By Jon Crowley
Putting bigger tires on your UTV is one of the first changes from stock that many of us make. Being a rock crawler I really like how larger tires give you more ground clearance, but that comes at a cost. For example a Polaris RZR XP Turbo comes stock with 29-inch tires. I like to bump that up to 32-inch and that larger tire changes the final gear ratio. This can cause CVT belts to slip and break. And you also lose some of the low-end performance with taller tires.
From back when I had a Jeep, the solution was to change out the ring and pinion in the differentials, but to do this in a UTV would be cost prohibitive. There are several “gear stack” type in transmission options available for Polaris RZR models, but the side effect to these types of setups is an increase in thrust load case fractures.
Optimum Offroad has teamed up with Mendeola Transaxle to create a different type of solution that moves the gear reduction as close as possible to the wheels at the pinion shaft. Optimum Offroad currently offers a 10% reduction and this is what I decided to try on my 2017 Polaris RZR XP Turbo.
Harts UTV in Sacramento, CA did the installation of the Optimum Offroad 10 gear set for me. The installation isn’t that difficult, but it is time consuming especially with an aftermarket cage and a turbo model since the transmission has to come out.
I picked up my RZR and the first thing I noticed was a bit more gear noise than stock. This is primarily due to the straight cut gears, but isn’t an issue and I’d gladly take a little more noise for stronger gears. We loaded up the RZR in early June and headed to the Rubicon Trail.
I run 320x10R15 ITP Ultracross tires on my RZR and I could notice only a slight difference in the rocks versus stock. But slow speed rock crawling with a 10% gear reduction isn’t going to be that noticeable. I crawled all day without issue.
Next up, I headed to the dunes up in Oregon for the UTV Takeover. I have 30-inch GMZ Sand Stripper XL’s on the car and while the power from the 2017 turbo is great, I don’t feel the gearing is setup well for my taste. I don’t feel the need to do 80mph in the dunes, and prefer more power down low for better throttle response. The Optimum Offroad 10 did just that for me. Just enough to give me better acceleration, but not so much that it took away my high speed. Very favorable change in my opinion.
Overall, I am pleased so far with the performance of the Optimum Offroad 10 gear set and can’t wait to get it out in the desert for some high speed runs with 32-inch tires.
The only downsides to this gear reduction is cost (retails for $699) and a little bit of extra gear noise. The gear set is made in the USA so I can understand the extra cost for higher quality. The other advantage to this setup is if you already use an in-transmission reduction kit (like Turner or SuperATV) or you have a HighLifter or Gold Metallic special edition with lower gearing from Polaris, the Optimum Offroad 10 will give you an additional 10% on top of what you already have.
For more information, visit www.optimumoffroad.com.