stock DS 650 runs about 72-74 mph stock right? And that is hitting the rev limiter in 5th gear. They come stock with 20x11x9 back tires. How much mph would be gained by going to a 22x11x9 tire?

 

Take the old tire size, and the new tire size, divide the larger into the smaller, this is the % of increase or decrease.

in this case +9%

Use a calculator and add the pencetage to your top speed. (if the new tire size was the smaller one you would subtract)

79.57mph is what I get, 6.57 more mph.


This may not be 100% correct and there are a few ways to do it but, I think this is easiest

 

if your curious, i have a gearing calculator on my site that takes in account, tire, sprocket combinations. the calculator does not take into account wind resistance. glamis dunes

 

Top speed is almost irrelevant unless you compare it on the same surface. My LT250R with the 22" rear tires hit 78 MPH with a 1 tooth shorter front sprocket. This was on the dry lakebed at El Mirage, CA. On anything remotely loose, you will loose a lot of speed, I think I was hitting like 65 or something on a sandy/loose dirt road at Hungry Valley, CA. (The road isn't there anymore, it's paved.) I'm curious as to what surface that top speed is rated on. I never hear the rags say that they took the machine to any dry lakebed for tests.