Z435is Reality v. Myths

I have now had the opportunity to spend 2 months driving my Z435is. The automotive press is overly critical of the vehicle. I am basing my opinions on having been a Z4 owner for over 4 years (replaced my highly modified 2006 Z4 3.0si) and driving the car(s) on windy canyon roads on a nearly daily basis.

First off, the bad news. Yes, the Z4 35is (and I assume the 35i) have more understeer than one would expect and less precise steering and feedback than one needs to properly take the car on up and down the "twisty turny" roads at its real potential. However, unlike the suggestions in some of the more absurd automotive press, the car does not handle like a "front wheel drive sedan." I know this from experience. The car handles very well. Not as well as my road racing 06 Z43.0si, not as well as a Cayman S or Boxster S - but it's faster than all of them and far more comfortable to drive on a daily basis. In every possible way, it is a vstly superior vehicle to pre 2009 Z4s. The Z4 is also a vastly superior car to its competition from Porsche roadsters in every category but turning. In other good news.... how hard is this to fix? Uh, not very. I'm working on solutions to the handling issues that might include some or all of the following:

1. Dumping the RFTs on the 19" wheels and replacing them with better gripping tires;
2. Playing around with front and rear sway bars to loosen up the rear and get more traction in the front;
3. Slightly raking the car's stance noseward;
4. More aggressive springs - maybe H&Rs;
5. Looking for a way to make the steering feedback and dampening more accurate through re programming.

IF ANYONE HAS TRIED ANY OF THESE OR SOMETHING ELSE LET ME KNOW!

A lot of critiques of the 35is ignore the vehicle's chief virtue. It functions as a luxury car, a sports car, a top down roadster, a daily driver coupe and a GT. It's not the very best car in any of those categories but it is, out of the box, warts and all, excellent in all of them. There is simply nothing like it on the market and they can be had, brand spanking new, in the high 60K range absent tax and other add ons and fees.

Originally Posted by Wavesofblue

A lot of critiques of the 35is ignore the vehicle's chief virtue. It functions as a luxury car, a sports car, a top down roadster, a daily driver coupe and a GT.

Yes, it is the ultimate compromise machine, and I definitely felt this when I drove it. But unlike you, I don't consider this a virtue. Having owned a Z4 3.0si and M Coupe, I was hoping for something a little more focused, something with a few more exposed edges. Instead we have a slightly sportier SLK. BMW thought they would expand the market for the car by softening it. Thankfully it's sold every bit as poorly as the previous generation. Hopefully the next Z4 and the Z2 will go back to the previous formula.

With all respect, I must disagree. Go ahead and drive a pre 2009 Z4si 400 miles and tell me that the new Z4 is a " compromise." Multi role capability is a virtue - in everything from military small arms to combat jets to cars. Also, if you drove the car you had to note that the power train was already - out of the box - the master of any car in its class. The 7 DCT is already a parctical match for Porsche's vaunted PDK tranny. By the way, don't jump to the conclusion that the handling flaws were a marketing notion by BMW to expand sales. A lot of it has to do with the fact that the 35is makes a helluva lot of torque and the handling issues are likely the result of rushing the car to market before refining the chasis and suspension. But again, it is my belief that all of the weak spots can be polished by just getting the front end to stick down a bit better. As I said - not an insurmountable challenge.

The 35is wil be one of my "cheaper" track cars.. Planning to just throw some Pirelli Trofeos or Pilot Sport Cups, HR springs and upgrade pads and fluid. It wasn't as bad as what the media described it to be when I took it for a spirited drive through the hills. Understeer can be dialed out.

First off...man...you have a nice collection! Anyhow, I agree the RFTs are the single biggest problem with a car already balanced towards understeer. But looking at your tire choices I think you could save money on tires. I agree with you 100% about the H&R springs. I am not sure why you want to upgrade pads and fluid. The stock braking system seems good to go as is. Have you noticed something I have missed? If so, please tell me. By the way, if I were going with upgrading the braking system I'd also likely use all steel brake lines. I think you can also change the camber of the front tires and tighten up the rear sway bars for low cost.

I dont know if you have thought about engine upgrades. I am considering the Dinan flash to take the car up a notch. But frankly, until I get the understeer out of the car and have a better feeling of the road I dont see any reason adding 50 horses. I like the expression "always adjust the driver before the car" in that respect. Supposedly with the Dinan phase 2 upgrade the car will do 0-60 in under 4 seconds. Now youre gonna need some new brakes!

Originally Posted by darbyogill

Hopefully the next Z4 and the Z2 will go back to the previous formula.

Z2

BMW Z2: Concept in detail

The Z2 is a two-seater and Munich product planners are considering coupe and soft-top roadster versions. Based on the UKL1 front-drive transverse architecture, standing for untere klasse in German. It's at the core of BMW's plans to become more efficient at making small cars. Power for the new UKL1 front-drive BMWs comes from three- and four-cylinder engines, spinning the front wheels. The Z2 is pencilled in for a launch in 2016, at around £20,000-£25,000. That's top-end MX-5 territory, nudging into Audi TT ground.

tires make the single most significant difference in lap times. I was quite a bit faster having the Trofeos on the F430 at Thunderhill and we're talking a couple secs. The F430 understeers on slow turns too but the stickier tires completely took that out of the equation. As for brakes, My brakes were always glowing with stock pads and fluids on any BMW include my old E46 M3 and the E60 m5 on the track. Pads, fluids and steel braided brakes lines solved a lot of that. I typically go through tires in about 3-4 track days and it's the price you pay for having fun..

as for power upgrades I will stick with the proven method on all N54's... JB4 with meth injection and DCI.

Originally Posted by Wavesofblue

First off...man...you have a nice collection! Anyhow, I agree the RFTs are the single biggest problem with a car already balanced towards understeer. But looking at your tire choices I think you could save money on tires. I agree with you 100% about the H&R springs. I am not sure why you want to upgrade pads and fluid. The stock braking system seems good to go as is. Have you noticed something I have missed? If so, please tell me. By the way, if I were going with upgrading the braking system I'd also likely use all steel brake lines. I think you can also change the camber of the front tires and tighten up the rear sway bars for low cost.

I dont know if you have thought about engine upgrades. I am considering the Dinan flash to take the car up a notch. But frankly, until I get the understeer out of the car and have a better feeling of the road I dont see any reason adding 50 horses. I like the expression "always adjust the driver before the car" in that respect. Supposedly with the Dinan phase 2 upgrade the car will do 0-60 in under 4 seconds. Now youre gonna need some new brakes!

I've had my 35is for about a month now, and I love it.
But I do wish the car lost a few pounds. I guess there probably were mechanical reasons, but I found the hood and the trunk to be too damn heavy. I took the car up the canyon roads here in LA, and I just wished the car weighed 80-100 lbs lighter. Otherwise, I do agree with most of your reasoning. I think for a roadster, the car has decent sized trunk (which I happen to appreciate), and the luxury/comfort elements are few more reasons why I love getting in the car every morning.

- J

I love this car .My last car was a Z51 C6 vette , yes it was faster the weight was 300 lbs lighter and stuck the road like glue ….BUT I would not go back to a vette after driving this car .I'm just fine with the way the car handles and rides . But Im not on a track or racing either ,not my thing

Originally Posted by OZ4

I love this car .My last car was a Z51 C6 vette , yes it was faster the weight was 300 lbs lighter and stuck the road like glue …...BUT I would not go back to a vette after driving this car .I'm just fine with the way the car handles and rides . But Im not on a track or racing either ,not my thing

My previous car to my 35i was also a Corvette (2007 Coupe with the Z51 Option)

Quality of interior fit and finish, exterior paint and DCT all advantages over the Corvette.

To me the 35i "feels like" it weighs LIGHTER than the Corvette.

Originally Posted by chefrara

I've had my 35is for about a month now, and I love it.
But I do wish the car lost a few pounds. I guess there probably were mechanical reasons, but I found the hood and the trunk to be too damn heavy. I took the car up the canyon roads here in LA, and I just wished the car weighed 80-100 lbs lighter. Otherwise, I do agree with most of your reasoning. I think for a roadster, the car has decent sized trunk (which I happen to appreciate), and the luxury/comfort elements are few more reasons why I love getting in the car every morning.

- J

I suppose you could make it lighter by using plastic body panels like the vette :P

Originally Posted by vivek_v_rane

I suppose you could make it lighter by using plastic body panels like the vette :P

You could and maybe they should if you want a lighter car

Fiberglass:

Positive - weight savings
Negative - structural rigitidy

Originally Posted by BlueZ4AZ

Fiberglass:

Positive - weight savings
Negative - structural rigitidy

Well it's not fiberglass thats old school either way thin sheet metal or plastic is just a facade .

Originally Posted by vivek_v_rane

I suppose you could make it lighter by using plastic body panels like the vette :P

well you know the 335i coupe had plastic fenders/quarter panels right?

Not to keep dwelling on the matter, but I had my car weighed today while waiting to be serviced. The gross weight was north of 4100 lbs !! Egad !

Curb weight was 3641 lbs. Tsk tsk.

I still very much love the car though.

- J


p.s. z4 35is w/ sport package (19" wheels, etc), no navi, but comfort access.

Originally Posted by chefrara

Not to keep dwelling on the matter, but I had my car weighed today while waiting to be serviced. The gross weight was north of 4100 lbs !! Egad !

Curb weight was 3641 lbs. Tsk tsk.

I still very much love the car though.

- J


p.s. z4 35is w/ sport package (19" wheels, etc), no navi, but comfort access.

I think It's a great car, It's just a fun car to drive

Originally Posted by OZ4

Well it's not fiberglass thats old school either way thin sheet metal or plastic is just a facade .

Well....
Jungles are now called Rain Forests
Bumbs are now called The Homeless
Junkies are now called Drug Addicts
Idiots are now The Mentally Challenged

SMC is just another form of Fiberglass, but since the term "SMC" sounds more high tech, GM started using that term.
SMC panels are formed by a high-pressure mold compressing a mix of fiberglass, resin, catalyst and release agent.

I'm still calling it what it is.....Fiberglass.

I like all the 60's terms.

Originally Posted by BlueZ4AZ

Well....
Jungles are now called Rain Forests
Bumbs are now called The Homeless
Junkies are now called Drug Addicts
Idiots are now The Mentally Challenged

SMC is just another form of Fiberglass, but since the term "SMC" sounds more high tech, GM started using that term.

I'm still calling it what it is.....Fiberglass.

I like all the 60's terms.

Originally Posted by BlueZ4AZ

Fiberglass:

Positive - weight savings
Negative - structural rigitidy

Fiberglass isn't used in the structure at all, neither in Corvettes nor in the new BMW's where it's used for fenders.

Carbon fiber is lighter and stronger than just about anything else on the market today. We could make our cars lighter, stronger, safer and more fuel efficient, by a wide margin.

Of course, it's also expensive, and while I'd support a government subsidy for its use (anything to ween us off foreign oil), the steel industry would go bonkers.

So, cb remains a dream .... for now.

Originally Posted by EdCT

Fiberglass isn't used in the structure at all, neither in Corvettes nor in the new BMW's where it's used for fenders.

See Post #18

Originally Posted by BlueZ4AZ

See Post #18

So

Post 18 doesn't address the structural issue at all - it's just you making a funny.

Fiberglass can be used successfully in non-structural roles in car manufacturing. In fact, it is and has been, as was pointed out.

I'm not sure I agree that a fiberglass chassis or tub cannot be made as strong, or stronger than a steel one. It's not necessarily the material itself, but how its engineered into a structure.

Originally Posted by EdCT

So

Post 18 doesn't address the structural issue at all - it's just you making a funny.

Fiberglass can be used successfully in non-structural roles in car manufacturing. In fact, it is and has been, as was pointed out.

I'm not sure I agree that a fiberglass chassis or tub cannot be made as strong, or stronger than a steel one. It's not necessarily the material itself, but how its engineered into a structure.

I am referring to the fiberglass body panels on the Corvette.

If I parked it at any more than a 5% incline/decline or side/side with the Corvette, when I got back to the car, the doors literally would not close 100% flush for a day or so. The panels would shift that much.

Going over potholes, the Corvette just did not seem as solid as the Z4. It almost felt as though the body panels were not adhered to the frame 100%.

Originally Posted by BlueZ4AZ

I am referring to the fiberglass body panels on the Corvette.

If I parked it at any more than a 5% incline/decline or side/side with the Corvette, when I got back to the car, the doors literally would not close 100% flush for a day or so. The panels would shift that much.

Going over potholes, the Corvette just did not seem as solid as the Z4. It almost felt as though the body panels were not adhered to the frame 100%.

That's a function of the structure. The corvette (at least the newest ones) have a space frame made of steel and aluminum - the entire structure of the car is supported by it. The fiberglas body has no structural function, it's purely cosmetic - the panels bolt on.

If you had a late model vette with this level of flimsiness in the structure, I'm truly surprised, almost no modern convertible I know of does this.

Now, when I was a kid in the 70's, if you drove an Alfa, MGB, Triumph etc., those cars were a different story - you could actually see the entire windshield move side to side at pedestrian road speeds - that and you never parked on a curb as the doors wouldn't function properly

Btw, your Z4 will feel more solid than most any convertible on the road because it's engineered to be that way - it's not a matter of steel vs fiberglass, it's the engineering that goes into the structure - you get what you pay for, and a Z4 is much more rigidly built than a Corvette.

Originally Posted by EdCT

That's a function of the structure. The corvette (at least the newest ones) have a space frame made of steel and aluminum - the entire structure of the car is supported by it. The fiberglas body has no structural function, it's purely cosmetic - the panels bolt on.

If you had a late model vette with this level of flimsiness in the structure, I'm truly surprised, almost no modern convertible I know of does this.

Now, when I was a kid in the 70's, if you drove an Alfa, MGB, Triumph etc., those cars were a different story - you could actually see the entire windshield move side to side at pedestrian road speeds - that and you never parked on a curb as the doors wouldn't function properly

Btw, your Z4 will feel more solid than most any convertible on the road because it's engineered to be that way - it's not a matter of steel vs fiberglass, it's the engineering that goes into the structure - you get what you pay for, and a Z4 is much more rigidly built than a Corvette.

Thanks for the clarification.

Back in 2008 - 2009 when I told the Chevy Serrvice Mgr that the doors on my 2007 C6 didin't close flush after I parked on any kind of an angle, his response was, " That's just the nature of the fiberglass panels"