Speedo Error Mystery
New to the forum. Yes I tried looking this one up. Couldn't find this exact situation.
Bought a used 2007 zx10r late in the fall. Guy said the sprockets were different so the speedo and odometer would be off. On the ride home on the highway I noticed I was at about 85-90 right next to my wife driving a car. Knowing she does't drive THAT fast, I asked what she was doing. About 75-80. So I figured I was off a bit due to sprockets. Did research and decided speedoDRD would be a good choice, and Santa brought me a one for Christmas. I just now got around to installing it and while doing so I took off the cover for the front sprocket for the first time. Had 17t stamped on it. The rear has 40 stamped. Hmmm...I thought that is stock yes? Tire out back still has plenty of life on it and is a 190/50/17 which I believe is also stock.
I went ahead and installed the DRD since I already had it and figured something is wrong anyway. Went with -8% to try to get it close, but will try to get more accurate using phone GPS while riding seeing as I can't really use a sprocket calculation since they are stock.
Any ideas as to why the error in the first place? And if it due to a faulty speedo or sensor, then do you think the DRD will properly fix it?