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Tiagra FD issues with Sugino triple

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Tiagra FD issues with Sugino triple

Old 09-14-13, 09:23 PM
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sthslvrcnfsn
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Tiagra FD issues with Sugino triple

Just replaced the stock Andel triple cranks on my Surly Trucker with a vintage Sugino VP triple. I wanted a slightly narrower Q (pedals closer together) for the "road bike feel" as opposed to the slightly wider "mountain bike feel" of the Andel. Also, for one of the first times in my biking obsession I was concerned with looks and wanted something a little more vintage/classic looking. Both cranksets have rings of 48/38/26.

The front derailer is the stock un-labeled Shimano 4503 (Tiagra triple FD) that comes with most new Truckers over the past few years. I'm having a couple of issues here, and they leave me with a catch 22:

1. The main issue is that when I shift to the big ring on the crank and the littlest three rings on the cassette, the chain rubs on the outer plate of the derailer cage. When I adjust the limit screw of the FD to allow more clearance, the cage strike the inside of the crank arm. Bad news! No more room!

2. Because the outer plate of the cage is contoured, I can move the entire FD down the seat tube so the chain - when on the big ring - is running past a part of the plate that bumps outwards and has more chain clearance. So I eliminate the FD cage striking the crank arm. BUT, at this position, the INNER plate of the cage strikes the teeth of the middle ring.

Note: Right now I have the FD mounted on the seat tube such that the INNER plate of the FD cage has about 1-2mm of clearance over the middle ring (when shifted to the big ring). I'm getting both minimal rub chain rub (when on the smallest cog in back - ie, when I'm going downhill and fast), and minimal rub between the outer cage plate and the crank. I think I've found the sweetest spot for this FD/crankset combo and it's not-so-sweet because of the rubs. "And that's the rub", as they say.

So, I have two hunches here, and I'm looking for feedback and expertise to confirm my thoughts. I love working on bikes, but in reality I'm an amateur mechanic, certainly there are people with much more experience who can hopefully comment. I know the original Andel crank arms have more clearance between the inside of the arm and the outside of the big ring - enough room for the Tiagra FD to operate cleanly - this was the whole point: I wanted a narrower Q. I knew I would be squeezing the derailer in when I installed the Sugino crankset. Looks like I may have to get an older FD with flat plates on the derailer cage. OR, perhaps I'm just not as adept as I thought with the fine tuning of FD positioning. Cable adjustment might be a factor, though I can get the FD to shift between all three rings - I just encounter the rubbing/striking issues mentioned above. I can set limit screws with no problem, so that's not an issue.

Thoughts? Thanks!

Last edited by sthslvrcnfsn; 09-14-13 at 09:27 PM.
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Old 09-14-13, 09:35 PM
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A couple of things to note:

- I'm running 9 speeds in the back - whatever Surly puts on there stock, probably Shimano.
- I'm using Dura-Ace bar-end shifters, which are purely friction for the FD.
- Probably not useful, but the rear derailer is Shimano XT with the long cage. Again, stock for the Trucker.
- The chain is stock. Yet again I would guess 9-spd Shimano.

Essentially the ONLY change in the drive system is the Sugino cranks.

Does anybody know if the new Sugino XD triples have fluted or skinnier crank arms versus the VPs? That would equal more clearance as well as the smaller Q I'm looking for. And the looks, too!
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Old 09-14-13, 09:51 PM
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This happens on some cranksets, but 3 sprockets worth is a lot, and something else must be going on.

Years back freewheels and cassettes were narrower, and FD geometry was a bit different so cranks had less clearance between the arm and chainrings. You might be able to solve the problem by rotating the FD a bit. As a starting place you want the cage equidistant from the arm as it sweeps by. Some times having the back slightly farther out than the front helps, but you have to experiment, and observe.

Bringing the FD as low as possible also helps, but I doubt it'll get you three sprockets worth of improvement.

The amount of angle you seem to have still seems excessive, so I wonder if your chainline is OK. Lay a straight edge against the face of the outer chainring (edgewise so flex doesn't cause errors) on a secant and carry that back to the cassette. Allowing for the offset to the middle ring it should line up very close to the middle of the cassette.

If the chainline lines up well inboard of the middle of the cassette, that's the problem. The fix might be a longer spindle to bring the crank out, but that defeats your desire for a lower Q-factor. But the problem may be a rear triangle offset to the right, which opens a can of worms as far as remedies go.
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Old 09-14-13, 10:39 PM
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Can of worms indeed FBinNY. I have rotated the FD every which way, looking at the cage's relationship to the chainrings mostly, but also the cage's relationship to the crank arm (is the crank arm striking the back of the cage or the front?) I feel like I've got the cage aligned pretty damn well at this point. I've been on two short (5 mile) rides and I can't help but stare at the new (old) cranks and the FD cage as I spin.

I addressed getting the FD as low as possible - it's got 1mm of clearance between the inner side of the cage and the middle ring (when shifted to the big ring).

Also I thought that cassette spacing and chains have become narrower as modern "technology" moves towards 9, 10, and even 11 gears in the back.

I'm not sure what you mean by "angle" though, unless you mean the angle/rotation of the FD. I will take my drywall square and lay it out on from the big ring to the cassette now and report my results: the outer edge of the CHAIN on the big ring hits the 5th cog in back. So the outer edge of the big ring and not the chain ought to hit between 4th and 5th gears in the back - right about in the middle.
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Old 09-14-13, 10:42 PM
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I should say this too ... When set up to the best of my ability, the only issue I have is BOTH minimal chain rub AND minimal derailer cage/crank arm rub on the highest three gears. So big chainring and smallest three gears in back. So I can get around town no problem, I just can't get to those downhill/go-fast gears without rubbing.
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Old 09-14-13, 10:44 PM
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Perhaps I have the drive-side crank arm tightened down to far on the square taper BB spindle? I don't own a torque wrench, and I'm the type of guy who tends towards the over-tightening side.
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Old 09-15-13, 06:15 AM
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According to the following document, the minimum required large to intermediate tooth count for your derailleur is 11T; you have only 10 so cannot optimally lower it for the large ring without it striking the middle ring on the way down as you have stated in point 2 of your OP. It is also rated for a maximum of 20 tooth front chainwheel difference, you have 22. So, you are exceeding 2 different FD specifications; the fact that it worked on your old crankset does not change this. It may be that the FD is simply incompatible with your new crankset. Perhaps a different FD, used within its limits, will work with your new one. http://techdocs.shimano.com/media/te...9830606982.pdf
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Old 09-16-13, 01:10 PM
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You might try raising the front derailleur enough so that the inner cage doesn't hit the middle chainring. As long as the limit screws are properly set up, it's not the end of the world. I suggest this as you are working with a touring frame + friction shifters, not a racing bike.

Mike
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