TR4A Calipers

[Bully]

I've just had a 4A fail it's MOT on front brakes.   To cut a long story short, the pistons have rusted in the calipers.

 

After much sweat and tears, I have split the calipers, and managed to remove the pistons and rubbers.

 

Refurbishment looks quite straight forward, with new rubbers and stainless steel pistons available from Moss.   However, I understand that joining the two halfs of the calipers back together isn't so straight forward.

 

Do I need to replace the bolts (are they stretch bolts?), and what are they torqued to?   Or should I not bother, and just buy a refurbished exchange set?

 

Any advise would be great.

 

:cool:

[Tr4Tony]

You need to be very careful here Bully - I reckon a home job is 50% successful even if you get all the right bolts and bits - better to exchange them.

 

There is a firm called Big Red who can do them for you and TR Shop had sets of two for £100 exchange - I used these and they are great.

 

Alternatively now might be the time for uprated ones - I run twin pot calipers on my 4a - hard to get but very very good. Wilwood also do alloy ones which are excellent - uprating is much more expensive but you forget the first time you need to stop rapidly !

 

Regards

 

Tony

[Kiwifrog]

After Having my front brakes lock on on the weekend and boil the fluid at 70MPH leaving me with no brakes at a very embarrasing moment I second Tonys thoughts about the calipers being a profesional Job. I believe mine sufferedbecause the car has not been driven for a couple of years and they seemed all right at lower speeds.The car has now been booked into a specialist for a caliper rebuild. I would have been much more embarrased if I had actually hit the back of My friends "Like New" TR3a  which had stopped in front of me, and the owner had Just got out of the paint shop 2 days before :blush: :blush:

[tr7v8]

just add to dad's post, brake engineering contact details are on their website http://www.brake-eng.com/

 

Tom

[Dale Moore]

Hi Bully,

While agreeing with everyone that, of course, brakes are an important safety requirement, rebuilding calipers is not rocket science, if you've succeded in the piston removal, providing there is no damage to bores threads etc, the reassembly is straightforward. Various books tell you to beware of splitting the calipers, but how do you remove siezed pistons otherwise? Take them to a garage to do, they will only bolt em back the same way you or I would. Part ex them and get someone elses! I dont believe the bolts holding the halves together are stretch bolts, the're 40 years old dont forget. I reused the old bolts, and tightened up to a sensible torque for that size thread, 3/8 UNF I think. Apparently there are 2 torque settings for the inner and outer bolts, but not disclosed anywhere ???  Check the square section o ring joining the mating surfaces. One of mine was missing, and been bolted back up by P.O. I don't think it is listed in Moss but is avalable as a Stag or Spitfire spare, if my memory is correct.  How many of you born again bikers, jump at the chance to pull your multi pot calipers to bits, on your 165 mph road rocket because its got a bit stiff pushing it out of the shed

Best of luck

Dale

[Bully]

Thanks for all the advise.

 

For the sake of an extra £30 I have gone with the refurbished calipers from the TR Shop (£49.50 each refurbished as opposed to £70 for new stainless steel pistons and gaskets).

 

Postage is £12.   Exchange surcharge is £100, until I can get the old ones back to them (trip planned to London later in the month.)  

 

Problem is, because I have split them, they want to send them back to the refurbishment company to get an OK, before returning the surchange.

 

This could get costly!!!

 

???

[Andy Moltu]

If you can find the correct torque settings then what's the big issue?

The main reason for splitting the two halves of the caliper is to make cleaning them out easier.

It isn't rocket science - a TR caliper is made of 2 cast halves each of which house a piston with a seal. the two halves again are bolted together with 4 bolts with a seal between.

Certainly you have to be dilligent in their reassembly but if you don't rate yourself to be competent at reassembling them you might ask the same about bolting them back on the car itself & bleeding the brakes.

I guess there is an industry built up on perpetuating the myth about simple components being untouchable.