Wandering Z3

[Don N]

Apologies up front if this is not really a new thread:

I recently installed new struts, shocks, control arms and polyurethane (centered) bushings on my 1997 Z3 2.8 - at 80,000 miles. Previously, the car tracked straight and true. Now, the steering is now delightfully tight and the ride has lost all of those "jiggles" from the worn out struts and shocks, BUT...

there is one problem: Although the steering wheel is "level", and on a perfectly flat road, the car goes perfectly straight, if there is any crown in the roadway, the car turns toward the curb very strongly. In the right lane, it goes right. In the left lane, it goes left. Full attention is required to counter steer back to the center of the lane.

All four wheels have been carefully aligned to factory settings.

I'm guessing that the solid poly bushings have so much less compliance than the old bushings that more toe-in is needed than specified by BMW.

Opinions/ anecdotes please...

 

[t-tony]

Are you on new tyres or part worn. If these are the original tyres they will have"worn" to the old suspension.My car was like this when I first got it and I truly wondered if I had bought a bad car or if that was how a Z3 drove. When I fitted a set of new tyres it really transformed the car. I love it now. Hope this helps you Don.
Ps. My car is on 82,000 miles too.2000 2.0 wide body.

 

[GazHyde]

The Z3 is more susceptible to what you describe, commonly referred to as tramlining. I agree with the tyres being a contributory factor in what you are seeing now.

Mine tramlines quiet badly at times, but it doesn't bother me as I've got used to it now.

 

[zedonist]

It's called bump steer, the rear wheels are pushing the front, hence the fronts go where the road wants it to go, you don't notice it on a front wheel drive because the front wheels are pulling the rear and the car goes where you want it to go. Solid bushings take away the forgiveness of the semi solid bush, so although on a nice flat road you will have good handling, on poor roads you will have amplified the bump steer effect.

 

[Aceman]

All of the above, the Z3 so susceptible to tyre condition/make you wouldn't believe.

A new set of fronts will transform your ride.

 

[Don N]

Thanks all. The tyres are new Michelin ps3 with less than 2000 miles. The car was aligned a third time, now with with zero toe. It's much better now but still pulls right all of the time. We are concluding that the alignment machine may not be calibrated correctly. But to set the toe at 0 we had to fool the alignment computer to allow something other than the factory spec. Going back again on Monday. But the ride is transformed as is the shifting with the new redline mtf in the gearbox. New diff fluid too.

 

[Aceman]

It is hard to accept the tyres are at fault especially when they are relatively new but it is not just the wear on the tyre that the Z3 doesn't like they also are very particular to the tread pattern or make/model of tyre. I have seen so many people in exactly the same position as yourself who have resisted changing the tyres and lets face it who would change a brand new set so I don't blame you at all but when eventually changed for a correct match it is a revalation to them. As said you honestly would not believe they could make such a difference but they do, the bushes and setup yes do have a significant importance in eradicating this trait but the single most effect is the tyres.

 

[zedonist]

Before I changed to 18" wheels, I had a block tread on my tyres, It suffered from bump steer / tramlining, the answer for me was the refurbishment of the front suspension components, there are two ball joints per side plus the track rods, he lollipop bush and the upper strut bearing, there was wear and play in all of these. Once changed and re-alignment done there were no issues of bump steer / tramlining on any road surface.

I have now changed to 18" wheels and the tyres have a directional V pattern, these perform very well on all but very poor roads, at which point it does on occasion track the road imperfections. So I would conclude a non directional block pattern is probably best for the car. Another point to bear in mind is the width of the front tyre, a wider tyre at the front will amplify the issues, so it is best to keep to either 215 or 225 width at the front.

To understand the issue you only have to watch F1 and look how they fight the steering on the older poor condition tracks, compared to the new tracks like yas marina, even on stae of the art racing cars you cannot remove bump steer / tramlining

 

[oldcarman]

I will be buying new tires for my 97 with 17" wheels. I've read that this is a particular problem with 17" wheels but no one has ever explained why a 16 or 18" rim would not have the same problems. Anyone have a theory that can clarify this. I've watched the video on improving the size of the anti-roll bars front and back along with the M bushings make the problem manageable. Has anyone gone this route? JIM

 

[Aceman]

I think you will find that 18" do suffer from the same problem if not more so as the tyres have a lower profile hence a stiffer sidewall which does not have as much compliance as 17" wheels. Conversely the 16" wheels do not suffer as much as they have higher profiles hence more give in the sidewall so will not exhibit quite as much of this foible but still will to a certain extent.

 

[Don N]

An update: There is clearly a bit of a wear-in period with so many new parts: tie rods, strut mounts, shock mounts, all of those bushings, etc. I kept driving, and after about 50 miles, I began to notice that on a nice flat, smooth freeway, the car goes laser straight, hands off the wheel. If there is much crown, I have to correct "uphill". This is a bit more necessary now than before with the worn parts, but with zero play in the steering/suspension, I can understand why it happens. The poly control arm bushings must be causing the added sensitivity. I've decided that all is right - and much improved.

Off to the local National Capitol Area BMW Club spring Pie Run on Saturday up through western Maryland and Pennsylvania - to see how it all works.

Thanks for all of the opinions!

 

[t-tony]

An update: There is clearly a bit of a wear-in period with so many new parts: tie rods, strut mounts, shock mounts, all of those bushings, etc. I kept driving, and after about 50 miles, I began to notice that on a nice flat, smooth freeway, the car goes laser straight, hands off the wheel. If there is much crown, I have to correct "uphill". This is a bit more necessary now than before with the worn parts, but with zero play in the steering/suspension, I can understand why it happens. The poly control arm bushings must be causing the added sensitivity. I've decided that all is right - and much improved.

Off to the local National Capitol Area BMW Club spring Pie Run on Saturday up through western Maryland and Pennsylvania - to see how it all works.

Thanks for all of the opinions!

Hope you enjoy your run out with the beemers. To be honest I took a while to realise that my car was much better than before it just took a while to get used to. Enjoy! !

 

[Cooper]

On Wednesday I picked up my Z3 in Melbourne and drove all over the city running errands before jumping on the ship [just arrived in time] and arriving in Tasmania. I then drove home and did a total of over 500 kilometers before I even had a chance to eat properly. The whole time the car suffered very badly from bump steer and it was like riding on a horse only half broken in, I really had to pay attention and be careful. Well today I finally had the time to fill up and check the tire pressure - they were all only 21 PSI, and this is on tires that are 255/50/R16 I think. Well, after inflating them to 34 PSI she drives like a dream. Sure, there is a little bit of bump steering compared to my Suzuki Grand Vitara but jeez, what a difference it makes with proper tire pressures. I actually thought that I was going to have to replace the bushes underneath.

So now the priorities are: water proof the hood and re-adjust the headlights [tomorrow], replace and lubricate the power window sliders for both doors, check why the passenger side door seems to be leaking in the lower part of the door, get and install a wind barrier [I want to make my own with Z3 computer inscribed in clear plastic with LEDs to highlight the Z3]. Then general maintenance and inspections.

 

[GazHyde]

Well today I finally had the time to fill up and check the tire pressure - they were all only 21 PSI, and this is on tires that are 255/50/R16 I think. Well, after inflating them to 34 PSI she drives like a dream.

Yup, that would do it

 

[Don N]

On Wednesday I picked up my Z3 in Melbourne and drove all over the city running errands before jumping on the ship [just arrived in time] and arriving in Tasmania. I then drove home and did a total of over 500 kilometers before I even had a chance to eat properly. The whole time the car suffered very badly from bump steer and it was like riding on a horse only half broken in, I really had to pay attention and be careful. Well today I finally had the time to fill up and check the tire pressure - they were all only 21 PSI, and this is on tires that are 255/50/R16 I think. Well, after inflating them to 34 PSI she drives like a dream. Sure, there is a little bit of bump steering compared to my Suzuki Grand Vitara but jeez, what a difference it makes with proper tire pressures. I actually thought that I was going to have to replace the bushes underneath.

So now the priorities are: water proof the hood and re-adjust the headlights [tomorrow], replace and lubricate the power window sliders for both doors, check why the passenger side door seems to be leaking in the lower part of the door, get and install a wind barrier [I want to make my own with Z3 computer inscribed in clear plastic with LEDs to highlight the Z3]. Then general maintenance and inspections.

Thanks Cooper! Based on your comment, I did check the tyre pressure and found 34#. I drove it again this morning for the first time since the weekend - all is right with the world. But your description of the your next projects mirrors my own - window regulator maintenance. I understand that the window motors are mounted on a rather flimsy piece of sheet metal that flexes (to failure) if the windows do not run smoothly. Now to figure out what to do about it.

On a technical note, as I understand it, bumpsteer occurs when the rear wheels rebound causing unweighting of the rear axle with associated increased oversteer. Tramlining is a description of steering wheel pull as if the front wheels were caught in a street car track (tram). We have both in our Z's, but tramlining is the problem I've been writing about.

 

[t-tony]

Hi Don, the first thing I would do with the window guides is. Lubricate them with silicone spray. It will make a terrific difference to them. Also the sliding guides inside the doors do benefit from some spray grease too ( normal grease that is not silicone )
Re. The tram lining general con census is it's mainly a tyre issue. On my car it definitely was., new tyres= different car.

 

[Cooper]

Thanks for the definitions Don they are helpful. I still have some bump steer issues and will get the bushes inspected soon.

I have some good news for you regarding the windows, have a look here http://www.zroadster.net/forum/viewtopic.php?f=18&t=11888 this is a step by step instruction on everything you need to fix the windows but read all posts before you try as others have made some contributory comments.

Have a look at this site regarding window deflectors, I WANT ONE NOW - order one for me will ya ? http://www.windblox.com/styles/bmw_z3_windblocker.htm

Cooper

 

[Don N]

Thanks for the definitions Don they are helpful. I still have some bump steer issues and will get the bushes inspected soon.

I have some good news for you regarding the windows, have a look here http://www.zroadster.net/forum/viewtopic.php?f=18&t=11888 this is a step by step instruction on everything you need to fix the windows but read all posts before you try as others have made some contributory comments.

Have a look at this site regarding window deflectors, I WANT ONE NOW - order one for me will ya ? http://www.windblox.com/styles/bmw_z3_windblocker.htm

Cooper

Thanks! One day I'll decide to get in there but I'll look for some of those fasteners before I break in. Meanwhile some silicone spray won't hurt on the visible parts. My windows work ok, but surely need some TLC.

Highly recommended to replace the control arms, sway bar links and brackets, and control arm bushings. There is a new solid feel to my car. However, once you start replacing bushings, you'll be amazed at the quantity of them throughout. Interestingly, I bought a new diff mount bushing, but was persuaded that it is a LOT of trouble to install - you have to remove the diff cover and/or drop the diff. Then I read that creating a stiffer diff mount only transfers forces to the subframe more directly. This is not good - as the z3 subframe and structure it mounts on is notoriously weak. I already see the slightest bit of rust at one of the rivets on my boot floor. This is purely a case of not fixing something before it's broken. So, I'll wait a while, then do a major subframe removal, with new subframe and diff mount bushings, as well as welding in some more material across the riveted/welded boot floor. There are a lot of very scary looking videos on this project.

I acquired this car in November '13. I am the third owner. I sure have learned a lot about it in the past few months.

Tell us more about your "new" Z - some pictures? Issues?

 

[Cooper]

Don, can you please let me know ho much you paid for some of the parts? Where did you get the stuff from? I am in Australia so may have to order a lot of stuff from overseas anyway - the prices are usually better and because I am not doing break down maintenance I have the time. Can we get the bushes etc as full kits?

I will send some pix soon and some more information, time for bed now as 0100 !!!!

 

[zedonist]

You can buy the diff back plate with the bush already installed for just a few more pounds than the bush on its own