Front rotor to caliper clearance

[ivan.wood]

I have just installed the front hubs on my 65 Elan and first off I had problems getting the hub adjusted properly until I discovered the replacement bearing set had felt seals that were glued into metal cup which prevented the hub from going all the way back, so either would not turn or had too much play. I Fixed that by buying 2 Nilos seals from DB. Yesterday I fitted the rebuilt calipers but noticed that the inside (frame side) clearance between the rotor and casting is significantly more than the outside (.032" and .075" }. I would have expected the rotor to be close to the middle. I bought the rotors from Spider Engineering a couple of years ago and was wondering if anyone else had this problem or is it normal?

[Chancer]

I think that might be a manifestation of not using the disc backplate, I dont have the manual in this country but recall that on a Caterham there are a pair of shim washers fitted somewhere to make up for the loss of thickness. Between the caliper mounting bracket and the upright IIRC.

[MarkDa]

Whilst equality is nice in reality the pistons won't know the difference and will operate perfectly well.

[ivan.wood]

I was wondering if it was designed that way since it is on the opposite side to the direct pressure input from the flexhose connection so it gives it a head start?

Just a passing thought with no scientific proof.

Ivan

[MarkDa]

The caliper doesn't move
So as long as the hub bearing is in adjustment the actual gap doesn't really matter.

[Chancer]

When the vehicles were new and if all the factory tolerances were respected and 50 years ago it wasn't such a priority then the disc would sit nominally in the centre, the build up of tolerances could move it either way but probably not visibly, I have a firm conviction based on a very poor memory that if the backplate is removed and shim washers are not used then there will be an offset.

With modern repro parts often the only requirement is that is should bear a passing resemblance to the original item enough for the buyer to accept it, tolerancing and QA are not a priority and often there will be no-one in the organisation capable of even understanding them and why they are important, modern machine tools in general will produce more accurate work than those of 50 years ago but it still needs checking and often they are just set up to copy a part without knowing the original dimensions and tolerances.

With a vehicle that may have had the upright, caliper, hub and definitely the disc replaced with modern pattern parts you should count your blessings that the rotor even turns let alone is centred.

That said I still think its lacking shim washers but dont have my manuals in this country to be sure and I cant even recall what fixing bolts the dust shield thickness would influence.

[rgh0]

There is a large stack of tolerances for many components that affect the centering of the disk in the caliper. If its a little off centre it is not surprising. If its so far off centre that it risks interference and you have confirmed assembly is all correct then you can adjust with shims.

Note: The Nilos inner seal spaces the inner bearing out by the thickness of the seal metal which should not be an issue

cheers
Rohan

[69S4]

My left hand front calliper just caught on the disc after I replaced the upright over the winter. I made up some 20 thou shims to recentre it and all was well. When I stripped it all down again a few weeks later (replacing shock absorbers) it didn't need the shims. I'd done about 20 miles in the interim.

[ivan.wood]

Thats interesting as I had not taken the Nilos seal into account but it makes sense for part of the problem. May be the Nilos seal does not seat fully back but after some driving loads on the hub it gets seated properlybut that would cause the bearing to loosen up?

Thnks

[ivan.wood]

So I have checked the the rotors and they appear to be the same as the originals except a few thou thinner due to wear. Tried re-seating the tappar bearing outer races but no movement. I have come to the conclusion it is the bearings I got from Spyder. They came in plain white boxes marked WBK1 so guess they are no name bearings rather than Timkin or SKF or other know quality brand. The only solution is going to be using shims as I don't want to have to press the shells out again.

Cheers

Ivan

[Chancer]

I would be very surprised if the bearings were really the cause, the tolerances on a bearing are many magnitudes finer than steering and suspension components and whilst there is no doubt some rubbish out there longevity wise if the outer and inner diameters were a correct fit its beyond belief that the thickness would be that far out.

[ivan.wood]

I would agree with you but either the inside outer bearing race was not pressed full home in the hub but I had that done by a local garage with a hydraulic press or the bearing itself is not going to the back flange of the stubb axle.

Anyway I have made some shim washers the have aleviated the problem.

Thanks

Ivan

[Craven]

Bearing inner backstop is the machined face of the upright.

[ivan.wood]

I tried with a tube onto the tapper bearing inner race and a fair sized hammer but it did not budge. Could not see behind the bearing because of the Nilos seal. Did not want to pull the bearing because of possible damage to bearing and Nilos seal.

I am just going with the shims for now

Ivan