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  1. #1
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    Fitment question

    OK. I've searched and read like, literally, 25 threads. And everyone seems to have an opinion on what fits what but nothing pertaining to my exact set up. I have a 09 cop car w/Scat Pack springs. I'm interested in the rears as I'm satisfied with the front set up. Right now, the rear is a 20x10, 25mm offset with 275/40-20 tires. I got a really good deal on a couple of near new Cooper 305/35-20 tires which, according to Cooper, will fit on a 10" wheel, being the narrowest recommended rim. However, the clearance between the inner fender well and the side wall of the current tire seems to be about, at best, 3/4" or a bit less on both sides, which makes me wonder if I'll have problems with the new tires. I'd like to have all parts available when I do the swap so it's not sitting in the garage waiting for spacers to arrive. So, my question is: will I need a couple of 6mm spacers or will they fit w/o them. Also interested in the fender lip with said set up both w and w/o spacers. If somebody owns a 20x10, 25mm w/305/35-20 or if you have physically seen that set up, please chime in. TIA



  2. #2
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    There are so many variables here but I'll give my opinion that you can disregard if you find an exact answer.

    First, you can have a major variance from one 305/35 tire to the next. When you are using a few millimeters to make your decision, it's better to have the spacers on hand.

    My setup is a 300srt with a widened 9" oem wheel, bringing it to 20x10 with a 32.2mm offset. I am currently running a 315/35 Michelin PS4 and using a 10mm spacer. With a 295/35 Michelin PSS I had a 6mm spacer. I'll be going to a 305/35 Michelin PS4S so assuming an actual 10mm of difference, I should have 6mm to play with If I go back to a 6mm spacer.

    Given your offset is 6-7 lower than my setup, you would have 1mm to play with if you had no spacer.

    There are a ton if variables there but I would recommend to have a 3mm and 6mm spacer set on hand as I did when I first installed my setup.

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    Last edited by BM_SRT; 11-06-2019 at 10:39 PM.
    2006 300c SRT8
    PWR Ported Heads | HHP Stage 2R Cam | 3.91 Getrag | GTP Ported Intake Manifold | Kooks Longtubes | Corsa Sport / SRT Resonators | AMG 8 Piston Brake Calipers | Hemituner 6,800 TCM | BT Catch Can | LMI True CAI V2 | Tranzformer | MM 87mm TB | Johan Tuned | REM Adjustable Endlinks & Front/Rear Shock Braces | 33/22mm Front/Rear Sway Bars | Michelin Pilot Sport 4 315/35/20 & 275/40/20 | 10" Widened Oem Wheels | LC-2 Wideband Analog Output to Trinity | Mishimoto Full Aluminum Radiator

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  3. #3
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    I have a set of 10.5s with 305s and I’m lowered beyond scat pack height imo you will be fine previous poster has spacers because that offset is way too high.


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  4. #4
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    Quote Originally Posted by Eric40962005 View Post
    I have a set of 10.5s with 305s and I’m lowered beyond scat pack height imo you will be fine previous poster has spacers because that offset is way too high.


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    What is the offset of your wheels?

    The offset is high by design due to the widening to the inside of the oem wheel. Most aftermarket wheels in the the 10-11" range have a generously low offset for fitment but results in the wheel sticking out from the fender. With the higher offset I can fit 315s within in the fender to keep a factory fitted look.


    Also OP can use Tirerack to compare the measurement of the two tires. Focus on the tread width measurement and not the section width. Just as an example, a Michelin PSS in 295/35 can vary by 8mm if you use the Porsche vs. Ferrari model. That's a huge difference and the reason I originally went from a 6mm to 10mm spacer.

    If you can find your specific tires, you can gather data from similar ones and arrive at a good statistical estimate of the treadwidth. If you actually have the tires on hand, you can measure as well but it's difficult when they are not mounted.
    Last edited by BM_SRT; 11-07-2019 at 05:28 AM.
    2006 300c SRT8
    PWR Ported Heads | HHP Stage 2R Cam | 3.91 Getrag | GTP Ported Intake Manifold | Kooks Longtubes | Corsa Sport / SRT Resonators | AMG 8 Piston Brake Calipers | Hemituner 6,800 TCM | BT Catch Can | LMI True CAI V2 | Tranzformer | MM 87mm TB | Johan Tuned | REM Adjustable Endlinks & Front/Rear Shock Braces | 33/22mm Front/Rear Sway Bars | Michelin Pilot Sport 4 315/35/20 & 275/40/20 | 10" Widened Oem Wheels | LC-2 Wideband Analog Output to Trinity | Mishimoto Full Aluminum Radiator

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  5. #5
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    Here's a simple answer without all the hippitty hoopla.

    Yes, they will fit, but they will only leave you about 1/4 inch space against the inner fender and under hard corners will make light contact.

    A 6mm spacer would give you about 1/2" space, won't bulge out from the fenders and you won't need longer wheels studs.

    Anything thicker than 6mm will require longer wheels studs to have the proper thread engagement to make it safe to drive.

    20x10.5/+25mm offset with 315/35/20s and a 6mm spacer at stock SP height for reference...

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  6. #6
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    Pretty much all of the aftermarket wheels that fit are a +25 offset as punisher listed. And they won’t protrude none of them do the issue is as punisher noted is rubbing inner liner I never had rubbing on my set up believe it or not my factory 275s on 9.5s rub in the back not my 10.5s

    And as I said I’m way lower than Scatpack springs




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  7. #7
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    Honestly there’s a factory reproduction thread that is repeating everything me and punisher are saying


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  8. #8
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    Also which cooper are they? I run a set for rainy weather


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  9. #9
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    The all season one. Thanks to everybody. Guess I'll order a set or 2 to have on hand.

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