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Old 12-06-2018, 03:53 AM
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Rim sizes/info/experience?

Hi all
I was looking into buying new rims for my 86 s/c. I saw these on Amazon and really liked them. However I dont know to much about the numbers and sizes listed. Id really like to get 17x7 (is 7 inches the average tire width?) for the front then maybe 17x9 (or 18x9) for the back (Im hoping to avoid over steering.. i was told getting wider back tires would help). On the amazon listing, there are other numbers and such in which I dont know what they mean, I was really hoping someone could tell me what all the numbers mean?
For example: 5 holes X100 millimeters pitch circle diameter X35 millimeters item offset X5.88 inches wheel backsp...
Aside from that, does anyone have any experience with these rims? I really like them. They look "casual", not really flashy or crazy yet they are obviously after market. I would love some reviews about these! Thanks!
Amazon Amazon



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Old 12-06-2018, 04:25 PM
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Re: Rim sizes/info/experience?

Read this, then come back and ask about whatever questions you have. I've had this link on my PC for YEARS!
http://www.skulte.com/adapterfaq.html

As for sizes, you're best bet is a square set up. Same size tire on all four corners. -except maybe for drag racing. PLUS....makes rotating them a lot easier. Still, some guys REALLY want to cram as big a tire as humanly possible out back, and that's cool too. It's all good if that's what you wanna do, but there's really no NEED for it.

As for stock sizes, for our cars, I think the vast majority are either 15x7 and 16x8. 16x8 runs a 245mm wide tire, and it looks and performs well. If you're looking to go bigger in diameter, I really wouldn't go any less than 17" or 18" x 8" wide. MANY repop wheels are that size and you can still run a 245mm tire. That being said, going to a 9"or 9.5" inch wheel allows running a 275mm tire, which may very well be the most common bigger size that guys are running. Good looks, good performance. Lots of wheels out there, lots of tires, and we know they fit, assuming the backspacing is correct. Fwiw, A 275/40/17 tire was stock on the 4th gen SS and WS6 cars.

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Old 12-06-2018, 04:58 PM
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Re: Rim sizes/info/experience?

...and for future reference, and for possibly better response.....we actually HAVE a wheels and tires forum!
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Old 12-06-2018, 06:01 PM
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Re: Rim sizes/info/experience?

Originally Posted by Abubaca View Post
Read this, then come back and ask about whatever questions you have. I've had this link on my PC for YEARS!
http://www.skulte.com/adapterfaq.html

As for sizes, you're best bet is a square set up. Same size tire on all four corners. -except maybe for drag racing. PLUS....makes rotating them a lot easier. Still, some guys REALLY want to cram as big a tire as humanly possible out back, and that's cool too. It's all good if that's what you wanna do, but there's really no NEED for it.

As for stock sizes, for our cars, I think the vast majority are either 15x7 and 16x8. 16x8 runs a 245mm wide tire, and it looks and performs well. If you're looking to go bigger in diameter, I really wouldn't go any less than 17" or 18" x 8" wide. MANY repop wheels are that size and you can still run a 245mm tire. That being said, going to a 9"or 9.5" inch wheel allows running a 275mm tire, which may very well be the most common bigger size that guys are running. Good looks, good performance. Lots of wheels out there, lots of tires, and we know they fit, assuming the backspacing is correct. Fwiw, A 275/40/17 tire was stock on the 4th gen SS and WS6 cars.
Thank you so much for the info! I did look at the link and found the amount of info a bit overwhelming.
You listed" 275/40/17 " what does the 275 represent? Also what's does the 40 represent? I posted the link to those rims above.. I've got a 86 camaro sports coupe
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Old 12-06-2018, 08:17 PM
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Re: Rim sizes/info/experience?

275 is width in millimeters.
40 represents the aspect ratio, which determines the sidewall height. It's expressed in percentage of width, or in this case 40% of 275mm. (which happens to be 110mm)
17" is of course the diameter.

Why the tire isn't simply a 275//110/17 tire is beyond me. Math is math, there is no grey area. 40% of 275 will ALWAYS be 110. Not sure why they don't just say 110.

But the magic here is overall tire and wheel diameter combined. Need to know THAT too, right? If you don't know exactly how and why you're changing overall heigh, best to leave it alone. ....and that 275/40/17 and the 245/50/16 are both right there at the stock 25.6" tall diameter. Doesn't mess with gearing, doesn't change speedometer calibration, and you know it fits and looks good.

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Old 12-06-2018, 08:38 PM
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Re: Rim sizes/info/experience?

The exact scale is NOT accurate. Kinda wanted to exaggerate the differences, but show the same overall diameter.

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Old 12-06-2018, 08:46 PM
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Re: Rim sizes/info/experience?

As for bolt circle, "we" use a 5 lug on a 4.75" bolt circle. In mm, math says 120.65, but in wheels, that'll mean 120.7mm bolt circle. I did NOT see on of those listed for those wheels.

EDIT*** so I've done some more reading, and I can find sources showing both 120.7mm and 120mm as equivalent to 4.75". Our cars are 4.75" and any wheel in mm wouldn't be made specifically for our cars. Doesn't mean it won't fit perfectly, just means it wasn't built specifically for our cars. That being said, if it doesn't list the bolt circle as 4.75", I'm honestly not sure which is ideal, or if it even matters. Maybe someone will chime in with the answer.

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Old 12-06-2018, 09:28 PM
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Re: Rim sizes/info/experience?

Here's a chart showing how backspacing and offset work. They're related, but are technically different. -and based on a given application, and wheel and tire size, sometimes one doesn't tell the whole story, especially when you start trying to cram REALLY wide wheels and tires in a car not originally designed for big wheels.

See how the 4th gen wheel has a higher offset? That's common nowadays. Allows for bigger brakes and more clearance etc. etc. Imagine putting those on your stock rear axle. From the back, the width of each wheel and tire would still be the same, but the entire width would be less. The wheels would sit inside more. You can make up for this with adapters to compensate for appearance. With a stock 16" wheel and 245mm tire, a 4th gen wheel would probably fit just fine on a thirdgen rear end, it may just look a little weird. ...but when you start going to a 9" wide wheel with a 275mm tire, you might scrape, and with a 10" wheel or bigger, cramming bit 315mm tires! -no way. They physically wouldn't fit. They'd hit the inner wheel wells for sure. -BUT, you can add an adapter. VERY common. In fact that's what that link I gave you is actually for. A 1.5" to 2" adapter is VERY common.

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Old 12-06-2018, 09:32 PM
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Re: Rim sizes/info/experience?

Important to note on the diagram above. Look at the left wheel with "0" offset. That means the mounting face is perfectly centered in the wheel. On an 8" wheel that should mean 4" offset right? From the middle to the edge of an 8" wheel should be 4", but it's not. The advertised wheel width doesn't account for the lip, but the backspacing does. You can see the 8" measurement for width, and see how the lip actually extends an additional .35" inches. If you laid a tape measure across our 8" wide Iroc wheels, it's actually measure 8.7"! ....this isn't hugely important on our wheels, but for trucks with big ole hoops it can be important.
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Old 12-06-2018, 09:40 PM
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Re: Rim sizes/info/experience?

So what are you looking for?
Diameter? Up to you. I like 17". 18" is very common for looks and performance. 19" and bigger starts to be more of a niche market, but hey, it's your car.
Width. 245 on an 8" is stock. Probably the single most common upgrade size is a 275mm on a 9 or 9.5. Looks, availability, performance, and we know they fit. Bigger will work, but do your homework.
Bolt circle. 5 lug on 4.75" or 5 lug on 120.7mm ***EDIT - I can't confirm if 120mm or 120.7mm is ideal, or if it even matters
Backspacing. Stock is 0 front, 16mm rear. This is ideal, but hard to find, depending on where you look. 1.5" adapters (about 38mm) and 2" adapters (about 50mm) are readily available and used to make up for differences.

LOTS of guys run various GM wheels from F bodies and Corvettes. Easy to find wheels that fit. SOOO many options though. Just gotta look.

Last edited by Abubaca; 12-06-2018 at 09:53 PM.
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Old 12-06-2018, 10:27 PM
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Re: Rim sizes/info/experience?

I'm super confused and overwhelmed with all this info haha can someone give me a size I could use to buy rims? I'd like 18" x 8 or 9. I don't know about the mm either .. I could really use the help! Thanks you all
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Old 12-06-2018, 10:57 PM
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Re: Rim sizes/info/experience?

It is a lot, but it's important.

I can't tell you what size. Stock performance for a 3rd gen was 16"x8", running a 245/50/16 tire. Honestly, I LOVE stock 16" Iroc rims on an SC. Not a bad choice. After that, I mean, 17x9 or 18x9. Stick with 275mm width, and go either 275/40/17 or 275/35/18. Both are 275 wide, both are 25.6 tall. one just has more tire, one has more wheel. You HAVE to have a 5 lug on 4.75"bolt circle, so no real choice there. ...then backspacing/offset. Honestly, find a wheel, then come back and ask.

What are you doing with the car?

As I mentioned, it IS a lot, but it's important. Look at stock 3rd and 4th gen wheels. Look at c4,5 and 6 corvette wheels. Look on Hawk's Motorsports site at what they offer. Sooooooo many wheels out there. If you want a list of wheels made for our cars nice and simple.....you have like 5 choices, lol! OK, more than that, but still. Beyond that.....if you don't understand what all the numbers mean, you'll never know what works.
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Old 12-07-2018, 12:04 PM
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Re: Rim sizes/info/experience?

Currently the car sits in my driveway. I'm in the process of restoring it. It doesn't turn on all the way and ive figured it's the fuel pump. So I still need to Replace that. But rims and wheels are one of my last stops (or very soon because I can't stand the wheels I have now). The ones I've found on amazon have many amazing reviews and I love how simple they are. If you go on Amazon and search the rim brand, many sellers sell the same kind of rims. So I'll have to search through those and I may be able to find the right kind!
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Old 12-07-2018, 03:19 PM
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Re: Rim sizes/info/experience?

Look on discount tire or tire rack website or any other online wheel/tire store. You can punch in your car and then when shopping for wheels select 18's. This will give you a safe wheel that fits the car with no interference. Or go by a local store if you buy a tire wheel package from a local store typically they don't charge you to mount them so it can end up being cheaper in the long run.

Honestly for street driving and over steer if you like your current wheels put the money into better tires. Your going to end up with a set of $400 rims and $1000 tires if you go to 18x9.

Take a look here also:
https://www.hawksmotorsports.com/82-...brakes/wheels/

once you look through what these websites says fit your car you should have an idea on the size, offset, and backspacing you need. A lot of people running oversized wheels and tires just live with scrubbing.

this particular wheel has all the info on the size on it https://www.hawksmotorsports.com/gta...free-shipping/
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Old 12-07-2018, 05:21 PM
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Re: Rim sizes/info/experience?

Thanks for the reply. Are tires really that much more expensive?! $1000.... I really can't afford that. I was told they would be about $100 per tire! I'm starting to think... My best bet is to find used rims and tires.. Because I can't afford this lol
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Old 12-07-2018, 05:54 PM
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Re: Rim sizes/info/experience?

The tire has way more to do with traction than the tire size (with in reason) yes you can get tires for $100 each for the 18x9 inch wheels but they will have no better traction than the $100 a tire 16x8 inch wheels (ok well marginal improvements when pushed to the limit because of sidewall deflection). My point being buy the wheels if you like the styling, buy nicer tires for your existing rims if you want better traction.

People oversize the wheels because 1: you can buy better tires for the larger sizes because they are more popular. 2: in certain cases because of supply/demand economics the more popular sizes have nicer tires at a slightly cheaper price. 3: when pushed to the limit and everything else being equal less sidewall height equals better traction (for driving curves doesn't apply for off road or drag racing). 4: they put bigger brakes on the car and the smaller wheels will not clear the rotor/caliper.

Buying bigger wheels and cheap tires is going to disappoint if you really are trying to solve traction issues. You can go with a slightly wider tire with your existing wheels, I'm not going to get into sizes though go to a good tire store and ask what the widest tire they can fit onto your wheels/car.

FWIW wheels off most GM/Chevy trucks from the 80's and early 90's will most likely fit, assuming they are not 4x4 as those have a larger center hole (not to introduce another variable). Wheels off corvette and 4th gen bodies fit with around 2" spacers. I dislike spacers, they put extra strain on the bearings, they mess with the track of the tires when turning, and if you have ever had one break... well no need to explain that one.

Go to tirerack.com put in your car info and look at the price of the tires. (wow this one is on a huge sale https://www.tirerack.com/wheels/WheelCloseUpServlet?target=runWheelSearch&initialPartNumber=LG32478610GMF&wheelMake=Hurst&wheelModel=Dazzler+17x8&wheelFinish=Machined+w%2FGold+Accent&showRear=no&autoMake=Pontiac&autoModel=Firebird&autoYear=1989&autoModClar=&packageSearch=true) and get soemthing likeBFGoodrich g-Force comp2 tires mounted and balanced the entire package is 616.57 + tax... humm almost tempting LOL except they only have 2 instock
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Old 12-07-2018, 06:23 PM
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Re: Rim sizes/info/experience?

Originally Posted by Aviator857 View Post
The tire has way more to do with traction than the tire size (with in reason) yes you can get tires for $100 each for the 18x9 inch wheels but they will have no better traction than the $100 a tire 16x8 inch wheels (ok well marginal improvements when pushed to the limit because of sidewall deflection). My point being buy the wheels if you like the styling, buy nicer tires for your existing rims if you want better traction.

People oversize the wheels because 1: you can buy better tires for the larger sizes because they are more popular. 2: in certain cases because of supply/demand economics the more popular sizes have nicer tires at a slightly cheaper price. 3: when pushed to the limit and everything else being equal less sidewall height equals better traction (for driving curves doesn't apply for off road or drag racing). 4: they put bigger brakes on the car and the smaller wheels will not clear the rotor/caliper.

Buying bigger wheels and cheap tires is going to disappoint if you really are trying to solve traction issues. You can go with a slightly wider tire with your existing wheels, I'm not going to get into sizes though go to a good tire store and ask what the widest tire they can fit onto your wheels/car.

FWIW wheels off most GM/Chevy trucks from the 80's and early 90's will most likely fit, assuming they are not 4x4 as those have a larger center hole (not to introduce another variable). Wheels off corvette and 4th gen bodies fit with around 2" spacers. I dislike spacers, they put extra strain on the bearings, they mess with the track of the tires when turning, and if you have ever had one break... well no need to explain that one.

Go to tirerack.com put in your car info and look at the price of the tires. (wow this one is on a huge sale https://www.tirerack.com/wheels/Whee...ageSearch=true) and get soemthing likeBFGoodrich g-Force comp2 tires mounted and balanced the entire package is 616.57 + tax... humm almost tempting LOL except they only have 2 instock
So. . I can't do math.. It's too Cold to run outside and measure my wheels... Can some please tell me what to buy? By this I mean size... I'm hoping for 18x8. I don't know about mm or anything else. I figured to ask for the size to buy just so I don't waste other people's time.
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Old 12-07-2018, 06:41 PM
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Re: Rim sizes/info/experience?

18 inch wheel that should fit
https://www.carid.com/american-racin...-28681400.html

Put in your car info but based on that sites info the tire would be:
245/40/zr18 and the wheel would be 18x8, 0 offset, 5x120.65 bolt pattern, 83.06mm hub, it doesn't list the backspacing but its probably

But the tire stores have to be conservative you can fit a 18x9 with 275/35/18 -- I'm guessing with a 9 inch wheel based on the internet information you would want +12 offset and 5.5" backspacing but I'm not 100% positive on that.

Last edited by Aviator857; 12-07-2018 at 07:10 PM.
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