Speedometer issue

Hi all, I am new to GEM’s and hope to gain some knowledge from those of you with more experience. I’ve recently purchased a 2009 GEM e4. It seems to be in decent shape. The front A arm bushings were worn out and one of the tires was leaning bad, so I replaced them. Other than that and the speedometer not being correct, everything seems to operate as it should.

One of the first thing I did was to check the speedometer against a gps speedometer. The GEMs speedometer shows 26-27 mph and the gps shows 21 mph. It has new 165/70-12 tires that were on it when I bought it. They measure about 20.5” tall. I’m assuming that the speed is limited by what the speedometer reads? Or is it programmed to only let the motor turn a certain rpm?

I’d like to go with bigger tires to gain a few mph, but before doing that, I’d like to get it up the the 25 mph that it is supposed to do. I’ve searched and can’t find any information as to why the speedometer would be off. Any help or information would be appreciated. If it makes a difference, it has the 7hp option from the factory.

Thanks in advance,


My magic magnet will calibrate that for you.

From looking at your other posts, that would allow me to change the speed limiter and calibrate the speedometer? Looks like the magic magnet review thread will probably answer a lot of my questions. But while I have you, if you keep the settings reasonable, this doesn’t reduce the life of the motor drastically?

Only in so much that you will be running 25mph rather than 21mph.
You can adjust it to lower speedometer reading in ~2mph steps.

Ok, thank you. That’s probably the route I’ll go

Fyi your Gem will be some what top speed limited. 2009 had the hill climbing gear ratio in it. accelerates and climbs hills well. But it limits it’s top speed. Most 2009 Gems came with 14" wheels, yours with 12 wheels and the 12…44 gear box will really limit top speed. If you want to start going 30+ mph taller tires would be recommended

Thank you both for the info. I would like to be able to go 30 or so, but I also don’t want to sacrifice a lot of range. I’ll probably try some taller tires and the magic magnet to correct the speedometer. I’m guessing with the lower gear, a taller tire might actually increase the range a little?

Reality Check: The faster you go the shorter the range.


Got the tires mounted and on this afternoon. They are 25x8-12. Also received the Magic Magnet. Super easy install, and clean unit. I left the switches set as they were shipped to see how close it was. GPS showed 28-29mph and the GEM speedometer showed 31. That’s close enough for me, but I’ll probably look back at the other threads to see if I can get it to read exact. The biggest thing I was trying to overcome is the way it was cutting out at 21 because the speedometer was reading wrong. Thank y’all for the help.