Speedo way off after F2 rim mod

[drinmotoracer]

Hey,
So I put a F2 front rim on my bike a few weeks back, and I noticed that my speedo is kind of off... like way off. I packed the speedo gear box full of grease as stated by the manual. I used a multi-purpose auto grease though, and I'm wondering if that has any affect. At speeds of 70+ mph I really notice a lot of cars going past me on the freeway... for example, I go 85 mph according to the speedo, but I had my gf follow me in my car which has a digital speedo she says I was really going 70mph. Anyone else experience something similar to this?

[hpwcycleservice]

maybe the tire profile is smaller making it spin more times to travel the same distance? whats the tire say on it?

[nomoduc]

That's exactly what it is, the lower profile of the tire compared to the stock size. I have the same problem. Maybe it's the bumpy I-880,haha.

[bk94si]

I went to a lower profile tire (stock rim). It used to read about 5 mph fast, now it's about 10 mph.