4x4 / Off-Road TechThis section contains all discussion related to taking the FJ Cruiser in Off-Road situations, 4x4 applications and any armor modifications.
I remember reading how the FJ Trail Team with their skids has their A/C on FULL and still feel hot inside the cab....
Also, the stock skids address 'venting' the front diff...wonder if the aftermarket skids deal with that....
There must be a reason Toyota engineered their stock skids to re-route airflow directly toward the front diff.
Just a reminder on the heat buildup question: Hot air RISES!
Putting something under a hot item does not affect that. Restricting airflow under it CAN affect it tho. The FJ Trail Team's full skid does not allow as much air to flow over it. BUT remember, when crawling or slow trail running, air flow is minimal, therefore the floors get warm. Skids on, off, makes little difference.
I have big skids on my Tacoma and had them on my old 4Runner and the regular ( non- High temp) paint was not ever even discolored, much less blistered or burned. All due to that hot air rising thing. Of course, everything under there gets hot, but not to the point of becoming an issue.
And as for venting the front diff, power steering, etc. that is what the slots are for.
( just a note: there are 7 slots in a Jeep grille. 14 on an FJ skid. Twice as good?!?!?!
The deflector/support on the inside helps redirect toward the diff.
Also, the skids are not as wide as the frame, so there is LOTS of room for airflow and heat shedding.
Q: Does anybody have experience with the UHMW plastic skids discussed over on IH8MUD?
It looks like a continuous plate could be run from bumper to gas tank, out of a single sheet. Yep a secondary cross-member would be in the plan, to support in front of the tank. It's got to be way lighter than steel, and is supposedly tough stuff.
Q: Does anybody have experience with the UHMW plastic skids discussed over on IH8MUD?
It looks like a continuous plate could be run from bumper to gas tank, out of a single sheet. Yep a secondary cross-member would be in the plan, to support in front of the tank. It's got to be way lighter than steel, and is supposedly tough stuff.
Yep, that's what I was looking at. Some threads say use "UMHW", some say "HPDE". McMasterCarr has some decent property description sheets on their site.
The thing I didn't get was, both Joel and 03FourRunner said this stuff is great, but they'd go with steel once it's available. Just doesn't make sense, unless it's a cosmetics or oil-change-convenience issue. The low weight is a compelling reason to try this solution. I'm willing to drill oil drain holes in the sheet, and use heat to get curved edges and a better fit. I was just hoping for more info from folks with direct usage knowledge before I take the plunge.
This is just my $0.20. people.
I have extensive experience using both materials, steel and Ultra High Molecular Weight Polyethylene (UHMWPE).
Here are a few quick comparrisons for your thoughts.
Steel
Advantages: high impact resistance, high abrasion resistance.
Steel
Disadvantages:
Heavy, limited wear life in highly abrasive conditions, subject to corrosion, high coeficient of Friction, higher shock transmission.
UHMWPE
Advantages:
1. It has a coefficient of friction 50% that of steel.
2.It is very lightweight, with a density of 0.95 g/cm3, as apposed to steel, which is 7.8 g/cm3.
3.The abrasive resistance of the UHMWPE material is up to two times greater than that of steel.
Disadvantages:
1.UHMWPE has a coefficient of thermal expansion ten times greater than steel. (Which means you better bolt it down well.)
2.UHMWPE is naturally combustible.
3.UHMWPE is slightly more expencive than steel.
The wear mechanism we are targeting here when using UHMWPE materials as a skid plate is gouging and scratching. UHMWPE materials are prone to gouging and scratching.
Large rocks can tear the material.
Impact resistance is best near a 90o
angle of attack.
Suitable only to 80-100oC temp.
Very good under high and moderate stress, if moderate impact.
This is just my $0.20. people.
I have extensive experience using both materials, steel and Ultra High Molecular Weight Polyethylene (UHMWPE).
Here are a few quick comparrisons for your thoughts.
Steel
Advantages: high impact resistance, high abrasion resistance.
Steel
Disadvantages:
Heavy, limited wear life in highly abrasive conditions, subject to corrosion, high coeficient of Friction, higher shock transmission.
UHMWPE
Advantages:
1. It has a coefficient of friction 50% that of steel.
2.It is very lightweight, with a density of 0.95 g/cm3, as apposed to steel, which is 7.8 g/cm3.
3.The abrasive resistance of the UHMWPE material is up to two times greater than that of steel.
Disadvantages:
1.UHMWPE has a coefficient of thermal expansion ten times greater than steel. (Which means you better bolt it down well.)
2.UHMWPE is naturally combustible.
3.UHMWPE is slightly more expencive than steel.
The wear mechanism we are targeting here when using UHMWPE materials as a skid plate is gouging and scratching. UHMWPE materials are prone to gouging and scratching.
Large rocks can tear the material.
Impact resistance is best near a 90o
angle of attack.
Suitable only to 80-100oC temp.
Very good under high and moderate stress, if moderate impact.
UHMWPE is not suitable under gouging abrasion.
Well I was going to post an answer, but now it just seems pointless. Nice response.
The reason they want to upgrade is that steel takes a HIT better. It won't flex like hdpe. They also tend to wheel REALLY hard. Given the cost and the weight, I'd still give hdpe a chance if I were you.
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