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    Results 1 to 9 of 9
    1. #1
      Join Date
      Feb 2019
      Posts
      218

      Negative offset wheels?

      I hope this is where to put this question.

      I have been reading, studying and going back and forth for a few weeks now. I am in a situation, and dont really know how to solve it.

      I am building Isaacs truck (see signature) and the wheel situation is driving me nuts. I installed an IFS, that is a mustang 2 style with a manual R&P, so its an a-arm type suspension. The frame on the 67 is basically straight, so the rails dont turn in, they are straight, making the stance wide. To run my current wheel setup, I am using 1-1/2" spacers in front, and 2" in the rear so it is slightly wider. The wheels are factory chrome clad 20" x 8" with a 24mm offset, from my charger R/T. The problem I am trying to solve is the offset. I want to run hellcat replicas, which would be 20x9 in front (20x11 rear), but the 8" wide wheels are close to rubbing now, with 1-1/2" spacers. The hellcat wheels have a 25.5mm offset, but being an inch wider, they would be even closer to the frame.

      I would like to eliminate the spacers, but I would need to make up the difference somehow. I could run a custom wheel, with a -24mm offset, but they would not be hellcat replicas. Im sure there are negative side effects to running a very aggressive negative offset wheel, but Im not sure if these wheels would fit that category. But you all know custom forged wheels are pricey too. So it would be almost $1000 a wheel.

      The other options are #1- get custom A-arms made which would be about 3-4" longer, allowing me to run the +25.5mm offset. I might also have to get a widened rearend (both of these options would put me over the $4k of the custom wheels). Or #2- Do a front clip swap, which would narrow the frame rails, and use a narrower suspension. To me this isnt an option, Im just mentioning it. I have a ton of time and work in the suspension now. Im not willing to cut the front half off and start over.

      I have seen a Youtube video where a guy used really good wheel spacers, that were massive (12" on each wheel) and they didnt break, and trust me...he tried to break them. I could also use a narrower tire, I think they make hellcat replica wheels that are 8" wide.

      I just dont know what to do. I might have to stick with what I have. I posted a few pictures, but Im not sure they tell the story.
      Attached Images Attached Images    

    2. #2
      Join Date
      Apr 2006
      Location
      Huntington Beach, CA
      Posts
      2,415
      Country Flag: United States
      Forgestar super deep concave wheels have negative offset options. Another lower prices option is Team III / ET Mags LT-III wheel.

      But spacers aren’t that big of a deal IMO. When wheel to wheel racecars are using 1”-2” spacers (adapters) fine I think we would be fine.
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      Autocross and track blog about running autocross and track events with pro touring cars

    3. #3
      Join Date
      Feb 2019
      Posts
      218
      Quote Originally Posted by Chad-1stGen View Post
      Forgestar super deep concave wheels have negative offset options. Another lower prices option is Team III / ET Mags LT-III wheel.

      But spacers aren’t that big of a deal IMO. When wheel to wheel racecars are using 1”-2” spacers (adapters) fine I think we would be fine.

      Thank you. I have just always been told spacers are bad. But I guess if I use good spacers, it might be ok. The replica hellcat wheels are around $250 each, versus $1000-1250 each for custom offset forged wheels. And the odd geometry associated with the custom length a-arms, and custom spindles is above my understanding. As long as it doesnt do anything weird to the steering. Im not talking about anything bigger then 2" up front. I havent done the math, but it might only be the 1-1/2" I already have.

    4. #4
      Join Date
      Apr 2009
      Location
      Michigan
      Posts
      322
      Country Flag: United States
      I also think you could get away with the spacers. The root cause of your problem is your huge scrub radius, which causes the front tires to swing in a big arc and get close to the frame. If you ran longer A-arms (reducing scrub radius to ideally around 0), you could run wider tires without frame clearance issues. But as you mentioned, the custom A-arm idea requires a good understanding of front end geometry and a lot of $.

      On a related note, if you stick with your current setup, you'll need a very high spring rate and matching damping since your motion ratio is so extreme. Since your track width is so wide, the tire will have a ton of leverage on the coilover (and the mounts on the A-Arm and frame).
      - Ryan

    5. #5
      Join Date
      Nov 2016
      Location
      Sulphur, La
      Posts
      598
      I use 2" spacers on my Jeep crawler with 40" tires, 1 ton axles and nitrous as well as small ones on road race cars. I have never had any issue with them.

    6. #6
      Join Date
      Feb 2019
      Posts
      218
      Im not too happy with the IFS so far, but I havent driven the truck yet. It had a solid axle in 67, so almost anything is an improvement. The IFS came with coil overs, but they are just cheap china non adjustable crap. Im going to get some QA1s when it gets closer. I talked to them on the phone, and they said if I got them 4 corner weight, they would advise me on spring rate for this truck. Itll be expensive, but worth it. And this is another reason I dont want to mess with custom A-arm lengths and such.

    7. #7
      Join Date
      Apr 2009
      Location
      Michigan
      Posts
      322
      Country Flag: United States
      Quote Originally Posted by drummerdad View Post
      Im going to get some QA1s when it gets closer. I talked to them on the phone, and they said if I got them 4 corner weight, they would advise me on spring rate for this truck. Itll be expensive, but worth it. And this is another reason I dont want to mess with custom A-arm lengths and such.
      Sounds like a good plan. When you talk to QA1, they will need to know the motion ratios as well as the corner weights. Make sure they know how far the center of the tire contact patch is from the inner A-arm pivot so they can calculate the front motion ratio correctly. Often people assume the lower ball joint is inline (vertically) with the center of the tire, which is sometimes an okay assumption, but that certainly isn't the case with your truck.
      - Ryan

    8. #8
      Join Date
      Feb 2019
      Posts
      218
      Thanks for the advice. Ill get them any dimension they ask for. I want to make sure this truck rides good.

    9. #9
      Join Date
      Apr 2007
      Posts
      193
      Sounds to me you are mixing 5x114.3 (4.5") hubs and 5 on 115mm wheels. Get spacers that are correct for resolving that. For a "cruiser" some people think the risk of off-center mount up, subsequent shake-loose, and the whole risk of stud breakage due to misalignment are acceptable. I disagree. Strongly. Though you may take your initial test drives as is. Because I'm going there next... ;)

      The big scrub radius you created- well I've driven vehicles that were poor driving because of it (road grooves constantly pulling at the wheel) and some you definitely couldn't even tell. Fact is most guys with accessorized late model trucks have crazy scrub radius, and don't know or care. But that's with some front ends where every dimension and motion has hundreds of hours of computer time that makes them really spot-on as a start point. IMO drive it and see.



      I think you realize adding length to the A-arms meaning redoing the steering, too. Honestly for you, that really means a new plan entirely. So get to that point- driving.






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