Will going to a 190/55 rear help bring my speedo a little closer to reality?

[RossKean]

I know the Zumo (and other) GPS gather altitude data (my Zumo 665 does as well as my 765T) but I don't know whether they use elevation differences in speed or distance computation. Even in the extreme example I used, the error amounts to only 0.5% (10 miles @ 10% slope).

 

[mikeames]

The newer GPS's are much more accurate than the older ones. In my opinion to the point of splitting hairs as far as speedo accuracy is concerned (in most paved road conditions). If you travel a road in a very deep and narrow canyon or with extraordinarily heavy tree cover you may experience some issues under those conditions. Other than that any modern GPS is going to be pretty damn accurate.

For my next question I'd like to ask "Is it ok to use automotive oil and oil filters in my motorcycle....?"

 

[El Toro Joe]

I still can't believe how long it took this to end up here

 

[Klubis]

I find speedometer error varies with the viscosity of the chain lube I use on my FJR. WD40 seems to get the best results. This assumes you change the air in your tires with every automotive oil and filter change.

 

[Klubis]

On a more serious note, when we're carving some twisties and all leaned over like the Tower of Pisa, we're riding on the side of the tire, right? The side has a smaller circumference than the center of the tyre (spelled with a "y" for the Brits among us). So while we have a knee dragging, if we were gonzo enough to look at the speedo, would it not show an artificially high speed? And if we never went straight, then wouldn't the odometer record artificially high miles? Think of all the pre manure valve checks that have been done. Hey, have any of yinz seen my meds? I gotta go now. I think those peeps in the white coats are coming! Happy Thanksgiving, all!

 

[HyperPete]

I did not see this posted in the thread, so here is a link to a tire size calculator for speedometer error:

https://tiresize.com/speedometer-calibration/

 

[RJAMT]

My Gen3 reads 1mph more than my Garmin up to about 45 where it starts reading 2mph more. I've only run up to about 120 but it was still reading 2 above GPS.

Where I live there is definitely no issue with misreads due to curves or elevation changes.