Forum

[papasmurf]

There is only one type of bolt to use on brake discs the correct ones from the manufacturer. They are after all a safety critical item.

[stinkwheel]

Which brings us neatly back round in a circle, because we don't actually know the manufacturer and I'm convinced most of these fittings aren't standard, with the possible exception of the disc bolts which look to have been used multiple times by the degree of rounding on the heads.



However, I'm happy enough to consult an engineering chart to see what tension to torque a particular fastener up to. So if I use an M6, 12,9 button head set screw, I need to tighten it to 15 ft/lb. This will stretch it to within 90% of its plastic phase and it wont come undone. 12,9 has the highest tensile strength of routinely available bolts. Locking compound is just belt and braces. If that strips the tread out of the disc, it wasn't a very good disc anyway.

[Alan R]

just a thought but while you have the wheel out you might want to fit our hosts steel axle clamps in place of those standard Aloo-min um ones ??........I had a pair that had cracked on the underside and hence out of sight until I came to fit my disc conversion on the last Bullet....Scary Movie or what ???

[ric]

I think longer bolts would hit the foul the fork leg, not the calliper

[stinkwheel]

Aye, deffo going to change those, the ones on my 350 cracked too. I was considering just making my own out of a bit of billet alloy, the profiling is entirely cosmetic. It really just needs 3 holes drilling in a block of the correct size then cutting in half down the middle. I've got a lump of alloy at home that's about the right size. That said, the steel ones are only £12...



Also pondering if I should just go ahead and helicoil the M8 stud holes now because I've landed up doing all four on my 350.

[papasmurf]

It should be easy to identify the correct bolts, there are loads on the internet specified for the purpose.

[Adrian]

Not just the end-caps, Alan...



I'd be interested to see how well the former drum brake fork slider itself stands up to the stresses of a much more powerful (by RE Indian standards) disk brake. I know our hosts offer a disk brake conversion for drum brake forks, but if I'm correct it's "only" the Pricol version. I think I'd be happier with that brake if it were in a pair of leading-axle B5/C5 forks, where the right hand slider's casting is obviously beefed-up for disk brake use. Get the right year's forks and they will still fit the threaded casquette or fork yoke on the older models.



A.

[stinkwheel]

Just because people sell them for that purpose, doesn't mean they are suitable. You see loads of stainless bolts being sold for brake applications. I'd never use stainless on anything to do with the brakes. Even the very high quality A6 stainless fasteners are weaker than standard 8,8 mild steel.

[stinkwheel]

I looked at the casting and wondered, however, the lugs are only really holding the calliper in place. The braking force itself is acting through the fork leg. In use, assuming the calliper is self centering correctly, the only bit of the lug that sees a significant load is the part between the bolt and the fork leg and that's acting in compression.

[papasmurf]

stinkwheel there stainless and then there is stainless, it depends on the specification of it.

I made some small locating pins for the MOD in a previous life out of stainless and although they only had a 6mm thread on one end hitting them with a lump hammer when clamped it a vice had no effect whatsoever except on my wrists.