Anyone actually running 18x9.5 fronts with 6.5"+ BS?

Discussion in 'Tires and Wheels (Mopar Hubcaps Too)' started by khuebner250, May 10, 2018.

  1. khuebner250

    khuebner250 Well-Known Member

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    I feel there is a ton of conflicting info on this subject. I read everyone's comments that a 275 on a 9.5 wide wheel will fit no problem but it always turns up they have a 18x8 or 9 with 5-6" BS with a 245 or 255. On a normal 18" hoop will the tierod actually fit inside of the hoop and allow turning? I have a wheel fit tool (it's aalittle thicker than a hoop) and it hits the rod end and at full compression the tire hits the fender lip while turned.
    I'm running the following:
    68 barracuda
    SPC uppers
    73+ spindles
    11/16 rod ends
    Hotchkis strut rods
    Hellwig sway
    Fender corners cut and lip shaved

    Uchoog1 is running 7.125" of backspace but I've heard it only fits because it's a cobra wheel and not a standard hoop. Is anyone actually running a standard or softlip regularly available hoop in 18x9 or 18x9.5 with more than 6.5" of back spacing? LMK or if you have pics please postem. Let's get this cleared up.

    Thanks, sorry it's long winded
    Keith
     
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    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      First, yes, I'm one of those guys running 18x9's with 275/35/18's. 18x9.5's aren't a problem, but you may need a small spacer to keep the tires off the frame when turning with a 6.5" backspace. The tie rod shouldn't be a problem, they do fit inside the rim. Tire to frame clearance will probably be too tight, you'll probably want to end up more like ~6.3" or 6.4" for the backspace. That would be the same inboard clearance to the frame as I have.

      tomswheels ran 18x10's with 285/35/18's up front on his Valiant. The wheels he used had a +42 offset, which works out to a 7.2" backspace, but he also used 3/4" worth of spacer. So his final backspace was more like 6.4", and his tires would have been the same distance inboard as my 275's. That combo would stick out .4" further than mine, and Tom pushed his fenders out with a hydraulic ram and rolled the edges.
      AutoCross-Crows Landing, CA this weekend!
      image-jpg.jpg

      On that note, if I remember correctly Uchoog1 was running the early AR engineering Viper brakes on his car. Those brakes add a 1/2" to the track width, which would make his effective backspace more like 6.6" compared to a car with 73+ disks. You have to be careful just looking at the backspace of the rim, you have to consider the track width changes with any brake upgrades. For example, my 18x9's are a +35mm offset, so, 6.4" of backspace. But my DoctorDiff 13" rotors add 5/16" to the track, so, my effective backspace is more like 6.2". And then I added a 3mm spacer to stay off the frame, so, 6.1".

      But if you compare the center line of the wheel, or look at the inboard distance of the tires, that would be the same as a 275/35/18 on an 18x9.5 with a 6.3" backspace.
       
      Last edited: May 10, 2018
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      • oi81b4uu812b4

        oi81b4uu812b4 Well-Known Member

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        Last edited: May 18, 2018 at 10:30 AM
      • 72bluNblu

        72bluNblu FABO Gold Member FABO Gold Member

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        Those are some pretty thick stick on weights. Quite a bit of weight too for a modern aluminum rim.

        It definitely does depend on the design of the rim though, some will have more room than others. Also something to consider with the 11/16” tie rod ends, you may have less clearance. I use 9/16” tie rod ends, but with tubular adjuster sleeves. The stock split adjuster sleeves are the weak link in the stock system, not really the tie rod ends.
         
      • oi81b4uu812b4

        oi81b4uu812b4 Well-Known Member

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        it’s not the rim, it’s the tire.
         
        Last edited: May 18, 2018 at 10:31 AM
      • khuebner250

        khuebner250 Well-Known Member

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        Well here's some more info and pics. Appx ride height, ~2* camber, ~3.5* caster.

        Wheel tool set up at 18x9, 10" overall width, ~6.3-6.4 BS, 3.5" from hub to outer wheel lip, 275/35-18 25.6" diameter. Hits at full compression turning in both directions.

        IMG_20180513_135637598.jpg

        IMG_20180513_135628413.jpg

        IMG_20180513_135218207.jpg

        IMG_20180513_135218207_TOP.jpg

        IMG_20180513_135211169.jpg
         
      • khuebner250

        khuebner250 Well-Known Member

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        Here's another set up.
        17x4.5 wheel, 26/6_17 tire, hub to outer wheel lip is 3.75". Hits in the same places at full compression.

        IMG_20180513_155942633.jpg

        IMG_20180513_155624972.jpg

        IMG_20180513_155610825.jpg
         
      • khuebner250

        khuebner250 Well-Known Member

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        Not sure how you guys are running tires this tall or wide.
         
      • 72bluNblu

        72bluNblu FABO Gold Member FABO Gold Member

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        Do you have your bump stops in place? Are they stock? What do your steering stops look like?

        Not sure what to tell you, the 18x9’s and 275/35/18’s on the front of my Duster are like 3.9” from hub to outer rim lip, so they stick out further that what you’re testing with that. When I started with those rims and tires I had pretty stock fenders except for thr lower front corner of the wheel opening. As I’ve lowered the car further I did run out of room and rolled the fender lips and added some “push” on thr fenders with the roller when I did that. But my car sits pretty low now. And it was well below factory ride height even when I started.

        Honestly with the tires straight ahead it looks like you’ve got more room than I do. I run less negative camber at -1.5*, so that should actually hurt my clearance. But I run more caster, +6.75*, so I get more camber as the wheels turn.

        These are older pictures, before I lowered further and rolled the fenders.
        IMG_2457.jpg
        IMG_3760.jpg

        IMG_3219.jpg
         
      • khuebner250

        khuebner250 Well-Known Member

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        Bump stops are 3/8" poly low profile. Steering stops are on the proforged lowers.
         
      • oi81b4uu812b4

        oi81b4uu812b4 Well-Known Member

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        Are you trying to run an 18 x 9-1/2" rim with 6-1/2" to 7 1/8" of backspacing?

        Is that \ + / or / - \ Camber?

        You look a little too far down on compression.

        What I have seen on wider than 9" rims is that the tire is 285/30/18 instead of 275/35/18
         
        Last edited: May 16, 2018 at 12:19 PM
      • khuebner250

        khuebner250 Well-Known Member

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        Yes I'm trying to run 6.5 - 7.125 of BS on a 9.5. the pic abofe is 18x9 with 6.4 and hits when fully compressed.
        -2*
        "You look a little too far down on compression" I'm not sure I understand this comment?
         
      • 72bluNblu

        72bluNblu FABO Gold Member FABO Gold Member

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        What he's getting at is that the suspension seems to be compressed further than it should be. Ie, the wheel seems awfully high. That's why I was asking about the lower bump stop. But with a 3/8" stop the wheel shouldn't be any higher than mine end up, at full compression mine will almost hit the inner fender.

        The fender lip seems like it's more of an issue than it is on my car, which is surprising because typically the Barracuda's tend to have a little more room to the fender lip. Less to the front lower corner because of the shape of the wheel opening (which is why you trimmed it back), but a little more to the lip. Maybe the wheel opening is actually a little lower on a Barracuda fender?

        What brakes are those? Because that will have a big effect on backspace.
         
        Last edited: May 16, 2018 at 4:14 PM
      • oi81b4uu812b4

        oi81b4uu812b4 Well-Known Member

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        Did you adjust you SPC uppers with the car lifted off the floor (as shown in all your pics) to set your camber?

        And near as I can tell it looks like you have about 3” of air between the top of your tire and fender lip. When you compress it buy lifting it with your Daytona jack, it looks 2” past the tire wall...

        It looks like you are running 1st Gen Viper Brakes and the Dodge D100 11-3/4” dia rotor?


        So 5” of suspension travel?

        What torsion bars are you runnning?
         
      • khuebner250

        khuebner250 Well-Known Member

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        That pic shows a little low. I set appx alignment at appx ride height. I forgot to take a pic until I started to let it down, then snapped it. At ride height I'm about 1/2" inside the lip. I'm running 1.14 bars.
         
        Last edited: May 16, 2018 at 8:37 PM
      • autoxcuda

        autoxcuda Well-Known Member

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        Full lock and full compression = a major situation....with 1.14” T-bars.

        Like under full lock... skidding across and racetrack... and hitting a berm.

        I skidded off track and hit a berm, but it wasn’t at full lock. I also had .99” t-bars then. Bottomed out the shock and dimpled around the shock just a tad... but noticeable. Shock was fine, alignment fine, rim ... well it bent a 15x8 rally rim in the center.

        Note: the weak point in a rally rim is the center. When they road raced 70-71 Cudas in a stock class in France, they cracked and bent rally rims in the center. Not anything to worry with even a hard street driving car or really a track fun day car.
         
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        • oi81b4uu812b4

          oi81b4uu812b4 Well-Known Member

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          Get your suspension work done, then put it on the ground and then set Camber,Caster & Toe.

          I thought you might have your torsion bars clocked wrong...

          With 3" of air between the top of your tire and fender lip you would have a noticeable \ + / positive camber setup. you look l = l and it shouldn't
           
        • autoxcuda

          autoxcuda Well-Known Member

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          Here’s a stock AAR at resting ride height. Looks if it had 3” compression with the small stock tbars, it would rub

          952A5243-B557-4A23-B930-8D738BDE1BDE.jpeg
           
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          • khuebner250

            khuebner250 Well-Known Member

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            Suspension work is done except torsion bars are out. Lower ball joints are squared up. If I set my spindles to ride height I'm -2* camber and 3.5* caster. Tire turns fine and doesn't hit at ride height. But under full compression it hits front and rear on the fender lip with a 3/8" bump stop.

            Can't get it on the ground because I don't have wheels. Converted SBP to BBP. All these threads and questions are for measurements for custom wheels. I'm wanting to not do custom wheels twice.

            Thanks,
            Keith
             
          • oi81b4uu812b4

            oi81b4uu812b4 Well-Known Member

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            You haven't accomplished anything after bolting on these parts.
            You don't have your ride height set with you car on the ground, so you can't have camber, caster and toe set...

            With 1.14" torsion bars you won't experience 5" of suspension travel like you show.

            I can only tell you that a 18x9 with +30 OS should fit a 275/35/18 tire on the front. With your Dodge D100 rotors and first gen Viper Brembo 4 piston calipers you will need a rim that clears those.

            You don't need to get a 9-1/2" wide rim to mount that tire. Unless you like to have curb rash on your rim lips?

            Who's 17x4.5 Race Star 92's are you using in the pics?

            And it looks like you waited to have the car painted to find rims & tires that just fit? That's backasswards.
             
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            • khuebner250

              khuebner250 Well-Known Member

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              You haven't accomplished anything after bolting on these parts. You don't have your ride height set with you car on the ground, so you can't have camber, caster and toe set... If I set my car on jack stands, account for a small rake, measure where I want my spindles in relation to my fenders... I can't replicate ride height without my car being on the ground?

              With 1.14" torsion bars you won't experience 5" of suspension travel like you show. I never said I had 5" of travel nor did I imply it. That is your figure and I previously corrected your statement.

              I can only tell you that a 18x9 with +30 OS should fit a 275/35/18 tire on the front. With your Dodge D100 rotors and first gen Viper Brembo 4 piston calipers you will need a rim that clears those. I'm running Mercedes 13" front rotors not d100 rotors. And 18x9 +30 SHOULD fit based on what, your assumptions?

              You don't need to get a 9-1/2" wide rim to mount that tire. Unless you like to have curb rash on your rim lips? Nope but in the custom wheel world, readily available hoop sizes are 8, 9.5 and 11. Yes I can get 9" and 12 or whatever size I want but the others are way more common. 275/35-18 is rated for a 9to10" width so I don't understand the weird passive aggressive curb rash statement?

              Who's 17x4.5 Race Star 92's are you using in the pics? It's just one a buddy lent me. It's a 26" tall tire with a hub to outer wheel distance of 3.75. I wanted to see how that compared to some of my other measurements.

              And it looks like you waited to have the car painted to find rims & tires that just fit? That's backasswards.What could I have done differently to avoid doing it backasswards?



              BUT...


              download.jpeg
               
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              • 72bluNblu

                72bluNblu FABO Gold Member FABO Gold Member

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                Nope, not true. Almost none of it is right.

                The car doesn’t have to be sitting on the ground. That’s the beauty of a torsion bar system. If he sets the spindles at right height and sets the alignment, it will be exactly the same sitting on the ground. He just has to set the torsion bar adjusters to achieve that height. And really, as long as it’s close the alignment will be close too.

                The suspension travel range is set by the bump stops, not the torsion bars. He might have 5” of travel. Depending on the ride height he sets, he might not ever see full compression. But his ride height looks pretty low, so, he might. I hit the bump stops on my car with 1.12” torsion bars, so it sees full compression. And bump stop to bump stop is a little less than 5”. I don’t see full extension though except on a jack, my ride height isn’t quite centered between the stops.

                And those aren’t the brakes he’s running.


                Yeah he’s wrong. You can totally set the alignment like that. You just have to duplicate the spindle location when you set the ride height.

                That brake set up adds about 5/16”. So you’ll need an extra 5/16” of backspace, or 5mm of offset. Same as my car. Which is what he’s quoting for the specs, my wheels. I run 18x9’s with a +35mm offset, drdiffs 13” cobra style brakes (same hub as yours), and a 3mm spacer.

                The 18x9.5’s should be ok. The difference in the section width of the tire will be pretty small compared to an 18x9”. The tie rod shouldn’t be an issue. Shouldn’t. Tomswheels had multiple sets of 18x10’s for the front of his car. Now, a bunch of that was on the outside to his pulled fenders, but not all of it was.

                You should be able to run 18x9.5’s. The beauty of using offset is that you should be able to use a +35mm offset, same as mine. It’ll put the centerline of the rim in the same place as mine. The section width will cheat out a little on both sides compared to my car. It will be tight, as you’ve found.

                And as autoxcuda pointed out, you probably won’t hit full steering lock and full suspension compression at the same time. To be honest, I don’t know that my set up would pass that test. I just know they don’t rub.

                You can do lots of math and fitting, but when you really push the limits you just have to see if they work sometimes. Are your fenders rolled yet?
                 
              • khuebner250

                khuebner250 Well-Known Member

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                When I was in the bodywork stage I had the fender lips trimmed to 3/16" and the front fender pied to make sure I had room for a 26" turning radius. I think that's what you mean. They are not flared or pushed out or baseball bat rolled. Also, barracuda fenders don't have any flare to them at the outer lip. They actually have a reverse flare.
                Maybe I just have to bit the bullet and order them up. Just nerve wracking. I appreciate your help and input.
                 
              • 72bluNblu

                72bluNblu FABO Gold Member FABO Gold Member

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                Oh I get it. The rims I have now are not the first set I bought for this purpose. It’s an expensive gamble. I think you’ve done all the homework, it’s close. Close enough that it’ll come down to the bodywork on your car in particular.
                 
              • autoxcuda

                autoxcuda Well-Known Member

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                I totally get it.

                I’ve stalled on ordering rims for about 4+ years trying to decide on brake package... that dedermines wheel backpacking/offset... that determine rear end width... trying to make all 4 rims the same backspace.

                I’ve mocked up 17x8 mustang rims with 275/40/17 up front. Don’t have notes handy but I think they were 5.75” backspace. It seemed like I had a good 1.5” plus more outer clearance than my current 15x9, 245/50/15, 4.125” backspace setup.
                 
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