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Thread: Wheels

  1. #1
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    Wheels

    Hey folks,

    New to the forum and looking at starting a GTM project.

    I'm leaning toward black wheels which FF doesn't have. What are people going with in that regard? And what wheels would work with the largest Wilwood set available?

    I know many have been down this path before me and just wondering how things have worked out. Larger wheels for max traction? vs best braking setup. Is there a sweet spot on both?

    Thanks for all opinions.

    Mike

  2. #2

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    Contact Shane @ http://vraptorspeedworks.com/
    He's probably done more of these than anyone else and is a great resource.

  3. #3
    VRaptor SpeedWorks, LLC's Avatar
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    That's a question without a simple answer. I just went to the FFR website and they no longer have any wheels listed for the GTM in their parts catalog? If memory serves, even FFR has changed this up on every set of optional wheels since the beginning.....I think the first set of wheels FFR offered were CCW wheels, 18" front and 19" rear. Then the Forgestar wheels were 18" wheels all around. The last set they listed were 19 front and 20 rear. With the hundreds of different wheels out there, it is impossible for me to tell you what will fit and what won't as far as brake clearance. In my own experience, there is not much problem clearing the Wilwood brakes and only the wheel manufacturer is going to be able to tell you for sure if it will clear if you provide them with the brake specs. The only brakes I've had any difficulty with on wheel fitment are the Z06 brake kits and the Brembo's that both have very large, bulky calipers.
    Shane Vacek
    VRaptor SpeedWorks, LLC
    www.vraptorspeedworks.com
    Turn-key GTM, SL-C & Ultima GTR Built to Your Specs!
    Offering a full line of GTM Upgrades and Custom Parts

  4. #4
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    Thanks Shane. They list the 19 fronts and 20 rears under options, but not in the parts catalog.

    Anyone have issues with a 20 on the back?

    I guess searching for options means starting with a '04 Corvette wheel replacement?

  5. #5
    VRaptor SpeedWorks, LLC's Avatar
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    That depends on if you want to run the spacers in the rear. If you are using Corvette-offset rear wheels, then you will have to run the FFR-provided wheel spacers. If you get the optional FFR wheels, they already have the proper offset built into the wheels so that you don't need to use the spacers.
    Shane Vacek
    VRaptor SpeedWorks, LLC
    www.vraptorspeedworks.com
    Turn-key GTM, SL-C & Ultima GTR Built to Your Specs!
    Offering a full line of GTM Upgrades and Custom Parts

  6. #6
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    Hey Canyonblue,

    I went through this exact exercise on my GTM. What I did was take the specs that FF listed on their site for the Forgestar 19s and 20s and then went to another supplier to get them. My lead time was about 6 weeks as they were custom made, but I got the exact specs I wanted and the color (matte black in my instance). From there I pulled all the spec sheets on the Wilwood brake packages that are available for a C5 Corvette. There are spec sheets online that will show the exact area of the rotor and calipers. I went through three spec sheets measuring with wheels before I found what fit. If memory serves me, is the Slim Line 14" rotors for both the front and rear. I have bolted everything up on my car and everything fits nicely. Next step will be to work the body around them once I get to that stage.

    I have the PNs in my BOM at home and can pull the Wilwood Kit I ended up with when I get home.

  7. #7
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    Just check that the tire you want to run is available for your desired rim diameter and width.
    Cheers,
    Dave

    GTM # 294 Build Start Date 10/12/2009,
    2000 C5 Donor, LS-1 Twin Turbo, AC/Heat, G50-20.02 6 speed, Brandwood Cable shifter
    Build site. http://s679.photobucket.com/albums/vv153/dfraser/

  8. #8
    Senior Member jamesfr58's Avatar
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    I have a set up with 19” front and 20” back wheels. They are IPW wheels, the front wheels are 19X8.5 and the rears are 20X10 with the C5 bolt pattern 5X4.75. They had the right wheel offset to fit my Wilwood big brakes, they are 6 piston fronts, 4 piston backs and I am using EDC racing rotors – BSD Series Sport w/Ultra Quite V Slot configuration mounted on new Detroit Axle hubs. The wheels are gun metal grey.

    You can see the wheel offset clears the big brake caliper, but it is close. It was hard to find a wheel with right offset using the Wilwood big brake system as they are considerable larger that the corvette brakes. Making sure you have right wheel offset to clear your brake caliper is an exercise if not using the corvette wheel. VRaptor is right in is a big deal to make sure the offsets / backspacing to insure they fit with the calipers no matter which ones you use.

    IMG_1462.jpgIMG_1463.jpgIMG_1464.jpgIMG_1465.JPGIMG_1467.JPG

  9. #9
    Senior Member jamesfr58's Avatar
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    I have a wheel back space calculator in excel if you would like a copy, just PM me your email and I will send you a copy.

  10. #10
    VRaptor SpeedWorks, LLC's Avatar
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    Quote Originally Posted by Fraser D View Post
    Just check that the tire you want to run is available for your desired rim diameter and width.
    Dave makes a very good point here. Once you get into 20" tires, your selection is very limited....and if you are running 20's in the rear and 19's in the front, there is going to be less than a handful of tires that will be available in both the front and rear sizes you'll need.
    Shane Vacek
    VRaptor SpeedWorks, LLC
    www.vraptorspeedworks.com
    Turn-key GTM, SL-C & Ultima GTR Built to Your Specs!
    Offering a full line of GTM Upgrades and Custom Parts

  11. #11
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    Thanks for all the great responses.

    I guess I'm a little confused because under options for the GTM, they list a 19X9 front, and a 20X12 rear wheel. But they sent me the 'GTM Custom Wheel Fitment' sheet and it shows tire sizes for the front as either 245/45/17, or 245/40/18.

    For the rear its either 17-19 inch with a 40mm offset, or 'Wide' at 19 inch 30 series, or extra wide at 17-18'' 335/30/18 or 335/35/17.

    I'm assuming that the 19 inch front and 20 inch rear are using the 'plus one' method for fitment along with the appropriate offset like Shane mentioned.

    I like the idea that Shane and Dave mentioned about maybe keeping everything at 19 inches.

  12. #12
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    Heres what I'm doing.

    Front 19 X 9 to what the FF specs were for the Forgestars
    Brakes: Wilwood PN 140-8230
    Tires: Michelin Pilot Sport Cup 2 245/35/19

    Rears 20 X 12 to what the FF specs were for the Forgestars
    Brakes: Wilwood PN 140-9119
    Tires: Michelin Pilot Sport Cup 2 325/25/20

    Fronts:


    Rear:



  13. #13
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    That looks awesome Shoeless. That's the kinda look I'm thinking about.


    I just don't want to make some huge costly error and be left with something that doesn't work between the wheel and the brake.

  14. #14
    VRaptor SpeedWorks, LLC's Avatar
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    Quote Originally Posted by Canyonblue View Post
    Thanks for all the great responses.

    I guess I'm a little confused because under options for the GTM, they list a 19X9 front, and a 20X12 rear wheel. But they sent me the 'GTM Custom Wheel Fitment' sheet and it shows tire sizes for the front as either 245/45/17, or 245/40/18.

    For the rear its either 17-19 inch with a 40mm offset, or 'Wide' at 19 inch 30 series, or extra wide at 17-18'' 335/30/18 or 335/35/17.

    I'm assuming that the 19 inch front and 20 inch rear are using the 'plus one' method for fitment along with the appropriate offset like Shane mentioned.

    I like the idea that Shane and Dave mentioned about maybe keeping everything at 19 inches.
    On the tire sizes, it sounds like FFR just forgot to update their tire sizes to match the wheel size for the fronts. You will also want to note that just because a 335/30/18 tire will fit does not mean that you can fit a 335 20" tire in there. As the wheel/tire size grows, you run out of clearance on the inboard edge at the chassis because there is a chassis tube that angles in toward the tire......smaller diameter tire fits farther back into the angle....larger diameter tire will hit the angle.
    Shane Vacek
    VRaptor SpeedWorks, LLC
    www.vraptorspeedworks.com
    Turn-key GTM, SL-C & Ultima GTR Built to Your Specs!
    Offering a full line of GTM Upgrades and Custom Parts

  15. #15
    Senior Member Roger Reid's Avatar
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    I used a 345/30/19 in the rear which caused all kinds of problems. First at full shock compression the tire hit/rubbed the chassis tube just above and forward of the wheel. This caused me to add a spacer to move the tire more outboard. Then after moving the wheel out it hit the fender which had to have bodywork (by Shane who did great job) to widen the body. None of that is cheap. I suggest using the 315/19 rear and a 275/19 front. To me there is no way I would touch a 20 inch wheel as rubber choices are limited.
    Just an old man with a great hobby

  16. #16
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    To reiterate what has already been said, I chose to stick with 18" diameter wheels because of the huge selection of tires available for 18" rims. Also, CCW was sold to Weld, but they still offer the services that CCW used to offer and have a dimension file for the GTM on hand. That means that you can call them up, tell them the style wheel you want, they have all the numbers, and can tell you if they can build it or not. Unfortunately, with the buyout it seems the prices have gone WAY up, but the CCW wheels are a good product. We run the 3 piece Classics on the FFR PDG GTM race car.

    I tell this to people all the time, but I don't think it really sinks in until they actually try and make something work...start with the tire you want and work your way in to the upright. In other words, find the tire you want to use, then find a wheel style that you like that comes in a size required for the tire, then see if the brakes you want to use will fit with the rim you have chosen.

    The power of the 3 piece wheels is that we can change tire widths and only have to change either an inner or outer ring to make the rim the proper size for the tire. Very convenient and a big $$$ saver.

    For reference, we run a 345 rear tire and a 300 front tire, both on 18" rims. Fronts are 10.5" wide and the rears are 13" wide. The front rims are actually speced to a stock rear 2004(IIRC) Corvette ZR1. Our rears are custom with 10" inners and 3" outer rings.

    We do have slight clearance issues with this large of a front tire, but rarely turn that tight.
    Last edited by crash; 03-22-2019 at 04:45 PM.
    www.myraceshop.com

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  17. #17
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    I might have to scoop up a set of the CCW for the track wheels. Pretty slick, but pricey.

    My racing buddy said the same thing that Crash is mentioning here. He pointed out to me that most track tires are in 18" diameter, so I better start there.

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