Changing chainset on Surly LHT

[chris__P]

Hi. Further to my earlier post about replacing the drivetrain on my Surly Long Haul Trucker.I was looking at what components to get. I want to get a SRAM PC971 chain, Shimano Deore HG50 Cassette (basically the same as what was on there to be replaced) but I want to replace the chainset. At the moment it is a Andel 110mm BCD 48-36-22. I want to replace with a Shimano Alivio 4 arm square taper M410 42-32-22.

Does anyone know if this will be compatable with the Surly LHT? I am no expert on bike mechanics, but it works out cheaper for me to order this from the UK (i'm traveling in Canada at the moment) and have a LBS to fit it for me, than to get the parts from Canada. (crazy i know.) Anyway, I want to make sure these components will go together before I order. I assume the fewer teeth on the bigger chainrings as a good thing, because I ride real slow and stay in low gears anyway.

Thanks

 

[RecordAceFromNew]

The Andel chainsets are uncommon in UK, it seems Andel are a Taiwanese chainset manufacturer. It is likely that your chainset is this model or similar, and as you can see it is available for either square tapered or isis bottom bracket, so you will have to make sure you get the right one (unless you wish to switch the bb at the same time).

Then I trawled around to see what the LHT spec says, generally, it appears:

Crankset: Andel forged, 110mm BCD

Chainrings: Andel aluminum, 48, 36, 26t

Bottom Bracket: Shimano UN-54, 68 x 110mm

which seems to indicate the standard equipment chainset is indeed square tapered in JIS standard (because that is what the UN-54 bottom bracket is). However, it is best you check, and please also check the bottom bracket shell is indeed 68mm wide. Some info including the visual difference of an ISIS and square tapered bottom bracket spindle is here.

A potential complication is that the LHT appears to have a road (Tiagra) front mech as standard (please check if it is), and since there is no info please also check the chainline ofthe Andel chainset (i.e. the distance from the centre of the bike to the middle chain ring). Since this Shimano spec says the M410 (which is a mtb component) will deliver a 50mm chainline with a 113mm Shimano square tapered bb, please come back here if your existing chainline is not very close to 47mm - we don't want a chainline mismatch between what your road front mech expects and what a new M410 mtb chainset delivers with a Shimano 110mm bb.

If your current chainline is indeed close to 47mm and that your bb is square tapered, then the M410 chainset in square tapered form should work fine provided that applying it 3mm closer to the frame than it is designed for doesn't cause it to clash with your frame (unlikely, but I don't know how we can be sure about this without trying). Please do make sure you don't get the M410 octalink version by mistake however. Further, assuming we can trust the LHT spec above and if you wish to renew the bottom bracket at the same time just get the UN54 or UN26, in 68mm shell width 110mm spindle length version.

Finally because the large chain ring is going to be reducing from 48T to 42T, a pretty significant drop, the mechanic will have to move the front derailleur down the seat tube by about 1.2cm.

Hope it helps.

 

[upsidedown]

My LBS replaced the Andels on my LHT with a Shimano SLX triple, so they must be pretty standard. I guess if it will fit a MTB it will fit an LHT.