Rolling radius?

[serenitycamper]

Hey guys, I really need an answer on this.

My rolling radius is -29mm (-4.43%). What effect is this going to have on a) my gearing and b) my speedo reading.

Thanks guys

[California Dreamin]

Speed 4.43% lower at the same RPM.....so 3500rpm at 65mph would now be 62.12mph or 3655rpm at 65mph APPROX.

Your speedo will also read 4.43% higher which considering most read around 8 - 10% over will now read 12.43 - 14.43% over.....so speedo reading 67 -68 would infact be 60mph.....all approx.

Martin

[serenitycamper]

Thanks for the answer! Hmm that's going to cause problems as I already don't know what revs I'm doing. I need a rev counter.

[billy739]

google gear speed calculator,
type in the info and it will tell you what your revs are at a certain speed.

you need to know your gearbox code - on the gearbox or sticker and your tyre size.