MGB Front Brake Calliper Rebuild: Replacement of Seals and Pistons on Disc Brakes

A bit of an impromptu video this week; whilst I was carrying out the brake service on my MGB I found that one of the brake calliper pistons was sticking and causing uneven wear on the pads. Investigating further it seemed as though the piston has caught the outer rubber seal and dislodged it. Luckily, I had a seal kit on hand and was able to rebuild the calliper.
When shooting the video it was hard to show what I was doing when removing and re-fitting the seals, don’t hesitate to get in touch with any questions.
PLEASE NOTE: I would only recommend rebuilding the callipers if they are in good condition with no rust or heavy scoring on the bores. By the time you’ve bought a seal kit and replacement pistons you are around halfway towards the cost of a brand-new calliper. Always take extra special care when working on your vehicles barking system, if you are at all unsure please get expert advice.
Big thanks to my sponsors for 2021 www.opieoils.co.uk/ for all the lubricants and brake fluids etc
#MGB #ClassicRacing #CarDIY

[@justinmason5381]

This just helped me put the finishing touches on renewing the front brakes on my 71 Midget. Cheers from Arizona! Thanks man.

[@davidrussellwilks]

Many thanks for your message, delighted to hear that it helped!

[@andywarby117]

Great Video as always David, Very informative and detailed. Keep up the fantastic work.

[@davidrussellwilks]

Many thanks Andy!

[@malcolmwatt9884]

david, thanks for the reply, I have it fixed now, cheers

[@jptoro2007]

As always David...thank you. Working on rebuilding mine. Thx

[@davidrussellwilks]

Many thanks Juan Pablo, hope your rebuild all goes well.

[@timrobinson2984]

this video,helped me a lot so gets thums up,

[@davidrussellwilks]

Many thanks Tim, glad it helped.

[@bshnabel]

🍺

[@BrailsfordsRides]

Great video David, I wonder if I should replace mine? They stop me lol. I have to figure out what is leaking from my rear end. Some fluid residue on the wheels which can't be brake fluid because the reservoir is good, but I feel it is coming from the axle

[@davidrussellwilks]

I found that both my callipers were slightly seized; I imagine the high temperatures don't help. In the end I swapped them both for brand new ones (video coming soon). I'll rebuild both the old ones and keep as spares. Uneven brake pad wear is a sure sign something's not quite right, it's easy enough to check. I had an oil leak on my rear axle; there was slight corrosion under where the shackles/bump stops for the springs are. I think as the axle got hot the axle oil was vaporising and leaking out, took me a while to find it. It was only a tiny pin hole

[@CharltonsClassics]

Hi David. I really enjoy watching your videos which are always very informative and concise. I must say I’ve been trying to work out which gloves you are wearing as I wouldn’t mind getting myself a few pairs for working on the car. Which ones do you normally use 😊?

[@davidrussellwilks]

Thanks for your message Chris, the gloves I use are a nylon PU glove. I do suffer with bad skin on my hands and oil, great etc really doesn't help. I find these gloves work really well for me, they are stronger than latex and also let my skin breathe. They are also fairly lightweight/thin so can be used for fine work too. I buy mine here www.ebay.co.uk/itm/24-Pairs-Of-Brand-New-White-Nylon-PU-Safety-Work-Gloves-Builders-Grip-Gardening/181031170878?ssPageName=STRK%3AMEBIDX%3AIT&var=480203076638&_trksid=p2057872.m2749.l2649 I also choose white so I can see when they are dirty.

[@CharltonsClassics]

@@davidrussellwilks Hi David. Thanks for the info there. I will definitely be getting myself some of these. Looking forward to the next video👌🏼

[@davidpengilly400]

Good video, thanks very much. I’m wondering if it is necessary to replace the steel retainers in a calliper at all as there is no contact between them and any moving part- they just retain the seal. You didn’t actually find any reason why the piston was sticking on one side - no corrosion but possibly a build up of dirt? I have always treated the callipers as a service item and replace them with the pads. Similarly the rear pistons are a disposable item after each intense European rally they just don’t seem to survive heavy use. I now have so many used calipers that I thought I would rebuild them with new seals and a stainless bleed Nipple and then recycle them.

[@davidrussellwilks]

Many thanks for your message David, the steel retaining rings tend to be included with the seal kits so I just swap them as a matter of course. They can get damaged when you remove them, but otherwise there would be no reason why no to re-use them. I never got to the bottom of why the calliper seized, a clean up of both the piston and calliper seemed to cure the issue. In the end I did the same as you and just bought two new callipers, I fitted new stainless steel pistons but at £100 for a pair it works out less than the cost of have an old set re-electroplated, a new seal kit and bleed nipple. I've kept the old ones as a spare but most likely I will just buy another new set when the current ones start to look a bit tired.

[@PhilSavageHDCCHUCC]

Would it be possible for you to cover changing the brake rotors on a wire wheel MGBGT as part of your next video please? It's a job I'm close to doing but have read that there might be more to it than with normal alloys due to the knock on nature of the wires. Thanks again for another informative video 👌

[@davidrussellwilks]

It's the job I'm doing at the moment Philip. The steel/alloy wheels can be a bit easier to work with than the wires as the nut on the stub axle is far easier to access, with your wire wheel hubs finding and removing the split pin can be tricky. A magnet type pick up tool is also especially useful for removing the end washer and shims in the bearing. I'm around halfway through, but wanted to cover the rear brakes too in order to make a comprehensive video covering everything.

[@malcolmwatt9884]

Hi, brilliant video, thanks. Completed calliper rebuild following video. Pressed metal dust covers and heard the click. Only issue is that they and the rubber seal come out with the pistons when brakes are pressed . Can't see where I have gone wrong. Just how much pressure is required to seat these?

[@davidrussellwilks]

The metal rings should be totally flush with the surface, has one side come away slightly?

[@aaronjeffers2139]

I tried the same technique on mine and it just bent the ring. It would appear the rings I got were a hair too large.

[@davidrussellwilks]

The rings are very thin, unfortunately it is easy to damage them when refitting. You could try freezing them first, it might just make them a tiny bit smaller.

[@dgriffin6074]

Why not remove the two bolts to separate the caliper halves? That would make the rebuild much easier.

[@davidrussellwilks]

Thanks for your message, I went down the split calliper route a while ago and whilst one re-sealed fine the other always seemed to weep a little at the joint, even with new o-rings. For some reason Moss do not recommend splitting the callipers but I can see no real reason not to. You will need to install a new seal (17H7679) and new bridge bolts (27H4353). I believe the bolts are the stretch type and should only be used once. Personally I don't find it to bad putting the seals in as they are, I certainly find it easier to pop the pistons out too with both sides together.

[@dgriffin6074]

@@davidrussellwilks Thanks for your valuable advice. After carefully inspecting my calipers on my workbench and noting some rather deep scoring on the metal surfaces, I decided to purchase remanufactured calipers from a vendor that doesn't require a core charge. Also, there WAS unequal wear on the old brake pads, so I purchased new replacements. Hope all goes well with you.