sprocket sizes

zac_k3
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zac_k3
can anyone give me a little help on picking the right sprocket? it's a 06 rm125 and I was thinking of maybe doing a 52t but thought that maybe it'd be too much, stock is 12-51. most tracks that I ride at are more faster with some tight turns. I can get a great deal on either the 47t or 52t but if it's not going to be good for the local tracks i can pass.
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Paw Paw
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Paw Paw 6/16/2017 7:30am
6/16/2017 7:30am Edited Date/Time 6/16/2017 7:31am
52 would do great, you just have to shift a little bit more per lap.
47 would be too much.
Are you sure the 12 is stock? I thought it was 13.

Paw Paw
NJKawi913
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NJKawi913 6/16/2017 7:50am
6/16/2017 7:50am Edited Date/Time 6/16/2017 7:51am
The best thing you could is get 2-3 differnt options. I know no one likes spending money if your not going to like one option, but you don't know unless you try it for yourself. There are so many factors to gearing from track layouts, to riding ability, to motor work, etc.. The way i look at it for the most parts all tracks have fast sections and tight sections. Pick what you are good at and gear it for the opposite. For example i love high speed rollers and rhythm, no matter what the gearing i do well with it, so i gear my bike to make the tight stuff i hate easier.
c0ncEpT
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c0ncEpT 6/16/2017 11:58am
6/16/2017 11:58am
I have 2 sprockets that I use.

One track in particular I ride is pretty sandy and has way more speed to it. I use the 50T. I'm able to use the wheel speed to get on the pipe and really use all the power with the longer gears.

Another is a tighter, harder packed track and has one particular double right out of a corner that I cannot hit using the 50T. 2nd gear is not enough and the 125 just wont pull my 190lb ass in 3rd. 51T is the key at that track. I can use 2nd instead of 1st in the slower corners and 3rd gear will pull me over all the jumps.

47T would be WAY to tall for any 125 IMO.
Bramlett321
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Bramlett321 6/16/2017 12:28pm
6/16/2017 12:28pm
Paw Paw wrote:
52 would do great, you just have to shift a little bit more per lap. 47 would be too much. Are you sure the 12 is...
52 would do great, you just have to shift a little bit more per lap.
47 would be too much.
Are you sure the 12 is stock? I thought it was 13.

Paw Paw
surely that thing isn't a 12, if so then I certainly wouldn't go up to a 52. Normally every 125, and even my 150 had a 13 on it. 13-52 shouldn't be too big of a stretch unless you're on a long fast track, but if you do any cross country that will help you on the rocks and hill climbs.

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zac_k3
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zac_k3 6/16/2017 1:48pm
6/16/2017 1:48pm
I'm not 100% sure, on motorsport when you select your bike and then look at sprockets it shows your stock gearing, it says for a 06 rm125 stock gearing is 12-51 with a 114 link 520 chain. if a 13t front would work with the 52t rear I'll just go ahead and change it while I'm at it.
Paw Paw
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Paw Paw 6/16/2017 3:07pm
6/16/2017 3:07pm
FYI: When ever you change sprockets try to do so in pairs and the best results result will come also with the use of a new chain as well.
If you elect to go with the 13/52 set up you will be geared for a higher top speed than the 12/50, which I understood was not the direction you wanted to go.
Also understand that the 2 vastly different tracks you are riding may in fact require 2 different gearing set ups to have the best performance at each.

12/51= 4.16:1
13/52=4.00:1

Paw Paw
zac_k3
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zac_k3 6/16/2017 3:31pm
6/16/2017 3:31pm
Paw Paw wrote:
FYI: When ever you change sprockets try to do so in pairs and the best results result will come also with the use of a new...
FYI: When ever you change sprockets try to do so in pairs and the best results result will come also with the use of a new chain as well.
If you elect to go with the 13/52 set up you will be geared for a higher top speed than the 12/50, which I understood was not the direction you wanted to go.
Also understand that the 2 vastly different tracks you are riding may in fact require 2 different gearing set ups to have the best performance at each.

12/51= 4.16:1
13/52=4.00:1

Paw Paw
thanks paw paw! I think I'll do the 13/52.
Paw Paw
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Paw Paw 6/16/2017 3:51pm
6/16/2017 3:51pm
OK, but remember you will have less drive out of the corners as it will be geared for a higher top speed. It will be higher than the original gearing you have now.

Paw Paw
Bramlett321
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Bramlett321 6/17/2017 5:28am
6/17/2017 5:28am
Paw Paw wrote:
FYI: When ever you change sprockets try to do so in pairs and the best results result will come also with the use of a new...
FYI: When ever you change sprockets try to do so in pairs and the best results result will come also with the use of a new chain as well.
If you elect to go with the 13/52 set up you will be geared for a higher top speed than the 12/50, which I understood was not the direction you wanted to go.
Also understand that the 2 vastly different tracks you are riding may in fact require 2 different gearing set ups to have the best performance at each.

12/51= 4.16:1
13/52=4.00:1

Paw Paw
zac_k3 wrote:
thanks paw paw! I think I'll do the 13/52.
Don't laugh at my question but I'd be interested to know how to calculate this? I ride a '16 300 and have been wanting to try different combo's!! Thanks
Paw Paw
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Paw Paw 6/17/2017 5:25pm
6/17/2017 5:25pm
Just take the rear sprocket tooth count and divide by the front sprocket tooth count. This will yield the gear ratio.

The higher the number the "lower" the bike is geared. The lower the number the "higher" the bike is geared.

"lower yields quicker rpms, but slower top speed.
"higher" yields slower acceleration, but a higher top speed.

Paw Paw

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