Lotus Elan

Brake caliper plating questions

PostPost by: Evante » Mon Dec 17, 2018 1:31 am

I am rebuilding my calipers on my Sprint and thinking of having them zinc plated. I have a few questions that do not appear to be addressed in previous posts.

1) when plating, do you need to protect the surfaces of the two halves of the caliper that contact each other when putting the two halves together or do you just plate all of the surfaces?

2) relatedly, do you protect the bolt holes, bleeder hole, and brake line fitting or are they plated as well? If they are plated, will the bolts etc. still fit or do they need to be tapped later?

3) the same concern goes for the space for the inner rubber washer.

4) finally, what about the space for the piston and O-ring? Does that get plated or does it need to be protected?

Thank you in advance for your advice.

Jay S.
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PostPost by: 74Twincam » Mon Dec 17, 2018 2:36 am

Hi Jay,

I plated the calipers on my Europa Special about 18 years ago, with white (blue) zinc chromate. I made sure they were completely separate parts/torn down, but didn't mask anything at the time. I had no problems with fitting parts when I reassembled them, nor any functional issues since. It was a while ago, but I didn't have to re-tap anything. I don't think caliper paint was available widely as an alternative when I did this, the plating has held up well enough.

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PostPost by: 661 » Mon Dec 17, 2018 10:06 am

I'm afraid I don't know the specific answer, but if you are in the UK I'd strongly recommend just sending them to Classicar Automotive in Cheshire. They come back like new and, of interest, in an anodised finished.
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PostPost by: Mazzini » Mon Dec 17, 2018 12:08 pm

661 wrote:I'm afraid I don't know the specific answer, but if you are in the UK I'd strongly recommend just sending them to Classicar Automotive in Cheshire. They come back like new and, of interest, in an anodised finished.


+1 I've been using them since they set up in the 1980's. Brakes are a critical component, if you're not sure take them to somebody who is qualified to do them, it's not worth the risk.
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PostPost by: alan.barker » Mon Dec 17, 2018 1:13 pm

661 wrote:I'm afraid I don't know the specific answer, but if you are in the UK I'd strongly recommend just sending them to Classicar Automotive in Cheshire. They come back like new and, of interest, in an anodised finished.

I don't think they can be Anodised that's for Aluminium Alloys.
I think you mean with a Pasivated finish :wink:
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PostPost by: Evante » Mon Dec 17, 2018 1:54 pm

Thank you all for responding.

Bill, would you paint the calipers now instead of plating?

Jay
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PostPost by: 74Twincam » Mon Dec 17, 2018 3:27 pm

Jay,

I would definitely choose plated over painted again. I think plating offers a better way to clean them prior to finishing, better adhesion (no chance paint would chip/burn off), and a thinner, more consistent coating that wouldn't interfere with the function. Importantly to me, plating protects the inside of the caliper piston bore and other areas you can't get to with paint.

I did a little poking around as well and found this reference from a Porsche brake re-builder, thought it was a good reference- http://www.pmbperformance.com/brakehowto.html

Attached is a picture of mine, the fasteners have some surface rust now but the caliper body still looks fair enough. I did the rotors and a few other components as well. The zinc chromate on the rotor surface was machined off when I had the rotors turned post-plating.

Cheers
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PostPost by: 661 » Mon Dec 17, 2018 4:43 pm

alan.barker wrote:
661 wrote:I'm afraid I don't know the specific answer, but if you are in the UK I'd strongly recommend just sending them to Classicar Automotive in Cheshire. They come back like new and, of interest, in an anodised finished.

I don't think they can be Anodised that's for Aluminium Alloys.
I think you mean with a Pasivated finish :wink:
Alan

I'm sure you are correct as I only have 'A' level chemistry which is well past its sell by date.
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PostPost by: miked » Mon Dec 17, 2018 6:45 pm

I have done these.
Split and de greased and then medium blasted (metal oxide) all parts except the calpier half faces. Can tape these. Also left some old nipples and bleed screws in holes. During a period of not having blasting available i gave some to a guy who blasted the surfaces and messed up the seal pocket. After being told and even taping them. :evil: To recover my engineering friend recut the seat surface and then machined the surfaces of both halves. Not an easy job.
So be careful if you take it on.
Yellow zinc passivate is the standard finish as it is more resilient than the silver.
Do not passivate the bolts, it weakens them. Use new black high quality bolts or cap type allen bolts. It is wise to clean threads with a tap.
You are not really supposed to split calipers as Joe Public and may struggle to get the little seal that goes between the calpier halves. In a way a bit like attempting gas fitting.
Kind of on your own.
Also you need to do a boat load of cleaning with a fine scraper and rotary wire brushes in the piston seal groove. This is where the rust collects. The medium blast will only clean the bottom. If there is any crap in the seal groove fluid will get past. Dont ask how i know. :oops: this takes time and crap comes out for ever and a day.
It is a satisfy job but the blasting is a dirty messy task.

As the guys say, Classicar Automotive are the Bees Knees. Front Calipers are so cheap from them i would not dirty my hands anymore. As regards rears, ulness they are low mileage in nice condition i would hand them over too as the dangling bits are usually worn and either need new parts or oversize pins making. Lathe required.
I have not looked at there prices recently (last 12 months) but they were great. Far lower that any other comercial brake outfit. Also two smashing friendly guys.
Cheers Mike
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PostPost by: RichardHawkins » Mon Dec 17, 2018 8:26 pm

Gentlemen,

Classicar Automotive overhauled my rear callipers last year. I drove there to deliver, and thought the place was scruffy/dirty, but decided to let them do the work as they have a good reputation. Someone mentioned the dangly bits (handbrake mechanism), I was disappointed with what I received when the callipers were returned. The pivot pins were the wrong size, and the curved face levers that bear onto the brake pads all had different curvatures. I had to rework these levers so that the curvatures were all the same. I used an original component borrowed from a friend to make a radius gauge, then used this gauge to correct the levers. I then had the levers re-plated. I hope that the work on the hydraulic part of the callipers is better.(my car is not yet in one piece).

I know I am a fussy old bugger, but I was disappointed. I had just come out of hospital, and thought this was something I could entrust to Classicar, also I don't know where else to go, or where to buy components.

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PostPost by: Gopherit » Mon Dec 17, 2018 8:27 pm

img_20181009_181304759c.jpg and
I will certainly look at Classiccar Automotive, but up to now have had quality service from Bigg Red:
http://www.biggred.co.uk/
Oven baked paint amongst other finishes.
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PostPost by: Evante » Mon Dec 17, 2018 9:35 pm

Thanks for the advice.

I am in the US and it would probably be prohibitive to mail the calipers to ClassicCarAutomotive.

I have purchased all of the parts already, seals, dust covers, stainless pistons, etc. so I guess I am already committed to the DIY path. Hopefully, it will work out.


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PostPost by: 74Twincam » Tue Dec 18, 2018 12:25 am

Jay,
Another resource here in the States worth calling is White Post Restorations in Virginia, lifetime warranty and brake specialists. You can find them on the web-

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PostPost by: Bigbaldybloke » Tue Dec 18, 2018 1:25 am

I looked at overhauling the calipers myself, but in the end I purchased exchange rear calipers from Kelvedon and new front ones as they are readily available and quite cheap.
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PostPost by: miked » Tue Dec 18, 2018 11:02 am

Jay,
Sorry, i did not realise that you were over the pond. Classicar will supply parts to help out if you are stuck. Maybe an idea with smaller bits that are less costly in the mail.
They have also remanufactured the handbrake components that i mentioned can be very worn. Again only small parts.

Re: the centralising strips for the hand brake pads. To my understanding these start off straight. Unless i am confused they are tweaked when fitted to the car to hold the pads away from the disc, thus preventing pad wear. Everything has to be together to make these subtle adjustments. In place on car. This is how i have always fitted them. Quite a few attempts of taking them off and making small adjustments until they make contact. Then screw driver in to make final tweak.
Classicar actually supply a suitable compression spring that goes on the tie rod cross adjuster to assist keeping the two pads apart. This works pretty well to separate but the strips centralise.
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