Tire Upgrade on Stock 14" Wheels

[Kristopher Gerbracht]

What Zaloryan said is true. 215/60/R14 is the widest you can go without rubbing the fender. It will make your car handle much, much better too.

[Electra_T_Type]

? I had 225 and no rubbing.

[BxOutkast2009]

What Zaloryan said is true. 215/60/R14 is the widest you can go without rubbing the fender. It will make your car handle much, much better too.

I am looking to invest in new tires for the Century, but Im willing to stick with the stock steel hubs...My only question is can I mount 205/60/15" tires on them? The 14" are okay, but as noted in the thread, they're getting harder to find, and 15" 205's are more common...

[DarkFox]

Wouldn't work.

The last number ( the 15" ) refers to the diameter of the wheel they will fit.

You can get away with changing the first two numbers slightly, but not the last one.

Going by stock steelies being 185/75/14, and what others have listed here, you can run a range of sizes


Width can range from 165 - 225

The lower the number, the skinnier the tire. (Better for snow / mud tires to be skinny)
The larger the number, the wider the tire. (Better for over-all handling on dry roads)


Aspect ratio / Height can range from 60-95 without issue

The lower the number, the thinner / lower profile the tire
The larger, the thicker / taller the tire


The last number is tied to the size wheel you're going to put them on; they must match.

You can't put a 14" tire on a 15" wheel, or the other way around.

[lemons bob]

there is one thing to note on the aspect ratio. Its a ratio for the sidewall height so the height changes with the width. The number is actually the percentage of the width, to determine the sidewall height you multiply the percentage by the width number. So for the stock a-body tire 185/75 r14 the sidewall height is 185 x.75 = 138.75mm

You have to note this because if you go with a wider tire you have to be sure to lower the aspect ratio or you're tires won't fit. For instance a 215/75 r14 would 161.25mm while 215/65 r14 would be 139.75mm or just 1mm different.

[DarkFox]

Alright, dilemma time.

I want the BFG A/T KO's, but they're just too expensive.

I know General tire has tire equivalent to them for a lower price, I'm just unsure if they will fit and need some advice.

I'll post out my whole thought process, so everyone can see what I'm doing.

Here's the links I've used to.

Tire Calculator

Wheel Terminology


The stock Buick / A-body tire size is 185/75/R14

The BFG A/T tires I know will fit. They are 195/75/R14

Here's the diagram showing the difference between the two.

The BFG tires are;

1.9" larger in circumference

.3" taller sidewall

General tire sells their only R14 tire as 27X8.50R14LT

Using the Wheel Terminology link above, they list the Metric equivalent size as 225/75R14.

Here I compare the stock A-body tire size with the General Grabber At2

The Grabber tires are;

7.4" larger in circumference

1.1" taller sidewall

My question is, would this work without rubbing?

Something in me doubts it, but it's worth asking nonetheless.

[DarkFox]

So I finally got down to the nitty gritty of tires and sizes, and learned a lot about our cars.

I pulled the front wheel on my Century to measure the distance from hub center to the base of the strut.

Worst case scenario (back part of the strut), is 12" from the center.

Best case (operating area), is a smidge taller than 13" from the center.

That means a factory strutted a-body can cautiously run up to a 26" overall diameter tire.

Interesting to note though, I measured my stock 185/75/14 tires outer diameter (OD from here on out), and the numbers don't add up.

Typically one would take the tire size (185/75), and deduce the OD with some quick math to come up with the sidewall height in mm.

185*.75 yields a sidewall height of 138.75mm.

My stock wheel is 14" (inches), which converts to 355.6mm

Our equation for OD would look like this (138.75*2) + 355.6 = 633.1mm , or 24.9 inches OD, is what it SHOULD be.

However, when I simply measured the tire across, I end up at exactly 24".

Whether that means my method is flawed, and we can infact run a 27" OD (or 225/75) tire, I'm not exactly sure.

However if anybody has the access to that size tire and the opportunity, if they could mount a 27" or 225/75 tire and check for rubbing, it would finally put me at ease knowing the maximum tire size our vehicles can accept.

[Century7667]

I wonder how hard it would be to put the Pontiac AWD gear into your rig?

Ken T.

[DarkFox]

Would be interesting, to say the least.

The car does have the 'hump' down the middle for a rear driveshaft, though it is occupied by the exhaust.

I'll try and see If I spot one in a yard what would be involved in swapping it over, though I don't think I want to get that involved, both financially and mechanically, with my Century.

If it's mostly a bolt-out / bolt-on job, I'll give it some fair consideration, but any custom fabrication beyond an exhaust, or electrical involving ECM compatibility and I'll probably let it pass.

[lemons bob]

the gas tank will be the problem. the 6000 awd have a special gas tank which are pretty rare now a days and there are no aftermarket ones. I was thinking a rwd a-body could be a pretty fun thing. The engine bay seems like it should be able to hold a v8, and with its size and weight it should be pretty darn quick.

[b_nad]

Does anyone know if 205/75/r14 will fit our a-bodies without rubbing? Thanks

[Aiken Chafin]

I recently put 15" Stock rallys on my chevy celebrity, originally 14" rims. Will that change the speedo read and mileage reading by much? Or is it not a concern? And if so, how do you make it correct?

[turbokinetic]

I recently put 15" Stock rallys on my chevy celebrity, originally 14" rims. Will that change the speedo read and mileage reading by much? Or is it not a concern? And if so, how do you make it correct?

You can look up a chart showing the correct size tires for the 15" wheels, to keep the speed ratio correct.

The overall height of the tire is what effects the speed and distance readings.

My 86 Buick GS came with 15" wheels factory. It's not parked here now, maybe later I can tell you the tire size.

There is a gear set in the transmission which sets the tire size ratio. I don't know how many different options there are. The C/H cars (LeSabre and Park Ave) had taller tires. I don't know if any of them had cable driven speedometers, though.

If you don't mind spending money, there are companies that will make a gear adapter for this purpose. It connects to the transmission in place of the speedometer cable, and then the cable connects to this device.

[Ray_McAvoy]

Does anyone know if 205/75/r14 will fit our a-bodies without rubbing? Thanks

That's the size I'm running on my '88 Cutlass Ciera. The front tires do rub a tiny bit when making a sharp turn. But they're just rubbing lightly against the plastic inner fender liners so it doesn't hurt anything.

[b_nad]

That's the size I'm running on my '88 Cutlass Ciera. The front tires do rub a tiny bit when making a sharp turn. But they're just rubbing lightly against the plastic inner fender liners so it doesn't hurt anything.

Awesome thanks!