When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Wheels and TiresNeed help with wheels or tires? Got fitment issues? Have questions about tire performance and handling? Ask all of those questions here!
Hey everyone, Not a wheel tire geek, haven't found anything I can rely on with wheel sizes during a short look, I'm looking to get American racing groove vn514 wheels but not sure what would be a good combination with sizes.. as the car will be an Auto X car i want the widest possible I can fit. front and rear. I've seen a few posts saying 245/40/17's are this biggest in the front and 275/35/17 for the rear, although I've seen 275/40/18 front and 295/40/18 fit in the rear with the same rim I want. Granted I'm not sure what modifications where done to that specific IROC, so in other terms I am right where I started.... lost.
I know a little bit to know the IROC has different spacing and the wheels are staggered, but anyways need some help. TO help my car is an 85 z28 with no suspension mods YET. With an 87 GTA rear end should be the same width and spacing in the rear as i recall.
I used to have 275/40/17 all around. It was a great size. Not i have 275/40 18 up front and 305/35/18 rear. I have a 9 in wide front and 10 in rear. Im using nitto NT01s and they stick really well. The 305s just fit in the rear and don't hit anything.
This last one the car is lifted in the rear and the axle is shifted out slightly.
oh sweet! any back spacing? are you rubbing around corners? are you saying you fit these with no modifications?
minor rubbing at full lock up front. Nothing in the rear. The front bs was 5 i think. Rear was 5.75
i think 20 yrs ago i clearanced the rear around the trailing arm. Theres a piece of wheel well that is a thin piece of metal. I bent it in a little. That was for the 275s.
Last edited by Firechicken82; May 2, 2026 at 05:21 PM.
I ran 295/30/18 on all 4 corners. Just a little hammering in the rear if you dont want them sticking out and the front will fit but you will lose a little turning radius. Thats almost eliminated with tubular a-arms that offer better clearance on the back side, I have UMI's on the car at the time. People have ran 11" wheels and 315's but that usually requires you to clip the bottoms of the fenders.
The current build will likely have 355/30/19 on all 4 because why not, but there has been a lot of work done to the car to make that fit.
Those wheels you're looking at look nice, IMHO. Important, though is to get the weight of any wheel you're wanting to use. They vary greatly by manufacturer, and you want the lightest wheel on the car you can get. We put some nice 18"X12" forester wheels on our car, and dam, they are heavy!! With 12"X18" wheels and 335 tires, though, you have to cut the front wheel opening to make room as you turn the wheel.
18" wheels will give you a little more clearance around the front strut, so you can go inboard 1/4-1/2" more, which is a good thing for fitting everything under the wheel openings and getting as much tire on the ground as possible. They will 'polish' the sway bar, but that's not too bad, since there's rarely any sharp bits on it. Pay attention to the back side of the front wheel well for any firewall seams you may need to 'massage' out of the way.
Going inboard as much as possible on the back, you have to pay attention to proximity of the bump stop mounts. I don't think it's as a big deal with 18" wheels as it was with 16", but pay attention. We cut a sticker Hoosier slick down on the bump stop mount at an event. We mini-tubbed our car, cutting back to the inner 'frame' rail to give more room under there. Additionally, with tubular rear lower control arms, you can move the spacers to the outside of the arm to move the arms inboard on the car, providing even more clearance. You may still polish the arm in hard turns, but like the front sway bar, it should be pretty smooth there, so all you should get is a bit of rubber buildup and some smoke on course.
Those wheels you're looking at look nice, IMHO. Important, though is to get the weight of any wheel you're wanting to use. They vary greatly by manufacturer, and you want the lightest wheel on the car you can get. We put some nice 18"X12" forester wheels on our car, and dam, they are heavy!! With 12"X18" wheels and 335 tires, though, you have to cut the front wheel opening to make room as you turn the wheel.
18" wheels will give you a little more clearance around the front strut, so you can go inboard 1/4-1/2" more, which is a good thing for fitting everything under the wheel openings and getting as much tire on the ground as possible. They will 'polish' the sway bar, but that's not too bad, since there's rarely any sharp bits on it. Pay attention to the back side of the front wheel well for any firewall seams you may need to 'massage' out of the way.
Going inboard as much as possible on the back, you have to pay attention to proximity of the bump stop mounts. I don't think it's as a big deal with 18" wheels as it was with 16", but pay attention. We cut a sticker Hoosier slick down on the bump stop mount at an event. We mini-tubbed our car, cutting back to the inner 'frame' rail to give more room under there. Additionally, with tubular rear lower control arms, you can move the spacers to the outside of the arm to move the arms inboard on the car, providing even more clearance. You may still polish the arm in hard turns, but like the front sway bar, it should be pretty smooth there, so all you should get is a bit of rubber buildup and some smoke on course.
OK, this is all good information. did you remove the plastic fender-wheel well? You are running 18x12 335 all around is what i'm understanding? If so that is ENORMUS ! Have you figured out the wheel balance is better staggered or same wheel sizes? i would imagine tire would not be the limiting factor going that big up front. Also if i'm following you had to clearance the rear for that too. What are you doing to get all that negative camber up front?
OK, this is all good information. did you remove the plastic fender-wheel well? You are running 18x12 335 all around is what i'm understanding? If so that is ENORMUS ! Have you figured out the wheel balance is better staggered or same wheel sizes? i would imagine tire would not be the limiting factor going that big up front. Also if i'm following you had to clearance the rear for that too. What are you doing to get all that negative camber up front?
Our car came to us as a running CP-class car, and every possible ounce was taken out prior to us getting the car, so no inner liners. Yes, it's square, 335's all around. The back tires don't do much but keep the rear bumper from dragging, and help get power to the ground. It can be throttle-steered, though.
The car started with 10X16" wheels all around, to take advantage of the weight break 10" wide wheels provided. That rule is now no longer valid, so we went to 12" rear wheels so we could run 13" wide slicks on the back. With 16" wheels, the inner wheel lip is in close proximity to the upper strut mount, so we didn't go any wider there. The idea was to keep the car as 'narrow' as possible, so it could be quicker through slaloms vs. having 3" of tire sticking out both sides. With 18" wheels we could clear the strut and get more wheel/tire inboard, limiting the width growth to less than 2". I figured that was a good compromise to get 4" more of tire width front and back to the ground. While we had to switch from slicks to A7's, other competitors have noted that there's not that big a difference in traction between the Hoosier slick and A7. The car sticks well, and easily gets over 1.2G in the sweepers.
The wheels are heavy, though, so we may try to research something lighter. It would be nice to find something as light as our Real 3-piece wheels, but at 18" diameter, that may not be possible. The search may start soon, though, depending on our local region's success obtaining a new venue we can run at. Either that or we wait until my co-driver retires so we can go out of town more often.
The offset also limits turn radius, as the front tires hit the firewall when turning. It's not a big deal, because if we're turning that much on course, that's usually a sucky course layout. It's only a big deal when pulling from grid, but if you think ahead, you can plan ahead.
We haven't done much in the camber department other than pushing the CC plates all the way inboard, and slotting the strut to spindle holes some, but even then, you have to watch the wheel to strut clearance. IIRC we have about -1.5 to -1.75-deg each side. I can't find my notes on it at the moment, though.
Our car came to us as a running CP-class car, and every possible ounce was taken out prior to us getting the car, so no inner liners. Yes, it's square, 335's all around. The back tires don't do much but keep the rear bumper from dragging, and help get power to the ground. It can be throttle-steered, though.
The car started with 10X16" wheels all around, to take advantage of the weight break 10" wide wheels provided. That rule is now no longer valid, so we went to 12" rear wheels so we could run 13" wide slicks on the back. With 16" wheels, the inner wheel lip is in close proximity to the upper strut mount, so we didn't go any wider there. The idea was to keep the car as 'narrow' as possible, so it could be quicker through slaloms vs. having 3" of tire sticking out both sides. With 18" wheels we could clear the strut and get more wheel/tire inboard, limiting the width growth to less than 2". I figured that was a good compromise to get 4" more of tire width front and back to the ground. While we had to switch from slicks to A7's, other competitors have noted that there's not that big a difference in traction between the Hoosier slick and A7. The car sticks well, and easily gets over 1.2G in the sweepers.
The wheels are heavy, though, so we may try to research something lighter. It would be nice to find something as light as our Real 3-piece wheels, but at 18" diameter, that may not be possible. The search may start soon, though, depending on our local region's success obtaining a new venue we can run at. Either that or we wait until my co-driver retires so we can go out of town more often.
The offset also limits turn radius, as the front tires hit the firewall when turning. It's not a big deal, because if we're turning that much on course, that's usually a sucky course layout. It's only a big deal when pulling from grid, but if you think ahead, you can plan ahead.
We haven't done much in the camber department other than pushing the CC plates all the way inboard, and slotting the strut to spindle holes some, but even then, you have to watch the wheel to strut clearance. IIRC we have about -1.5 to -1.75-deg each side. I can't find my notes on it at the moment, though.
HMM good to know, the courses in my region usually have a lot of 180 degree turns, or courses that double back into the same areas, wondering if going that big would be a problem, Those slicks in 355 and 13 in must be pricey too, I'm thinking I might want to try 305/30/18's all around to start out, any recommendations for backspacing?
No clue on an unmodded car. Ours has been mini-tubbed, and a bunch of stuff has been moved around out back from OEM. I think the wheels are a +6 'ET', but I was copying another competitor's recommendations, as I duplicated the wheels he was using. Yes, they'll make tight turns an issue.
No clue on an unmodded car. Ours has been mini-tubbed, and a bunch of stuff has been moved around out back from OEM. I think the wheels are a +6 'ET', but I was copying another competitor's recommendations, as I duplicated the wheels he was using. Yes, they'll make tight turns an issue.
Gotcha good to know. The other builds with the same rims are running +5.5 so that sounds about right. What front and rear calipers are you running? i've thought of c5 z06 rotors and calipers, and I think I have seen cts-v set ups too.
Mine are 5.75 rears. There is plenty of room around the wheel/tire. Ive heard of people using 6-6.25. There is more wheel clearance around the struts/bump stops w 18s vs 17s. Up front I could easily fit a 10 vs the 9 wide that i have. I have 275s. Im sure a 295 would fit. My 305s wouldn't fit up front. They're really big. My wheels are moved out 1/4 in D/t the wilwood brakes. The nt01s stick really well, i cant imagine 335s.
Mine are 5.75 rears. There is plenty of room around the wheel/tire. Ive heard of people using 6-6.25. There is more wheel clearance around the struts/bump stops w 18s vs 17s. Up front I could easily fit a 10 vs the 9 wide that i have. I have 275s. Im sure a 295 would fit. My 305s wouldn't fit up front. They're really big. My wheels are moved out 1/4 in D/t the wilwood brakes. The nt01s stick really well, i cant imagine 335s.
Sweet, i might buy a rim and measure clearances around and go from there.
Sweet, i might buy a rim and measure clearances around and go from there.
To get an idea of tires that would fit. I measured and then ordered a used set NT01s in the size in thought would fit. They were 75 for the pair, shipped. I had a friend w a tire machine mount them w/o weights. Then i went out and ripped around in the car and looked for issues. There were none, so I went out, burned up the tires more and then got new ones!
To get an idea of tires that would fit. I measured and then ordered a used set NT01s in the size in thought would fit. They were 75 for the pair, shipped. I had a friend w a tire machine mount them w/o weights. Then i went out and ripped around in the car and looked for issues. There were none, so I went out, burned up the tires more and then got new ones!
$75? where did you buy em? I struggle to find tires under $120
Well, I finally ordered that wheel and threw it on the front that was already in the air. My first thoughts were MAN THESE RIMS LOOK KILLER!!!! Then it was, oh man, i don't think this is going to fit, as I was pulling the rim up to the hub. BUT MAN WAS IT CLOSE, LOL.
This might be the biggest rim you can put on this stock z28 hub without rubbing on anything, Maybe a 18x10.5 or 18x11 but the pictures below show how close everything is. A 295 might not fit with this as it might stick out and roll a little bit under load. Closest thing to the rim was tie rod end, shock and sway bar, would be closer with a larger sway bar.
Well, I finally ordered that wheel and threw it on the front that was already in the air. My first thoughts were MAN THESE RIMS LOOK KILLER!!!! Then it was, oh man, i don't think this is going to fit, as I was pulling the rim up to the hub. BUT MAN WAS IT CLOSE, LOL.
This might be the biggest rim you can put on this stock z28 hub without rubbing on anything, Maybe a 18x10.5 or 18x11 but the pictures below show how close everything is. A 295 might not fit with this as it might stick out and roll a little bit under load. Closest thing to the rim was tie rod end, shock and sway bar, would be closer with a larger sway bar.
