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Fixed gear - Sprocket change - Gearing Advice

BR 1979BR 1979 Posts: 296
edited February 2013 in The workshop
Afternoon all,

I currently ride a 2012 Langster on a 48t x 15t chainring-sprocket combo (= 84.4" gear). Whilst I am perfectly capable of doing my commute with this gear I can't help but feel it might be a little easier on my knees / more helpful with my cadence and technique to up the sprocket size. Also quite fancy a change and it's cheaper than a new bike!

So, do I go:

1) 48t x 16t (79.1") - Equates to a 6.3% reduction in gearing.
2) 48t x 17t (74.5") - Equates to an 11.73% reduction in gearing.

I am minded to go for the 17t option, but am interested to hear views - Is a near 12% change in gearing too much? Will I find the one or two descents on my route more tricky? (I ride with f/brake, so no great shakes). I quite fancy bit more spin.

My rear wheel is in middle of dropout at 15t - Will I have enough chain for 17t?

(What would you buy, and from where?)

Thanks for any info and views.



  • ride_wheneverride_whenever Posts: 13,279
    I'd advise the 17, purely because you'll have fewer skid patches.

    You'll want about 1/2 and inch for the reduced chain.
  • BR 1979BR 1979 Posts: 296
    Thank you.

    Not being a pedant, want to make sure I understand you correctly - When you say "Need half and inch", do you mean 1/2" of available forwards movement in the horizontal dropouts?

    (Re skids - I've ridden fixed gear bikes for 3yrs+ and not skidded once, I had a 2007 Langster before this. :oops: )
  • The RookieThe Rookie Posts: 27,811
    The gaps between gears on a road bike is typically around the 6.3% on road bikes(middle of cassette) and about 12% on MTB's, do you think you want to drop it 'by one gear' or 'by two gears'?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • BR 1979BR 1979 Posts: 296
    I think I'll go for the down two gears option, but it's a fix/fix hub so could run the two on the same wheel. Just hope I have enough chain to take it.

    Does the brand matter much in terms of quality/longevity/corrosion?
  • BR 1979BR 1979 Posts: 296
    Just to finish up on this:

    Changed from 48/15 to 48/17. No downsides - More spinny, easier climbing and still high enough to spin downhill. Got a 17t cog from Condor reduced from £15 to a tenner.

    Thanks for help.
  • Manc33Manc33 Posts: 2,157
    You either have legs like tree trunks or... I am desperately weak. :oops:

    Or I am missing some real basic fundamental facts. I mean you're on a 20" BMX wheel right? You have 500PSi tyres on, right? :lol:

    No you're probably using a 700c wheel. :o

    48F/15R which you were originally on, means the back wheel span 3.2 times for one full (360 degree) pedal turn.

    To get 3.2 turns I would have to have it on something like the biggest chainring (50T) and the 16T on the back, which is almost the highest gear. That gives a slightly lower gear than you had, 3.125.

    So you mean to tell me you ride around in what amounts to almost the highest gear on a road bike, everywhere you go?

    I am just speechless at this point... I wouldn't even get up a 2% incline in that gear. I would have to be pushing as hard as possible to even get in that gear at all on the flat, it would be like HIIT to me and I would last literally 30 seconds tops before having to stop.

    How on earth are people THAT strong?

    Its not that I don't believe you I just think this is absolutely insane. :P
  • BR 1979BR 1979 Posts: 296
    ^ Nice to have a lady on the forum! ;)
  • I use a 44 - 17 on my single speed which gives me around a 70 inch gear. I find that I have a comfortable spped range from 14 - 22 mph. This means that I can spin along comfortably on the flat, climb many gradients and fight against wind. Used to only use a 72 inch n the past. Would never consider a gear anywhere near the size that you suggest and I consider myself to be reasonably strong. Mind some of the terrain that I ride over would not allow a bigger gear. Only time I have rode on a fixed gear as big as that is on the velodrome.

    I would say the 74 inch option would be the best of the options that you have suggested. Of course I would go a bit smaller.

    Riding single speed for me is about efficiency and enjoying it whilst getting to work quick. 70 inch gear works great for this.
  • im currenctly running 48 x 17 on my 2013 langster though as a single speed

    really love it, great for cruising on flats & awesome for sprinting up short climbs

    the only downside is i spin out on one of my descents hence single over fixed :wink:
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