Wheel Wobble/Vague Steering - Possible Solution

[Sprite]

I'm not sure if this is the best location to post this, so feel free to move it to a better home. Hopefully it will help someone.

My car suffered from the seemingly common, vague steering at speeds, so much so that I had very little confidence in driving the zed like it was designed to be. I tried everything - new tyres, four wheel alignment, polly bushes, new wishbones... each improved the problem slightly, but it was still there and still made the car horrible to drive.

It might not be the same for everyone, but I found the problem to be a small, but significant build up of crud between the mating faces of the hub and the wheel. Caused I believe by a combination of old copper grease and an electrochemical reaction between the alloy wheel and the ferrous disk/hub. Reading some of the posts, it seems that the problem tends to occur more frequently after tyre changes. This makes sense as the wheels are unlikely to be refitted in the exact same position as they were removed i.e. rotated by at least one if not a couple of bolt holes on the hub. Even a 0.1mm build up of debris at the hub will make quite a difference in the wheel angle at the rim and even more at the tyre.

My solution was to remove each of the wheels and painstakingly clean the mating faces of both the hub and the wheel with a gasket scraper and then some solvent (I used brake cleaner, but I'm sure others will work as well) with wire wool. I'll not lie, it took ages and wasn't a fun job, but it totally cured the problem and now I actually feel like the steering provides feedback rather than feeling like its possessed by a drunk jellyfish.

The hub/disk side isn't too bad to do as you can be quite brutal with this side, however you need to be careful with the wheel side as the soft alloy damages easily. I reassembled with a very thin smear of copper grease and I now make sure this is cleaned off and replaced with fresh every time the wheels are removed. For me this is at least twice a year when I switch from the summer to winter wheels, but if you weren't removing the wheels, I see no reason why it would need to be done.

I can't be sure that this will cure any specific issues as there are many factors which will influence the handling, but if you have tried everything else, this if definitely worth a try.

Cheers,

Dave

 

[z4all]

Got pictures of where exactly needs cleaning mate? For the mechanical novices like me

 

[Chris_D]

Another interesting and this time in particular, a more intriguing post.
It's curious that you got to the stage where making a somewhat 'marginal' change in the mechanical relationship between hub and wheel can make such a significant improvement!
Don't get me wrong, I can totally appreciate the differences which can be effected in any mechanical system, even a thermal fluctuation or change can throw out the operational tolerances of a alpha/gamma seal in a nuclear environment and having experience in that sector has given me a total appreciation for the difficulty of getting things designed there!
But there are so many factors involved in your case; the debris between hub and wheel. The manufacturing tolerance deviation of said hub and wheel x4. Actually x16 when considered cumulative and 4 to the power of n when everyrhing else is taken into consideration! Tyre pressures, condition, wear patterns. Suspension, tracking, geometry. Weight distribution. Wheel balancing. Road conditions. Temperature. All either 10th, 100th or possibly even 1000th mm/gramme/c tolerance. And all inter-related causing an incalculable cumulative effect!
It's great that youve solved the problem and spent time and effort in the process and id hope that it's a happy coincidence but i really wonder if u really solved the underlying problem.
Be interested to hear any ongoing results as my own shaky twitchy steering was solved by the simple application of using taller profile winter tyres on 16" wheels! Its literally perf ct steering and fantastic feedback now. Bizarre.

 

[Sprite]

The post title may be a bit misleading - I don't mean to imply that it's a quick solution to the problem, in fact, I think there are essentials like the alignment that need to be sorted before its even worth trying this. It's more that after trying everything else, I did see a noticeable improvement, but the whole story was something like this:

- Bought Z4, already fitted with non runflats. Steering felt a bit vague and tramlined a bit but not too bad, so after checking the tyre pressures I got the alignment done to try and improve it.
- Slightly better, but only marginal improvement. Did a bit of reading only to find that a lot of other people have said the same thing, turns out that its a "feature" of the electric power steering. I had no frame of reference for what it should feel like, so I accepted it but made a mental note that I probably won't keep the car that long.
- Started to really enjoy the car in spite of the steering (last car was giving me about 18mpg so you can put up with a lot for half the running costs!), so bought second hand set of wheels to use with winter tyres, however since they already have a nearly new set of Bridgestone runflats fitted, I decided to use these for a few months just to see if they are as bad as some people had said.
- With the runflats it was truly awful, not only did it feel vague but it tended to pull randomly at the slightest change in the road camber. I've had other cars with much wider wheels which tramline like crazy but were still more predictable than this was so decided to spend some money on sorting it.
- Replaced the bushes and had the alignment done again, which took out much of the vagueness but it still felt like it pulled a lot on the steering (I could now just feel it better!).
- Replaced the lower arms and had the alignment done yet again, which reduced the amount it was pulling, but it was still quite bad.
- Replaced the tyres, as I had given up on the runflats and winter was now approaching so wanted the winter tyres on these rims. This gave a marked improvement and by now the car was driving better than it had done when I bought it, most of the vagueness had been removed, but it still felt like it was pulling very slightly. To be fair, for most day to day driving it wasn't an issue but when really pushing on in it, you could never really tell if the tyres were starting to struggle for grip or if it was just the steering doing its thing.
- Cleaned up the wheels and hubs as described above. This really did take out the rest of the pulling from the steering. There is still that slight vagueness there but its at such a low level that I can live with it.

So I totally agree that its just one of many factors in a complex system. Wear in any of the components, including the tyres themselves could probably cause the same symptoms and if you are lucky, resolve them when the item is replaced. This is just something that most people can probably have a go at as a cheap DIY fix and hopefully see a bit of an improvement.

I'd love to know why the Zed's are so sensitive to this, as I've had plenty of other cars which don't suffer in anything like the same way. Since the above work, I've also replaced pretty much the rest of the front suspension with new track rod ends, shocks, springs and top mounts, but each one of these hasn't made any noticeable improvement.... I think I'm just being picky now!

 

[Sprite]

Got pictures of where exactly needs cleaning mate? For the mechanical novices like me

It's the area I've circled in red on this pic, and also the part of the wheel that mounts to it (I don't have any wheel pics handy I'm afraid):



It is clean underneath all that copper grease, honest!

 

[dhobbs]

I could understand that grease causing a steering wobble between those mating halfs. Some places recommend not putting copper grease on the hubs for that reason although it can be a pain getting the wheels off.
Always good when you finally fix something