Lotus Elan

Brake caliper mountings

PostPost by: fattogatto » Thu Nov 10, 2016 3:02 am

I have a 1967 S3 baby elan. Total rebuild on the brakes. While installing the recently rebuilt calipers on the front I notice there is no way the disc will fit centrally in the caliper opening. I have tightened down the axle nut to insure the hub is mounted square to the caliper mounting flange, then backed it off appropriately for preload. Still no luck. I would estimate there is a 10 degree difference between the disc edge and the caliper edge (if that makes any sense.) Since I may have easily mixed up the caliper halves when repainting, the question is - are these calipers matched (i.e. each half is matched with its brother) at the factory?

Everything blasted and painted. New bearings and hardware.

Any suggestions?

Thanks,
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PostPost by: RogerFrench » Thu Nov 10, 2016 4:23 am

They are matched, but I'm surprised at the extent of mismatch.
Is the disk 10deg askew relative to the calipers?
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PostPost by: fattogatto » Thu Nov 10, 2016 1:32 pm

Thanks. Yes, the disc seems about 10 degrees askew from the caliper. Same issue on both sides with both calipers. Mounting flanges on the calipers are not parallel with the mounting flanges on the calipers. I guess I'll have to dismantle the hub assemblies. I don't see how I could get the parts mis-assembled. Anything is possible.
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PostPost by: Elanman99 » Thu Nov 10, 2016 2:55 pm

Re your 67' Elan (nothing baby'ish about it) but I do not understand what is at an angle, to what?

The plane of the caliper lug mounting face is determined at manufacture by the machining of the components. Being steel and not rubber they are quite rigid and I don't see how assembling them could be done at an angle.

The stub axle fits in a tapered bore in the main body. Something would have to be very severely amiss to throw the disk axis off at 10 degrees, if it was bent I doubt that the bearings and hub would even assemble so your problem does not make sense.

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PostPost by: fattogatto » Thu Nov 10, 2016 3:17 pm

I agree Ian.
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PostPost by: billwill » Thu Nov 10, 2016 11:45 pm

Have you mounted the brake disk wrong way around?
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PostPost by: Briggs1 » Fri Nov 11, 2016 12:03 am

Roger,

out of curiosity- how do you know they are matched in production?

seems like a bad way to produce anything.

just curious,
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PostPost by: fattogatto » Fri Nov 11, 2016 12:24 am

billwill wrote:Have you mounted the brake disk wrong way around?


The discrepancy is with alignment. Were the disc mounted wrong way 'round it would not even fit in the caliper. I will dismantle the hub(s) to check everything.
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PostPost by: UAB807F » Fri Nov 11, 2016 6:44 am

Hmm, one of those problems that makes us all sit back and scratch heads.

As has been said already, the mounting plates aren't going to change, the only thing I can think of there is either a generous coat of paint preventing metal/metal contact or maybe a washer that's sitting where it shouldn't do.

As far as the caliper re-build goes, even if you did mix up the caliper halves I don't think that would be the problem. It's the half of the caliper with the mounting lugs that determine where the caliper sits in relation to the disc, and all those will be manufactured to the same drawings. No matter how vigorous you've been with the wire brush I can't see you removing that much metal !

Calipers and mounts would be manufactured in different factories (Girling/Standard Triumph) so I can't see them being matched at birth and I didn't think they were made in RHS/LHS versions. I suppose they might be, but if so it's another school day for me.

The only other point is the discs themselves, either mounting problems on the hub (errant washers, paint, grit) or some very weird distortion ?

I'll be interested to hear how it all works out.....

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PostPost by: Elanman99 » Fri Nov 11, 2016 7:50 am

fattogatto wrote:I agree Ian.


"I would estimate there is a 10 degree difference between the disc edge and the caliper edge (if that makes any sense.)"

Well to be honest it does not make sense.
Where are you saying the 10 degrees exists between? Is the disk sitting at an angle in the caliper gap?

Out of interest, What bit of my reply are you agreeing to?

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PostPost by: vstibbard » Fri Nov 11, 2016 9:40 am

HI check following:

1. Where the brake caliper mounting plates attaches to the forged upright there is rubber ring fitted, check that you have not inadvertently caught this between mounting plate and upright, which may cause the misalignment.

2. Have you painted the caliper mounting plates, is there excessive paint?

3. Have you cited the correct stub axles as the bolt on a spin on stub axles are different.
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PostPost by: CBUEB1771 » Fri Nov 11, 2016 3:15 pm

The caliper mounting brackets are handed, do you have them on the correct sides? If they are on the wrong sides you might be trying to attach the calipers to the as-cast and tapered side of the bracket, not the side that is machined flat. That would cause the calipers to be angled with respect to the discs.
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PostPost by: fattogatto » Fri Nov 11, 2016 3:24 pm

CBUEB1771 wrote:The caliper mounting brackets are handed, do you have them on the correct sides? If they are on the wrong sides you might be trying to attach the calipers to the as-cast and tapered side of the bracket, not the side that is machined flat. That would cause the calipers to be angled with respect to the discs.


That is probably the answer. I was not aware the caliper brackets are handed, although I tried to keep them with the rest of the corner items.

To answer others - yes, the plane of the disc is about 10 degrees off the plane of the caliper opening. So, obviously I have mis-matched something. Paint is very thin on the mounting surfaces.
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PostPost by: UAB807F » Fri Nov 11, 2016 4:34 pm

CBUEB1771 wrote:The caliper mounting brackets are handed, do you have them on the correct sides? If they are on the wrong sides you might be trying to attach the calipers to the as-cast and tapered side of the bracket, not the side that is machined flat. That would cause the calipers to be angled with respect to the discs.


Yep, you're right and I was wrong earlier.

The minute I read your post I went and checked the templates I made for producing some new brackets and the top & bottom holes are different diameters, so yes, they only fit one way.

The brackets I've seen only have one machined surface though, the backs are very rough and as you say aren't going to match up with the calipers. In fact I'd be surprised if you could even make an assembly ?

edit to add, I'm getting real curious on this one, be sure to post the answer !
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PostPost by: elj221c » Fri Nov 11, 2016 4:50 pm

fattogatto wrote:Paint is very thin on the mounting surfaces.


Shouldn't be any. Metal to metal.
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