Contour Enthusiasts Group Archives Forums Modifications Wheels & Tires am i crazy

ok i just recently got 19's on my csvt and since ive had them it seems that my car rides ALOT harder, i was thinkin that it was because in riding on 35 series tires. its liek i feel every bump also cornering just isnt teh same. my car just seems more top heavy and liek it doesnt want to corner as well. is that just in my head or can all these things really happen.

I'm not sure what wheel diameter you were running before, but moving to 19" from 16" or 17" will give you a much shorter sidewall, resulting in a stiffer, less compliant ride. Therefore, "feeling every bump" shouldn't come as much of a surprise. Most 19" wheels will also be substantially heavier than the stock 16"'s (unless you get into some high-buck forged wheels), resulting in greater unsprung weight and generally poorer performance. Simply put, no one puts 19" wheels on their SVT's for performance; it's generally all about the looks (they certainly do look good).

BTW, do you go to ECU?

Not just your head. The feel is subjective, but every suspension deisign has a limit on how short a sidewall can be before it begins to compromise handling. The advantage of the short sidewall (low aspect ratio) is that the tread is more stable. As your car rolls, the suspension has some variation in the camber built in to compensate for the body roll. A double a-arm suspension has a lot of geometry possibilities. A strut is more limited. As a result, the camber of the wheel/tire assembly tends to track the body roll more than a well designed double a-arm suspension. When the wheel/tire assembly rolls with the body, the sidewalls flex to allow the tread to stay on the pavement. If the sidewall is too short, then the tread follows the camber angle of the wheel too closely, and the effective contact patch becomes much narrower, only using the outer portion of the tire.

One of the misconceptions many people have when putting wider tires on thier car is that the they are putting more rubber on the ground. In fact, they are only cahnging the contact shape. The actual size of the contact patch is determined by the weight on the wheel/tire assembly and air pressure in the tire. The wider tire has to deflect less to go froma round shape to the flat of the pavement. Hence, it is more stable. The shorter sidewall of a +1, +2, etc system does the same thing, it stabilizes the tread on the pavement. To get an idea why stability is important, place your hand on a flat surface and try to slide across the surface. Now do the same thing, flexing your hand slightly. The total contact patch has changed little, but your hand now moves much more easily across the surface.

In answer to your original question, in effect, by putting such a short sidewall on your car, you have had the effect of putting a narrower tire on the car when the car rolls in the corner. Now instead of benefitting from the short stiff sidewall, the tread is flexing as has to go from round to flat over a longer distance. That short stiff sidewall is also transmitting bumps to the wheel much more efficiently.

I have no way of being sure (maybe Luke at tire rack, or other who have had a chance to controlled suspension tests, could shed some light) but I think that given the overall diameter of the wheel/tire assembly, and the strut supension of the contours, I would guess that optimum handling would be with wheels about 17 inches without significant changes in the camber of the suspension.

My $.02

Sorry for the length of the post.

Originally posted by SVTpyr8:

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ok i just recently got 19's on my csvt and since ive had them it seems that my car rides ALOT harder,

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of course 19inchers are going to run hard, and in our car, you won't be able to get the tire fat enough to even out the aspect ratio and reap true benefits, so your car looks cool, but won't corner as well, and will ride like crap. . .R&T did a thing two years ago or a year ago, when plus sizing started to get more economical and popular, and found that going from a 15 or 16in stock, +1 (to a 17in) had the best performance and the least compromise, while +2 and beyond decreased in performance (because of what was previously said in that huge last post). . .ebay the 19inchers and enjoy life and handling again. . .

You sacrifice a lot going to 19s (too big IMHO).

Best size IMO are 17s.

In reply to:

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You sacrifice a lot going to 19s (too big IMHO).

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I agree. They look cool, but they are not my style.

To me personally, I always thought that going more than plus 1 was just plain stupid.

bigger the car the bigger the rims is the way i see it and Contours aren't that big

I'd go 17s max...just cuz I think a nice body kit low to the ground looks good and can't really do that with 19s

but if u ever give away your 19s I'll take em

Actually Normy,

Considering that the vanilla 'Tours come with 14" steelies, the early SE's with the 15" wheels are already a plus one, and the SVT's 16's are a plus 2 from the factory.