I am planning on upgrading the 16" Bridge Spoke RunFlats with 17" aftermarket Konig Feathers with non RunFlat Yokohama S-Drives 205/45/17. Will the ride be better, worse or the same?

It will be on 09 MCCS with non Sports Package.

 

Good question. I'm curious, too.

 

Define "better" and "worse"... comfort wise the 16's longer, narrower contact patch means better tracking (straight line stability) and less impact harshness, but slightly less of a "go-kart feel"... and the taller sidewall also means a little more "give" in the corners, but some of that is mitigated by the runflat's stiffer sidewall.

The 17" Feathers with S-Drives' shorter, wider contact patch = more "go kart" feel, but more "immediate" at the limit as well. Shorter sidewall gives less rim protection from potholes and MAYBE a little stiffer ride, but since they're non runflats that'll mitigate that a little. You'll also experience more "tramlining", where the tire wants to squiggle a bit more on a rutted road.

Quiet? Well, the 17's should be a bit quieter to begin, but in time they're likely close. I've not driven the S-Drive in specific, but drive the 205/45/17 Michelin Pilot Exalto (pretty close - Ultra-High-Performance, non runflat, reported to be a more quiet and a good wet tire compared to other UHP tires - similar characteristics to an S-Drive).

I guess the big tradeoff is the more "immediate" feel of the 17 (negative = tramlining) vs. the better straight line stability and comfort of the 16. Ultimate grip will actually be slightly different, but pretty close. Oh, and looks.

BTW, the Michelins are great, quiet, great in the wet and dry, but soft. They also have a bit of a "ring" to them at certain speeds - not annoying, but definitely there. Far better than Pirelli Euphori@s in all aspects of performance except maybe wear, where the jury's still out (at worst they're equal).

 

I change from 16" Bridgespoke with GoodYear Runflat to 17" Non-Runflat General UHP, the ride is 20% to 25% better

 

Could you be more specific?

 

Hey Dixon,
Help me understand why a contact patch on a bigger wheel is shorter. I'm not seeing it...

Thanks.

 

How do you like the General UHP tires? People either tend to love or hate them. Does it feel like Marshmallow type of ride?

 

LOTS of dynamics at work, but a dramatically simplified version is this: All else equal, (basically load or car weight and tire pressure), the contact patch of any tire will have the same area as measured in square inches. Think of it as PSI (pounds per square inch). For a given number of pounds, you get a given number of square inches.

If a Mini weighs 2700lb, and carries 60% of its weight up front, each front tire carries 810lb. At 33psi, each tire carries 33 pounds per square inch, so requiring a contact patch of only about 24 square inches - about the size of your hand.

With a narrower tire, this 24 square inches is limited in width, and so gets longer relative to width. With a wider tire the contact patch is shorter and wider.

A wider contact patch is more sensitive to road ruts because forces can be exerted at the edge of the contact patch, having more leverage back to the steering wheel. Likewise, a wider contact patch is more resistant to lateral loads because it's, well, wider, and usually stiffer (more of a performance tire). The effect is called "tramlining".

(note: this simplified description ignores the effect of the dynamics of a rolling tire, "slip angle", tire construction, and the difference in wheel size between a 16 and 17 and resultant sidewall height and stiffness differences. This is meant as a guideline. More technically accurate descriptions can certainly be found, just wanted to cover the basics.)

Some references:
Contact patch:
http://www.tirerack.com/tires/tirete....jsp?techid=10

Tramlining:
http://www.tirerack.com/tires/tirete....jsp?techid=47

Hope this helps - now off to the car show!

 

Cool stuff. Thanks for sharing the links!