Shimano Drive Compatibility

I want to replace my front twin chainset with a triple on my road bike - to be able to shift down to a 22 - 24 teeth ring. I need to get up some mountains next year!

I have just fitted a new HG50 8 sp cassette with a HG70 7/8 sp chain. I have picked up a 3 speed Sora Flightdeck shifter, to match the RH shifter, off ebay.

I am looking at an Alvio chainset with a suitable mech - will a MTB set work on a road bike and will it mesh with the above componentry.

Any help appreciated

 

Yes. You CAN use a MTB crankset on a Road bike's frame ...

• you may want to replace what is probably a 42t outer chainring with either a 46t or 48t outer chainring, BTW.

FWIW. I recommend a 113mm Shimano Octalink + LX-or-XT crank OR a 109.5mm Shimano Octalink + XTR crank ... you'll find these on eBay ...

• the spline pattern on the two TYPES of Octalink BBs differ & are not interchangeable

There may certainly be OTHER crankset & BB combinations which will work BUT you may have to worry about the chainrings being too far outboard from the bike's centerline.

BTW. OLDER, square-taper 110BCD cranksets usually have mounts for a Granny -- I think the BB length is 118mm, but a shorter spindle can often be used ... the caveat is that you need to know if the crank uses a symmetrical or asymmetrical spindle ...

I know someone who uses a 22t (?!?) with a "standard" 130BCD Road crank (DA 7700, Octalink) ... BUT, he uses a 39t Triplizer MIDDLE chainring (~$80+) to preclude (¿?) any chance of the chain becoming lodged when making the transition from the inner to middle chainring. He used a 118mm Octalink BB, but I found that the 112.5mm (XTR) Octalink BB could be used with Triple cranksets.

THE OTHER OPTION is to simply use a MTB rear derailleur + MTB Cassette ... even with a Triple Road crankset if you think you need it.

Just be sure that the 8-speed Shimano Cassette is of a reasonably recent vintage and that the cogs are ramped ... otherwise, just get a new SRAM 8-speed Cassette.

BTW, if the front shifter is a Road shifter designed for an 8-speed drivetrain then the front derailleur needs to be designated for an 8-speed Road drivetrain ... your current front derailleur may be "okay."

 

Brilliant thanks - a lot to take on board, but I think that is clear enough!