Result: Great Looking Wheels

Discussion in 'Lifted & Offroad Suspension' started by unruly, Feb 24, 2011.

  1. unruly

    unruly New Member


    I have a stock suspension '89 C1500 2WD with OEM 15" rallys...does anyone know (for sure) the OEM wheel width, 6", 7"?

    I found the aftermarket wheels I want. I plan to use 2" drop shakles on the rear to almost level it with the front, slight rake. I think deeper dish rim on the rear is appropriate. How do I calculate (guestimate) the tire/wheel dimensions to get a consistent look front to rear, you know, filling out the wheel wells evenly? Wheel manuf. site says 6" rim on the front with factory size 235-75-15 (tread width 6-5/8) will result in same overall height as a 10" rim, if I go with 255-70-15 (tread width 7-5/8). Also, I can get within less than 1/2" overall height, if I go with a 275-70-16 on an 8 1/2" rim (tread width 8-1/8), getting better. Or, I can get spot on same overall height as the front with some "less than streetable" M/T or Hoosier 29-12.50-15 (10" tread width) on a 10" rim. I like 10" of tread width. My speedo would be really close with any of these scenarios. Does anyone have any experience with these calculations, making it look right in the process? Thanks for any help provided.
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Welcome to the GM truck club. Unless you bought your '89 new, the only way you can be sure of your wheel width is to measure them. It's easy. They could have been swapped out 4 or 5 times in 22 years. The wheels that came on my '88 looked stock, but were 7" inch Ford wheels lol, yep Ford wheels. Same bolt pattern & spacing for the Chevy C-3500 2wd 8 lugs as the Fords through those years.
    Last edited: Feb 24, 2011
  3. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Welcome to the club.
  4. unruly

    unruly New Member

    ---------- Post added at 11:05 AM ---------- Previous post was at 11:04 AM ----------

    Do you mod here?
    Last edited: Feb 24, 2011
  5. unruly

    unruly New Member

    ---------- Post added at 08:55 PM ---------- Previous post was at 08:53 PM ----------

    ---------- Post added at 08:56 PM ---------- Previous post was at 08:55 PM ----------

    Bought it from the original owner with 99% of documentation included with purchase. Do you have any skill or knowledge that will help?
  6. stephan

    stephan Rockstar 4 Years 5000 Posts

    I probably can't be of help for your situation, because I don't like the raked look, so I leveled mine (raised it 3" in the front to achieve level). You said you didn't want to level yours so your fitment will be different than mine. I can fit 33" X 12 1/2" on 8 3/4" inch wide wheels with 4 1/2" backspacing.

    The sizes that you state are metric. Unless you have a metric tape measure, you need to convert them to inches & then take a tape & see if they will physically fit on your '89.

    255-70-15 This metric tire size that you state means the tire is 255 mm wide at the cross section, aka the bulge (not the tread) the 70 is the aspect ratio, meaning the tire sidewall is 70% as high as it is wide from the ground to the bead, & of course the 15 is the wheel dia. You won't have any trouble fitting these on the back, but a 255 is going to be close to rubbing on the front with 22 year old coil springs that have sacked out. I had 255s' on mine & before I lifted it & put in new springs (at 100K miles) mine occasionally rubbed.

    As far as getting a "consistant look" from the front to rear & filling the wheel wells equally... I don't think you will be able to do this unless you use different size tires front & rear because you aren't planning on leveling it. With the shorter wheel well height in the front, tires of the same size front & rear will always fill the front wells "fuller" than the back.
    Last edited: Feb 25, 2011
  7. Lil_Red_Chevy

    Lil_Red_Chevy Rockstar

    I have a stock suspension '89 C1500 2WD with OEM 15" rallys...does anyone know (for sure) the OEM wheel width, 6", 7"?

    My suggestion, if you haven't already, go talk to a tire shop. There is usually someone there that can answer these detailed questions about your specific model without you having to buy anything.
  8. unruly

    unruly New Member


    Good point about just measuring it...I have very little experience with aftermarket wheels yet. My vehicles only had one chance to be all original...but I'm ready to change a few things now. without breaking the good looks. I planned on leaving the front alone and reducing the rake by dropping the rear by 2", but do exactly as you say, use different sizes front to rear. The springs were replaced with OEM and adjustable A-arm cams installed by the original owner in '02. Knowing this is a perk of having the docs. Since it will be factory on the front, I will use aftermarket wheels and tires with factory dimension there, then all I will need to do is design the rear to fulfill my original question. I just have no idea how much of an effect will be yielded by each wheel width increment and tire dimension change on the rear. I get the general idea of a narrow wheel heightening the tire and changing the cross-section, but I need to find someone who knows just how much. Trial and error won't suffice...could be a very expensive mistake.

    ---------- Post added at 10:28 PM ---------- Previous post was at 10:21 PM ----------


    I agree, but most shops in my area only know how to air wrench the wheel off, break it down, re-mount, balance and air wrench it back on. I asked a Goodyear authorized shop to look in the door and put the factory recommended pressures on my newly purchased factory spec tires and it almost brought the shop to a stand still with such a great opportunity to ridicule a customer. I got home and found 35 in each tire...the ride quality felt like sh!* the whole way there...then after adjusting to factory pressures, it felt like a Caddy again out on the highway. I need to locate a custom wheel shop and get them to help me estimate...thanks all

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