I test drove CMS with summer tires and compared to GTI the ride felt too stiff, bordering on harsh, without being any better in handling.

I know part of it is run-flats. Do stock all-season run-flats have better ride? Do they sacrifice handling a lot?

 

Did you test a CMS with 18" wheels? The 17" wheel/tire combination will ride better, with little sacrifice in handling. We chose the 17" all-season tires with Sport Suspension option and we like it.

Some run-flats are better than others. I would say that the Conti run-flats are somewhat smoother riding than the Pirellis for instance. In general the all-season tires supplied with the CM will ride a bit better than the summer tires, but it varies by make and model.

Check the Countryman Wheel and Tire section for much more information:
https://www.northamericanmotoring.co...nd-brakes-367/

 

I agree with DR61.

Much of the ride compliance difference across tires is due to the width and stiffness of the sidewalls. Thus, in general, and with all else equal (including tire diameter):

Run-flats provide a harsher ride than non-run-flats (RFTs have very stiff sidewalls).
18" tires provide a harsher ride than 17" tires, which are harsher than 16" tires, etc.
Summer tires provide a harsher ride than all-season tires.
The higher the performance category, the higher the ride harshness.

There are a few exceptions to the rule, but I haven't seen many looking at Tire Rack data.

As your last question suggests, handling crispness is generally inversely related to ride comfort. How much of one we're willing to give up in order to get more of the other is a personal decision. It may be that the ride comfort difference between RFTs and non-RFTs will be noticeably greater than the ride comfort difference between summer RFTs and all-season RFTs. That's because all RFTs have very stiff sidewalls.

 

Interesting perspective here. I am in the shop since last Thursday (long story), but my loaner is a '12 All 4 without sport suspension with Pirelli Run Flats (same tire I have on my '11 All 4 with sport suspension) I can honestly say that the sport suspension does "harsh" up the ride considerably. However, I am glad I have it because the handling and cornering is so much better. The RF tires on the non-sport suspension isn't cushy by any means. a pot hole, is still a pot hole. Ultimately I will go non- runflats, and love my sport suspension. Dealer said that I wouldn't want it, now I'm glad I have it after I have had a good amount of time behind the wheel with both versions.