hilljackofdenile

I talked to a guy from a tire store about bigger tires and he said the biggest I can get are 265/60s on my 15" rim, but i have seen people with 275s on here, I was just wondering if I can get 275/70s on my 15x7" rims. I want the 70s because i have a 3 gear, automatic, non-lock up, non-overdrive transmission and the 3.73 rear gears, an 225/70s already so my highway RPMs are pretty high, and i dont want them to get any higher. does anyone know if i can do that?

hilljackofdenile

anyone?

[This message has been edited by hilljackofdenile (edited October 16, 2001).]

hilljackofdenile

anyone?

RB83L69

I've seen people jump off tall buildings too, but that doesn't mean it's the right thing to do...

When you put on a tire that's too wide fro a wheel, the tread is forced out of the shape it's designed to be in. The contact patch with the road isn't like it's supposed to be. The edges will never touch the road, so the tire will wear down the center.

275/70s are HUGE. That's about the size tire you'd put on a UPS truck or something.

It may seem hard to believe, but the gearing combination you have used to be pretty common... all sorts of older muscle cars came that way. All of my 69 Chevelle SS396s came with a T-400 and 3.73s, or a 4-speed (no OD) and 3.73s; to make matters worse, they came from the factory with 14x7 wheels, so about the biggest tire you could put on them was about a 225/60-14, which is smaller than what comes on an Accord today. My 70s Z28s all had T-350s or 4-speeds (again, no OD) and 3.73s; one of them even had (not factory) a 4-speed and 4.10s. At least those had 15" wheels. The bottom line is, there's no particular reason to put some goofy size tire on a car just because of that.

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"So many Mustangs, so little time..."
ICON Motorsports

hilljackofdenile

okay, yeah that makes sence, but does anyone know of a good tire size that wont mess up the tire, but still give good traction and decently tall?

hilljackofdenile

or if i were to get larger rims? does anyone know what a common upgrade is to the stock 15x7" rims? (wider and taller is better)

RB83L69

One real common upgrade is to get the 16s off of a newer / higher-performance car.

What kind of car do you have? I got 87 IROC wheels for my 83 Z28, 16x8 instead of the stock 15x7. If yours is a base model Bird or older T/A, you could get some wheels from a later model Formula or T/A with 16s.

Or, you could get a different rear or different gears.

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"So many Mustangs, so little time..."
ICON Motorsports

82camaro

225/70's are taller than stock and fit a 15x7 OK. 245/60 are as big as I would go on a 7 inch wide wheel. However, they are shorter than the 225/70's. If you want to reduce the highway rpm, change the gears or get an overdrive. Tires can only help so much.



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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

Dan87IROC-Z

What about on IROC rims, whats the biggest that can go on there and still be effective? Can I use 255s or 265s? Also, could I get a smaller diameter, like 40 or 35s even?

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Accel High Flow TPI Baseplate, Edelbrock TES 1 5/8" Headers, Catco 3" High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, Jet TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET: 14.32 @ 97.7mph
(corrected for elevation)

92blackbird

I run 245/60 15's on my stock cross lace wheels. fit well, speedo is spot on, and they look good.

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'92 firebird t-tops
305tbi,670cfm tbi, 2 1/2" Dynomax catback, 9x3 K&N open element

iroc5speed

I have 255/50/16s on my iroc wheels. work well,don't scrape the wheelwells or anything. I like them

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei distributer
'95 3.23 rearend
hotchkis rear suspension
PST front polygraphite suspension
"speed kills. buy a f@&d, live forever."

85 Berl

You'll have to get BIG tires to see any real difference in RPM's / mileage. I think 31's may fit with some minor sawzall work. HAHA!!! Just kidding. I think you'll come out better with an overdrive or taller gears. What are your RPM's now at 60MPH?

hilljackofdenile

lets see, i get about, i think, 3000 rpm at 60, but i dont think the speedometer was calibrated when the previous owner put on the taller tires. also, about how much would it cost to redo the rear gears?

[This message has been edited by hilljackofdenile (edited October 20, 2001).]

85 Berl

I've never really checked on it, but I think you can get it done for about $500. Check around in your area, and make sure the shop knows it's stuff. If its not set up right, it'll howl, and wear out quickly. You may want to check out a new rear. You can probably get a rear with disk brakes, and a posi for a little more than that. If you do get one with disks, get the proportioning valve from under the master cylinder, too. The one from a drum brake car wont work right.

stuart69427

what would be the biggest efficient rim size and what tires would I want to put on them?

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You know you drive an F-Body when you can't remember what the back of a Mustang looks like!

'88 Camaro Sport Coupe V6

zslug

Am I the only one here who's confused by the word, "big?" Are we talking about taller or wider or both or...???
If the question is how to decrease revs at highway speeds, then a taller tire is in order... but there goes the speedo accuracy.

My first thought here is to transplant a 700-R4 automatic, with O/D, which will decrease engine speeds in top gear and give you the added benefit of a lower 1st gear, giving a better launch as well. Then stay with a 26" diameter tire to keep your speedo accurate.

Fix your gearing problem with gearing, and select tires for handling, looks, and ride.

zslug

BTW, the 0.7:1 O/D on the 700R4 with a 3.73 rear gives you an effective final drive ratio in top gear of 2.61:1. There's your cruising gear!

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Zslug

May the road rise to meet your treads...

'84Z, 5sp, stock 305, Edelbrock intake, GTA wheels

IROC315

iTrader: (9)

I have 275/70's on 15x10 weld wheels.
I was more comfortable with 220's. The 275's offer great traction and fit the wheelwell good but are just too big.

poncho9789

The widest tire reccomended (safe) on a 15x7 wheel is a 275/60/15. I know I had them on my s-10