What am I experiencing?

[masCh]

How can you tell if what you experience is really bump steer?I think I start experiencing this after I changed from stock 15 inches to17 inches. Now I feel like my steering wants to turn left or rightwhenever it wants to, or maybe its been happening before but I haventnoticed it.It is quite apparent when I drive on the highway. The steering givesfeedback that it wants to turn to the right, but if I let the steeringgo, it will spin just a little towards the right then goes left againslightly, then right again slightly. It makes me feel uncomfortable. Andif run on the highway where one side of the road is slightly higher thanthe other (those stretches where one side has been recently re-tarred) Iexperience a sharp feedback towards the side of the road that's lowerthan the other. The feedback is not enough to threaten the direction thecar is going, but enough to make me feel I need to grip on the steeringjust in case it does suddenly change direction abruptly.I've done the alignment 3 times in 1 week some 3 months ago when Ichanged the rims, and they all said its normal. I dont think its normalbut I dont have another bimmer to test and compare to.Is this what you call bump steer? If not, what is it?

 

[Lee36328]

It's normal, live with it, or switch back to 15.

It would be compounded by negative camber (check if yours is negative, and by how much), or toe-in (is yours toe-in?)

You can reduce it somewhat by adjusting the above two elements. I am happy with a slight negative camber and a touch of toe-in because it gives me sharper response and helps dial out the understeer a bit.

Cheers.

 

[535i]

Other things related to it ;

1) Type of tires - thread patern esp if it is 'V' shape
2) Tire pressure

Basically, ur car will follow the road contour ..
Like what Lee said - live with it ..

 

[Bavaria]

hey,

im suffering that.especially on bad roads,the pull to here n there is aggravated. nothin much can be done i suppose.

 

[Zoggee]

burn the tyres.... :blush:

 

[skar19]

Please post in the correct place next time

-The Moderator

 

[masCh]

So this isnt what they call bump-steer? Because if its bump-steer, there ARE solutions out there. What do you call this phenomenon?

 

[manjit]

yupp...i am facing this problem as well...but to the account that the problem was not there when i acquired my car in 04'. I am driving in 17" rims ever since. For sure something is wearing out, or else the problem wud be there ever since. I have done alignment few times but no to avail result. All the bushing, ball joints are ok. Last resort, tukar absorber.

Problem scenario:

Even road- superb nice cruising

Uneven road- bad steer...had to hold with 2 hands as steering goes left & right....notice able.


I am pretty sure others experienced this. hoping the thread wud continue until a resolution is found(boleh jimat duit, tak payah tukar absorber)

 

[Lee36328]

Here's a good definition:-

Bump Steer:
A directional change in steering caused by road surface irregularities. As the suspension moves through jounce and rebound, changes in alignment at the front or rear wheels may alter the vehicle's path.

A comment on the impact of larger rims.

[color= blue]
Q: What wheels / tires should I get? I want to move up in size.

A: Larger wheels and ultra-low profile tires look cool, but as with lowering, there will be side effects as well. Large diameter wheels have a lot of mass at the rim, which wastes engine muscle to get rotating. Also, a large wheel/tire combo often ends up taller than stock in total height, which changes the final drive ratio of the car. This leads to slower acceleration, as well as speedometer error. Lastly, big rims with low-profile tires tend to wander, rather than track straight, as they are influenced by waves and bumps in the road surface[/color]

So, whether this is bump steer or not depends on how one interprets the definition. The fact remains, the larger the rims, and therefore the lower the tire sidewall, the more the tendency of the tire to follow the surface of the road because there is less sidewall to compress to absorb the irregularities.

The solution to this? Smaller rims -> taller sidewalls.

 

[3er]

Im running on 225/40/18 and yes, i suffer tramlining as well. You just have to get used to it or go down to 17" or 16".

 

[Daniel]

Originally posted by masCh@Jan 8 2006, 10:24 PM
So this isnt what they call bump-steer? Because if its bump-steer, there ARE solutions out there. What do you call this phenomenon?

its called tram-lining.