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Run out of gears !

JCJCJCJC Posts: 162
edited May 2010 in MTB workshop & tech
Hi,

I have an Orange P7 (2008) which I use for commuting (seperate set of tyres) as well as offroad. I am finding however that I run out of gears on the flats and downhill - i.e. I want some higher gears as the pedals are spinning fast and I feel that I have more power to give.

How do I best address this? Can I get a new smaller bottom cog at the back (or larger at the front), or do I need to replace the whole cassette. What about chain length ?

Many thanks
JC

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    so what size is the cassette? and what size are the chainrings?

    11T is the smallest rear cassette cog.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • JCJCJCJC Posts: 162
    Not sure - I would need to check. Whatever it came with "off the peg".
  • Down the RoadDown the Road Posts: 949
    Only real option is to put a 48/36 combination on the front. Larger rings will raise your gearing by about 10% but your main problem is you are using this bike the wrong purpose.

    Mountain bikes are for riding off road and hybrid or road bikes for on road. Basically the wheel is too small on a MTB for road use.
    Racing is life - everything else is just waiting
  • peter413peter413 Posts: 5,120
    Is it a double or a triple chainset
  • JCJCJCJC Posts: 162
    Down the road. Thanks - can you explain this in laymans tems though. Can I just replace the largest ring, or are you saying that I need to replace all three? I find that other two are fine for offroad use.

    I can't afford the luxuary of two bikes ( I have enough expensive hobbies as it is), hence trying to tweak my P7 to do two jobs.

    Peter413 - it is a triple

    Thanks again
    James
  • Down the RoadDown the Road Posts: 949
    You could maybe get away with just the outer but I would do both
    Racing is life - everything else is just waiting
  • nyanzanyanza Posts: 68
    You get the biggest gains per teeth if you make changes at the back. So, going from a 13 tooth to an 11 will give you a much bigger gear than changing from 42 to 44 on the front. So, start at the back, and if you are still running out of gears then make changes up front with a bigger outer ring. That's a bit more hassle as you might have to shift you front mech up the seatpost to make room for it.

    I run an 11/48 on my commute and never run out of gear in the city and no one ever overtakes me! I have another bike which has 14/42 which is useless for a commute. Sheldon's gear calculator lets you play with teeth combinations and shows you how to make the most efficient changes to your ratios.
    http://www.sheldonbrown.com/gears/
  • supersonicsupersonic Posts: 82,708 Lives Here
    So what is your gearing, and what cadence are you spinning at max speed?
  • The RookieThe Rookie Posts: 27,804
    I commute on a touring frame kitted out with mostly MTB parts, I have a 46T front and an 11/34 rear cassette and that copes with all I need, I spin at about 90rpm.

    Count the teeth (or find the markings) on the rear (only really need the smallest) and front gears (largest) and repost so we know where we are starting.

    Simon
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • JCJCJCJC Posts: 162
    I will check (re number of teeth) and update this thread shortly...
  • Having commuted and MTB'd on the same bike and the best thing I did was buy a road bike for the commute to work. No need to swap tyres,if I crashed the MTB I could still get to work and it is much quicker. Might be worth getting a cheap commuting/road bike second hand ?

    If not I wouldnt recommend changing the drietrain to suit road as climbing offroad will be hell if you are geared to highly.

    £1.25 for sign up http://www.quidco.com/user/491172/42301

    Cashback on wiggle,CRC,evans follow the link
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  • JCJCJCJC Posts: 162
    Maybe, but 1) the extra cost and 2) sometimes there are fun jumps, sets of steps to jib around on on the way home for which I can unlock the front forks and go for it !

    What is a drietrain ?
  • Its a drivetrain with a typo amazingly. Or are you being serious? Judging by asking noddy questions about fitting a bigger ring to an MTB triple you probably are.

    £1.25 for sign up http://www.quidco.com/user/491172/42301

    Cashback on wiggle,CRC,evans follow the link
    http://www.topcashback.co.uk/ref/MTBkarl
  • JCJCJCJC Posts: 162
    I am being serious. Wouldn't a drivetrain be the entire mechanism that we are talking about anyway...?

    I dont see why asking questions is "noddy", surely this is the whole point of this forum...? And what is wrong with changing parts on a bike to make it suit a riders needs better ?

    Re teeth - I have 44 on the front and 11 on the back.

    Cheers
  • supersonicsupersonic Posts: 82,708 Lives Here
    44/11 gives about 34mph at 120rpm.

    You can work out the maths yourself if you know the wheel diameter.
  • JCJCJCJC Posts: 162
    Cheers, so should i go for a bigger front cog or small back ?
  • nicklousenicklouse Posts: 50,675 Lives Here
    JCJC wrote:
    Cheers, so should i go for a bigger front cog or small back ?

    before that can be answered we need some info from you, as you said you would.

    but i dont think you will be able to go smaller on the rear.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • stu8975stu8975 Posts: 1,334
    JCJC wrote:
    Cheers, so should i go for a bigger front cog or small back ?

    How fast are you actually travelling with your current set-up? are your legs spinning at 120rpm?
  • JCJC wrote:
    I am being serious. Wouldn't a drivetrain be the entire mechanism that we are talking about anyway...?

    I dont see why asking questions is "noddy", surely this is the whole point of this forum...? And what is wrong with changing parts on a bike to make it suit a riders needs better ?

    Re teeth - I have 44 on the front and 11 on the back.

    Cheers

    I was being flippant like yourself picking up a typo when someone is trying to give advice. And when I said changing the drivetrain you are correct I didnt mean as a whole just the ratios by changing the front rings. I have a 44 tooth front and 11 back and can get a pretty decent speed on the road. It may be that you just have to train yourself to pedal at a higher cadence.

    There is nothing wrong with changing your bike to suit different needs but there are limits where making compromise affects the offroad side of things. You could fit a touring crank like this. http://www.winstanleysbikes.co.uk/produ ... ranks_T661

    But it would make quite a difference to your lowest gear. Apologies for being grumpy,had a banging headache and feel knackered.

    £1.25 for sign up http://www.quidco.com/user/491172/42301

    Cashback on wiggle,CRC,evans follow the link
    http://www.topcashback.co.uk/ref/MTBkarl
  • thelonegrooverthelonegroover Posts: 1,073
    I've ridden my mountain bike on plenty of roads, flat, up and down and to be honest top gear was more than high enough, even on the steepest downhill sections. (Which I tend to freewheel anyway). You must be doing nearly 40mph on the flat!
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  • JCJCJCJC Posts: 162
    "before that can be answered we need some info from you, as you said you would."

    What info do you need?

    44 on front, 11 on the back. No idea on cadence though
  • diydiy Posts: 6,473
    Cadence would be around the 110 rpm mark at 35-40mph*, on that gearing. One option would be to change to a 28.38.48 front chainset, which would give you much higher gearing. and lower the cadence at the above speed to about 75-80rpm*

    obviously the downside is that you will loose the 22t at the lower end.

    *Purely guessing.
  • cooldadcooldad Posts: 32,599
    Pick up and old road bike off Ebay, probably get something decent for less than £50. Not much different to changing drivetrain, and much better on road.
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