gearing changes and top Speed for everyone!

[ski]

I noticed a few posts regarding gear changes, what chains are needed and what it will do to the top speed afterwards. I made a Micro$oft Excel chart with the gears and ratios listed and what chain is required. There is also a really easy to use formula box that you can punch in engine Rpm, ratio, and # of track drivers to get your theoretical top speed at 1:1 clutch shift.

The RX1 has a 19% gear reduction I don't know about Apex and Attack, if they are the same reduction it will work fine if not, let me know what the correct amount is and I will make a 3rd box for those models, right now there are 2 boxes one for Rx1 and one for non-gear reduction sleds with 2.52 pitch drivers which covers most sleds out there.

click here for the calculator, use engine RPM for the formula and know how many track drivers you have 8, 9 or 10. Any questions ask them here so everyone can benefit, and I won't have to answer the same question more than once hopefully.

You need Micro$oft Excel to use this.

 

[ski]

also let me know what you think of it or If there should be any changes. Thanks

 

[kinger]

Can you add a 25T gear, that is what I have but don't know what the bottom gear or chain is. Also what drivers are stock? Thanks!

 

[LazyBastard]

Take a look at this spreadsheet - it has all the relevant data.

 

[number1kyster]

A couple of members have said that by going wit ha 21t top gear on the vector i would gain top end. I did so but according to this chart i lost 8mph by doing so. If this is true then #*$&@ the 21t top gear ill go back to 22. Anybody have any truth to this chart?

 

[kinger]

I have no idea what bottom gear I have or what tooth drivers...

 

[LazyBastard]

A couple of members have said that by going wit ha 21t top gear on the vector i would gain top end. I did so but according to this chart i lost 8mph by doing so. If this is true then **** the 21t top gear ill go back to 22. Anybody have any truth to this chart?

This chart does NOT tell you ACTUAL top speeds, it tells you THEORETICAL top speeds.

What this means is that ASSUMING 100% driveline efficiency and PERFECT traction with no slip whatsoever, and with the engine turning EXACTLY given RPM, then since x engine revolutions = y driveshaft revolutions in s seconds, and y driveshaft revolutions = z distance the track has moved (given t driver size), the sled has moved z distance / s time, and that is the speed.

Of course, you can NEVER get 100% driveline efficiency, and you can NEVER get perfect traction, AND since in most cases, you can never get full clutch shift out, combinations that give LESS than maximum theoretical speed may, in fact, give maximum ACTUAL speed.


In the case of gearing down from 22 to 21, this change results in a different, and possibly more efficient clutch ratio, which can result in improved top speed.

 

[LazyBastard]

I have no idea what bottom gear I have or what tooth drivers...

If they're stock for 03, then 38 tooth bottom gear, 9 tooth drivers.

 

[kinger]

I have no idea what bottom gear I have or what tooth drivers...

If they're stock for 03, then 38 tooth bottom gear, 9 tooth drivers.

Thanks that shows a top speed theorical max of 133mph and I hope to radar this winter but I'm thinking it will actually to 135mph on the bottle. I better confirm what drivers and bottom gears I have. Thanks

 

[ski]

Yes exactly what lazy bastard said. Just changing the gear will not make your sled faster or slower for sure.... you need to have the clutching efficiency and horsepower to make it get there as well.

Also some (most) sleds are over geared stock and may see an increase in acceleration by lowering the gear ratio with either no loss in actual top end or a gain in top end due to putting the clutch in a more efficient range.

Say you sled does 105 on gps, but the theoretical top speed on my chart is 118mph, lowering the gear ratio to show a 112mph theoretical top speed may make the sled accelerate faster and improve top speed by 2 or 3mph .... or it might not ... depends on many conditions and variables .. this chart just gives you an Idea where to start, or at least where you started from.

 

[ski]

Take a look at this spreadsheet - it has all the relevant data.

So according to your chart the Apex / Attack do have a different gear reduction ratio? 37:30 as opposed to 37/31?

 

[ski]

Can you add a 25T gear, that is what I have but don't know what the bottom gear or chain is. Also what drivers are stock? Thanks!

ok, I added 25t gear, clear you browser cache and download it again.

Also, just added Apex/Attack formula as well.

 

[LazyBastard]

So according to your chart the Apex / Attack do have a different gear reduction ratio? 37:30 as opposed to 37/31?

Yeah, something like that. 06+ are geared lower to the PTO.

 

[YamerDown]

For those that have used this calculator, do you find it accurate?

I've got an 03 Viper, stock gearing should be 22/38, clutched to run at 8600, and it's got 9 tooth drivers on it. According to the calculator my top speed should be 106.77. Last year, both on Radar and GPS, I was able to hit 114.3 MPH???

I haven't checked the gears, but I'm fairly sure they are totally stock. Wouldn't matter much anyway, as I don't think the Viper has the HP to pull a lower ratio. Based on the calculator, my sled must have 23/37 gears in it. Yah, right.

Anyway, just thought I'd ask how other's results have turned out.

 

[LazyBastard]

The formula's right. Your tachometer is off.