How do 20” tires affect speed?

[localbar]

I have the standard 18” tires on my RXV and I want to go to 20” tires (14” rim)
My cart goes 17mph now, what can I expect when I go to 20”?

[kernal]

Under optimum conditions with standard 18" tires: electronic key unlocks 17.5 mph and hand held scanner unlocks additional 2 mph. Dealer with appropriate equipment can do this for a fee. After that 20" tall tires effectively result in a taller final drive ratio (lower numerically) resulting in 22-24 mph. This robs a little torque but I didn't notice it on mine.

If you have access to tuning (Curtis controllers only) by Bob Boyce, 32 mph is possible as is fine tuning of acceleration and regen braking along with the recovery of torque lost by using the electronic key/scanner.

If you don't have access to dealer or Bob, the tires will get you to 20ish likely.

[ojo]

The 20.5 tyres gives me 3.5mph more, with 20" you can expect around 3mph...

[JohnnieB]

RXV has 16.99:1 gears, so at 17 MPH on 18" tall tires, the motor is spinning at 5394RPM.
With 20" tall tires, the cart's speed ought to be 18.9 MPH. The actual speed gain will likely be slightly less since the is a 10% torque loss associated with the 11.1% speed gain.

[kernal]

JB, my experience with the RXV is that they are significantly dialed back by the VCL, software or firmware (pick appropriate term). My RXV doesn't drive anything like my TXT (series but 48v, Alltrax etc).
When I first acquired the cart the dealer had forgot to unlock the controller. After he did it I found no decrease in accel or speed attainable on inclines whether by seat of the pants or measured by GPS. After it was tuned by Bob Boyce it reaches 32mph with out much effort (20"tires). This is not a case of needing a long run out to to get there and the cart is especially snappy in the 25mph range. On my test hill the cart held 22mph as originally programed, 22mph after "freedom mode" was unlocked and still holds the same 22mph on the same hill after the specialized tuning, even with the 8v batteries at end of life and voltage dropping below 40 under load.

[localbar]

Originally Posted by JohnnieB

RXV has 16.99:1 gears, so at 17 MPH on 18" tall tires, the motor is spinning at 5394RPM.
With 20" tall tires, the cart's speed ought to be 18.9 MPH. The actual speed gain will likely be slightly less since the is a 10% torque loss associated with the 11.1% speed gain.

Thanks. I was hoping it wasn’t going to put me over 20 MPH. This cart is for my kids and in a private residential community.

[kernal]

Dealer might be able to dial it back. Never had anyone ask about that as I recall.

[JohnnieB]

Originally Posted by kernal

JB, my experience with the RXV is that they are significantly dialed back by the VCL, software or firmware (pick appropriate term). My RXV doesn't drive anything like my TXT (series but 48v, Alltrax etc).
When I first acquired the cart the dealer had forgot to unlock the controller. After he did it I found no decrease in accel or speed attainable on inclines whether by seat of the pants or measured by GPS. After it was tuned by Bob Boyce it reaches 32mph with out much effort. This is not a case of needing a long run out to to get there and the cart is especially snappy in the 25mph range. On my test hill the cart held 22mph as originally programed, 22mph after "freedom mode" was unlocked and still holds the same 22mph on the same hill after the specialized tuning, even with the 8v batteries at end of life and voltage dropping below 40 under load.

I keep forgetting the laws of physics don't apply quite the same when RPM limiting is involved.

More correctly, they actually apply the same, it is just that there are other factors involved that mask their effect.