After this thread:

http://www.singletrackworld.com/forum/topic/whats-causing-my-chainsuck

one of the chainring bolts fell off the workbench, accelerated across the floor and has disappeared.
After numerous swear words & pulling all manner of stuff out of the way I still couldn’t find it (I even went CSI style with my Spokeshirts light).
For the moment I’ve taken one out of another chainset, but need to replace the missing one (which i will inevitably find the day the new one turns up).

The ones on the CRC website are almost as much as the chainring cost, but I have found these….

http://www.sjscycles.co.uk/shimano-fc-m770-inner-chainring-fixing-bolts-m8-x-85-mm-pack-of-4-prod18106/
for £7.14 which are specifically for my chainset, XT M770
and these:
http://www.sjscycles.co.uk/shimano-fc-m771-inner-chainring-bolts-m8-x-85-mm-1j2-9803-pack-of-4-prod18016/
for £4.07 which are for the M771 chainset. What’s the difference though, apart from a £3 saving!?

They are both M8x8.5 an appear to have a T30 Torx head.

Obviously don’t wanna order the wrong things, but don’t wanna pay £3 more than I need to for some bolts that are identical….

It’ll be under the fridge (even of the fridge is in a different building).

check postage on SJS before you order – it’ll be quite a lot.

I wouldn;t want to recommend one over the other – I don’t know the answer to your q.

I cannot see any difference – perhaps they are different materials. This is where a friendly local bike shop can help out. Do you have one? Or some mates that have been cycling for ages and accumulated loads of spares? A bloke at work who cycles in lots?

Go to the dump/tip/CA site with your allen key and ask if you can have one off a bike in a skip? There is a flytipped bike in a hedge up the road from me!

I have loads of old ‘spare’ chainring bolts that you could have one of if you lived around the corner from me. Where are you?

These are £4.99

http://www.chainreactioncycles.com/Models.aspx?ModelID=40570

Is it inner ones that you need?

I cannot see any difference – perhaps they are different materials.

The M771 bolts have a large unthreaded portion. If there’s going to be an incompatibility, it’ll be by using 771 bolts with a 770 ring. There may not be enough thread on the 771 ring to be able to tighten it properly.

I have some new KCNC ones if your interested ?

JImmAwelon…..I am nr Peterborough.

Yeah, I have a local bike shop, but am not around on Saturday and cannot get to them in the week. I might give them a bell though anyway.

Those RaceFace ones from CRC might be a go-er though.

Three Fish – very observant! I obviously wasn’t looking close enough. You are probably right that they won’t be compatible due to the non-threaded portion. Thanks for that!

wwaswas – I did actually check under the fridge freezer – although only the one in the garage, perhaps I should check the fridge in the kitchen too!! Fingers crossed the chainsuck has gone although comparing the old & new rings there appeared to be very little difference.

on and on – Member
I have some new KCNC ones if your interested ?

Are these the ‘male & female’ ones for the outer/middle chainrings?
I should have mentioned above, I am after just the inner chainring bolts that I think are just the male side of the KCNC ones.

Thanks for the offer, but I’ll probably give the RaceFace ones a whirl or see if my LBS can sort me out at some point.

Ah I see, mine are the M/F.
All the best
Steve

The Shimano document in the link below explains that all the chainring bolts for the M770 and the M771 cranks are interchangeable:

http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-M771-K-2694_v1_m56577569830621042.pdf

Thanks for that edd – very useful!