Likely TR3a calliper problem

[Markboston]

Dear TR universe experts,

I would be very grateful for views or pointers on a problem that has just arisen on my otherwise perfectly behaving TR3a. Its serial number is in the 73,000s. The front callipers discs and pads have been overhauled in its recent history (but not by me) and seem very clean and in good order. 
But the car suddenly developed a most unsatisfactorily large swerve to the offside upon harder brake application, particularly at higher speeds. After a run, the O/S calliper felt appreciably hotter than the N/S, possibly suggesting inaction on the N/S.

I would like to know if this is a frequently found problem, and if so, is there a ‘usual’ cause.
My first step would be to bleed for air. There is no noticeable fluid loss. Applying the handbrake only does not seem to lock the rear wheels although on heaviest possible  foot braking the N/S rear wheel will lock first.  I do not know whether this would be likely to add to, or alone cause, the O/S veer. 
 

Many thanks in advance for your kind considerations, 

Mark B 

 

g

 

 

[Lebro]

have you recently greased the front suspension ? if so it is possible some grease may have got onto the brake disk on one side - this can have a dramatic effect.

(Don't ask me how I know!)

Otherwise it could be worn out pads on one side, or sticking pads on either side.

Bob

[Motorsport Mickey]

The disc braked front works much more efficiently (or should do) over the brake drummed rear axle. As an example I blew a rear oil seal within the axle during a race which upon examination afterwards covered the brake shoes upon that side heavily with oil. Although aware there was something amiss when racing I still maintained the same lap times (not driving hard enough said my mechanic) which agrees that braking is normally something like 70% from the fronts and 30% on the rear.

If you can lock up a rear wheel first before the front's, using the foot brake, there is definitely something wrong with the operation within the system. Under normal circumstances you should always lock the front first, there's no "usual" cause, faults can appear and the best way is to examine the operation of each calliper on the front and brakes shoes on the rear separately. You may need a friend or partner to operate the brakes, (foot and hand brake) whilst with the "corner" jacked up, you turn the discs at the front or drums at the rear feeling to see what braking effect you find there. Obviously where the braking effect is weakest deserves to be inspected further.

Mick Richards        

[Markboston]

Thanks very much for that. From what you say seems very much like issue at fronts and will try to test as suggested.

[Drewmotty]

A good reason to have our Historic Vehicles MOT checked every year. It’s very difficult for the average driver (me) to assess brake balance/efficiency from the driving seat. 

Edited March 18, 2023 by Drewmotty

[Ralph Whitaker]

12 hours ago, Markboston said:

Dear TR universe experts,

I would be very grateful for views or pointers on a problem that has just arisen on my otherwise perfectly behaving TR3a. Its serial number is in the 73,000s. The front callipers discs and pads have been overhauled in its recent history (but not by me) and seem very clean and in good order. 
But the car suddenly developed a most unsatisfactorily large swerve to the offside upon harder brake application, particularly at higher speeds. After a run, the O/S calliper felt appreciably hotter than the N/S, possibly suggesting inaction on the N/S.

I would like to know if this is a frequently found problem, and if so, is there a ‘usual’ cause.
My first step would be to bleed for air. There is no noticeable fluid loss. Applying the handbrake only does not seem to lock the rear wheels although on heaviest possible  foot braking the N/S rear wheel will lock first.  I do not know whether this would be likely to add to, or alone cause, the O/S veer. 
 

Many thanks in advance for your kind considerations, 

Mark B 

 

g

 

 

Mark,  how long ago were the calipers overhauled? , and has the car had much use since?. Has this swerve only occurred after a winter lay up?   Rust can build up in the caliper preventing the pads from moving freely, not just on TRs, this can affect more modern machinery too, then when the brakes are applied harder it can overcome the rust and force the pad into contact with the disc.  If it were mine I would be whipping the front wheels off and checking that the pads are free and the pistons can be pushed back into the bores , ie not stuck. If all seems OK it could be that the flexy hose is collapsing internally and preventing the n/s caliper from working .

Ralph

Edited March 18, 2023 by Ralph Whitaker
Additional thoughts

[Motorsport Mickey]

4 hours ago, Drewmotty said:

A good reason to have our Historic Vehicles MOT checked every year. It’s very difficult for the average driver (me) to assess brake balance/efficiency from the driving seat. 

Don't forget to take it in weekly then, remember the MOT is only confirmation that at the time of inspection the vehicle met the appropriate standards. If a week (or even a day) after the MOT you are involved in an accident which involved you failing to stop in time a police or MOT station will test your brakes and if they don't meet MOT standards then you will be prosecuted. There will be no mitigating circumstances taken into account in court, the judge or magistrate will merely say "not meeting MOT braking requirements at the time of accident" and sentence you appropriately,...Oh no ! what are you to do ? 

After your MOT you drive the car about 50mph and brake hard enough so the front brakes lock up and the car doesn't divert in any direction. Appraise and calibrate yourself as to what is "correct amount of retardation" I have a road with a good surface which I use for brake tests, couple of hundred yards of straight with not too much camber. That's what garages used to do before they needed a rolling road, they would carry a Tapley meter on the passenger floor which gave a measure of retardation. Your personal and subjective retardation judgement should instead be calibrated by feel against it. If after a couple of months if it continues to stop in a manner you are familiar with having driven it since it's MOT then the brakes are still OK, if not you investigate and repair replace what's not correct. I use a similar method for the rear brakes also, using only the handbrake to slow the car, as said the rear brakes work much less slowly and to a lesser effect so I check on how effective I feel the mph reduction is. It's all subjective but unless we want a weekly MOT it's as good as it gets. 

Am I the only driver to occasionally jump on the brakes of the modern daily use cars I have (after warning the missus and making sure the cream cake is secured) to check the ABS operation and "feel" for the pulsing under the brake pedal confirming it's operation, ? or turn off traction control or EPS and make subjective judgements about their effectiveness ? As an older driver it's what I do to ameliorate the risks of a failure in systems that when you need them...really need them to work.

Mick Richards

Edited March 18, 2023 by Motorsport Mickey

[stuart]

1 hour ago, Motorsport Mickey said:

Am I the only driver to occasionally jump on the brakes of the modern daily use cars I have (after warning the missus and making sure the cream cake is secured) to check the ABS operation and "feel" for the pulsing under the brake pedal confirming it's operation, ? or turn off traction control or EPS and make subjective judgements about their effectiveness ? As an older driver it's what I do to ameliorate the risks of a failure in systems that when you need them...really need to work.

Mick Richards

Mine get checked pretty often on the way into work as theres a manhole cover on a curve up through the village and the numpties that live there park just round the blind bend so you often find you have to suddenly stop when someone pulls out of a side turning halfway up the line of cars and the manhole is right at the braking point. Thats when you`ll feel the ABS.

Stuart.

Edited March 18, 2023 by stuart

[Markboston]

Ralph, Thank you. I shall do this too. The car has had only occasional and overly-light use over winter. Yes, the swerve just appeared on perhaps its first good-weather run for weeks  Perhaps prior short trips on damp and still-salty roads have allowed for corrosion. 

[Motorsport Mickey]

2 hours ago, Motorsport Mickey said:

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Edited March 18, 2023 by Motorsport Mickey
duplicate

[DesNoble]

Do you know how many miles your pads have done. Sometimes when they are new they are a little tight, rub and get hot. I've had discs glowing before now with new pads. Not on the TR. Try driving a short distance without using the foot brake, and then stop gently, possibly with the hand brake, and see if the brake is getting hot. I would also test the brakes on an empty road or empty carpark by applying them progressively harder to see what happens. You don't have to be going fast you just need some space and no traffic. If they seem ok hit them as if you were doing an emergency stop just to satisfy yourself that if they were just sticky from being laid up that they were now clear. If they still pull to one side then I'd do as Ralph said above.

PS If they do get so hot that they glow drive slowly without touching them to cool them down otherwise they might warp the discs or even seize. 

[Trev Good]

Not on my 3a, but on my Scimitar (which has similar suspension and brakes as a TR).....I had a very similar problem following my restoring it.

After I had fitted new calipers and pads, new discs and lost a lot of hair, I suddenly thought about how I had restored the brakes!.......... I had used brake hose clamps. I then tried new braided hoses and, voila, all perfect....the clamp on the offside had seized the hose. So, after £400 of new parts, loads of time and hair pulling.....it was cured with an £8 part!

[TimG]

On 3/21/2023 at 6:44 PM, Trev Good said:

Not on my 3a, but on my Scimitar (which has similar suspension and brakes as a TR).....I had a very similar problem following my restoring it.

After I had fitted new calipers and pads, new discs and lost a lot of hair, I suddenly thought about how I had restored the brakes!.......... I had used brake hose clamps. I then tried new braided hoses and, voila, all perfect....the clamp on the offside had seized the hose. So, after £400 of new parts, loads of time and hair pulling.....it was cured with an £8 part!

I agree brake hose clamps seem a good idea but not in practice. I used them in removing the rear axle on my 1930 Sunbeam to fix broken half shaft. On  reassembly I thought better of it & got new hoses.

I have a Tapley brake tester bought when a local garage closed down