Honestly, I think this is one of the best mods. I think doo's come way over geared. -1 on top or +2 on the bottom is pretty close to the same change. Just watch your dog leg, and you'll be alright

Sent from my Pixel 5 using Tapatalk

 

I’m thinking about running the sled stock for part of the year to see what it’s like, then change them.


Sent from my iPhone using Tapatalk

 

Exactly.

No point in changing things if you don't have an established base line.

 

Yes, I’m just trying to plan ahead.


Sent from my iPhone using Tapatalk

 

When you gear down by either removing one tooth from the top gear or using a bottom gear with more teeth, you are removing some of the load that the engine and cvt system senses because of that gained mechanical advantage

After gearing down you "mite" end up at let's say 8100 rpm @ WOT rather then the ideal 7900 rpm @ WOT. These cvt systems are very sensitive to changes so you may need to do a few small changes to allow the cvt to upshift a bit faster as to "load" the engine back to it's ideal powerband .

Just sharing some of the basics of how gearing changes can effect things. Hope this helps.

 

Not sure what the 850 comes with for gearing but I've geared down two teeth on top from a 25 to a 23 on my last four 800s. Probably at least 25,000 miles with no issues. Awesome acceleration, awesome belt life, yes it's hard to reach over 100 but you get there really fast. And yes I've had to add pin weight one or two grams to the clutch for optimal RPMs. Never considered it was because of my gearing change but I guess that makes sense.

 

The 850 renegades come with 25 - 45 sprockets.

I m sure gearing down the old 800r renegades would have help alot. I always felt they were lazy on the bottom end in stock form.

Stock to stock against my buddy's 800R renegade, my current 850 renegade hits sooo much harder down low.

I ll ride my sled stock this season but maybe next year I ll experiment with some gear changes and clutching as well.

 

Here is good link on gearing. It brings you to an example of dropping from a 23 to a 21 for off-trail, but you can use it for dropping from a 25 to a 23. Then scroll to the top and read the whole page.

Gearing - I have a 23, considering a 21 top gear

It does have the answers to your questions, including the effects of gearing on the clutching which is explained halfway down with two pictures to depict the center of gravity position change of the arms (ramps for the pDrive).

 

I would stick with stock gearing on your 850 if you mainly trail ride. Some guys even go to a 26 top gear if they are running a 1.25" lug track or smaller. A clutch kit will do much more for you. Check out hot rod sled shop. There are alot of threads that speak to clutching on here.

 

A good clutch kit and 192 studs that stick up a 1/2 inch above the lugs will do 100x more than changing your gearing.

 

I've got Reeds and HRSS clutch kits and I wasn't planning on gearing down, thing spins to much as it is.

 

Use a 26/45 on my 18 Renegade X with a 1 3/4 Hurricane track, works perfect for me.
Didn't need to change the chain either.

 

Yup, changing my 25/45 on my ‘21 MXZ XRS to a 26/45 also for this year. Lots of folks on here say the 26 works great. Can’t wait to try it out with my 1.25 Ripsaw stock track.

 

The 850s certainly makes enough raw torque to pull the 26 tooth top sproket .

My 850 with factory 25 -45 gears completly rips threw what my poor 137 ripsaw with 96 studs could provide for traction.....

This year I ll be running a Storm 150 track

 

26T top gear gives you a higher top speed than a 25T, assuming you have enough power to pull it. People usually gear the other way though when the increase the track lug size. I would try the 25T first if you already have it.

 

The 850 has plenty of power to pull it. Its just that sometimes someone will get say 103mph with a 25t and 99mph with a 26t, what happened?
Whatever helix and spring combination in the secondary clutch is not tight enough to pull that higher load from the gear. The vehicle is getting the speed its getting by virtue of excessive belt slip.

 

As above... a taller lug usually adds drag to the system and loads the engine more and reduces top end RPM and speed. Going to a higher number of sprocket teeth up top loads the engine even more, and you can end up going even slower.

Going to fewer teeth up top would be the typical way to try to rectify that change... or clutching changes that would tend to increase RPM's.

 

Add 1 tooth to the bottom, if at all on a Rene. Most people find the Rene can handle MORE gear.

 

Add 1 tooth to the bottom, if at all on a Rene. Most people find the Rene can handle MORE gear.

IF "more" means larger number, THEN, If you have a 45 bottom and go to a 46 bottom, then in theory [gear calculator] the top speed is slower.

 

^^^ All depends on what one means when saying a sled can 'handle more gear' LOL.

 

More meaning some people run 26 or 27 on top. Theoretically yes, you lose top end with going bigger on the bottom.

 

I ran a 26 top in my Renegade. Now, I have my personal philosophies on gearing. But I can confirm the 26 works very well in a stock sled with clutching. 108 gps top speed on crappy snow. Would’ve tried a 27 top in it if I would’ve kept the sled- I think it had the legs to pull it. But either way, 26 works. 25 is geared too low for trail riding in my personal opinion.

 

^^^ Interesting issue. Makes sense with the increased drag (torque) to the secondary due to the larger top gear. Thanks for the insight on a 'real-world' issue.

 

Application is important. Different sled, different engine, and clutches but similar power and tracks. 24 Polaris 850 XCR 136 1.352 Cobra comes with a gear ratio of I believe 1.68 from the factory, and I went up one tooth on the bottom gear for a 1.73 gear ratio. If the Renegades with 1.25 ripsaws are coming stock with a 1.80 gear ratio with 25 45 gears they have a good bit more gear reduction (not accounting for clutch differences) than the Polaris sleds come with at a 1.68 ratio with that lug height. Going 25 46 which would be adding one tooth on the bottom gear gives a 1.84 ratio. Both of the 850 engines have good torque and gearing down for the short lugs and prestuds or shorter trail studs at 2-3 per bar for trail riding after a point will reach limits of the available traction and then sled spins more instead of accelerating harder. Deep snow, higher elevations, and deep lug tracks can utilize more gear reduction. Sled might actually be easier to keep traction coming out of corners or taking off from a stop with less torque multiplication from a taller gear ratio like 1.73 which you could get with a 26 45 sprocket set. I think the stock gearing for on trail use low elevations with a 1.25 ripsaw or 1.25 ice ripper or even a well trail studded 1.25 ripsaw is pretty good and I don't think any big changes would be helpful. I would focus my efforts on making sure your clutching is dialed in.
However I also have a low power/torque 600efi with a 1.25 ripsaw and 90 short trail studs that I figure will benefit a good bit from some extra torque multiplication and not overpower the track to spin city lol so I am looking to go with a 2.09 gear ratio on it.

 

Also with the 600 efi at 85-90 hp turning a 1.25 lug height on a long travel suspension rider forward chassis I have no worries about top speed loses from running out of gearing it doesn't have the power with the stock 1.96 gearing to pull clutches to full overdrive or even 1/2 overdrive.
So top speed can be another factor with gearing changes but it again depends on the application my XCR the polaris clutches do not have as much overdrive as the ski doo clutches and if I was to run the same 1.80 ratio as the renegade I could potentially lose some top speed in ideal conditions compared to my 1.73 ratio. I also felt I will be doing good to get the hp I have now hooked up with my track and trail stud setup on that 850. Gearing down further would likely cause additional trackspin so for those reasons on that sled I went with the 1.73 ratio and didn't gear down further. But the 600 efi with nearly 50% less power I want a way different ratio on it a 1.73 would be terrible.....