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Poor Brakes? Check your Caliper Mounting Plates!


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My Vitesse has never had what I'd call fantastic brakes, but along with I suspect many owners I put this down to my being used to modern servo assisted ABS equipped modern brakes.


I'll try to cut a longish story short here. I recently fitted a new set of calipers to the Vitesse following discovering a ceased piston in one of my originals and realising that they had been very poorly rebuilt in the past. 


After fitting the new calipers I experienced a long, spongy pedal and very poor braking. Closer examination showed that the left caliper was not locating parallel to the disc causing one pad to reach the disc first but more worryingly then causing the caliper mounting plate to flex and the caliper to move laterally.


With originals no longer available I contacted Canley Classics about their aluminium plates, the chap on the phone was very helpful but said he didn't believe that the original bracket could bend or flex without braking as it was cast iron and wasn't happy to sell me their plates without further investigation.


Several other "experts" and "specialists" expressed the same opinion, in fact the phrases "I've never seen that in all the years I've worked on Triumphs" and more significantly "they all have poor brakes", became very familiar to me.


I got the Canley plates anyway and fitted them today and yes BOTH the original caliper mounting plates were bent just beyond the bolt holes attaching then to the rear of the upright. 


As they came off easily and showed no sign of any other damage I have to assume that this is due to ceased or sticking caliper pistons causing side thrust on the calipers and in the right circumstances cast iron DOES bend,


With the alloy plates fitted the calipers run true and the disc is centered in them, there is no flex or movement of the calipers and the brakes are superb not ABS standard of course but easily able to pull up the Vitesse quickly with no locking up or pulling.


So, don't take it as read that "they all have poor brakes" if your Triumph brakes aren't all you would like for no apparent reason check your caliper alignment and look for any movement of the caliper when the pedal is pressed. Either or both is a good sign that the mounting plates have distorted.

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Certainly, it is not true that "All Triumphs have poor brakes" but many have poorly adjusted  or maintained brakes.  Not your's, necessarily, Freyasgrandad!

If you can lock-up your wheels, the brakes are good, and the tyres are the final decider, anyway.


There are several types of "cast iron", some termed "ductile" or "malleable" that will bend under strain, when classically brittle cast iron will break before it will bend.

I would think that Triumph would use the first for such an application, rather than the second.


But I wonder if the seized piston was the result of the bend, not the cause.   The constant off-centre pressure would have distorted the piston seal and maybe allowed water in.

What bent the mount brackets, Gok!    Kerbing??


Which way were the both brackets bent?  and which piston was seized?



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Yes John, a very good question which did come first? 


I suspect that the piston ceased due to a very poor rebuild of the caliper, not by me I hasten to add, combined with a period of not being used over January and February but it must have been knocked back to have ceased where it did. The offside caliper was not ceased and the distortion on that mount was much less than on the nearside but it was also bent towards the wheel as was the nearside.


I can't see that a kerbing impact would have bent the mounting and not damaged other parts of the suspension.


The car has just clicked up 73000 miles and had original dealer service history until 66000 so I know the calipers were never worked on in that time. Therefore I assume that the calipers were done when the car was refreshed in 2008 and also assumed that the mounts might have been rusted on to the upright and were "persuaded" free with a large hammer but the evidence doesn't support that theory so frankly I'm not entirely sure what caused them to bend initially.


You are correct that they are made from ductile iron but the design is such that natural braking stresses should not cause them to distort as they have. In truth I still suspect a large hammer was involved but I cannot find anything to prove or even support this idea.


Interestingly the rear brakes have been rebuilt to a very high standard as has the rest of the mechanics and chassis of the car so why the fronts were so bodged up mystifies me.



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