Trogger

On my long haul trucker, I recently replaced a square-taper BB with hollowtech and a Shimano Alivio crankset. (Reason: there's a dearth of ramped chainrings to replace the worn ring of my old, 5-bolt crankset)

Problem: I can't find a way to adjust the front Tiagra derailleur (triple; seat tube clamp) to successfully change to the big ring. It works fine switching between the small and middle rings. If I fully extend the derailleur with my finger, it seems to come up short of what's needed.

Adjusting the derailleur has always been difficult, so I don't know if my current problems result from my continued ignorance or, for example, the new front cogs do, in fact, sit farther from the bike centreline and thus out of reach of the derailleur.

Can anyone shed some "yes... of course... I know exactly what you're talking about, and here's what you should check" light?

Thanks!

shelbyfv

Did you add any spacers to the HT bb?

Trogger

Thanks for your reply.

In my research, I did find many references to spacers, but the BB and crankset were installed by a LBS and I don't know if they included spacers.

Is there an easy -- i.e. just by looking -- way to check?

shelbyfv

I'm sorry, I don't know if a spacer would be obvious. I've never used spacers with a HT bb but I know they exist and could mess with the chainline. If you paid a shop they should sort it out for you.

Andrew R Stewart 

So, the shop installed a new crankset and BB and didn't also check and/or readjust the front shifting? Did they at least say something about the issue? Andy

Trogger

Ya, I know.​​​​​​ They did mention something but, given the previously-experienced finickiness (it's truly a pain, but maybe that's just the way of a triple) of this derailleur -- it's not the first bike shop that hasn't adjusted it well -- I figured I would fix it once I got it home.

I'll be taking the bike back to the shop and chatting with them if I can't sort it out this weekend.

Trogger

Yep, I'll be taking the bike back to the shop.

alcjphil

The spacers can be seen by looking closely at the outboard BB cups. Your BB shell is likely 68 mm wide and the crank is designed for a 73 mm wide BB shell. Spacers are needed to take up the 5 mm narrower BB shell width on your bike

Iride01 

What was the original crankset and BB? A Tiagra front DR is probably made for a more typical chainline for a road group. A 10 speed Tiagra crank has a chainline of 45. Your Alivio might be 50mm if it's the 3x current product.

Some of those 2-piece Shimano cranks that aren't for the road group sets, need a spacer, depending on the bike and the BB along with whether the BB shell is 68 or 72 mm.

Trogger

All good info.

Yes, to my knowledge, Surly outfitted the stock LHT with mtb drivetrain, presumably to get the granny gears.

The current model Disc Trucker uses the Alivio triple crankset, which is the reason I went with it (and the LBS agreed would work).

I confirmed on the LHT specs that it's a 68mm BB width. And I can see two spacers, presumably 2.5mm each, on the crank side. (I'd post photos but, as a new member of this forum, I'm not yet able). I also did a tape measure comparison of the gap between each crank and the seat tube. Darned if the distance isn't 5mm. I therefore expect, perhaps, that the crankset is shifted 5mm further out which throws off the chainline and puts the big ring beyond the derailleur's reach.

Not to mention that one foot sits 5mm farther out on the pedal than the other.

Does that reasoning make sense?

So, the spacers are there simply to account for a too long (for situation) crank axle?

Might this be fixed by moving the spacers to the left crank?

The current Disc Trucker also sports a 68mm BB. The LBS had one on the sale floor so I can check to note its geometry.

Thanks for the info thus far; it's very helpful.

Kontact 

There's no reason I can think of for there to be two spacers on the drive side. The spacers are there to fill in the difference between a 68 and a 73, which are both symmetrical.

That's likely the problem - unless your front derailleur still only has range for a standard road chainline.

maddog34

Alivio is an MTB group... and you have a.. what type of bike? Road.

Road Bottom Bracket width is 68mm...

MTB BB width is now 73mm. Some older MTBs used a 68mm BB width

possible Solution: you should get a ROAD width Hollowtech II Crankset.

alcjphil

OP's bike is a touring bike. It is very common to install mountain bike cranks on touring bikes in order to have low gearing for loaded touring. My touring bike is equipped with a mountain bike crank for this very reason:

maddog34

so how did your chainline work out? any issues? how did you solve them, if so? Also, how does having the much wider Q-factor effect your ride quality? did you consider a larger Low Gear in back instead of installing the wider crank in front? if so, what prompted that decision?

well biked

For your Alivio mtb Hollowtech II crankset on your LHT frame with 68mm bb shell: two 2.5mm spacers on driveside, one 2.5mm spacer on non drive side. That will achieve the desired chainline on your LHT frame.

One thing I don't think I've seen mentioned in the thread, but maybe I missed it, is whether you have adjusted (loosened) the high limit screw on your front derailleur so that it can move further to the outside. The Tiagra triple FD is obviously a road FD, designed for a road drivetrain, so it might well be that it won't allow movement far enough outside to accomodate the Alivio crankset. If so, switch to a mtb triple FD (Acera, Alivio, etc) and use a friction shifter for front shifting, if you don't already have that. I've sold a lot of LHTs at my shop, and almost all of them have come stock with bar end shifters, with the front shifter by default being friction shift only.

alcjphil

Chainline is fine, I put 2 spacers on the non drive side and one on the drive side. It also helps that the derailleur is designed to work properly with that crank with its smaller chainrings

alcjphil

The OP already has 2 spacers on the drive side. Moving one of them to the non drive side would move the chainline inward

WizardOfBoz

It should be easy to measure the distance from centerline to each sprocket. Measure the seat tube diameter, D, with a mic or a caliper. Measure the distance from the seat tube to each chainring with at ruler. Add half of D. You'll have offsets for small, medium, and larger chainrings, Os, Om, OL.

In the general case, aren't specs available that tell you what the offset range of the FD is? This would seem to me to eliminate guessing.

But to the OP's point, alcjphil has a practical and actionalbe idea it seems to me.

maddog34

yep.. the Derailleurs specifically designed for Road and MTB sized Chainrings have many carefully engineered features... all those odd bumps and arching ridges have purpose.

well biked

With a 68mm bb shell and a mtb Hollowtech II crank, there should be three, 2.5mm spacers, one on NDS, two on drive side. If it were a 73mm bb shell, just one 2.5mm spacer on the drive side, no spacer on the NDS. That's where you start, that's the correct way to set up a mtb HT2 crankset with 68 and 73 bb shell widths.

We currently have a Salsa Marrakesh touring bike in stock, a close cousin of the LHT, the bike is stock with a 68 shell and an Alivio HT2 crankset/bb. It has friction shifters and an Acera (triple, mtb) front derailleur. I've sold a bunch of LHT's that had a Tiagra triple FD such as the OP's, but those bikes used square taper touring cranks/bb's. I imagine the mtb triple FD will be necessary in the OP's case, because of the Alivio HT2 crankset with mtb length spindle.

cyccommute 

There should be 5mm of spacers on the crank. Mountain bike cranks are wider than road cranks and, to work with a road derailer, you need to move some of the spacers from the drive side to the nondrive side. You may need to move all of them to the nondrive side or you may need as little as a 1mm spacer on the drive side. I’ve done this successfully on 4 bikes without issues. I’m using indexed STI shifters on all 4 bicycles.

well biked

Regarding spacers, how many, where they go for various shell widths, etc, scroll to page 12 in this Shimano doc for HT2 bb installation for mtb cranks. For reference, (A) in the diagram is a 2.5mm spacer:
https://si.shimano.com/en/pdfs/dm/FC...002-16-ENG.pdf

Trogger

My reply has been delayed due to "new member" restrictions.

My thanks for all the replies; they've been very helpful and educational.

I am a little concerned with having Q-factor (another newly-learned term) different on each pedal, caused by asymmetrical spacer placement; 5mm difference may not seem like much but it does force a different geometry on the two sides of the physiology.. Comments? I note one suggestion to move one existing spacer to the non-drive side, thus making symmetrical.

A couple of detais:

The new crankset is Shimano Alivio T-4060 (Shimano assigns the family descriptor "Trek" rather than "MTB" for this model) which is the same one used on the current Disc Trucker. The road options don't providee the necessary 3-ring tooth counts (e.g. 48-36-26). It seems Trek is an invented happy medium between MTB and road; a good fit for touring.

I'm 95% certain that, with the 5mm total drive-side spacers, the crankset now sits at least 5mm farther away from the centreline than did the previous, stock, sq-taper mounted Andel triple -- thus messing up the front derailleur and the chainline. I will verify at the shop with a look at their floor model Disc Trucker and go from there viz necessary changes to make it work.

According to the Surly spec sheet, the stock 2010 front derailleur (currently installed) is Tiagra FD-4503BS triple. surlybikes.com/uploads/downloads/2010_Surly_Catalog.pdf . The current Disc Trucker uses a Sora R-3030 (nominally a road model). I am certainly puzzled why Surly is, according to the Shimano website bike.shimano.com/en-US/home.html, mixing-and-matching MTB, Trek and road components when there exist same family components. A mystery. It's also a little odd, in my mind, that the derailleurs are not designed with a little larger range of travel than nominally necessary, which can then be limited with the L and H screws.(particularly with a friction shifter). But I'm still pretty much novice at bike mechanics, so what do I know?

Thanks, again, for the help!

base2 

Trekking as in synonymous with touring. Not Trek, the bike company.

Much of the engineering translates between different product groups. So, much compatibility exists. It's very common to mix-n-match components to achieve a desired result.

alcjphil

I checked my own touring bike again to see how I installed the spacers. The bike has a RaceFace Turbine crank that was designed for 3x9 drivetrains. The chainrings are 42- 32- 22 giving me nice low gearing even though my cassette is a 12-28 8 speed. The best setup for this bike is to have a single spacer on the drive side and 2 spacers on the non drive side. My front derailleur is an older Shimano STX which was actually designed for 3 x 7 setups. With 2 spacers on the drive side I was having a bit of difficulty shifting to the large chainring, so I moved one of the drive side spacers over to the non drive side