Rear brake locking after new brakes.

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Dr Strangeglove

Well-Known Member
Posts
705
Location
Lancashire
I have just swapped the rear axle case on my Defender 90 and at the same time I gave it a bit of a refurb. It's had new (refurb) case, new bearings (Timken), new calipers and discs (Britpart), new cunifer brake pipes (by me) and new Delphi/Lockheed pads. I have blead the brakes and the pedal feels good.

Took it out for a short drive today to test the brakes. The pedal was firm and it stopped so I decided to take it on the road. I slowly built up speed whilst testing the brakes. It stopped well without pulling so I deceded to try to get it to lock up.

So on pushing hard I got a rear wheel to lock. It was the rear left. I tried again and the same. Whilst doing this the truck did not pull, but I don't know if this is normal.

The road surface was a decent tarmac and dry. Front tyres are 6 month old General Grabber AT3s and the rears are older General Grabber TRs.

I was probably doing around 25-30 mph when testing.

What are your guys thoughts?
Brake pipes
20220423_110134.jpg


20220423_110104.jpg
 
Are the callipers the same size as your old axle?
New ones look like 110 fronts(unless they have used these for later models)
 
You've rebuilt the rear, could it be the front brakes aren't working as well as they could be? Have you got the same pads front and rear? If you've got softer pads up front, that can also do it
It's only the front brakes that will cause the car to pull one way or the other
 
Answers to the questions above.
Tottot these are brand new pads, so with yesterday's test, probably only about 2 miles on them. It may be worth letting them bed in as you say.

Kermit_rr, i changed the front less than 100 miles ago (it does not get a lot of use!) And they improved the brakes when done. I have Ferodo pads on the front and Delphi on the rear.

Slomofo, I have only changed items from the rear flexible backwards. The Tee pies was an old one I reused but it looked OK and passes air through OK. Cleaned up and used. Everything else on the rear brakes was new.

I will look for the bias valve to check one is fitted.

Before I changed any of the brakes I could get it to stop and lock the front wheels if I really put some pressure on. The brakes feel better now and it stops better. I am happy with their performance other than that wheel locking up - but I don't want that becoming an mot fail.
 
Is it just the way the photo is rendered, or is there something amiss with the driver's side brake pipe? Just inboard of the clip, it seems to have a kink in it. If so, that may explain why the passenger side (with a free fluid flow) is locking before the driver's side where its restricted.

The other thing I've found is that an awful lot of air can hide in a Land Rover braking system. I find with mine it helps to let it settle overnight and then bleed a bit more through the following day, and then a drop more a week or so later just to be on the safe side.
 
I see from the picture in post 11 that the tube isn't pinched, it's just stepped up to go over the bracket on the axle.

Even so, it might be worth having a look at it, just in case the process of cutting and flaring has restricted the flow compared to the other side. Plus making sure the pistons move equally freely on both sides. From the description of the problem it sounds like it's a side to side balance problem, rather than a front to rear balance problem. If it was the latter, I'd suspect the balancer valve. But there's clearly pressure getting to the back of the vehicle, it's just not getting equally distributed from side to side.
 
Maybe you are over thinking it? run it and see how you get on, as for the mot they will most likely be using a tapley/bowmonk meter so wont notice any individual rear locks as a stand out feature, their main concern will be the meters readings, and seeing what you have forgot to refit during the rebuild!

Ps that is some very smart brake pipe bending and fitting, I like stuff like that as it shows you are proud of your work.
 
lynall said:
Maybe you are over thinking it? run it and see how you get on, as for the mot they will most likely be using a tapley/bowmonk meter so wont notice any individual rear locks as a stand out feature, their main concern will be the meters readings, and seeing what you have forgot to refit during the rebuild!

Ps that is some very smart brake pipe bending and fitting, I like stuff like that as it shows you are proud of your work.
Click to expand...
Thanks Lynall, I will try running it for a while before worrying too much about it.

I am trying to learn things as I go along and making the brake pipe is just another thing I want to try and get right. It wasn't too difficult as I had an original pipe to copy. It is quite satisfying to replicate something and you feel you have achieved what you set out too. Whilst everything I am doing is on a budget, I do have time to try and make the best of what I have available. There is an amount of satisfaction making a nice job whilst spending minimum (what you can afford) money!!
 
Your rear brakes should not lock-up under heavy braking, this is dangerous, that's why there is a pressure limiting valve.
I would suspect that the side that isn't locking-up may not be operating properly. Is your new brake pipe kinked and restricting flow to one brake and putting all the braking effort on the other side?.
 
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