Jump to content

Recommended Posts

I still have this perennial long brake pedal. Just recently changed my EFI original throttle bodies to the excellent Jenvey Heritage throttle bodies which look like Webbers but have trick injectors inside.I used the Webcon USA made one piece inlet manifolds which has max vacuum for the servo and it feels it. Any way I digress. When reversing in a straight line then braking, then driving forward and braking nice firm brake pedal. Tried this a couple of times and same result.

Now tried it again with turning the steering wheel to the left and then to the right, then braking going forwards, long brake pedal so narrowed down to the front area.

I had this when first put back on the road with standard all new parts.

I uprated everything including four pot callipers, vented disc's CDD alloy hubs with bigger stub axles and bigger bearings, Changed the trunnions yet again with a much better set.

All poly bushed and everything renewed.I rebuilt my TR5 with a high quality best of parts available with no expense spared yet still have this niggling problem. I can not get it on to my Two poster till next week to investigate where I know it is the fronts only so hope to pin point it at last. I have lived with it since 2004 one stab of the brakes and it is fine.

It is mechanical but what is it. Anyone come across with the same problem?

Be kind. I have fully rebuilt a few and mine is the only one to act like this.

Regards Harry

20210111_135835.jpg

Link to post
Share on other sites

Have you checked those residual pressure valves are the right ones and working? What calipers have you got on the front?

Stuart.

Link to post
Share on other sites

Thanks for the reply Stuart.

I removed the internals of the residual pressure valves as I did not like the way it worked.

The callipers are Hi Spec.

I have the same problem before I uprated everything and still the same.

I do like to drive on track days and the brakes in very hard use have no brake fade whatsoever

Regards Harry

Link to post
Share on other sites
5 minutes ago, harrytr5 said:

Thanks for the reply Stuart.

I removed the internals of the residual pressure valves as I did not like the way it worked.

The callipers are Hi Spec.

I have the same problem before I uprated everything and still the same.

I do like to drive on track days and the brakes in very hard use have no brake fade whatsoever

Regards Harry

I have heard of problems with long pedal on Hi-Spec calipers before, Guy (Jersey Royal) took them off his TR6 as he was having similar problems. AP calipers are a much better bet. The residual valves would go some way towards stopping that problem which is what they are for.

Stuart.

Link to post
Share on other sites

Hi Harry,

That set-up looks the biz !

Whilst I cannot offer any ideas to remedy, I run the Cannon inlet manifold (like you) ? With Jenvey throttle bodies and AP 4 pot calipers, with the appropriate Ford Escort Cosworth vented discs etc, and have a nice, firm, and short pedal.  Also using the uprated hubs, alloy hubs, bigger stub axles and modern, larger Timken bearings.

Interesting to hear about another car with this issue using those calipers ?

 

Good luck.

 

Cheers.

Link to post
Share on other sites
2 hours ago, stuart said:

I have heard of problems with long pedal on Hi-Spec calipers before, Guy (Jersey Royal) took them off his TR6 as he was having similar problems. AP calipers are a much better bet. The residual valves would go some way towards stopping that problem which is what they are for.

Stuart.

Yep and a pain to sort out at my place took half a day pressure bleeding it to get the right pedal 

Link to post
Share on other sites
1 hour ago, TRTOM2498PI said:

Hi Harry,

That set-up looks the biz !

Whilst I cannot offer any ideas to remedy, I run the Cannon inlet manifold (like you) ? With Jenvey throttle bodies and AP 4 pot calipers, with the appropriate Ford Escort Cosworth vented discs etc, and have a nice, firm, and short pedal.  Also using the uprated hubs, alloy hubs, bigger stub axles and modern, larger Timken bearings.

Interesting to hear about another car with this issue using those calipers ?

 

Good luck.

 

Cheers.

You have the right calipers there Tom. The AP ones though expensive are the right tools for the job.

Stuart.

Link to post
Share on other sites

Indeed if I was buying now I'd get the AP calipers, but the HiSpec 4 pots I have on my TR4A serve me really well and function flawlessly, however i should add that they were fitted in 2007 as part of the then Revington upgrade kit which included new rear drums (Alfin).  They do however appear to be a different design to the current Hispec offerings.

20200812-P1050019-2.jpg

Link to post
Share on other sites

Probably the same as mine Colin as I fitted the Hi Spec the same year.

I must admit I would prefer the AP callipers but these days I believe it is just a name and made by all and sundry. At over a grand an expensive mistake if it was not the problem.

A few people I know have fitted Hi Spec with no issues.

I can not remember if the brake residual valves solved it but pulled out the guts as I did not like the brakes binding slightly.These are designed for kit cars with a lower master cylinder so I believe.

It lies somewhere in the front and until I get to it next week to strip down I am fishing for answers.

Could be staring in the face but .....

Regards Harry

One for Tom below.  Cosworth Escort discs  and AP Callipers can you PM me a price. 

20201227_161543_resized.jpg

Link to post
Share on other sites

Hi Harry,

You may remember  i had same pedal issue with the replacment calipers fitted during the rebuild on my 6. Later  I replaced these with AP 4 pots and vented discs and the long pedal didn't change, but brakes are fine on track

Mark

Link to post
Share on other sites

Hi Harry,

Looks like you have done the obvious things.

Since you have a firm pedal when going in a straight line, and the issue starts when you start turning left and then right, it looks to be related to that (think we all agree).

Apparently this movement does “something”. For me, most likely source is sideward (lateral) movement between disk and caliper(s). This pushes the caliper pistons back a bit. A longer pedal represents very little fluid si it is not easy to detect/measure. Can you get feeler gauges between pads and disk on your calipers? If needed with wheels removed. And measure all 4 clearances? It may point you to the culprit area. Then compare what is different.

It could well be insufficient stiffness of the way the entire construction.

Good luck,
Waldi

Link to post
Share on other sites
3 hours ago, Waldi said:

It could well be insufficient stiffness of the way the entire construction.

Good luck,
Waldi

Thats the problem, slight distortion causes it.

Stuart.

Link to post
Share on other sites
13 hours ago, harrytr5 said:

I can not remember if the brake residual valves solved it but pulled out the guts as I did not like the brakes binding slightly.These are designed for kit cars with a lower master cylinder so I believe.

 

 

The whole point of the residual valves is to maintain a little pressure in the lines, not just for kit cars. If you fit the correct valves (they are set differently for fronts and rears) they work very well. They were developed for NASCAR racing.

Brake line valves

Stuart.

Link to post
Share on other sites
5 minutes ago, harrytr5 said:

Stuart,

Fitted the right way round. 2lb fronts and 10lb rear and fitting in the right directions. Did not like the drag on the brakes so removed the innards.

Thanks everyone, for the replies.

Regards Harry

Can I suggest you retry them, there shouldnt be any drag if set up OK.

Stuart.

Link to post
Share on other sites
2 hours ago, stuart said:

Thats the problem, slight distortion causes it.

Stuart.

How does that explain that the knock-back happens when there is no brake pedal pressure applied? Harry says it happens after maneuvering back & forwards without braking. I’m quite willing to accept that the residual valve solution will work, but it sounds to me like the problem is with the stub axles, not the calipers.

John

Link to post
Share on other sites

The problem was there when all rebuilt, hence chasing around in circles fitting uprated beefier better quality parts with out finding the cause. My TR5  (Jas)gets what it needs even if it does not know it. I built a concourse winning TR5 (Rooster)to factory standard and fabulous to drive but after that could not change anything as wanted to keep standard. After three years of driving around I got frustrated as I wanted to change things so I sold on to a friend. Perhaps I should leave things alone. Jas is more me and drives like no other TR5 with all the mods I have done on it. Still got that soppy grin when I take Jas out.

Yes the braking is an irritant and I have put up with it for years but would now like to find out why.

Thanks for the replies and helpful advice.

Mark, strange yours still does it after fitting AP, perhaps it is me.

Regards Harry

Link to post
Share on other sites

When i fitted Toyota 4pot calipers to my 6, back in anout 2013! , my brake pedal travel did increase.

i noticed two types of increase, permanent and transient.

permanent longer pedal travel is accounted for by the change in hydraulic ratio, from the slightly larger caliper piston area.

transient long pedal seemed worse after reversing/manouvering, and i think this is caused by flexing of the hubs allowing the disk to twist and move the pads back

i fitted CDD’s big hub kit and this did make some difference but was not a 100% cure

the toyota calipers are solid iron items so i doubt they flex in gentle reversing.

 With 4 pistons spaced apart they are perhaps more sensitive to any twisting of the hub or other suspension ‘bending’?

steve

 

 

Link to post
Share on other sites

Have you set up the wheel bearings with factory endfloat?

If you have try tightening them just enough to remove the endfloat and that should cure it.

All my Triumphs will fail the MOT on loose bearings with the factory end float and I gave up trying 30 years ago. Pad knock back is a symptom of loose bearings.

Neil

Link to post
Share on other sites
5 hours ago, Stagpowered said:

Pad knock back is a symptom of loose bearings.

I think that's why the Revington upgrade worked on my car. The stiffening tube also acts as a spacer against which you torque up the nuts (and bearings). Shims are used to get the end float just right. A bit of a fiddle to set up, but very effective.

John

Link to post
Share on other sites

Yes we all know about knock back due to flex but if you read the OP you will see he has the larger stub and bigger bearing kit fitted which then to me points to caliper problem.

Stuart

Link to post
Share on other sites
21 minutes ago, stuart said:

Yes we all know about knock back due to flex but if you read the OP you will see he has the larger stub and bigger bearing kit fitted which then to me points to caliper problem.

Hi Stuart,

Yes, I saw that but I'm trying to understand how the callipers can be the problem when they haven't even been loaded. Are 4-pot callipers more sensitive to knock-back? In other words, might they still suffer the problem even with stiffer stubs etc.?

Not questioning your judgement, just trying to understand rather than blindly accept.

John

Link to post
Share on other sites
1 minute ago, JohnC said:

Hi Stuart,

Yes, I saw that but I'm trying to understand how the callipers can be the problem when they haven't even been loaded. Are 4-pot callipers more sensitive to knock-back? In other words, might they still suffer the problem even with stiffer stubs etc.?

Not questioning your judgement, just trying to understand rather than blindly accept.

John

Talking to Darryl at Racetorations about this when Guy had the problem with his he reckoned the calipers being light alloy distort slightly hence they recommend AP http://www.racetorations.co.uk/triumph-c56/tr3-c4/tr3-brakes-c31/racetorations-kit-vented-disc-p515

Stuart.

Link to post
Share on other sites
On 1/21/2021 at 12:25 AM, Mark V said:

Hi Harry,

You may remember  i had same pedal issue with the replacment calipers fitted during the rebuild on my 6. Later  I replaced these with AP 4 pots and vented discs and the long pedal didn't change, but brakes are fine on track

Mark

I could accept that Stuart but Mark had that problem and when he changed to AP he still gets it. I do not know if he experiences the same as I do though.

I now have my TR5 on my two poster with the wheels off trying to study what is happening and where might be the problem.

All good fun and lock down has its plus sign's.

Regards Harry

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.