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  #21  
Unread 12-30-2015, 08:49 AM
RF2200 RF2200 is online now
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Manchester, you will probably be best served by modifying your driving technique and you should see substantial improvement. Use a higher gear than “low”. The higher gear ratio will reduce torque and help reduce wheelspin. Drive straight up, and steer for traction if momentum wanes. Steering for traction is when you make quick 1/4 turns left and right repeatedly until traction is gained. If you fail the ascent then fully apply the brakes, engage reverse, and back straight down. Left foot braking should substantially decrease wheelspin and help you maintain forward momentum. Left foot braking is pressing your left foot on the brake and your right foot on the throttle simultaneously. Traction control only kicks in after your tires have lost traction (reactive). Left foot braking helps your tires maintain traction and not spin in the first place (proactive) and helps regain forward momentum after your tires have lost traction (reactive) by helping to equalize speed to each wheel and allow more torque to be sent to the wheel with more traction. Left foot braking will also keep your brake rotors clean and dry. If this doesn't get you where you need to go then use chains, then add taller tires, then add lockers.

https://youtu.be/L85t5WLCK84

People also get confused about traction in winter conditions and what to do with your tires. On ice, hard packed snow, and a small amount of snow on top of ice or hard packed snow you want a tire with the least rolling resistance and smallest contact area possible which results in a higher pressure per unit area between your tire and the road surface (tall, narrow, and fully inflated). When you are on snow surfaces where you are not "finding the bottom" such as deep snow or driving on a glacier you want a tire with the least rolling resistance and the largest contact area possible which results in a lower pressure per unit area between your tire and the road surface (tall, wide, and aired down).
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Last edited by RF2200; 12-30-2015 at 09:22 AM.
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  #22  
Unread 12-30-2015, 09:46 AM
RF2200 RF2200 is online now
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Forgot to discuss siping which people are also generally confused about.

Tires make traction in multiple ways, mechanical grip is one of these ways which causes the edges of the tread that grab the irregularities in the road surface like teeth and propel the vehicle forward. The more grooves or sipes in the tire, the more mechanical grip you will have. Circumference grooves will enhance side bite. Lateral grooves will enhance forward bite.

Sipes do not increase surface area of your tire.

Adding sipes to the tire laterally will increase mechanical grip and cause the rubber molecules to rub against each other. This will increase the operating temperature of the tire. Sipes around the circumference of the tire will open up at speed and provide airflow between the blocks of rubber. This will provide some heat retention at low speed but cool the tire at high speeds. Grooving provides air flow between the tread blocks and make the tire run cooler across the board.

So, siping increases mechanical grip, increases tire operating temperature, and is generally beneficial in all types of winter tires.

https://www.youtube.com/watch?v=3Tc3VIDQvh0
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Land Rover 110
Unimog U1200
Husqvarna TR650 Terra Touratech

Last edited by RF2200; 12-30-2015 at 02:56 PM.
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  #23  
Unread 12-30-2015, 09:56 AM
Wapitihunter Wapitihunter is offline
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Quote:
Originally Posted by RF2200 View Post
and fully inflated
I agree 100% with everything you said except this, unless you mean a full contact patch. Grease monkeys pumped my tires up to max side wall pressure, reduced surface area, and my subaru w/ blizzaks was like driving with bald tires. Air down to 'fully' inflated or lower than fully inflated and friction vs. surface area trumps pressure for stopping and going on ice. IMHO, stayed at a holiday inn express again last night. I think you do better getting moving on ice by airing down - I challenge you to a dual!
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  #24  
Unread 12-30-2015, 11:46 AM
RF2200 RF2200 is online now
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Haha. Ok. A duel it is. Facts vs feelings.

I said fully inflated, not over inflated. You don't want a bulging tire. I think we know all know that when you put 35" tires with a stiff carcass on a JK you are not running them at 70 psi or whatever the max pressure is. You are going to run them at around 30 psi. That is fully inflated - when you have an even contact patch laterally and no less or more. Under inflated or "aired down" generally will not help you on icy roads.

You do better moving on ice with the right tires with the right tread compound and the right mechanical grip enhancements (siping, studs, chains). Mechanical grip trumps adhesion on ice. Siping, studs, and chains will trump even the softest stickiest rubber compound on ice. So, if airing down puts more sipes, studs, and/or chain in contact with the ice then traction may be enhanced to a limited extent, but there are many other disbenefits that outweigh the potential enhancements. Look at what ice racers use on ice and replicate that on your truck if you want ice traction, but that is not practical and would be poor in snow. Manchester asked specifically about a loose snow covered road/driveway that was being traversed with a 4x4 Ram 2500 Cummins with open differentials on 285/75R17 Toyo R/T II tires.

Hypothetically, even if Manchester did increase traction in his tires by airing the tires down he would increase rolling resistance by an even greater amount resulting in a net loss. There are many different variables involved here beyond strictly traction. Furthermore, friction is independent of contact area. Said another way, friction does not depend on the amount of surface area in contact between two objects, the tires and ground in this instance. The amount of friction force depends on two things, the coefficient of friction and the mass of the object you are trying to move. Since the coefficient of friction is constant the only thing really determining the amount of friction force is the mass of the object you are trying to move, a truck in this instance. No matter how much you air down your tires you are not going change the mass of the truck, other than the slight mass of the air that you let out of the tires.

You can do this experiment at home. Take a brick and set it on a table largest surface area side down. Take a force gauge and pull on the brick until static friction is broken. Note measurement. Now take the brick and set it on end with the smallest surface area down. Then pull with force gauge until static friction is broken. Note measurement.

They will be the same. Friction is independent of contact surface area.
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Last edited by RF2200; 12-30-2015 at 01:36 PM.
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  #25  
Unread 12-30-2015, 01:42 PM
Wapitihunter Wapitihunter is offline
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Quote:
Originally Posted by RF2200 View Post

They will be the same. Friction is independent of contact surface area.
As a former fellow student of statics and dynamics I agree 100%, bad choice of words, thats why I went chemical not mechanical at my last stay in the holiday inn express.

I still think I could beat you in an up hill drag race if we had the same tires and mine were lower than typical street pressure. I think I would stop faster too. This sounds like a fun experiment (roads are total ice here too, perfect).

edit: if nothing else than because the pressure that ram recommends on the tires (or any truck tire) is for max or light loads. If you have no load or very light load, the tire pressure is infact wrong for the load, which is why I think tires wear so fast and the ride is so bad at 60psi/40psi. eh? I get that once you have the idea contact area for a flat road, then that is it, and that will correspond to a pressure for that tire - but i'm saying the pressure he is running is too high, you don't agree his pressure is to high?
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Last edited by Wapitihunter; 12-30-2015 at 01:50 PM.
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  #26  
Unread 12-30-2015, 02:09 PM
RF2200 RF2200 is online now
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Agreed that the manufacturer's recommended pressure is too high for an unladen truck. Blame Ford Explorer/Firestone debacle years back.

This is a question of optimization more than anything. Tractive force vs rolling resistance vs tire deformation vs safety vs clearance under differentials vs etc.
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Last edited by RF2200; 12-30-2015 at 04:14 PM.
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  #27  
Unread 12-31-2015, 07:42 AM
PeteEinMT PeteEinMT is offline
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I am running my siped R/T's at 48 in the front and 44 in the rear on a 2500 Mega Cab. Considering the roads and passes I have done I am pleased. I am also running stock 3.42 gearing so I am sure the fact that I tend to lug it a little doesn't hurt. I also have limited slip. I will be changing to 4.10's and ARB lockers this spring. Hoping the AEV switch panel is out soon

Pete

I'll take my truck any day of the week over my JKU in bad weather
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  #28  
Unread 12-31-2015, 09:26 AM
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Manchester Manchester is offline
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Why the change to ARB over the LSD?
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  #29  
Unread 12-31-2015, 10:14 AM
PeteEinMT PeteEinMT is offline
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For the select ability aspect and getting the front locker out of it. I do feel with LSD you get some tire wear due to that so would rather have open for the majority of the year

Pete
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  #30  
Unread 12-31-2015, 10:43 AM
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Anyone have input on the ARB vs the electric lockers like used in the Power Wagon?

Don't know if applies to the Ram version but heard some reliability complaints about electric lockers in general. Think they may offer some install ease over the ARB (at least no compressor).
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