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9" vs. 9.5" with 275 tires

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Old Apr 3, 2006 | 02:29 PM
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From: Readsboro, VT
Car: 85 IROC-Z / 88 GTA
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9" vs. 9.5" with 275 tires

A lot of the wheels I'm looking at only come in a 9.5" width instead of the 9" that I was looking for. How do the 275s work on a 9.5" wheel? Do they look ok? I'm not into that stretched out tire look that I see all too often.
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Old Apr 3, 2006 | 02:52 PM
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It will look fine. You'd have to run something like a 10.5 or 11 to do that with a 275.
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Old Apr 4, 2006 | 03:16 AM
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From: Changing Tires
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Here's a picture of a 275/35/18 on a 18x9.5 on the rear

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Old Apr 4, 2006 | 07:03 AM
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From: Albany, NY Area
Car: Red on Red 89 RS
Engine: LO3 305 TBI
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Crazy... could you tell me all of the measurements of those wheels? They look like they belong on the car. All of the other 3rd gens I've seen the back wheel sticks out.

I'm looking into a set of 18's...

I need to know (for front and rear):
Size & Width (already know the back is an 18x9.5)
Backspacing & Offset
Tire size (already know the back is 275/35/18)

Also... how much did you lower the car? It has a great stance!
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Old Apr 4, 2006 | 01:49 PM
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From: Changing Tires
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For the 18x9.5 in the back there its a 5.5" backspacing with 0mm offset (no offset specified). I ran a different setup in the front because of brake mods I plan to do in the future (and also being unsure about fitment with the ride height I want in the front). In that picture up top its Eibach Sportlines in the front and custom setup in the rear (ground control weight jacks w/ 10" spring adjustable height). The same 18x9.5 with 5.5" backspacing would fit on the front and be flush but depending on the ride height you might have rubbing. I put it on the front once for giggles, was not able to lower the car as much as I wanted. These days the front is also a custom setup w/ weight jacks and 10" spring adjustable height. Here's a more recent picture of the ride height (its slammed!!)

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Old Apr 4, 2006 | 02:33 PM
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From: Albany, NY Area
Car: Red on Red 89 RS
Engine: LO3 305 TBI
Transmission: TH-700R4
Axle/Gears: 10-bolt / 2.73
What backspacing would you reccomend for the front wheels? I plan on dropping the car 1.6" with 18's. I want to use an 8.5" wide wheel in the front. The only brake mods I am planning will actually fit behind a stock 16" IROC Wheel. I noticed all of your cars are slammed, I'm sure you have plenty of experience with lowering & big wheels.
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Old Apr 4, 2006 | 03:12 PM
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Car: Pair of 92 Z28s
im about to mount 285s to a 9" rim...
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Old Apr 4, 2006 | 05:47 PM
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From: Changing Tires
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Check out this thread for more info on wheel fitment, it has alot of good info. For a 8.5" wide I would copy ROH's specs, 4.5" backspacing with -7mm offset.

https://www.thirdgen.org/forums/susp...ighlight=wheel
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Old Apr 4, 2006 | 09:42 PM
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275/40/17's look fine on a 9.5 wheel. I'll post pics on ne3g when i put the pair on the TA
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Old Apr 5, 2006 | 09:59 AM
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From: Readsboro, VT
Car: 85 IROC-Z / 88 GTA
Engine: 403 LSx (Pending) / 355 Tuned Port
Transmission: T56 Magnum (Pending) / T5
Axle/Gears: 3.42 / ?
Thanks for the info guys. I guess I could live with how the tire looks on Crazy Hawaiian's car, though it's still not ideal to me. It may be less noticable on a 17" wheel too.
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Old Apr 5, 2006 | 10:44 AM
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From: Changing Tires
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If you can only get 9.5 and you think the 275 looks stretched maybe consider going with a wider tire 285 or 295 on the same 9.5" to get the look you want. Here's a pic of 275/40/17 on 17x9.5 on the rear (this is when I first got my Z28)

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Old Apr 5, 2006 | 11:47 AM
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From: Readsboro, VT
Car: 85 IROC-Z / 88 GTA
Engine: 403 LSx (Pending) / 355 Tuned Port
Transmission: T56 Magnum (Pending) / T5
Axle/Gears: 3.42 / ?
that pic looks totally different than the 18". The tire has a nice squat and is visually wider than the rim, which is what I'm after. On the pic of your 18", it looks like the wheel is the widest thing.

My concern with a 285 or 295 is that it'll be too wide to fit within the wheel well. I don't want anything sticking out farther than stock, or at least not too far that rolling the inner fender can't give adequate clearance.
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Old Apr 5, 2006 | 01:46 PM
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From: Changing Tires
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Maybe its the pics or something. When either wheel was dismounted and you stand over it and look down you couldnt see the rim lip. I dont think it looked stretched but its a personal opinion. I think around a 255 or 265 on a 9.5 it starts to look stretched but very minor, again just an opinion. I've had 225's on a 9.5 now that was an extreme stretch hahaha. Here's another pic that might help, again with the 18's (ignore the front wheel, focus on the back)



You could definately get 285's or 295's under there with no issues, the key will be in the backspacing. Some guys are running 315's on the back of our cars but it's a little too close for my comfort.
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Old Apr 5, 2006 | 01:57 PM
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Car: 82 Z28
Engine: Al LT1 headed LG4 305
Transmission: TH350
Axle/Gears: 3.73 posi with spacer
Corvettes come stock with 245/45-17 on 8.5x17 in the front and 275/40-18 on 9.5X18 in the rear so it will be fine.
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Old Apr 5, 2006 | 03:33 PM
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From: Readsboro, VT
Car: 85 IROC-Z / 88 GTA
Engine: 403 LSx (Pending) / 355 Tuned Port
Transmission: T56 Magnum (Pending) / T5
Axle/Gears: 3.42 / ?
Originally Posted by CrazyHawaiian
Maybe its the pics or something. When either wheel was dismounted and you stand over it and look down you couldnt see the rim lip. I dont think it looked stretched but its a personal opinion. I think around a 255 or 265 on a 9.5 it starts to look stretched but very minor, again just an opinion. I've had 225's on a 9.5 now that was an extreme stretch hahaha. Here's another pic that might help, again with the 18's (ignore the front wheel, focus on the back)



You could definately get 285's or 295's under there with no issues, the key will be in the backspacing. Some guys are running 315's on the back of our cars but it's a little too close for my comfort.
I can get a 295 to tuck without rubbing? I thought 275 was the max without a BFH? A lot of the wheels I've been looking at only offer an 8" or 10" width, but I haven't even considered using a 10" wheel because I thought anything bigger than a 275 wouldn't fit well.
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Old Apr 5, 2006 | 03:50 PM
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Car: 82 Z28
Engine: Al LT1 headed LG4 305
Transmission: TH350
Axle/Gears: 3.73 posi with spacer
Crazy's got the nicest car, it is the best look thirdgen i have ever seen. The only thing that i don't like is the tuned port injection and z28 badges. I think it would look much cleaner without. But hey that me and i'm
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Old Apr 5, 2006 | 06:48 PM
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From: Albany, NY Area
Car: Red on Red 89 RS
Engine: LO3 305 TBI
Transmission: TH-700R4
Axle/Gears: 10-bolt / 2.73
Originally Posted by Jim85IROC
I can get a 295 to tuck without rubbing? I thought 275 was the max without a BFH? A lot of the wheels I've been looking at only offer an 8" or 10" width, but I haven't even considered using a 10" wheel because I thought anything bigger than a 275 wouldn't fit well.

I had 295's on 15's on my last Camaro with no rubbing... if that helps
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Old Apr 5, 2006 | 10:20 PM
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Originally Posted by Jim85IROC
I can get a 295 to tuck without rubbing? I thought 275 was the max without a BFH? A lot of the wheels I've been looking at only offer an 8" or 10" width, but I haven't even considered using a 10" wheel because I thought anything bigger than a 275 wouldn't fit well.
Depends on what you consider "tucking". You can go 10" with a 295 as long as you dont order any more than I'd say 6" of backspacing depending on how low you are.

Here is an 18x10" with 6.0 backspacing on 285's..no rubbing.



From what I've been told he has between .25" and .5" more space to work with before rubbing becomes an issue..so 295 is possible with a 6" backspacing. You could go with a 5.75" backspace to be safe but in my opinion the wheel will stick out too far and look tacky.

When I order my wheels I will be getting 18x9" rear with 275/35 and 5.5" of backspace. They won't stick out any farther than stock wheels and won't rub either.

For the record..just because a wheel company doesn't list a 9" on their site doesn't mean they don't make them, shoot them an email or give them a call.

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Old Apr 6, 2006 | 05:03 AM
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From: Changing Tires
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Yeah Jim, you can get 295's under there. Check out that link I posted for jimp2001 on the wheel fitment, there is alot of information as well as pictures in that thread. Hey ME Leigh, thanks for the props man. Its funny you mention that stuff because when I do my next round of exterior mods on that car I plan to remove the tuned port injection decal as well as the Z28 decal and have the spot for the Z28 decal filled in and smoothed. The car is gonna be completely smooth w/ no decals or moldings hehe.
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Old Apr 7, 2006 | 12:42 AM
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Car: 86 LG4 & 92 TBI Firebird
Engine: The Mighty 305!
Transmission: 700R4
Axle/Gears: 3.42
Here's 275s on a 9.5" rim. Also 245 on a 8" rim.
Attached Thumbnails 9" vs. 9.5" with 275 tires-tires.jpg  
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Old Apr 7, 2006 | 08:28 AM
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From: Readsboro, VT
Car: 85 IROC-Z / 88 GTA
Engine: 403 LSx (Pending) / 355 Tuned Port
Transmission: T56 Magnum (Pending) / T5
Axle/Gears: 3.42 / ?
Originally Posted by Justins86bird
Here's 275s on a 9.5" rim. Also 245 on a 8" rim.
Which is which? I see 4 different tires in the pic.
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Old Apr 7, 2006 | 07:35 PM
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From: Another world, some other time
Car: 86 LG4 & 92 TBI Firebird
Engine: The Mighty 305!
Transmission: 700R4
Axle/Gears: 3.42
Originally Posted by Jim85IROC
Which is which? I see 4 different tires in the pic.
Lol, the ones on the bright red firebird are the 245s.
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Old Apr 9, 2006 | 07:26 PM
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From: West Springfield, MA
Car: '88 IROC-Z
Engine: StealthRammed 355
Transmission: 700R4
Any idea what 275s would look like on a 17x8 wheel? I am thinking about going with the SLP 3rd-gen specific ZR1s and would like to go with something wider than factory, but don't want to get the look of way too wide of a tire mounted on the rims.
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