Kontact 

Actually, it will only be a 2.5mm offset on the drive side. I misspoke in my previous post. As you can see in this manual page, the Alivio crank always gets at least one spacer on the driveside, and adds one on each side in addition if the BB is 68 rather than 73.
https://manualsnet.com/shimano/crank...manual?page=12

At this point no one is sure if you are having a problem simply because your derailleur cable tension and/or limit screws are off. Or if your derailleur doesn't have the mechanical range for the wider MTB crank, or if it is some other problem - like the shift cable being attached to the wrong spot on the derailleur mounting bolt (you should check.)

The other thing to be aware of is that you have road derailleurs because you have road shifters. The Shimano mountain front derailleurs aren't index compatible with road shifters, and vice versa. So don't go get an MTB front derailleur if you have road STI levers.

alcjphil

It isn't clear what shifters you have on your bike. If you have Tiagra shifters that would explain why Surley specced a Tiagra front derailleur. Road shifters don't work well with mountain bike front derailleurs. My touring bike has bar end shifters with friction shifting for the front derailleur so I can use any front derailleur that I want

Trogger

First item of note is that the bike is fully stock, as delivered in 2010 from Surly EXCEPTING the crankset and BB that have been replaced.

If I have 2x2.5 mm spacers on the drive-side, (I note there is also a single 2.5 spacer on the other side) why would it be only a 2.5mm offset? (Which doesn't seem to make sense mathematically if we're only using spacers to account for the difference between 68 and 73mm -- i.e. 5mm; whereas 3 x 2.5 = 7.5mm) (I'm assuming -- likely incorrectly -- that, if the spacers were not there, the position, in space, of the new rings would exactly match where the rings on the old crankset were. Or, becase, to my -- likely wrong -- understanding, the HT BB bearings are outboard of the BB shell, maybe the rings are further from the centreline even without the spacers? I have eyeballed the two cranksets, old and new (both triples), and they appeat to have identical spacing between the rings, so the new is no wider than the old. My head is going to explode!)

My shifters are bar end SL-BS77 (If anyone has a link to the full details of use of those, not just a low-granularity exploded view, I'd be happy as 1. mine are wearing out and 2. I've messed up the orientation of the rear-derailleur shift arm vis-a-vis the mounting rings, if that makes sense). The front shifter is friction. I'm quite sure I've relaxed both limit screws sufficiently to give the basic mechanism a full range of motion. There is more than one place to connect the shift cable? I don't understand. In any event, even with the cable not attached, using my finger to move the derailleur to full extension, it doesn't reach far enough.

I someone has a link to a side-by-side comparsion diagram, oriented along the centreline, showing dimensions of a sq-taper crankset beside a HT crankset, that may be helpful.

2 steps forward, 1 step back.

cyccommute 

Much is made of different dimensions that usually doesn’t matter. And don’t get hung up on metric vs SAE values. Yes, 5mm seems large but it is less than 1/4”. That isn’t going to throw off your physiology. This article looks at Q-factors and comes to this conclusion:

If a 60mm difference in Q-factor has little impact, a 5mm difference is going to have less of an impact.



As base2 said, this has nothing to do with Trek, the company. “Trekking” has to do with the chainring selection on a mountain bike triple crankset. Instead of 44/32/22, a “trekking” crank will have 48/38/26 chainrings. The crank is still a mountain bike crank with, usually, a 104/64mm bolt circle diameter (BCD) and the wider stance of a mountain bike. Road bikes tend to use 130/74mm BCD which do not allow for the smaller gears. The smallest middle ring on a 130mm BCD has 39 teeth. The road bike will tend to have a narrower Q-factor and the Tiagra front derailer is designed for road applications. It can be made to work with the wider mountain crank but, usually, only by moving the crank inboard. You have to do the same with a square taper. Your previous crank used a narrower bottom bracket that it would have if had been mounted on a mountain bike.

Kind of my bad. Shimano uses three 2.5mm spacers on the Hollowtech II trekking (and triple mountain bike) crank. There are two on the drive side and one on the nondrive side for a 68mm width bottom bracket. For the 73mm BB, there is only one 2.5mm on the driveside. Yes, there are 5 mm of spacers on the driveside but mountain bike front derailers are meant to swing wider than road front derailers are. While that 5mm may not be important to the Q-factor, it becomes important in this case. Your derailer isn’t designed for that kind of width but mountain front derailers don’t play well with road shifters. You need to get creative. That means moving some spacers around. Often that means moving most or all of the spacers on the drive side to the other side, which moves the chainrings 2.5 to 5mm inboard, depending on how many spacers you need to do the job.

Parts are often mixed and matched to get a desired result. The Tiagra road triple crank is a 130/74mm BCD crank. That limits the low gear for a touring bike to something like a (reasonable) 50/39/26 tooth chainring set. That might be okay for an unloaded bike but for a heavily loaded touring bike, it ain’t gonna cut it. So they used a mountain bike crank and, likely, a shorter bottom bracket to make it work. There’s nothing wrong with the Hollowtech II cranks but you have to make some adjustments to get it to work properly. Moving spacers is relatively simple and it works.

cyccommute 

Not no one here. I know exactly what the problem is and it can’t be solved with cable tension nor limit screws. The Tiagra simply can’t be pushed out far enough to be used with the “normal” mountain bike spacer configuration. I’ve done this at least 4 times with road front derailers, STI shifters, and Hollowtech II cranks.

Fully agree. A road front derailer will work and work well, it just takes a bit of creativity to get it to work.

Kontact 

As I said, the Alivio crank design always has an odd number of spacers. That's the way it is designed and what it shows in the manual I gave you a link to. It has the extra spacer because that spacer is sometimes replaced with a FD mount ring. So it should have two on the drive side if your bb shell is 68mm wide. Might be worth measuring your BB shell.

The other thing that can make your crank stick out is a spacer on the spindle itself under the spider. You would notice this as a possible cause if the crank arms are different distances from centerline. You can measure this by measuring from the seat tube out to each crank arm. That distance should be roughly symmetrical.

Using the same technique, you can measure your chainline going from the center chainring to the front center of the downtube or seattube. Center to center should be around 47.5mm. What is yours?

Is your Tiagra FD a band type or is it mounted on a band adapter?

Square taper mountain cranksets have the same dimensions as HT mountain cranksets. Your issue is that something isn't working when you went from road triple to mountain triple.

It doesn't sound like your cable is an issue. But people sometimes mount the cable above or below the bolt when it should be the opposite.

shelbyfv

Since OP has front friction shifting, could he use a mtb FD? Would that give him enough extension?

Kontact 

Did you try a braze on adapter that allows multiple angles, so you can push the derailleur outboard?


But we don't know if there is something else going on to take it well out of range, or if it is just the Tiagra 45mm chainline limit at work. I've found the operating range of some FD has a lot to do with the seat tube diameter.

Kontact 

Should be able to, unless the barrel on the shifter is maxed out with the amount of cable to pull. But I doubt it would be an issue.

alcjphil

In this thread I see tons of earnest effort to help the OP and almost none of the snark that often happens. My take is that it is perhaps time for a bit of trial and testing. I don't know what the rear dropout spacing the OP's bike has. If it is standard road 130mm, chainline would be 2.5 mm less than if it were 135mm mountain bike spacing. If that is the case, it might well make sense to move one of the 2 2.5 mm spacers from the drive side to the non drive side
Moving a spacer, if it works, is a zero cost solution

Kontact 

That would solve the problem, but it would make the cranks offset 5mm left.

You might be able to remove one on the right and use less than 2.5 on the left, depending on how much spindle is showing. As long as the plastic retainer in the pinch bolts snaps down, you're good.

well biked

Since the OP has bar end shifters (friction front shifter), all that's needed is a Shimano triple mtb front derailleur, and the front shifting problem should be solved. As I mentioned earlier in the thread, we have a Salsa Marrakesh touring bike in stock at my shop that is stock with an Alivio HT2 triple crankset and bb. The bottom bracket is installed correctly on the 68mm bottom bracket shell frame, which, again, means two 2.5mm spacers on drive side, one 2.5mm spacer on NDS.

Front derailleur is a Shimano Acera on the Marrakesh, bar end shifters are Microshift, front shifter, as always with bar end shifters, is friction only. Works great with this drivetrain.

Regarding the difference in Q factor between the old cranks and new cranks, I feel strongly that it's an absolute non issue, but that's just my opinion.

well biked

135mm rear hub spacing on LHTs.

Trogger

This has been an education for me and I very much appreciate everyone's helpful suggestions.

I'm taking th bike back to the shop this week to have it sorted out. But, now I am armed with more knowledge and the shop owner is aware of the issue and wants it resolved.

cyccommute 

Yes. Didn’t work and I’m not a fan of the braze-on front derailers because they have multiple angles and aren’t nearly as rigid as a clamp-on derailer. Basically, they made it issue worse.

It’s the chainline. Been there, done that, got the t-shirt. If it isn’t the chain line…which it is!…that’s also the best place to start, especially considering this comment from Trogger’s first post.

That is exactly what I observed the first time I tried to fit a Hollowtech II mountain bike triple to a road bike with STI shifters and a Tiagra front derailer.

Kontact 

The 4600 triple FD manual does say it has a 45mm chainline.

Trogger

BB shell = 68mm

There is a difference in distance from seat post to each crank arm of 5mm.

Tiagra deraiilleur is a band type.

Distance from centre of seat tube to middle ring is, I would say, more likely to be 50mm than 47.5 but that is using a retractable tape measure and eyeballs; harldy precise.

I realize, now, that I ought to have taken some measurements with my old crankset, for comparison.

I'm not sure the old crankset was a "road" crankset though I honestly don't know what determines "road" vs "MTB" vs "whatever" beyond the installed tooth counts (it doesn't seem to be the ring count; any can have 1-3 apparently); is there a difference between the various designations in where in space the rings sit relative to a common point of reference?

I dont understand what you mean by "people sometimes mount the cable above or below the bolt when it should be the opposite." I see just one bolt to crimp the cable and just a single, short, obvious path from crimp bolt to under-BB cable guide.

Trakhak

Just two weeks ago, I replaced the original Alivio triple crankset on my '95 Cannondale H300 hybrid with an Amazon-sourced off-brand Hollowtech II-style crankset and three chainrings bought separately as a set, also off-brand, also from Amazon. The tooth count on each of the new rings was close to that of the originals.

The suggested arrangement of the bottom bracket spacers put the chainrings too far out for the front derailleur to get the chain on the outer ring, so I moved one spacer (I think) from the drive side to the non-drive side. Might have been two spacers.

In any event, that solved the problem. Just checked: for what it's worth, which might not be much since yours is a steel frame and the Cannondale is aluminum, I can just barely fit a 6-mm Allen key between the small ring and the chain stay.

One crucial thing I did was that I abstained from messing with the front derailleur limit screws until I had what looked like the correct (6-mm) clearance between the ring and the stay. Once I hit the right arrangement of spacers, the shifting was pretty much perfect without touching the limit screws.

[Edit:] Just remembered that I did have to move the derailleur vertically to accommodate the new big ring. Up or down; don't remember. But I ended up with the correct clearance between the top of the ring and the bottom of the derailleur cage, which is about 1.5 mm, I believe. ("About the thickness of a penny," according to a quick search.)

Kontact 

5mm which way?

Bike Gremlin

With a Tiagra (RS500 is the model if memory serves me) BB, I threw out the 2.5 mm spacers on each side (leaving just one 2.5 mm spacer on the right hand side, so both cranks end up symmetrical from the frame's centre).
On a 68 mm hub shell frame.

Of course, after having done that, the axle protruded too much for me to engage the "thingy" on the left hand crank, that should get inside the hole on the axle. I just left it out and gave it a test.

Yup - there was still just enough "room" to set the bearing preload using the plastic end-cap-screw.

The cranks used are Sora "2x9".

They work well with an ancient road double FD. No play, no falling off or anything. The bike is used regularly, mostly for long rides on dirt roads.

Using friction shifters, but if the FDs movement range were unable to handle it (as is the case with the OP's FD), even friction shifters wouldn't have worked.

The point of all this is that the OP might give it a try without the spacers and see if the cranks would fit and if the FD would be able to reach the largest chainring when the chainring is moved another 2.5 mm inward - and also see if then the smallest chainring ends up being too close to the frame for the FD to shift onto. If the latter is the case, I suppose one could try adding a 1 mm pacer on each side, and see if that gets the cranks in the "sweet spot" for the FDs range of motion.

Relja So-Far-So-Good Novović

Trogger

Actually, in remeasuring, I find I misspoke. It's about 3mm difference (let's call it 2.5), the drive-side being a little longer, which makes sense, I guess, as it has 2 spacers vs 1 on the non-drive side.

Trogger

At the moment, there's about a 12mm +/- gap between the teeth of the smallest ring and the chainstay (which Surly had, on manufacture, 'dimpled' to afford clearance). So, that ought not be a concern if, say, the crankset was shifted, worst case, 5mm left (i.e. all 3 spacers on non-drive side).

Maybe I'll just get a hack saw out and chop a little off the spindle. A little superglue and, presto, Bob's your uncle!

Seems odd that Shimano just doesn't (I don't think) offer an Alivio triple 48-36-26 crankset to fit a 68mm BB sans spacers. Wouldn't that solve the problem? (Rhetorical)

Kontact 

If your outer chainring moved 2.5mm inboard, would that allow your FD to reach far enough?

Trogger

To be determined. Similar answer to chainline question.

cyccommute 

Keep the hacksaw in the drawer. Making one width of crank is a cost saving for both Shimano and the consumer. If they made two models, they would have to keep an inventory of both as well as machining for both. Twice the cost. Spacers are cheap and effective as well as allowing for a wider range of bikes the crank can fit on. Adjustment for chain line is also easier and cheaper for the consumer. Internal bottom brackets need to come in a variety of widths and it’s a bit of a trial and error method to find the right one if, for example, you want to use a mountain crank on a road bike. Mountain bike cranks tend to actually use narrower bottom brackets than road bikes because the crank curves inward at the spindle where a road crank doesn’t.

This is all fairly easy to do at home, by the way. The bottom bracket tool is relatively cheap and easy to use. The fastening bolts on the crank make it so that all you really need to take the crank off is a 5mm allen. The process is far less involved than removing an internal bearing bottom bracket. As a bonus, you aren’t without your bike for 2 weeks while it waits in a shop.