i'm seriously thinking about getting 20" irocs all around, I've done a lot of searching, and some people say pretty much kiss your fender lip good bye due to the rubbing. then others say 20's fit all around, and have no problem with rubbing. But I think half the people haven't had any experience with them, they are just going off what they have heard. So i need some 'hard evidence' to know for sure what the deal is.

I have sportline springs, which is approx 1.5" drop, maybe a bit more. I need to know if i'm gonna have problems with these or not. The tires I'd be running is a 27" overall tire, and a stock one is 25.7. So i mean its not that big of a change.

If there is a major problem with rubbing, i'm just gonna run 18's up front, 20's in the back, but I want 20's all around just for rotating purposes..

thanks in advance guys..

 

17 " Limited Rims (Chrome)

I went with 17s on my iroc and there is mucho rubbing. In fact my ground effects have been broken due to them (front of the side gfx). I have to make sure i do not turn to hard or I can hear it rubbing. I think 18s or 20s will even be more of a problem. I do have a 2" lowering springs all around.

I think that maybe once I have my sfcs, wonderbar, and stb in it may not be as big of a problem cause there will not be as much flex. I may also go with tubular A arms as well to work my way around this.

If your gonna put 18s or 20s on be prepared for problems and be prepared to spend lots of cash to avoid rubbing and breakage with them.

My 17s are big enough. Many people think they are 18s or 20s just by looking at them cuz they look huge.

Once I have installed all the parts mentioned above im replacing my side gfx with 91 camaro ground effects. I hope this will solve this problem.

Hope this helps.

 

what size of tires are you running and how wide? because you shouldn't be rubbing, more than likely your tires are too wide or too tall overall.

My logic seems right, but I'd like some real life experiences to back it up.

Because I should be able to run a 245/35/r20 tire because there are people have run 9.5" wide rims up front (ZR1's) with 275 tires, and a 245/35/r20 tire is 26.8" overall, and a my 16" tires are 25.7 overall. So that would only be 1 more inch taller, so figure 1/2 inch on each side closer to the ground effects and fender lip. And it seems like I have enough room to pull that off.

Do you guys think my reasoning is wrong?

 

Your reasoning is correct. The diameter of the wheel does not matter. The overall specs of the wheel and tire are what matter. You can go bigger than stock diameter, as long as you select the right size tires, you should have little to no change from stock as far as rubbing. Calculating height is easy but I think where it gets hard is when you get into the width because fitment there depends on the ride height and contours of the fenderwells. The wheel backspacing would also play into this. Lets use the 18's on my Z28 as an example. Stock 16's overall height is 25.65" tall, and 9.6" wide, tire is a 245/50/16 on a 16x8. I run a 245/40/18 tires on my 18's, puts the overall height at 25.72" and same width, very small difference from stock. I have the car dropped so low in the front the wheels/tires tuck under the fender and I do not have any rubbing issues, even at full lock. If I had gone wider or went with a more agressive backspacing, I might run into rubbing issues. I dont think anyone has documented exactly how tall and wide you can go front/rear before running into issues with contact. But there are so many other people running aftermarket wheels/tires with lowered ride heights, you can use their experiences to help you get close. What I would do in your case is find other members with the same ride height (other people running sportlines) and write down the tires they are running with no rubbing issues, and the backspacing and width of the wheels. Then calculate the overall wheel/tire height and width of the tires they are using, and use those specs to determine what size tires you're going to use. Then once you get as close as possible, make sure you're using similar backspacing on your wheels (which would depend on the width). Contrary to what most people think, 20's are not beyond the limit of being able to maintain close to stock overall dimensions. You can do it but how streetable it is would be the question. A 245/30/20 tire is around 25.79" tall and same width as OEM, so very close to OEM overall specs. If you are going wider than 245's then you might have to run smaller than 30 series tires. So depending on what you consider streetable, 25 and 30 series tire might not be a good choice. In that case you will have to go taller than OEM overall dimensions, which means you're going to be more likely to run into rubbing issues. I consider 1 inch taller or shorter quite a big change. I know when I went 1 inch shorter on my IROC-Z it made a noticable difference as far as chassis clearance.

 

CrazyH,

What BS are you running? I will be running a similar set up with 17"s soon, and a pro-kit Does 4.5 BS safely work for the front with an 8" rim With a 17" 255 tire? or will a 5.5 BS on a 10" rim work.

I'm ordering rims like tomorrow, any advice would be appreciated, I know you have alot of experience with different tire/wheel combos - Looking for more of a Road race stance.

Thanks

 

alright thanks for the advise there crazy hawaiian...So 1" is a big difference then? as far as backspacing, they are iroc wheels, so the backspacing is made for thirdgeners, not sure what it is, but I know the 20's are wider than 8 inches, i think they are 8.5"...

I wish i could talk to this guy about his car, but I have no idea on how to get ahold of him. He's running exactly what I would be running. (sportlines and 20" irocs)
http://www.cardomain.com/ride/403007/2

So I guess like what hawaiian said, could people with sportline springs or similar springs post their tire sizes and let me know if they are rubbing or not.

thanks guys...

 

27" and you'll have a tough time. 25.5-26" is really a good range to be in.

in the end it's all on the offset and rim width. 20's are heavy though, your ride will suffer and so will your power.

 

hmm...wish there were 19's out there cheap...

i should probably go with 18's, but everybody has 18's...

such a hard decision, but it seems that 27" is too tall, and you guys are very trustworthy, and I'm not gonna run anything smaller than that of a sidewall, because the ride quaility is going to be bad enough.

I guess I'll just have to be satisfied with some 18's all around..so with my ride height I shouldn't exceed anything taller than a 26" tire?

 

No problem guys. I'm running 4.5" backspacing on the front and the wheel is 8" wide. I wouldnt consider it a road race stance. I went with a very conservative backspacing because I wanted to experiment with dropping the car. The front wheelwells are a problem with extremely lowered cars because of the way they are contoured. So when I ordered my wheels I planned to use adapters in the future to perfect the stance w/ adjustable ride height, the wheel sits inset. Here is a picture that shows what I mean, look at the stance of the front wheel versus rear, eventually they will be the same:



That picture up there was when only the rear was dropped, the front still had an off-the-shelf Eibach spring (though the type is still under investigation). And here is what it looks like after being dropped:



Now all I need to do is finish my brake upgrade in the front since it'll affect offset, then measure and order adapters to get the perfect stance. Once its completed I'll measure for overall specs so people will know what specs to order to get the same stance w/ bolt on wheels no adapters.

At first I thought that cardomain car was Blue502's car but thats a different guy, dont think he posts here. Maybe leave him a message?

 

what if i did like what blue502 did, 18/20...and run like a 26" tire in the front, 26.8" in the rear, that would work...

just out of curiousity, how would a 20" rim affect power, like what kandy said? I know its more rotating mass, so when you get them spinning, they spin longer because of the momentum. But what are some other problems, and how big of a difference would it be?

 

The wheels and tires are unspring weight. So generally speaking, the more unspring weight you have, the less responsive the car will be. This is not necessarily the fault of the wheels being 20 inches, but more the fact that 20's are probably going to be heavier than smaller wheels. I have seen lightweight 3 piece 20's but those are very very expensive. Aside from that, the large diameter means you'll probably need small sidewall tires to maintain or attempt to maintain reasonable overall dimensions. For drag racing this is probably not optimal because the sidewalls of 25 and 30 series tires aren't going to flex at all. So you probably won't have as good traction from a stop as you would with smaller diameter wheels and larger sidewall tires. For handling, the smaller sidewall tires are optimal.

 

well what I plan on doing is having another setup of rims for the rear with DR mounted on them, so when i go to the track, i would run the drag radials. When i race, i don't prove myself on the street, I take it to a track, so street races aren't a big thing for me.

The most street racing i would do is like a 20 MPH roll on or something, and I don't see how stiffer tires would really affect this, because I'm not gonna tremendously break them loose at 20 MPH anyways...

anybody have any weight comparisons? like stock 16" with tires versus bigger sized irocs and tires?

 

my ride quality wasn't any worse with 245/35/19 versus 245/40/19. once you get away from a 16 with a 245/50 sidewall everything is rough. you can go taller, it just looks out of place and the overall dia is thrown off. stick the factory size. just change your measurements accordingly.

 

all can be found searching, i've gone over it numberous times. take a 2lb weight and swing it in a 1' circle. do the same with a 3lb weight and move up. it makes a difference.

now take a 8" rim or 245 width tire and push it down the street. do the same but with a 10" and a 285 wide tire. much more resistance. i lost roughly 30 horsepower switching from 18's to 19's. i couldn't imagine switching having heavy 20" cast rims.

 

alrighty...i guess the next question is where can i get a smaller tire? i found the kumho 245/35/20 and thats it. Who makes like a 245/30 or something?

 

alright i gotcha.. say roughly 50 horse at the max I would be losing? but I would get that all back when i switched to some 16's or something DR..and I guess thats all that matters..

 

So CrazyH, & Candied

Will a 17x10 work in the rear work/ look ok with 5.5 BS?

I'm ordering rims now and need to confirm what will work.

Love the way CrazyH's car sits. if I got the 10" rim with 5.5 I believe I'll only be .5 inches out further. would this rub? (I'll be using the pro-kit) should give a nice stance.


If any one knows for the front, will 4.5 BS clear Baer brake calipers?

Muchos Gracias......

 

as i said swing a weight. pick up a 5lb and swing it around your head, do the same with a 2lb. it's noticeable and of course this all relates to horsepower.

there are plenty of tire sizes for the 20" i'm running 245/35/19's myself though so to be comparable you would have to run a 245/30/20 which puts your sidewall pretty thin. better get tripple A insurance or invest in a truck and trailer. be sure to avoid all bumps in the road.

 

that's more his angle. my 18's i ran a 6.75 b.s with the 18x10" wheel and i'm running a 6.25 right now with my 19x10" 5.5 would definately rub with a 10" i would say.

also, i run a 13" track kit up front. i run 4.75 bs to compensate for the 1/4" the kit moves the hub out. everyone is different though. I can not stress how important it is to learn about the measurements and do it yourself. wheels are too expensive to go by someone elses measurments and all vehicles are different to some degree.

 

Kandied,

How's the fitment with the 6.25 BS? any inner wheel well contact/ any modification necessary?

I don't have the car with me so I can't measure right now ( getting paint)

off topic,

Did you like the bilstiens with the pro-kit or would you recommend a yellow Koni ( for the street)

Thanks-

 

i deal with koni every day, one of their representatives is a good friend of mine. i loved my bilstein hd's with the pro-kit. just a very nice setup.

as for fitment i don't want to be rude but i would appreciate it if you searched a bit, i've discussed all of my various wheel setups quite a bit here. i wouldn't run them if it didn't fit. 6.75 required modification as i had to remove the bumpstops and massage the support, 6.25 is fine however i do have to roll the fenders a little to set the car at a 3" lowering which i drive it at.

as i said, it all depends on the car and no two cars are alike. what works for me probably will not work for you, but it will guide you.

 

Kandied,


Thanks for your input, I've searched the crap out of this and there is tons of speculation , and very little hard and true fitment facts for rear sizes over 9.5 rear or fronts over 8.5 with no BFH mod or rolling the fender lips

As you said each car has its nuiances, and everyone has a slightly different opinion on what looks the best.

Again your insight is much appreciated
just digging all up all the info I can before I part with my hard earned cash.
-K

 

good idea.

 

well the weight issue just doesn't outweigh the 'look' the 20's will give me. So i guess i'm gonna polish up the 18" eagle 077's i have and stick with them for the time being. I picked one of the wheels up today, I can't believe how light those baby's are!!! lighter than my stock iroc 16's i believe. Maybe the 18's will help my performance..

But once 20" irocs or a similar wheel comes in polished aluminum, i'll be the first to buy them...

thanks for the help you guys...mucho appreciated.

 

CrazyHawaiian,
What brand of wheels are those? I'm planning to go with a similar style for my GTA in 17".

Thanks.

 

These are the rims i went with......i went with 17s even though you could get them bigger...check it out...

 

Those are the Boyd Coddington Tuned wheels.

 

I know they already have stretched iroc wheels with a polished finish up to 18", maybe 20's you'll have to look around.

To go with any bigger than an 18 you're gonna need a real big drop to make it look right in my opinion, big enough to the point that it's gonna make it a chore to drive around depending on where you live not only because of the drop but also the extremely small amount of side profile tire you'd need for it to look like it belongs. Unless you can afford bags I honestly don't think it's practical. But you're idea of what looks good and mine may not be the same. Good luck with whatever setup you end up going with man.

 

even 18 you need to. if your worried about the ride and height you need to stick to 17's or you won't pull it off right.

 

Hmmm, they don't show up on Boyd's Web site. Google has come up empty as well.

 

I'm pretty sure that's what they are but could be wrong. Maybe they don't offer them anymore? Hopefully he'll chime in here again.

 

Agreed. It's all about knowing what you're limits are. If he's able to make 20's look like they belong while still remaining reasonable then he should go for it. It depends on where you live and how much you can tolerate as far as driving goes as well. Honestly if I wanted to I could run a 19 or 20 with a decent drop and be fine due to the pretty friendly roads around here. But if you find yourself compromising the look because of driving conditions then you should really consider going smaller. Not to mention the weight savings.

 

Those wheels on my Z28 are the Boyd Coddington "Tuned" wheels. I dont think they are advertised anymore, but I can guarantee you they still have the molds. So if this is the style you want, give them a call and let them know. Be prepared to pay alot though, they used to be cool about doing custom stuff for cheap but nowadays they aren't as laid back (probably after the TV show success or what you want to call it). Here's another picture of the wheels from the side (so you can see the style better).