BCD of 2 x 10 chainsets

BG2000

Has the industry agreed on a BCD size of 120 / 80 mm for dedicated double MTB cranks ?

I know poor old RaceFace went with that for their new 2 x 10 Turbine cranks (is anyone selling these !!??)

I don't see many chainrings for sale in this size yet though ? I think SRAM make you buy the whole spider don't they ? :shock:

nicklouse

there is no standard.

shimano has kept 104-64mm on one set and uses 88mm on another.

njee20

there is no standard.

shimano has kept 104-64mm on one set and uses 88mm on another.

This.

Carbon-Ti do some for SRAM cranks. Or I got a custom made 88mm ti ring from Matias Hellore. Doubt there'll be a standard any time soon! Shimano will stick with 88 I reckon, as will SRAM with theirs.

BG2000

I'm partly asking because after a couple of nasty chainsuck incidents recently, I'm weighing up my options, as I'm worried about losing my RHS chainstay ! (yes, it's a hardtail).

I'm running 42 middle / 28 inner on RaceFace Atlas AM cranks. I can't get the drive side crank any further out (maxed out on spacers), and yet the 42 is too close to the chainstay for comfort. Even with a 38 middle, any chainsuck would still result in heavy scratching to the chainstay.

The dedicated Atlas AM 'double' ships with 36 x 24, but a 36 x 11 highest gear may be a bit low.

I'm running fairly new Chinook rings with a newish PC-991 chain, all clean and well lubed - but sometimes in heavy mud, you just can't avoid chainsuck.

I just wish a decent anti-chainsuck device existed - despite most people hating them.

Hence, my interest in double cranks. But most are for 10 speed drivechains - I won't go into the 'should I change from 9 to 10spd debate here !

Hmmm, maybe I'll just have to go back to triple rings....

cooldad

Couldn't you run them middle and outer?

njee20

Can't go smaller than a 30t on the middle, and even then the only option is an Extralite Octaramp and you have to file your spider down. Also means there are no chainline advantages over a triple.

The dedicated Atlas AM 'double' ships with 36 x 24, but a 36 x 11 highest gear may be a bit low.

You may be surprised, I've just gone to a 36t single ring on my race bike with an 11-36, I can spin out on the road, and I certainly spend more time at the top of the block than I did with a 42/28, but I find it an excellent all round set up.

BG2000

njee20 wrote:

You may be surprised, I've just gone to a 36t single ring on my race bike with an 11-36, I can spin out on the road, and I certainly spend more time at the top of the block than I did with a 42/28, but I find it an excellent all round set up.

Presumably you're talking about 10 speed though ?

But even then, I'd need lower than 1:1 gearing for climbing steep rocky bits etc..

Spinning out of gears isn't too big a worry for me, especially with the few races I'll be doing now (soon to be dad of 2). So I could try a 36 + 24 x 11 - 32

I think I instantly assume my gear ratios are incorrect just because I'm using the 11. But I'd actually be quite pleased to wear that one out, for once, as it's usually the 14/15/16 sprockets that seem to wear out first.

I guess I may as well try - I'd have no problem selling a 36 and 24 if things didn't work out...