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Bike fitting - q factor

michaeltathammichaeltatham Posts: 5
edited October 2013 in Road beginners
I used to be a mountainbiker but have moved over to road for commuting and possibly competing in the future. For my transition bike I bought an alloy ribble road bike (running ALX Aclass wheels) that according to the scales was 9.5 kg, compared to 14.5 kg for my mountainbike. I was a bit disappointed by the lack of perceived performance improvement when cycling my commute to work (15 miles) on the Ribble so tracked timings over a few months, and basically once I'd got bedded into it the road bike only improved my speed by about 2 minutes over the course of an hour (on average) compared with the MTB. Being 90kg myself the simple arithmetic says my total mass has reduced by about 5%, so my timings have reduced about the same. But why do I not get the massive improvements I hear everyone talking about on here? Are people just talking nonsense and the perceived changes are psychosomatic; i.e. "The road bike should be faster, so I convince myself that it is"? I don't think it is just because I am used to the MTB, because I have been riding the ribble for over a year and have still noticed little difference.

Also I find riding the MTB much more comfortable and 'urgent', while the road bike is less so. So I spent a good bit of time trying to reproduce the seat/bars/pedals geometry on the road bike to match my MTB. I've also fitted a wider range cassette on the back to give me similar gearing. Still little change..! But one thing I did notice when switching between road and MTB was that my feet are further apart when pedaling on the MTB. A bit of research shows this is called the q factor

http://en.wikipedia.org/wiki/Q_factor_(bicycles)

Strangely no-one seems to talk about this when discussing bike fittings. I am quite a stocky build and have wide hips, so it seems logical for me to think that the narrower distance between the pedals may not suit me so well. Surely a leg that is vertical puts the power down more efficiently than one that is offset from vertical. Anyone any ideas on this? The problem is that this is very difficult to test. I don't even know of any crankset manufacturers who offer different q factor cranks.....

Posts

  • KajjalKajjal Posts: 3,404
    The big gains on a road bike v a mountain bike are slicker thinner tyres at a higher pressure, more aerodynamic riding position and less weight. I weight just under 100kg and find my XC mountain bike while fast off-road is slower on road than my road bike. Road bikes are a lot more sensitive to how you set them up than mountain bikes so have a read on bike setup which is the compromise between speed / power and comfort.They are also more sensitive to rough road surfaces.

    You may just find you are more suited to mountain bikes in the same way I prefer riding hardtail rather than full suspension mountain bikes.
  • MichaelWMichaelW Posts: 2,226
    Modern Q factors are quite wide. The main point of debate is how to narrow Q factor for smaller, slimmer riders so they dont have to pedal bow-legged.

    Road position is a bit different to MTB. MTB may has more weight over the rear wheel and a longer chainstay to alter the for-aft weight distribution. Cross country MTBs have a very low bar, comparable to the hoods of a road bike.
  • turnerjohnturnerjohn Posts: 1,249
    You may have got your mtb set up near road bike fit anyway ?
    If your riding a competitive speed your notice more of a difference ...don't see mtb's at road events !

    Look made a carbon pedal CX7 (I think) that was Q-factor adjustable but I've only seen on those pedals .
    Modern thinking seems to suggest reduced Q factor is better - reduced load on the axle and BB and less flex at the least
  • crankycrankcrankycrank Posts: 1,830
    Only a 2 min improvement for 15 miles is unusual I'd say. If memory serves I used to ride 6 miles to work switching between a road-race bike and a non-suspended MTB fitted with 1.5 inch road tyres and the difference was about 3 or 4 minutes in that short of a distance. I can only guess and say that possibly your bike is not fitted properly which can sap some of your power. Q-factor if not the right width can lead to long term problems with knees, ankles, etc. I'm an older guy and finding the proper width is easy as my knees will scream if it's off by a 1mm or 2 but it's very hard to determine if your not experiencing any discomfort. Long rides always seemed to sort this out for me in my younger days. The knees would start to feel as though they were being twisted after 50 miles or so if my stance was off. You can widen the QF by moving your cleats or adding several mm of shims to the pedal spindle where is screws into the crank or some mfrs offer longer spindles for their pedals. If all else fails there doesn't seem to be much point in keeping road bike if you're happier on the MTB.
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