crank question.... and bottom bracket

[pembo6]

Hi. I am working on my first fixie project. I am goingg to buy a new crank online. My existing bottom bracket has square taper axle with the older style nuts (not newer Allen bolts) holding on the crank arms.

If I purchase a new cranksset for square taper, will it fit the larger nuts? Or do the newer cranksets only fit the axles with the smaller Allen bolts. My existing BB is the right size (68mm). I am just worried that the nuts won't fit into a new crank arm.
Or will I need to also purchase a new BB?

I hope I have explained that clearly??

[Dan]

They'll fit.

[BRLVR.v2]

They'll fit.

But the issue will be the axle length, if its an old road double it maybe toolong. A new bb that matches your crankswill get a better chainline. Have a look at sheldon brown's info . 68 mm is the shell width,the axles come in many lengths,and thats the important bit

[Dan]

indeed...

[slidetaker]

some deals combine BB with crank so the package will tell you what exactly is the chainline....(around 42mm)...

which you can aim to match with the cog in the rear wheel....

[Dan]

All redundant until OP has a wheelset. For example, running a road rear with a spacer kit means its likely that any english thread BB will work, as the chainline can be adjusted with the spacers on the freehub. Different story with a track/fixed rear, which is what Dave was alluding to. In any case, original question was whether the cranks bolts would work with the new cranks....

[pembo6]

Thanks for the comments.

So it seems that the cranks will fit my existing BB, but it may not be at the ideal chainline. It is an old road double chainwheel.

I will be running a new flip-flop rear wheel/ hub (in the mail) and will be using a fixed track cog. So a little limited in changing the chainline at the rear (without moving wheel over and re-dishing).

It sounds like my best option is to get the new crankset and check the chainline. Fingers crossed it will be OK. If not, I will measure the BB/spindle width and see what I need to get the correct chainline.

The crank I am looking at does specify the chainline (42.5 I think??) but it does not specify what BB size that is for. The specs are......

Chainline: 43.5mm
BB Axle: Square (103) NOT included

Is "103" the BB/spindle length? How can it state the chainline without knowing what BB is being used?

Thanks again for your help.

[Dan]

Chainline: 43.5mm
BB Axle: Square (103) NOT included

Is "103" the BB/spindle length? How can it state the chainline without knowing what BB is being used?

that's the chainline you'll get using a bottom bracket with an axle/spindle length of 103mm - cranks can only sit so far in on the axle before they bind, as they're tapered. Look at the link to Sheldon posted earlier. If you want a chainline that's lesser, you need to get a shorter axle, and vice versa.

[BRLVR.v2]

you can also look at removing the axle and flipping it as quite often they are longer on the drive side to allow for the two rings. This may bring it in a little closer. This works , I've done it before in the past on quick flip conversions.

[Mulger bill]

It'd be worth trying the single ring in the small ring position too, it won't look as neat but it may solve the problem.

[BRLVR.v2]

It'd be worth trying the single ring in the small ring position too, it won't look as neat but it may solve the problem.

I think OP is purchasing a new single ring specific crank which only has one mounting option any way.

[Mulger bill]

It'd be worth trying the single ring in the small ring position too, it won't look as neat but it may solve the problem.

I think OP is purchasing a new single ring specific crank which only has one mounting option any way.

Comprehension fail.

[BRLVR.v2]

It'd be worth trying the single ring in the small ring position too, it won't look as neat but it may solve the problem.

I think OP is purchasing a new single ring specific crank which only has one mounting option any way.

Comprehension fail.

Old age,bud.....