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I have a 2010 Haro Pro Race, which I bought for commuting and general tomfoolery.

Haro

I commute on it 2 miles a day, and I want to be able to go faster by changing the current single-speed gearing ratio.

It currently has no modifications from the standard gearing:

  • Crankset: 3-pc Alloy 175mm, Euro Sealed Bearing BB
  • Gearing: 39/14

I find that I can go quite fast with this gearing ratio, but when it comes to going down hill it is just too easy and I no longer get any drive.

Can someone suggest a better gear ratio / crankset that is more aimed for top speed, rather than acceleration, yet still allow me to accelerate from a standstill quite quickly?

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3 Answers 3

up vote 6 down vote accepted

what spacing is the is the rear hub? I bought an s2c recently to commute on my track bike, two speed internal geared hub with a gain of 38% but it might be over kill for yourself.

Given your setup you have a gearing of about 55inches, if you were to switch out the rear cog to a 12 tooth you would gain 5inches, bring you to around 60 which is considered a fairly spinny ratio on a track bike.

Easiest way is to switch is the back free wheel. However it seems the lowest freewheel available is 13 tooth so you are limited. You could get a new chainring up front which would achieve the same but may need to buy a new chain too.

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+1 Actually it's difficult to recommend some gear-ratio, besides saying "the larger the better". Unfortunately it's not even THAT easy because if you get too big a gear-ratio, it will raise other difficulties, either (going uphill, for example). –  heltonbiker Apr 30 '13 at 14:49
    
If I were to swap out the chainring, considering it is currently 39t, what size would you recommend? –  StuR Apr 30 '13 at 20:33
2  
Have a play around with this sheldonbrown.com/gears and to be honest your best bet is to work out what gearing is right for yourself. If you have someone with a higher gear ratio try a spin on their bike and see how it fits and work from that –  will May 1 '13 at 9:50

This question isn't as straight forward as you might think. A larger front ring and/or smaller rear cog will get you a larger gear ratio and you'll have higher top speed. However, the larger your gear ratio is, the slower you'll be able to accelerate from a standstill.

Furthermore, the highest gear at which you can accelerate from a standstill is going to depend greatly on your physical fitness.

If you do replace something, you don't necessarily have to replace the whole crankset. You can just replace the chainring with a bigger one. That'll be a lot cheaper. You might also be able to swap out the freewheel, which may be even cheaper.

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Here is an easy gear ratio chart, it will give you a calculation and you can compare it to other sizes that will give you a good gauge to see what you might want to try: bmxultra.com Gear Ratio Chart. I grew up with the 16t rear so my calculations always go relative to that row. Usually BMX racing starts at 45:16, which is really close to what you have at 39:14, and goes up from there. I raced with a 46:16 and never wished for a larger front. This would be about a 40 for you with a 14t rear. If I remember correctly, Fuzzy Hall used a 48:16, and I have seen 53, but that was for a guy on a half pipe to pedal in the flats.

Freestyle gears are set about 44:16, which is just between 38 and 39 on a 14t and then go down, I ride 36:14 on my street bike, and although it pedal more to go the same speed, I go as fast as I need to go, but with the advantage of shorter strokes to get up on rails in tight spots.

The moral of the story is, you will need to learn what you like for different purposes. My son has 9t rear cassette, and if you are willing to spend the money, you might consider going smaller front AND rear. This will reduce the overall weight due to less metal, it will also reduce the chances of busting your sprocket or chain since you will have smaller parts making them harder to hit. You will find more parts are being made for the 9t rear, which is another incentive to go smaller.

Get a 40t front, maybe even try a 41, and since you have a chain-ring rather than a sprocket, you can replace them pretty quick and cheaper. Find what you like and keep your old parts so that if you go too big, you can always go back. You might also want to keep different chains with each sprocket so you dont need to remove or add links. You might even want to swap the gears out on a daily basis depending on what you are riding that day, cross town? use the 41, skatepark? swap out to the 39.

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