Uneven Rear Tyre Wear???

Mr Whippy said:
I think 0.5 deg off the rear camber might help.

Of course my experience tinkering with it is in a vehicle simulator with many unknowns, but it does seem an odd amount to run on a road car on road tyres.

Another thing is, I think Evo are a little wrong pointing the finger at the toe imho, plenty of cars run that kind of kinematic to toe out the loaded rear, and don't drive like that.
What I have noticed while watching the kinematics of the E46 Z axle (guess it's pretty close to the Z4 one anyway), is the dynamic camber change under bump... it's got quite a lot of movement. Now, throw in bumps that happen to one wheel and not the other (bumpy roads), and you get camber thrusting as the wheel goes into even more negative camber and fires the back end around laterally.

I'm not sure why the Z4 suffers more from that though, than an E46 might... maybe static camber settings are lower to start with, ie, nearer -1.5 rather than -2.5 or so!?


Personally, I think the Z4 doesn't have any nasty tramlining issue, what people experience is lateral thrusting and imho, most of it is from the back end... (I noted this on my first test drive report of a Z4 on here actually, very much the back end shifting around and making the car not so fun to drive on bumpy roads)

Dave
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I think you're right - it certainly isn't tramlining IMO, but whatever it is gives an effect that many people assume is tramlining.

It's really down to the characteristics of the Z4 suspension (the rear particularly) and the way things move when a bump is experienced. I'm not knowledgeable enough to make comment on evo's ideas, but it certainly sounds like a possibility. For me, it's the least enjoyable part of the car as there's some roads up north from me where I back off due to the bumps: I was out in my mate's MINI Cooper at the weekend and was surprised how composed it was on bumpy roads compared to mine :(

The (Bridgestone - for those Michelin RFT lovers :wink:) RFTs ruin the Z4.
 
The thing that confused me with the Evo article, that then makes you question their authority/understanding of it, was they said the wheels toe in under compression. The loaded wheel would be on the outside of the turn, and toeing in would be steering that wheel into the direction of travel, so reducing the scrub angle and reducing the lateral force it generated.
What you would want to aid track driving would be toe out, and I'm pretty sure this is what they mean... easy to test with a camera on a tripod filming the wheel with a spirit level across it while jumping up and down in the boot! (I have done it for camber ;) )

I think just taking out some of the camber will reduce the magnitude of the lateral thrusting quite a lot. It'll still bump camber as much, but since you are starting with less you will end up with less too even on the bigger bumps vs before :)


My only concern would be reduced rear end grip, but I guess you'd just have to try and see what the changes were like :D

Dave
 
I wondering if the difference between the Z4 and the 3 series might be due to the Z's lower center of gravity and the fact that we're practically sitting over the rear axle? Is the wheelbase length the same?

Either way, I like the way my car rides-lots of feedback. Don't expect a tightly sprung sports car to ride or handle like a family sedan.
 
I would certainly be prepared to possibly lose some rear end grip, on the basis we spend far more time negotiating (increasingly bad British) uneven roads than trying to hang the rear end out on corners...honest :P
Grip is one thing the Z4 seems to have more than enough of, I've not been able to get to the point where it feels like the rear is going to let go, prehaps I'm not driving fast enough, damn :oops: ! However there are stretches of road where it is difficult even to maintain speeds up to the posted limit trying to keep the car off the verge or over the centre line, this more than anything else (for us) detracts from the enjoyment of having a 3 litre Roadster.
Is it possible to adjust the rear camber on a standard car? or does it require the fitment of aftermarket adjustable rear camber arms? I remember seeing them advertised somewhere.

Thanks,

Dave.
 
I thought the rear was adjustable with eccentrics/adjustable rods, but maybe not!?

Personally I don't mind the car being a challenge to drive quickly. RFT Brigestones went too far, but I do prefer it to be lively. Being able to travel fast without effort is the complete opposite of what I want, within reason... that is why I sold my last car... it literally was far far too fast without expending any real effort. A bad thing imho!

Dave
 
I did a lot of drifting at an airfield day (Woodbridge) on Saturday and noticed that the inside of my rear tyres had worn 1mm more worn than the outside. If I get someone to change the camber would this ruin my handling, I would ideally like even wear.

It's a Z4MR
 
Smartbear said:
Hi, it's more likely to be the tracking out of kilter than the camber causing this.
Rob
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I may have to get it checked out although it wasn't done long ago. This thread makes uneven tyre wear sound normal, does anyone else experience it and will doing this make it worse:

https://www.youtube.com/watch?v=8rNkTFlsxnM

Not the best drift I know but I'm getting there with it.
 
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