Looking for some advice or experience opinons

[Enigmatik]

Check the springs carefully as the OEM rears are prone to snapping off the dual rate 'pig-tails' and can be hard to spot. Most cars of our age will have snapped at least the rears, mine first went before the first MOT, then again a few years later so mine is on it's third set. I gave up on the dual rate type and fitted single rate springs that have lasted twice as long so far, with no noticeable deterioration in ride TBH. spring1.jpg

I take it I'm not going to know until they come off? Which brand did you use? There aren't any real bangs or noises from it, it's pretty solid and quiet. Slight rub somewhere on the passenger front on a off camber turn and the previously mentioned bottoming out.

 

[Mr Tidy]

Those are really good looking wheels.

Original BMW 18" wheels for Z4s were staggered, but after-market ones may or may not be! I bought a set of 18" CSL Replicas a few years ago and they were 8J all round. I'm sure I've read a few people saying they reckon their BMWs handle better on a "square" set.

Anyway I can't see why 235 section tyres would be a problem.

 

[Enigmatik]

Thanks Mr Tidy. I didn't know CSL replicas were available in 18", I saw a 19" set going in the for sale section and really liked them, but think the increase wouldn't work round here. Might keep my eye out though. I read a few people saying a square set stopped the rear pushing the fronts wide, but limited experience myself.

My only thoughts against 235 would be:

1) do I gain more grip at expense of acceleration
2) do they reduce wet grip due to larger surface area
3) would the point they break away be so high, it might instill over confidence. i.e I think I read the reason Toyota put small narrow tyres on the gt 86 was so that you could have a degree of fun without being right at the edge/too far gone

 

[Ewazix]

Check the springs carefully as the OEM rears are prone to snapping off the dual rate 'pig-tails' and can be hard to spot. Most cars of our age will have snapped at least the rears, mine first went before the first MOT, then again a few years later so mine is on it's third set. I gave up on the dual rate type and fitted single rate springs that have lasted twice as long so far, with no noticeable deterioration in ride TBH. spring1.jpg

I take it I'm not going to know until they come off? Which brand did you use? There aren't any real bangs or noises from it, it's pretty solid and quiet. Slight rub somewhere on the passenger front on a off camber turn and the previously mentioned bottoming out.

You can see spring tail breaks-offs with a careful inspection by a light and mirror, easier if it's jacked up with the wheel off of course. I used Sachs which have turned out be be at least twice as durable as the OEM springs and work well. Being single rate they are shorter off the car and sit slightly lower at rest but do not compress quite as far. Theoretically they should feel firmer over low speed bumps, but in reality the move away from run flat tyres gives you slightly more compliance so the two balance out in my experience. My SE car was on factory non-sport suspension, with the Sachs it sits mid-way between standard SE and Sport at rest (people mention it looking lower) and I think is a good compromise between sport & standard on a car with non-RFT's.
As far as wheel spec's go, you can overthink it IMHO. I've messed up the the driving experience of more cars by upping wheel/tyre sizes beyond factory sizes than I care to remember, it's an expensive way to spoil a balanced car for road use.