Front caliper clearance too small after rebuild

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derekal
Posts: 19
Joined: Tue Mar 15, 2011 11:14 pm
Location: Dublin, Ireland

Front caliper clearance too small after rebuild

Post by derekal »

Hi - I'm hoping someone might be able to shed some light on front brake caliper sizes.

The latest stage of restoration of my '83 635 has been refitting the front brake calipers after cleaning, painting and rebuilding. I had noticed that one of the calipers, although very similar, looked a little less weighty than the other, but didn't think too much of it assuming the PO must have replaced one with a later version perhaps.

Anyway, the end result is that the slightly weightier one appears to have more clearance - I fitted it first to the car with no issues. When I went to fit the second, it soon became apparent that there is not enough clearance between the new pads for the 25mm disc. Clearance between pads measured just over 21mm. The piston was new and pushed in as far as it would go. On removing the new piston to investigate, I discovered that there is a raised section within the caliper which is accommodated by a recess on the original piston, a feature missing from the new piston - see photos. Refitting the original piston buys about another 2mm. But still just shy of allowing the disc to squeeze in.

Caliper clearance from the original piston (fully pushed in) = approx. 64mm
Pads (ATE KBA 607046) are approx. 20mm each (13mm of pad)
I haven't measured the clearance of the other caliper as its on the car, but it appears to have a larger overall clearance which was partly why it looked slightly weightier.

So, wrong caliper? Wrong pads? I'd welcome any insight.
Thanks.
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olympia57
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Re: Front caliper clearance too small after rebuild

Post by olympia57 »

Hi Derek.
If the pistons and pads are correct for year/model then it sounds like mismatched calipers .
I'm a series 1 man with different front calipers but is there any identifying part no.cast into the bodies ?
Don
1981 635 series 1
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derekal
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Joined: Tue Mar 15, 2011 11:14 pm
Location: Dublin, Ireland

Re: Front caliper clearance too small after rebuild

Post by derekal »

Hi Don,
Yeah, it certainly seems to be the case. I suppose the previous owner may have replaced the caliper which worked with the part worn pads at the time.

The problem caliper is marked with the no. 98.
I can't see any markings on the other caliper although that may be a result of the de-rusting and painting I've done.

Derek
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derekal
Posts: 19
Joined: Tue Mar 15, 2011 11:14 pm
Location: Dublin, Ireland

Re: Front caliper clearance too small after rebuild

Post by derekal »

Hi,
I'm in the process of sourcing a replacement caliper.
Am I correct in saying that the E28 has the same front brakes?
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