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I would like to put an Road crank on my MTB, I basically only use it for commuting and I all the time find myself in the highest gear, 42/11...

Is it possible to exchange my Shimano Deore HT2 crank with an Road-crank (with 50/34 tooth Wickwerks blade) or Cross-crank (with 46/36 tooth Wickwerks blade), are they compatible with the rear freewheel (Shimano 10 speed 11/34) and chain, and is it possible at all, can a Road bottom bracket fit into a MTB frame....???

-I know 34 or 36 tooth might be a little big as a smallest front blade, but I am from flat Denmark, I´m not going to climb mountains....

Bjarke

EDIT, I can see that most people recommend changing just the blades and I guess thát is what I´ll do, can anyone point me to a 44/46/48 tooth blade (which should be enough, plus some sort of an "granny", I do think I will need a two-blade setup up front, not just a single) which will fit a Shimano 10-speed HT2 4 bolt crank, the Shimano jungle is not for beginners....???

The bike I will buy is this one http://www.feltbicycles.com/Sweden/2014/Bikes/mountain-29/nine-series/nine-3.aspx and I hope it will accommodate the higher tooth-count, otherwise I will just need to go with 44 teeth which will probably be fine with regards of gearing, but with regards of wearing out the 11 and 12 in the back it is probably a little low....

The bike where 42/11 was too little was a 26" and the Felt is a 29" with 38/11 as the highest gearing, without having calculated on it, I think the Felt is a little lighter in the heaviest gearing.... -In the end I guess 44 is close to plenty....

With regards of cadense, the really heavy gear is for the (flat on the road) downhill with both the wind and the sun in the back, I do have a little low cadense though, but can´t really get away from it, old habits You know....;-)

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  • Not an answer on your question, but most Shimano cranks have a version with more tooths.
    – Eric Smekens
    Commented Jul 3, 2014 at 13:14
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    It'll depend on your frame. The problem isn't whether the bracket will fit, it's whether larger chainrings will hit your chainstay, especially when changing from a triple to a double moves them closer in.
    – armb
    Commented Jul 3, 2014 at 14:21
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    You can get 46t and 48t Deore chainrings. Keeping the same crank and using larger chainrings might be better and/or easier than using a road crank.
    – armb
    Commented Jul 3, 2014 at 14:23
  • Clearly the easier option is to put a bigger chainring on the existing crank but in 104 10 speed I am not finding one. You need to check the width on your shell. The bb needs to match the shell and the crank needs to match the bb. Post the bb on the bike now.
    – paparazzo
    Commented Jul 3, 2014 at 15:35
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    This question pops up quite often. Most often the riders cadence is too low. 42/11 at a cadence of 80 is 38km/h, at 100 its 47km/h. What speeds are you riding at?
    – mattnz
    Commented Jul 3, 2014 at 22:07

3 Answers 3

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(As requested, turned comment into answer.) - This question pops up quite often.

Most often the riders cadence is too low. Presuming 26" wheels with 2" tires, 42/11 at a cadence of 80 is 38km/h, at 100 its 47km/h. What speeds are you riding at? If you are maintaining these speeds on a solo commute on a MTB, you should get in touch with your national cycling body ASAP, I am certain you will be invited onto a development squad.

As a first step measure how fast you are pedaling. No need to get a cadence computer, although it would be easier, as counting 100 in 1 minute is not all that easy. At your cruising speed, count your pedal stokes over 10 or 15 seconds and work out your cadence. If it is above 80 go ahead and make the changes to the bike (and make that phone call). If its below 70, improving riding technique would far be more beneficial (and probably more cost effective) than increasing gear-inches.

I can't help a lot with technique, mine's awful:), but a few ideas would be to read up and watch videos on the net, ask a (road) cycling mate, or join a club or pay for some coaching.

This question - How can I improve my pedal stroke? might provide some useful tips.

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Yes, but with some caveats:

  • Road rings are big. You might have clearance issues with the chainstays.
  • Bottom bracket. You might need a new bottom bracket to fit the spindle or change the spacing.
  • New chain. Bigger rings require more chain (usually).
  • Front derailleur. Derailleurs are meant to handle certain sizes, spacings, and mountings, your current one may not work.

Depending on the arrangement, there might be more things but these are the top ones that come to mind.

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There are two issues.

  1. Will the chainring and crank clear the stays?

Many modern MTB's are designed to only have a maximum chain ring of 44t or so. They are also designed for the relatively wide Q-factor of MTB cranks vs road cranks.

  1. Can you get the front derailler high enough to accommodate the larger chain ring?

Switching to a single ring in front solves 2 and you can get single rings for your crankset up to 50t. 50/34 is still a pretty low gear on the roads.

Blackspire makes them. http://www.blackspire.com/qs/product/83/5948/263228/0/0

Adding some spacers to the chainring bolts can help with the clearance issue.

As far as the chain goes, if the cranks are spaced for 10 spd then you should have no problem. The only real problem occurs when the chainrings are far enough apart that the skinny 10spd chain can get jammed between the chainrings.

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  • "Adding some spacers to the chainring bolts can help with the clearance issue", but then I will need an longer bolt too, I guess, where do I find thát, anyone....???
    – Easer
    Commented Jul 4, 2014 at 11:51
  • You already have "long" chain bolts. The bolts for a double are much wider than needed for a single chainring.
    – Fred the Magic Wonder Dog
    Commented Jul 4, 2014 at 14:22

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