Hi All,
Wanting to change out my rear wheel to a Prodigy to match the front Prodigy but dont want to confuse the BCM. Bike is a '14 SGS stock rear is 180x65x16 or 25.35" in dia, new wheel would be 180x55x18 or 25.92" in dia. Total difference is 2.16% in diamater with the newer wheel being slightly taller and less revs per mile. To me the difference is insignificant but having had to make changes in my PV to get my crusie control to work in 6th gear I want to know if I am going to create another headache before I spend the $.

Rather than tell me to google it, get into a oil argument, or inform that a real biker would just do it... I would prefer you post a nude of your side piece if you dont know the answer.

 

Here is a tire comparison with speed errors, if that helps. Assuming those numbers are actual tire sizes and not wheel size.

 

Thanks!
The calcualtor says the difference is 2.4% and the new wheel will be 18 fewer revs per mile. Will the PV let me do a flat reves per mile for all gears modificaiton? (my prior change was just for the 6th gear calculation) or is this so small that the BCM wont notice?

 

I'm not familiar with PowerVision. Someone on here can help, but I think most likely the adjustment is made in quick tune.

 

I'd be worried about the clearance between the top of the fender and the tire. On the SG there isn't that much there now with the lower shocks unlike the Ultras with the 13" shocks. What about getting a 18" tire with the same height as existing? Wouldn't have to worry about anything then.

 

If you are simply changing your tire diameter, it won't affect cruize.. Bike don't know you are going 2% faster. Don't mess with the PV.

 

it's a direct swap. you'll have no worries about hitting wires under the fender, etc. as you're basically going to be running a stock size tire. you won't even really have to mess with speedo correction as you're pretty much going to be in the zone of error for the speedo anyway. just check it with your gps afterward to see how far off you are.

 

I can't help you on the PV question, however I did swap my both my stock front and rear RG wheels (180/65-16 rear) out with a set of 2020 Ultra Limited wheels (180/55-18 rear) about two years ago. I can tell you I haven't noticed any real difference when it comes to speed. The chart via the link RKZen provided seems to be about right, very little difference with speed.

I would say a new tire on the 18" wheel would probably be the same diameter as fully worn-out tire on the 16" since a new tire is about a 1/2" (8/32" tread thickness per side) taller than a worn-out one (2/32") and the chart says that the difference between the two tires is 0.6"

 

got that backwards, the 18'' is .6'' taller than the 16'', so a worn 18 would be similar to a new 16.

 

You can change the transmission output pulses (I think that's what it is called) in the PV to account for the change in tire size and it will correct your speedometer, which in turn I would think would solve any sort of issue you'd run into.

I was able to change the output pulses on my '14 street bob with my PV to correct my speedometer when I changed pulley gearing. Changing tire size has the same effect. But even left unchanged it should have no effect on whether or not you can use cruise control, your speedometer just won't be reading the proper speed.