Handling

[10594087]

Hi,

Maybe just a newb question but i would like to ask why when we change our rims and tyres to a slightly larger say from a 17x7 to a 18x9. The handling of the car feels stiff and not so responsive. I thought the wider base would of made a better handling car. I understand that the manufacturer have made the settings of the suspension to accomodate the stock wheel sizes say 17x7. If this is the case how do modify the car to suit the new rims and tyres. This has been the case with a few cars that i've owned and other people i know as well. Also even after a complete wheel allignment it dosen't make it better.

Thanks,
Ken

[10594087]

Hi,

Maybe just a newb question but i would like to ask why when we change our rims and tyres to a slightly larger say from a 17x7 to a 18x9. The handling of the car feels stiff and not so responsive. I thought the wider base would of made a better handling car. I understand that the manufacturer have made the settings of the suspension to accomodate the stock wheel sizes say 17x7. If this is the case how do modify the car to suit the new rims and tyres. This has been the case with a few cars that i've owned and other people i know as well. Also even after a complete wheel allignment it dosen't make it better.

Thanks,
Ken

[exFSAE]

Short answer: Bigger is not always better, and you can't necessarily just "tune it out" with suspension settings.

[Mbirt]

You're correct--the OEM has tuned your suspension for the wheel/tire combo which the car came from the factory with.

With significantly larger wheels, you're increasing the unsprung mass at each corner (unless the wheels are light enough to compensate for the size increase). An increase in unsprung mass could hurt every aspect of your vehicle's handling. Also, the increase in wheel width is only going to pay off in steady-state grip if you've chosen a good tire. Check out which tires are winning in DOT-legal auto-x and road racing classes.

When you say the car feels "stiff and not so responsive", you must be referring to the NVH increase from a shorter tire sidewall. If it's a good tire, the increase in ride stiffness should equate to increased responsiveness also from less sidewall deformation.

To take advantage of your increased grip from wider and stickier tires and recover some responsiveness, lower the car's CG and stiffen your wheel rates with appropriately matched springs and dampers. Install stiffer anti-roll bars front and rear to decrease roll. And before you go back to the alignment shop, look up what setups autocrossers with similar cars run. You might want to toe out both front and rear. Maybe some more caster is in order. Going too far with a street setup will make your car twitchy and prone to wandering, however.

Hope this helps. If I were you, I'd have stuck with the stickiest tire that fits on the stock-size wheel. But to each his own...

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mbirt:
You're correct--the OEM has tuned your suspension for the wheel/tire combo which the car came from the factory with. </div></BLOCKQUOTE>

Often the opposite.. but the idea the same.

Bottom line, wider tires and shorter sidewalls aren't just inherently magically good.