[wspohn]

I looked for a Z4M coupe but couldn't find one as they brought in very few, and then found a Solstice GXP coupe that I picked up new and have been very happy with.

Spring forward 4 years and a friend who is a retired dentist told me he was thinking of buying a new summer top down car, as his wife had said she'd like the Miata he'd been using for that purpose.

I told him to look at Kappas, but he has always been a BMW fan, so I steered him toward the Z4 series and he came across a low mileage Z4M convertible that I told him he should jump on. He did. And the bugger got the same blue colour I had been looking for!

They come with a lovely sounding straight 6 engine(especially when it zings up toward 8,000!) putting out 330 BHP, 40 more than a GMPP tune Kappa, but weighs about 300 pounds more.

We took the cars out on a sunny day up a nearby mountain to give them a run. He is a casual driver that just enjoys responsive cars; I am a race car driver familiar with setting up cars for competition. The results were interesting - while I've driven the Z4M before, I've never had the chance to compare against a Kappa on the same day.

The BMW is tight and raw, which surprises one a bit. The handling is quite good, better than a stock Kappa but not as tight and with lower limits than my massaged chassis. At the limit, the BMW is a bit more ragged but it is a lot of fun to drive hard - you need to drift it to get the most out of it.

Excellent controllable brakes, but a somewhat low pedal (more travel than the Solstice), a bit of push in the front end easily overcome by a bit more accelerator (similar to the Solstice with the ZOK bars on my car), and good transition balance.

The Solstice on the other hand was crisper, needing less horsing around to drive fast, and seemed just handier all round. When we took off, I out accelerated him up to as high as we felt safe going - can't beat the torque of the turbo engine!

I could be happy with either car, but having the chance to drive both makes me pretty happy that I ended up with the Solstice. Sure, the plastic GM interior is inferior to the more expensive German item, but I don't buy cars for interior looks I buy them because they are fun to drive, and while both cars would deliver that, in slightly different ways, I'm certain that the BMW delivery would be at a significantly greater price, both in terms of acquisition cost and maintenance cost!

 

[Mehran333]

Gratz on the amazing experience Bill, wish I could drive that BMW! :thumbs: what did he have to say comparing the cars himself? OR did you not let him drive your car :lol: Ha.

 

[L-N-F'n]

Obviously a Solstice coupe knock off. LOL

 

[wspohn]

Actually, I didn't let him drive my car, I drove both of us in each car and then we went for a run each in his own car (which is when he lost the acceleration contest) - I consoled him by telling him how much better his car sounded.

I build my cars and have always been very reluctant to allow anyone but me drive them. Probably comes from building race cars for so many years - if it breaks, it better be me that broke it!

 

[twowheeladdict]

Does the z4m have a targa top?

Personally, I enjoy driving the solstice with the top up, but much prefer the top down. Don't think I would enjoy a hardtop sport car.

 

[wspohn]

The car my friend bought was a convertible with soft top. That's what you'd no doubt opt for. The coupes like the one pictured did not have a removable top. I have never had my Solstice coupe top off - I'd have preferred that it be welded in place!

 

[Mehran333]

Bill, you have no idea how stubborn I am either. When my A/C failed, my parents offered to buy the compressor for me and have it installed.. I threw so many fits taking it to 3 mechanics. After everything, they paid $600 and I no longer want people to touch my car. It's my only child.

 

[LatinVenom]

Bill, thanks for the post and your views. Interesting to note as you said, how the few upgrades to our suspension makes our KAPPA a great handling car.

 

[Seltzinator]

Edify me here. What are the best suspension and handling upgrades for the Kappa, in terms of bang for the buck?

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[LatinVenom]

ZOK suspension in total.
Or ZOK sway bars and ZOK shocks and springs.
Backbone/Probeam(or different manufacturer)/VenomBrace
You could also delete the ZOK shocks and springs and go with coil overs from other manufacturers.
A good set of tires!!!!

 

[TomatoSoup]

What LV said... but in 'bang for the buck' order, I'd say:

1) Backbone and Probeam
2) ZOK sway bars (maybe rear-only, for non-track cars)
3) Tires
4) ZOK shocks and springs -or- other coilovers (if you don't mind height and ride compromises)

1) and 3) are absolute requirements (but #3's cost drops it in the 'bang for the buck' order)

 

[Somnambulator]

a good friend of mine has had an 04 z4 2.5i for some time now. the 2.5 is the small engine, basically making it slightly faster than a miata considering the weight pf the car (3200 i think). its a nice car. it rides very smooth...smoother than my gxp with stock suspension and a rear beam, but the gxp is tuned for speed and high speed handling.

the interior is vastly, completely, superiorly in a different galaxy. its a bmw,

also because its a bmw, however, **** is exxxxxxxpensive to repair. i remember a few of us changing his thermostat... $75 just for the part and it wasnt bmw branded. thats just one example of many.


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[Shadofax]

What LV said... but in 'bang for the buck' order, I'd say:

1) Backbone and Probeam
2) ZOK sway bars (maybe rear-only, for non-track cars)
3) Tires
4) ZOK shocks and springs -or- other coilovers (if you don't mind height and ride compromises)

1) and 3) are absolute requirements (but #3's cost drops it in the 'bang for the buck' order)

If you happen to have some mileage on your stock tires and they need replacing anyway, you should move them back up in your order, just a maintenance item, while everything else is an add on cost.

And what happened to the front brace, not on your list? I think it really helps stiffen up the front, perhaps this is needed less if you opt for the zok sway bar up front?

 

[Shadofax]

The car my friend bought was a convertible with soft top. That's what you'd no doubt opt for. The coupes like the one pictured did not have a removable top. I have never had my Solstice coupe top off - I'd have preferred that it be welded in place!

I'd imagine the braking was better in the BMW as well?

 

[TomatoSoup]

If you happen to have some mileage on your stock tires and they need replacing anyway, you should move them back up in your order, just a maintenance item, while everything else is an add on cost.

And what happened to the front brace, not on your list? I think it really helps stiffen up the front, perhaps this is needed less if you opt for the zok sway bar up front?

Frankly, I didn't notice the handling gains so much for the front brace. Certainly not the same difference as the backbone/probeam, made anyway. However, it IS cheap

 

[wspohn]

I'd imagine the braking was better in the BMW as well?

Stock to stock? Probably.
There isn't anything wrong with the Kappa brakes and I get tired of people claiming there are to try and justify the expensive fitting of huge rotors and calipers for what in the end has nothing to do with performance, just with bragging rights.

I switched my car to EBC Red Stuff pads early on and found that they improve initial grip immensely over whatever crap compound the factory stuck in there off the line, and unless you compete that's all you need. If you DO compete, I expect that switching to Yellow Stuff (or equivalent would still be adequate.

Is the stock pad compound better on the BMW? I'll bet it is. They didn't cut many corners on those cars. You just have to sit in them to appreciate the difference in interior quality between them and our generic plastic interior. But you pay for it!

 

[wspohn]

Frankly, I didn't notice the handling gains so much for the front brace. Certainly not the same difference as the backbone/probeam, made anyway. However, it IS cheap

X2
Small incremental improvement compared to the quite large effect of the rear braces.

 

[LatinVenom]

That was probably because you had the other 2 already in place,
To see what it really does, just put it on by itself and it will become very apparent as to why is need it.
The suspension on this car needs to be close if you want a 1st class handling car.
All of the pieces listed are a must or you will not get the total handling package.

 

[wspohn]

That is correct, LV - I had the rear stuff done already. I would expect the effect to be greater if that was the only thing added to an otherwise unmodified car, and agree that the package is the way to go. I'd add that your front brace always made far more sense to me than the others that built bridges up over the various bits you might need access to in the future, thus causing future maintenance headaches and extra work! Have you ever seen any evidence that the flat brace is inferior to the more elaborate versions in terms of added stiffness?

 

[LatinVenom]

To answer your last question NO. Even Dave from DDM will tell you the same.
By the way my Brace was designed using CAD software. Also a couple of engineering friends were the ones that did all the calculations after I showed them my initial muck up.
I gave DDM the rights to use it, that is why it is called the Venom Brace in their catalog.
This way members could have a one stop shopping for the suspension components for our car.