[Z06] New wheels
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
It's a wheel problem in that sense, and a difference in opinion on what "good" wheel fitment is. For an 18x11 rear wheel, Forgestar is going to send you a +55 or +53 mm offset, and it's going to poke a little like you're seeing. It's popular and it's what most of their customers want. Also with a wheel that wide, there isn't room to tuck it inboard much more. When you have the wheels mounted and car on the ground, reach in and feel how much space is between the tire and rear brake duct to see what I mean. An 18x10.5 is easier to fit inside the fenders.
I just got my own new set of Forgestars and have the same issue even with -1.5° of camber in the rear. It isn't terrible and I'm going to live with it, because you can really only see it if you're looking for it. From most perspectives, it isn't noticeable, and that's why you don't see it in most pictures on the forum. It's true that if you lower the car and/or align in some negative camber, you can hide the poke to some extent. Otherwise, the fitment you have now is still going to get you plenty of compliments on Saturday mornings at Cars and Coffee.
I just got my own new set of Forgestars and have the same issue even with -1.5° of camber in the rear. It isn't terrible and I'm going to live with it, because you can really only see it if you're looking for it. From most perspectives, it isn't noticeable, and that's why you don't see it in most pictures on the forum. It's true that if you lower the car and/or align in some negative camber, you can hide the poke to some extent. Otherwise, the fitment you have now is still going to get you plenty of compliments on Saturday mornings at Cars and Coffee.
Burning Brakes
Joined: May 2014
Posts: 763
Likes: 215
From: Detroit
I have 20x11 +53 rears with 305/30-20 Advan Apex V601 tires. Can you post a link to the "no poke at all" pictures? I'm skeptical without seeing it because it's really easy to take a picture that hides the little bit of poke.
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
This pic was the. One that made me want 18 all around. I ordered off this image.
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
Burning Brakes
Joined: May 2014
Posts: 763
Likes: 215
From: Detroit
MotoJB posted that picture. He also started the thread and in the first post he wrote "My rears do not stick noticeably out past the fenders" and "Minimal Stick Out/Poke with 295's". That description suggests to me that he had the same little bit of poke, too. Then look at his pictures in post #15 which shows the poke.
Z06 Forgestar F14 Info & Pic Thread - CorvetteForum - Chevrolet Corvette Forum Discussion
Z06 Forgestar F14 Info & Pic Thread - CorvetteForum - Chevrolet Corvette Forum Discussion
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
MotoJB posted that picture. He also started the thread and in the first post he wrote "My rears do not stick noticeably out past the fenders" and "Minimal Stick Out/Poke with 295's". That description suggests to me that he had the same little bit of poke, too. Then look at his pictures in post #15 which shows the poke.
Z06 Forgestar F14 Info & Pic Thread - CorvetteForum - Chevrolet Corvette Forum Discussion
Z06 Forgestar F14 Info & Pic Thread - CorvetteForum - Chevrolet Corvette Forum Discussion
Burning Brakes
Joined: May 2014
Posts: 763
Likes: 215
From: Detroit
It's hard to say, but your tires look right for a 275 mounted on a 9.5" wheel. What are your old wheels and tires? That chrome or polished wheel wasn't stock on your car. The old tire definitely looks like it has more sidewall bulge which might account for the uneven level.
Also read this post, I think it might answer a lot of your questions.
Z06 Forgestar F14 Info & Pic Thread - Page 8 - CorvetteForum - Chevrolet Corvette Forum Discussion
Also read this post, I think it might answer a lot of your questions.
Z06 Forgestar F14 Info & Pic Thread - Page 8 - CorvetteForum - Chevrolet Corvette Forum Discussion
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Race Director
Joined: Jan 2000
Posts: 10,373
Likes: 3,385
From: Central TX
C5 of Year Finalist (appearance mods) 2019
Yes, it could be an alignment issue, especially if you haven't had it checked in a long time. If your front wheels have at least 7" of backspacing and the rears have 8.125", there's not a whole lot else it could be,
BTW, have you driven the car since installing the new wheels and tires so the suspension had a chance to settle?
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
It's hard to say, but your tires look right for a 275 mounted on a 9.5" wheel. What are your old wheels and tires? That chrome or polished wheel wasn't stock on your car. The old tire definitely looks like it has more sidewall bulge which might account for the uneven level.
Also read this post, I think it might answer a lot of your questions.
Z06 Forgestar F14 Info & Pic Thread - Page 8 - CorvetteForum - Chevrolet Corvette Forum Discussion
Also read this post, I think it might answer a lot of your questions.
Z06 Forgestar F14 Info & Pic Thread - Page 8 - CorvetteForum - Chevrolet Corvette Forum Discussion
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
I have not driven the car. Local shop said not to drive it. It just seem like they were poking so far out. I was mad and worried at Sametime. I know once a tire is mounted. There is no sending wheels back.
Le Mans Master
Joined: Jun 2016
Posts: 5,426
Likes: 3,974
From: Cincinnati, OH
So you did or did not 100% figure out what the offsets actually are?
There are a million calculators online to determine this stuff. I like this one:
https://tiresize.com/wheel-offset-calculator/
Oh and don't listen to whomever told you "not to drive the car" with wheels like that...You don't want to see what my 315 Front/335 Rear tires look like when I autocross.
There are a million calculators online to determine this stuff. I like this one:
https://tiresize.com/wheel-offset-calculator/
Oh and don't listen to whomever told you "not to drive the car" with wheels like that...You don't want to see what my 315 Front/335 Rear tires look like when I autocross.
Last edited by smitty2919; Jun 28, 2021 at 10:36 AM.
Le Mans Master
Joined: Jul 2011
Posts: 7,422
Likes: 969
From: Morristown New Jersey
Oldtimer
I’ve always liked bigger tires but there are limits, especially for the street. I don’t like for a sports car to look like Jeep and vice versa. You mentioned TSW wheels. I have Nurburgrings and the offset is very close to stock. I have a coupe but when I found my stock wheels were cracked I went to C5Z sizes. I also strongly believe that GM engineers knew what they were doing especially in the realm of steering geometry. I would never consider changing camber just to accommodate the appearance or to relocate the position of a wheel that has incorrect offset. Remember that offset can also change the leverage on the bearings.
I strongly urge you to glean all the stats you can: stock offset/backspacing and the same for the wheels you have. Then go to tiresize.com with that info. It will give you a VISUAL and statistical view of the effects of the various numbers.
Following pix are of my car with 18/10.5 wheels on the rear with 295 tires. One pic is from as vertical as I could estimate, the other a few inches to the left.
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
So you did or did not 100% figure out what the offsets actually are?
There are a million calculators online to determine this stuff. I like this one:
https://tiresize.com/wheel-offset-calculator/
Oh and don't listen to whomever told you "not to drive the car" with wheels like that...You don't want to see what my 315 Front/335 Rear tires look like when I autocross.
There are a million calculators online to determine this stuff. I like this one:
https://tiresize.com/wheel-offset-calculator/
Oh and don't listen to whomever told you "not to drive the car" with wheels like that...You don't want to see what my 315 Front/335 Rear tires look like when I autocross.
Le Mans Master
Joined: Jun 2016
Posts: 5,426
Likes: 3,974
From: Cincinnati, OH
The shop I bought the wheels and tires from. They are the ones that said not to put miles on the tires. Stickers would have to be on tires if I wanted to swap tires. I believe that the front tires are the wrong size. I think they should be 265/35 for a 9 inch wide wheels. I thought i was getting 9.5 inch wide. So I ordered 275/35. I will use that calculator when I get home from work. Been a year or two since I did algebra. Maybe I did the math wrong.
Stock C5Z
Front:
Wheel size: 17 x 9.5
Offset: +54mm
Tire Size: 265/40/17
Back Spacing: 7.38” (187.35mm)
Rear:
Wheel size: 18 x 10.5
Offset: +58mm
Tire Size: 295/35/18
Back Spacing: 8.03” (204.05mm)
So I think you said you had an 11" wheel with 8.125 BS? That equates to a +54 offset. Since the stock wheel is 10.5" +58 and new one is 11" +54 that puts new wheel 0.16" further outward. Keep in mind you are measuring to a tire sidwall bulge in which not all tire widths across all brands are the same. So that COULD account for some of your visual "poke".
Thread Starter
Racer
Joined: May 2011
Posts: 412
Likes: 19
From: Shawnee oklahoma
Offset on rear wheel is 51mm according to online calculator. Fronts are 44mm. This is without the tire bulge. I cut something to fit on the flange. To get more accurate measurement.
Le Mans Master
Joined: Jun 2016
Posts: 5,426
Likes: 3,974
From: Cincinnati, OH
https://www.1010tires.com/Tools/Whee...et-Calculator#
This says your 11" wheel +51 will stick out 13mm more than 10.5" +58 which is about 1/2"
This says your 11" wheel +51 will stick out 13mm more than 10.5" +58 which is about 1/2"