wheels & tires
 

I have a 69 GTO and I want to increase my ground clearence .
I am running ralley 2- 14x7 wheels with 245/60/14 tires.
I will be needing new tires soon and want to know what would be the tallest and widest tire I could use on the car with out tire rub.
OR
I have 2-ralley 2 wheels 15x8 and could buy 2 more and buy new tires for those wheels but still need to know what tire size would be best hight and width for the GTO.
any ideas?:attention

You should be able to "safely" run 255/60/15's on the back - these are about 27" tall vs. the 25.6" tire height of your 14's.

You may be able to fit 275/60/15's - these are about 28" tall.

You will be able to fit 235/70/15's - these are about 28" tall.

You should be able to fit 255/70/15's - these are about 29" tall.

On the front - 235/60/15's are about 26" or a 225/70/15 would be about 27.5".

Lot's of options - just remember that changing the rear tire diameter will affect your overall gearing of your car. Those 255/70/15's will really raise your year end and really lower your RPM's at the same time.

Assuming a 3.23 rear gear and a 4spd tranny with your current tires you're turning around 2550 RPM at 60 MPH. Those 29" tall 255/70/15's will drop your RPM's down to 2250 at 60 MPH - effectively turning your 3.23 gears into about 2.85 rear gear.

just what I was also looking to do rpm wise,I have 3.90's in the rear and t-400trans.
the car is street strip,I have slicks for the track.
thank you....mike

I have 15X8 wheels on the back with 275/60/15 and 245/??/14 on the front. It gives it kind of a raked stance. You could just get tires put on those 15's for the back for now and put some on the front when you get two more 15's. I have a TH400 with a 3.90 as well. It doesn't do too bad on the highway. The 275/60/15 are 27.99" tall.

studda,
do you have any pics of the wheel tire combo on your car?
I would like to see from the sides and back.
mike
[email protected]

I personally don't like the look of a 28" tall tire in the back. Unless it is a slick of some sort. I run a 235/60/15 in the front and a 275/50/15 in the rear; 26" in all 4 corners.

I have 255/60-15's on 8" Cragar's out back and 245/60-14's on 7" in the front. You might get a little taller front and back but after it's all said and done you MIGHT gain an inch ground clearance. Maybe.

There are a couple pictures in my album on my profile page. I looked and the front tires are 215/70/14.

FWIW department - the original equipment tires on a '69 GTO were 27" so your 26" tires are 1" shorter than stock.

A 28" tire only goes .5" higher up into the wheelwell than the orignal tires - not enough to change the appearance much from the stock tires.

Good web site for tire sizes.

www.turbinecar.com/tires.htm

I also have 275/60 on a 15x8 wheel on the back of my 68. I think it looks great and is the perfect tire/wheel size for the rear of my car. I like the 28" tall tire for highway cruising, but I need to re-gear my speedometer since it is reading alot slower speed than the car is actually traveling. There's some pics on the 68-69 pic thread (scroll all the way down the thread for all the pics) if you want to check it out:

http://forums.maxperformanceinc.com/...=639898&page=9

15x8 Rally II's? Are they aftermarket reproduction wheels?
Factory Pontiac Rally II's didn't come in 15x8. 15x7's are as wide as they got. If you measured across from outside edge to outside edge and got about 8", then the wheels are 7" wheels. The width is measured inside the wheel lips, where the tire bead seats are. Personally I like 245-60-15's on 15x7's.

I have 255-60-15's all the way around on my 70 and with 15x7 Rally II's and no rubbing issues whatsoever, even with the HO Racing springs/lower than stock stance.

you can but 15x8 rims all over the place, Coker,Wheels Vintique etc.

I have run 275/60r15 on 15x7 rally II's out back on my '67. They fit well, look great, and tucked inside the rear wheelwells with no rubbing. The '68-69 rear wheel well has a little more room than the '67, so the 275/60 is a slam dunk.

You might be able to run a M/T drag radial 275/50r15 but I think you probably would want an actual 8" wide wheel and you might need to roll the rear fender lip.

I know...that's why I asked if you had "aftermarket wheels" or factory wheels, since you didn't say one way or the other. Since some people might not know that there aren't factory 8" rally II's, or know how to measure the width properly, and think they have 8" wide when they have 7", I had to check to make sure you weren't one of those people who don't know :) . Now we know for sure that you have 8" wide aftermarket Rally II's and can give advice based on that.

A 7" wide wheel is too narrow for a 275/60/15. I know people do it - but the MINIMUM recommended width is 7.5" and most people run at least an 8" wide rim.

I have 255/60/15's on a 7" wide rim and wish I had 8" rims as they "balloon" more than I like on a 7" rim. 255/60/15 is the largest/widest tire that is safe to run on a 7" wide rim.

I am not hearing any thing good about 14x7 wheels,why is that?
Does everyone just go to 15?

Because unless you are going to run bias ply redlines, you can't get an appropriately sized radial tire in a 14". The original tire height on most GTO's was about 27". Your reasonably wide 245/60/14's are too short (25.6" tall"). If you go to a 225/70/14 (26.5") you're getting closer to the appropriate tire height, but aren't wide enough for what most of us want on the rear end.

Bottom line - they don't make a big enough tire in the 14" tire size to satisfy what most of us want on our cars

wheels -tires
 

do you have any pics of your car?

I currently run a 15x8 rim.. but I have to respectfully disagree with your last sentence that it is not safe. There is no safety problem running a 275/60r15 on a 15x7 rally wheel. I've done it for years on several cars including my 67 GTO on pontiac rally II's and my old 72 chevelle SS on chevy rallys. I don't see what the issue is. It fits fine, looks cool, handles well, no uneven or premature tire wear...

I understand that BFG lists 7.5" as the min recommended width, but we're talking about the rim width difference of just half an inch... which I think is not enough to worry about.

It it were not safe, tire shops would refuse to mount a 275/60 on a 15x7... I have never experienced any such refusal.

As they say however... to each, his own! and.. Your mileage may vary... ;)

Another factor is the "cut" of a particular tire. Different brands/designs appear differently on a given rim despite being the same tire size. I remember my old Firestone SS Radials looking like balloon tires and another brand/same size looking completely different on the same rims.

car in my signature is wearing 275/60/15 0n 7" factory rims in rear.
215/70/15 up front.

my orange 71GTO has the same rears but 255/60/15 out front. i like that stance a lil better.

i used these tall fronts on this one because i had some LOW hangin hooker comps! i've got RA manifolds now.

And there are people that say that it's perfectly safe to run a 35 year old tire, too.

A guy used to be able to take an old used tire into a shop and get it mounted. Today many shops will refuse to mount used tires at all, or if they will, not if the tires are more than 5 or 6 years old - regardless of the amount of tread remaining.

The reason they have a MINIMUM recommended width is for SAFETY reasons. It's not because of looks...;)

Today, there are many tire shops that will refuse to mount a tire on a rim that is outside of the manufactures specs.

As a kid, I used to stand up in the front seat between my Mom and Dad. Today they'd get arrested for allowing me to do that...:eek:

Key word in their charts is "recommended". Too many of us have run the 275-60R15's on 7" wide rims tens of thousands of miles without incident. If you think about it, you are only bringing in the bead a quarter inch a side. Is it better to run a 7-1/2" rim, yes -- will it be catastrophic if you run a 7" rim, no.

I've wondered about the recommended wheel width lately myself, and here's the example I was thinking of. ln the late 70's, the factory put 225-70-15's on the Trans Am WS6 8" wide snowflakes. Now, if you look at the wheel widths recommended for 225-70-15, the chart will say that the maximum width should be 7.5", when we all know that size came on 8" wheels from the factory.

Thank you. There is no safety issue with 275/60r15 on a 15x7 rim.

Champ, a whole lot of members here are running this combo. I have never had an issue with a 275/60r15 on a 15x7 rim. I personally have run this size on a 7 inch wide rim for thousands of miles. I believe it is perfectly safe. I would never put a wheel and tire combo on my car if I felt it was not safe.

Half an inch difference from a tire manufacturer's 'recommended' rim width to the actual width of the rim does not make the combo unsafe. If you want to repeatedly claim that a 275/60r15 on a 15x7 rim is in fact not safe for highway use, please state a credible source... like an actual DOT study or something. Otherwise lets stop arguing on the internet because everyone knows what they say about that.. ;)


Grand73Am makes a good point... the FACTORY went over the recommended rim width by 1/2 an inch... was this safe? I'm sure it was quite safe for highway use or the factory would never have done it.

Because of this controversy, I read up on this subject and here is what I found: The narrower rim width causes the sidewall to flex more compared to the same tire mounted on a wider rim. The increased sidewall flex makes for a softer ride, and so a 275/60r15 tire on a 7 inch rim may not last quite as miles as if it were mounted on a 8 inch rim for the duration of the tire's life due to the additional sidewall flexing over the thousands of miles that the tire will be in use... Using a rim within the recommended rim width will ensure maximum mileage out of the tire before it is worn out.

Now obviously, you don't want to go way too narrow or way too wide on the rim, because then you can run the risk of the tire bead becoming unseated during hard cornering or something. I would say a 275/60 on a 6 or 5 inch wide rim probably would be unsafe for this reason.

I found this statement on the tirerack interesting:


http://www.tirerack.com/tires/tirete...jsp?techid=194


So there you go, proof you cannot argue with! Two manufacturers of high performance vehicles (corvette and M3) run rims half an inch narrower or wider than the tire manufacturer's published recommended rim width for that particular tire.

Chevrolet or BMW would never put these tires on a new corvette or M3 if they thought there was any chance of it being unsafe!!

I also had Firestone SS Radials just before the tires I have now. They looked so much wider than the tires I have now and had very square shoulders on them instead of a more round transition from sidewall to tread.

Just because you and some other folks have done it, doesn't mean it's safe.

Funny how you didn't post the whole paragraph as printed on the tirerack site:

Let's finish the paragraph:

So, I've just countered your proof positive, as you have not been in contact with both the vehicle and the tire manufacturer to assure that the internal stresses are within it's design parameters.

As I posted earlier, the narrower rim also makes the tires "balloon" too much. I don't really like the balloon look on my 255/60's with 7" rims. I can't imagine how bad it looks with an extra 20mm's of section width.

Keep yelling through you're bullhorn...;)

I don't need one.

When you left out the critical part of your posted paragraph, you lost all credibility.

I used to believe old tires were safe - until I had a "new" looking redline radial have the belts separate at 70 MPH. The tire had 80% of it's tread left, no sidewall checking and no checking on the tread area. But it was 12 years old.

That's when I started paying closer attention in regards to tires and safety.

Jeez.

that's a nice looking tire-wheel set up you have David Jones