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Disc Runout
Posted: Fri Jun 22, 2007 12:13 pm
by tetlow
I have been having a pulsing hissing sound coming from the passenger front wheel.
I have stripped the unit down and found a lot of disc run out. They are pretty new slotted and dimpled discs.
After repositioning the disc 90deg I have reduced the runout to about 6 thou or 0.15mm. It this good enough?
If not is it possible to get the discs ground?
Regards
Dave
Re: Disc Runout
Posted: Fri Jun 22, 2007 2:19 pm
by sidecar
tetlow wrote:I have been having a pulsing hissing sound coming from the passenger front wheel.
I have stripped the unit down and found a lot of disc run out. They are pretty new slotted and dimpled discs.
After repositioning the disc 90deg I have reduced the runout to about 6 thou or 0.15mm. It this good enough?
If not is it possible to get the discs ground?
Regards
Dave
6 thou sounds pretty good to me. I guess the "proof is in the pudding"...go for a spin
Posted: Fri Jun 22, 2007 3:01 pm
by tetlow
Can't. No front or rear suspension, and no motor.
Can't even pressurise the brakes as not connected.
Posted: Fri Jun 22, 2007 3:43 pm
by kiwicar
sounds about right for now then!
Mike
Posted: Fri Jun 22, 2007 4:01 pm
by tetlow
I am in the process of rebuilding the front and rear suspension, removing all the Koni shocks and replacing with standard ones, and replacing the gear box with a 5 speed jobbie.
I do not want to rebuild the front hub units only to have to strip them again!!
Posted: Fri Jun 22, 2007 4:32 pm
by sidecar
tetlow wrote:I am in the process of rebuilding the front and rear suspension, removing all the Koni shocks and replacing with standard ones, and replacing the gear box with a 5 speed jobbie.
I do not want to rebuild the front hub units only to have to strip them again!!
I guess the only way to be sure if you can't drive the car is to check out the runout limit in the manual.
I used to race an F1 sidecar and spent hours moving disks round on splined shafts to get the lowest run out figure. I would have been happy with 6 thou.
Regards,
Pete
Posted: Fri Jun 22, 2007 4:58 pm
by ian.stewart
Somewhere in my distant memory, 0.002" is the max runout for a disc.
may be wrong, I have been before,
Ian
Posted: Fri Jun 22, 2007 8:01 pm
by tetlow
Iv'e dug out an old B manual and found the lowest runout is 0.003", so it looks like a regrind.
Thanks y'all.
Dave
Posted: Sat Jun 23, 2007 12:12 am
by katanaman
An often overlooked part is the hubs themselves. There are quite a few cars out there that can and do warp the hubs so give them a good check over as well.
Posted: Mon Jun 25, 2007 1:04 pm
by davemgb
Before dashing off to get the discs ground check the bearing end float.
Are you getting some of that 6 thou from the bearing movement?
I suggest removing the shims from the bearing pack and tighten the hub nut to about 10 lbft then check the run out on the disc.
Dave
Posted: Mon Jun 25, 2007 8:15 pm
by tetlow
Thanks Dave.
I had adjusted the endfloat to about zero with the shims.
I have checked all mating surfaces for burs etc but all seems OK. The hubs are nearly new.
I bit the bullet this morning and the discs are in for grinding at £12 each, which thought was not too bad.
I will update when I refit them.
Cheers
Dave.
Posted: Thu Jun 28, 2007 1:21 am
by Sondar
Guess the other thing is to make sure that they're seated flush against the hub / disk bell.
Posted: Thu Jun 28, 2007 8:14 am
by tetlow
Guess what.
Just got discs back. Look great. Same problem as before.
I checked hubs and as per katanaman said
they seem to be distorted.
The hubs rotate true but the lip that the discs bolt to goes up and down.
I have checked the surface and it seems OK, i.e. no lumps etc.
I will try this morning to see if my local engineers can true the hubs.
At least I know the discs are good now.
Dave