Front brake disk scraping on caliper during right turns

[billmoore42]

I am wondering if anyone else has had this problem. My 67 Series 3 has a caliper on the passenger front side that is not centered on the brake disk. The result is when the brakes get hot, the parts swell a bit and the metal body of the caliper scapes on the outside of the brake disk. If the gap was more even on both sides, I am sure this scaping would not occur. The hub bearing is smooth and has no play, and the runout is within spec.

I can only think of machining down the mounting face of the caliper to fix this, as adding shims between the caliper and the caliper mounting plate would only worsen the gap. I have owned the car five years, so who knows if the caliper is original or an old rebuild. Any insight would be appreciated!

[alan.barker]

Maybe caliper mounting plate is bent or wrongly fitted. Bent from accident in the past.
Alan

[billmoore42]

Alan, thanks, I will check this out.

[joe7]

If you look at the gaps on the right pad retaining pins, top to bottom, there is a difference in the gaps. They appear to be skewed, the top gap is wider than the bottom gap. Also, looking at the threaded hub as a reference point, the entire caliper seems to be titled to the downside to the left. I think Alan's suggestion is correct.

[MACCA.GLM]

Hi
Check the wheel bearing adjustment. too loose will cause that problem
Regards
G

[2cams70]

It has new discs. One of the things I would check would be whether the reproduction discs are dimensionally correct as per original. Don’t machine the caliper. If original it was designed by people smarter than you or I. There is something outside of spec. and you need to identify the root cause.

[Craven]

If you still have the old pads check for evenness of wear, a taper in thickness may give a guide.

[alan.barker]

Have you checked runout of Disc with a Dti
Alan

[MACCA.GLM]

Check the bearings are seated properly in the hub shoulders causing the disc hub assembly to be out of position
Cheers
G

[billmoore42]

The runout of the scraping disk is .003" which is more than the drivers side front disk which has a runout of .001".
I think this is within spec.

The weird thing is this only happened recently after a vigorous hot hour drive on twisty roads (90 degrees F) and lots of downhill braking to heat up the rotors. I even felt the brakes fade a bit during the end of the run (and then the scraping noise on left turns began).

The disks and calipers were fine and not making noise for two months before this hot drive. Then again, I have not really rung the car out since the rotor replacment 2 months ago. The scoring is pretty much even all along the outside edge, and I noticed scoring on the inside of the brake caliper to match this outside edge. Seeing this, I figured the best move was to machine a little material off the inside of the caliper but now I am not so sure.

The wheel bearing feel completely smooth and there is no play when I grab the rotor and try to move it back and forth. I think I might try tightening the axle nut one stop as the next step, as the rotor only scrapes on left turns, and makes no noise going straight or on right turns.

These are new Spitfire disks from Moss which as I said earlier were fine for 2 months on the car before the hour drive in hot weather. Perhaps having the disks turned to thin them a bit would fix this? Thanks for all your comments and help.

[2cams70]

Don’t try and rock just the disc. Put the wheel back on and try and rock the whole assembly. Having the wheel on will give you more leverage and greater ability to check for play between disc and stub axle.

[2cams70]

Just looking further at the pictures. Something is really odd with your set up. The disc is clearly offset relative to the centre point of the caliper and also the clearance groove for the disc in the caliper is offset. I can’t say whether this situation is standard or not for an Elan (perhaps others can) but intuitively it looks wrong. Perhaps someone in the past has had a fiddle thinking they could improve things. Maybe measure the front track of the vehicle and see if it matches specifications. If it’s wider than standard you need to dig further to identify what may have been changed.

[Sadbrewer]

Don't machine the caliper...the problem is elsewhere.

[AshleyPark]

You may have a seized piston on one side of the caliper that's brought about the offset.

[MACCA.GLM]

Have you checked the offset of the disc where bolted to the hub is the same as the original disc. If it’s bigger that’s your problem
Where did you obtain the discs from as they may have been m/c incorrect