Just put the rebuilt trailing arms on the car and measured the runout. One side was .010 and the other .012 !! So I'm figuring on getting some shims. Rockauto.com has them for $16 each. They are for .003 and .006. Can I use two?

 

OK, I think I have answered my own question. After doing a search, which I probably should have done first. I am going to do the 'beer can' approach and make my own. God knows I have plenty of those!

 

Ask Summit tech line? They are made to correct runout, not just flat shims?

If you search our archives, there are wedge style available.

 

Thought for you, if you have not done so already. I would try indexing the rotor on a different set of lug nut studs and see if you get a better result. So, you check runout with the rotor in 5 different positions and use the lowest runout numbers to shim from there if needed.

BTW I made and used my own shims out of steel shim stock and it worked just fine.

Hope this helps and good luck!

 

On the rears at least, you can't index them because of the parking brake adjustment holes. I think I will try and get some steel shim stock.

 

I went to a hobby store and got thin sheet brass.

 

Good point and forgot that, oh well.

 

Don't forget to torque the wheel nuts evenly (I ran normal wheel nuts backwards so the taper doesn't interfere) and you shouldn't just shim the high spot alone, you should also shim the next two studs the lesser amount as well, assuming the rotor is flat of course.

You can drill a hole through the thin material nicely (and safely) by clamping the aluminum between two pieces of wood and drill through the whole thing
M

 

I indexed mine and used the shims. I think it is more important to get rotors to run true than to worry about adjusting my emergency brake. I like the idea of the variable thickness correction shims rather than the individual wheel stud shims.

 

I bought an assortment of brass shim stock from a hobby store chain called Lee Valley. It's difficult stuff to get here in Atlantic Canada for some reason. I also used a sharpened leather hole punch, a ball peen hammer, and an anvil to create the lug holes. Worked well, but Mooser's method is likely better. I used a little bit of chassis grease to hold the shim in place on the spindle (very thin). It's very important to torque the lug nuts evenly as suggested above.

The job can be quite effective. Good luck.

 

A Gasket Punch works for making the Holes in the Shim Stock as well.

 

I used tin foil from the kitchen, found the least runout spot to index the rotor on the hub, sprayed it with paint as a witness mark, and took out the rest of the runout by shimming with tin foil layers as needed, say it took just one layer, put it under the stud and forget about it, takes more than that, make sure to put one layer less under the adjacent studs to alleviate any stress....been that way for years now....

 

all good replies - thanks

 

OK, so to follow up on this, I went ahead and ordered the rotor shims from Summit. I got two of the .003 and two of the .006 ones. I ended up using both 006 on one side and both 003 on the other side. It says to only use one but I am going ahead anyway. I got both dialed in now to about .002 runout.














As you can see I just cut 'V' notches in them where the parking brake adjustment holes are and this worked fine.
Jim

 

If you put that style shim as shown in the photo ( .006 ) doesn't that just shim the entire rotor out .006.

I thought the idea was to prevent wobble by shimming one or 2 studs ???

Is the dial indicator something I can buy locally and which one would I need ?

I need to do this soon so any help is appreciated,

Frank

 

The shims are tapered from one side to the other. (notch in the center marks either the high or low spot depending on the brand.)

So if you have a .006" runout you buy the .006 shim and orient it to cancel out the wobble.

Straight thickness shims work when you place them over some of the area of the rotor like your thinking

The indicators can be bought fairly cheaply at someplace like harbor freight. Good enough for how much you'll need it.

M

 

Great, thanks for the info - makes sense now -
I appreciate it !

 

jim-81,

Did you rebuild the trailing arms yourself? If not, who did them?

 

Yes, I did them.

 

Interesting observation here. The shims aren't actually .003 or .006 thicker on one side. They are engineered to make up the difference at a particular distance on specific sized rotor. So, if you buy them, you won't see the specified difference in the shim itself. I think it was about 1/2 for our Corvette rotors.
A good product that works well.