Shimano Hollowtech crank fixing bolts

Sailing7

Has anyone else had problems getting the two small M6 x 15mm bolts that take a 5mm allem key tight enough on the non drive side crank? I've just about rounded out one of my bolts and will need to replace it.

I'm reluctant to just get two more Shimano bolts as they'll round out too and they're not cheap! I've been thinking of replacing them with harder wearing titanium. Is this a waste and would I be beter off just getting high grade stainless bolts from a motor factor or such?

Any one with simlar experience please share your thoughts

maddog 2

the torque setting for the pinch bolts isn't a lot, 12-15 Nm if my memory serves me correct.

so I can't see how you're rounding them.... unless I'm miss-reading your post.

nicklouse

what are they made of? Cheese!
if they are the original ones then they are Harder that Ti.

I blame the tools.

Sailing7

Looks like I need to add 'Torque Wrench' to my Santa Wish List then as I'd read the 12-15 N-m (106 - 132 In lbs) as TIGHT.

As for tools - they're Halfrauds Professional which my mate who's a Snap On dealer rated as fine for home mechanic use. Will just get Shimano replacement bolts and not be so enthusiastic! Perhaps Loctite is all I need for peace of mind?

gkerr4

yeah - they don't need to be as tight as you are thinking. the locking tab thingy should give some piece of mind too.

wow - how are you rounding those allen heads?

your not using an imperial allen key set are you? (sorry - I know thats probably a daft question...)

Sailing7

Well it's not exactly rounded but the 5mm Hex key slipped round in the bolt and I stopped tightening then! Can probably still undo the bolt but not tighten it any more. Just using the standard 1/4 inch socket driver handle tool which is no more than 20cm long and my arm - which isn't huge!

Had thought they needed to be TIGHT as it's those bolts stopping the crank from working loose on the hollow axle.....

alfablue

If it was a cheap hex key it could be inaccurate and increases the chance of rounding.

A good source of bolts in all sizes is Stagonset. They will sell in any quantity, they are good quality, and they usually arrive within 2 days of ordering.

Probably M6 20mm socket head cap head screws will do the job (they are 19mm on my Ultegra chainset, but an extra 1mm should be fine as there is about 4mm unfilled thread on the other side). Cost 2 x 15p plus £1.50 postage, so it is worth getting a selection to make the postage justified.

aracer

If you've got a 20cm lever, then 12Nm is 60N of force, or the equivalent of putting a 6kg load on the end of the tool. Not actually that much when you think about it (<10% of bodyweight for most).

andy_wrx

Titanium 'harder wearing' ?

Titanium bolts are softer than steel and will stretch.

Bling, might save a few (I mean a few) grams but I wouldn't use them for anything important, just e.g. to hold on a bottle cage.

geoff_ss

Another excellent source for allen bolts is Modelfixings http://www.modelfixings.com/

My main pastime now is aeromodelling and I buy lots of stuff from them. You can pay through PayPal and the postal charges are reasonable.

Geoff

Sailing7

Update on bolts - having taken crankset apart last night after total water immersion on way home I found out the hard way that the spares bought online were not the right length. Who'd have guessed that the Dura Ace 7800 crank arm only needs 15mm bolts whilst the Ultegra Hollowtech is best suited to a 25mm closest to the bearing and 20mm further out? Should have visited my LBS - Mike Vaughn much sooner! Only cost 50p for the two bolts too.

Hope this info is useful for anyone else with Shimano Ultegra Hollowtech cranks and bottom bracket.