bigger = slower

 

Anyone else have any input on this?

 

120/70-12 front
130/70-12 rear..

will make the speedo off, uhm may lower rpms at higher speeds? may wear out bushings faster if lots heavier. Idk

 

Different tire manufactures will have slightly different real world measurements even given the same markings on the tire sidewall. With this being said the Michelin power pure 140 is very very close in outside diameter to the
OEM 120/70-12. My odometer actually gained accuracy slightly when I switched to the 140 Michelin (when comparing to GPS readings). Knowing now the size difference I might have considered running the Michelin 130 on the front.

Shawn

 

I like to run Michelin 130 but they are only made for the rear.

Has anyone used Michelin 130 rear tire as a front tire?

 

I run Metzeler 130s front and rear

 

Oh the groms I hve raced everyone seems to be running the following sizes:
Front: 100/90-12
Rear: 120/80-12

but that is just the common sizes of race rubber available for everything from mini sumos, GP chassis minis, to Grom / z125 type machines. This doesn’t mean mean the tires work as well as they should. Grip has a lot to do with the rubber and wether you have the right compound for the temps your aggression level is able to put into the tire. (Super soft, soft, medium, etc).

But the optimum sizing has to do with the bike, how you ride, the wheel width etc. On my stock grom I don’t overwhelm the grip with its modest brake/power. But I am curious what sizes closer to stock may make on handling. The width of the grom wheels is wider than every other Mini I have (except for my Benelli 135). I want to try PMT slicks in a size closer to stock and see have the handling behavior change. Maybe this will be a better match with the wheel width.

front: 120/80-12. (Because that is what is available, note it is listed as a rear tire though)
rear: 130/75-12

i live in Texas so our high temps leave me wanting medium as I tend to kill softer tire in the summer. As a result I have to run pressures on the high side to keep tire temp in check. With that said the hardest compound for the rear is a soft. Ultimately that may affect my ultimate choice as to what works best. But maybe not a problem. My motor isn’t a torque monster.

for another perspective, my Benelli uses stock sizes that are large like the Grom. The track rubber I run currently fells like I am going to crash all the time. It very much wants to fall into corners. And it never feels planted. No way do the tires get to the edge. Which may be a profile issue. Time to find out.

 

I was recently told by a professional motorcycle racer that the front tire should be shorter: 100/70/-12, not taller 100/90-12. I just got my Grom back from having new 100/90 tires placed on the front and I noticed that my bike is slower to go from one side to the other. I can't throw the bike back and forth through tight turns as quickly. Maybe the shorter 100/70 tire would help with this issue?