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Triumph TR6 - Rear Brakes Pulsing

Hey All,

This is probably a no brainer, but I have probably asked dumber questions.

My left rear brakes seem to be grabbing/pulsing when I step on the brakes. It is pretty subtle. (No, I haven't installed ABS.) I am thinking my brake drums need to be turned (is that the right word?), but could my shoes also be on the fritz? There is about 3/16 of stuff left on the shoes.

And every now and then my E-brake seems to get stuck and not release on this corner until I try to move. Could this be related?


Ignatius Rigor

It does sound like your drum is not round. If one of the shoes isn't retracting after use of the parking brake the symptoms would be worse until it freed up.

My drums came off real easy...
that's because...
My DPO had the OD lockout switches overridden and he backed up in OD causing all sorts of shudders that he figured must be brake problems! He has the rears rebuilt 3 time in 2,000 miles!
Hard to believe, but the OD survived!

Back to your issue Ignatius, if your drums have never been turned (resurfaced?) you should be able to have it done and dramatically improve the situation, if not correct it altogether. I've never had shoes cause a pulse in the pedal. Bent wheels or suspension, yes. But not shoes!

Good luck!
EC Smith

Not sure how you can tell its the left rear..but it is possible the drum may be out of round and need turning, you can likely solve the parking brake problem by ensuring the cable is free to move. Also check wheel cylinders.

Try this....while going straight ( open road or empty lot..not gravel ) get up to a nice speed and use only the parking brake to start slowing down. If you get the pulse or a regular thumping that you feel in your butt in the seat (I hope your butts in the seat) then that's indicative of the drums being out of round.One drum can be out more then the other and/or your brakes are not set up equally.
Most places offer drum turning for a few $$..if you take them in yourself.
If you do get them turned try not to stand on them to hard for a few days till the settle in or you can make them out of round again..remember when they are turned a few thousands of an inch of drum is taken off making them slightly thinner till eventually you have to replace them.


Charlie Ballard

Thanks for all the thoughts!

I guess I am not sure if it is the left drum that is causing the pulsing, but it is definitely the left brake that is sticking when I release the parking brake. I will try braking with the parking brake and see if I get the thumping.

The brake drums are almost a half inch thick. What is the minimum thickness to turn down to before buying new ones?

Ignatius Rigor

There is usually a "max dia" dimension cast on the outside of the drum.
Brent B

Most shops will not turn drums to a diameter larger than the maximum. My opinion... there is a safty factor included but why risk it. Drums shouldn't be too pricey.
EC Smith

Check that the locating screw drum to hub is there snug and isn't broken? Look for any brake fluid dampness.

The max is calculated by the amount the mechanical action can push out the pads. Measured with inside calipers to surface. Unless you have realy high milage their OK to turn. Old cars had lots of room built in. Do both and replace pads.

Most parts stores do turning automated. But if you have an extra minute find a pro or specialty machine shop. Might cost 2 bucks more but you will be happier. Carbides are usually sharper. So's the kid turning?

Overall I bet on leaking brake fluid. Could be cable or rusted mechanicals?
Bill Brayford

Hi Bill,

I am trying to figure out how leaking brake fluid figures into this. I did have a brake fluid leak from the same side that I think is pulsing, and replaced both rear cylinders a couple months ago. I did have the pulsing before that too. I cleaned everything up as well as I could when I replaced the cylinders. Could the break fluid that leaked hurt the pads?

I will replace the pads as suggested by others.

Ignatius Rigor

Hi Ignatius

Got your e-mail earlier today and responded before I seen this post. So I will give a quick response here as well.

Brake fluid will soak into pads. Heating and cooling as brakes do even the metal drum gets a bit contaminated. Something like re-oiling an oilite bearing for the techie crowd? It will cause less noticable problems when the leak is still there. Afterwards brake pads will tend to glaze and stick.

Do what you mailed . Replace pads/turn drums and clean all surfaces up with a good brake cleaner/clean rags.

Bill Brayford

This thread was discussed between 25/11/2003 and 03/12/2003

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