Chainstay/Bottom Bracket/Chainring CLearance

I did an archive search by the way. I get points for that. 🙂 Chauncey

FasterthanU said:

I am building an olde Mixte Motobecane from the bottom up. I want to install a Suntour triple crankset on it, but am unsure of the clearance needed between the inner chain ring and the chainstay. What is it? I've got an old book that tells me 10mm is a "healthy" amount. However, I feel a very tight clearance of 3 to 5 mm is more common. Is it? Thanks, Chauncey

Not sure why you need a 3ple for a mixte... anyways, if you'll be using most of the time the outer 2 chainwheels (as the case for mtbs where the granny is reserved only for really steep ascents) it is best that you concentrate getting a good chainline for these regardless of the resultant clearance with the granny gear and as long as it does not rub the chinstay.

hd reynolds said:

Not sure why you need a 3ple for a mixte... anyways, if you'll be using most of the time the outer 2 chainwheels (as the case for mtbs where the granny is reserved only for really steep ascents) it is best that you concentrate getting a good chainline for these regardless of the resultant clearance with the granny gear and as long as it does not rub the chinstay.

SO, no rule of thumb? I just try a bb I have and then gauge + or - for a new one from there? Is there a minimum clearance at least? Thanks, Chauncey

FasterthanU said:

SO, no rule of thumb? I just try a bb I have and then gauge + or - for a new one from there? Is there a minimum clearance at least? Thanks, Chauncey

3mm sounds good... about the same as mine.

FasterthanU said:

SO, no rule of thumb? I just try a bb I have and then gauge + or - for a new one from there? Is there a minimum clearance at least? Thanks, Chauncey

I agree that 3-4 mm should be sufficient.