Increased travel/spongy on brake pedal, Vitesse

[daverclasper]

Hi. This has gradually developed in the past couple of weeks. If I release pedal and press down again immediately, it has firmed up, though a couple of seconds later if pressed again, it will be back to longer travel.

I have adjusted the shoes, no difference.

If I press down on pedal hard and hold it, it doesn't sink further and I don't appear to have lost any fluid.

Rear cylinders replaced a couple of years ago.

Only thing done on brakes recently was new front pads a few months ago.

Air in system?/Master cylinder issue?, or any other ideas please, to work on.

Thanks, Dave     

[dougbgt6]

18 minutes ago, daverclasper said:

Air in system?/Master cylinder issue?

Yes, sounds like air or hydraulic rubber starting to deteriorate. Did you overhaul the master cylinder with the rear cylinders? Worth getting a master cylinder overhaul kit, only a fiver, bleed the brakes and see where you are. You might have been unlucky with the wheel cylinders or there may be something not right with the callipers when you did the pads, but do the simples first! 

Doug

 

[Pete Lewis]

Amd reduce the front wheel bearing end float to a minimum but never  reduce it completely

Extra float pushes pads back when driving or left standing.

Also if hand brake cable has tension  and is  holding the shoes open gives a double press 

Pete

[johny]

In the end I found going to a 0.75 master cylinder was the only way to get the pedal feel I wanted....

[thescrapman]

Clamp off hoses to see it you can pin it down to a corner?

[Pete Lewis]

Dave  did the new pads have the dreaded plastic antinsqueal sticky pads.

If so remove them and fit steel ones 

Pete

[AidanT]

I've also had very similar symptoms.  The final solution I found was using a good quality master cylinder replacement seal kit. 

 

Aidan 

[dave.vitesse]

Problems with seals, brake hoses, anti-squeal shims can cause this pain. Been there, thought there was air in the system.

If it has only appeared after fitting new brake pads - Pushing the pistons back when fitting new brake pads can find a weakness in the caliper seals.

And as Pete has said, avoid the anti-squeal sticky pads.

Dave  

[Paul H]

1 hour ago, Pete Lewis said:

Dave  did the new pads have the dreaded plastic antinsqueal sticky pads.

If so remove them and fit steel ones 

Pete

Hi Pete , what do the “ dreaded antisqueal sticky pads “ look like ?

Paul

[RogerH]

21 hours ago, daverclasper said:

Hi. This has gradually developed in the past couple of weeks. If I release pedal and press down again immediately, it has firmed up, though a couple of seconds later if pressed again, it will be back to longer travel.

I have adjusted the shoes, no difference.

If I press down on pedal hard and hold it, it doesn't sink further and I don't appear to have lost any fluid.

Rear cylinders replaced a couple of years ago.

Only thing done on brakes recently was new front pads a few months ago.

Air in system?/Master cylinder issue?, or any other ideas please, to work on.

Thanks, Dave     

Hi Dave,

          this is a tip from another forum for your symptoms.

Press the brake pedal down and then jam into position with a length of wood. leave for 24 hours.

Possible cause on new calipers and may develope on older ones - the caliper piston seal becomes or is too stiff. When the piston is pushed out it deforms the seal.

When the pressure is release the seal pulls the piston back rather than simply releasing the pressure/contact.

Doing the above may allow the seal to slowly return to its normal position with the piston that bit further out.

 

Roger

[poppyman]

As scrapman says clamping off all the flexy hoses will tell you where the problem lies. With all four clamped it's m/cyl, then release one at a time untill you find which corner or corners are giving the problem   Job done.

Tony.

[Pete Lewis]

Sticky anti squeal shims are often supplied with replacement pads  its a simple flat plasticy shim which will adhere to   the pad backing

They are supposed to stop pad squeal  but dont give the relief to the leading edge of the piston as the metal ones do.

Being a compressable material they can give a spongy pedal compare to a steel shim

You may  gather I hate them 

Pete

[Paul H]

6 minutes ago, Pete Lewis said:

Sticky anti squeal shims are often supplied with replacement pads  its a simple flat plasticy shim which will adhere to   the pad backing

They are supposed to stop pad squeal  but dont give the relief to the leading edge of the piston as the metal ones do.

Being a compressable material they can give a spongy pedal compare to a steel shim

You may  gather I hate them 

Pete

Thanks Pete, just checked and  I’ve got steel shims 

Paul 

[Pete Lewis]

Thats good,

Just to add plasticy ones fit anyway up steels have an arrow  for direction of disc rotation so the relief is in the right place

Pete

[Gully]

As noted above, some of the new calipers have poor seals that don't allow the Pistons to self-adjust fully and pull back when released, giving longer pedal travel. I've had to pull the pads out of my calipers on a couple of occasions now to pump the Pistons out slightly - rectifies the problem until the pads wear a little more.

Gully

[Waynebaby]

On 11/02/2019 at 12:10, RogerH said:

Hi Dave,

          this is a tip from another forum for your symptoms.

Press the brake pedal down and then jam into position with a length of wood. leave for 24 hours.

Possible cause on new calipers and may develope on older ones - the caliper piston seal becomes or is too stiff. When the piston is pushed out it deforms the seal.

When the pressure is release the seal pulls the piston back rather than simply releasing the pressure/contact.

Doing the above may allow the seal to slowly return to its normal position with the piston that bit further out.

 

Roger

Roger,

Your tip has sorted my brake pedal travel. I've had a similar problem to Dave since fitting refurbished calipers which no amount of bleeding would resolve. 24 hours with the brake pedal held down as you suggest has restored the pedal feel. Many thanks.

Wayne

[RogerH]

Hi Wayne,

           the tip is normally used for new/recon calipers as the new seals are much stiffer than OEM.

Glad it sorted you out.

 

Roger

[Darren Groves]

On 11/02/2019 at 12:10, RogerH said:

Hi Dave,

          this is a tip from another forum for your symptoms.

Press the brake pedal down and then jam into position with a length of wood. leave for 24 hours.

Possible cause on new calipers and may develope on older ones - the caliper piston seal becomes or is too stiff. When the piston is pushed out it deforms the seal.

When the pressure is release the seal pulls the piston back rather than simply releasing the pressure/contact.

Doing the above may allow the seal to slowly return to its normal position with the piston that bit further out.

 

Roger

Another method is take out the pads and depress the pedal until the piston comes out as far as it can, but without popping out, I wedged in a thick spanner to stop this. This gets the seal back into position and stops it pulling the pain back... Just done it on aTVR with recon calipers, common problem these days.... 

Darren

 

[Nick Jones]

3 hours ago, Darren Groves said:

Another method is take out the pads and depress the pedal until the piston comes out as far as it can, but without popping out, I wedged in a thick spanner to stop this. This gets the seal back into position and stops it pulling the pain back... Just done it on aTVR with recon calipers, common problem these days.... 

The trouble with this, certainly on the new repro Type 16 calipers currently available, once the pads wear down a bit, the problem recurs.  They just don't seem to be able to self adjust properly and you have to repeat the above procedure.  There's another thread on here that covers this in detail and the update from me is that I'm now sufficiently fed up with it to have bought a used pair of OE Girling calipers to rebuild.

Nick

[GT6M]

If after all yer fart,n aboot, an still no got a good pedal,

then try thee,s tips

 

1, get yer self a solid spacer for frunt suspension, stops the shaft flexing, meks it solid.

 

2, get / mek yer self an adjustable push rod,that goes into the MC

 

3, check that yer pivot points in MC/push rod / brake pedal , clevis pin, are all ok, not worn or ovalled.

all the wee bits of wear all add up.

 

4, a Bigger MC will reduce pedal travel, but increased leg muscles will be required, no that much though.

 

5, Get 2 RPVs, one for frunts  2 LBS an one for,t rear, 10 LBS

this will keep a pressure int lines, so no let pads or what ever sneek off.

 

M

[daverclasper]

Hi, and thanks a lot everyone for brill advice.

Did Rogers tip of locking the pedal down, as simple first. I did it for 48 hours. Released it 7 hours ago and had firmed up. Still good now, though not used car, looking hopeful (thanks Roger).

Calipers are original as far as I know, and seals are at least 5 years old (since I got the car), so maybe getting hard?.

Let you know how it goes.

PS. Maybe a good idea to do this now and again anyway, to help avoid rear brake cylinder/caliper pistons etc sticking?, and also may help,  detect any seals that may be ready to fail?. 

Cheers, Dave

 

Edited February 13, 2019 by daverclasper

[Nick Jones]

3 hours ago, daverclasper said:

Calipers are original as far as I know, and seals are at least 5 years old (since I got the car), so maybe getting hard?.

The original seals last for decades.  I actually put original seals (which could have been 45 years old but were still perfectly flexible) into new calipers in an effort to get them to work properly and so far they are working much better than the ones the new calipers came with!

Did you check the wheel bearing play as Pete suggested?  Prime cause of a slightly long pedal.

[daverclasper]

Thanks Nick. Did a routine check of wheel bearings about a month ago. Had the usual amount of play. The stub axle is more worn a bit on the underside, so about 2mm of play at the rims on the vertical plane, and about 1mm on the horizontal planes.

I could check them again to see if play has suddenly increased, if locking the pedal down technique hasen't worked in the longer term. Not had chance to use the car yet.

Just wondering. Could locking the pedal down have expelled any air in the system by forcing it out up river at the M/C.

Also can air get in the system, if systems not dismantled eg, via leaks, though I'm assuming mine isn't leaking, as would have lost pressure when locked down?.

Cheers, Dave   

Edited February 14, 2019 by daverclasper

[Gully]

On 12 February 2019 at 20:41, Nick Jones said:

The trouble with this, certainly on the new repro Type 16 calipers currently available, once the pads wear down a bit, the problem recurs.  They just don't seem to be able to self adjust properly and you have to repeat the above procedure.  There's another thread on here that covers this in detail and the update from me is that I'm now sufficiently fed up with it to have bought a used pair of OE Girling calipers to rebuild.

Nick

Yep - that's my world! I have the OE calipers, but no OE seals and hadn't thought to refurbish them on the basis that the new seals would probably just render them the same as the re-manufactured calipers with new seals. 

Gully