upgrading to bigger rims and tires

[guisseppe69]

Hi everyone,

Just got my self a 1986 Buick Regal Limited with the 5.0L 307 V8. I am crazy enough to make this into my daily driver after selling my BMW 323i which I drove because it was newer and reliable blah blah blah!!!! (boring as hell) So I sold the beemer and decided to turn one of my favorite cars into my everyday car. My 1'st project was making sure everything was in great shape for it to be reliable. I have done that and now that it is safe and hopefully in great condition I am now making it look more up to date less Granny's car more pro touring without the performance (for now). I have purchased a set of wheels STR 514 18x8.5 with +30 offset and a 32mm thick adapters (5x4.75 to 5x4.5) which should give it a -2 offset for all 4 wheels. I want to put the widest tires possible and don't mind staggering the tires rear to fronts. I have a 2 inch spindle drop in the front suspension. I have seen posts that states a set up of 245/40/18 fronts and 275/40/18 rears. Now I know 275 is wide for an 8.5 inch rim but I am not racing it nor will I be going to fast with a wife and 2 young boys at the back seat. Has anyone done this and if so share some advice. Any help would be appreciated.

 

[jetsetw31]

Hey, 275 is big for a 8.5 inch rim. the minimum rim is 8.5 with 9.5 being optimal. Just because it fits doesn't mean it will be right for the car. Why? because too wide a tire on a rim will prematurely and unevenly wear out the tread and put stress on the side wall as if you were driving top speed all the time. I give it about 6 to 8 months before you buy another pair. Maybe you have that kind of money to throw away, but the other consideration is safety. The littlest road hazard becomes major when your tires are stressed to the max all the time. A simple low speed turn in the rain can be a spin out situation in an instant. I've seen it happen on a Porsche.
He blew it out from a spin on the interstate and was looking for a free replacement because he only had it six months. We told him wrong tire for the rim. He had 245 40 18s on a 9.5 inch wide factory rim. (It's the same thing with undersized tires too, high stress load) The right tire was 265 40 18. We wouldn't sell him anything else for liability reasons. ( I worked at Sears then.)

It's really not a good idea to stagger tire sizes. On a Gbody, it's better to stagger rim sizes with the right tire.


In your case, get four 245 40 18s and stagger your off sets. I did that on my '81 Cutlass and it came out nice. I had four 16 x 8 (FWD)'89 Grand Prix wheels and tires. I used 1 inch spacer adapters in the front and 1.5 inch in the rear.
I hope this helps you out.
T

 

[guisseppe69]

Hey thank you for your reply. Your car is my inspiration. lol... So I didn't really want to go 245/4018 on the rear as I want to go a bit wider. You mention you can get a way with 265 40 18's. I dry fitted the wheels today and based on our trial and error with stock suspension on the rear and a 2 inch spindle drop in the fronts I should be able to go with 2 inch spacer in the fronts using 245/40/18's and 1.5 inch spacer in the rear using 265/35/18's with the wheels being 5x8.5 with 30mm offset. What do you think? The reason for the 2 inch front spacer is because of clearing the center hub.

 

[jetsetw31]

Unfortunately your the first to try this combination so everything is trial and error. With the combo I had on my '81 Cutlass, My rims had a 25mm offset with the 16x 8 Diamond spoke rims. With a 30mm offset are yours off a FWD car?

Are you running the stock brakes? I had the stock set up on that car. I never got a chance to lower it, yet it still looked right. It got totaled by my ex wife in NY. It was factory brown with tan interior and those gold centered rims. The rims accented the car perfectly. It was her DD. I got her a SUV after that.
The spacers I used gave me a 4 inch back spacing on the fronts and 3.5 inch on the rears. With 8 inch wide rims, I had no clearance issues and the rears looked wider than they were because they stuck out more.
Come to think of it, they looked just like the rims and tires on my current car fitment wise of course. I only have 15 x7 and 15 x 8 on my '88 Cutlass. 225 60 15 and 245 60 15. It sits a tad higher in the rear than My '81.
The rears can go in as deep as 4.5 inch, but the tires will be real close to rubbing the frame. The fronts can go that deep also and they will rub in tight turns. You want to watch out for that. 25mm is approximately 1inch and 30mm is 1.16 inch. So my 1 inch spacer made my front 8 inch rim 0 offset.
I hope this helps you out also.
T

 

[guisseppe69]

I think I'm gonna go for the whole enchilada and go ahead with the 18x8.5 wheels all 4 @ +30mm offset and 6" BS and 265/35/18 on the rears using 1.5" adapters which will bring my BS to 4.5" and offset to -8mm. Now the fronts will be 245/40/18 using same rims but 2" adapters (due to center bore clearance issues). This will give me a 4" BS and -20.8mm offset. Lets just hope everything goes well. What is your set up?

 

[guisseppe69]

Everything stock except for the front spindles that has a 2" drop.

 

[guisseppe69]

I wish I knew how to post photos. My wheels are STR 517 with a 3 inch polish lip and gold center. The Regal will be pearl white with balck trims like grill, headlicht bezels etc.

 

[guisseppe69]

Here is Betty White Before I turn her into a beast.

 

[guisseppe69]

My wheels!

 

[guisseppe69]

Hoping to come close to this look.