Tunnel Clearance ????

[SixtySevenGT]

What is acceptable tunnel clearance ? I recently put a 2.25 x 159 on and now my clearance is about 1/4 of an inch.

I think this is really slowing things down. I had my Track ported at Wilderness in New Plymouth this really helped. I might roll my chain case or just sell the sled. 02' 800 edge built pretty good.

 

[NoSecondChances]

What is acceptable tunnel clearance ? I recently put a 2.25 x 159 on and now my clearance is about 1/4 of an inch.

I think this is really slowing things down. I had my Track ported at Wilderness in New Plymouth this really helped. I might roll my chain case or just sell the sled. 02' 800 edge built pretty good.

1/4 inch is not enough IMO. I prefer at least 1" bare minimum.

 

[longhairfreak]

What clearance r u talking about? The top of the tunnel or the front of the bulkhead.

 

[winter brew]

If it's not rubbing it is good. IMO the minimum clearnce that doesn't rub is ideal, any more just builds up ice, adds weight and the track just "trims" the ice so you end up with minimal clearance anyway.

 

[Eli]

I had a huge roll on my last sled 3+ inches of clearance with a powdercoated tunnel. I did not experience significant ice accumulation.

 

[05snopro440]

What is acceptable tunnel clearance ? I recently put a 2.25 x 159 on and now my clearance is about 1/4 of an inch.

I think this is really slowing things down. I had my Track ported at Wilderness in New Plymouth this really helped. I might roll my chain case or just sell the sled. 02' 800 edge built pretty good.

I know exactly what you mean. The track is clearing everything but something seems to be slowing it down. This is because the air resistance between the track and the cooler actually slows the track down. The spinning track has to push the air out of the way, so the track is slowed because of this. If the guys on here don't believe me I have seen it before. Increasing you clearance will get rid of this problem, however you want to do it. I don't know what is acceptable, I would compare to a stock sled and try and get a similar clearance to that.

 

[Eli]

My sled with mega clearance was less affected by deep deep snow. It seemed less tempermental to changing snow conditions. My personal guestimate is you need around an inch for mod-type sled.

 

[NoSecondChances]

What track was on the sled before? If you had a 140 ish or 151, going to the taller track and longer will slow you down, not the air pressure in the tunnel since your track is ported, there should be minimal air pressure. You might be forcing snow through there and it is hanging up and causing friction with only 1/4" of clearance would be my guess.

 

[amery3]

If it isn't rubbing, you're fine, as an extra measure of protection, I live by the rule of thumb...if you can force your thumb in between the track and the tunnel, you're fine, that accounts for the track riding up on drivers at high speed, hitting stuff and causing the track to bounce, etc, 1/4" is plenty IMH, that's all I have on my MC with unclipped lugs, and it almost never hits.

 

[SixtySevenGT]

Thanks for the Input

I still think the air pressure is the problem. I think about 1" would be good. I will most likely roll the case and keep the sled. I want a D8 but will keep the old one for spare.

 

[mountainhorse]

In order to run a taller track you not only have to maintain the lug tip clearance, but you have to increase it (on stock tunnel/skid/drive). Simply put, a taller lug will move more snow. The more snow you have to move out the front of any given tunnel-opening, the more parasitic loss you will have ( “pumping-loss”).

To illustrate this, look at any action pic, in the pow, where someone is on a "wheelie" for whatever reason... you will see gobs of snow spraying out the front of the tunnel. The tighter the opening is, the more power it takes to push the snow past the restriction (the opening at the front of the tunnel at the bulkhead)...

Getting a track to fit, and having it run well are not necessarily the same thing. If it comes close to rubbing, IMO as well as Mark Holz, Mike Vanamburg and others) it has no place on a properly set up deep-snow sled.

Snowest had a great article about lug tip clearance a couple of years back... 1" or so being ideal.

If you are worried about ice buildup at the mouth of the tunnel/bulkhead... install a thin 1/16" thick piece of UHMW plastic the full width of the tunnel from the cooler down to the opening... if you only have a rear cooler... run this piece of plastic all the way back to the cooler... you will have no issues with ice buildup.

 

[mountainhorse]

Also,

People riding in light champaign powder will have a whole lot easier time getting thru the snow with little clearance than wet heavy pow... like we get on the west coast.

 

[boone]

I had the same problem on my sled with my 16 X 2.5. My case was already rolled so I went to the next size smaller drivers on my driveshaft and re-geared to compensate. I now have 3/4" clearence.

 

[Interceptor]

Why does a vacuum cleaner 'rev up' when you put your hand over the end of the hose and block airflow?

 

[mountainhorse]

Why does a vacuum cleaner 'rev up' when you put your hand over the end of the hose and block airflow?

Because you are asking it to move less air... vacuum cleaners are centri***al blowers, If it does not have to move air it does not have to work as hard... Kinda like running on the hardpack as compared to deep snow.

Why does your shop vac bog down when you put your hand over the outlet and block off airflow out of the exhaust?

Because you are choking off the outlet and the blower inside the vac is still trying to pump the air out and is loaded up.... Kind of like having a restriction in the front of the tunnel... the bigger the track (longer and taller lugs) the more snow you move... the more snow you move, the proportionally bigger the clearance needs to be.

As a random example... using random clearance numbers....If a 2.0" track needs 3/4" clearance, a 2.5" track of the same design would need more than 3/4" clearance... for optimum

 

[mountainhorse]

Hey moderators.... Centri***al is not a cuss word, fix that auto edit feature.

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[NoSecondChances]

Not sure if you guys noticed but he said his track was ported, air movement won't be as big a deal. I like at least 1" of clearance simply to clear the snow and if you ever ride on dirt (even for 100 ft) there is a chance that you can kick a rock up in the tunnel. Snow will push through the tunnel, rocks tend to put big holes in thin aluminum coolers. Moving extra air is just an added benefit to the clearance for rocks and big ice chunks.