Early 90/110 brake question

flat · Jan 28, 2017

Gents.

Discs and drums 90.

Early 90 - front calipers seized so I replaced them with 110 versions (bigger piston diameter) and at the same time I fitted a new master cylinder and servo and all new flexis.

The master cylinder I fitted was the part number for an early 90.

Brakes bled good, and bite hard however the travel on the pedal before any braking action is a couple of cm, then it's very sharp action - barely 'featherable' but the brakes are very good.

Servo is fine and all the usual test to test master cylinder and servo are fine aswell.

My question is:

- could this 'excess travel' be rectified by adjusting the actuating rod (I don't recall
Adjusting it when fitting the new servo/mc)

- or should I fit the early 110 master cylinder (which i believe has a bigger stroke volume) to match the early 110 calipers?

Land Rover must of spec'd different master cylinders for a reason?

Thanks

Ed

Rougharse Racing · Jan 28, 2017

Sounds like it could be a miss-match between your calipers and master cylinder, except the excessive travel before the brakes apply, I would make doubly sure that your brakes are fully bled and that the rear drums are properly adjusted before you start swapping bits. I think later defender 90's use the same front brakes as the 110, it could be worth checking if the master cylinder changed at the same time.

flat · Jan 28, 2017

Rougharse Racing said:
Sounds like it could be a miss-match between your calipers and master cylinder, except the excessive travel before the brakes apply, I would make doubly sure that your brakes are fully bled and that the rear drums are properly adjusted before you start swapping bits. I think later defender 90's use the same front brakes as the 110, it could be worth checking if the master cylinder changed at the same time.

Thanks sorry forgot to say. Rear drums adjusted the other day and it made a slight difference.

Yes later 90/110 had same calipers and same master cylinder.

Have fully bled them - they deffo aren't spongy. It's more like they are binary brakes (on/off).

I wonder if it's a mismatch.

Going to check the actuator rod as I may have cocked that up when fitting.

It passed an mot with them like this, I advisories, nothing. That was with a taplow not rollers

Turboman · Jan 28, 2017

flat said:
Thanks sorry forgot to say. Rear drums adjusted the other day and it made a slight difference.

Yes later 90/110 had same calipers and same master cylinder.

Have fully bled them - they deffo aren't spongy. It's more like they are binary brakes (on/off).

I wonder if it's a mismatch.

Going to check the actuator rod as I may have cocked that up when fitting.

It passed an mot with them like this, I advisories, nothing. That was with a taplow not rollers

Have you checked the rear drums for trueness, they can go oval, which makes the pedal pulse under braking, and very difficult to adjust.

flat · Jan 28, 2017

Turboman said:
Have you checked the rear drums for trueness, they can go oval, which makes the pedal pulse under braking, and very difficult to adjust.

Yep I did when I overhauled the brakes, only at home with a dial gauge not at an engineering place or anything. The drums were also not very worn. I replaced the rear shoes as one of the the friction material was breaking up so changed both sides shoes and spring etc but left the drums.

jamesmartin · Jan 28, 2017

flat said:
Gents.

Discs and drums 90.

Early 90 - front calipers seized so I replaced them with 110 versions (bigger piston diameter) and at the same time I fitted a new master cylinder and servo and all new flexis.

The master cylinder I fitted was the part number for an early 90.

Brakes bled good, and bite hard however the travel on the pedal before any braking action is a couple of cm, then it's very sharp action - barely 'featherable' but the brakes are very good.

Servo is fine and all the usual test to test master cylinder and servo are fine aswell.

My question is:

- could this 'excess travel' be rectified by adjusting the actuating rod (I don't recall
Adjusting it when fitting the new servo/mc)

- or should I fit the early 110 master cylinder (which i believe has a bigger stroke volume) to match the early 110 calipers?

Land Rover must of spec'd different master cylinders for a reason?

Thanks

Ed

i would certainly try adjusting rod first,obviously if you went too far there would be no free play in pedal at all ,pedal travel once free play is taken is a different issue

flat · Jan 28, 2017

jamesmartin said:
i would certainly try adjusting rod first,obviously if you went too far there would be no free play in pedal at all ,pedal travel once free play is taken is a different issue

Yep I thought adjusting the rod would be easiest thing to check. Will measure it carefully, is 1.5mm the free play amount?

WhTs your thoughts on the calipers/master cylinder mismatch?

jamesmartin · Jan 28, 2017

it should only increase pedal travel a little, a larger piston does require more travel for given movement of the piston but pads should be fairly tight up to disc once run in so not needing much piston movement, what youve done has been done quite a few times with no issues, but you cant guarantee it will be perfect on every truck due to the numerous variables

flat · Jan 28, 2017

Thanks, will check the servo rod adjustment first and rebleed before i fit a new 110 master cylinder.

Can't think what else it would be!

flat · Jan 30, 2017

Okay. Checked the master cylinder/servo rod - had 3mm free play and the locknut was loose so adjusted that and brakes are way better, they are actually quite good.

Didn't need to change master cylinder.

Early 90/110 brake question

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