What is 'tram lining'?
- Thread starter toonmal
- Start date
toonmal said:I've been reading a lot about run flats and tramlining. I'm assuming they give the effect of being stuck in a tram line.
However, I can't understand how this could happen on a good quality road.
Could someone enlighten me please
I'm assuming its a matter of the car pulling you in one direction even though your trying to steer in the opposite direction. Only reason I'm assuming this is Iv had a few times on my RF's where Iv been accelerating hard & say Iv driven over a cats eye it seems to drag me in an unpredictable direction which makes me have to steer against it quite harshly to compensate for it. In other words it acts like its stuck in a grove or 'tramline'...But again this is the first time Iv driven a powerful rear wheel drive car so not sure if its more to do with me getting used to the drivetrain.
On many well used roads there are ruts on the bit of the tarmac that most traffic travels - caused by thousands of vehicles driving in the same part of the road. Most of the time you can't see them from the driver's seat, but they are there - try driving in the slow lane of the motorway where the lorries travel. Or any other lane actually, because it is more pronounced at speed. The stiff sidewalls of runflats catch the grooves and cause steering movement, mostly barely perceptible but enough to be unsettling if you are travelling fast. Also happens in a more scary fashion on fast twisty A and B roads when you catch an uneven point or a weird camber as the tyres don't ride the bumps but take the route of least resistance.
You do get used to it after a while, for me it just became a part of driving the car. The bigger reason I went non runflat was to soften the ride... I still get a bit of tram lining even now, but I think that's the peculiar suspension set up of the car, not the tyres.
You do get used to it after a while, for me it just became a part of driving the car. The bigger reason I went non runflat was to soften the ride... I still get a bit of tram lining even now, but I think that's the peculiar suspension set up of the car, not the tyres.
A main dealer will not put non runflats on a car that has runflats as OEM. Not sure any other dealer will either. If you buy on here it will more than likely have non runflats fitted already, but it's not calamitous if it doesn't, just change when you can. They aren't dangerous, just irritating... And some eome actually have no issue with them.
You looking at e89s then ? Doesn't really matter as I think all BMWs except ///Ms come with runflats nowadays, and the e85/86 did too.
It is possible that new BMWs use newer versions of RFTs that are better than the ones on the previous model of Z. Ask a question in the e89 section about what the owners think of them ?
It is possible that new BMWs use newer versions of RFTs that are better than the ones on the previous model of Z. Ask a question in the e89 section about what the owners think of them ?
Low speed tramlining is tolerable - you can at least get used to it. It's the high speed behaviour that freaked me out, e.g. on country lanes. Very skittish - replace the OEM runflats with something decent and the car feels far more planted on bad roads.
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toonmal said:I've been reading a lot about run flats and tramlining. I'm assuming they give the effect of being stuck in a tram line.
However, I can't understand how this could happen on a good quality road.
Could someone enlighten me please
I think you answered your own question. It doesn't happen on a good quality road. It happens on poor quality roads or roads with pronounced facets such as think painted lines or tarmac laid in certain patterns.
This affects older Z4's, e85/e86 for the most part. I've never had tram-lining effects in my e89 (new/latest Z4 model), I certainly did on my e85. Run Flats on new Z4's are NOT optional.
shotbybothsides
Member
Think of the front wheels, and the fact that they steer by pivoting round an axis that is called the kingpin axis.
So called because 100 years ago, carts had simple steering where the wheel carrier (hub in modern terms) was mounted on a big vertical pin to allow it to be steered left and right.
OK, now draw an imaginary line through the centre of the kingpin to the surface of the road, where the tyre contac patch is.
If there's a line or contour in the road directly below the kingpin line (this is called kingpin axis) it will have no leverage on the steering as the tyre passes over it, so you won't feel it through the steering.
But, beacause you have modern wide tyres, it is possible that the inperfection in the road, is acting on the tyre, several inches to left or right of the kingpin axis, which gives a rotational force around the kingpin axis, that you feel through the steering and the road starts to steer the car.
A further complication (particularly in front wheel drive cars or cars with big brakes), if there simply isn't room inside the wheel for all the suspension joints, brakes, calipers etc and still allow the wheel to steer fully, unless the kingpin axis is moved inboard, and therefore moving the kingpin axis away from the centre of the tyre contact patch. Thus making tramlining etc worse. Tilting the kingpin to "point to the centre of the contact patch" just raises other steering issues.
It's all a compromise, and the stiffer sidewalls of runflats can magnify the problem as well, as we see with Z4's
So called because 100 years ago, carts had simple steering where the wheel carrier (hub in modern terms) was mounted on a big vertical pin to allow it to be steered left and right.
OK, now draw an imaginary line through the centre of the kingpin to the surface of the road, where the tyre contac patch is.
If there's a line or contour in the road directly below the kingpin line (this is called kingpin axis) it will have no leverage on the steering as the tyre passes over it, so you won't feel it through the steering.
But, beacause you have modern wide tyres, it is possible that the inperfection in the road, is acting on the tyre, several inches to left or right of the kingpin axis, which gives a rotational force around the kingpin axis, that you feel through the steering and the road starts to steer the car.
A further complication (particularly in front wheel drive cars or cars with big brakes), if there simply isn't room inside the wheel for all the suspension joints, brakes, calipers etc and still allow the wheel to steer fully, unless the kingpin axis is moved inboard, and therefore moving the kingpin axis away from the centre of the tyre contact patch. Thus making tramlining etc worse. Tilting the kingpin to "point to the centre of the contact patch" just raises other steering issues.
It's all a compromise, and the stiffer sidewalls of runflats can magnify the problem as well, as we see with Z4's
I only recently got my zed on a Saturday and on the Monday the run flats were replaced with normal tyres but in that short time I could understand what everyone says about run flats I also found on country lanes the car was very very skittish and I am so glad I removed them as it really does make a massive difference.
toonmal said:Thanks for all the info folks, totally understand now
Don't worry it doesn't happen on the E89!
I will probably fit runflats when the originals wear out (unless the prices get even more silly)
If you do ever fit non runflats the dealer doesn't want to know the car at trade in time.
ronk said:toonmal said:Thanks for all the info folks, totally understand now
Don't worry it doesn't happen on the E89!
I will probably fit runflats when the originals wear out (unless the prices get even more silly)
If you do ever fit non runflats the dealer doesn't want to know the car at trade in time.
and of course you have to deal with those punctures down lonely country roads.. late at night, during a thunderstorm, in the winter, having left your coat and phone at home.... :evil:
Very interesting about the trade in (even though I haven't bought it yet lol.ronk said:toonmal said:Thanks for all the info folks, totally understand now
Don't worry it doesn't happen on the E89!
I will probably fit runflats when the originals wear out (unless the prices get even more silly)
If you do ever fit non runflats the dealer doesn't want to know the car at trade in time.
And yes Maxsam..sod's law and all that
