Nearly finished the commuter build and rode it in for the first time today (Rides nicely on 2.3 Supermotos)
It has an Alfine 8speed hub with an 18t sprocket fitted

I have just put a new 32T stainless front chain ring on and I could do with it being a bit taller geared.
I am limited for chainring clearance so was wondering if anyone knew the difference in Diameters of a 32T 34T 36t chain ring ?

Cheers
Dom

chain is 1/2″ pitch.

so 2t will add 1″ (25.4 mm) circumference

diameter of 32t = 128 mm
diameter of 34t = 137 mm
diameter of 36t = 144 mm

* guessing

The number of teeth defines the circumference of the chainring so the difference in diameter will be the difference in circumference measured in teeth divided by ?

So, ((32/36)/?)*100 for percentage difference = about 28%

Wow – more than I thought!!

Rachel

My 40t Surly measures approx. 175mm Dia.

If we allow 10mm for the height of the teeth, we get: 165

165*Pi = 518

518/(25.4/2) = 40ish [it has 40T]
So (518-25.4)/Pi = 38T = 157mm ish
and (518-50.8)/Pi = 148mm….ish

ie for each 2T less than 40, you remove 25.4mm from the Circumference and then divide by Pi

I think

No need for pi in the calc rachel – it cancels out for both sizes. It’s a straight percentage difference.

(32/36) x 100 = 89%

Think that may be a little off, I believe the diameter is directly proportional to the circumference. So a 36t would have 12.5% larger diameter than a 32 which I think is what Thom said up there.

And that’s the most I can remember from my degree. 🙂

Cheers everyone,
I shall have a measure up tonight but I suspect if I want to maintain a decent chainline then I shall have to go down on the rear sprocket instead

You could maybe squeeze a 33T ring in there?

http://on-one.co.uk/i/q/CROOSS/on_one_stainless_chainring

Easy.

32-34-36 are ~134mm, 142mm and 150mm

(I’m not great at maths but I do have the shimano tech book..)