sized front brake piston

[Efuentes]

Sorry, I meant vibrations due to an unbalanced wheel

[Lebro]

2 hours ago, david c said:

That's a nice looking piece of kit, but I think I have possibly found the answer to problem.

Being "clever" when refitting the brake pads I pushed them back as far as I could, makes sense to me so much easier to slide the callipers over the disks?

I think the problem is now I have a situation where I have to push the peddle about an inch just to get the pads to contact the disks, hence the "dead" space.

Does this theory make sense?

If so what can I do about it.?.............without removing the callipers preferably.

As said above, the pads will move towards the disk when you first push the pedal down, they will only move back a tiny ammount after that.

It's either some air still in the system, or lost movement in the master cylinder. 

Bob

[david c]

Thank you for your swift reply,

I will try bleeding the brakes one more time as it's fairly straightforward.

My reason for thinking it was what I think is called "piston roll back" is two fold

1 it fits my pet theory and seems to make sense.

2 when I press the brake pedal twice the second push is much more the mark but given a few seconds perhaps about thirty I'm back to square one...excess travel, in my mind in that thirty seconds the pistons have gone back to there start position.

[TR NIALL]

12 minutes ago, david c said:

Thank you for your swift reply,

I will try bleeding the brakes one more time as it's fairly straightforward.

My reason for thinking it was what I think is called "piston roll back" is two fold

1 it fits my pet theory and seems to make sense.

2 when I press the brake pedal twice the second push is much more the mark but given a few seconds perhaps about thirty I'm back to square one...excess travel, in my mind in that thirty seconds the pistons have gone back to there start position.

You still have air in the system you’ll need to re bleed.

[RobH]

Was there not an issue flagged some time ago about some modern piston seals being too stiff,  so they pulled the pistons back from the disc? 

[david c]

I defer to those far more experienced than I.

Having slept on the problem I am sure you are right, why would the pistons go all the way back in to the callipers? 

Simple answer jack up the front end take off the wheels and have a bl**dy look If they look like they are up to the disk then that's my silly theory out of the window. Also check the master cylinder for wear / ovality on the pin

I'll bleed the system again, sorry to be a pain

[stuart]

14 hours ago, RobH said:

Was there not an issue flagged some time ago about some modern piston seals being too stiff,  so they pulled the pistons back from the disc? 

Yes there was.

Stuart.

[Efuentes]

Hi, David. Did you take a look at the brake pads?. What’s the veredict?

[Efuentes]

This is the thread that talked about the dust seals being too rigid and pushing pistons back in, as well as other possible causes long brake pedal travel 

 

[david c]

hello Eufentes

I haven't managed to back into my workshop these last few days, cracked a rib doing another job, not a huge problem, I've done it several times before! .but it does make messing about with the TR a little "uncomfortable"

Hopefully I'll get back to it after the weekend , 

Thank you for your interest, David                  

[Michel Higuet]

On 11/17/2023 at 12:36 AM, Efuentes said:

This is the thread that talked about the dust seals being too rigid and pushing pistons back in, as well as other possible causes long brake pedal travel 

 

So for you a dust seals and caliper piston seals are the same thing?  

[Efuentes]

This is the thread that talked about the dust seals being too rigid and pushing pistons back in, as well as other possible causes long brake pedal travel 

Michel, before making such a supposedly smart remark, please read the thread I attached. It’s generally useful to read properly before commenting. While the first comment says it’s the caliper piston seals, in a later one, the commenter acknowledges he refers to the dust seals… May I add that, even if there was not such clarification, anyone that has dismantled the caliper and seen it, would understand that it would be extremely unlikely that the caliper seal, which is essentially a rubber ring with a rectangular section that seals against the sidewall of the piston, would push the pistons in, whereas if the the dust seals, that attach to the top edge of the piston, are too rigid and, therefore, hard to extend, that creates a force that pushes pistons in…

[Terry Potter]

On 11/4/2023 at 8:05 PM, david c said:

Out driving recently and became aware of a noise from front n/s brake, on examination noticed the brake was rather warmer than I feel it should be. Today I removed the calliper and found one of the pistons to be sized solid, to cut a long story short I worked out that the only way to get the offending piston out was to put back the free piston (as best I could.....about halfway) and blow them out with the airline, this worked a treat.

My questions are should I now replace both front callipers?  if so any recommendations?

Is it feasible to replace the rubber seals?  If so any tips?

Obviously to get the pistons back in the callipers they have to go in 100% square any tips on achieving this would be really helpful.

Thanks for taking the time to read this.

David

 

[Terry Potter]

Hi.

I had an experience like that back in July, smoke from from caliper seized piston, so I  replace both with new ones.

While I was at it replaced rear slaves.

Was fairly easy. 

I got a pair of calipers from a company called MFD2015. About £109.00 if I remember correctly. 

If that helps.

[BlueTR3A-5EKT]

5 hours ago, Terry Potter said:

Hi.

I had an experience like that back in July, smoke from from caliper seized piston, so I  replace both with new ones.

While I was at it replaced rear slaves.

Was fairly easy. 

I got a pair of calipers from a company called MFD2015. About £109.00 if I remember correctly. 

If that helps.

Not Big Red then?

https://www.biggred.co.uk/caliper

 

[david c]

Well back to the TR today, bled the brakes for the 4th time..................it really has made no difference, except that I now have a an empty new one litre bottle of DOT4 and one full bottle of DOT 4 that I have to get rid of. 

The new dust boots idea sounds plausible ( I bought mine from Rimmer Bros,) failing that I really am out of ideas, Am I expecting too much? do other members brakes have  much free travel before you can feel the pads contact the disks.

Thanks all for your time and patience, David

[RobH]

Are you sure it is the calipers and not excessive travel on the rear brakes you are feeling, David ?

[John Morrison]

Eliminate rear brake adjustment issus by part applying the handbrake, see what that does to teh pedal travel.

John.

[Efuentes]

13 hours ago, david c said:

Well back to the TR today, bled the brakes for the 4th time..................it really has made no difference, except that I now have a an empty new one litre bottle of DOT4 and one full bottle of DOT 4 that I have to get rid of. 

The new dust boots idea sounds plausible ( I bought mine from Rimmer Bros,) failing that I really am out of ideas, Am I expecting too much? do other members brakes have  much free travel before you can feel the pads contact the disks.

Thanks all for your time and patience, David

But, were you able to see if the pads are almost in contact with the disks?. If they are not, your issue may be the dust seals. If they are (you should see no visible gap, but the wheel should be able to turn), then the issue is either air in the system or, potentially, rear brake adjuster issues

[stuart]

If its anything its not the dust seals its the piston seals.

Stuart.

[Lebro]

14 hours ago, RobH said:

Are you sure it is the calipers and not excessive travel on the rear brakes you are feeling, David ?

+1 !

Bob

[Efuentes]

11 hours ago, stuart said:

If its anything its not the dust seals its the piston seals.

Stuart.

 

On 11/20/2023 at 12:25 AM, Efuentes said:

This is the thread that talked about the dust seals being too rigid and pushing pistons back in, as well as other possible causes long brake pedal travel 

Michel, before making such a supposedly smart remark, please read the thread I attached. It’s generally useful to read properly before commenting. While the first comment says it’s the caliper piston seals, in a later one, the commenter acknowledges he refers to the dust seals… May I add that, even if there was not such clarification, anyone that has dismantled the caliper and seen it, would understand that it would be extremely unlikely that the caliper seal, which is essentially a rubber ring with a rectangular section that seals against the sidewall of the piston, would push the pistons in, whereas if the the dust seals, that attach to the top edge of the piston, are too rigid and, therefore, hard to extend, that creates a force that pushes pistons in…

Hi, Stuart. I have not experienced the problem but, from the thread I attach above, it seems that it is the dust seals that cause the issue. If you read the thread, you will see that the person that pointed to the piston seals acknowledges that he meant the dust seals. As I also point in the attached comment, it is difficult to see why the piston seals would push the pistons in, as they only press the pistons in the sidewall (if at all, they would make the movement of the pistons hard, but not push them in), whereas, if the dust seals are too rigid and hard to extend, with them being attached to the top of the piston, I can imagine that they would exert a force that would push the end of the piston back into the caliper… in other words, it makes sense to me that it is the dust seals and it does not that it would be the piston seals, and the attached thread supports that view…

 

 

[John Morrison]

If, applying the handbrake say two/three notches doesn't reduce the pedal travel, and therefore rear brake adjustment is not the issue,

then to prove the point, I would 

pull the calipers and refit without the dust seals, you'll know then one way or the other.

John.

[Z320]

On 11/15/2023 at 12:14 AM, RobH said:

Was there not an issue flagged some time ago about some modern piston seals being too stiff,  so they pulled the pistons back from the disc? 

The seals always have to pull back the pistons a a small amount.

This should reduce with not elastic (stiff?) seals.

Ciao, Marco 

[david c]

Thanks all for your suggestions, I really do appreciate your advise.

When I look at the pistons they are 1/4" back from the disks both sides both disks, this is what leads me to suspect the new bellows type bust covers.

I did all the bleeding with the hand brake on, is that wrong? in point of fact I had to back of the rear shoes one notch as they were binding very slightly with the hand brake on.

I do not understand how the piston seals could cause this problem, could you explain why they might please.

I am quite prepared to take off the callipers  and try the pedal travel without dust covers, but first I have to get more DOT4 and possibly another set of dust covers from an alternative source (recommendations welcome) alternatively should I just bite the bullet and buy complete new callipers? once again recommendations welcome. I would rather not go the junk and replace route it goes against the grain and I have read of some bad reviews of new callipers.

thanks all David