Odd handling at speed

M

mct

Member
 Bedfordshire
Hi,
I’ve just got myself a Z4 e86. Very pleased with it apart from the fact that it wanders significantly above 60 mph. Now I’ve just noticed that it has non rft’s on the rear axle and rft’s on the front. Could that be the issue ? Is any one else running a similar combo without any issues ?
It has new shocks, new track rods and suspension bushes and the tracking is good.
Any thoughts ?
Thanks,
Mark
 
And ending point. Get those run flats off immediately.

Currently your front axle is sniffing out all minor surface imperfections and following them, while the rears are just staying their course.
 
Agree get rid of the ditchfinders on the front see if that improves things.
 
I've got RFTs on the front and non-RFTs on the back and it drives brilliantly. Straight as an arrow well into license losing territory. The ride is also no worse than with non-RFTs. They're Merc spec Bridgestones FWIW - Chinese random name stuff is a lot stiffer and crashier.

However, it won't be tyres, and if they've done the front lollipop bushes then it's probably the RTABs at the back. They tend to get forgotten about and they make it feel as though the front is wandering about.
 
Thanks for the suggestions. They are Bridgestone rft’s on the front (fairly new) and Uniroyale rainsport 5’s on the back (new). I’ll get them to check everything front and back first then think about changing the tyres.
 
Those of you with non rft’s - are you carrying a repair kit etc or relying on rac/aa etc in the event of a puncture?
 
mct said:
Those of you with non rft’s - are you carrying a repair kit etc or relying on rac/aa etc in the event of a puncture?
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When I had my 3.0Si I had a space-saver that I bought from another forum member who had sold his Z4. E46 3 Series have them, but it needs to be a 17" one from a 330i or 330d to fit over the front brakes on a 3.0Si. Other models only had a 16" one. An E46 jack also fits the jacking points perfectly.

Spacesaver2.JPG

M's don't have run-flats, just a "Mobility Kit" which is a can of gloop and a compressor. As I often do trips hundreds of miles from home I've bought a full size front wheel for mine which takes up a lot of boot space but would mean I wouldn't be trying to find a tyre in the Scottish Highlands and could continue my trip without any 50mph or mileage limitations.

I still have the Mobility Kit and RAC Membership as Plan B and Plan C though. :LOL:

Some people have used "Rats-tail" plugs and a compressor too, but I'm not confident about my abilities with those.
 
Ok, so the garage have checked tyres, wheels, suspension etc and all seems ok. Having driven it they think it feels like the power steering is pulling the car from side to side a bit like lane assist on modern cars. It only seems to happen on straight roads at speed. Country lanes are fine. Has anyone experienced anything like this ?
 
If your back tyres are new, get 2 more of them for the front so they're all the same make and model. I think that will fix it. You'll be able to sell the old tyres if they're in good condition, I've done that on gumtree a few times locally.

For this type of car especially, I personally would only ever have all 4 tyres exactly the same model of tyre.
 
mct said:
Ok, so the garage have checked tyres, wheels, suspension etc and all seems ok. Having driven it they think it feels like the power steering is pulling the car from side to side a bit like lane assist on modern cars. It only seems to happen on straight roads at speed. Country lanes are fine. Has anyone experienced anything like this ?
Click to expand...
Been said before but could it be sticky steering again, mine had this. it's sorted but still has a sort of pulling different ways as you describe, I think it's a lot to do with the road surface on B roads, it is less obvious on dual carriage ways and M ways.
 
Are the straight roads dual carriageways, or see a lot of heavy goods vehicles? My guess is the very stiff sidewall front tyres are tramlining in lorry grooves, but the soft sidewalls rears are being affected less.

If the fronts are relatively new you should be able to sell them to help fund replacements - might as well go uniroyals to match the rears.
 
You lot have an absolute idéfix with tyres. The Z4 was designed with 18s in mind and far worse run-flats than we have now. It's not like 25 years ago with people throwing 18s on cars that came on 15s and having it dive around the place on motorways.
 
So why doesn't my car with the same tyre setup not buck me off the much abused M4 & M5? I can tell when there's an egregious rut but it runs nicely otherwise.

It sounds like they've looked at the front but not the back. The RTABs are impossible to see in situ and can be really very worn but still never fail an MOT. Doing mine certainly stopped vagueness in the front end.
 
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