I also got some new rubber. Since I'm planning on getting some new wheels within the year, I went with the cheapest rubber available in 205/45-17... Kumho Ecsta AST. I got them installed and on the first turn out of the tire place, I thought my rear swaybar was disconnected. SOOOO much more sidewall deflection than Yoko ES100's. I've driven on them for a week now and I'm getting used to the lower grip levels and more body roll. With the Yoko's, the weight would shift and the outside front would bite. Now, the outside front feels like it rolls over on itself. This weekend, I stiffened up my H-Sport comp to the middle setting today and it seems to help out.

 

Welcome To H speed rated tires. Mini is such a ridgid package it really points out the lack of sidewall stiffness.

The 1st factor is sidewall flex from softer, lower speed rated sidewalls.

The 2nd factor is treadblock flex, Tall brand new tread blocks are extra squishy. Think of a new pencile eracer vs one thats allmost gone.

3rd contributing factor is perception due to heat cylcling and tread block flex. Your comming off short tread blocks that squirm alot less.

When a tire is new the rubber is soft, as it heats up and cools down from driving then parking - the tire is heat cycling. The more heat cycles the less flex.

The comming from short blocks that are super firm from heat cycling, onto new tall tread blocks with no heat clcyling = a big shock.

It will get a bit better with time, but the sidewall stiffness - will allways be a factor. You'll notice this in quick transitional lane changing.
Think of guiding the tire, les snapping your steering inputs.

This "Sugestion" vs "Forcing" is the same thing that allows me to drive agressivley on snow tires with minimal compromise.

Alex

 

Good stuff there Alex. It's been a while since I had new tires, but your analysis is spot on.

 

Here is a shot of my new tires on. It is my feeble attempt at HDR.