Triple chainset front mech specification.

[Brian73]

I'm fitting a 30 42 52 triple to my Bob Jackson Audax Club.

Most shimano triple front mechs state 50t max in the tech docs. The Ultegra 6703 allows for 52t but states minimum difference between top and intermediate is 13t.

Does this mean I need to buy a 39t or less middle ring or will it work OK with the 42t one?

Ta.

[Brucey]

you don't say what shifters you want to use, or what chainline you intend to run, or how may gears/what chain you intend to use. These things are important too.

I think buying different chainrings just to suit an available front mech is putting the cart before the horse; better surely to at least try to get a front mech that will work with the chainrings that you really want to use?

FWIW I would much prefer a 42 to a 39 as a middle ring....

cheers

[Brian73]

Dura Ace 9 speed downtube (friction front) (Friction/SIS rear) shifters

45mm chainline

SRAM PC-951 chain

HG-9 Speed 12-27 cassette

[Brucey]

in which case I'd use an older shimano MTB/touring style mech (bottom pull, bottom swing) meant for 'alpine' gearing i.e. with a 10T interval on the outer rings. These often look as if they won't have enough capacity but because the chainstays are more angled on a 700C wheeled machine, they have a larger capacity than when fitted to an MTB with 26" wheels.

Basically any mech from a 7/8s shimano road triple group (pre 1997) or many of the MTB mechs from that time or earlier will do the trick; a few of them are meant for 12T interval but even these can work OK on 10T provided you are happy to raise the mech 3-4mm or so; the vertical clearance above the middle ring can be less than 1mm and it will work fine. The MTB ones are meant for a 48T big ring but usually still work OK on a 52T.

cheers

[Brian73]

The newest 30 42 52 chainset Shimano made was the FC- 2303 8 speed, after that everything went 50t outer ring.

The FD-2303 front derailleur is rated at 10t middle to outer with 22t capacity but finding one is difficult, only 1 on ebay uk.

[Jimstar79]

Is the one on Ebay the right one for? I think it looks like its in very good condition and not too expensive, especially if it is what you're looking for - consider how much use you will get out of it for that price?

Hope you get sorted.

[pwa]

I had the same issue a while back and adopted 52-39-30 to please my new Ultegra mech. Not surprisingly the mech worked well. But as a bonus I found the 39 ring much easier to stay in than the 42 it replaced, and I think I use it more. The 30 and 39 rings get used a lot, and the 52 is just "turbo boost" on fast descents. So the big jump is easy to live with. My 39 is a nice TA from Spa.

[Brian73]

After a bit of googling I found the Shimano FD-R443 has the same spec as the FD-2303

22t difference with 52t max and 10t difference from intermediate to high.

and it's a 9 speed

Evans has them in stock too.

http://www.shimano.com/media/techdocs/c ... 684418.PDF

[Jimstar79]

After a bit of googling I found the Shimano FD-R443 has the same spec as the FD-2303

22t difference with 52t max and 10t difference from intermediate to high.

and it's a 9 speed

Evans has them in stock too.

http://www.shimano.com/media/techdocs/c ... 684418.PDF

Well done for finding that! Any chance you could post a link because I wonder if this could help me out, too?

[Jimstar79]

It's OK. good luck anyways!

[Brian73]

Bit more than I wanted to pay, but I got the chainset cheap.

http://www.evanscycles.com/products/shi ... r-ec039351