Tire Pressure Traction Tech

J.C.

J.C.

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Apr 18, 2005
Location
Greensboro, NC
If bead seal and ground clearance are not considered, is it possible to run too little air in tires on the typical southeast trails such as Tellico, Callalantee, DPG, URE? Is it possible that greater pressure will result in better traction?
 
To my knowledge, if not considering clearance or bead seal. I have never wanted more pressure on any of those trails.
 
Good question.. With radial car-type tires, I remember seeing a decrease if you went too low, as the middle of the tread would pull up.. But with a Bias, I'm gonna venture and say no?

Though the whole pounds/square inch thing keeps nagging me.
 
I understand what ya mean about the lbs per square inch Rich. Super light, and super wide don't make sense
 
I think you can be too skinny and you can be too wide, where the extreems are would varry for a particular setup/weight etc.. There is a wide middle ground where personal preference lies. I think in very specific situations were the traction is constant a specific tire size can be a benifit.. But as soon as you factor in the dynamics of offroad all that changes and you back to the old tire debates...

Its easy to calculate the best tire on a track for a particular day/race etc.. While a racer will argue the track changes, (it does) I'd say its farily consistant when compared to 4x4 terrain, rocks, dirt, mud, slickrock etc...

Out west where your more apt to see a particular type of rock for length of time, I can see people makeing good cases tire X over tire Y... I think the left coast ppl are slowly seeing that the terrain over here is really NOT the same and does require a different style of wheeling... AKA, more gas at times, but maybe not full on Dan Dibble amounts..
 
In my experience there is definitely a line at the right amount of air pressure. Radial or bias construction is a big part of the equation but tire type/sidewall construction is also a big thing.

With the radials, it seems that 6-8 is about right. 3-4 is too low, although it can work with some bias ply tires.

With the Bias, depends on the type of tire. I have seem 42 TSLs work great with 3-4 and IROKs that need a bit more. I think it more of a trial and error things.

Sidewall height and rim size have alot to do with it. The relationship between the amount of side wall and the amount of rim affects the amount of lateral stability the tire has at any given pressure.

Just my $0.02
 
ahhhh good point Andy. I have seen tires running really low PSI trying to run an angle on the side wall. Where as more PSI would have kept the tread under the rig.
 
zubz said:
Sidewall height and rim size have alot to do with it. The relationship between the amount of side wall and the amount of rim affects the amount of lateral stability the tire has at any given pressure.
Just my $0.02
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upnover said:
ahhhh good point Andy. I have seen tires running really low PSI trying to run an angle on the side wall. Where as more PSI would have kept the tread under the rig.
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I've been pondering this one, too. A lot of people will run rims that are narrower than the facotry recommended rim widths (8" wide rims on 37x12.50's ect...). I assume you just can't go as low with the psi on these setups, or just risk popping the bead? Is there that much more lateral stability with the wider rims?
 
johnski said:
A lot of people will run rims that are narrower than the facotry recommended rim widths (8" wide rims on 37x12.50's ect...). I assume you just can't go as low with the psi on these setups, or just risk popping the bead?
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Actually, exactly the opposite. narrow wheels help keep the bead.
 
i know my tires work better w/ aprox. 8 PSI in the front and about 6 PSI in the rear. I have tired lower...didnt like it.

I have found that when it gets to low the tread folds together and you dont get the bit because the tread voids are almost touching.....

that probably doesnt make since, but it sounds right in my head.

Seth
 
Your air presure and tires size is all dependent on your rig. Unless you have a cookie cutter rig like a TJ that every one has and it is mostly stock then there is really know way for you to get usefull infomation.
I run around 12-15 lbs in my 35's on my j10 and I have not had many traction issues that I think lower pressure would have fixed.
 
Rich said:
Actually, exactly the opposite. narrow wheels help keep the bead.
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Really. That's good to know as I'll be getting new set of wheels soon. But, why do manufacturers recommend a wider rim?
 
John......

Wider rim (up to a point) typically provides a flatter contact patch at the mfr recommended air pressure so that you get the optimum tire wear.

The narrower rims hold the bead better(because there is more friction/force on the beads) at any given pressure over a wider rims at the same pressure because the forces on the bead are less.

Go Yx8 for anything upto a 13.50 wide tire and you should have no problems hitting 8-10 without breaking a bead. You may have to clean them out more often but they will work.

Andy
 
zubz said:
John......
Wider rim (up to a point) typically provides a flatter contact patch at the mfr recommended air pressure so that you get the optimum tire wear.
The narrower rims hold the bead better(because there is more friction/force on the beads) at any given pressure over a wider rims at the same pressure because the forces on the bead are less.
Go Yx8 for anything upto a 13.50 wide tire and you should have no problems hitting 8-10 without breaking a bead. You may have to clean them out more often but they will work.
Andy
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Thanks Andy. Now I feel smarterer.
 
Somebody ask BigWaylon the tire pressure question. You'd think air was in scarce supply if you see his trail pressures.

For my "cookie cutter" TJ with 36x13.50x15 Iroks, I've found about 8lbs in the rear and 9lbs in the front to be optimum. My TJ is heavy, around 4800lbs. Important to remember also that tires often need a "break-in" period before they will flex all the way.

I've only lost a bead once (both right side tires during an awsome assault on a very muddy and rutted hill).



Stewart
 
I run mine at 3lbs front, 4lbs rear. But this is on Boggers. Other tires I am sure I would need more. at empty mine don't bulge much. Tire pressure is defiantly different between type/brand of tire and weight of rig
 
CYJKrawler said:
Shees, now he's an educator too on top of all his other attributes:) Henceforth refered to as Doctor RockShop or affectionately as Doc Rock.
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It is funny actually, John's Dad was my trainer for my old engineering job when I lived up in Binghamton, NY. He worked at our training center running the training classes for the customers and staff members on the equipment we manufactured. John came in for us to do his cage and we chatted a little bit........it is definitely a small world......
 
Another "cookie cutter" TJ checking in. I am running 6PSI on all 4 corners and it seems to work well for me. 35x12.5 TrXuS MTs on 15x8 wheels with Staun Beadlocks from Doc Rock.
 
Andy,
You never said Binghamton before. I used to travel up there in the 96-98 time frame for meetings at Loral (I think. Maybe later bought out by Lockheed Martin?). My impressions of Binghamton: COLD. Great little mom & pop informal Italian place right downtown though.

Stewart
 
Yup, "lived" there for 2 years after college. I was on the road 75-100% and that was our home office. I didn't spend a ton of time there but I did have an apartment just outside the city.....

Andy
 
stewartgivens said:
Somebody ask BigWaylon the tire pressure question. You'd think air was in scarce supply if you see his trail pressures.

For my "cookie cutter" TJ with 36x13.50x15 Iroks, I've found about 8lbs in the rear and 9lbs in the front to be optimum. My TJ is heavy, around 4800lbs. Important to remember also that tires often need a "break-in" period before they will flex all the way.

I've only lost a bead once (both right side tires during an awsome assault on a very muddy and rutted hill).

Stewart
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yeah...it's not in scarce supply...they just don't give me CO2 for free...:D

actually, the last time or two, I haven't gone down quite as far...I think I'm gonna stay in the ~6PSI range, not the 3 (or less) I've been running...

Greg
 
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