• We are no longer supporting TapaTalk as a mobile app for our sites. The TapaTalk App has many issues with speed on our server as well as security holes that leave us vulnerable to attacks and spammers.

Top Speed Lacking

Supa Dexta

Expert
Joined
Apr 20, 2011
Messages
471
Location
Canada AB/NS
Just got back from a week long trip and although I didn't need top speed most of the time, when I did push it - it wasn't there.

My sled started as a 121 - its now stretched to a 144 with a 2" track, and 8 tooth drivers. I'm topping out at 75mph on GPS. I know I've got more out of this before, but I didn't have a ton of miles on it with this set up, and never GPS'd, so I'm not sure how much the 8 tooths set me back.

I am getting 8900rpm pretty consistently, spiking to 9100 at times across the lake, hitting little drifts. Nothing done to the clutching as far as I know. Worst part is I'm now away for work, and there's little chance of any more miles this season. I believe my belt is in good shape, I should have thrown a brand new one on, just to see.. But am I not shifting out?

2100 miles/3500km on the sled, seems to pull hard down low.

Gearing calc's show I should be around 90 mph with the 8 tooth drivers, coming from 101mph stock.
 

I'm going to have to say secondary clutch work plus maybe go up one tooth
 
Gearing calc's show I should be around 90 mph with the 8 tooth drivers,

Gearing calc does not compensate for the 2" track. I believe that's where your speed is going
 
Gearing calc's show I should be around 90 mph with the 8 tooth drivers,

Gearing calc does not compensate for the
144" x 2" track. I believe that's where your speed is going
 
I just can't believe I'm down 25mph (an additional 15 cause of the track), the xtx guys can't be down this much, but they generally start a bit higher.
 
The 2" track is going to be partly responsible for sure. Not only is it more rotating mass but also the resistance moving through the air and carrying snow load. (Depending on conditions) From my experience there is decent jump going from 1.75" to 2" for some reason, like you are crossing some magic barrier.

The other thing is the efficiency of your driveline. The smaller diameter drivers have changed the path of your track takes. It's now turning around a smaller diameter then approaching the front of the rails at a different angle. I'm not going to throw any physics at ya cause I failed that in high school. This is simply what I have been told by older wiser sledders and I have experienced it as well.

All that being said you still seem like you are down more then you should be. Did you make any changes to your clutching when you went to 144 and 8T drivers??

The other factor is conditions. My experience is the big tracks are more susceptible to changes in conditions. (When it comes to high speed run.)

....For comparison I am running 144x2 (ice are rails challenger track) with 9T drivers and geared 19/39 SBR stage II and I hit about 94 mph on the speedo which i suspect is likely around 87 or 88 mph in reality.

Maybe the snow will be around long enough to dial her in. ;)!
 
I'll mess with it, but I'm also shopping around for another sled.

I was holding off an 800 etec and an 800 assult til about 55-60mph or so likely and then they were pulling away. So the sled is working good down low - I've just got no top end.
 
revster said:
The 2" track is going to be partly responsible for sure. Not only is it more rotating mass but also the resistance moving through the air and carrying snow load. (Depending on conditions) From my experience there is decent jump going from 1.75" to 2" for some reason, like you are crossing some magic barrier.

The other thing is the efficiency of your driveline. The smaller diameter drivers have changed the path of your track takes. It's now turning around a smaller diameter then approaching the front of the rails at a different angle. I'm not going to throw any physics at ya cause I failed that in high school. This is simply what I have been told by older wiser sledders and I have experienced it as well.

All that being said you still seem like you are down more then you should be. Did you make any changes to your clutching when you went to 144 and 8T drivers??

The other factor is conditions. My experience is the big tracks are more susceptible to changes in conditions. (When it comes to high speed run.)

....For comparison I am running 144x2 (ice are rails challenger track) with 9T drivers and geared 19/39 SBR stage II and I hit about 94 mph on the speedo which i suspect is likely around 87 or 88 mph in reality.

Maybe the snow will be around long enough to dial her in. ;)!


Hey Revster

Looks like yer still sleddin.....and still modded out...

I pm'd ya about buyin some stuff if ya part out....

Thnx...enjoy the late season ridin.....weekend looks SWEET around here :Rockon:
 
terez said:
revster said:
The 2" track is going to be partly responsible for sure. Not only is it more rotating mass but also the resistance moving through the air and carrying snow load. (Depending on conditions) From my experience there is decent jump going from 1.75" to 2" for some reason, like you are crossing some magic barrier.

The other thing is the efficiency of your driveline. The smaller diameter drivers have changed the path of your track takes. It's now turning around a smaller diameter then approaching the front of the rails at a different angle. I'm not going to throw any physics at ya cause I failed that in high school. This is simply what I have been told by older wiser sledders and I have experienced it as well.

All that being said you still seem like you are down more then you should be. Did you make any changes to your clutching when you went to 144 and 8T drivers??

The other factor is conditions. My experience is the big tracks are more susceptible to changes in conditions. (When it comes to high speed run.)

....For comparison I am running 144x2 (ice are rails challenger track) with 9T drivers and geared 19/39 SBR stage II and I hit about 94 mph on the speedo which i suspect is likely around 87 or 88 mph in reality.

Maybe the snow will be around long enough to dial her in. ;)!


Hey Revster

Looks like yer still sleddin.....and still modded out...

I pm'd ya about buyin some stuff if ya part out....

Thnx...enjoy the late season ridin.....weekend looks SWEET around here :Rockon:

Yeah I got back to you via PM.
 
What is your gearing?

I am getting 92 mph out of my mtx see 162. Speedo speed. Gps is like 85.

Did you extend the rails from 121 or put xtx rails in?

What clutch weights are you running?

My mtx has 18/40 gearing, 39* helix with white spring and gwg primary spring with super rat weights for flat land.
 
As far as I know everything was stock when I bought it, & I pretty much immediately put the 144 extensions on,(tipped up 144) and now here I am.
 
Have you ver marked your clutches with a marker, and wound it out to see if she is shifting all the way out? Once you get it right on you could always send you cluch o someone like ulmer or muffin to machine your sheave for a few more mph on the top end FYI
 
I haven't. Just looking for suggestions here now. Not sure what I'll have to run on in april, Ice will likely be gone.

I was only getting ~130km to a tank - also gps'd.. It was deep snow and lots of playing generally, but I was beating the 800 etec for mileage.

Expand on this:

loudelectronics said:
You will want to gear down. Gearing is to tall for that track and running low efficiency.

If I'm pulling these gears to 8900 rpm, I can't see how gearing down will help. If anything I think I'm not shifting out on my clutches, and my final drive isn't where it should be.
 


Back
Top