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Discussion Starter · #3 ·
I went straight to a 13 tooth and its great doesn't bog down any more. But I'm also 6'5" 280 so every lil bit helps lol
haha yea, thats a lot of weight to move, im about 190...the 13 tooth drops the top speed to about 65-66, 14 tooth is around 70 which im hoping is about where it can reach with an exhaust and the 14 tooth

I bet that 13 rips around town
 

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I went straight to a 13 tooth and its great doesn't bog down any more. But I'm also 6'5" 280 so every lil bit helps lol
Hey hey another big guy. What speeds have you been hitting with that 13 tooth, I have been thinking about swapping mine out.
 

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Discussion Starter · #6 ·
So stock is 15? How can you reach 65-66 with a 13, but I can only get 62 in stock form?
Lol...you have to understand the difference between theoretical top speed and actual top speed.

These bikes dont have enough power to reach the theoretical top speed, as in the top speed that is actual possible at 9200 RPM with a 15 tooth gear.

The calculated top speeds with a 15 tooth is about 74, 14 tooth, 70, 13 tooth, 66.

When you put a 13 or 14 tooth gear on the bike you are multilpying the engines torque a little more and getting it in the power band better so you may be able to reach a higher ACTUAL speed even though the THEORETICAL top speed is lower.


Going down the exact same hill today I was able to hit 69 mph with the 14 tooth and I could only hit 65 with the stock 15 tooth.

It's all relative, if you add enough power to where the bike can hit 70+ no problem you may go to a 16 tooth up front.
 

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Lol...you have to understand the difference between theoretical top speed and actual top speed.

These bikes dont have enough power to reach the theoretical top speed, as in the top speed that is actual possible at 9200 RPM with a 15 tooth gear.

The calculated top speeds with a 15 tooth is about 74, 14 tooth, 70, 13 tooth, 66.

When you put a 13 or 14 tooth gear on the bike you are multilpying the engines torque a little more and getting it in the power band better so you may be able to reach a higher ACTUAL speed even though the THEORETICAL top speed is lower.


Going down the exact same hill today I was able to hit 69 mph with the 14 tooth and I could only hit 65 with the stock 15 tooth.

It's all relative, if you add enough power to where the bike can hit 70+ no problem you may go to a 16 tooth up front.
Yeah I know all that, but I didn't know the Grom would actually make that actual top speed. Really doesn't seem to have any power above 8k, or maybe I'm just crazy.
 

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Discussion Starter · #9 ·
Yeah I know all that, but I didn't know the Grom would actually make that actual top speed. Really doesn't seem to have any power above 8k, or maybe I'm just crazy.

Yea, I hear ya. The motor really doesnt have any power up top but with a 15 I know the RPM's are pretty low in 4th gear, like 7k or so around 60 so the 14 puts you up around 8k and into the powerpand better I guess.

Either way, It seems like the bike will cruise a few mph faster on the highway with a 14 tooth.

Im gonna order a 13 tooth to test it out as well.

I may end up staying with the 13 tooth if it can hold 63-64 mph.
 

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Going down the exact same hill today I was able to hit 69 mph with the 14 tooth and I could only hit 65 with the stock 15 tooth.

It's all relative, if you add enough power to where the bike can hit 70+ no problem you may go to a 16 tooth up front.
keep in mind pretty much all bikes have built in 10% speedometer error, so that 69 is actually more like 62
 

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What sprocket are you guys using? Havent seen any companies come out with replacements yet. Are there other bikes that they fit?
 

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justin
Lol...you have to understand the difference between theoretical top speed and actual top speed.
 
Going down the exact same hill today I was able to hit 69 mph with the 14 tooth and I could only hit 65 with the stock 15 tooth.

 
 
I hope you are not going by the number on the groms speedo.
 

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Plenty of chain adjustment for the 13T and 14T up front?
 

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Yeah I was using my speedo and my buddies to compare but I used my GPS today and noticed I was 5-7 mph off. So I will do some more testing and see how fast it will actually go. Sorry about that. For some reason I was thinking it was reading off the front wheel. Derrrr lol
 

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Discussion Starter · #19 ·
keep in mind pretty much all bikes have built in 10% speedometer error, so that 69 is actually more like 62
It seemed right on accurate when I used the GPS on my phone with the 15teeth.

I think the grom speedo reads pretty true.

The 69 was after I compensated for the gear change, it read 72 mph which was about 69 after compensation for the gear.
 
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