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W I D E R I S B E T T E R . or is it?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by CooknwithGas, Apr 24, 2002.

  1. CooknwithGas

    CooknwithGas 1/2 ton status

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    RIMS -

    Need to make a decision on rock crawler rims - will be buying in a few days.

    Should I get 15 X 10 or narrower say 15 X 8 or 9? I want 33" tires to be flush with the body (not tucked up under the fenders).

    Anybody have experience with this. The truck will be used for mostly road, but some off-road activity. When I order the Rock Crawlers (probably mail order from a 4X4 magazing). Should I specify a backspacing since I want them to be flush with the body? What backspacing is best?

    W I D E R OR NOT SO WIDE. Any suggestions?

    Scott.
     
  2. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    the 8 inchers will keep the valve stem tucked in further from trail damage
     
  3. BurbinOR

    BurbinOR 3/4 ton status

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    I run 16x10 rims with 36x12.5.16 SSR's and after our PNWFS4x4 first run was wishing I had gone with 8" wide rims - the rock rash I got may NOT have been avoidable but it seems it would have been less.
     
  4. fourwheelerjeff

    fourwheelerjeff 1/2 ton status Staff Member Moderator

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    hey blazzinOR, that's good for me to hear, i am thinking or running two different rigs with 36's and already bought a set of 8's (thank's laketex) but was wondering if i should have went with 10 on the 36's, now i know
     
  5. marv_springer

    marv_springer 1/2 ton status

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    I run 15x8's with minimum backspacing (read: stick out as wide as possible. Can get them custom made thru US Wheel.

    Since they make the track wider, they minimize the interference on the rear tire at the top on the inside with the fenderwell during full stuff. Also, as mentioned before, the valve stem can be set way in there - keeping it away from damage.

    Marv
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Well the narrower rim is better at keeping the bead seated at low pressure and protecting the rim.
    The down side is on the street. The tire will be more stable on a rim closer to the width of the tire. 12.5 inch tire should be on a 10 inch wide rim according to the manufacture. I'm running 35x12.5's on 10 inch wide rims and it handles better on the street than it did with a 33x12.5 on a 8 inch rim.
    You need to decide the trade off your willing to make.
    Now the deepest offset you can get on the truck stock is going to be 4 inches. That's about 1/2 inch more than stock rims. The front will stick out a good 2 inches. The rear will be close to flush. With the tread.
    Now My thought on the tires sticking out. I wheel a lot and the trails I get on are often dug or deep V ruts. I have trashed both sides of my truck because the body hit before the tires did. I wanted the tires out a couple of inches to try to save my sheetmetal.
    On the front if you were to look at the steering gemoetry the taller the tire the more you want the tire to stick out.............
    Ok now a bunch of folks are going no that's not right...it's harder on the ball joints and bearings.......Not true.....
    If you were to look at the angle that the knuckle turns on and draw a line through it till it intersected the point were the tread meets the pavement that's the pivot point that the tire would turn on. It's called several things including "King Pin Inclination" In a perfect world that would be dead center the tread. Even stock it isn't perfect because of other factors like Castor angles and camber angles.
    The larger the tire the more that intersection point moves away from the center of the vehicle. Offsetting the tire out gets you closer to the point where it was. The end result is it handles more like it was originaly designed to handle.
    The other thought is the wider you make the stance when going to larger tires the more stable the vehicle will be to help compisate for lift rasing the center of gravity.
    There is a couple pictures of my beat up old truck on rock crawlers and 35's in my CK5 photo album. It was a recent change so only a couple shots up right now. Link is in sig.
     
  7. CooknwithGas

    CooknwithGas 1/2 ton status

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    OK. You talked me into the 10" wide wheels.

    Thanks for the photos, Grim. The bigger tires look great! I don't think 35's would fit under my 2.5" lift unfortunately, so I might just go with 33's from Wal-Mart.

    I'm still not sure of the backspacing though. What was the backspacing on your used Rock Crawlers?
     
  8. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    35's will fit. just need a bit of trimming.
    grant
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    I'm running 4 inch backspacing. Works out pretty good.
    For the record with some more minor modifications you could clear 35's To be honest my springs are really 2.5 inch rancho's/ Measuring the total lift against my wifes bone stock 79 they were 3.75 inches of lift. The way I cleared the 35's was I used some ORD zero rate add a leafes and moved the front axle forward and inch. They also gave me a total of 4.75 inches of lift on the front. I put a set in the rear to even it up and once I get some cash I'll be lengthening my drive shaft and moving the rear axle back one inch. I also put on a 1 inch ORD body lift. My first wheeling trip was last weekend. I ran the sway bar because I have not had a chance to ramp the truck since I did the mods. I didn't scrub a single time. Hope to have it on a ramp this week so I can check it with the sway off. My fenders are only timmed back to the inner fender.
    One other thing...some brands of tires are not true to the listed size. I'm running the new KM BFG and unloaded they are EXACTLY 35 inches tall. Swampers are the only other brand I know for sure that are right on their listed size.
    Total cost for the above stuff was I think $40 per set of Zero rates. $90 for the one inch body lift and I had to get a new set of U-Bolts.
     
  10. MOABDADC22

    MOABDADC22 1/2 ton status

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    Grim hit the nail on the head........Botta Bing....Botta Boom.
     
  11. MudbogAD

    MudbogAD 1/2 ton status

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    15 x 10's look much better than the 8's, IMO. Besides, what if you decide to go with bigger tires in the future? The 8's won't cut it.
     
  12. wayne

    wayne 3/4 ton status

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    Grim, Swampers are not the advertized size. They advertize my 35x14.50x15's at about 35.2". Mine mounted on 15x10" wheels are just under 34" inflated to 35psi and mounted on the truck. Also there was a post on POR that showed SX's in 38x12.50 and 38.5x14.50 and they were not mounted and were not close to the advertized spec.
     

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