SS GEARING Question

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SS GEARING Question
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flag big-pete23
Posted: Apr 2, 2015 at 4:37 Quote
im running 36-16 at the moment,

i want more acceleration, which one do i change? 36-14?
flag RunsWithScissors
Posted: Apr 3, 2015 at 6:55 Quote
If you want snappier acceleration you need a lower gear ratio, but you will lose top end speed in the process. If you want to lower the gear ratio you can either use a larger cog in the rear or a smaller chainring/chainwheel in the front.

One thing to keep in mind is that changes to the tooth count in the rear will be more noticeable than changes in the front. One tooth more or less in the rear will be roughly twice as noticeable as one tooth in the front because your gear ratio is already pretty close to 2 to 1.

As for which way is better, cost will determine that more than anything, and which will be cheaper depends on what manufacturer you go with, what retailer, and what type of hub and crankset you have.

FWIW, if you switched from 36-16 to 36-14 you would be getting a higher gear ratio which would give you a higher top speed, but slower acceleration. At a guess, I'd say you want a 17-18 tooth cog in the rear...

Hope that helps...
flag cmc4130
Posted: Apr 6, 2015 at 8:42 Quote
Yep.

This is a "gear inch" chart for 26" wheels. The higher the gear inch number, the more difficult it is to pedal (but you go faster at the top end).

Unsecure image, only https images allowed: http://i1239.photobucket.com/albums/ff509/austinmtbbmxalliance/Gear_Ratio_Chart.jpg
A "normal" singlespeed gear ratio in cross country mtb is a 2:1 ratio, or 2.0 X 26 = 52 gear inches.

In the BMX and dirt jumper world, you want something a little stronger than that. The stock gear ratio is around 55 gear inches. Many riders use up to 60.

A lot of single speed road riders and fixed gear road riders use between 67-73 gear inches.

This is the chart for 700c road wheels:
Unsecure image, only https images allowed: http://www.wabicycles.com/images/gear_chart_700.jpg
flag a-d-e
O+
Posted: Apr 6, 2015 at 8:59 Quote
more acceleration from stationary yes fit bigger at the back or smaller front. i run 32 16 with 26".
if you want greater acceleration at high speeds you might well need smaller rear - only assuming you mean at high speeds because you suggested a smaller rear was required, maybe a geared setup would work better.
flag a-d-e
O+
Posted: Apr 6, 2015 at 9:05 Quote
what i would also suggest is training to improve sprints, some bmx tracks i ride need hell of a sprint from stationary to clear first doubles.
flag big-pete23
Posted: Apr 20, 2015 at 12:27 Quote
a-d-e wrote:
what i would also suggest is training to improve sprints, some bmx tracks i ride need hell of a sprint from stationary to clear first doubles.


this is what i wanna do, i need to build up strength again after a 4 year absence, so gunna drop to 32-16 me thinks Smile
flag cmc4130
Posted: Apr 20, 2015 at 14:35 Quote
mongooseritual wrote:
a-d-e wrote:
what i would also suggest is training to improve sprints, some bmx tracks i ride need hell of a sprint from stationary to clear first doubles.


this is what i wanna do, i need to build up strength again after a 4 year absence, so gunna drop to 32-16 me thinks Smile

32/16 will be spinny. 34/16 X 26 = 55.25 gear inches would be a more normal bmx track gear.
flag a-d-e
O+
Posted: Apr 21, 2015 at 0:48 Quote
cmc4130 wrote:
mongooseritual wrote:
a-d-e wrote:
what i would also suggest is training to improve sprints, some bmx tracks i ride need hell of a sprint from stationary to clear first doubles.


this is what i wanna do, i need to build up strength again after a 4 year absence, so gunna drop to 32-16 me thinks Smile

32/16 will be spinny. 34/16 X 26 = 55.25 gear inches would be a more normal bmx track gear.
agree with this, i ran 32 16 which i would recommend for general trail riding where terrain involves climbing but its fairly spinny on faster terrain, often swapped to 14t out back. most often run 30t chainring on the 12t on bmx track with a geared setup.
flag big-pete23
Posted: Apr 22, 2015 at 2:32 Quote
lads im on 24" , how much of a diff does it make?
flag cmc4130
Posted: Apr 22, 2015 at 8:45 Quote
mongooseritual wrote:
lads im on 24" , how much of a diff does it make?

ya just do the arithmetic:

32 / 16 X 26 = 52 gear inches

32 / 16 X 24 = 48 gear inches

36 / 16 X 26 = 58.5

36 / 16 X 24 = 54 (55 is the "norm"/standard for BMX, so 36/16 on 24"s is pretty normal).

The lower "gear inches" number means that the same gear ratio with smaller wheels is even spinnier..... Get it ? Wink

The reason is that the "effort" required to turn a large wheel is more than for a small wheel.

With a unicycle, you get one wheel circumference distance per 1 crank rotation. If your wheel is bigger, that means you go farther for one crank rotation.

The idea of "gears" on a bike is that when you pedal your cranks in one rotation, you get MORE THAN ONE wheel rotation because your front sprocket has more teeth than the rear cog. (If it was reversed, you would get less than one wheel rotation per crank rotation--which is the case with motorcycles). The question of how many wheel rotations you get is where "gear ratio" concept comes from.

Does that help!? Wink

Unsecure image, only https images allowed: http://www.dube.com/unicycle/images/Splash_Unicycle_Beginner.jpg
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