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Hi Just wanted to ask how to make my bike faster.

Do I change the front chainring to a larger one, if so do I have to get a whole new drive train or can I just get another shimano large ring. Can I get a smaller cog at the back, will that make my bike faster?

Please take a look at my bike. here are the specs

Shifters: R660 Shimano trigger, Front derailleur: R453 Shimano, Rear derailleur: Shimano Sora, Cassette: FAC MICHE 9s 12X26 Bottom bracket: FC453 Shimano 50/39/30, Chain: KMC Z9000

here's the site with more information http://www.btwin.com/en/fitness-road-bikes/3856-b-twin-forme-5.html

I just want to know if I can change anything to make it faster but I don't know what to change. thanks

Thanks

David

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closed as not constructive by Neil Fein, freiheit Mar 4 '13 at 4:10

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.If this question can be reworded to fit the rules in the help center, please edit the question.

1  
Why is it slow? At top speed in high gear, how many RPMs are you turning? Do you have enough gear ratio options on the high end to pick a "sweet spot"? –  Daniel R Hicks Mar 3 '13 at 13:22
    
I don't know how many RPMs I get but I find myself feeling like I could go up a gear, the bike stays on the large ring and even cycling as fast as I can down hill I only reach about 45 - 50km per hour. –  david Mar 3 '13 at 13:52
    
Your bike is a hybrid which is more intended for versatility than speed. Try out a dedicated racer or TT bike which will have a more aggressive posture...that alone will make a noticeable difference. –  WTHarper Mar 3 '13 at 17:18
    
Replace the legs which drive the pedals. –  Kaz Mar 4 '13 at 21:46

2 Answers 2

There's a nice gear calculator at Sheldon's site. I did a quick calculation for you, and at 50/12, at 90 RPM, you should be going 47.4 km/h. If you upgraded your front chainring to a 54, and your back cassette to go down to 11, at the same RPM you could go 55.8 km/h, which is a significant increase. You can play around with different options on the calculator to see how much it would help to get different gearing combinations.

You might find that you won't get much extra speed out of bigger gears as your bike has a somewhat upright posture and therefore you'll be quite limited in what kind of speed you can get. I think that 50 km/h is plenty fast for a bike and that you should just focus more on going faster on the flats and uphills.

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Thank you for all the answers, I will probably change my bike for a racer. –  david Mar 5 '13 at 7:35

By far the easiest option is change the cassette to an 26*11. Reducing the smallest cog from 12 to 11 will give you about 9% more speed for the same cadence. To get the same out the front, you would need to go to a 54 large chain ring. An other option would be to go to a 52/12 - quite a common size.

You failed to mention what wheel size you are running - this has a big impact on gearing.....

As Danial asked though - 50/11 is an insanely large top gear (assuming 700C wheels), very few people could push that for any length of time. It is unlikely your speed problem is gearing with a 50/12 - is you cadence high enough?

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