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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > Z Series > E85 / E86 Z4 (2003-2008)

E85 / E86 Z4 (2003-2008)
E85 Z4 Roadster, E86 Z4 Coupe, E85 Z4 M Roadster, and E86 Z4 M Coupe talk with our BMW gurus here.

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  #1  
Old 06-21-2013, 12:24 PM
Tony Amos Tony Amos is offline
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Mein Auto: BMW Z4 2.5 SI Sport 2007
Z4 wheel sizes

Have just bought 2007 Z4 2.5 SI Sport, only done 20,000 miles. Ride seems harsh, particularly if hit a pothole, and think the 18" wheels with run flat tyres could be to blame. Thinking of replacing tyres with non run flat, and possibly fitting 17" wheels with larger profile tyres. Car is used as a really good looking convertible as against speed machine (although I do love the BMW 6 cylinder engine). Any advice greatly appreciated.

Last edited by Tony Amos; 06-21-2013 at 12:27 PM.
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  #2  
Old 06-21-2013, 01:56 PM
keeton keeton is offline
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The sport package included a slightly lowered and stiffer suspension so tires would not fix that. Having said that, you could try non-run-flat 225/45/17 wheels/tires which was the stock size without the sport package and I think the ride would be much improved.
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  #3  
Old 06-21-2013, 05:28 PM
pokeybritches pokeybritches is offline
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2.5i's do not come with 18" wheels. If your car does have 18's, they were put on by a previous owner. You can check the tire sizes to confirm your wheel size, or post a picture of them on here.

17" wheels and non-RFT's will help, but the car will never have a plush ride.
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  #4  
Old 06-22-2013, 03:25 AM
Tony Amos Tony Amos is offline
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Mein Auto: BMW Z4 2.5 SI Sport 2007
Z4 wheel sizes

Thanks for the replies. Must point out that 18" wheels are the standard on 2.5 SI Sport, certainly in the Uk. Not looking for a plush ride, realise that the Z4 is a sports car, but would like to reduce the "jarring and banging" when you hit one of our plentiful potholes.
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  #5  
Old 06-22-2013, 07:42 AM
Jstic Jstic is offline
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Mein Auto: 2006 Z4 3.0i
18" wheels, RF or not have almost no sidewall to absorb road faults. It almost looks like you are riding on the rim. 17" have more and ride better. I know because I have tried both. For the best ride, 17" non RFT tires and a quick fix tire kit in the trunk.
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  #6  
Old 06-22-2013, 01:32 PM
Tony Amos Tony Amos is offline
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Mein Auto: BMW Z4 2.5 SI Sport 2007
Z4 wheels

General opinion seems to be that run flat tyres spoil the ride. If I fitted non run flat tyres, would a space saver spare wheel be an option for emergencies? On E Bay there are plenty of BMW 17" E46 space saver spares at low prices, does anybody know if these could be used on a Z4?
Took the car for first good run today. Must say it handles superbly through twisty lanes and acceleration is mind blowing for old git like me (and that is without using Sport button). Also feeling of quality compared to 2009 MG TF it replaces is very noticeable. Loving it!
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  #7  
Old 06-22-2013, 02:18 PM
chickdr chickdr is offline
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I think that would be a cool car with the 2.5 si motor. In the states we got a detuned 3.0i motor instead. You had to get the 3.0 si to get the wheels you are talking about. I would certainly recommend getting non run flat tires as pretty much anyone who has was glad they did. As for a spare- the M doesn't use run flats and has no spare. Just carry BMW's mobility system.
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  #8  
Old 06-22-2013, 04:07 PM
ZEEBOY ZEEBOY is offline
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Mein Auto: 2001 Z3 Coupe and 2003 Z4
Last fall, I purchased a tire/wheel set of winter Blizzaks for our 2003 2.5 Z4....the tires I purchased were up one size on aspect ratio (taller tire) from our normal tires. It is remarkable the improvement in the ride of the car with this one change...in fact, my wife, who drives the car, now insists that I put the same taller aspect ratio tire on the spring/summer/ fall wheels.
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  #9  
Old 06-23-2013, 07:47 AM
STIHLBOLTS STIHLBOLTS is offline
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You can also find a soft tire, Conti's are stiffer than most, I tried some Kumho's on my 1st 2004 Z4 after taking the run flats off and it was night and day difference. But you still won't be in a sedan type ride. With my M I went with 2 size up on the tires still on 18 rims. After these wear down I am going back down a size. The ride is good, but the handling is a little mushy.

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  #10  
Old 06-26-2013, 08:52 AM
Tony Amos Tony Amos is offline
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Mein Auto: BMW Z4 2.5 SI Sport 2007
Z4 wheel sizes

Thanks to everyone for the good advice. I have decided to change to non run flat tyres, same profile on same 18" wheels, and to carry 17" space saver or emergency repair kit. Have to admit that I was overstating the problem - the more I drive car with hood down, the less I notice the harsh ride. Just got back from 100 mile drive to Whitstable and along coast in lovely sunshine - it's true, we do get some sun in England.
Thanks again for the replies.
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  #11  
Old 07-04-2013, 07:28 AM
tohbi tohbi is offline
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the stock 16" wheels with square setup will give the softest ride and longest wear, due to being able to rotate the tires.
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  #12  
Old 07-05-2013, 09:42 AM
Pierce Pierce is offline
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Z4 wheel sizes

Get rid of those run flats!!! That IS your problem right there!! I just did that to my 3.0Si last month and it made a world of difference! You don't need to change the wheel size. Just change the tires and it will drive more like a car. No jarring bumps and no wrestling with the car while it tramlines all over the place


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  #13  
Old 07-05-2013, 11:30 AM
dominoaz dominoaz is offline
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+1 - Tires Are Culprit

Dump the RF's. After 5 years of tooth shattering ride on my 2007 Z4 3.0si, I finally decided to get rid of the RF's, even though they were only 50% worn. I went from the factory Sport Pkg. 18 inch RF's to 19inch non-RF's. The change in ride is astounding. Even with a lower profile non-RF, I am getting a far better ride. New tires are Sumitomo STR Z3's, high performance, summer tires. Quiet, sticky, smooth riding. As for spare needs, I carry a tire plug kit, a can of Green Slime flat fix and a small compressor.
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  #14  
Old 07-14-2013, 11:24 PM
Hox Hox is offline
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Please tell me you didn't get 5 years out of the same set of tires....
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  #15  
Old 07-15-2013, 02:00 AM
dominoaz dominoaz is offline
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Five Years & Plenty of Tread Remaining

The Z is not my daily driver. At present, 15,000 miles on car. The RF's had better than 60% tread remaining. Given the wear rate, it would have taken another five years to wear the RF's out. So, I caved and dumped them. Sorry I didn't do it five years ago.
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  #16  
Old 07-15-2013, 08:39 AM
STIHLBOLTS STIHLBOLTS is offline
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Wear on the tire is not the only reason you change tires. Age is a serious consideration too. If you had those on the car 5 years, then I would be willing to suggest your tires were at least 7-8 years old since most stock tires are usually a couple of years old when they get mounted.

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  #17  
Old 07-15-2013, 10:22 AM
dominoaz dominoaz is offline
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Tire Age Mythological?

IMO, the tire age issue is myth created by tire manufacturers and dealers to sell tires. What is more critical is the exposure the tire has had during its life. Notwithstanding heavy duty usage, such as semi tractor, or manufactoring defects, given the millions upon millions of owner-neglected tires on the road, the incidence of tire disintegration is miniscule. Driving on five year old tires isn't exactly "rolling the dice."
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  #18  
Old 07-15-2013, 11:44 AM
tohbi tohbi is offline
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ha! i'm lucky to get 6 months on the rear tires.

out here, tire rot is a problem. the sun destroys everything.
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  #19  
Old 07-15-2013, 02:33 PM
dominoaz dominoaz is offline
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+1 Tohbi

As you can see, I live in AZ also. Everything turns to dust in the desert. I am fortunate to have a garage at home and underground parking at work. So my Z4 gets very little sun exposure.
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  #20  
Old 07-15-2013, 03:22 PM
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Keepittrill Keepittrill is offline
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Z4 wheel sizes

Quote:
Originally Posted by dominoaz View Post
As you can see, I live in AZ also. Everything turns to dust in the desert. I am fortunate to have a garage at home and underground parking at work. So my Z4 gets very little sun exposure.
AZ sucks.


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  #21  
Old 07-15-2013, 03:43 PM
tohbi tohbi is offline
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Quote:
Originally Posted by Keepittrill View Post
AZ sucks.


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phoenix isn't arizona. it's east los angeles, at least, to those of us whose families have been here awhile.
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  #22  
Old 07-15-2013, 04:10 PM
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Keepittrill Keepittrill is offline
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Z4 wheel sizes

Quote:
Originally Posted by tohbi View Post
phoenix isn't arizona. it's east los angeles, at least, to those of us whose families have been here awhile.
My parents have been here for 25 years and I've been here for 18 years.


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  #23  
Old 07-19-2013, 02:11 PM
ytramiii ytramiii is offline
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I moved to Phoenix so I could DRIVE my BMW's and my Z4....most other states are abusive on the car with road rash, salt, potholes, busted up chunks of concrete, etc. I SAVE tons of money running my BMW's in Arizona. And Phoenix is NOT LA.....not even close.
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  #24  
Old 07-19-2013, 02:24 PM
tohbi tohbi is offline
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i miss the "twisties." arizona is more high-speed straightaways, good for cars like corvettes, if you can afford the tickets.

i was being facetious. phoenix may be what arizona is becoming but not what it was. cities are their own reality and often not like the rest of the state.
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  #25  
Old 07-19-2013, 03:13 PM
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Keepittrill Keepittrill is offline
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Z4 wheel sizes

Yeah, there really aren't any twisty roads in AZ...kinda sucks


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