"the only difference being calibration of springs/dampers, wider wheels, and alignment specs."
there is no only about spring calibration!
there is no only about different dampers!
there is no only about different alignment specs!
the wider wheels they were using to fit wider tyres to a completely different enviroment. you cant pass that off as only. it is a very different vehicle. And what you are talking about is Alpina accepting certain compromises in the car being a nice road car, to make it more of a race car. the Alpina did fit 185/70VR13 CN36 onto its 2002 so the derogatory effects on handling are less than they are if you fit a modern tyre to a 2002 today, becuase CN36 is a carcass suited to cars with that sort of suspension. However it isn't as comfortable. the steering is heavier, there are compromises made to make it a more racey.
And finally, taller profile sidewalls respond to steering inputs more slowly than low profile sidewalls. This is, as you say, just physics.
Ok; that would be true if the amount of tread in contact were the same, which it isn't by any means. If you compared a lower profile tyre to a taller tyre with the same contact area/footprint, then yes the lower profile tyre would turn in quicker. but we arent doing that.
The picture on my last post shows the massive difference in how much foot print is on the road between a 205/55R16 P7 7.5" footprint compared to a 5.5" footprint of the 195/70R14 CN36 (It's shame i haven't got a 205/70VR14 CN36 on the shelf it would prove my point better.)
I have said this before, but a modern 50% profile tyre will put a huge amount more rubber in contact with the road tha a 70 profile tyre of the same section. a lower profile tyre has a wider foot print in relation to its section width.
Oo! i have had an idea. I do have a 205/70VR14 XWX on the shelf. this picture pretty clearly demonstrates this point.
Yes the likes of Ford and GM might well base their tyre choice on cost, i suppose i don't think it was completely open cheque book with BMW, but it wasnt price that determined the size, and they were buying Michelin XWX. so it certainly wasnt price that determined that. And Alpina chose CN36 so that wasnt a bank balance choice. These are BMW cars where handling is the key. they are built for windy roads, and AutoBahns, point and squirt from traffic light to traffic light.
Agree completely. Additionally, the tire technology limitations of the period are vastly different than today. BMW would probably make an entirely different choice in wheel and tire for the e9's if todays technology were available to them back then.
If BMW built the E9 today they would have very different geometry in it to suit a modern tyre. If they painted the Mona Lisa today she would be wearing a track suit and a didgital watch.
Tyres like the CN36 and the XWX have the right structure for your cars. they also have modern build quality and compounds. so yes they are better than period tyres, but their carcass presents the foot print to the road in a manner suited to your geometry.
Blimey i cannot be explaining myself very well. After a series of long posts and i don't seem to be able to get accross the fact that tyre fitment is a balance. I'm trying to get accross a few point:
- What makes a good racing tyre, compromise, comfort, tramlineing and nice light precise steering.
- Grip and handling are different things.
- Modern cars are totally different and can take advantage of the modern tyre construction that is not suited to older cars with totally different geometry.
- Car manufacturers dont just guess a tyre size, and then just buy off the cheapest supplier. (Specially not BMW.)
The combination of these adds up to an E9 will be at its best,
as a road car, (not a race car, or one that thinks its a race car, or one owned by someone who likes the look of tall wheels,) fitted with a high quality tyre in the size the cars manufacturers extensive testing proved to be the best. And importantly a period carcass will give the best all-round balance
as a road car. At present that is the 195/70R14 Pirelli Cinturato CN36.
Anyway i seem to be struggling to get these points accross, so hopefully i can lighten the subject by demonstrating how seriously we take tyre testing, with this tyre safety film i made a few years ago.