17" vs 18" wheels/tires

[86MCLS]

I currently have 235/60-15s at all 4 corners and they're about a 26" tall tire. Aesthetically they seem to fill the wheel wells OK. Since the car has been a stalled project, the tires are 20+ years old and what tread that's left on them will only be good for a couple of small burnouts not far from home and I certainly don't want to drive on tires that old, too unsafe.

I'm considering upgrading the wheels/tires to 17" or 18" rather than buy 4 new 15" tires and was going to go with the Car Craft fitment chart recommendations of 8" wide wheel, 255 rear, 245 front, 4.5" BS, etc. I can seem to get some 17" tires that are nearly spot on in the 26" range both front & rear, but I'm struggling with the 18" tires. Seems like those same width tires with 40 & 45 aspect ratios seem to be as much as 1" shorter in height. A 50 aspect ratio in a 18" tire is slim pickings & the price shoots up. I could go wider on the tires which will by default make them taller as long as I don't drop aspect ratio down, but then I get concerned about rubbing.

My car is not notched and has factory A-arms plus a fat front sway bar .I really like the looks of the 18" wheel but the 17" is looking to be the way to go, on paper, when it comes to fitment & tire height.

So my question is... Who here that are running 17" & 18" tires are happy with how they fill the wheel wells? What's the height/overall diameter of your tires? Pictures would also be helpful!

 

[WisconsinCutlass]

Here's a link to my thread when I bought new wheels and tires. All the sizes are in there. The pictures in that thread the car is lowered 1" in the front and 1-1/2" in the rear. The picture attached is with the stock springs in the rear. Hopefully this helps. If I were to do it again I would try to go 235-245 width in the front.

https://gbodyforum.com/threads/new-rims-and-tires.56260/

 

[86MCLS]

Here's a link to my thread when I bought new wheels and tires. All the sizes are in there. The pictures in that thread the car is lowered 1" in the front and 1-1/2" in the rear. The picture attached is with the stock springs in the rear. Hopefully this helps. If I were to do it again I would try to go 235-245 width in the front.

https://gbodyforum.com/threads/new-rims-and-tires.56260/
View attachment 83327

Yes that's great info! Thank you! Also helps with my decision as to go wider like a 275.

 

[melloelky]

switching to a bigger tire is always a good idea,you have better performance from your tires and much better selection for a better performing tire.I'm running a 18-9 275 40 with 4-7/16 bs in the rear @26" tall.it fits pretty well
in the front i'm running a 17-7 225 50 with 4-3/8 bs @25" tall.wish it was a 17-8 but that's life.the frame isn't notched and the front end is all after market.it's lowered one inch in the back and one and a half in the front.i have no fitment issues anywhere.I'm very happy with it.

 

[ck80]

If your goal is saving money but still getting into a 18" tire, have you looked into the local market for new car take-off rims/tires? It's far cheaper to buy a set of rims/tires from somewhere doing conversions on new cars than buying 4 new tires alone.

Then yoy spend about $80 on dismounting and mounting the tires on your rims, BUT, you can sell the left over rims after.

Saves several hundred dollars.

 

[UNGN]

255/40-18's are 26"

245/40-18's are 25.7"

Both are made by people that sell good tires for less than $150 each.

255 40s are supposed to go on 8.5" wheels or greater, but if you "got a guy" to install them, they'll be fine on an 8" rim. The National chains probably won't install it. If you have higher rear gears and/or a torquey motor, 255/45's are 27" tall and will work fine on an 8" wheel.

 

[86MCLS]

switching to a bigger tire is always a good idea,you have better performance from your tires and much better selection for a better performing tire.I'm running a 18-9 275 40 with 4-7/16 bs in the rear @26" tall.it fits pretty well
in the front i'm running a 17-7 225 50 with 4-3/8 bs @25" tall.wish it was a 17-8 but that's life.the frame isn't notched and the front end is all after market.it's lowered one inch in the back and one and a half in the front.i have no fitment issues anywhere.I'm very happy with it. View attachment 83331 View attachment 83332 View attachment 83333

That looks sweet!

 

[86MCLS]

If your goal is saving money but still getting into a 18" tire, have you looked into the local market for new car take-off rims/tires? It's far cheaper to buy a set of rims/tires from somewhere doing conversions on new cars than buying 4 new tires alone.

Then yoy spend about $80 on dismounting and mounting the tires on your rims, BUT, you can sell the left over rims after.

Saves several hundred dollars.

My goal isn't to save money, I'm just debating with myself on buying a set of new 15" using the same Cragar SST wheels I have now, or upgrading to 17" or 18" wheels, which would also allow room to do more than the 2WD Blazer brake upgrade up front. I want a combo that'll fill the wheel wells without looking lame, and will be as balanced in overall diameter front/rear as possible. While I don't want to spend a ton of money, main goal is optimum looks & performance. Don't want to lay down the cash for something that looks lame.

 

[86MCLS]

255/40-18's are 26"

245/40-18's are 25.7"

Both are made by people that sell good tires for less than $150 each.

255 40s are supposed to go on 8.5" wheels or greater, but if you "got a guy" to install them, they'll be fine on an 8" rim. The National chains probably won't install it. If you have higher rear gears and/or a torquey motor, 255/45's are 27" tall and will work fine on an 8" wheel.

I was seeing numbers vary based on tire brand, with 255/40-18s from just a hair over 25" to just a hair under 26". With the 255/45-18s being 27" +/- I was concerned they'd be too tall, hence why I threw the question out there.

The engine is a pretty stout 400 SBC and I have a ~2600 stall Hughes converter with a TH350 trans & 3.73 gears so I'm not concerned about the extra 1" diameter messing with performance.

 

[86MCLS]

Also should disclose I have the Eibach Pro Kit springs that lower the car 1" to 1.5".