sheared crown bolts - technical tip..

[mcmteam]

I don't really post much here, but I thought I'd share todays endeavours..

I sheared two crown bolts on my pace rc36 pro class forks.. :shock:

Under braking the wheel would dive off to the left & after the initial surprise I noticed a lack of hex heads in the crown - I thought they'd fallen out..

Arrived at the pub and looked closer to see they'd actually sheered off!

Anyway, next up was figuring how I'd get these out without having to drill; use a blob of epoxy on an allen key type of thing etc. but the simple answer was.

- Prime with WD40
- Find some thin wire (bared cat5 network strand is ideal)
- Thread the wire and loop it around the sheared bolt thread in between the clamp faces
- pull tight and in a bow-dowel fire lighting method spin that bad boy out!!

Boom! a 2 minute fix!

That's all folks

If anyone has any appropriate bolts please PM me, Ti would be favourable - the crown is the standard RC36 pro class type.

 

[02gf74]

were they Ti? If so, then replacing them with the same will more than likley end up with the same result.

If in doubt and it is safety critical, don't fit Ti but HT steel bolts 12 or 14 grade.

 

[mcmteam]

were they Ti? If so, then replacing them with the same will more than likley end up with the same result.

If in doubt and it is safety critical, don't fit Ti but HT steel bolts 12 or 14 grade.

this had crossed my mind.. More of the fact I may run the risk of pulling threads so a direct replacement would be favourable - cheers for the advice..

Although I do ride daily and a ride hard I'm not really bike engineer oriented, so I'm unfamilliar with the stresses involved, but I guess they were HT judging by the sheer pattern..

The bolts have A2 stamped in the head, and are none ferrous, however they're way too light to be stainless :?

Some kind of Ti alloy perhaps? they don't have a Ti look to them

 

[02gf74]

hmm, ^^^ that's a bit worrying - stainless comes in A2 (304) & A4 (316) grades - it is not meant to be used in stressed applications.

here is a A2 stainless bolt yesterday

 

[mcmteam]

many thanks for the info

Well I guess they must be factory, although there's every likelyhood they could have been changed at some stage.. Would I be best getting HT steel? I can probably pick some up today

 

[bren]

Yeah A2 will be budget grade stainless, probably swapped for the originals at some point. Factory would most likely be 10.9 grade ht plated steel.
If you were to fit A4 stainless versions they may be OK, as they are actually a higher tensile strength, pretty close in fact to 8.8 grade steel.
For my money I would fit new 10.9 bzp bolts.

 

[02gf74]

BZP cap head bolts (allen key fitting) are 12.9.