Grom gearing/speedometer

Top speed on a stock grom is around 60mph. If yours is stock ? , with that gearing change you might have slowed it down?

 

Just buy the carbon bst’s for it already

 

A grom is fast enough to need a spedo?.....

 

You need tooth counts to even start....
If it was 14/42 that was a 3.00/1 ratio.
Going to a 16/40 would be a 2.50/1 ratio.
Big number divided by small.

You can use your actual ratios to figure rpm or speed change if you have a reference.
60x3/2.5=72 therefore, what used to
Be a indicated 60 would be actually 72 now. If the speedo was correct before.

 

Yeah, not stock. I’m putting almost 26hp to the wheel.

It originally made 24hp, but it couldn’t rev past 7.5-8k with the stock clutch. Livengood put a beefy Barnett clutch in it. Now I can use all the motor.

 

Thanks for that Danny. I knew someone would have a formula for it.

 

Broome,
Go here and put in your changes
https://www.gearingcommander.com/

Then you can graph your speeds

 

I tried it, but I didn’t see a place to adjust the HP. It is based on a stock one.

 

In a Speedo.

because when I read the title I cringed that this may be about Broome riding his Grom in his Michael Phelps replica

 

The hp will effect your time spent in each gear, not your road speed

 

That is assuming you can reach redline in top gear, where some of them can’t because they are HP limited.

 

Stop grinding his gears

 

So adjust the graph to the max rpm you can acheive.....it’s just a fancy spread sheet

 

With 16/34 and enough juice from the motor it will do 78

That could almost get me in the interstate.

But it does not consider rider weight , incline and drag, so the resulting real life speed is lower

 

It would also shorten your life expectancy.

 

$20,000 Grom, and you can't figure out how to mount a real speedometer/GPS?

 

What about displacement? The graph is setup for a 125cc, mine is a 183cc.

 

I have the smaller/low profile bars (I forget the name of them now). They don’t have the extra rail or much room for anything extra.

I already have a map switch mounted on there for VPR and MR12 (I run VPR on the street).

 

Strap your phone on top of a foam block on the tank and run the GPS.

 

I might end up making another gearing change at some point. 1st gear is so short that it is almost useless and it’s still pulling hard in the upper RPMs of 4th gear. I could get away with going up another tooth in front, or dropping a couple more in back.

But then again, I will probably never use it on the interstate.