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Hi there.
I'm building up a Charge Plug 'cross bike and i've a question regarding chainset spec that I hope someone can help with.
Most of these cross bikes with 135mm rear spacing come with road double chainsets. I'd like to run a set of Middleburn MTB cranks with the inner ring removed.
The reason for this (to my understanding anyway) is that the chainline of a 135mm rear hub is suited to a MTB triple rather than a road double. If I take the inner ring off the Middleburns and buy a slightly shorter BB (4mm shorter) to compensate, my reckoning is that i'll have a better chainline than if I ran a road double.
There must be a reason why bike companies aren't doing this though. Is it because you can't shorten the axle of a GXP / outboard BB? Is it because a road front mech won't shift the chain onto the big ring (even with a shorter axle?)
I'd rather find out before I go for the Middleburn's, but running a road double with a 135mm rear end seems a bad idea - even though everyone is doing it.
Any advice would be appreciated.
Thank you.
I think the MB mtb bits are designed around a 50mm chain line.
I ran a Duo set up with a 113 st bb. I run an Uno also on a 113 st bb which is spot on.
You can give Matt at Middleburn a ring - he is super helpful.
Thanks Nipper.
Good to know. The duo is a 47.5 chainline, other MB MTB cranks are 50mm, so if I use the triple crank with inner ring removed on a 108mm BB instead of reccomended 113, then I will correct chainline by -2.5mm, so should end up exactly as your Duo, in effect.
I notice the Salsa Fargo uses an X7 front mech with Apex road shifters (which is what I have), so i'm thinking Apex shifters + Middleburn MTB cranks + 108mm BB + X7 front mech will be fine... hopefully!
If I take the inner ring off the Middleburns and buy a slightly shorter BB (4mm shorter) to compensate, my reckoning is that i'll have a better chainline than if I ran a road double.
I've done the same on a bike, then used a Middleburn road spider on an MTB RS7 with a 107mm BB i/o the std 113mm, got 45-46mm CL I think. Can't remember tbh but it was better than the triple w/o an inner ring. What you're looking at with the duo sounds workable though. May end up doing the same - wish Middleburn made a 104 BCD double spider for 48mm CL like 10s XT doubles.
There must be a reason why bike companies aren't doing this though.
SRAM make wider-chainline chainsets for road bikes with 135mm rear ends. Shimano don't seem to think it matters.
Cheers Jameso,
Nipper - I just saw a photo of your Singular that you had the Duo on. What FD were you using - a road mech or MTB?
Jameso, could I ask you the same question (what FD and road shifters?)
Thank you
XT double with 105 double brifter.