Why am I told 285s are only for the rear and not all 4 corners?

Tire stores have been telling me that the 285/40R17s will not fit on the front tires. But I see people installing 315s!!! What needs to be done to fit 285s on all four wheels? Any modifications?

Most likely because your tire store doesn't know what they're talking about. Are the wheels on your car now, with different tires on them? If so, hop out to your car, swing the front wheels to lock on both directions, hop under there with your ruler, and see if you have clearance. Assuming the offset of the wheel is "normal" for your car, there should be plenty of space for a couple extra mm that those tires will take.

Dave

I have been curious about the same subject. I think if you put 9.5" wide rims all the way around, it would be fine. Thoughts anybody???

I bought the 10-Spoke SS rims from a guy and they do not have tires. I am looking for a set but for now they are just wheels / no tires so I can't check. I hope someone else has 285s up front before I order them...

You should have no problem, even with 9.5" wheels. I run 275's on 9.5" on the street and it's never been an issue. You're talking about .4" difference in width using the 285's. Like Dave said, as long as the offset is correct or least within a normal range, you should be fine. I was looking on Tirerack and noticed (first 285 I came to, your tire may vary...) required at least a 9.5" wheel. Once you go past at 275, it's almost time to consider something wider than a 9.5" wheel.

And yes, I run 315's on 17x11's all around when I autocross with minor rubbing on extremely hard cornering or bumps but it's very minor.

I added mine to the front on my clutch install which isnt finished yet so i dont know how they are gonna work. My car is lowered also. On a lift it is hitting the sway bar but only when its turned all the way to one side. Ill let ya kno in a couple of days.

Go to www.ground-control.com for wheel spacers... maybe 1/4 will help from hitting the sway bars.

Mine doesnt hit unless you have the wheel turned to the max. And majority of the time when you have the wheel like that your goin slow. Unless you wanna be on your lid i dont think your gonna turn your wheel like that at a fast speed.

Thanks!!! Are you using wheel spacers for the 285s up front? Or is there plenty of room on all 4 tires that doesn't require wheel spacers?... Sorry about the questions but I want to know before I spend $185 per tire...

Originally posted by Wild1
. . . is there plenty of room on all 4 tires that doesn't require wheel spacers?... Sorry about the questions but I want to know before I spend $185 per tire... Keep in mind that nominal tire sizes are just that. IOW, the actual section width and diameter will vary somewhat, and not everybody's 285 will be of the same measured width. I'd look up the actual dimensions of the tires that you intend to purchase and compare those measurements with the OE make/model 275 width tire. Don't forget to adjust the width(s) by 0.2" per half inch difference between the actual rim width and the rim that the tire size(s) was/were measured on. These dimensions can be found on the "specs" pages for many tires at www.tirerack.com .

Norm

Does anyone know the offset for his wheels?

The wheels are factory 10-Spoke SS Camaro wheels... 17 x 9.5

I believe the factory offset was around 50.

I just wouldn't think there would be any major problems with clearance then. A 285 is a little larger than I'D like to have on a 9" wheel though, it doesn't really stretch the sidewall out enough. 9.5" wheels are generally on the low end of a 275 tire. That would be my major concern.

I ran 285/40ZR17 Goodyear GSC's on the front of my ZR1 (17x9.5") rims for a while. I've since replaced them with 275/40ZR17 Goodyear F1 GS's.

I had no problems with clearance at all.

Coincidently, I also have 285/40ZR17 Goodyear GSC's on the rear ZR1 rims and find they are very solid and although they grip well, stretching out the tire that much does tend to "loosen" up the rear-end a fair bit (as does going from 315's to 285's since you have less rubber). Breaking the rear free is a bit easier, but lateral transistions do feel more "flat". Next set for the 17x11" rims will probably be 295's or 305's, I think those may give some good lateral support without giving up too much tire width.

Thanks for the input. The 285s on the rear are "stretching" out the tire causing it to be loose? I think that is where I made a left turn. You should have a larger tire patch with the 285s over the 275s which should hold better... right? I guess I'm fuzzy on the stretching concept. Please help. :)

What tires are you going to be using?

Most 275 tires are designed for 9"-11" rims so I'm sure 285's need at least a 9.5" rim minimum. By using a rim too narrow, you don't give the sidewall the support it needs to keep the tread flat on the ground. Not only that, but because it's not "stretched" the sidewall flexes on hard cornering giving you a spongy of soft feel. I took a quick look on TireRack's site and looks like (the first two I looked at) a 285 needs at least a 9.5" rim at the least. You can put them on 11" rims if that gives you an idea.

Thanks for explaining it. It makes more sense now.

Since I will be using stock 10-Spoke SS Wheels that are 17x9.5 it could be marginal to use 285s because of the potential flex in the sidewall. I've been checking out the Tirerack website. Good info. Thanks guys.

Thanks for the input. The 285s on the rear are "stretching" out the tire causing it to be loose? I think that is where I made a left turn. You should have a larger tire patch with the 285s over the 275s which should hold better... right? I guess I'm fuzzy on the stretching concept. Please help. When you stretch the beads out onto a wider rim, you also increase the vertical spring rate of the tire (since the sidewall ends up with less reverse curvature). In addition, the stiffness of the sidewalls and shoulder area is trying to lift the center of the tread off the road when you increase the distance between the beads beyond design width. You may need to add a little inflation pressure in order to get full use out of the center of the tread.

One effect of increasing the overall vertical spring rate is much like going with heavier springs or up a bit in antiroll bar size at that end. So, particularly if you've only stretched the beads out at one end of the car, you've altered the front:rear balance. Another is that while the stretched-out tire's response is more linear as you approach its limit, you also get less warning before it gets there and does let go.

Norm

I get it. 285s will stretch the beads on an 11" rim due to the tread width to rim ratio. There will be less stretch with the 285s on a 9.5" rim due to the tread moving closer to the top of the rim/bead.

That's it. For good handling, you want a stiffer sidewall so the tire doesn't move around in relation to the rim. It helps to make the handling more precise and gives you a better feel as to what the car and suspension are doing.

Thanks for your help. :)

Why does Chevrolet (excuse me... did Chevrolet) put 245s on the 17x9.5s? Instead of 275s?

Seems like it is a delicate balance between too much stretch (245s) and too little stretch (285s). Soooooooooo, 275s seem to be the best choice for a 17x9.5 rim.

Another variable would be the sidewall ratio right? A 45 or 50 sidewall rating on a 16" rim will behave differently than a 40 sidewall rating on a 17" rim.

Perhaps a 275 would be max on a 16x9.5 rim versus a 285 on a 17x9.5 rim. Wishful thinking, I'll order the 275s for the 17x9.5 wheels instead of the 285s for the 17x9.5s.

Did anyone heat-cycle the tires? Or is that BS from Tirerack? They seem to have a good organization and recommend the heat-cycling.

I asked a lot of questions in this response... sorry in advance.

All of the Chevy and Pontiac wheels are 9", not 9.5".

As far as heat cycling, that's only necessary for competition tires. Street tires are heated up to a more normal temperature and have a different tread compound. The softness of the competition tires benefits from heat cycling to help stabilize the compound BEFORE being used at the temperatures they will run at. I use heat cycled Hoosier A3S03 autocross tires to increase the life of the tire but it's just not necessary for your street tires.

THAT IS WHERE THE DISCONNECT IS AT! Ouch! Ok, that was my mistake...

I was informed that the 10-Spoke SS wheels were 17x9.5s which is why I went with them. Unfortunately, I sent them straight to the powder coating shop so I didn't measure them. So, they are 17x9s which means obviously that the 275s are the max recommended size for that wheel. Otherwise there will be too little stretch to fit the 285 on the 17x9 wheel. Ok ok ok...

I'm really appreciate everyone's help. :) This board is the best and I'm glad there aren't goofs on here like other web boards that can't give a straight answer. Before starting this thread, I was ready to purchase the 285s, and after everyone's responses, I'll stick with the 275s. I hope this thread helps others with the same question and use the search function.

Thanks everyone

:D