Will a 30-42-52 road triple fit on a Trek 7.3fx hybrid?

mishad

I have a Trek 7.3fx flat-bar hybrid (25"), which came with low-end MTB drivetrain: 28-38-48 and 11-30 8spd cassette. I use it to commute (all weathers) 17 mostly flat miles each way ~4 days a week.

Upgrading rear to 9 spd (new Deore MTB shifters, 12-26 cassette, chain, to get closer ratios in the useful range

Also considering switching chainrings to 30-42-52 to regain the 48:11-equivalent top gearing, and a slightly better use of the close-ratio (12-13-14-15) range of the cassette.

Will a 30-42-52 road chainset be compatible:

a) with the frame (bigger outer ring, and possibly closer chainline, vs chainstay)

b) with the front mech (low-end C102, specced for max 48T and 10T between rings)

c) with the rear mech (Deore long cage)

?

If (b) is a problem, I believe I'd need a new road front mech -- would that work fine with the MTB shifters, or would I need different shifters too? (I've read that MTB front mechs need the shifter to pull more cable so don't work well with road shifters, but not sure whether it works in the other direction.)

Thank in advance

Misha

Mr P

I'd make the back end changes first and run for a while, before deciding on chainwheel replacement - it is a lot of faff and expense for (perhaps) not a lot of noticeable effect (unless you are always in 48/11 now!). 48t is the same as many road compacts - I've got one and don't spin out on it very often with a 12t sprocket!

My answers to your questions;
a) the extra teeth outer will need an extra radius of about 9mm, and the chainline MAY take it in a max of 5mm - you can visually check clearance now with this info. (The chainline may not change if you keep the same bottom bracket. Shimano pref chainline for road triple is 45mm and mtb triple 47.5-50mm. Don't know if this is driven by crankset or bb though)
b) iirc yours will be a top pull mech. Don't think there is a top pull road mech, but the deore mech has a 22t capacity and 12t jump so should do you fine, and avoids any potential cable pull issues.
c) no problem

maddog 2

a) should be fine.

b) probably not. Best to match the chainset with the mech.

c) rear mech will be fine

as you say, road front mechs aren't compatible with mtb shifters (when running a triple). If you want bigger gears then consider running a compact double (34/50, 34/48 etc.). That can work with a mtb shifter quite easily.

If you must run a road triple c/set with flat bar shifters then you can, but it won't be cheap (new c/set, f. mech and shifters)

mishad

Thanks for the advice, guys.

I'll run the 28-38-48 with the 12-26 9sp for a while, as suggested -- its probably good discipline to force me to spin out rather than push (and so might save my knees as well as some cash and time!).

M

acorn_user

I have a C101 front mech running with a 52-42-30 Sora triple. But setting it up was not easy. it eventually proved too much for me, so I had to take it to the bike shop. TBH, I rarely use either the 52 or the 30, because 42 is just right.