto oh jezzz

Appreciate the offer though

Say... I called Mantis the other day asking about an alignment... was surprised to hear the cost... I can understand the initial fee (240) but the actual cost is double that? Something about unfreezing the rear end? Never had a shop quote me double to loosen some potentially tough bolts. I guess they are too busy [EDIT: I have spoken with the owner Ernie and it appears there is a misunderstanding regarding this on my part]

Dan Martinic

When I get back, I'll post pics. When trying to remove the old rotor on the one side using bolts in the threaded holes made for the purpose, the rotor just cracked and broke where the bolts were. That's how corroded it was to the hub

GPA951s

When you need something you should check with me... I really do have a ton of parts... I think I have 3 or 4 Sets of turbo Headers... Cruse control stuff 2 extra sets of airbags for late cars.. ... Ive been Gathering parts for 20 years.. One of these years im gonna take it all to Hershey .... but its so nice to have so many spares... Im actually going to build out all the engines that I have.. I just sold one as a matter of fact to a club racer...

Dan Martinic

Good to know! Esp since we're practically neighbours lol

We will talk cruise control: I don't have it... yet I'm planning some long trips in the future.. cross-country... that dangling plug beside my feet suggests it shouldn't be too hard to equip. At least I hope not!

GPA951s

Well, Ill let you know when Brion and I are setting our cars up. We will have to do an alignment on both of them at my shop because we are changing engines in both cars.. I have to take out my standalone and sleeved engine and put it all back to a fresh "stock" setup for clubracing... . When I change engines I drop them out the bottom with the lift so I always have to re-align... It helps that Brion owns then hubstands company... So alighments are super ez.... So Start Soaking your bolts now with penetrating oil...