Crank Arm Fixing Bolt

bobskittles

Hi
I'm hoping someone can help me. I have a Trek Alpha 2.3 road bike & the crank cap was threaded by a mechanic on a charity ride. It has Shimano 105 crank, I need a new one but don't know which one I need. Hope someone can help.
Thanks
David

cycleclinic

What a mechanic!

Crankbolts are pretty common. Octalink probably and I have plenty. Most shop should keep these but read on.

If by the crank cap you mean the crank bolt that secures the crank arm to the BB axle then oh dear. These are steel and your crank arms are Alumium alloy so if the thread on the bolt is damaged the thread in the crank is probably worse. Removing your crank arms propewrly is now diffult/impossible. Riding around without the bolt may cuase them to fall off though.

If I have not misunderstood then you have to options;
1) new crankset
2) find a shop that has the tool do destroy threrads and re cut to a larger size. Helicoil are available or special crank removal tools which a larger threaded insert. Cylcus do one. I am itching to buy this tool but no one has come in with this problem yet.

bobskittles

Thanks thecycleclinic
Its the plastic plug/cap that im guessing protects the nut maybe?
Thanks David

nicklouse

bobskittles wrote:

Thanks thecycleclinic
Its the plastic plug/cap that im guessing protects the nut maybe?
Thanks David

post up pics of what is not there as there have been a few versions of the 105 over the years.

at a guess you have a damaged preload bolt.

but in ID on the cranks is needed.

bobskittles

HI
Its the dust cap/pre load bolt. The bike is 6 months old from new. Its made of black plastic with a hexagon allen key hole in the middle. I'm not at home so cant send picture.
Thanks David

nicklouse

http://www.trekbikes.com/us/en/bikes/ro ... ries/2_3/#

with the Shimano R600 cranks

http://www.sjscycles.co.uk/shimano-fc-4 ... prod17959/

bobskittles

Thanks Nick the type was a FC-5750.
Thank you for that.
David

cycleclinic

Are that part. That is not a crank arm bolt at all. I thought from your desription you had a older 105 with Octalink BB or square taper.

That is a replaceable part. Visit your LBS or buy of CRC/wiggle e.t.c.

keef66

When you're buying the replacement part, do yourself a favour and get the little plastic tool you need to fit it as well.

You'll notice from the pic that the recess is not in fact hexagonal but sort of daisy shaped.

The proper tool fits the recess precisely, and is designed to ensure you can only do it up finger tight.

It's only meant to preload the bearings; the crank is held on by the two pinch bolts.

ugo.santalucia

keef66 wrote:

When you're buying the replacement part, do yourself a favour and get the little plastic tool you need to fit it as well.

You'll notice from the pic that the recess is not in fact hexagonal but sort of daisy shaped.

The proper tool fits the recess precisely, and is designed to ensure you can only do it up finger tight.

It's only meant to preload the bearings; the crank is held on by the two pinch bolts.

Indeed...