Topic: How wide can you go on stock rims?

[TecSolOnt]

 Thinking about putting new tires on my stock chrome rims ,  like the look of a wider tire at the rear which you see on some of the  Porsche models. I like the the rims so just wondering what my options are sticking with them.

  Wondering anyone know how wide we can go with these rims, anyone have experience with putting a wider tire on the rear?  


 

[Kelu]

Also I think depends if you have lowered your car.

[Ben L]

I think the Porsches achieve that look through a staggered setup, with a wider rim in the rear.  I run 275s on a 9 inch rim in the rear, and 245s on the stock 8 inch width in the front.

Here's how it looks --




Trying to get overly wide tires on a narrow rim is not a good idea.  Each tire is designed with a certain sidewall flex point.  If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, which reduces tire life and could result in failure.  Also, a narrower tire will increase the aspect ratio, because it will pull the beads on either side closer together, and result in a sidedwall bulge or overhang over the rim bead.  This will offer a cushier ride and more shock absorbtion, but the price will be slower response to turning inputs, less precise handling and increased slip angle and rollover in hard turns. Also, the "footprint" of the tire depends inevitably to some degree on the rim width.  If you squish a wide tire on a skinny rim, you are not going to get the full tread width contacting the road as you would with a proper sized rim.

All "ultra performance summer" tires specs. on the Tire Rack suggest that 245 or maybe 255 is about the limit on an 8" rim.

[Brazen17]

Ben L - Would a 255 on a 19 x 8.5 be ok or even a 265?

[Ben L]

An 8.5 inch rim will likely accomodate most 255s.  For example, the rim width range for Bridgestone Potenza Re-11 255-35-R19s, and for Yoko Advan AD08 255-35-R19s is 8.5 to 10"  You may be able to squeeze another 10 mm on there, but may have some degree of the downsides noted above.  Also, I am not finding decent 19" tires in 265 size.  The increments in that size seem to be 255 to 275.

Keep in mind the stock rim is only 8."

[Critterman]

I have 255's on 8.5 rim, tire rack would not mount 265's on the 8.5 rim which is what I wanted.

[TecSolOnt]

  Thanks guys, saves me some time. Since I don't want to trade out the rims it looks like 255's are it.  Thinking ahead to next summer...

[Brazen17]

Just ordered some Hankook Ventus V12 evo K110 255/40ZR19's for my new 19" MODA MD1's.  Can hardly wait til they arrive early next week!

[TecSolOnt]

 Nice ! Put a pic up when you get them on Roadstersol !

[Brazen17]

I'll try.  I'm not very computer savy but I'll figure it out. 

[ThunderSky]

I will be needing new tires in the spring as I have a bad tire with a small bubble, maybe from a pothole. Dealer says the rim is fine but tires are over half worn and typically crap in the rain anyway, so I think I'll order 4 new ones to put on when she comes out of winter storage. Looking at the Falken FK-452's and can get either 245-45-18 or 255-45-18. I'd like to make that small leap to the 255's. (on stock suspension)

Anybody see an issue with that ?? 

[snaponbob]

ACTUAL size is sometimes different than what is embossed on the tire. Try to find the true dimensions of any tire you plan on. All things being equal, a 255 should only be less than 1/2" wider than a 245, so should fit okay. Tire Rack shows all dimensions for all their tires right on their site. Discount Tire should be able to supply that info as well, as do most tire company web sites. One very important number is the overall diameter so as to not screw up your speedo.

[kennysabarese]

Do you guys think that a staggered setup encourages understeer? And can the swaybars account for that?

[spicy3480]

FYI...I am running 255's on an 8 inch rim with no issues.  On the rears, I am running 275's on a 9 inch rim with no issues either.

[ThunderSky]

ACTUAL size is sometimes different than what is embossed on the tire. Try to find the true dimensions of any tire you plan on. All things being equal, a 255 should only be less than 1/2" wider than a 245, so should fit okay. Tire Rack shows all dimensions for all their tires right on their site. Discount Tire should be able to supply that info as well, as do most tire company web sites. One very important number is the overall diameter so as to not screw up your speedo.

Yes, I looked at that and the difference in diameter is very minimal. 26.7" dia for stock size and 27.0" dia on the 255's . so only about 1% larger.

 

[snaponbob]

Do you guys think that a staggered setup encourages understeer? And can the swaybars account for that?

Yes, and maybe. In daily driving it won't matter much at all. The more you "lean" on the car, the more apparent it will get. Just ask the guys with BMW 135i's and many of the new M series Beemers. They all have bigger rear meats, and when driven hard they PUSH !!!!!!!!!

[Graywolf]

I had a similiar problem with Tire Rack. I have 18x8 oz racing wheels and run 295/30zr18 hoosier a6 same as Gm racing.  Tire rack stated not compatible !  The tire width is 1 1/2 wider than stock  Handles great, stable great traction ,ran speeds up to 120 on road racing course,beats most vettes,not the Zo6  Great set up for autocross/Hi speed autox/time attack events. Gray Wolf

[Uranium-238]

Do you guys think that a staggered setup encourages understeer? And can the swaybars account for that?

I'd ask Ben that, I know he's got a staggered setup and knows how to push his car to the limit.

[snaponbob]

I had a similiar problem with Tire Rack. I have 18x8 oz racing wheels and run 295/30zr18 hoosier a6 same as Gm racing.  Tire rack stated not compatible !  The tire width is 1 1/2 wider than stock  Handles great, stable great traction ,ran speeds up to 120 on road racing course,beats most vettes,not the Zo6  Great set up for autocross/Hi speed autox/time attack events. Gray Wolf

They were covering their "liability" a$$. Even Hoosier says this will work. EVERY A/Stock Kappa has run 295 A6s.

[Ben L]

Do you guys think that a staggered setup encourages understeer? And can the swaybars account for that?

I do not think so.  When you have weight over them, the 245s grip OK.  I think springs and anti-sway bars are the formula for reducing understeer to tolerable levels.  The car is pretty neutral now, and tends toward oversteer when pushed really hard.  Which is how I want it.  BTW I think you can get a 255 on the stock front rim no problem. 

[kennysabarese]

The thing I am trying to determine is if going wide as possible with the tires is the best for street and road courses. I know for AutoX more is better, but that's a lot different.

That's why in the other thread I'm trying to find out what Don runs on his T2 car, the specs aren't actually written down in the Solstice Performance book

[Ben L]

The thing I am trying to determine is if going wide as possible with the tires is the best for street and road courses. I know for AutoX more is better, but that's a lot different.

That's why in the other thread I'm trying to find out what Don runs on his T2 car, the specs aren't actually written down in the Solstice Performance book

For performance applications, track work and autox, the bigger the contact patch the better, I'd say.  At some point, weight and increased rolling resistance of a wider front may be a factor, but not on our relatively high HP cars.  I know Eric K (local SCCA A Stock GXP hotshoe) runs 295 A6s at all corners, but switches to them at the event.

On the street, a wider front can cause problems, including tramming (i.e., "wandering" and tending to follow truck ruts, etc.) and increased tendency to hydroplane.  This is a huge problem on the Cobras.  I have driven on my 315 V710s in the FFR coupe to nearby events, a couple of times in the rain, and used to do it regularly on 275 Nitto NT-01s in the roadster, and it is always pretty terrifying. 

Larry Casey put a hitch on the coupe, and I just finished my tire trailer (yay!), so I will not be doing that again.

Because my GXP is primarily a street car, those were the reasons why I maintained the stock width in front.  If you are going to ask your rims/tires to do dual duty, the bottom line is that the vast majority of hours are going to be logged on the street.  Again, I think you can upsize the fronts a bit, but would be cautious about drastically increasing the rim width on a street car.  If you do, be aware of the downsides of a wide front tire in wet highway driving especially.

[kennysabarese]

Yeah I am worried about having too wide on the street.

I just know once I put on a big turbo kit, I'll be sliding all over the place. So I wanna find a happy medium for street and track.

[Critterman]

You can put 255 on the 8" rims, but none of the sellers will sell you an 8" wheel with a 255 on it. I have 8.5" rims, and they would not go past 255 when I bought the wheels and rims.  They would sell me larger tires, but not mount them.  As SOB said "liability"