Rotor runout.....

[GTR1999]

Fact is shimming does work, if done correctly. I just posted about this on DC and NAPA sells overpriced shims just for this purpose for many car applications.

Fact #2- front hubs can be trued up by any experienced auto-machine shop once the rotor is secured to the hub. Since many front rotors rarely need to be separated from the hubs they can be turned as they did 40 years ago as one. They run on the lathe by the bearing races so to dress them keeps them concentric. Rear rotors are a bit different and most times the rotor and spindle are no longer matched and runout can be excessive. Facing the spindle flange, with the spindle on center will help but it doesn't always work unless the rotor is matched to it. All you need is a 13" or larger lathe.

Fact#3 indexing the rotor may help with runout as some vendors recommend but you better spot and drill the PB adjusting holes or you won't get them adjusted.

New rotors "were" 1.250" thick with discard of 1.215" this covers total of both sides. Some of the new rotors now are coming in at 1.245" thick, probably the "rice" conversion factor. I'm not a fan of turning a chip unless it is really necessary and I have never had a problem with new, used, NOS rotors that I bolted on and dialed in using SS shims. The brakes are rock hard, the runout is under 0025" and the rotor is secured by bolts in addition to the lug nuts. I just did an original set of '66 arms, never apart. The rotors were 003 undersize 46 years later. I reconditioned the spindles and rotors without removing more then a few ten thousands at that. They dialed in without any need for shimming at 002 and 0005" runout.

But to each his own so all I can say is good luck with what ever method works for you.

 

[Kid Vette]

Fact is shimming does work, if done correctly. I just posted about this on DC and NAPA sells overpriced shims just for this purpose for many car applications.

You certainly have whole lot more experience than me. But it seems to me if you put a doughnut shim around 1 or 2 lug studs then you are tightening on air on 2 or 3 of the remaining studs. I know I'm probably be overly anal on this (I was a moldmaker for too many years I guess).

 

[GTR1999]

Fact is shimming does work, if done correctly. I just posted about this on DC and NAPA sells overpriced shims just for this purpose for many car applications.

You certainly have whole lot more experience than me. But it seems to me if you put a doughnut shim around 1 or 2 lug studs then you are tightening on air on 2 or 3 of the remaining studs. I know I'm probably be overly anal on this (I was a moldmaker for too many years I guess).

I agree that is what it may seem to be an "air gap" but in fact the rotor is tight and flat against the flange once the flat heads are torqued. If not, and I have seen some that guys do them and were loose, the rotor will have play in it.

One of the last checks I do to T/A's is to check the runout and final endplay to be sure there is no lateral play in them.

Tool & Die and Mold making were once highly regarded, saught after positions here in the Northeast. Finding experienced help is hard now that a lot of shops are closed and the work is gone. I worked with a lot of those guys and I'm sorry to say the experience this country is losing daily is not going to be replaced unless there is a vast change in mfg. I doubt it, at least not during my lifetime, as long as China is machining parts for cents on the dollar and Mexico is working for $1 hr.

 

[Kid Vette]

Tool & Die and Mold making were once highly regarded, saught after positions here in the Northeast. Finding experienced help is hard now that a lot of shops are closed and the work is gone. I worked with a lot of those guys and I'm sorry to say the experience this country is losing daily is not going to be replaced unless there is a vast change in mfg. I doubt it, at least not during my lifetime, as long as China is machining parts for cents on the dollar and Mexico is working for $1 hr.

I hear you, my business travels consist of trips to China and Mexico these days. I never would have guessed 35 years ago when I began my career that this is how I would finish it.

 

[010752]

Rear rotors are a bit different and most times the rotor and spindle are no longer matched and runout can be excessive. Facing the spindle flange, with the spindle on center will help but it doesn't always work unless the rotor is matched to it. All you need is a 13" or larger lathe.

Just wondering what mounting method you use to chuck up the rear axles. Some guys advertise their services, but it involves a lot more than just throwing it in a lathe.

As you well know, set up is the key, they have to be dialed in concentrically with the bearing surfaces, otherwise more harm would be done than good.
A lot of the threaded ends can be somewhat damaged due to pressing/banging bearings etc.
It would be ideal to be able to setup accurately between centers and use a dog drive like done originally.

 

[Doug]

Checked the front hub runout on mine the other day before fitting the new rotors and they both had .014 runout. Removed them and sent them out to get trued up, hope to get them back today. One of the hubs actually had quite a pronounced lip on the outer edge.


Doug

 

[GTR1999]

Rear rotors are a bit different and most times the rotor and spindle are no longer matched and runout can be excessive. Facing the spindle flange, with the spindle on center will help but it doesn't always work unless the rotor is matched to it. All you need is a 13" or larger lathe.

Just wondering what mounting method you use to chuck up the rear axles. Some guys advertise their services, but it involves a lot more than just throwing it in a lathe.

As you well know, set up is the key, they have to be dialed in concentrically with the bearing surfaces, otherwise more harm would be done than good.
A lot of the threaded ends can be somewhat damaged due to pressing/banging bearings etc.
It would be ideal to be able to setup accurately between centers and use a dog drive like done originally.

Well it depends on what I'm doing to determine setup. I rarely like to turn a spindle, most of them still have the factory rough facing on the flange and that is all you need.

You are 100% correct, if you just chuck it in a 3 jaw and then face it chances are you will create more runout then before.

When I polish the spindles I use a 3 jaw as they are fine for that purpose. They are good for general machining as well but to true a spindle flange I use a 4 jaw. For smaller diameters I use collets as they are better then 3 jaws and faster then 4 jaws.

I don't use faceplates but they can be used with a live center and dog. That is what we were first trained with on South Bend lathes in tech shool, 9th grade.

Again most corvette spindles do not need to be faced. They will not warp as some say but can be damaged by impact and then they should just be replaced with USA spindles, Toms' or Spencer Forge.

A good example is comparing a used GM spindle chucked in a 3 jaw to a new USA spindle in a 3 jaw. It will depend on the chuck, some will be tighter or looser then others. I used my small inside chuck I use for polishing on a Hardinge lathe for the test bed. The new Spencer Forge spindle had 009 runout in the flange, the GM 005" . Facing either one like that would have caused more runout issues when installing the rotor. I know the runout is in the chuck not the new spindle or even the old GM but it was fine to polish them with.

Some 3 jaws come with adjusting screw to dial them in like a 4 jaw as well.

Did I answer your question?

 

[010752]

Rear rotors are a bit different and most times the rotor and spindle are no longer matched and runout can be excessive. Facing the spindle flange, with the spindle on center will help but it doesn't always work unless the rotor is matched to it. All you need is a 13" or larger lathe.

Just wondering what mounting method you use to chuck up the rear axles. Some guys advertise their services, but it involves a lot more than just throwing it in a lathe.

As you well know, set up is the key, they have to be dialed in concentrically with the bearing surfaces, otherwise more harm would be done than good.
A lot of the threaded ends can be somewhat damaged due to pressing/banging bearings etc.
It would be ideal to be able to setup accurately between centers and use a dog drive like done originally.

Well it depends on what I'm doing to determine setup. I rarely like to turn a spindle, most of them still have the factory rough facing on the flange and that is all you need.

You are 100% correct, if you just chuck it in a 3 jaw and then face it chances are you will create more runout then before.

When I polish the spindles I use a 3 jaw as they are fine for that purpose. They are good for general machining as well but to true a spindle flange I use a 4 jaw. For smaller diameters I use collets as they are better then 3 jaws and faster then 4 jaws.

I don't use faceplates but they can be used with a live center and dog. That is what we were first trained with on South Bend lathes in tech shool, 9th grade.

Again most corvette spindles do not need to be faced. They will not warp as some say but can be damaged by impact and then they should just be replaced with USA spindles, Toms' or Spencer Forge.

A good example is comparing a used GM spindle chucked in a 3 jaw to a new USA spindle in a 3 jaw. It will depend on the chuck, some will be tighter or looser then others. I used my small inside chuck I use for polishing on a Hardinge lathe for the test bed. The new Spencer Forge spindle had 009 runout in the flange, the GM 005" . Facing either one like that would have caused more runout issues when installing the rotor. I know the runout is in the chuck not the new spindle or even the old GM but it was fine to polish them with.

Some 3 jaws come with adjusting screw to dial them in like a 4 jaw as well.

Did I answer your question?

Well, yes and no.
Thanks for the feedback, good to get other ideas.

By your response, I think you agree, they are just a big PITA.
I've got access to a full machine shop as you do, but I've been toying with the best AND easiest way to mount them.
I'm convinced that the only way to grab them is by both bearing race lands.
New, those axles held very tight tolerances for the races.

1st idea was to make a stepped set of jaws for 3 or 4 jaw chuck. One friend of mine's lathe is a huge cnc turning center, the type with the cuttings elevator out the back. He virtually made new jaws for every job (did a lot of engine piston turning, so he's pretty accurate.) His chucks are automatic and huge (over 1 ft dia). The problem would arise in doing less than 500 at a time. Sometimes you can remove and reinstall the jaws without retouching them, but not always, so too much possible setup time.
Sadly that idea is out the window, he recently died unexpectedly.

2nd idea was to have a stepped collet made, that would grab both the race lands at once. As you know, they mount easily and quickly in a collet chuck and they are also extremely accurate for removal and later install. Another friend has a bunch of Hardinge lathes that he does similar but smaller work on and he deals in specs at tenthousands for the military most of the time with his.

Two other friends have a variety of engine lathes, but frankly I wouldn't attempt it on a regular chuck, too hard to setup straight and way too time consuming for one cut. :banghead: Don't have the patience any more.

As long as the rear flanges aren't way, way off, to affect the rim mounting, probably the best method all round is to get the rotors cut on the car with a good machine. Lots of those Procuts around here.

 

[GTR1999]

It sounds like you have access to some nice machines. Maybe we are overthinking things here because most won't go to the extreme to dial in rotors.

You can chuck the spindle on the large bearing diameter and get them pretty good, the time in setup all depends on the condition of the chuck.

I have turned down my 72's spindle & rotor bolted together in the lathe. -0- runout, once I removed the rotor and placed it back on it was out 002" That is still good but not the -0- I had.

I still like dialing them in with shims if needed. You don't cut the rotor or spindle and I have them down to 0005" runout.

 

[Kid Vette]

Finally got some time to work on the Vette.



Even after having Mike (tracdogg2) refaced my front hubs, I still had excessive runout. So I got a couple of the BrakeAlign shims.





They are made from .025" stock with a taper ground on them. The ones to correct .003" runout have .0015" taper and the ones to correct .006" runout have .003" taper. In my case all the runout was on the hubs (the Wilwood rotors ran very true) so I just indicated the hubs and matched the thick part of the shim with the low spot on the rotor.





I now have about .0035" runout on one side and .0025" on the other when measuring about a 1/4" from the edge of the rotor. I'm calling that good enough.

 

[MYBAD79]

first time I see these tapered shims, nice idea..... but i prefer to hit the inside of the rotor (mating surface) and/or the spindle's surface with a sandpaper disc to remove .003" or whatever is needed to get the rotor to run true. I have a few 3" discs that mount to a drill, or a few 2" discs, even scotch brite discs that mount to air tools.... tedious work and obviously the wheel studs have to be removed to do this .... probably overkill but my personal preference...