speedometer off with 7 tooth?

[freak485]

I am running the x3 162 with 7 tooth drivers and my last trip everyone was doubling if not more miles than me in a day and i usally do more riding then the rest of the group. And i pretty sure its off just since i know what i usally would put on in a day in the area was riding. Anyone else have this?

 

[pfi572]

Drivers are 8% smaller than if you had 8 tooth on.
So should be reading the other way.
More miles than others . Weird
If you have GPS I would check it.

 

[steepndeep800]

More than likely due to less track spin, the 3" will really hook up compared to most other tracks.

 

[newtrout]

More than likely due to less track spin, the 3" will really hook up compared to most other tracks.

X2. I noticed this too.

 

[Scott]

It's been geared down.
It IS off.

stock drivers are 2.86 pitch with 8 teeth= 22.88" circumference

these drivers are 3.0 pitch with 7 teeth= 21" circumference.

If those are drivers are trued, then that comes out to 9.17% smaller circumference.

Your speedo is off by 9%. In theory, you are going 9% further and 9% faster than what your speedo and odometer say.

Because of how that track performs, less track spin IS also a factor.
I amazed at how mine performs after my first ride out on it. Can't wait for better snow conditions.

 

[Scott]

I am running the x3 162 with 7 tooth drivers and my last trip everyone was doubling if not more miles than me in a day and i usally do more riding then the rest of the group. And i pretty sure its off just since i know what i usally would put on in a day in the area was riding. Anyone else have this?

Ride down the trail side by side at a few different speeds to get a speedo reading.

10mph, 25mph and 50mph. You'll see that you are about 1mph slower at 10 and about 4 or 5mph slower at 50.

 

[Solby]

Scott,

Shouldn't it be the other way around?

If you reduce the diameter of your driver the driveshaft will have to turn it faster to make the track speed faster.

Ex.
If your buddy has a stock sled and the actual speed of the sled is 50 mph and it shows 50 mph on the dash.

To get the geared down sled to go 50 in actual speed the dash will show 54.5 mph

 

[Sixat38]

Solby's correct.
But rereading what Scott said he may be correct just not explaining it very well. His math is correct with regard to circumference and distance traveled per revolution of the drive shaft.

In Scott's analogy, if two guys run down the trail at 10mph on the gauge, the guy with the 7T drivers will fall behind. Or at least I'd like to think that what Scott meant.

Now if Scott was meaning they run down the trail side by side at the same ground speed he is wrong. In this case the guy with the 7T drivers gauge would read 11mph (approximately). What Solby said.

 

[Scott]

Ok, yeah, I was confusing.

Is it correct to say that if you are using 7t drivers and your buddy is with 8t drivers and you are both holding at 50mph on your speedos, YOU will be falling behind.

 

[Scott]

If you travel down the trail at the same ground speed, the guy with 8t drivers says 50. The guy with 7t drivers will say 54/55.

 

[byeatts]

I am running the x3 162 with 7 tooth drivers and my last trip everyone was doubling if not more miles than me in a day and i usally do more riding then the rest of the group. And i pretty sure its off just since i know what i usally would put on in a day in the area was riding. Anyone else have this?

thats because it only took one pull to hit the top, others grind all day long!

 

[byeatts]

It's been geared down.
It IS off.

stock drivers are 2.86 pitch with 8 teeth= 22.88" circumference

these drivers are 3.0 pitch with 7 teeth= 21" circumference.

If those are drivers are trued, then that comes out to 9.17% smaller circumference.

Your speedo is off by 9%. In theory, you are going 9% further and 9% faster than what your speedo and odometer say.

Because of how that track performs, less track spin IS also a factor.
I amazed at how mine performs after my first ride out on it. Can't wait for better snow conditions.

In Theory however the actual cir. of an Avid is much smaller than 21 in.. If I recall they were 20.1 cir.

 

[Scott]

In Theory however the actual cir. of an Avid is much smaller than 21 in.. If I recall they were 20.1 cir.

I have heard they are indeed actually smaller. I have not heard any numbers yet though.

Thanks.

 

[TRS]

Lets look at this from a different perspective. On the trail with no fold over.

7 tooth drivers with 3.0 pitch and 3" track
7x3=21
21*3.1415=6.6847
6.6847+6=12.6847

8 tooth drivers with 2.86 pitch 2.4" track
8x2.86=22.88
22.88*3.1415=7.2831
7.2831+4.8=12.0831

Lets use a 2.5" track
7.2831+5=12.2831

Can we agree on paper the 7 tooth 3" pitch track 3" lug is geared taller?

 

[Scott]

Lets look at this from a different perspective. On the trail with no fold over.

7 tooth drivers with 3.0 pitch and 3" track
7x3=21
21*3.1415=6.6847
6.6847+6=12.6847

8 tooth drivers with 2.86 pitch 2.4" track
8x2.86=22.88
22.88*3.1415=7.2831
7.2831+4.8=12.0831

Lets use a 2.5" track
7.2831+5=12.2831

Can we agree on paper the 7 tooth 3" pitch track 3" lug is geared taller?

I'm not quite sure what some of the numbers mean in your formulas. Help me understand them.


G to this spreadsheet and look at the blue numbers. Play with the numbers in the blue boxes to see how it affects that yellow MPH box.

With all numbers the same except track pitch and teeth drive sprocket, 8t 2.86 pitch says the track moves 79.4. Change drivers to 7 and go 3.0" pitch...it drops to 72.9. That's lower geared, not taller.

 

[freak485]

I am confused also lol. I also have 19/43 gearing. Not sure how much that changes it also. Go math gurus!

 

[Solby]

So.....
If I'm going 50 on my pro with a 2.4" track
my dad is going 50 on his cat with a 2.6" track
my buddy is going 50 on his XM with a 2.5" track
When will we arrive at the pow????

 

[Sixat38]

TRS is throwing some number I remember from school as Pi, at the circumference to get the diameter. Then adding twice the height of the paddles to get an overall diameter of the rotating track that's in contact with the snow. If you work the diameter backwards from there to get a circumference, it looks good on paper, as far as how far you may be traveling in one revolution compared to the other guy, but still falls short when reading the gauge. It does provoke some thought. I like it. It falls short on the overall gear ratio too.

What its should tell you is something about the torque at the tips of the paddles, assuming no fold over, and what might be required in way of clutching & gearing to turn such a large diameter.

Or just go ride and fugetaboutit.

 

[TRS]

I'm not quite sure what some of the numbers mean in your formulas. Help me understand them.


G to this spreadsheet and look at the blue numbers. Play with the numbers in the blue boxes to see how it affects that yellow MPH box.

With all numbers the same except track pitch and teeth drive sprocket, 8t 2.86 pitch says the track moves 79.4. Change drivers to 7 and go 3.0" pitch...it drops to 72.9. That's lower geared, not taller.

But you forgot part of the equation. You have a 3" lug track versus a 2.4" lug track. If you are comparing 2.5" tracks in either pitch you are correct.
What I did in each case was take the circumference of each driver and divided by Pi to give you diameter and added lug height.
So lets use radius which is half the diameter and add lug height.
So a 7 tooth 3.0 pitch track with a 3" lug has a 6.342" radius
a 7 tooth 3.0 pitch track with a 2.5" lug has a 5.842" radius
an 8 tooth 2.86 pitch track with a 2.4" lug has a 6.041" radius
An 8 tooth 2.86 pitch track with a 2.5" lug has a 6.141" radius

 

[byeatts]

But you forgot part of the equation. You have a 3" lug track versus a 2.4" lug track. If you are comparing 2.5" tracks in either pitch you are correct.
What I did in each case was take the circumference of each driver and divided by pie to give you diameter and added lug height.
So lets use radius which is half the diameter and add lug height.
So a 7 tooth 3.0 pitch track with a 3" lug has a 6.342" radius
a 7 tooth 3.0 pitch track with a 2.5" lug has a 5.842" radius
an 8 tooth 2.86 pitch track with a 2.4" lug has a 6.041" radius
An 8 tooth 2.86 pitch track with a 2.5" lug has a 6.141" radius

No. The lug Height does not alter the speedo.. The skid is a flat surface, The belt is moving at the same rate as the tip of lug, ONLY on a round wheel does the tip run at a faster speed.