Speed 25 brakes adjustment

For Speed 20, Speed 25, 3.5 Litre and Crested Eagle cars
johnlayzell
Posts: 113
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Speed 25 brakes adjustment

Postby johnlayzell » Tue Oct 06, 2015 3:49 pm

I have new soft brake linings front and rear. I have new rear brakes cables installed. I have adjusted the brakes according to three separate but similar instructions from the Speed 25 handbook and elsewhere, and, with the handbrake off, there is the slightest of drum dragging against the linings on all four wheels.

Both central wing nut adjusters remain slacked off to the fullest possible extent, as none of the instructions mentions to tighten them after the individual drums have been adjusted.

However, when I depress the brake pedal it travels almost all the way to the floor before any pressure is felt. This with the car still up on jack stands and engine not running. The brake servo is connected and adjusted according to the article “THE CLAYTON DEWANDRE BRAKE SERVO” in Bulletin 394 of July 1991 - as best as I can understand it!

What am I missing here?

All advise and suggestions welcome!

With thanks!
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

DaveT
Posts: 93
Joined: Tue May 22, 2012 12:53 pm
Name: David Turnage
Location: Colchester, UK

Re: Speed 25 brakes adjustment

Postby DaveT » Wed Oct 07, 2015 12:54 pm

how about one or more of the drums being oval?

I asked a question about this before but got no response.

viewtopic.php?f=16&t=450

I changed one of my drums (with another 2nd hand one) and got a much better result for run out and subsequently for the adjustment of the brakes.

I appreciate that turning the drum around may introduce an error but if this the case you will get a sine wave type error over one turn of the wheel, whereas ovality will create two high and two low spots per rev (in general).
Dave T
Colchester, UK
sp25 DHC
Jensen 541

chhym
Posts: 34
Joined: Fri Mar 21, 2014 12:35 pm
Name: Chris Hyman

Re: Speed 25 brakes adjustment

Postby chhym » Wed Oct 07, 2015 2:01 pm

I doubt having oval drums would cause this amount of free play in the pedal.

Not having the engine running means that the servo won't be in operation although it will go "through the motions".
I suspect once you get the brakes correct, then you may have to go back and adjust the servo.

Having a read of the instruction manual.

Back off central wing nut adjusters.
Adjust the adjusters on the front brakes.
Click the handbrake on two clicks.
Adjust the adjusters on the rear brakes.
Job done.

Now real world:
From memory clicking on the handbrake two more notches locked up wheels completely when setup correctly, although I do remember that it took me many tries before I got the adjustment happy as you have to get the cable length correct as well as the adjusters on the back and it was the cable length where I had the problems, so I went backwards in the adjustment.
IE:
Get the adjusters on the back of the drums correct as you have with the shoes just touching/dragging.
As these are new linings you may have to have them dragging slightly more until they are settled in.

Click the handbrake on 4 notches.
Adjust the front cables a turn or 3 each side in turn until the brakes are locked on, or at least very very hard to rotate the wheels.
Release the handbrake - can you turn the front wheels at all?
No - back off the cable adjustment slightly for each wheel.
Yes.. do they drag about the same as before?
Yes - do the same on the back with the handbrake on slightly more and you should be all good.
No - Its is less than before?
Yes - re-adjust the back plates and start again.
No - Try and balance the back plate adjustment and cable adjustment until you are happy (this is the hard bit).

I have also been told that you sometimes need to shim the shoes to make then sit at 90deg's to the back plate as obviously if they are not at 90deg the first part of the brakes going on will be used up by the shoes moving to 90degs to the back plate.

Hope this helps.


Chris

johnlayzell
Posts: 113
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Re: Speed 25 brakes adjustment

Postby johnlayzell » Tue Oct 20, 2015 2:40 pm

Thank you Chris & Dave!

I took a break from the car and will resume this week. I will post my results.
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

johnlayzell
Posts: 113
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Re: Speed 25 brakes adjustment

Postby johnlayzell » Sat Oct 24, 2015 4:13 pm

Mission accomplished! Thanks Chris & Dave.

What none of the various brake adjusting articles/posts mention is that after fully adjusting the brakes as described, one has to tighten the foot and hand brakes adjusting wing nuts.
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

chhym
Posts: 34
Joined: Fri Mar 21, 2014 12:35 pm
Name: Chris Hyman

Re: Speed 25 brakes adjustment

Postby chhym » Mon Oct 26, 2015 6:05 pm

thanks John for the update.

RichardWallach
Posts: 274
Joined: Mon May 21, 2012 10:14 am
Name: Richard Wallach
Location: Melbourne, Australia

Re: Speed 25 brakes adjustment

Postby RichardWallach » Tue Oct 27, 2015 7:21 pm

Gentlemen,

It would be handy if an article on this subject was written for The Bulletin.



Richard
Melbourne

johnlayzell
Posts: 113
Joined: Mon May 21, 2012 2:44 pm
Name: John Layzell

Re: Speed 25 brakes adjustment

Postby johnlayzell » Thu Dec 15, 2016 3:47 pm

Over a year after I announced 'Mission accomplished', I realize I was being overly optimistic and confidant.

The brakes survived a 583 mile drive this past October, but not without a few moments of angst!

I had another go recently and now they are actually worse than before I tried to improve! The correct adjustment of the adjusters on the back of the drums (front top/rear bottom) continues to mystify somewhat.

Also, if we start by fully backing off the two central wing nut adjustments, after every other adjustment has been made, what do we do with them after every other adjustment is made?

Appreciate further input!

Thanks!
1925 SC12/50
1937 SP25 VDP Saloon
1970 Peking to Paris Rally VW Beetle

chhym
Posts: 34
Joined: Fri Mar 21, 2014 12:35 pm
Name: Chris Hyman

Re: Speed 25 brakes adjustment

Postby chhym » Fri Mar 10, 2017 2:42 pm

Shame it did not work out.

My car has been away for many many months so have not had a chance to fiddle.

Having a read of the manual the central nuts are used to adjust the brakes every few thousand miles or between major adjustment.
As you have new linings could some of the wear be due to:
1) they are bedding in?
2) they are soft lining therefore wear slightly quicker?

The manual does say 200-300 miles to bed the brakes in so as you are nearer 600miles maybe its expected.

The other option is take the car to a specialist as ask them "what am I doing wrong!"


Chris


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