The Definitive tire size chart
08-25-2022, 11:45 PM
#11
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Join Date: 05-01-2014
Location: California
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Hello... I just installed Michelin Primacy 245-45-18's on my Wife's 2008 HHR SS with factory SS wheels. Its a close fit, we have had zero issues. It has changed the dynamics of the vehicle with a more comfortable ride, quieter, friendlier handling and looks a lot better with a more proportionate sized tire. Hope this helps...Maurice.
08-26-2022, 04:59 AM
#12
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Join Date: 12-05-2014
Location: Northern Ohio
Posts: 2,595
How would coilovers change the position of the lower spring seat? There is a fixed distance from the center of the axle to the spring seat, coilovers would change the distance from the lower seat to the upper seat. The only way to force a bigger tire in is to increase the wheel offset, or use wheel spacers. Both of those options will change the steering geometry, causing tire wear and different (probably dangerous) handling characteristics.
Google around and see what “coilovers” are offered for HHR/Cobalt. The OEM struts are already “coilovers,“ i.e., the spring and the dampener are coaxial. And at least some of the available sets don’t provide coilovers in the rear at all. They provide a different shock and a different spring. So in the vernacular, there are “lowering springs” which just springs, and “coilovers” which are sets springs and dampeners, virtually all of which provide adjustable spring height, a.k.a. “ride height” in the front, and may provide the same in the rear. Some also provide dampening adjustments.
The coilovers available, if they change the position of the struts spring seat, do so by… changing the position of the spring seat. But virtually all of them, equally importantly, make the diameter of the spring smaller. Presumably, these things are done specifically to provide more room for the tire.
And yeah there are negative effects too making changes to accommodate larger tires, some of them quite significant. But keep in mind that while some of these changes are made for the track, some or maybe most are motivated more for style than performance.
A few times, in other formums, I have suggested that the HHR SS suspension is pretty good as is, for street performance, anyway. It falls flatter than flat, could get a hostile response or ridicule.
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