MPH change with larger drivers??

[Sapling-Thrasher]

I am running 8 tooth drivers and wondering the effects on my MPH on the Yamaha gauge?

In theory I have geared up a bit.

One revolution is now 24 inches vs. 21.

I know one of you is a math wiz and has a quick formula for this.

Search function is not as good anymore since you can't use the old site info.
Thanks

 

[Sixat38]

So you wnet from 7t-3p drivers to 8t-3p.

There's a couple of different ways to try and explain it but this might be the easiest. Since your probably wanting to check track speed while climbing. At least that's the boat I was in.

50mph X 21 / 24 = 43.75mph. Your gauge will read 44mph but your track speed will be 50.

Your gauge will loose 1.25mph for every 10mph. Confused?

 

[Sapling-Thrasher]

That is exactly what I was looking for.


Is there is a way to correct the computer to read correctly???

 

[Sixat38]

That one I don't know. But I doubt it.

 

[obr]

actually, your seeing more correct speed now...We've tested with radar, and the speedometer is WAY of with 7tooth drivers...

 

[Ultralord]

So you wnet from 7t-3p drivers to 8t-3p.

There's a couple of different ways to try and explain it but this might be the easiest. Since your probably wanting to check track speed while climbing. At least that's the boat I was in.

50mph X 21 / 24 = 43.75mph. Your gauge will read 44mph but your track speed will be 50.

Your gauge will loose 1.25mph for every 10mph. Confused?

DUDE---- GIVE UP THERE IS NOT A HILL IN WASHINGTON YOU SLED WON'T CLIMB ANYWAY ARE WE GOING RIDING ON WEN?

 

[Ultralord]

That is exactly what I was looking for.


Is there is a way to correct the computer to read correctly???

Is there a gear on the speed sensor?

 

[Sapling-Thrasher]

Yep there is a gear on the drive shaft that the sensor works off of. I might be able to make Thursday but I won't know until tomorrow. I was pulling 76MPH of track speed on big house at Baker at 14 lbs and my A/f was off a bit. That would put me at about 85.5 MPH if you use the formula above. I was hoping for more!!!

I got a 15 wide track coming. 16 wide soon to be for sale. I am ditching the Simmons as well. They tuck under at speed on harder snow really bad!! Down right scary!!

I might have to give her more boost!!

 

[Ultralord]

Yep there is a gear on the drive shaft that the sensor works off of. I might be able to make Thursday but I won't know until tomorrow. I was pulling 76MPH of track speed on big house at Baker at 14 lbs and my A/f was off a bit. That would put me at about 85.5 MPH if you use the formula above. I was hoping for more!!!

I got a 15 wide track coming. 16 wide soon to be for sale. I am ditching the Simmons as well. They tuck under at speed on harder snow really bad!! Down right scary!!

I might have to give her more boost!!

I would think if you change the gear tooth count you could get the spedo accurate. I dont know what my track speed is I was to affaid to look I am still just learning how to hang on.

 

[Ultralord]

I will go on thursday if the new motor works out saturday to

 

[TurboKeith]

Yep there is a gear on the drive shaft that the sensor works off of. I might be able to make Thursday but I won't know until tomorrow. I was pulling 76MPH of track speed on big house at Baker at 14 lbs and my A/f was off a bit. That would put me at about 85.5 MPH if you use the formula above. I was hoping for more!!!

I got a 15 wide track coming. 16 wide soon to be for sale. I am ditching the Simmons as well. They tuck under at speed on harder snow really bad!! Down right scary!!

I might have to give her more boost!!

I ran a 15 wide challenger extreme on mine for about 3 months. It did get better track speed and was a little faster on the top end. It just didn't have the hookup or flotation that the 16 wide challenger extreme has.

 

[Ultralord]

I ran a 15 wide challenger extreme on mine for about 3 months. It did get better track speed and was a little faster on the top end. It just didn't have the hookup or flotation that the 16 wide challenger extreme has.

I think his issue is the sled shows its weight on a sidehill in harder (normal)western wa snow. I have ben thinking about it but I will use sap for my R&D my wife is looking for my credit card I need to lay low after the apex then the turbo then the skid, tunnel body parts and then a new motor and a 16 wide 2.5 that now I regret

 

[Sapling-Thrasher]

It is mobility issue not a traction or track speed issue. With the track speed this thing makes I can afford to give up a little traction/flotation to have better sidehilling and quicker response side to side (if that is possible on an Apex on hard snow!!)

I figure I can sell the 16 that I ported and clipped and buy the new one and only be out a couple hundred......that and the 15 is 5-6 pounds lighter!!! I will hold onto the 16 until I decide if the 15 inch is the better choice.

Anyone want a set of brand new set of Simmons? Grey on black??

 

[Sixat38]

I've been had

Yeesh... Sap, you have a sled that will climb tree if you ask it and I tought I was helping you with a real problem. Worrying about 75 or 80 mph track speed, now that's funny stuff right there. I remember when 50mph was the target. Well I guess it still is with most mortal sleds.

However, one note, if you don't get the gear changed (or whatever) to get your MPH corrected your odometer will be off too. It will read less miles for the same distance traveled when you had the 7T drivers. I.E. you will wonder why you can only get X miles out of a tank when you used to get X amount more.

 

[Sapling-Thrasher]

I try to keep track of my miles for oil changes. (not that 10 % is going to matter) I am changing oil every 125-175 miles. Or every third full day of riding. The oil gets bad pretty quick!

On days prior to my switch to 7 tooths I have seen the speedo at just over 100 running 15-16 pounds. I knew it would read less was just trying to compare to what I had seen before.