I currently have a Dr Jekyll with Shimano Saint M800-1 single ring cranks (bought in 2004), i use a 9x1 gear set up but when the chain is in the lowest gear (largest cog) the chainline appears to be way out, it runs ok but i have to use a chain device which not only causes a huge amount of noise but also puts the chainline even further out!
i plan to replace the cranks and maybe buy a new frame, my question is do all cranks that have the saint style bottom brackets affect the chainline in this way? if i buy something like the Raceface Evolve DH crankset with the X type B/B will i have the same problem?
The chainline is measured when the chain is on the middle cog at the rear. If it's lined up with the front ring then it's fine. When you go to the extremes of the cassette the chainline will look wrong, but that's the price of running with a single front ring.
You do have a few mm of adjustment with X type BB's if you move the spacers around.
With a 50mm chainline such as the Saint the single ring lines up best with the 7th cog and as the OP notes the chainline on the biggest (1st cog) is not good. With a BB mounted chain device and a 73mm shell there are generally no spacers to remove.
i hear what your saying, if the chainline was more inline with the largest cog on the cassette it would have an adverse effect when on the smallest cog, gotcha.
when using a conventional style b/b does the front chainring not sit nearer the frame?
Older chainsets had a choice of BBs so could be run at 50mm, 47.5mm (the norme at the time) or even 45mm. These days all MTB chainsets with external bearings are 50mm.
That depends on the chainset, my old FSR had a chainline of 50mm with a 121mm BB in a 68mm shell running an XT chainset a newer shimano XT chainsets with an identical part number sat a full 6 mm further out. So just be careful when changing bits.
Looking at the Shimano website the Saint single ring crankset appears to have the ring where the outer would be on a triple, have you tried fitting the ring inside the spider?
No i havent on these cranks but this is something i've done before, although it does move the chainline in by a few mm or so it looks kinda strange.
The cranks i have are quite old, i'm wondering whether on newer models the BB cups are thinner? surely the single ring up front is quite popular (DH etc) so i would have thought manufacturers would compensate for this?
Saint is designed for use on bikes that will have fat tyres that need wide chainstay spacing and a wide crankset. They also often have a 150mm rear axle which lines up the middle of the cassette with a 50mm chainline crankset.
Shimano show two Saint cranksets: one for 68/73mm BB with a 50mm chainline & one for 83mm BB with 57.5mm chainline. Dr Jeckyll is a 68 so the 800-1 should be right, are you sure it's not an 805-1 Stuart?
