Front mech not compatible with new set up ?

skdotcom

Hoping some one can help !

I recently bought a 2nd hand Boardman Team Hybrid 2010 from eBay.....
When I get it home I realised that it wasnt in the "good" condition I was led to believe. Nevermind I think, I can now justify spending money on upgrades to build an even better bike!

I wont go into all the details of what I've replaced (saddle, seat post, hydraulic brakes, handlebar, stem, grips, bar ends, tyres, skewers) but will concentrate on the area that is causing my issues.

I have a SRAM X7 9spd rear mech (original part), Shimano Tiagra R440 Double 9sp Front Mech (original part), SRAM PG990 11/32 Cassette (upgrade from PG950 and SRAM PC991 Chain (upgrade from PC950).

The chainset is a new Truvativ Elita 2.1 Compact 9sp Double Chainset with 48/34 chain rings and GXP BB. The original set up was also Elita 2.1 with GXP BB but 50/36 chain rings.

So really the only thing that has changed is the chain rings from 48/34 to 50/36.

I should add that I didn't ride the bike much before I started the work and it wasn't shifting gears well anyway so don't know how well the original set up would have worked.

I took the bike to my LBS to set up the gears (and fit the chainset as I didn't have a tool to remove the GXP BB). They've done this OK, but the chain rubs on the front mech something cronic. I can only use a narrow range of gears on either the 48 or 34 ring. LBS said this is not unusual on some bikes from new, and they think the issue is that the GXP BB sticks our more than other BBs. They've suggested replacing the front mech with a triple rather than double.

This seems like a reasonable idea. Can anyone comment on whether this is likely to work, and more importantly what front mech i should buy?
I appreciate I've posted this in the MTB section, and when typing this realised that the chainset/front mech are actually road components, but its a hybrid and theres no hybrid tech section!

Greer_

Do you know what the teeth limit for the front mech is?

Just realised today that the compact chain set on my new road bike is controlled by a 3 speed shifter and 3 speed mech, and for some reason '1st gear' is the small ring, '2nd gear' is on the small ring but closer to the big ring, and '3rd gear' lifts the chain onto the big ring! Its been indexed like that (and I tried to fix it because I didn't realise I had 3 gears as such). Never heard of anything like it.

No idea if that's of any help

supersonic

What shifters are you running?

skdotcom

supersonic wrote:

What shifters are you running?

SRAM X5 shifters

Thanks.

skdotcom

Greer_ wrote:

Do you know what the teeth limit for the front mech is?

Just realised today that the compact chain set on my new road bike is controlled by a 3 speed shifter and 3 speed mech, and for some reason '1st gear' is the small ring, '2nd gear' is on the small ring but closer to the big ring, and '3rd gear' lifts the chain onto the big ring! Its been indexed like that (and I tried to fix it because I didn't realise I had 3 gears as such). Never heard of anything like it.

No idea if that's of any help

Thanks, the shifter that I have is a 3 speed too, at least what you're saying is that a triple front mech will work with a double chainring, but not necessarily solve my problem.

Greer_

Hmm well the tiagra front mech I have as a lot thinner than my sram x5 mech and im guessing that has something to do with the range of the cassette and chain line. A mountain bike mech might improve things? I know how annoying a rubbing chain is, can spend hours sorting mine!

supersonic

I didn't think MTB shifters worked with that front mech ie cable pull.

bikaholic

The FD-Rxxx series is the non group meant for leisure and touring bikes - that is to say, designed to run with cranksets with a narrower chainline than MTB cranksets, ie a road crankset.

It's 100% compatible with MTB 7,8,9 speed front shifters.

The corresponding Shimano SL-Rxxx is 100% compatible with MTB front derailleurs - the only difference is that they have intermediate micro-clicks for trim purposes.

The OP's problem is most probably chainline related provided they know how to setup a FD properly.

The most common issue with GXP cranksets is that people don't bolt it up tight enough - be liberal with the grease and tighten it until it bottoms out and locks into the NDS bearing cup.

If that doesn't fix it then try rearranging the BB spacers.