too low of gearing?

ruffryder · Nov 20, 2008

How do you know if your gearing is too low? Is there such a thing? I could care less about top speed in the mountains, just curious what some symptoms of gearing too low could be.

I know that if you gear lower and your top speed is decreased and you want top speed you had a negative effect. I am more looking towards mountain type symptoms. I run around 48 MPH track speed in a climb, and I can do 85+ on the trail. My thinking says that I can still gear lower.

When I say low, I am talking numerically higher gear ratio. I am went from 2.0 to 2.11 and thinking about going to 2.33 since top speed is still quite high.

Thanks

longhairfreak · Nov 20, 2008

Gearing is relative to proper clutching. You want your clutches to fully shift out.

shortstop20 · Nov 20, 2008

In AAEN's clutch tuning book he says you should gear your sled so that you are using the 1:1 ratio in your clutches for the majority of your riding, since that is the most efficient ratio in the clutches.

sled_guy · Nov 20, 2008

Yes, you can gear too low. It seems all the rage these days to gear sleds way down. Really low gearing can make for very erratic clutching with RPMs that won't hold and that bounce all over the place.

sled_guy

Ancient Sledder · Nov 20, 2008

I am starting to think the same way. I get 42 mph track speed with a 151 x 2. My top speed is 75 mph on the flats. Now if I could gear it down to 60 top speed, would my track speed increase to 50-55 mph? I don't think I can fit much lower gears in the case and I don't think anyone makes 4 tooth drivers yet.

johnsodo · Nov 20, 2008

last year i ran 21/37 with a 159'' and this year im going to run a 22/39 with a 151'' i might go to 23/39

RockyMtn.Kris · Nov 20, 2008

Too low for me is anything under 80mph max. You still have to ride the trail to get there. Too low and you feel like you are stuck in first gear. I have experimented with gearing using a jackshaft sensor for a few years now and I think gearing for 80-85mph is good all around for mtn. riding. Gearing down will get you closer to the 1 to 1 ratio but in reality you will be closer to 2 to 1 with both clutches loaded

shortstop20 · Nov 20, 2008

RockyMtn.Kris said:
but in reality you will be closer to 2 to 1 with both clutches loaded

I'm confused as to what you mean?

I am geared at 2.10 ratio(88 MPH top speed)works very good for me.

svensdream · Nov 20, 2008

shortstop20 is on the right track, you want to gear down so that the track speed matches what the motor is capable of spinning the track at when the cluthes reach their 1-1 ratio (full shift on stock clutches).

I.E. if an 800 is capable of spinning the track at 50 mph on a hard climb than the sled should be geared close to or slighty above this speed, which will reduce belt heat/ wear and reduce drivetrain stress.

gearing is based on track length, paddle highth, driver diameter, and size of motor. a bigger motor will make more stack speed, that is why JOHNSODO can run tall gears- gotta love that big-ol 1200

ruffryder · Nov 20, 2008

svensdream said:
shortstop20 is on the right track, you want to gear down so that the track speed matches what the motor is capable of spinning the track at when the cluthes reach their 1-1 ratio (full shift on stock clutches).

I.E. if an 800 is capable of spinning the track at 50 mph on a hard climb than the sled should be geared close to or slighty above this speed, which will reduce belt heat/ wear and reduce drivetrain stress.

So based on that, and thinking about available gearing options for most sleds, you really can't go too low then? I don't think you can gear down to 50mph on any sled.... unless you cut off a cylinder here or there...

johnsodo said:
last year i ran 21/37 with a 159'' and this year im going to run a 22/39 with a 151'' i might go to 23/39

Your gear changes seem interesting... since one tooth on the top is roughly equal to two teeth on the bottom, increasing one on top and two on the bottom seem to have a very slight effect / noticable change....?

I went from 20-40 to 19-40 and will soon be going to 18-42. This is all on a stock (no boost anyways) MTX.. Might be getting a bigger track in there, but we shall see....

Good information, thanks for the help yall!

Throttle Junkie · Nov 20, 2008

700summitguy said:
I am starting to think the same way. I get 42 mph track speed with a 151 x 2. My top speed is 75 mph on the flats. Now if I could gear it down to 60 top speed, would my track speed increase to 50-55 mph? I don't think I can fit much lower gears in the case and I don't think anyone makes 4 tooth drivers yet.

No you would need more HP and an 800 to pull those track speeds.

You want to run close to 1:1 while climbing. best thing to do is mark the primary with a sharpie make a climb and see how far it's shifting. I thought full shift out was more that 1:1..overdrive?? no? I alway like to see the belt about 3/4 of the way up the primary while climbing.

ruffryder · Nov 20, 2008

Throttle Junkie said:
I thought full shift out was more that 1:1..overdrive?? no?

I think skidoo's are the only secondary that allow overdrive... I think they go to like .85 or something, though I am not sure on that number....

Motley Doo · Nov 20, 2008

I'm running 19/47's with 7 tooth 3" pitch drivers. It's pretty low, will do about 60-65 top speed, but I don't have a speedo anymore so that's from a buddies sled along side of me. I do really like it in the steep though! Build very little clutch heat, very easy on belts, it was a little hard to get clutched, but nothing impossible!

ruffryder · Nov 21, 2008

Cosarguy said:
Not sure I understand this part of your post. A 1 to 1 ratio is when both clutches (primary and secoindary) are turning at approximately the same speed, (The belt would be somewhere near the middle of the sheves) not when they are fully shifted out.

Full shift out is 1:1 on most sleds...

CATSLEDMAN1 · Nov 21, 2008

Gearing an Going

When you're playing with all your drive train variables keep in mind a gearing change and loss in performance may not be the result of your lower gearing.

1. in your chain case style sled.......... you will notice a loss of efficient tranfer of power when you use a 19 tooth top gear or less. Read the technical data ......... they have the numbers for efficiency loss when you spin that chain around a little sprocket. So........if it looks like a 19/40 gearing combination is what you want ( .475 ) , your way better off to use 20/42 or ( .476 ) gears, so most tuners are limited by how big a bottom sprocket you can use in a chain case and what chain lengths are available.
If your sprocket and chain combination has a big loop of slack in your chain wrapped around an idler wheel, you shooting your self in the foot again, as any sharp turn in that chain is sucking power out of your drive train. If I recall on the cat chain cases.........20/43 with a well broken in chain or you wont get it in, give you a good low gear, the idle adjuster can be thrown out, you'll minimize chain breaking and its a good effiecient set up.

2. Ditto for small drivers, wrapping that track around 7 tooth drivers at 50mph is way not good, sucks power. Cat used to run those dinky rear idle wheels to make their suspension scissors work / and so did M10 SUSPENSIONS, sucked track power but made the paralellogram work, 7/8/10" rear wheels became the rage, more efficient tracks even if the suspension sucked and ratcheted.

3. Aaen's clutch book says 1 : 1 is ideal drive ratio ? Sure, that's where your belt has to turn the two gentlest corners when spinning in your clutch's, less power loss, less belt heat from bending.

Arctic Thunder · Nov 21, 2008

ruffryder said:
Full shift out is 1:1 on most sleds...

Your telling me that the outside of your primary when the belt runs is the SAME diameter of the bottom of your secondary. This is full shift out? There is no way these are the same diameter. So 1:1 isn't even close to full shift out.

The main goal is to run near 1:1 ratio between the primary and secondary. This has been proven to be the most efficient ratio. Also I believe this is the point where your primary and secondary have the best hold on the belt. So less slippage. (Where are most of your black marks on your primary? At the outside Dia I would bet) But I personally like to run about 3/4 the way out of the primary on a pull. Seems to pull better. Do the sharpee marker trick, it works.

But it has been my opinion that the taller gear you can run and pull the R's the more track speed you will have.

I tried about every gear combination on my 900 cat and the lower I went the worse it climbed. Kind of like being stuck in first gear all the time. You have to get into the taller gears to get the track speed. But again it is a balance between pulling the R's and spinning the track.

Thunder

ruffryder · Nov 21, 2008

Arctic Thunder said:
Your telling me that the outside of your primary when the belt runs is the SAME diameter of the bottom of your secondary. This is full shift out? There is no way these are the same diameter. So 1:1 isn't even close to full shift out.

Correct, but you are comparing ID's and OD's... also, if you look at the secondary, the belt is never supposed to be at the bottom, it is not supposed to touch, so you need to adjust your viewing line accordingly.....

Vern · Nov 21, 2008

on poos we've always liked right around 2.25:1 ratio, had good luck with it. my m7 is much lower in the DD but i dont know how the final drive differes from the chain case sleds. never did much with doo or yammi just one or two in the past so i dont remember what they were.

rynokron · Nov 21, 2008

Keep a close eye on your chain tension and top gear wear if you go with a 18 tooth. That is a tight bend and hard on the chain and sprocket. I am running 19/42 with 9 tooth drivers on my "vintage" mod sled.

AdrenalineAddict · Nov 21, 2008

According to the centri***al clutching efficiency charts I've studied once you hit a 2:1 shift ratio (which is approximately 46 mph trackspeed with 2.1:1 gearing and normal size drivers) your clutches are 92% efficient. 92% is about as good as centri***al clutching gets. 1:1 shift ratio is only 91% efficient. I've never found any gains in trackspeed (or belt life)going lower than 2.1:1 gearing and you'll still cook down the trail at 85 mph if you like. It won't let me spell centri***al because there is a *** in there.

too low of gearing?

Well-known member

Well-known member

Well-known member

Member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Similar threads