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Widest wheel/ max offset&back spacing allowed on factor 90ex car.

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    Widest wheel/ max offset&back spacing allowed on factor 90ex car.

    Got a quick question for you knowledgable wheel guys and or "stanced" herrafrush etc.What's the max offset and back spacing on a 7-8 in 14-15in wheel on factory length studs and brakes. It's a dirt track car not the popular look at me stuff, strictly function.

    Or widest wheel and max offset/ back spacing I could run using factory ex brakes and stud length, with no or minimum spacer. Up for opinions on the matter it has to be done, unless any gurus think running an OEM alloy and widest tire I can fit on the rim would work aswell.

    02 Crv
    02 silverado Ex cab Z71, 2011 TRD 17" wheels, 245/80/17, ls1 cam, AFE intake, 3" catback, tuned by Larry at LSXperformance&pcm tuning driven daily.
    92 Acura Legend colbalt blue LS Coupe, custom intake, custom vibrant 2.5 cat back, led cluster and high beams, 2016 Coyote GT 18x8 wheels 235/40/18.
    Coming Soon Tein TSX coilovers.

    #2
    I've actually been doing a good amount of reading on this lately cause I'm in the process of fitting wheels myself.

    I'd say 25 would be the maximum for a 7" wide wheel, and 30 for an 8" wide wheel. You said it's a dirt track car, are you lifted? As you might be able to run less offset because of the increased suspension travel. My .02 hope it helps.

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      #3
      x2. A 20-30mm spacer on an oem offset tire will put it just about flush with the fender.

      There is about 125mm or so from the mounting face of the rotor to the knuckle. You may want to double check that number though.

      Also while you're at it, get the numbers from the rotor face to the fender. I don't think that's been officially measured here. You'd make a great contribution with that info!

      YouTube Clicky!!

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        #4
        Originally posted by SOHC-FTW View Post
        unless any gurus think running an OEM alloy and widest tire I can fit on the rim would work aswell.
        The OE rim is 5.5" wide and is really too narrow even for the OE sized tyre (195 section width), unless ride comfort is the prime consideration. The wider the tyre relative to the rim width the less stable a given tyre will be, causing the sidewall to behave 'as if' it were softer than it really is (it will suffer from a lack of 'lateral stiffness'). This will manifest as poor steering response and 'floppy' handling, but a more compliant ride quality. Wider tyres will fit on the rim, but it's not a good idea if you want sharp steering and handling.

        My car has 6.5" Prelude wheels, and I use 185/60 section tyres with those. This lightly 'stretches' the sidewall and makes the sidewall effectively somewhat stiffer. You can go too far with sidewall 'stretching', and many people do, chasing a fashion driven extreme 'stretched' appearance (form over function, rather than the other way around...). I'd be happy to use 195 section tyres (maybe even 205) on these 6.5" rims, if the tyres have a stiff enough sidewall (but it's hard to find stiff sidewall tyres in 195/60/15).

        NASCAR style racers do use very wide tyres on a relatively very narrow rims, but this is a specific application where the rules stipulate a given maximum rim width but are less proscriptive re tyre width. The imperative is to get as much rubber on the road for outright grip, so the widest tyres reasonably possible with the mandated rim width are used. However, it's my understanding that the tyres used in NASCAR are designed with this legal peculiarity very much in mind and therefore have very stiff sidewalls to account for being fitted to rims that for any other tyre (of that width) would be way too narrow...

        Note that when fitting wider rims you need to be aware of the backspacing. I found that even with the modestly wider Prelude rims that at full steering lock the inner rim edge would contact the front ARB mounting, necessitating that steering lock be reduced. I used rubber wrapped around a leg the inverted Y shaped coil-over yoke (held in place with very large pull ties), so that the steering arm contacts this rubber pad to prevent the wheel turning far enough that the rim contacts the ARB mount.
        Last edited by johnl; 03-30-2015, 11:46 PM.
        Regards from Oz,
        John.

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