how wide of tire on 18x9.5 rim? - Chevelle Tech
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post #1 of 11 (permalink) Old Jun 30th, 08, 8:55 PM Thread Starter
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mike
 
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how wide of tire on 18x9.5 rim?

Of the wheels I am considering the most the widest wheel they make are 18x9.5. What is the widest tire that that will fit. I was hoping to use the 305/45/18 nitto drag radial but that might be too much tire for 18x9.5. What do you guys think?
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post #2 of 11 (permalink) Old Jun 30th, 08, 9:04 PM
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Matt
 
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Re: how wide of tire on 18x9.5 rim?

Here is my logic:

305 is the width in millimeters, so divide by 25.4 to convert to inches. It equates to 12 inches wide.

Now your rim is 9.5 inches wide. That is measured where the bead of the tire goes, so add an inch and that is approximately how wide the rim is from edge to edge.

A 12 inch tire in a 10.5 total width rim will cause the tire to overhang past the rim .75 inch on each side. On a low profile tire like that, my opinion is that it will be a bit too much. The tire will have a 'pinched' look to it, rather than a squared off look.

You should shoot for a tire with a width of closer to 11 inches. 285mm would work.

1966 Chevelle, original 283/glide with 54k miles. 1987 Grand National, runs mid 10's with working A/C and cruise control.
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post #3 of 11 (permalink) Old Jun 30th, 08, 9:33 PM Thread Starter
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mike
 
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Re: how wide of tire on 18x9.5 rim?

Cool deal, that is what I thought. I will either have to compromise on my wheel choice to fit the bigger tire or go with a smaller tire.
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post #4 of 11 (permalink) Old Jul 1st, 08, 3:31 AM
 
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Re: how wide of tire on 18x9.5 rim?

http://www.chevelles.com/forums/show...01#post1679101

Post #21 show rear 18 x 9.5's w/ 305/45 Nitto DR's

Nitto actually recommends a 10" wheel

http://www.nittotire.com/#index%2Etire%2Ent555r%2Esizes
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post #5 of 11 (permalink) Old Jul 1st, 08, 10:04 AM
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Troy
 
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Re: how wide of tire on 18x9.5 rim?

Yep, check the manufacturer's spec. They will give the acceptable wheel widths for a given tire size, and they also list the wheel size the tire was mounted on when it was measured for section width.

If the spec lists 9.0-(10.0)-11.0 that means 9" is the minimum acceptable wheel width, 10.0" was the wheel that the tire was mounted on to take the section width & diameter measurement, and 11.0" is the maximum wheel width.

Mounting the tire on a wheel that is out of spec range will stress the sidewall beyond the manufacturer's tested and approved limits... you may have problems, you may not. Also remember that as you mount a tire on a narrower wheel you decrease the actual contact patch and the tire will have more "squirmy" and unstable sidewalls, and as you mount the tire on a wider wheel the contact patch increases and the sidewalls stiffen up.

The Nitto 305/45/18 you mentioned is rated from 9.5 to 11.5 per Nitto's spec sheet, so it would be OK to mount. Keep in mind that's almost a 29" tall tire though!

1969 Chevelle
Old setup: Procharged/intercooled/EFI 353 SBC, TKO, ATS/SPC/Global West suspension, C6 brakes & hydroboost.
In progress: TT LS2, T56 Magnum, watts link, Wilwood Aero6/4 brakes, vaporworx, floater 9" rear, etc.

Last edited by Gokou; Jul 1st, 08 at 12:45 PM.
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post #6 of 11 (permalink) Old Jul 1st, 08, 12:20 PM
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Ron
 
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Re: how wide of tire on 18x9.5 rim?

The 305's on a 9.5" does not look right to me. The sidewalls puff out way to much. I think the max that looks good on a 9.5" wheel is a 275.

69 Camaro
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post #7 of 11 (permalink) Old Jul 1st, 08, 12:32 PM
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Erik
 
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Re: how wide of tire on 18x9.5 rim?

On an 18" rim, 295 is the widest approved by the TRA (Tire and Rim Association) for a 9.5" rim (this is 2006 yearbook, so there may be some newer tires that are approved). Specifically: 295/45R18 (28.46" Dia.) or 285/40R18 (26.97" Dia.)

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post #8 of 11 (permalink) Old Jul 1st, 08, 12:47 PM
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Troy
 
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Re: how wide of tire on 18x9.5 rim?

Quote:
Originally Posted by ehjorten View Post
On an 18" rim, 295 is the widest approved by the TRA (Tire and Rim Association) for a 9.5" rim (this is 2006 yearbook, so there may be some newer tires that are approved). Specifically: 295/45R18 (28.46" Dia.) or 285/40R18 (26.97" Dia.)
True, but per Nitto's spec sheet the particular tire he is looking at is rated for a 9.5-11.0 wheel width range-- so he would be OK, appearance aside. Always err to the manufacturer's rating. Nitto's do tend to run a little narrower than other brands. My 285/40/17 Kumho's look and measure nearly as wide as a friend's 305/35/17 Nitto DR's, both mounted on 11" wide wheels.

1969 Chevelle
Old setup: Procharged/intercooled/EFI 353 SBC, TKO, ATS/SPC/Global West suspension, C6 brakes & hydroboost.
In progress: TT LS2, T56 Magnum, watts link, Wilwood Aero6/4 brakes, vaporworx, floater 9" rear, etc.
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post #9 of 11 (permalink) Old Jul 1st, 08, 2:28 PM
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Erik
 
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Re: how wide of tire on 18x9.5 rim?

For every 1/4" of rim size change from the designed rim width the tire section will change accordingly by about 0.1" (2.54 mm). So...a 285/40/17 is designed for a 10" rim and has a nominal section width of 290 mm. Add 10 mm (2.5 x 4/4ths) and the nominal section width on a 11" rim is 300 mm. A 305/35R17 tire is probably designed for an 11" rim. Again...my latest TRA Yearbook is 2006 and does not list that specific size.

Erik
'69 Chevelle Sport Coupe, EFI355, TH350
'68 Chevrolet C10 Stepside Project, 292, t-56, C4 IRS
'77 Chevrolet K20 Silverado LWB, 400CI, TH400
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post #10 of 11 (permalink) Old Jul 15th, 08, 12:58 AM
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Clint
 
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Re: how wide of tire on 18x9.5 rim?

My 93 Corvette 40th Anniversary came standard equipped with Goodyear 285/40/17 tires on its oem 17x9.5 wheels so GM obviously didn't think that width wheel was too narrow.
http://www.corvetteactioncenter.com/...3/93specs.html
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post #11 of 11 (permalink) Old Jan 15th, 16, 6:27 AM
 
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Re: how wide of tire on 18x9.5 rim?

hey guys just wanted to know if I can get some advice real quick.... I recently purchased a set of wheels, 18x8.5 front and 18x9.5 rear, im having some trouble with deciding the right tire size for my wheels. im interested in getting low profile tires and I want no stretch and if so a little bit of stretch. what size tires should I get? if anyone has an answer email me at chris.a_14@yahoo.com. please and thanks for the help.
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