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Groove on Front brake discs


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Recently stripped the front brakes and suspension for refurbishment, new bushes etc.

However the front disc on both sides has a groove worn in the middle of the disc on the rear face.

The pad also has raised section mirroring the grove. It is about 0.5mm deep by 6mm wide.

Does anyone know what could have caused this?

 

Many thanks

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If it was one side it may be possible for a trapped small piece of stone or grit to have grooved it, both sides of the disc in about the same area I'd say it's likely there's a fault in the make up of the disc material causing a softer area and excess wear.

 

Mick Richards

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I thought that groove occurred when the steering stop cam was not adjusted properly or is missing. This means that the full lock goes too far and the disc catches part of the front suspension. It happened on my wife's TR6 before I adjusted it.

 

 

Cheers John

Edited by John390
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Lock stops missing?

 

I do not think TR 6 has adjustable lock stops like the eccentric things fitted on TR 2/3.

 

Cheers

Peter W

 

PS. Or very worn trunnions and bushes perhaps.

Edited by BlueTR3A-5EKT
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Hi, I have exactly the same marks as Pedlar17. I also read that the end stops were not correctly adjusted. So put my car up on 4 pillar hoist and moved steering lock to lock and inspected.

 

Could not see anything that looked adjustable as a stop, but did see that one of the trunnion lower link split pins was rather close at end of lock. So re-shaped/moved the end of the pin.

 

If anyone could please clarify what these end stops look like that would be handy.

Thanks and cheers,

J..

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Hi James,

as stated by John, they are a small disc of steel apprx 5/8"diameter and 1/4" thick.

They are bolted to the TRunnion with a 1/4"unf bolt.

As the TRunnion rotates the disc will hit a stop on the TRunnion and that gives the limit of full movement

 

http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=2789#78 item 78.

 

Roger

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Posts 16 onwards here covers the lack of lockstop causing grooving:

http://www.tr-register.co.uk/forums/index.php?/topic/49030-anti-roll-bar-poly-bushes/

photo on post 22 shows where lockstop should be screwed in.

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Q: Does the lock stop on your car actually hit up against the tab on the base of the V post when the trunnion is rotated L to R? If not a taller lock stop might be required - the early car lock stop was half the height of the 15611 TR6 item. Perhaps a pile of washers of a larger diameter than the existing lock stop could be substituted.

 

 

Parts History Time for us Anoraks

 

142403 was the eccentrically drilled lock stop spacer tube fitted TR4A-5-250 & TR6 (as fitted on 1969 models only pre CC/CP50000 - no comm number change point given) This was adjustable to give max steering lock without impingement of parts.

 

156111 was the concentrically drilled lock stop spacer tube fitted TR6 - no engineering change point is given but 1970 build or CC/CP50001 onwards could be a reasonable guess. This was not adjustable so the max steering lock is fixed.

 

Cheers

Peter W

 

PS Just a thought - which way up are your lower wishbones fitted - the eye should droop down both ends when fitted. Is this a possible cause? They can be fitted both ways - if the inner stud is removed and the hole is through threaded. No flat machined on the upper face inner stud hole though. Lowering trick from all accounts.

Edited by BlueTR3A-5EKT
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I had the same problem-mysterious groove on the rotor. The trunnion bolt head or nut was contacting the rotor on full lock. I made a steering stop collar sligtly larger to prevent contact as the existing collars were drilled concentrically. Grinding or machining the bolthead or nut would have been another solution. Be sure to check full lock in both directions on both wheels.

Berry

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I had the same problem-mysterious groove on the rotor. The trunnion bolt head or nut was contacting the rotor on full lock. I made a steering stop collar sligtly larger to prevent contact as the existing collars were drilled concentrically. Grinding or machining the bolthead or nut would have been another solution. Be sure to check full lock in both directions on both wheels.

Berry

That is very often where the problem arises. I have come across instances where even with eccentric stops fitted the trunnion bolt will still touch and it can be down to moving the split pin and nut round a little.

Stuart.

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I think you might be right. It may be the bolt head.As all bolts were pretty knackered.

 

The stop plate on my car is concentric there is no adjustement it is an early uk 72 .

When I reassemble I will check the bolt heads.

 

Thanks everone.

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