Me and me cranks again!

Hello all

I finally got round to checking out what my right hand crank was. I then went to Mr Google and put in the said figures and came up with lots of interesting stuff. My crank is a Shimano FC 1056 which is the old 105. Found an interesting bit on Cyclefoums about correct bottom bracket lengths. For this (as a double) the correct BB is 107. For the older FC 1055 the correct length is 113. Now I also found on Sheldon's - God rest his soul - site that if you use a 107 BB with the FC 1055 you get a nice track chainine. So my brain starts to whir a little and I deduce that if the 1055 with its 113 BB needs a 107 to go track then the 1056 with its 107 BB needs a 101 to go track!? Or am I no where near the tree I should be barking up?

Help!

no senor,

101 no existe here, I never see them..

very probably, I expect you use 107 and mount the chainring on the inside?

Generally speaking* you need to take 5mm off the drive side for doubles to get near a 42mm chainline. Fortunately old Dura Ace BB's were 102mm. Unfortunately, they're kinda hard to find.
Campagnolo make a 102mm for Chorus and Record but different tapers mean your cranks will go on too far and possibly bottom out on the spindle.
I think Stronglight make a 103mm with the japanese taper.

*I reckon Sheldon mentioned the 107mm in place of the 113mm because Shimano make a symmetrical 107mmBB, the 113 is not symmetrical, and do not make a 108mmBB at all.

Mounting the chainring on the inside with the 107mm would indeed take 5mm off the chainline as well.

How accurate do you have to be with chainline? With my hub/sprocket combo, according to Sheldon, I should have a chainline of somewhere between 41.5 and 42.15. With my crank and using the inner mount I should get a chainline of 41mm. Is this enough?

nononno. Sugino do a BB of 103.

...let me find it...

Bingo

I was looking for that too!
i just couldn't remember which cycle company sold them.

eyebrows do you ride in Oxford?

So with a 103 bb the outer ring should be at 42 then. I think thats right isn't it? 46m outer on a 107. No, poo pah! Doesn't that give me a 44mm chainline?

My calc...107 gives the outer ring a CL of 46 (Sheldon)

          103 - ?2mm shorter on each end as they're symmetrical - would be 44? No?

A few things spring to mind...

1. Whats the rear spacing?
   
2. Do you have to keep the old crank?
   
   

On conversions I'd either space & dish the rear wheel, or fit new crank & bb. In my experience to do it cheaply usually means the space & dish option. Either way you can have a straight chainline.

I've just put my bid in on some new cranks...
Hopefully the headaches will stop soon...
Doctor says I'll be fine once the initial excitement wears off...

Thanks for all your help once again. Stay tuned for the next instalment of Anthony's crank saga!

If you've got a track frame@120 spacing go for some track cranks.

@miro_o yes. Look out for a black bob jackson with crazy handlebars.

I've got an old peugeot beater. No track ends in sight!

That's funny.
I have an old Peugeot beater (also with no track ends). And I ordered a white Bob Jackson Vigorelli Yesterday.
eyebrows I'm in Cheltenham but often ride in Oxford. I plan to ride to Oxford someday. I shall keep an eye out next time I'm there.

nononno. Sugino do a BB of 103.

...let me find it...

its a rebadged RPM if you can find them too!

I've got an old peugeot beater. No track ends in sight!

Right Anthony. Your rear spacing is 126mm (i'm taking a punt at this so you'll need to check - use measuring calipers, and Sheldon's guide if you struggle). Whatever your chainline is at the front it's fine. All you need to do is know what it is.

For the sake of argument lets say you did get the Sugino 103 BB and you old Shimano cranks on the bike and your chainline is now 44mm.

Your track hub will be 120mm in a 126mm rear space so will need spacers to the effect of 6mm. A regular track hub will have a 42mm chainline, (but I usually measure with the cog on as it can vary by a 1mm or so).

This means you can move the rear wheel, hub and cog 2mm out. To do this use 1mm spacer on the drive side, and 5mm spacer on the non-drive side.

You now have the perfect chainline, but need to dish the rear wheel 2mm with a spoke tool, so it sits centrally in the frame. If you need to know how to do that try Sheldon again or feel free to ask.

[note... on my bike with 126mm spacing I found spacing to the effect of 4, rather than 6mm better as it pinched the frame 1mm each side. This means I just run one 4mm spacer on the non-drive side.]

Cheers miro_o. That should come in useful.

No problem. There is plenty more here