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Old 05-20-10, 08:47 AM   #1
jmenking
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Retrofitting Triple on '05 Poprad for Long Tour - Help!

Hey readers,

I posted this in the Maintenance/ Repairs section as well.

Going on long tour, many mountains.

I'm trying to put a Shimano Ultegra triple (26-39-52) on my '05 Lemond Poprad, which is currently fitted with a Shimano Ultegra double (39-53). There is just a hair's space between chainring and chainstay, so I believe I am going to need a longer bottom bracket.

Yesterday I tried measuring the axle length of the BB (Shimano octalink), and I measured somewhere around 111mm-112 mm. I think these are not actually Shimano BB sizes, so 113mm or maybe 109.5 mm and chalk it up to the inaccuracy of my measurement? I didn't actually remove the BB, just took the crank arms off and held up the ruler.

Will I be able to fit a longer BB on this bicycle in order to accommodate the triple? What are other solutions?

External BB?

What about a compact? Could I put a chainring smaller than 30T on a compact and still conquer some mountains?

Thanks!
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Old 05-20-10, 09:17 AM   #2
sstorkel
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Originally Posted by jmenking View Post
I'm trying to put a Shimano Ultegra triple (26-39-52) on my '05 Lemond Poprad, which is currently fitted with a Shimano Ultegra double (39-53).
Are you sure the smallest chainring is a 26? Ultegra triples are usually 30-39-52. Most Shimano triple front derailleurs are designed for a maximum difference of 22 teeth between the largest and smallest rings. This spec is conservative, so it wouldn't surprise me if a 26-tooth jump works... but you may not get Ultegra-quality shifting.

Quote:
I didn't actually remove the BB, just took the crank arms off and held up the ruler.
If you remove the BB, it may have a label that tells the exact size. Depending on what conditions you've been riding in, it may or may not be readable...

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Will I be able to fit a longer BB on this bicycle in order to accommodate the triple? What are other solutions?
You can probably fit a longer BB. Whether your FD will have enough extension to push the chain onto the outer chainring is the real question. This is where buying from a LBS helps: I had to swap BBs several times when trying to upgrade one of my older bikes. Your best best is to use the narrowest BB that gives you the clearance you need. If you push the chainrings too far from the frame you screw up your chainline and then things can start to get difficult...

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External BB?
Is your crank designed to work with external BB cups? If not, this isn't an option. Even if it is, the external cups are designed to produce a specific chainline and there's very little adjustability.

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What about a compact? Could I put a chainring smaller than 30T on a compact and still conquer some mountains?
Unfortunately, I don't think you can put anything much smaller than a 30T ring on a compact crank.

When I did my credit card tour down the Pacific Coast, I decided that neither a compact crank nor a standard road triple provided low enough gearing. I could pedal the compact over any single hill, but at the end of a day's worth of hills my legs were done! I ultimately ended up with a Shimano Deore M532 trekking crank (48-36-26) coupled with a Shimano Ultegra SL drivetrain and a 12-27 cassette.
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Old 05-20-10, 09:33 AM   #3
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Are you sure the smallest chainring is a 26? Ultegra triples are usually 30-39-52. Most Shimano triple front derailleurs are designed for a maximum difference of 22 teeth between the largest and smallest rings. This spec is conservative, so it wouldn't surprise me if a 26-tooth jump works... but you may not get Ultegra-quality shifting.
Well, the LBS is going to swap the 30 for a 26 they have on a different triple. Although, I'm pretty sure the 26T is coming off of a used Ultegra. Must have been retrofitted by someone else.


Quote:
You can probably fit a longer BB. Whether your FD will have enough extension to push the chain onto the outer chainring is the real question. This is where buying from a LBS helps: I had to swap BBs several times when trying to upgrade one of my older bikes. Your best best is to use the narrowest BB that gives you the clearance you need. If you push the chainrings too far from the frame you screw up your chainline and then things can start to get difficult...
Sounds like I may need to turn this over to the LBS.


Quote:
Is your crank designed to work with external BB cups? If not, this isn't an option. Even if it is, the external cups are designed to produce a specific chainline and there's very little adjustability.

Unfortunately, I don't think you can put anything much smaller than a 30T ring on a compact crank.

Sounds like these aren't options, then. Thanks for the advice!
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Old 05-20-10, 10:28 AM   #4
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Originally Posted by jmenking View Post
Sounds like I may need to turn this over to the LBS.
If you've got a BB wrench, it's an easy DIY project. Just pull your old BB and take it to the LBS. Stand it vertically on the parts counter and buy a new one that's a little bit longer. If you've got a square taper BB, your LBS probably has several common Shimano sizes in stock that you can compare side-by-side. Octalink might be more difficult to find, but a well-stocked LBS should have those, too.
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Old 05-20-10, 10:34 AM   #5
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Just get a different BB... or maybe try a spacer.
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Old 05-20-10, 10:58 AM   #6
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Keep in mind how much smaller the 26T is going to be than the 39T. That might make the difference clearance-wise. Then you only have to worry about inward FD travel. I just swapped to a triple on my touring bike from a compact double. The FD had JUST BARELY enough travel to shift to the small ring. Good enough to shift well to all gears though. If I had gone to a longer BB, it would have moved the chainline out too far for the middle and outer rings. What is the chainline measurement of your current setup?
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Old 05-20-10, 09:58 PM   #7
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Well, we got it to work. A 118.5 mm BB was enough for clearance. The triple has a swanky 26T chainring on the bottom which is sure to be appreciated on the big climbs. Surprisingly, the 105 FD and 105 RD work fine. The RD, although a short cage, hits each gear without problems. The FD takes a little coaxing to get into the small chainring, so I may replace it with a true triple FD.

Thought any future Poprad-ers should know that you can retrofit a triple without that much hassle.
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Old 05-21-10, 03:44 AM   #8
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Retrofit of a triple on just about any bike is possible, and as you found, the 118.5mm BB was the appropriate thing to go for. The most critical factor is not necessarily the crankset and BB, but whether your shifters are triple-capable. I am a little surprised the standard double FD works, but not surprised that the RD works -- although you might get issues in cross-chaining.

I recently fitted a triple Ultegra to a CF frame, complete with Ultegra Octalink II triple (the left shifter was already triple-capable). However, the rear cassette is a 32-11, and an XT SGS RD was fitted to enable everything to work smoothly. And it does.

I also fitted a 26-36-48 MTB Octalink II crankset to Machka's new Ti frame, with a triple Ultegra FD, and the same set-up on the rear, and it, too, works well.

Just for a future reference, and for those considering similar types of changes, the BB specs are available on the www.shimano.com website under the North American cycling tab, then technical documents. The documentation with new components also contains the specs.

Last edited by Rowan; 05-21-10 at 03:50 AM.
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