irc wrote: mikeymo wrote:
irc wrote:Will the 771 not go up gto 36T anyway. I thought Shimano were a bit conservative with their specs.
I know the feeling with 1x9. I run low normal rapid rise derailleurs on my 3x9 tourers. Currently have 2 nearly new ones on my two touring bikes and two brand new on the shelf.
I'm happy with 34T at the back though. 22/32/42 on the front.
Thanks. I'd like to be able to go down to a crankset that size, but it isn't as simple as I first thought. It seems that most cranksets like that are for MTBs, and at the crank there isn't the same MTB/Road compatibility as there is at the back end. Could I ask:
1. Is this a drop bar bike with STIs (or similar)
2. What crankset is it?
3. What BB is it?
4. What FD is it?
5. Do you know what the chainline is?
Drop bar tourers using bar end shifters . A Surly Long Haul Trucker and a Spa Steel Tourer. The bar end shifter allows Deore Hollowtech 2 cranksets with HT bottom brackets and MTB XT front shifter.
I realise that isn't much help if you use STI's.
Only tip I can offer if you are on STIs is this device (below) for adjusting the inner/outer position of front derailleurs which may help with one aspect of getting STIs to shift on an MTB chainset or move a road front deraileur further outboard if required. . The other way with Hollowtech bottom brackets which could be used in conjuction is putting only one of the 2.5mm spacers on the drive side and two on the non drive side which shifts the chainrings 2.5mm to the left. https://www.sjscycles.co.uk/gear-spares ... hed-split/
Thanks. This is all new to me.
I've got a pair of Dura Ace DT shifters on the shelf, and sometime I'll try them out. But I'd like to keep at least the option
So if I've got this right:
1. If I'm using road STIs, I need a road FD (like I've got).
2. But the main problem is that most MTB chainsets are expecting a MTB chainline, which may be 50mm (or even 54mm with Thorn cranks) and then the FD isn't in the right place. Because road FDs are expecting a road chainline, of 45mm.
3. As far as I can tell, and please correct me if I'm wrong, the actual chainring to chainring spacing on a triple MTB chainset isn't substantially different to the spacing on a road triple chainset. And I can always make it wider with chainring spacers, but not narrower, obviously.
So I need a way to get the FD further out, the chainset further in, or a combination of those.
The Jtek eccentric shim (which would work on my bike, 28.6 seat tube) would do the first thing. And by changing the BB (if ST) or doing the thing with the shims on HT, I might be able to do the second thing, at least until I ran out of space on the BB. At which point the (road) FD would be "centred" over the chainset.
As the whole point of this is to use smaller chainrings, I assume that I'm less at risk of them catching the chainstay if I'm moving them inboard.
And as a matter of fact I read somewhere that with 135 OLN, like mine, the chainline should really be 47.5 mm. I'll measure it sometime.
Am I on the right track?
PS, the reason I'm interested in the Thorn Cranks - https://www.sjscycles.co.uk/cranks/150-thorn-10464-pcd-triple-crankset-mk2-black/
- is that they are about the only cranks that will take a 22 tooth inner, and also have 165 crank arms available, which is what I have, and like.