I've recently built up a current model trek slash frame. It's got a boost 148 rear hub spacing and I bought a new 55mm crankset (latest slx 12sp) for it as that's whats spec'd for chainstay clearance for the chainring I believe. The chainline is pretty crap in the lowest gear and when I back pedal the chain is slipping off. I initially wondered whether is the mech hanger so I've borrowed an alighnment tool but can't actually fit it as there isn't enough clearance so I'm still not sure if the hanger is slightly bent. I just swapped on a new mech as the old had taken a few knocks but I'm still getting the same issue. Looking at the chainring I've got fairly good clearance to the chainstay and I'm going to switch from a 34t to a 32t which should help too so is there anything apart from the chainstay clearance to stop me from moving one of the crank spacers from the drive side to the non drive side to improve the chainline?
I should say, I think I only have 1 spacer on the drive side anyway
In my v v recent chainset thread, it appears that 55mm is suoer boost and 52 is normal boost. So you may be being hampered with the wrong cranks to start.....but im not an expert!
Yeah I saw that thread, was going to post in there but didn't want to detract from the OPs question. I'm pretty sure they spec'd it with a 55mm crank but it does make the chainline look awful. Is there any harm in swapping spacers from one side to the other though? Apart from any clearance issues? Ie does the spacer need to be there for another reason?
Im pretty sure you can move spacers to adjust chainline. Have you checked the build sheets for the slash? Sometimes it twlls you what model of crank is fitted, so may confirm or deny your suspicion?
Ian
I'll take a look. Just realised you are the OP on the other thread. My experience is to go with the most narrow chainline you can. I was running a non boost crankset on my orange with a boost hub because the chainstay clearance wasn't an issue and the chainline and shifting was much better.