ehh, i guess i have to go 17'' rims then cuz i dont think they make 16 inch 275's lol

 

I always thought bigger tires up front helped handling? More rubber on the road. It seems logical.

-Rippin

 

Actualy the (R17) stands for R(adial) 17(inch rim size).. so if your tires read this, than you
don't have stock IROC 16's.

Not really.. you have WAAY more tire to turn (I mean.. when turning the steering wheel).
Think of it like this..
Speed bikes: Skinnier the tire.. better the handling/better the speed capabilities.
If you put wider tires up front than were designed.. then it will also throw out your handling..
as your suspension is made for 215's, 245's, whatever size..

 

Err, I hope you haven't bought the tires yet. Otherwise, you'll need to EBAY those 16-inch wheels and buy some 17-inch wheels. That's a 17-inch wheel sized tire. You'll be able to slip your new tires onto the 16-inch wheel BY HAND, but getting it to pressurize will be a real PITA.

I'm running that exact same sized tire on my Trans Am, and the footprint is only marginally wider than the 245's on a 16-inch wheel. However, the side profile is great. The only problem with the 17 inch wheel is that your suspension has to really be up to snuff. There's no forgiveness for sloppy suspension components, or your car will track all over the road.

--drb

 

I knew I was right:

http://www.thirdgen.org/techbb2/show...hreadid=209314

More contact patch means better handling. Happy Reading.

-Rippin

 

More contact patch=more grip, not ALWAYS better handling. if you put a 33X15X15 Super Swamper truck mud tire on your car you have a bigger contact patch and a terrible handling car. Tire design, compound, sidewall stiffness all contribute to "handling" Skidpad numbers usually reflect more of the "grip" and Slalom numbers usually show more of how we a car "handles". Good link though.

 

Sounds like we all need some education on tire specification. We're all running on generalizations. Here's a few of my own:

1) Friction. The wider the contact patch, the greater the peak friction. In addition, the greater the contact patch, the greater the rolling resistance. Skinnier tires will reduce rolling resistance. The sacrifice is that peak friction is reduced. Since drag cars want to accelerate in a straight line, it's okay for them to lose some peak friction for cornering, since they don't turn, except onto the return road.

3) Mass. Generally, the wider the tire, the heavier it will be. This goes for increasing of the wheel diameter, too. Since the tire has a lower sidewall, it must be manufactured to be stiffer, with heavier construction materials. In addition, when moving from a 15 to a 17 inch wheel, there will be more mass located farther away from the center of the wheel. This increases rotational inertia. The wheel, in essence, becomes harder to accelerate, and harder to slow down. A double-whammy, for sure. That's why there's 20 pounds PER CORNER extra mass on my Trans Am with my ROH wheels: The whole package weighs 52 pounds per corner versus my road-racing 16 x 8's which weigh 31 pounds each. That's also why drag racers LOVE skinnies: The reduction in mass and centrifugal inertia helps their cars accelerate faster.

4) Why do 17-inch wheels HANDLE better than 16-inch wheels? It has to do with contact patch integrity. They 17-inch wheel can keep more of the tread in contact with the road. The 16-inch (or 15, for that matter) with its taller side wall, will allow the tread to roll up and away from the pavement. When this happens, there is a reduction in contact patch with the pavement, and the tire can more easily slip from a static to dynamic coefficient of friction. Rubber, like most materials has a lower DYNAMIC coefficient of friction than static. This is why a locked-up tire will skid farther than one that continues to rotate while braking.

5) Sidewall bulge. When choosing a tire, make sure it isn;t too large for the wheel. 275-40-17 requires you to install it on an 8.5 inch wheel, as a minimum. 9.5 inches is optimum. If you put it on a skinny wheel, your contact patch will look wide, but the sidewall will not be able to control it like it should. Under hard cornering, the tread will squirm left & right, as the sidewall 'stands up' on one side, and 'lays down'on the ither side. The result is that the contact patch lifts up and away from the road surface. Thus, the advantages of the big fat tire (and it's ability to maintain contact patch with the road) become negated in anything but straight-line acceleration.

Hope this new list of generalizations helps,

--Dan Burk
'84 Trans Am. 1.05 g sustained lateral acceleration verified, 1.27 peak lateral acceleration also verified at Gingerman Raceway, August, 1999.