[milesr3]

Originally Posted by HighlandPete

I know many will laugh, and probably choke on their supper, but cars like the Peugeot 405 although not a sporty car, had some very good driving dynamics.

ISTR with older Peugeots (although it could be the 406 vintage) that a lot of this was down to the quality of the dampers that they used to make in-house rather than buy in.

Having a damper that was well matched to the spring rate, corner weight and tyre size was something that BMW used to get so right before big rims and runflats became mandatory equipment. This is impossible as soon as you offer a choice of fashionable wheel sizes as none are 'right'.

[Em135eye]

The last iteration of the Clip Trophy with Sachs dampers certainly worked pretty well...

[Em135eye]

Can't say I've ever stepped out of a car after a spirited drive and thought "my that car had great turn in." I generally find that when I turn the steering wheel, the front wheels turn roughly proportionally to my input. Feedback - yes. Turn in? Errrmmm... Not something I hear mentioned either.

Handling is subjective but most will agree that for the sweetest handling, small sports cars generally rule the roost.

[F31-340i]

Originally Posted by 335diesel

Can't say I've ever stepped out of a car after a spirited drive and thought "my that car had great turn in."

Turn in is a fairly commonly used term - quick google on "low profile tyres"...

A low profile tyre has a smaller sidewall. This makes the tyre stiffer, which has a number of effects. The first is that the tyre doesn't flex so much as you apply steering angle, making the car react quicker to steering inputs (improved turn-in) The second is that the tyre flexes less during high-speed cornering, keeping the contact patch closer to its normal position. This makes the car's handling more secure / predictable during high-speed cornering. Another is that the tyre is less flexible when encountering bumps, so the secondary ride (the car's behaviour over high-frequency, low amplitude surface irregularities) is less smooth. Also, the distance between tread and rim is reduced, meaning the wheel is more vulnerable to damage from impacts with kerbs, potholes or debris on the road.

This difference in steering reaction (turn in) is tangible as you change tyre profile (which is what you do when you change wheel rim size for a given rolling radius). It is equally marked between e.g. 19" nonRFT and RFT tyres. I'm surprised you didn't notice any difference going from RFTs to nonRFTs - I found the difference very noticable.

Poor turn in is a very noticable feature that ruins the drive in many crap cars. I have vivid memories of the worst car I have driven for "turn in" - a Ford Mustang Convertible. It was like driving a water bed. A combination of soft springs, poor damping & relatively high profile tyres. In theory the ride was 'good', but it was wallowy almost to the point of sea sickness....a truely dreadful car. It was a hire car in San Francisco - it didn't help that I'd stepped out of my E46 M3 (on 18"s) at Heathrow....

[Em135eye]

Nope - I didn't notice a marked difference in "turn in" - just a better ride and no tramlining.

Anyway, 335ds (and 335is) have proper fully hydraulic and beautifully weighted steering so more "power" to turn the wheels quickly anyway ;-)

Good on you for running an E46 on 18s though. There is some hope ;-)

[HighlandPete]

I believe it is over simplification to see big rims = sharp steering. There are so many factors which can have a bearing, something as simple as tyre selection, has a impact on steering response.

I understand why some love the RFT, for the way they sharpen some responses, low slip angles, etc. But it is the negatives in steering which we also have to live with. Personally I don't want the extremes, I don't like a wheel that tries to snatch out of my hands, that isn't feedback in my view.

Back in 1996 when the E39 5-series was launched it came on 15" wheels and the upgrade, even on sport suspension, was a 16" wheel. AutoCar mentioned the 'fat' 225/55 section, how things have changed. But the review and full road test of that car, a 528i on sport suspension and 16" wheels, was full of praise for the chassis, the handling, the damping, composure, etc., etc. It got the full 5 stars for ride. A near perfect car they concluded.

My sort of drive.

HighlandPete

[Em135eye]

My Dad had a 323i (E20 shape) from new with an LSD fitted.

He still reckons it's one of the sweetest handling cars he's ever had - and he's had some fairly "serious" motors. Narrowish tyres on high profile rubber.

I remember him cleaning it constantly. I wasn't allowed (I was about 5 at the time) for fear of scratching it! Sounds familiar! Our little one (2 and a 1/4) is only allowed to "help" with the wheels!

[HighlandPete]

Do you mean the E21 or E30 (1983 onwards)? I used to drive an E30 323i (company had it new) with sports wheels (14" I seem to remember) and sport suspension. Definitely a car that drove well without drama. Needed some respect, as the rear end could bite back.

I fancied the E21 323i when it came out, but stuck with the 528.

HighlandPete

[Em135eye]

Oops - I meant E21. The first iteration of the 3 series.

Looked a little bit like this:



A few "essential" options almost doubled the list price and although it was a brilliant car, he had major engine trouble about a year into ownership and had to sell it for a fairly massive loss.

Oh well!

[F31-340i]

Originally Posted by HighlandPete

I believe it is over simplification to see big rims = sharp steering. There are so many factors which can have a bearing, something as simple as tyre selection, has a impact on steering response.

I understand why some love the RFT, for the way they sharpen some responses, low slip angles, etc. But it is the negatives in steering which we also have to live with. Personally I don't want the extremes, I don't like a wheel that tries to snatch out of my hands, that isn't feedback in my view.

Back in 1996 when the E39 5-series was launched it came on 15" wheels and the upgrade, even on sport suspension, was a 16" wheel. AutoCar mentioned the 'fat' 225/55 section, how things have changed. But the review and full road test of that car, a 528i on sport suspension and 16" wheels, was full of praise for the chassis, the handling, the damping, composure, etc., etc. It got the full 5 stars for ride. A near perfect car they concluded.

My sort of drive.

HighlandPete

I don't think it is an oversimplification to link tyre profile directly to turn in sharpness. It is a fairly simple easy to visualise link after all - other things being equal.

I'm not convinced there are ANY handling/steering downsides to large rims and RFTs. The ride maybe hard, but in my experience there are no issues with them affecting steering feedback or increasing wheel snatch (not that I've ever found this to be a problem in an E91).

I can see why people prefer the handling/ride compromise offered by higher profile wheel/tyres and non-RFTs - but its surely all about the pursuit of improving the ride, and not handling?

[milesr3]

Originally Posted by ///ajd

I'm not convinced there are ANY handling/steering downsides to large rims and RFTs.

What about unsprung mass? This is directly proportional (inversely) to ride quality, traction, handling and steering control.

This is one of the ways in which BMW have lost the plot. Why build your suspension components out of alloy and then hobble them with heavy wheels and tyres.

[Em135eye]

I must rush out and get some of these then....



Miles is right - big wheels weigh a LOT. I've checked the weights of many OEM BM wheels and almost all 19s (even Performance ones) weigh a hell of a lot. Even the most basic 17s weigh far less - about 25% less in many cases. Then add massive wide rubber and you have a wheel and tyre set weighing an awful lot more - add a set of light wheels to a bike and the difference is immense. Similar applies to a car.

Not only do these vast wheels weigh a lot, they are often extremely fragile, partly due to the design constraints but also the almost non existent protection from the elastic band profile tyres.

Again we live in the UK - which isn't a billiard board smooth racetrack. I'd hate to panic every time I saw a slight pothole or road imperfection. That to me is compromising the fun of driving and also slows you down - not really a performance enhancer.

I think I'm pushing it now. I fear imminent total exclusion again...

[HighlandPete]

Originally Posted by ///ajd

I don't think it is an oversimplification to link tyre profile directly to turn in sharpness. It is a fairly simple easy to visualise link after all - other things being equal.

I'm not convinced there are ANY handling/steering downsides to large rims and RFTs. The ride maybe hard, but in my experience there are no issues with them affecting steering feedback or increasing wheel snatch (not that I've ever found this to be a problem in an E91).

I can see why people prefer the handling/ride compromise offered by higher profile wheel/tyres and non-RFTs - but its surely all about the pursuit of improving the ride, and not handling?

If you say "all things being equal", then large rims are the easy bolt on, I agree with that, but in my experience you do get some negatives from the steering.

I don't personally find run-flat tyres to be consistent enough to enjoy them. Every day is different, temperature alone, then the rain cooling them, just too tight a tolerance for predictable driving. Cars I've driven definitely have bad steering reactions due to the run-flats.

The ride/handling balance is a compromise, even BMW tell us that, it is just what is most important. To me, on the roads I use, I need to sacrifice the sharper edged handling, as the ride is more important, but big wheels also are harder to live with on poor roads, IMO.

By the way, how do we define what is a good handling setup for poor road surfaces? I personally believe there has to be a few more compromises, to get a predictable car.

But each to his own.

HighlandPete

[Em135eye]

Running ultra low profile tyres with rock hard RFT edges is never going to make a happy car. Simple physics.

Also a slightly separate (but related) point - what's happened seeking to the most important performance enhancer of all - lightness?

Big rims, huge tyres, big spoilers, tonnes of optional tech, etc, etc all weigh a lot - on a car which IMO is too heavy even bog standard without a single option. And yes, even the M3 is extremely heavy.

A "fully loaded" M Sported up 3 series model with optional 19s must weigh significantly more than a "poverty spec" version with the same engine?

It's hard to find out the exact weight difference but "fully loaded" up, a 110 Landy and it weighs over 150kgs more than a bog standard version. I'm sure it's not as much on a 3 series but I bet it's not far off 100kgs.

[HighlandPete]

Originally Posted by 335diesel

....I think I'm pushing it now. I fear imminent total exclusion again...

Won't be alone....

I had the first chance to really try the winter tyres today at warmer temperatures (5 - 6 degrees) and no snow, or ice about. Now these weedy 17" wheels are same on all corners, and I have to say you can immediately tell the rear is benefiting from the lighter wheels and unsprung weight. The rear suspension works more smoothy, over the broken stuff. BTW, the RFTs on the same rims, never felt like this at the rear. As the summers are a staggered setup, the current steering balance is more neutral, "sharper" into the bends, tyre pressures are as I'd run the summers, 2.4 & 2.6bar. So rather than a bit of understeer, which slows the steering reaction, it has faster steering response and is verging on oversteer.

Now to your setup, 335diesel, you're on a 'square' setup, plus with your ContiContactSports (they are 225's aren't they?), you haven't moved up a size and softened the steering response? (Something a lot of big wheel users do, add a size or two and take away some of the sharpness). Makes for a tidy setup, IMO, so easy to see how and why you find it ideal, particuarly as a compromise to get a good blend of ride and handling balance.

HighlandPete

[kaishang]

We should get together and form a 17 inch exiles club.

[F31-340i]

The unsprung weight comment is valid, though lets face it no OEM cast BMW wheel is exactly lightweight.

I haven't personally noticed a negative handling difference from 18" to 19" sizes in this respect - just the opposite from sharper turn in. The turn in issue isn't everthing when it comes to handling but at the end of the day its the only thing I really noticed. I suppose at the end of the day I just like the "go kart" effect.

I should be clear that I did NOT get 19"s in the belief that they would improve handling - this was not a motive - I got them as (and I'm not embarrassed to admit) I like the 225M style and perversely worked out I could work it to be cheaper option than getting new 18" RFT tyres. I was actually worried that the harsher ride would annoy me, and intended to jump straight to non-RFTs.

What I actually found was that the ride was still tolerable, and when I did ditch the RFTs I actually sort of missed them and the sharp handling they gave.

I can only go by the slightly dissappointed memories of that first drive on non-RFTs (noting that the ride was better).

[Em135eye]

ajd - I agree on one point there; 225Ms do look nice

Highland - yep my "old man" set up seems to work well but as with everything, owners will always justify the hell out of what they've spent their hard earned cash on!

Should you ever get extremely lost and end up in Cornwall, like Kaishing, you're welcome to try my set up out. 225/45 17s all round, Sports suspension, non RFT CSC3s. And a beige cardy with leather elbow patches...

[kaishang]

Originally Posted by 335diesel

/ And a beige cardy with leather elbow patches...

This would match my beige leather and woodgrain interior.

[HighlandPete]

There was an article in CAR magazine a few issues ago where they 'back to back' tested an E30 M3 with a 135i coupe, across some interesting roads. The big surprise was the M3, on its small wheels didn't tram-line, was never deflected off course by over firm suspension, and it rode very well. Also the steering, although slow by todays standards, weighted up in the corners and transmitted enough information from the rubber to let you know exactly (italics CAR) what reserves you've got to lean on. The rear rubber never felt troubled either.

What a revelation.

HighlandPete

[milesr3]

Originally Posted by kaishang

We should get together and form a 17 inch exiles club.

Where do I sign?

When I built a car I went to stupid lengths with alloy bells on the disks, ultralight brake calipers and alloy dampers to keep the unsprung mass down but the most important part was being able to use these 13" wheels (3.7Kg each) with crossply tyres (3Kg lighter than a radial).



How badly do you think the car would have handled with 19" rims and a nice set of 30 profile runflats? The gyroscopic effect alone from turning a corner would have flipped it into a hedge

[milesr3]

Originally Posted by HighlandPete

What a revelation.

There is an article on the new 1 Series M Coupe in the current Evo with an interview with the guys responsible for developing it. They claim that they didn't use runflats because it makes the steering response 'too wooden'.