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Harness bolts

Violet Elizabeth

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Off to club track day at oulton on the 5th. Just remembered that got told off by a scruiteneer at brands due to the harness bolts not filling the threads.


Does anyone know where I can get some longer bolts, and is it just a case of unbolting and re-bolting ? Don't want to mess unduely with something so important.



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As a general engineering rule of thumb , minimum engagement of any bolt for strength is 1.5 times the diameter - for say M10 - thread in at least 15mm.


Much greater than that and he extra isn't doing very much other than filling the hole.


If scrut bloke can see end of threads and they are engaged as above, fill end of hole with underseal, silicone etc.


if they aren't engaged - use longer bolts.



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I have often seen scrutineers checking that the top harness bolts go all the way through the chassis rail behind your head and have at least a slight protuberance out of the bottom of the rail. I also recollect seeing guidelines to this effect, possibly in final instructions for a race or track day.


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There is 1 particular sprint venue (Wethersfield) where the scrutineer pulls up every Caterham on this point. Despite a qualified engineer pointing out to him how much thread was engaged and how relative to the diameter this was sufficient he would have none of it (scrutineers can be like that...). However he was quite happy for us to remove the spacer which allows the belt mount to pivot in order to get more thread engagement - this of course is much less safe since if the belt mount can't pivot then a sudden load is likely to 'tear' the belt at the mount point if the pull isn't exactly square. Said scrutineer states that Caterham are aware of the problem and will supply longer bolts, but when I asked them they knew nothing about it. I sourced some longer bolts elsewhere in the end just to avoid the hassle.



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