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Machining brake drums Vittese Mk 1 2L


Martin OD

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Theyre available from most suppliers although are expensive (60 pounds each plus delivery). The problem with machining the old one is finding somewhere with the tools to do it these days as it needs a mandrel to hold it centred on the internal mounting hole.

Drums used to be routinely machined but as their cost came down it was no longer worth doing. I did manage to get mine done a few years ago in a workshop where they were prepared to have a go using a large 4 jaw chuck lathe and manually centering the drum which improved them but wasnt perfect.

One last spanner in the works is the possibility that any replacement drum might not stay perfectly round either. Cast iron has a tendancy to deform after casting and the blanks should be left months before theyre machined to allow for this. However Im not sure this is the case with all after market replacements so I would consider the condition of your old ones carefully before changing... 

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agree on the machining i bought from a good place two new drums for the 2000   they were really based on a thrupenny bit   been held in a chuck andseriously lobed 

went in the bin 

on our trucks we kept Qualcast drums outside to normalise for 18 months 

Pete

 

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The problem is right now the car pulls to the left which is towards the good drum. I can replicate it on the hand brake as well and so it is definitely the drums. The new shoes on the scored drum are only hitting the middle (unscored) part of the drum. I could use it until I wear in the shoes so that it hits all the parts of the drum but that will take a while. Or perhaps I leave the hand brake on when driving 🥴🥴🥴 to wear it in. Oval drums will be a disaster 😕.

As an aside I am looking at the front brakes shortly. It has been standing for a while and I need to see how good the fronts are.

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Definitely dont overheat the drums as that is a good way to get them oval😂 I would ensure the fronts are good and then, unless dangerous, drive it for a bit as even perfect but new drums and shoes can take a while to settle in....

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Reckon accurate machining wouldnt be difficult using a section of old drive shaft with hub. Bolt the drum on reversed using the wheel studs/nuts and clamp shaft in lathe chuck then skim the minimum to achieve a good surface. It probably should be ground but it'll be an improvement even without that👍

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  • 2 weeks later...

To be honest it does amaze me the very low price of our discs and drums. It's not as though they make 100,000pa of each part. It sometimes worries me the low price and more often than not low quality of replacement safety parts. 

Iain 

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Youre right on Spitfire/Herald repro drums but for some reason Vitesse/GT6 ones are much more expensive and why? Maybe the smaller ones are used on loads of other cars so they sell more, either way the quality is a always risk... 

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