Mountain Gear

Tech FAQ: Getting Pinned by 2X10

A reader says his new 2x10 drivetrain was the wrong choice. Tech-guru Lennard Zinn says a modification is possible.

Dear Lennard,
I just got a new bike with a SRAM X.0 2X10 group about a month ago. The chainrings are 26-39, and the cogs are 11-36 (10-speed).

What can I do? Can I make it into a triple?
-Greg

Dear Greg,
TechWidgetYes, you can make it into a 3X10 system, but you’ll have to replace the crankset, left shifter, front derailleur, and, probably, chain.

Thing is, I’m not as young or as light as I used to be, and it’s kicking my butt. I got it because the guys at the bike shop were raving about it – how it was the latest, best thing and all, but I didn’t think it through very well. I just really need a much lower gear than I have. One of the reasons I went out and bought a new, lighter bike is so that I could climb better, and now I can’t even make it up climbs I used to ride on my old bike.

I know the concern, as with the 2X10 you do lose the top end and low end of a 3X9 22-32-44 with 11-34 system. The 22-34 low gear is a 17-inch gear on a 26er and an 18-inch gear with a 29er. Compare that to the 2X10’s 26-36 low gear, which is a 19-inch gear on a 26er and a 20-inch gear with a 29er. The 3X9’s 44-11 top gear is a 104-inch gear on a 26er and a 113-inch gear with a 29er, while the 2X10’s 39-11 top gear is only a 92-inch gear on a 26er and a 100-inch gear with a 29er.

Your left shifter only has two click positions in it. You’ll need one with three click positions.

I know from experience that that front derailleur will not work well with a triple crank, even with a triple shifter. It will tend to throw the chain down from the big ring to the granny ring, bypassing the middle ring, even though you would have only given it a single click with the shifter.

The chain will likely need to be longer, since your top gear will now be a 44 X 11 or the like, rather than 39 X 11. And you don’t want to add a link to a 10-speed chain, especially on a mountain bike, as you are likely to someday shift the front derailleur under high load. That’s asking for a broken chain.

To stick with SRAM and the 10-speed-specific parts, you could get a 3X10 SRAM X.9 or X.7 crank, front derailleur, and left shifter, along with any SRAM 10-speed chain. Thing is, you may not be able to get a shifter that fits onto that nice sliding clamp on the brake lever that the X.0 shifter fit onto.

Expect these parts to cost you at least $350 without labor. You can also substitute a Shimano 3X10 crank, front derailleur, left shifter, and chain into this system, and it will work fine.

On the other hand, I also know from experience that you can slap an old 9-speed triple crank, front derailleur, and left shifter on there, along with a 10-speed chain, and it will all work fine with your 10-speed chain, cogset and rear derailleur. You can use SRAM or Shimano for the shifter and front derailleur, too. I recently combined a 2009 X.0 left shifter, Shimano XT front derailleur, and one of our long (in this case 210mm) Zinn triple MTB cranks with a 2010 X.0 10-speed group, and it not only worked fine, but the left shifter mounted onto the same sliding mount on the left brake lever band clamp, and the colors of the shifters matched, even if the styling was a bit different.
-Lennard

Dear Lennard
Regarding the Oct. 26 posting on carbon and solvents and lubricants; I’ve been using rubbing alcohol to get all the tough stains off my carbon frame (matte finish) and also to make it shine a bit. Does anyone know if that will ruin my carbon frame or paint?
-Byron

Dear Byron,
I have been getting variations of this question for years, and the answer is always the same: no. That was my intention by posting this column, to cover all of the bases enough that everyone would be clear that solvents and lubricants that one commonly uses on bikes do not damage carbon fiber (click on the graph if it’s too small to see). Rubbing alcohol, being about as mild a solvent as you’ll find, certainly will not damage a carbon frame. Isopropyl (rubbing) alcohol is a lot milder solvent than acetone, and you saw how that did nothing to the carbon structure, even in cross section. Of course, use an abrasive rag with enough elbow grease, and you could dull the finish by simple abrasion, but it’s not the alcohol that would have caused the problem.

If you want to know a solvent that will damage carbon, then know that paint remover – the stuff you smear onto a car, for instance, to cause the paint to bubble up so that you can peel, scrub, rinse and scrape it off, will attack the paint on as well as the resin within a carbon frame. But I can’t imagine any reason why anyone would ever put that on a carbon frame. Warning about it is equivalent to mentioning that putting a carbon frame under a car tire and driving over it will damage it.
-Lennard

Dear Lennard,
I have a 2010 Trek FuelEX with carbon frame and a carbon seatpost. Seatpost and frame seemed fine without any lube, but I bought some FSA carbon prep anyway. After a very light application, the post would creak when subjected to even moderate loads. So I cleaned off the post and frame and the creaking subsided.

Is creaking a common problem with carbon prep?
-Paul

Dear Paul,
Where there’s movement between highly loaded parts, there will be creaking. The assembly paste is designed to create pressure where there is separation between parts, and with that separation, there can often be movement and creaking. Grease, on the other hand, stands out as a creak remover, since it migrates to the larger spaces and moves out of the tight spaces. So if it doesn’t slip, then just grease it.
-Lennard

Readers can send brief technical questions directly to Lennard Zinn.

Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.

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