Gearing down

[cey800]

I know this is a on going discussion on many other sites, but here we go. How many of you gear down your sleds? If so, to what extent? Gearing is a personal preference, but what is more important? Run up to a hill, or track speed? Just looking for a little discussion.

 

[HagmanMod1]

the only way i'd gear down is if you were lengthening the track. my opinion is if you gear it down to much you make your sled slower and track speed is the key to the big marks on the hill

 

[HagmanMod1]

when i built my sled it went from a 159 to a 162 2.5 extreme track and i obviously lost track speed making this change, but with bthe extra traction i gained it climbs way higher now than it used to. i thought about gearing mine down when i made this change but got talked out of it and it seems to work really well. in some cases i've heard of gearing on a stocker inproving it alot so i dont know its a tough call, like you said more off the bottom or more track speed

 

[cey800]

Talking about track speed, what do we like to be at?
85,75,70 mph?

 

[dooski]

gearing down allows you to use your clutches more efficiantly with the proper weights,springs and ramps.I agree longer tracks take more power to turn that is definately the reason you would want gear down and by clutching it properly could gain that track speed and more:d:d

 

[dooski]

I know of a 08XP with a 162 track with a race clutch in it with 59mph track speed. I have a M1000 with a 174 track and I am trying to achieve 60mph track speed

 

[cey800]

Speed Calculations:
Engine Speed ________(rpm) x Gear Ratio ___________ = _____________(rpm) Drive Shaft Speed
Drive Shaft Speed _______(rpm) x Driver Circumference ______(in) = ___________(in/min)Distance Traveled
Now convert inches per minute to miles per hour:
Distance Traveled _____________(in/min) / 12 (in/ft) = __________________(ft/min)
Distance Traveled _____________(ft/min) x 60 (min/hour) = _________________ (ft/hr)
Distance Traveled ___________________(ft/hr) / 5280 (ft/mile) = ________________ (mph)
7 tooth 2.52 pitch drivers = 17.64 inch circumference
8 tooth 2.52 pitch drivers = 20.16 inch circumference
9 tooth 2.52 pitch drivers = 22.68 inch circumference
10 tooth 2.52 pitch drivers = 25.20 inch circumference
7 tooth 3" pitch drivers = 21 inch circumference
8 tooth 3" pitch drivers = 24 inch circumference
9 tooth 3" pitch drivers = 27 inch circumference
10 tooth 3" pitch drivers = 30 inch circumference
Example:
Engine Speed 8000 (rpm) x Gear Ratio .5122 (21/41) = 4,097.6 (rpm) Drive Shaft Speed
Drive Shaft Speed 4,0976 (rpm) x Driver Circumference 22.68 (in) = 92,933.568 (in/min) Distance
Traveled
Now convert inches per minute to miles per hour:
Distance Traveled 92,933.568 (in/min) / 12 (in/ft) = 7,744.464 (ft/min)
Distance Traveled 7,744.464 (ft/min) x 60 (min/hour) = 464,667.84 (ft/hr)
Distance Traveled 464,667.84 (ft/hr) / 5280 (ft/mile) = 88.005 (mph)

 

[throttle-up]

Turbos are the only sleds I know of that get 80mph for track speed. I have a stock Dragon 800 163, geared down two teeth from factory and I am getting 46-50mph.

 

[HagmanMod1]

yeah thats right the only sleds i've ever seen with that much tack speed are turbo'd or have like 1200cc or more.my rev has about 180hp with a 162 2.5 and even with my race clutches i'm only pulling like 80 to 85kph on the hill and thats not to bad for not being turbo'd. you can only gear and clutch your sled so much you know. like throttleup said 50 to 65kph is good for a stocker especially with a track like that my xrs 159 with a little clutch work only pulled in the sixties

 

[cey800]

Great topic, thanks guy's

 

[mb1]

By gearing down you will give your motor a chance to use the clutches efficiently, as said above. Picture putting your quad ( manual tranny) in a different gear and going through some mud ( simulating a hill / load) First will be too slow, second is better, third best, then in fourth you can't hold rpm and 5th is nothing. But on the sled you have the clutches in the mix too.

I'm going from 21 / 39 to 19 / 42 this year.

 

[dooski]

hagman thats interesting that you are only getting 85km/hr track speed. I would like to know how this buddy of mine is getting 97km/hr track speed

 

[mb1]

hagman thats interesting that you are only getting 85km/hr track speed. I would like to know how this buddy of mine is getting 97km/hr track speed

Different snow, inaccurate speedo, slight exaggeration........clutching, track differences, rider weight, more exaggeration?

 

[teeroy]

cheapest, and best seat-of-the-pants feeling mod to a stock sled. I have geared down every new sled I've owned, along with clutching it feels like a different sled. (thanks Mitch, you da man)

I had an '01 MXZ 800X, it would do 105 mph on the speedo stock on an icy road. dropped one tooth on top, added 2 on the bottom and it still pulled 105and would go a year on a belt easily. clutches were never shifting out on the big end, theoretical top speed with the factory gearing was 126mph.

on my XP 146, with 19/45 (23/45 stock) gearing I get 50-55mph track speed in the fluff on a climb. the highest I've seen on the max readout was 62 later in the spring, top speed on hardpack is 88mph. before clutching and gearing changes it was 40-45 and a belt eating monster.

 

[dooski]

hey that could be but i was riding with him and it was impressive

 

[Modman]

The age old question with far too many parameters to answer as a generic response of "yes" or "no".

So often I hear the terms "track speed" and "efficiency" thrown around by people when they are comparing apples to oranges in most cases.

Efficiency - what efficiency? Temperature? belt slippage?

Are you actually measuring track speed in the same conditions, same parameters? Measuring track speed one day with a full tank of fuel in 3 feet of powder and hot clutches and another day with no fuel, the hood off and hardpack are night and day comparisons.

To truly compare what track speed does for your sled in a given situation, you need to take different sets of gears out to the hill with you and try it out. Some sleds with heavy weights and clean sheaves will grip a belt really well in powder and spin the track all day without heating up. That same sled might slip the belt like crazy on harder snow if it can't spin the track.

I have worked with the gearing on sleds for years. They are better now, but most mountain sleds still come stock with gearing too tall for its intended application. The original Summits and RMK's had flatlander gearing in them! The old 1994 583's would pull upwards of 90 mph on the forestry roads! Talk about slippage when they were hillclimbing.....

Drop a few teeth on the gears and give the motor the mechanical advantage, the belt will likely shift out farther in the clutches and keep the RPM's in the optimum power range with less slippage and less heat generation.

Slipping clutches are an exponential failure. As the clutch starts to slip, it generates heat in the sheaves and belt. The more heat it generates, the more it starts to slip.....the more it slips, the more heat it generates....and further down the spiral it goes.

Anyway, that's just my $0.02.:d

 

[HagmanMod1]

well i'd have to see your buddies sled actualy pull 97kph track speed before i will ever belive it! with my gearing and the way my clutches are it tops out at about 120kph on the lake. i lined up at the wall in allan creek against 2 turbo'd yami's and i took them until just before half way up the hill. and 85kph is only a guestamate because you all know how small the digital speedo is on the rev's

 

[northstar23]

When you are talking about track speed is that the speed of the sled?

 

[HagmanMod1]

to me track speed is how fast the track is turning when your climbing and track speed varies with snow conditions

 

[dooski]

I'll give you a hint.Its one of BAKERS SLEDS and he is from olds