Front Derailleur on a triple chainset

[npcarey]

I’ve come back to cycling after a long absence and I’m doing a build of a Surly Cross Check, and am having troubling shifting to the outer ring of a triple chainset. The front derailleur is a Deore FD-M591-3, and am using Shimano Dura Ace 7700 9 Speed Bar-End levers, a Stronglight Impact Triple Chainset (48/38/28T), BB Sronglight 115mm and a 9-speed cassette.
I must admit to being bewildered by the multiplicity of both FD’s and RD’s these days, however as the Deore’s capacity was given as 20 teeth with a large chainring of 48 or 46, I assumed all would be well.
The cage is set up a couple of mm above the large ring, but cannot shift from the middle ring to the large ring as the the inner cage catches on the middle ring. I assume the cage should be able to clear the middle ring. Moving the FD up to clear the middle ring just makes it totally useless. Moving the set screws makes no difference. So what gives, am I entering my dotage, or is it the wrong FD for the job? It used to take me about ten minutes to replace FD’s thirty years ago.
Any help would be much appreciated.
Thanks Neil.

[531colin]

There does seem to be more front mechs. than humankind can possibly really need!!
It sounds like your mech. is designed for 12T difference between middle and big ring, eg 24, 34, 46T

[Graham O]

When I was building a Cross Check last year with the same front mech, I had the same problem. Changing the 46 tooth chainring to 48 solved it.

[Brucey]

....The cage is set up a couple of mm above the large ring, but cannot shift from the middle ring to the large ring as the the inner cage catches on the middle ring. I assume the cage should be able to clear the middle ring. Moving the FD up to clear the middle ring just makes it totally useless. Moving the set screws makes no difference. So what gives, am I entering my dotage, or is it the wrong FD for the job? It used to take me about ten minutes to replace FD’s thirty years ago.
Any help would be much appreciated.
Thanks Neil.

what is the problem with the raised front mech, exactly? ....some folk run that kind of setup OK...?

BTW one solution is to run a 30 year old front mech.... but seriously.... many older shimano mechs were built for a 46-48T big ring and a 10T middle to big difference.

cheers

[freeflow]

Try switching to a 105 or ultegra triple front mech. I use an ultegra 6703 front mech with a 42/32/22 xt chainset and it works well enough for my needs.

[reohn2]

I've run a 26/36/46 and 26/34/46 with the same mech,c/set,BB and friction levers.It changes better with the 12 tooth difference but the 10 tooth change wasn't bad by any means though the mech needed moving up the s/tube slightly to clear the middle ring.
I don't know what's causing the anomaly but I've got two bikes running with the same set up but road front mechs(one Tiagra one Sora) which work very well and with slick changes.

[npcarey]

Thanks for all the replies. I had another go raising the cage and still no joy. Can shift to the inner and back to the middle but no further. But I do have a nagging feeling that I’m doing something wrong.
However as 531colin mentions and with Graham O’s information it looks like a 12T difference is required so it looks like a 36T middle ring is needed.

Graham O wrote
When I was building a Cross Check last year with the same front mech, I had the same problem. Changing the 46 tooth chainring to 48 solved it.

A question for Graham O, so you ended up with 26-36-48T I take it?

Brucey wrote
BTW one solution is to run a 30 year old front mech.... but seriously.... many older shimano mechs were built for a 46-48T big ring and a 10T middle to big difference.

Brucey, I do have an old FD, a Suntour Xc I think, it has the opposite spring direction to other mechs, I’ll give it a try tomorrow. It's worth a try, mind you I need it for a future restoration.
As I’m in Ireland it’s the web for any chainring and the postage is the killer so will have to look for something else to buy to justify the expense. A 105 FD to be on the safe side?
Thanks again everyone,
Neil.

[recordacefromnew]

Thanks for all the replies. I had another go raising the cage and still no joy. Can shift to the inner and back to the middle but no further. But I do have a nagging feeling that I’m doing something wrong.

At risk of stating the bleeding obvious, I presume the H limit screw is all the way out? Can you measure how much cable is being pulled by the shifter end to end? If not ~20mm have you tried pulling the cable by hand after the mech won't go out any further?

A common problem using mtb mech with a road triple (I assume your current chainline is ~45mm) is to get to the small front ring - there is no conceivable reason, assuming nothing is broken, why you can't get to the big ring with your setup if you raise the mech just high enough to clear the middle ring.

I think it is too early to buy/try another (road) mech, sure a road mech would probably have been better, but all current Ultegra triple fds have minimum large/middle ring difference of 13T... and pretty much all road triple mechs are designed for a 50T large ring, so it is not all roses.

Having said all that, personally I think chance is both your current M591 and any Shimano road triple (especially 105 and below) should work just fine for you, if properly adjusted. It might be worthwhile going back to first principles, doing it step by step, by following this: http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

[cromo]

I'm no expert, but is it possible that the bar end shifter is mounted incorrectly so that it is not pulling enough cable? The bar end shifter sits on a square mount and I seem to remember reading somewhere that if it is mounted 90 degrees out, then the cable pull is affected.

[reohn2]

I'm no expert, but is it possible that the bar end shifter is mounted incorrectly so that it is not pulling enough cable? The bar end shifter sits on a square mount and I seem to remember reading somewhere that if it is mounted 90 degrees out, then the cable pull is affected.

I've been puzzling over this problem and the only thing I can think of is not enough cable is being pulled.
MTB mechs need more cable pull so if there's slack in the cable when the mech is in the inner position,there may not be enough left to quite get the mech over into the outer ring when the lever is at it full movement.
And if the lever is positioned 90 degrees out,Cromo's right the lever will only move through 90 of the 180degree needed to shift a triple c/set across all three rings.

[Graham O]

However as 531colin mentions and with Graham O’s information it looks like a 12T difference is required so it looks like a 36T middle ring is needed.

Graham O wrote
When I was building a Cross Check last year with the same front mech, I had the same problem. Changing the 46 tooth chainring to 48 solved it.

A question for Graham O, so you ended up with 26-36-48T I take it?

Correction, just looked at the bike and my front mech is a Deore XT. Why do Shimano have so many versions of Deore? Very confusing.

Initially, I chose 26-36-46 on a Spa chainset, but like yourself, could not get it to physically move to the large chain ring as the cage was hitting the teeth. I tried to raise it up to clear the big ring, but it needed a lot of height to do so. The spec sheet for the derailleur says a few mm (can't remember exactly) above the teeth and a 12 tooth difference, so I changed the outer to a 48. IIRC, I did try to change gear with the derailleur in a high position, but I don't remember it working reliably. It was an unexpected expense, but I'm happy with the results.

[npcarey]

Spot on cromo.

[b]cromo wrote[/b]I'm no expert, but is it possible that the bar end shifter is mounted incorrectly so that it is not pulling enough cable? The bar end shifter sits on a square mount and I seem to remember reading somewhere that if it is mounted 90 degrees out, then the cable pull is affected.

I removed the shifter rotated the mount, replaced the shifter, tried it and I was able to change to all three chainrings. Very relieved!
However the mech is positioned too high on the seat-tube, the chain rubs on the bottom of the cage in some gears and also on the ‘bulge’ of the inner cage on the outer ring. Moving to H limit screw relieves the second problem but pushes the cage slightly too far and will probably cause chain throw. So I’ll go with Graham O’s suggestion,

Graham O wrote
Initially, I chose 26-36-46 on a Spa chainset, but like yourself, could not get it to physically move to the large chain ring as the cage was hitting the teeth. I tried to raise it up to clear the big ring, but it needed a lot of height to do so. The spec sheet for the derailleur says a few mm (can't remember exactly) above the teeth and a 12 tooth difference, so I changed the outer to a 48. IIRC, I did try to change gear with the derailleur in a high position, but I don't remember it working reliably.

and go for a 12T gap between the middle ring and the outer. This will allow the mech to be positioned lower and solve the problems.
Thanks again everyone, this site is a great asset.
Neil