Ask a Mechanic | 2×10 Mountain Conversion & Tight Fitting Tires

Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at daniel.slusser@artscyclery.com. Today’s column discusses the inticacies of a partial 2×10 conversion and an unusual question on tire installation.

Question

I hope you can help me with a few answers to my questions after getting different ones from my dealers here in Germany. Here is my bike and setup: Lapierre Zesty 314 model 2011, Race Face Deus Crank 22/32/44, 9-Speed Shifters, Front Derailleur, Rear Derailleur, Chain, & 11-34 Rear Cogs are all 9-speed. I have bought 2 Race Face front rings 24/36 (64 and 104 BCD) which will be mounted on the granny and middle positions on the crank. I want to upgrade my front derailleur to an XT, but I will need an E-Type because Lapierre has a low direct mount, which means I just need to take off the BB plate holder and screw the derailleur onto the frame.

Here are my questions: Can I use a 2X10 front derailleur or will this setup only work with a 3X10 front derailleur, or even a 3×9? Here are the 2 models I had in mind: Shimano XT FD-M780E 3×10 or the Shimano XT FD-M785E 2×10. On the back of my Race Face 10-speed rings it states to only use the rings with a 10-speed chain, but my dealer is saying use a 9-speed for my setup. What do you think? I really hope you can help me, as I am a little confused and don’t want to order 3 different parts to see what works! From: Shaun

Always use 10-speed chains with 10-speed rings.

Answer

Great question Shaun! Since you are using 10-speed rings you should use a 10-speed chain and front derailleur. A 9-speed chain and front derailleur might work ok but the 10-speed will work better. The reason for this is because the spacing between the rings is slightly different. This is also the reason why a 10-speed front derailleur works better in this situation with its narrower cage that is optimized for the narrower chain and chainring spacing. The 10-speed chain should work just fine with your 9-speed cassette.

For the front derailleur: neither options you are considering are going to be optimal since the double front derailleur is made for a 38-40t middle/big ring and the triple front derailleur is made for a 32t middle ring. To make things trickier the e-type mount doesn’t allow for any adjustability. My first inclination is to go with a double derailleur however. I checked with two Shimano tech reps to see what they thought and they both independently recommended the double derailleur without first knowing which way I was leaning or knowing the other one’s response. So go with the XT FD-M785E 2×10 derailleur.

Your 9-speed front shifter should work ok but it might be hard to shift (extra effort at the shifter required) up to the 36t ring with it because you will be up against the outer limit screw of the front derailleur. This is because the 9-speed shifter will pull slightly more cable than a 10-speed one and will want to push the derailleur farther outboard than you will likely want it to go. Either that or the derailleur will rub on the chain when you are in the large cog and 36t ring. The best bet is to replace the front shifter with a 10-speed DynaSys unit that incidentally works with both double and triple cranks. Best of luck Shaun!

Don’t saw on your tire bead with one of these.

Question

I had a flat out on the trail and my Hutchinson wire bead tire was so hard to get back on that I just gave up and walked home. My friend says that I should have just cut the bead to get it back on. Would the tire stay on after cutting the bead? From: Jim

Answer

No.

Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly University. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.

2014-03-05T16:11:49-08:00