Brakes seem to be holding on too tightly

[alaric]

Hi.

My car pulls slightly to the right under heavy braking. I checked the front hubs with the wheels off and found that after applying the brakes and releasing the right hand hub pads are stopping the hub spinning on at all when I try to set it spinning by hand, whereas the left hand one spins on about half a turn. As the car is jacked up there's no end float movement to push the pads out, so it's only the spring back of the seals that would release the pad grip. I wondered if what I'm seeing is normal. The car does roll freely when on the ground.

I've taken the pads out to make sure they're not binding. With no pads in both front hubs spin freely..

If the piston seals are too hard, or in the wrong way round, this is what I would expect to see. I don't want to start pulling the front calipers apart, but will if there's really a problem. How freely do others hubs spin?

Thanks.

Sean,

[steve lyle]

When I had those symptoms it was the result of rusty pistons. I rebuilt the calipers with new stainless pistons and it fixed the problem. The free rotation depends on speed of rotation, but it’s easy to get a full revolution, iirc.

[alaric]

Thanks Steve. Yours sound a lot freer than mine. The pistons and seals in my calipers do appear to be new, which is in line with what I was told when I bought the car. They should be stainless replacement ones. The pistons are very hard to push back in though. I'm wondering if they're a bit tight. Maybe I should just drive the thing for a few hundred miles haha. The problem may just be that they're new.

Sean.

[Donels]

It is just the pull from the seals that releases the pads so there’s not a lot of force and anything causing stiction of the piston will prevent the pads from releasing. I would not think that just driving it will improve matters. I’ve seen an Elan pull violently to one side when the pads have failed to release so I suggest you investigate further.
As stated remove the pistons and check, your life may depend on it.

[Spyder fan]

One reason for an Elan to pull to the left or right under braking is worn or faulty suspension bushes. I had new bushes fitted to my +2 a few years back, I went to drive it home and nearly ended up in the ditch because it pulled to the left under braking, the new (faulty/substandard) bushes were like toffee, you could see the wheels moving toe out on the rollers at the MOT testing centre when the brakes were applied.

For safety's sake, unless you know the full history of your brake caliper rebuild I would get them redone to ensure they are safe. It would be a very good investment, but also examine your wishbone bushes and trunnions etc.

Keep safe!

[alaric]

Hi. Thanks for the replies. Yes brakes are pretty important aren't they. I just replaced the master cylinder with a new one from Tony Thompson racing - 0.75" version. I replaced it because I wasn't happy with my rebuild of the original. It didn't feel right. The new one is lovely though. Really smooth.

Ok I'll get the callipers off and pop the pistons out. The only bit I think I'l struggle with is putting the seal retaining ring in - a new set of course. In the past, with my Cooper S discs on the mini I had years ago, I made up a ring of just the right size that I could use to press the retaining ring into place. Guess I'll need the same this time around. I do have decent press to push the pistons in with though .

The suspension bushes all look and feel like new on my car, so I really don't think it's that, and there's no bump steer either, which I would expect to feel if the geometry was not stable.

All the best.

Sean.

[Donels]

When I stripped my rear callipers I found the rear pistons really difficult to remove. The pistons had been replaced but the surface finish was awful, not smooth chrome plating but record like grooving. What they were like to use I have no idea but they were awful. So new pistons do not mean good brakes.

[alaric]

Hi again.

I've been looking for pistons and seals, but also checked the price for complete callipers. I can get a pair for less than £100.

I've found them on Ebay but also from brake part specialists like this: https://www.angclassiccarparts.co.uk/pr ... -1857-6772

Has anyone bought callipers for this sort of price? Are they any good? I'm tempted to get a pair just to try out and see if the problem with the car pulling to the right is solved.

Regards.

Sean.

[alanr]

Just putting pistons and seals into 50year old calipers that have scored or corroded bores is a complete waste of time. The calipers either need to be completely replaced or the caliper bores re-sleeved by someone who has the appropriate engineering equipment.
Like these people :-https://www.pastparts.co.uk/

Personally I am not yet convinced by the low cost and I suspect chinese made calipers that are on the market. Maybe ok,maybe not!
Personally i would sooner have my old ones re-sleeved.

Alan

[Andy8421]

Absent a suspension problem, as a general rule, if the car pulls to the right under braking, there is a problem with the left hand side brakes, not the right.

A slightly sticky piston is not going to have any impact on heavy braking, but as pointed out above, it doesn't hurt to have a look to see what is going on in the calipers to check everything is OK, particularly if the car is new to you. From the symptoms you describe, I would have thought it was most likely a suspension problem - heavy braking loads up the suspension bushes and swivels and any play or squish can allow the wheel alignment to change and the steering to pull.

Having had many Minis, the fixing ring for the caliper dust seal is different to an Elan, It isn't a pressed in ring, more of a sprung circular piece of wire - and is very easy to fit.

I messed around for ages rebuilding the calipers on one of my Elans, and reached the conclusion it was easier to send to a specialist, particularly as I wanted it plated. I used http://www.classicarautomotive.co.uk/ who I can recommend - others on here have had good experiences with them as well.

If you choose to rebuild yourself, the standard repair kit doesn't include the seal that goes between the caliper halves. I think it is just about impossible to rebuild a caliper without splitting, so you will need to source those separately. I bought a couple of no-name repair kits from one of the usual suspects that was rubbish, nothing seemed to fit properly. I eventually bought a kit from https://www.biggred.co.uk/ - I wasn't expecting much given the name, but it turned out to be good quality and fitted perfectly.

Good luck, and report back when you have found the problem.

Andy.

[2cams70]

A couple of tips:

If you jacked up the wheels and found one side that dragged much more than the other it's likely to be the calipers. Another alternative is that the hydraulic hose on that side has swelled internally but that's less likely. I don't believe you have a problem with the suspension based on your description of the symptoms.

The usual cause of calipers sticking is water ingress under the dust boot. The moisture sits in the area of the cylinder between the top of the piston and the seal. It collects there and causes corrosion in the small gap between the piston and cylinder and this corrosion causes the piston to stick. Stainless steel pistons won't help with this as it's mainly the cylinder corroding not the piston corroding that causes this. Stainless pistons may even promote cylinder corrosion and make it worse. Make sure you pack the area under the dust boot and between the piston and cylinder above the piston seal with rubber grease. This helps prevent water ingress.

The most difficult part of rebuilding a caliper is removing corroded in pistons. By far the best and easiest method is to use the hydraulic pressure in the brake system to force the pistons out before you undo the hydraulic connection to the caliper. Remove the pads and pump the pedal until you have extended the pistons so they contact the disc. To extend them further you can unbolt the caliper so the piston extension is not restricted by contact with the disc and keep pumping the pedal. You may have to restrict the movement of one piston a bit if one moves but the other is stuck. Hopefully this is enough to give you a general idea. Key thing is to use the brake hydraulics to do the work. It's a far better method than trying to fluff around with compressed air or pumping in grease (that really is a big no no if you aren't planning to split the caliper halves)

If the caliper is not leaking between the two halves and you aren't planning on plating the calipers it's not essential to split them and replace the seal between the two halves. It's static and doesn't wear. It only becomes ineffective if the fluid has at some stage become contaminated with for example mineral fluid.

The seal in a caliper is between the piston and the piston seal. The cylinder surface inside the caliper is not a seal surface so some corrosion is acceptable and won't cause any fluid leaks. Sleeving is not required.

One final note - If you can original is always best when it comes to brake parts. Don't replace the hard components with repro. parts unless you really have to.

[alaric]

Hi all. Thankyou very much for the advice and links / recommendations.

It's good to hear that the sealing ring is easy to fit. Given that I am very tempted to try and get the pistons out, as there's no sign of corrosion at all - it all looks new - not surprising though as the car has been so well looked after. So I suspect they will pop out quite easily even if tight.

My plan is to check the suspension first as suggested, as I haven't done so yet and have assumed it's ok - my opinion on that was a bit hasty I think.

Then I plan to get a new pair of callipers, and try them, but will probably pull the current callipers apart first.

Re the pulling to left or right and which wheel causes it, I just reasoned out that if the car twists to the right, it must be experiencing a larger force from that side - I think it's only on take up. I wasn't surprised to find it was the right calliper that was holding on the tightest. But no worries - I'll work on both callipers together.

OK I'll post pics as I go along.

BTW I just bought a t shirt that says Loads Of Trouble Usually Serious on it. Haha.

All the best.

Sean.

[2cams70]

If they are repro calipers it can be that the groove dimensions cut into caliper for the seals aren't correct. Reverse engineering something is not the same as engineering something in the first place. That's why I say original is always best!

Don't kid yourself either that that the pistons will be easy to remove even if they aren't corroded. Heed my advice above to move the pistons as far out of the cylinders as you can before disconnecting the hydraulic line. Remove the dust boots so they have unrestricted movement before pumping them out.

Don't think it's a good idea either to try and twist them out with pliers. You'll burr the shoulder on the piston that seals against the dust boot. This will give an easy path for water to enter underneath.

[alaric]

Ok so I'm bracing myself to remove the pistons from the offending caliper on my car. The disc was warm on that side when I took it for a drive last week, while the other side was cold, so it's not something that can be left alone. Having tried to buy a replacement and being informed that I'd have to send mine to the company, and it would take 8 weeks to come back, I'm prepared to have a go myself.

All the best.

Sean.

[Foxie]

I think I might have posted this a long time ago, but when I was doing a big refurb of my brakes I made up this rig to remove pistons. I used a spare M/C and a cheap foot pump assembly.