What are you folks doing to center your upgraded brake rotors on the hubs? There is a little slop between the ID pilot of my Grand Am rotor hats and the hub pilot OD. What are you doing to hold concentricity of the rotor hat to the hub?

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RickN
White 88GT 5spd (<10K miles)
White 85GT (SC3800 Series II w/ AOD)
White 99 F250SD 7.3PSD 6spd
1956 Ford 860 Tractor w/ Freeman Loader
20Ft H&H Tilt Bed Trailer

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Never noticed that on my upgrade, how far does the rotor move on the studs?

Well, maybe it's not an issue but it can move around a little. I haven't measured it yet but it looks like it could be as much as .030" to .045" diametral difference between the hub pilot and the ID of the rotor hat.

I just measured it. .040 on a diameter. 62.5mm ID on the rotor hat and 61.5mm OD on the hub pilot.

[This message has been edited by RickN (edited 04-04-2010).]

I machined spacer rings to keep the rotors concentric with the hubs.

It's a little hard to machine spacer rings 0.5 mm thick without having them bend or break.

I'd suggest wrapping the hub with electrical tape.

I wondered about shim stock. There is a generous chamfer on the back edge of the rotor ID. Maybe fold the edge of the shim over, then roll it into a ring. The double thickness of the edge would keep the ring captured behind the rotor hat so that it would stay in place.

[This message has been edited by RickN (edited 04-04-2010).]

I'm not sure you'll be able to roll that folded over shim stock as easily and crimp-free as you think. I may be wrong. I personally think the vibrations from the rotor being off center by 0.040" will be negligible. I'd be willing to bet that most rotors don't fit much tighter on wheel flanges to enable them to be removed after three or four years of use in areas with winter conditions and salt use. I know I had to bring my Expedition to a garage after I failed to be able to remove the rear rotors for that very reason. They had to use a sledge hammer to free them up from the hub centering ring. I cringed at every blow, then got them to do an alignment.

So just throwing some rough approximate numbers out there for the sake of discussion:

Mass of brake disc:
5 kg
Worst case scenario distance of brake disc CG from rotational axis:
0.5mm

Mass of the smallest wheel balancing weight typically used:
10g
Distance of balancing weight from rotational axis on a typical wheel:
200 mm

I don't think it's a big deal.

quote Originally posted by Bloozberry: I'm not sure you'll be able to roll that folded over shim stock as easily and crimp-free as you think. I may be wrong. I personally think the vibrations from the rotor being off center by 0.040" will be negligible. I'd be willing to bet that most rotors don't fit much tighter on wheel flanges to enable them to be removed after three or four years of use in areas with winter conditions and salt use. I know I had to bring my Expedition to a garage after I failed to be able to remove the rear rotors for that very reason. They had to use a sledge hammer to free them up from the hub centering ring. I cringed at every blow, then got them to do an alignment.

It's actually less than .040", that number is the diametral difference. The radial difference and maximum off center would be half that or .020".

quote Originally posted by pmbrunelle: ...I don't think it's a big deal.

Well, you may be right. I should probably just drive it for a while and see if it is an issue.

[This message has been edited by RickN (edited 04-04-2010).]