Drum brake question

jgra1 · Unread post by **jgra1** » 18 Aug 2006, 22:45

Hi all, trying very hard to get a 39 year old camper through an MOT tomorrow.

One question, why is it that, my brake pedal moves ? 10cm before it becomes firm and the vehicle stops, when, with handbrake on, it only takes 3cm?

I am (I think) an experienced home mechanic.
I know what is happening in relation to above.
The shoes are well within service limits.
The brake adjuster works on the bottom of the shoes, the handbrake and slave cylinder work on the top..
Is it simply the the return springs are overcoming hydraulics and returning shoes back to a place a long way (relatively) from the drums?

how can i have a 'limited travel' pedal again

John

ACTIVE8 · Unread post by **ACTIVE8** » 19 Aug 2006, 08:58

Hi jgra1

What make is the camper ?

Also how much travel is there on the handbrake ?

jeremy · Unread post by **jeremy** » 19 Aug 2006, 09:20

I think you'll find if you pull up without using the footbrake and apply the handbrake that the footbrake is slack as usual for the first application but subsequent ones are tight. As you say this is due to the brake shoes moving before they make contact with the drum - and is therefore an adjustment issue.

be careful not to get them so tight that they overheat - this can be nastier than you think if you boil the fluid - and suddenly you find that you have no brakes - especially if you don't have a split circuit.

An old trick for getting drums to work nicely is to bevel the leading edges of the linings - which helps prevent grabbing when cold and sometimes judders and noises. This can be done with a craft knife or even a wood chisel - which is handy if you want to do the job without taking the shoes out.

jgra1 · Unread post by **jgra1** » 19 Aug 2006, 09:54

thanks Active / Jeremy..

Camper is a Commer PB. I have had it 4 years or so, the last 3 it has been in a barn, rotting a little, although chassis looks very good.

Have replaced 3 of the four brake cylinders.

Re: Adjustment : Its the fact the adjuster moves the bottom of both shoes out, and I have adjusted it a fair bit (they are nearly binding) but this adjustment would still leave the clearance at the top of the shoes - where the brake cylinder and handbrake act... I can live with the pedal travel. But when you know how it could be, it's a shame not to have it..
I may try adjusting more later, after MOT, see if I can get shoes a little nearer the drums.

Handbrake cable is new, and it only needs 3 clicks to work.

Will bevel leading edge Jeremy, thanks.

John (nervous)

Clogzz · Unread post by **Clogzz** » 19 Aug 2006, 14:24

Apply the footbrake a few times after each adjustment.
That sort of ‘re-seats’ the shoes.

I always used to adjust the shoes for the slightest possible bind to get a short pedal travel, and felt the wheels for heat when arriving home, or into whatever friendly territory.
Even then, drum brakes never get as short a pedal travel as disc brakes.

And best wishes for MOT day.

jgra1 · Unread post by **jgra1** » 19 Aug 2006, 15:19

thanks clogzz;)

think i may marry the MOT guy....

He has failed on bits and bobs, should be able to do most this week, he didnt fail it on things which ( i think) he could have.. they were borderline and would have been nigh on impossible to fix;;;

Van went ok, brakes passed (in a fashion) but i want to examine all cafrefully now the van has used them, and see whats what.,
One was really binding on when i got home.. and there just is too much travel, so a really good bleed needed. I wish I could fit my 'easybleed' but the reservoir cap is wrong size

but, relieved that within 7 days hopefully i will have the paper, then i can get on with fun work

John