SRAM front mech options?

gkerr4

Hi - wonder if you guys can help - i'm normally a 'roadie' but please don't hold that against me!

I have a Carerra Subway bike which i use for 'family' duties - on the prom at blackpool, towing the tag-a-long for my youngest daughter etc. Its not the best bike, but it doesn't get that much use and i got it for less than the price of my campag record shifters on my road bike!

- anyway - although it is sold as a hybrid, its clearly a MTB frame and has MTB low gearing with a 20/30/40 triple on the front. I have always felt it was too low geared for me and as it doesn't go off road i thought i would change it for a shimano Tiagra 30/40/50 triple with hollowtech2 bearings that i had kicking about the garage. This also allows me to get rid of the 175mm cranks that came as standard on the bike and go back to 170's that i prefer.

I realised when i started the job that i would have to move the front mech up the seat tube, but there is a bottle cage mount boss in the way of where the front mech needs to be located.

My Question is - what other options do i have for a front mech? - it's a very large framed SRAM one that came with it - if there was a neater model, it might still fit under the bottle-boss? are there different types?
can i use a "road" type mech with it?
What are the 'low' and 'high' mechs that SRAM sell - would these fit ok? and work with the cheap X-3 Shifters it has?

here's some pics and thanks in advance for any assistance you can offer?

thanks
graham


Untitled by gkerr4, on Flickr


Untitled by gkerr4, on Flickr

nicklouse

it is unlikely any MTB front mech will work with the new rings due to the larger diameter of them and the fixed radius of the MTB mech.

anz road front mech "could" work but you may have issues with cable pull direction and band size.

if you are not adverse to a bit of metal manipulation then i would bend the cage.


PS you will need one with a low band position to clear the Water bottle bosses. the one in your hand is a High clamp.

Giraffoto

You're not kidding it's large framed, it looks like it's made of Lego. Leaving that aside, as stated above you can get front mechs with the clamp set a fair bit lower that the conventional swing design - have a look at all the Shimano ones on CRC and you'll see there are two types

gkerr4

thanks guys - i have since looked at CRC and wiggle - i see that SRAM do hi and lo clamp versions of all their models!

you are right Giraffoto - it's massive the one i have - weighs a ton too - ah well, cheap bike, cheap parts i guess!

It looks like i am going to struggle with the mech being 'ok' for the number of teeth - do you think it will still work ok? its not like the bike gets used a lot so i could live with a 'poor' shift, but would prefer it to work somehow - what size ring are most MTB mechs made for - is 40-42 about the max? will it work at all with a 50 tooth chainring?

thanks again.

graham

nicklouse

You sre not limited to Sram. Shimano will work fine. See if you can find a tiagra flat bar front mech. If should be fine.

And maybe try a sram rival.

gkerr4

but, won't the cable pull be out? - doesn't SRAM do that whole "1:1" pull thing or something?

think it'll work?

If i could find a road one which could band onto the 34.9 frame then that would be ideal

nicklouse

There is no difference on the front. And the front road being different is also debatable.

I run X9 shifter. A rival front mech and a shimano tripple crankset running two rings.

The only thing to consider is cable pull direction with road mechs.

gkerr4

what about this one?

neat mech, small movement / frame - available in 34.9 band-on and says it handles 48T which is only a couple less than the 50T chainring - should be ok do you think?

http://www.chainreactioncycles.com/Mode ... elID=40545

gkerr4

sorry - another - i take it that "dual pull" means it can be pulled from below or above?

(it's below, on this frame)

thanks

cooldad

Yes

bikaholic

Swapping a mtb crankset to a road crankset usually means that the chainline is moved inwards - meaning that mtb front derailleurs may not be able to shift to the smallest chainring on a triple crankset.

What the OP needs is the Shimano FD-R443 or FD-R453 front derailleur. They are down pull, bottom swing derailleurs but, since frame measurements are not available, I can't guarantee that there won't be any clearance issues with the lower bottle boss.