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Gearing....Would like some options

1K views 22 replies 13 participants last post by  doo rider 
#1 ·
I was considering changing the gearing in my sled, just for sh&%s and giggles my stock gears and chain are 43B 23T and 74 link chain......My ? is how many teeth can I add to the top gear without changing chains...........The sled is an 800ho with under a thousand miles on it

Would like to try a 26t on top if possible


Thanks in advance for your advice.......Doug
 
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#3 ·
Why do you want to gear up? These sleds are already geared to a higher top speed then they can attain. Gearing up will probably not provide you any higher top end but will definately provide you with a dog on the bottom end. You can drop 2 teeth on top and drastically improve your low end response while having little if any affect on top speed.
 
#4 · (Edited by Moderator)
With the 10 lug drivers you have... you will hate a 26 tooth top gear with the 43 bottom gear.... if you did go spend the money for the longer chain. You will not only lose acceleration but you will probably also lose top end... no way can you pull that gear ratio..

You will probably have better acceleration and higher top speed with a 22 or 21 tooth top gear. Doo's are notoriously over geared from the factory..

But trial and error is the best way to learn... I probably have one of the longer chains and the 26 tooth gear if you want to make yourself unhappy..

REVin soon is right on.....
 
#6 ·
These guys are right.
Drop 2 teeth to 21
You will find a big difference low end and little if any on top.
It allows the engine to wind up quicker on acceleration
and make better power
It's worth the price of a gear to find out.
Good bang for your buck.
 
#8 ·
That's the right approach, go with both bigger bottom and top gears and a longer chain.. rolling the chain over bigger radius a little less friction loss probably hard to measure .. but it's one of those things in the right direction.. keep stacking things up in the right direct and pretty soon you are faster..and quicker..But most people go with the cheaper approach (gears are roughly two dollars a tooth.. and thus top gears are cheaper then bottom gears..so most opt to go with a couple of less teeth on the top gear..
 
#10 ·
ok, needs some opinions on this.

I've got an 03 800 that has some nice mods to it. Porting, head, etc. Maybe a new pipe yet too. Anyway, 26/43 gears were stock w/ 9 tooth drivers. At a 1:1 ratio, thats 102 mph. Maybe get a little into overdrive.

I believe that efficiency goes to he11 after 1:1 ratio. I saw a graph somewhere (I think it was Aaen's manual). So wouldn't it be better to gear up and attain a higher speed at 1:1? I would hope that my sled should put 110 with decent conditions, and gearing down would require it to go way into overdrive to attain 110.

Also, if you gear down you probably are spinning the track like mad at launch. Is this the best way to accelleration, or would it be better to be right at the verge of spinning but not spinning, like in a car?

thoughts? Thanks!
 
#13 ·
L]...I believe that efficiency goes to he11 after 1:1 ratio.
J]...How so?

L]...I saw a graph somewhere (I think it was Aaen's manual).
J]...What secondary details was he using?

L]...102, 1:1 way overdive to get 110.
J]...full o.d. = 122 in your case.

L]...Also, if you gear down you probably are spinning the track like mad at launch.
J]...make suspension transfer better.

L]... Is this the best way to accelleration, or would it be better to be right at the verge of spinning but not spinning, like in a car?
J]...make suspension transfer better.
 
#16 ·
Hey Joe,

The manual talks about efficiency looses due to belt stretching, belt side pressure, turning radius, belt speed, etc. When in overdrive, the secondary clutch is spinning faster than the primary, and this high belt speed yields efficiency loss due to belt tension and centrifigul force. I'd also imagine that having less contact area with the secondary while in overdrive lends to more slippage. It states that best efficiency is between 2:1 and 1:1. With stock gearing on the 03, thats between 51 and 101 mph.

So if the starting ratio is 3:1 (this probably varies some), I think that means that the clutches don't start shifting until 34 mph. So there is low efficiency between 34 and 51, best between 51 and 101, and then falls off in overdrive.

So, if you're doing alot of corner to corner riding, you'd want lower gears so that when you exit the corner, and you you nail the throttle, the clutches haven't fully closed, and your rpms will go right to peak hp without having to be down on the power curve and then have to pull back up toe peak before beginning to shift out the clutches.

I know it's alot more complicated than that, but am I even making sense?
 
#14 ·
Never fear the Gear! I look at it as this. Where do I spend the bulk of my riding time? I spend a majority of time at lower speeds under 85 mph. So, I gear it to where it helps me most for the bulk of the riding that I do. 21/45 for me.
 
#19 · (Edited by Moderator)
Hey Joe,
The manual talks about efficiency looses due to belt stretching, belt side pressure, turning radius, belt speed, etc. When in overdrive, the secondary clutch is spinning faster than the primary, and this high belt speed yields efficiency loss due to belt tension and centrifigul force. I'd also imagine that having less contact area with the secondary while in overdrive lends to more slippage. It states that best efficiency is between 2:1 and 1:1. With stock gearing on the 03, thats between 51 and 101 mph.

So if the starting ratio is 3:1 (this probably varies some), I think that means that the clutches don't start shifting until 34 mph. So there is low efficiency between 34 and 51, best between 51 and 101, and then falls off in overdrive.

So, if you're doing alot of corner to corner riding, you'd want lower gears so that when you exit the corner, and you you nail the throttle, the clutches haven't fully closed, and your rpms will go right to peak hp without having to be down on the power curve and then have to pull back up toe peak before beginning to shift out the clutches.

I know it's alot more complicated than that, but am I even making sense?
Lootski howzit goinski...


L]...efficiency looses due to belt stretching,
J]...Heh, I really don't like talking as if im reading a resume', however its hard to describe otherwise without knowing my experiences to offer information with a little bit of weight. I do "reliablity specialist" studying vibration analysis and focus on static/dynamic belt driven equipment.
At one time, being part of a design group, I have discussed this comment with engineers from Reliant/Dodge, goodyear...

These gents quote: Regarding "Stretch".
The belt has that aramid fiber band woven, spun as the tension section; The rubber blend cover is made as a solution around this aramid fiber.
Under load the belt is like a steel band.
...Belt rubber deforming...yes; The rubber must deform to follow the sheave path when the belt is pulled.
...Belt stretch?...No!

L]...belt side pressure
J]...How do you calculate this? How would you use the values?

L]...turning radius
J]...Ok.

L]...belt speed, etc.
J]...What would the values tell you? Something good? Something bad?

L]...When in overdrive, the secondary clutch is spinning faster than the primary, and this high belt speed yields efficiency loss due to belt tension and centrifigul force.
J]...Ok then, what will you do with this information? Will it help you calculate something?

L]...I'd also imagine that having less contact area with the secondary while in overdrive lends to more slippage.
J]...GREAT! Now we're getting somewhere. Now you are talking with a principle.
Q]...What do you do to reduce belt slip?
A]...Grab it harder.

Question]...How do you grab the belt harder?
Answer]...Increase the side FORCE.....not "pressure" Do you weigh 195 lbs pressure? No, you weigh 195 lbs...gettit?!!

Question]...How do you increase the side force?
Answer]...Increase spring force and/or use lower helix angle vs. previous values.

Question]...How do we know to make a change in the right direction?
Answer]...How do you know there is slippage?

Comments]...Hot temperatures
Question]...Why is there hot temperatures?
Answer]...Belt slip
Question]...How do you reduce belt slip?
Answer]...Grab the belt harder.
.
.
.
.
...Gettit?!!
Efficiency losses due to, blah blah blah... Well we know inefficiency reveals high temperatures, then who cares about all that stuff - Yes it's good to know, however don't let that stop you from experimenting.

*Inefficient = belt slip = high temperatures. Efficient = less belt slip = lower temperatures.
Now would this "*" be more important to know than "efficiency loss, because" ?
Now only need to care how to reduce temperature.
Clamp the belt harder to reduce temperature and tell me anything else that matters.

How do you know how to grab the belt?.....Know "Clutching IQ" he he he
 
#20 ·
Hey DJ,

I'm way over my head on this stuff, just restating what I've read. But yet I continue on...


So the question is, based on less belt contact area and a tighter radius as we approach overdrive, if I were to be setting up for a speed run event, wouldn't it likely be better to use gears that will allow me to top out at near 1:1, vs going way into overdrive?
 
#21 · (Edited by Moderator)
Linking theory and exercises
You have to start somewhere,

I like to start with learning what speeds that consistent sleds are going across the finish line - [In the field that the test sled will be running in.]
I follow a Capacity Building regimen where my exercises leave gearing alone and focus on improving the clutches ability to achieve the "X" mph.
By taking a snapshot of what the field is doing you can link the theory you know to the excersises you do.
Example; For lack of better numbers, If the field is going across the line at 100mph then I like to calculate my gear ratio for being at 1:1 at the finish line or just a little before, at 100 mph. If that sled is going across at 100 mph then I want to go across the line at least that fast.
...how to get there is just different exercises.
Regardless of racing discipline grass or ice or whatever; What I've done by gearing my sled to go as fast as a good field sled, i've temporarily set aside the detail "gearing" in the drive system so I can concentrate on clutch tuning. I know my sled is geared for 100 mph, how do I go about grabbing the belt correctly to get there?
I don't ask people what I should do.
I don't recommend tuners to ask other tuners what to do - what do they know about your sled?...other than say "try this" or "try that". This is tuning by "hope" and hope just cost money and grief. he he he

I start asking the sled's clutches "Why am I not achieving that mph?"
...use the clutching principles you know to learn how to grab the belt with the "required" amount.
 
#22 ·
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