Why gear down?

[JayO]

I've thought some about this question and need some other input. What is the theory behind how a lower ratio helps/ benefits the performance of an M8.


Along the same lines.... would one increase the ratio of a boosted sled as it is so much more powerful (race gas version, not the wimpy- beat by every 860 pump gas variety) Jay-0

 

[PCDOC]

cooler clutches for one thing. Think of driving a manual transmission car in third gear all of time vs second gear. Mtn sleds will not see 80 mph on the hill so why not gear down to take advantage of more power at lower speeds. My M8 is geared down to 54/66 and pulls great. I would rather have quickness over top end. A stock sled will beat me on the trail for top speed, but I'll pull ahead until they catch me on top end.

 

[ACMtnCat]

Yep... I geared down to 56/64 and I'm seeing cooler clutches and better track speed on steep climbs (45-48mph). And the snap/grunt off the line is sweet! Almost rips the bars out of the hands on a blip! I should have gone lower maybe?

 

[tcpeterson]

What kind of track speeds were you getting prior to the gear change?

 

[ACMtnCat]

What kind of track speeds were you getting prior to the gear change?

I was getting 40-43'ish some times only 37-40mph. Now its feeling more like I'm hovering on the top of the powder when I smash the throttle!

I'm talkin steep and deep powder climbs not racing up a packed hill.

 

[tcpeterson]

Wow, that's quite an increase! I was also curious because of the clutches running cooler since i've been have clutch heat issues. Thanks for the info!

 

[1Mike900]

With the diamond drive I would gear down, You will get more torque to the track since it robs BHP within itself.

Mike

 

[ACMtnCat]

Wow, that's quite an increase! I was also curious because of the clutches running cooler since i've been have clutch heat issues. Thanks for the info!

I have also add clutch weight and switched to a green snopro inthe driven. So not all that was gained by just gearing down.

 

[tcpeterson]

Ok, well i went with a 44/40 helix and 75g weights. It really seemed to help the clutch engage faster. If i gear it down i'm hoping to gain some more.

 

[ACMtnCat]

I found the shallower helix's work better for steep and deep. I tried that 44/40 and found it to loose rpms in powder climbs. I'm really liking the 44/36. Good snap off of idle and hold a constant 8050rpm.

 

[SLED2SHRED]

Yeah it sounds that gearing down will do it for my M8. I have SLP pipe, BDX air with 40/36 and it seems a stronger bottom than stock yet seems hard on the belt. Which way should I go? I would like to get by with only 1 more trip to the shop to dial this in..

 

[Killerk]

The way I understand it is there are 2 advantages.
1-you have a mechanical advantage by gearing down (less effort for the clutches to initially get the track moving).
2-the clutches run in a more efficient part of the sheeves at lower speeds compared to higher gearing.

 

[KMMAC]

Set a new stock sled up on a stand with the track off the ground, warm it up good and watch the speedo, it will more than likely hit about 120 mph,,, if you can stand to hold it wide open that long. Now ad in the fact that when you go up in elevation you lose horse power. Now the clutches have to work harder, shifting against the stock gear ratio. So unless you have a gozilion horse power and alot of clutch weight the clutches get over worked and too hot, which then translates the heat to the belt and the belt being the weak point, bang goes the belt. Don't know much about the other brands but cat seems to think that high gears are the way to go, or, that every one has gobs of money to spend on belts. Bottom line is gearing for the mountains on a stock or semi modified sled meaning after market pipe, stuff like that, the sled should have no more track speed than about 70to80 mph. some will argue but like I said earlier,, unless you have a gozilion horse power, gear down.

 

[JayO]

KMMAC.... I appreciate you opinion.
would you gear down a race gas M8? It comes stock with 57/63. Estimate 200 hp at 7K...??? Jay-0

 

[KMMAC]

Like I said,, if you have a gozilion HP you probably don't need to gear down so much. Since I've been out of sledding before the change to the gear drive don't know for sure on how much to gear down this new stuff. ONE thing is for sure,,,, if you are still burning belts with that much HP and all is well with your clutch alignments and setup then ya, I would say that you might need to gear down some. I take it you are saying you have a race gas turbo? Also, do like I suggested at the beginning of my post just for kicks put that baby up on a stand warm the engine and watch the speedo it's amazing what kind of speed you will see. If it climbs over 100 I would be concerned that your not getting the most out of your clutches. Where I noticed the gear down the most is boondocking in deep snow and tight woods or through the trees up hill alot with a bunch of stop start stuff. That being said, even out in the wide open in heavy snow or deep pow up long pulls under a heavy load this to will cause clutching problems, you know, wide open belt blowing type problems. Some of this stuff doesn't change too much would love to get on a newer sled just to see how much different this new chassis handles. Problem is it's been 10 years to the month since I was injured riding and was never able to get the damage fixed (hip). I could ride but it would be embarrassing plus the fact that I'm so out of shape now not hugely over weight just short of breath that I would probably hurl before I made it to the meadows, Baker. Still love this sport though and it looks like with some sort of miracle I might be getting my hip fixed this year, so looking to get back in the game IMO this IS the best recreation period. Bring on a moderate ice age!!!