18x10.5 Square Set up with 285/35/18s
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Joined: May 2005
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
18x10.5 Square Set up with 285/35/18s
Car sticks a bit better now and looks a little bit better too.
Joined: Jun 2000
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From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
Transmission: T5, 700R4, T5, 700R4
Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: 18x10.5 Square Set up with 285/35/18s
what et?
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From: Leicester,Massachusetts
Car: 1983 CHEVROLET CAMARO Z28
Engine: Forged 355 with a GT45 turbo
Transmission: TKO 600
Axle/Gears: built 4th gen rear with 3.27s
Re: 18x10.5 Square Set up with 285/35/18s
looks good...saw this on FB
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Junior Member

Joined: May 2005
Posts: 56
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Joined: Jun 2000
Posts: 5,364
Likes: 51
From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
Transmission: T5, 700R4, T5, 700R4
Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: 18x10.5 Square Set up with 285/35/18s
56mm et with 2 inch spacers.. so basically an et of around 5mm. Does it clear the steering box brace in the fender?
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Junior Member

Joined: May 2005
Posts: 56
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
Total clearance in the front besides at full lock it rubs the inner fender well plastic which I expected. The rear I have KYB Excel Gs and they are just too soft so on the highway when you have a drop off I get a little rub as the car compresses. Going to put a stiffer shock in the rear hoping I don't have to roll the rear fender lips. Just got back in from a night drive, the car really sticks well though.
Joined: Jun 2000
Posts: 5,364
Likes: 51
From: Enschede, Netherlands
Car: 82 TA 87 IZ L98 88 IZ LB9 88 IZ L98
Engine: 5.7TBI 5,7TPI 5.0TPI, 5,7TPI
Transmission: T5, 700R4, T5, 700R4
Axle/Gears: 3.08, 3.27, 3.45, 3.27
Re: 18x10.5 Square Set up with 285/35/18s
Instead of just a stiffer shock use some u bolts to bolt a pad to the axle where the bumpstops contact. You cab easily adjust it so that the bunpstop contacts right before the wheel rubs.
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Joined: May 2005
Posts: 56
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
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Junior Member

Joined: May 2005
Posts: 56
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
So I just got back from a drive...after removing the 12 inch sub in the trunk and amp along with the spare tire and jack. Went over some bumps and no rub but waiting to get out on some of the highway ramps that have some of the dip drops that are more severe before saying it worked. Either way rear shocks are ordered and it will be a stiffer shock then the GR2. I knew I should have went with Konis as many advised. haha
Joined: Feb 2001
Posts: 8,494
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From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: 18x10.5 Square Set up with 285/35/18s
That's a sharp looking car!!!!!!!!!
Question about the clearance on the back. Could you have moved them in a little? Maybe used a 1.75" or 1.5" spacer instead of 2"?? I'm considering a similar set up and wouldn't mind tuckin' them in there just a smidge more.
Question about the clearance on the back. Could you have moved them in a little? Maybe used a 1.75" or 1.5" spacer instead of 2"?? I'm considering a similar set up and wouldn't mind tuckin' them in there just a smidge more.
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Joined: May 2005
Posts: 56
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From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
I believe I could have went with a 1.75 spacer in the back but doubt I could have went 1.5 without doing something to the inner fender wells.
Joined: Feb 2001
Posts: 8,494
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From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: 18x10.5 Square Set up with 285/35/18s
makes me wonder what the stock size was.
Joined: Aug 2006
Posts: 12,812
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From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: 18x10.5 Square Set up with 285/35/18s
The rears can move in a half inch and still clear. Just a little hammering of the front lower part as usual. I ran 18x10.5 with 17mm offset rear for some time on my 92.
Joined: Mar 2001
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Car: '89 Firebird
Engine: 7.0L
Transmission: T56
Re: 18x10.5 Square Set up with 285/35/18s
How fat a tire looks has a lot to do with where it tucks under the car. My 275 rear tire looks kind of skinny but it would look pretty fat if it was placed a little further inboard. And the cost of a 275/40-17 is way less than the 18s ( like half). I consume a set of rear tires in about 4 months driving on the street so the recurring cost adds up over time. In my case if I wanted a fatter look I would get a wheel with a different backspacing and stay with the more affordable 17-inch tire.
Joined: Jan 2002
Posts: 3,449
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From: LONDON, KY
Car: Camaro
Engine: Carbed L98
Transmission: TH350
Axle/Gears: 3.73
Re: 18x10.5 Square Set up with 285/35/18s
How fat a tire looks has a lot to do with where it tucks under the car. My 275 rear tire looks kind of skinny but it would look pretty fat if it was placed a little further inboard. And the cost of a 275/40-17 is way less than the 18s ( like half). I consume a set of rear tires in about 4 months driving on the street so the recurring cost adds up over time. In my case if I wanted a fatter look I would get a wheel with a different backspacing and stay with the more affordable 17-inch tire.
At what size / back spacing do they hit? This is one of the reasons I myself am looking at the 18's. This square setup looks like a great combination.
Joined: Feb 2001
Posts: 8,494
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From: Sophia, NC
Car: 2016 Camaro SS + 1986 Z28
Re: 18x10.5 Square Set up with 285/35/18s
LOTS of different variable...LOTS....but rule of thumb is max 5" backspacing up front and max 5.85" backspacing out back. ....but again....research and measure. No two cars are exactly the same, plus mods and aftermarket suspension and brakes, etc. etc.
Lots of good info here:
http://www.skulte.com/adapterfaq.html
Lots of good info here:
http://www.skulte.com/adapterfaq.html
Joined: Jan 2002
Posts: 3,449
Likes: 7
From: LONDON, KY
Car: Camaro
Engine: Carbed L98
Transmission: TH350
Axle/Gears: 3.73
Re: 18x10.5 Square Set up with 285/35/18s
LOTS of different variable...LOTS....but rule of thumb is max 5" backspacing up front and max 5.85" backspacing out back. ....but again....research and measure. No two cars are exactly the same, plus mods and aftermarket suspension and brakes, etc. etc.
Lots of good info here:
http://www.skulte.com/adapterfaq.html
Lots of good info here:
http://www.skulte.com/adapterfaq.html
Using a 18" wheel in front would remove the issue of hitting the tie rod end compared to the 17" wheels. One less obstacle to overcome. On the 18, the tie rod would be inside the wheel.
Is a 10.5 wide wheel in front beneficial for a daily/occasional driver? I can understand for autocross, but for everyday driving?
Dont get me wrong, I love the look, just trying to understand better.
Wider wheels would seem to put more stress on steering parts over time, but I could be wrong.
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From: Ahead of you...
Car: 1984 LG4 Camaro
Engine: 350 Roller Motor
Transmission: Level 10 700R4
Axle/Gears: Strange 12 bolt 3.42
Re: 18x10.5 Square Set up with 285/35/18s
You can run a 17" x 9.5" wheel with 5.25" BS and not hit the tie rods - I make them, so they work. There are other wheels in 17" that fit - but not all of them are 9.5" wide.
Yes, a square setup is best for all around performance - going staggered on a front heavy car will give the car mechanical understeer and hurt braking too.
Yes, a square setup is best for all around performance - going staggered on a front heavy car will give the car mechanical understeer and hurt braking too.
Joined: Mar 2001
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Car: '89 Firebird
Engine: 7.0L
Transmission: T56
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Joined: May 2002
Posts: 813
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From: Summerville, SC
Car: 91 RS Camaro
Engine: 305 TBI
Transmission: 700R4
Axle/Gears: 2.73
Re: 18x10.5 Square Set up with 285/35/18s
Penny for your thoughts.
I'm doing some research here and seen this post. I'm thinking about refreshing the look on a bone stock 91 RS that has 15" wheels/tires. I love the square look and used to have a 90 RS but never had the chance to get wheels.
From what I understand 18x9.5 might fit nice without much interference. My intention is to put 275/35/18s at all 4 corners. I have no idea yet on backspacing but do you think this is a viable solution?
I'm doing some research here and seen this post. I'm thinking about refreshing the look on a bone stock 91 RS that has 15" wheels/tires. I love the square look and used to have a 90 RS but never had the chance to get wheels.
From what I understand 18x9.5 might fit nice without much interference. My intention is to put 275/35/18s at all 4 corners. I have no idea yet on backspacing but do you think this is a viable solution?
Thread Starter
Junior Member

Joined: May 2005
Posts: 56
Likes: 0
From: Phoenix Arizona - Formerly OCNY
Car: Yellow 1985 Iroc and 1991 Z28 1LE
Engine: 305 and 350
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
Penny for your thoughts.
I'm doing some research here and seen this post. I'm thinking about refreshing the look on a bone stock 91 RS that has 15" wheels/tires. I love the square look and used to have a 90 RS but never had the chance to get wheels.
From what I understand 18x9.5 might fit nice without much interference. My intention is to put 275/35/18s at all 4 corners. I have no idea yet on backspacing but do you think this is a viable solution?
I'm doing some research here and seen this post. I'm thinking about refreshing the look on a bone stock 91 RS that has 15" wheels/tires. I love the square look and used to have a 90 RS but never had the chance to get wheels.
From what I understand 18x9.5 might fit nice without much interference. My intention is to put 275/35/18s at all 4 corners. I have no idea yet on backspacing but do you think this is a viable solution?
Joined: Sep 2002
Posts: 1,099
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From: Melbourne Australia but from South Carolina
Car: 1991 Trans Am convertible
Engine: 305 TPI
Transmission: Auto
Re: 18x10.5 Square Set up with 285/35/18s
Fast lenny: Is that using the standard backspacing? I am doing the same to my TA. Thanks.
Joined: Aug 2006
Posts: 12,812
Likes: 109
From: Central NJ
Car: 86 Trans Am
Engine: 408 stroker sbc
Transmission: TKO600
Axle/Gears: Moser full floater m9, 3:70 trutrac
Re: 18x10.5 Square Set up with 285/35/18s
Stock brakes and axle, I would run 5.5" Bs with an 18x9?5, front and back
Re: 18x10.5 Square Set up with 285/35/18s
I you have 18x10.5 front and they rub at full lock do you think that an 18x10 25mm backspacing would ive been looking this whole week cant find anyone running 18x10s in the front
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