Shimano front derailleur query

[Sergeant Pluck]

Hi all

Your knowledge is needed again 

I am having trouble finding a replacement front derailleur for my Marin. I need:

• 9 speed
• triple
• Mega 9 compatible, to work with indexed flat bar shifters
• Multi fit band on
• Needs to cope with 22T difference
• Needs to manage a 50T big ring

Will this do my job? I think it meets the criteria except for the last one; this is rated 48T max.

Thanks for any advice

SP

[Polar Bear]

Q1:  What shifter do you have?  Shimano road and mtb shifters for the front mech pull different amounts of cable.

Q2:  What is the current mech that you are replacing?

[Sergeant Pluck]

Current Shimano front mech unknown, probably a Tiagra, but the only Tiagra I can see is for road shifters and not suitable.

Q1:  What shifter do you have?  Shimano road and mtb shifters for the front mech pull different amounts of cable.

Flat bar shifters as above; very like these.

I ordered this as I thought it was what I needed; I was sent the bottom one and the manual makes it clear it is for road shifters which I did not determine from the ad. It'll have to go back.

[Polar Bear]

If the shifter is an mtb one then you won't get a road mech to work on it.   Rear mechs are interchangeable but not fronts.   Don't suppose you have a pic of the front mech just to be sure do you?

Biggsy is more of an expert but experience has taught me to stretch the range a tad with the quoted figures.   For instance, my audax bike runs a small ring of 26 teeth even though minimum 30 is specified.   There is usually sufficient capability in the mech to cope.       

I would be willing to bet that any Shimano 'mtb' mech with max 48 theeth specified will do the job perfectly.

 

[Gus]

Shimano R440 9sp Flat Bar Front Mech at Parker International
or Ultegra 6503 / Dura Ace 770

[Sergeant Pluck]

Cheers for all that, PB. I'm not trying to get a road mech to work on it:

You see I am not trying simply to replace the existing mech - the bike originally was 52/42/30. I have changed to 50/39/28 which changes my needs somewhat. That's neither road nor MTB ring sizing, really. If there is a bit of leeway with the 48T, if it would stretch to a 50T, then I think the mech mentioned in my first post might be the best match. But I'm not sure if it will.

Gus, thanks, that looks very like the existing mech - I don't think it copes well with a 28T small ring so I am looking for an alternative if possible, just to be awkward 

[Gus]

According to Shimano's website you need a FD-R773.

It is a flat bar front mech that should be able to take 22 teeth and a 50t chainring

[Sergeant Pluck]

That's for 10-speed chain though.

Thanks for prodding me to look at the website though: the FD-R453 would seem to cover all the bases. However, I wonder if it is only sold to bike manufacturers as I am having trouble finding one for sale without a bicycle attached.

[Gus]

Ohh so it is. 

Here are a chart that shows what parts can be mixed with the flat bar group.

hope it helps.

gus

[Sergeant Pluck]

Thanks Gus: confirms that a 453 will do if I can find one.

[Polar Bear]

Cheers for all that, PB. I'm not trying to get a road mech to work on it:

You see I am not trying simply to replace the existing mech - the bike originally was 52/42/30. I have changed to 50/39/28 which changes my needs somewhat. That's neither road nor MTB ring sizing, really. If there is a bit of leeway with the 48T, if it would stretch to a 50T, then I think the mech mentioned in my first post might be the best match. But I'm not sure if it will.

Gus, thanks, that looks very like the existing mech - I don't think it copes well with a 28T small ring so I am looking for an alternative if possible, just to be awkward 

Have you actually tried the existing mech?  I have twice changed my chainset rings from 52/42/30 to 48/38/26 on two different machines, one Shimano, one Campagnolo.   Both times the setup has worked perfectly.   All I needed to do was drop the mech down the tube to give the requisite 2-4mm clearance of the outer cage plate over the outer chainring.   First time I did it it took a little experimenting until I realised that's all I needed to do then it was plain sailing after that.

[Sergeant Pluck]

I've been using the existing mech with that set-up. The front mech is a bit tired and I think it might have been bent at some stage.

One of the reasons I'd like to try an alternative is this: since changing to TA rings, the inner ring seems to be positioned just slightly further inboard compared to the original rings. The mech struggles to go in far enough - part of it  just touches the seat tube. Ideally I'd like a mech that could go in a mm or so further as I'd get a better middle>small change then.

Obviously the answer is to fit a BB that moves the crank out a little further but I am not going to do that.

Returning to the initial question: will a mech that states its max size is 48T cope with 50T?

[Sergeant Pluck]

Thanks Gus: confirms that a 453 will do if I can find one.

Actually, looking at it again, the specs for a 453 note an inner ring lower limit of 30T, as opposed to my 28T, so again it's a question of leeway in the specs.