Lotus Elan

Brake caliper plating questions

PostPost by: Bigbaldybloke » Tue Dec 18, 2018 3:37 pm

I?d just query why you would split the calipers when overhauling them unless you had a leak between the two halves. Although this latest time I took the easy (expensive) route and let someone else do the work. I did overhaul them myself about 35 years ago and they worked just fine for all those years. I didn?t split the calipers. I left the pistons and seals in place and plugged the hydraulic connections, then bead blasted the calipers, carefully cleaning down the outside to get rid of any grit before stripping out the pistons, seals etc. I painted them with VHT paint again with the old pistons in place to prevent ingress into the internals. Then reassembled with new stainless pistons and seals. Original bores in the calipers were good with no scoring or corrosion so no problem, if scored or corroded it?s probably not worth continuing with a rebuild.
Hope it goes well.
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PostPost by: alan.barker » Tue Dec 18, 2018 6:06 pm

Scoring in the piston bores is not a problem. The Seals act on the Pistons. As long as the bottom of the Groove is clean no problem. The splitting of the Caliper halves enabless you to clean the bottom of the Grooves correctly. Plus the Seal between the two Halves needs replacing also.
Alan
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PostPost by: RichardHawkins » Tue Dec 18, 2018 8:14 pm

Those centralising strips ar fiddly but can be bent to do the job with patience and perseverance. An important starting point is to get the discs running true, I was guided by a friend who advised that the total indicator runout of the disc should not exceed 0.004". In my case the three point flange, or spider in the rear hub, that the disc bolts to had been damaged at some time in the cars past. I machined the mounting face of this flange to be square with the axis of the shaft. I got one side correct, but the other side required a 0.0005" shim to run true. I don't have 0.0005" shim nor could I find any but I managed to find 0.0025" and 0.003" which gave me a difference of the 0.0005" I needed at the spider to get the outer face of the disc within the 0.004" required.

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PostPost by: mbell » Tue Dec 18, 2018 8:21 pm

I got a quote from a US place to overhaul mine, new pistons, seals and external finishing. I think the by the time you'd included shipping it was heading towards $1000. So I did the job myself and just painted them with caliper job. Certainly not a high quality finish as professionally restored calipers but cost a fraction of the money and was no risk to them getting lost during shipping.

(I got the SS pistons from the UK as it was much cheaper than getting them from US supplier, even before the pound's value crashed.)
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PostPost by: alan.barker » Wed Dec 19, 2018 9:06 am

Here in France 10 years ago i did the opposite and bought in USA cheaper including Postage.
You need to check with the exchange rates :wink:
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PostPost by: Frogelan » Mon Jan 14, 2019 6:20 am

Jay

I wish you the best of luck with the passivating and did not try this myself. I used a firm called Past Parts in Bury St Edmunds, Suffolk (GB) who did a nice job (photos below) on calipers that were in good condition.

My understanding is that the whole caliper (after splitting) is passivated after blasting (I may be wrong). I went for silver coloured zinc and note that it does not always work perfectly first time round - mine were done twice (I'm probably very fussy) and that to do it well, it is expensive:

img_20190111_1132061.jpg and
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Last edited by Frogelan on Mon Jan 14, 2019 8:24 am, edited 1 time in total.
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PostPost by: alan.barker » Mon Jan 14, 2019 7:11 am

Frogelan wrote:Jay

I wish you the best of luck with the passivating and did not try this myself. I used a firm called Past Parts in Bury St Edmunds, Suffolk (GB) who did a nice job (photos below) on calipers that were in good condition.

My understanding is that the whole caliper (after splitting) is passivated after blasting (I may be wrong). I went for silver coloured zinc and note that it does not always work perfectly first time round - mine were done twice (I'm probably very fussy) and that to
do it well, it is expensive:


IMG_20190111_1132061.jpg

Very nice all you need now is stainless Pistons
Alan
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PostPost by: Evante » Mon Jan 14, 2019 3:28 pm

I decided to go with the yellow zinc passivate, and did the front two calipers. The rears will come next.

Overall, the came out quite well and did not cost too much, $60.00 for both.

Here is a pic.

Also, I did splurge for stainless steel pistons.

Thank you all for your help.

Jay S.
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