Watch out for the WIDTH of the tire and wheel up front. You may run into rubbing issues. No problem on the rears.

 

I have road raced, raced at the strip and driven 20's on street rods. 20" wheels will degrade performance, period. 20" wheels will degrade ride quality. Period. No ifs, ands or buts. Shelby and others make 20" wheels because of the "want" by purchasers, and most people are stupid. Show me a Shelby that is a real race car with 20"s and low performance tires. Show me any sanctioned race car that has 20" wheels. The same make of tire on a 18" wheels will out perform the same tire on a 20" wheel, and on a 16" wheel it will out perform the 18's.

20"s look cool, but are not performance wheels by any stretch of the imagination. To each his or her own. If you like 20's get em. If you are looking for performance over style, don't. It's as simple as that.

 

Tire diameter and gear ratio are 2 of the parameters that define a given speed for a given engine RPM and how quickly you get there. To many, you can tinker with either and be oblivious to the outcome (until you see some newb post "Why is my speedometer off?"). To others, it's a performance issue. If you wander from the stock 27.6" (if I recall off hand) and don't have a tuner, your speedo will be off at the very least.

 

I have a car that really needs the "look" of a bigger wheel. I can tell you from experience two things: You get a rougher ride with 20" wheels......but you also get a stronger grip on the road. Having recently changed from 20's to 19's I see a HUGE difference in handling. Smoother, but less grippy...if that makes any sense. I attribute some of the difference to different manufacturers of the tires, but not all of it. The 20" Nitto Invo's I previously had would hug the road, no matter how fast you seemed to go. I especially miss them on curvy roads.

And Nuke....if you refer to 20's as "in da hood" one more time, I am going to personally attack you with my Gee-toh wagon.. grrrr!!!!!!

 

I think 20's look fine on the S197. it's a HUGE wheel well to fill up, my stock 17's look like 15's would look on another car, at least to me. I'd go with 20's on my car except there's not a lot of tire choices for the sizes I want to run. I'm going with 18's simply because I want to run MT drag radials in the rear and they only go to 18".

as far as a blanket rule that 20's are "bad" for handling I don't agree. there's plenty of exotics that come with 19's and 20's from the factory. when it's bad is when you get the wrong size and the overall diameter go way up. it would be like going from a 4.11 gearing back to a 3.55, you're gonna notice that. also if you go cheap and get some 500 treadwear tires that'll hurt performance. also most 20's are pretty heavy, unless you're going to spend the money for some forged wheels you'll be adding some fat to an already fat car.

to me on the 04 and older it's domestic rice if you go with 20's, the wheel wells are pretty small on those body styles. 05 and up are larger cars and have larger wheel wells, 20's work and look great with the right tires. if you go from my stock tires to 20's you go from a 5.09" sidewall height to a 3.5" sidewall if you keep the same overall 27" diameter. 3.5" is still a decent amount of tire between the road and the rim.

but everyone is different, do what you like to your car

 

some very good points liberty, but really, how many among us are using our s197's as "race" cars? yeah, we enjoy the performance on the street, and as a street car, we're not going to see huge performance swings between 18's and 20's. it's just not realistic. more or less comfortable ride? sure, but how many people actually know or care if their shiny new 20's have increased their 1/4 mile time by a half second? then there's all of the people with modded street cars... i can tell for you for certain, between my suspension setup and f/i, i was cornering on rails and smoking the tires off the rims before and after i mounted 20's.

and as far as the completely subjective point of whether they look good or not, who really cares what anyone's opinion is other than their own. i know i don't.

lastly, 20" wheel debate threads =

 

20" rims look good, but damn, I can feel the extra rotational weight on 18"s already. Unless you have engine performance mods, you can really feel the slow down.

If you liked the light feeling, you can kiss that goodbye when you put on 18"+
I can tell you for a fact I won't be dragging in my 18"s

 

Ya' PROMISE??? Invite me over for fried chicken and watermelon and I'll consider it, Shella...

The look is simply a matter of preference. If that's what trips your trigger, floats your boat, etc, then go for it. The OP asked; I commented. Were good.

 

Mmmmmm, Fried chicken. I want that for dinner

 

As long as you don't expect me to cook. :X

I can honestly say I didn't "feel" any super change in the get up and go in my car. Perhaps I need to be on a more intimate level with my car.