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Air Pressure, How Low?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by kpanza, Jan 2, 2001.

  1. kpanza

    kpanza 1/2 ton status

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    Just wanted to check with the rest of you guys who run tires and wheels of the 16.5"x9.75" variety. I just switched from the 15s of my old 10 bolts to the 16.5s of my 14 bolt and 3/4 ton front axles and was wondering how low you can go before you will peel a tire off because of the lack of a safety bead? I used to go down to 10 psi and never had a problem with the 15s. I was out wheeling this weekend, and I dropped the pressure down to 30 psi, but they were just way too hard for good traction. I am running 35x12.50 BFG Muds on the 16.5" wheels. Thanks for the help.
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I run my 35 x 12.5 x 16.5's on the factory steel 6.75" rims. I haven't peeled a tire off yet. I have gone down as low as 18 psi on the trail. On the street I run them at 30 or so.

    I just scored a set of near new 15 x 10's with the 8 bolt pattern so I'll be able to air down a lot better with my next set of tires.[​IMG]

    Rene

    [​IMG]
     
  3. ken

    ken 1/2 ton status

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    I run my 16.5" rim Swampers down to 10 PSI in the sand...course I don't turn too fast at speed in the sand, so as to try to peel em off!!

    ken
     
  4. HarryH3

    HarryH3 1 ton status Author

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    I've got 35x12.50x16.5 BFG Mud-Terrain's mounted on rims the same size as yours. On the rocks of Colorado, at 18 PSI two of them peeled right off the rim. I actually drove right out of one of them! [​IMG] BFG told me not to run them below 26 PSI if I wanted them to stay on the bead.

    A tire with a stiffer sidewall, like the super swampers, can probably get away with a bit less pressure.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A><P ID="edit"><FONT SIZE=-1>Edited by HarryH3 on 01/02/01 11:07 AM (server time).</FONT></P>
     
  5. kpanza

    kpanza 1/2 ton status

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    Thanks. I guess I will stay above 25 psi then! I guess it is time to look into some beadlocks!
     
  6. pcorssmit

    pcorssmit 1/2 ton status

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    Good luck finding beadlocks for 16.5's, I don't know of anyone who makes them. I guess my advice would be to go back to a 15" rim with beadlocks. I run my Swampers with around 6-7 psi on 15x10 bead locks. With my old 35's (street tires) I run around 10-12 psi on 15x10's, without beadlocks (off road). I've never lost a bead. As for running swampers without beadlocks, I don't think it will solve the problem. At least in the 15" size, they are more prone to comming off the rim than BFG's. The sidewalls are much stiffer, requiring lower air pressure, resulting in losing the bead more often.

    Pete

    '83 K5, 350 TBI (ex 6.2), Dana 60/14 bolt, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  7. kpanza

    kpanza 1/2 ton status

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    I had to go to bigger rims because the brakes would not clearance with the 15s...I will look around for beadlocks, I am pretty sure that a friend of a friend once had them on his full size Ford with 16.5s...I'll let you know if I find them! For now I will just keep the psi around 25...
     
  8. pcorssmit

    pcorssmit 1/2 ton status

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    Are you running the stock Chevy 3/4 ton brakes? If so, 15's will fit the rear fine and the front with a little grinding. I've done this on 3-4 front ends, 10 bolts and 44's. Dana 60's require a lot more work, but it can be done. I run 15's on my front 60 and rear disk brake 14 bolt, and I also have a buddy with the same axles under a '93 long box Chevy with 15's.

    Pete

    '83 K5, 350 TBI (ex 6.2), Dana 60/14 bolt, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  9. Blue85

    Blue85 Troll Premium Member

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    You "dropped the pressure down to 30 psi"? How high do you usually run it? I run 28-30 psi on the highway.

    I ran 33/12.5/16.5 on 16.5x9.75 at 12psi in the sand this summer and it worked out pretty good (Silver Lake, MI rocks!). It basically works better the lower you go, but I'm afraid to run any lower than that on 16.5's. Now steering into rocks, they probably would have peeled off.

    "Big? No, these tires might be big for your Jeep, but they're just temporary for my K-5" [​IMG]
     
  10. kpanza

    kpanza 1/2 ton status

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    When I put the 15" wheels up to my brakes, I would have had to grind off a lot more than I thought was safe! I'm talking more than a 1/4" of caliper and backing plate...so i went with the 16.5" because they have way more tire choices than the 16s...oh well, I will live with the not so low pressures, plus the big wheels look so much better than the little 15s! And this way I can someday swap in really nice disc brakes all around and not have to worry about anything..
     
  11. ken

    ken 1/2 ton status

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    AMEN!!

    And at least you didn't cry about losing your 6 lug wheels when you went to 8 luggers!!! Hehehehehe!!!!! ;)

    ken
     
  12. pcorssmit

    pcorssmit 1/2 ton status

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    I guess it depends on which brand of wheels you use.
    The four wheel disk brakes are a great thing to have, my rear drums never worked all that well.
    I'd still be interested to know if you find 16.5 beadlocks.

    Pete

    '83 K5, 350 TBI (ex 6.2), Dana 60/14 bolt, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  13. reddog64

    reddog64 1/2 ton status

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    my 35x12.5x15r BFG at's run at 6psi in the snow just fine... but Hey i live dangerously... I tried 10 and it was fine to...
    But be careful and carry some either for re seating the bead!!!

    Um... yes officer I know it's too big...
     

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