Wide wheels follow the grooves on the road?

[Boxtyp3]

Try increasing the psi a little bit. The way I understand it is that the wider tires has more contact with the road hence more grip. Probably that's why its following the road grooves. Just an opinion.

[fourtailpipes]

Originally Posted by bogart

Actually... toe-in will make things "feel" worse. The adjustment that would eliminate the issue would be negative camber and neutral or toe-out. I know this because when my car was stock with almost no negative camber and toe-in, it would tramline like crazy. After suspension upgrades I now run -3 degree camber and I had it set at 1/8-1/4" toe-out. Tramline sensation went away completely.

I just recently changed it back to a slight toe-in, I would say about 1/8", and even with the negative camber, I now feel the tramline again. So, some toe-out, alone, may do the trick now that I think about it more.

you have this backwards. toe out improves turn-in and hurts straight line stability. toe in hurts turn-in but improves straight line stability. your results/impressions may have been muddied a bit by the simultaneous camber change, though that should also have the opposite effect from what you described (all things being equal). take a look at this... it's a little elementary, but covers the basics. the grassroots motorsports article linked at the bottom of page 1 is also good.

[bogart]

Originally Posted by fourtailpipes

you have this backwards. toe out improves turn-in and hurts straight line stability. toe in hurts turn-in but improves straight line stability. your results/impressions may have been muddied a bit by the simultaneous camber change, though that should also have the opposite effect from what you described (all things being equal). take a look at this... it's a little elementary, but covers the basics. the grassroots motorsports article linked at the bottom of page 1 is also good.

... I know what toe does. I studied racecar vehicle dynamics (rvd) throughout college. I think you misunderstood my explanation. Basically, toe-in will tramline more than toe-out. I know this from experience with different suspension settings, tires, and suspension parts on my own car.

[fourtailpipes]

Originally Posted by bogart

... I know what toe does. I studied racecar vehicle dynamics (rvd) throughout college. I think you misunderstood my explanation. Basically, toe-in will tramline more than toe-out. I know this from experience with different suspension settings, tires, and suspension parts on my own car.

interesting... and highly unique. can you cite a source you've encountered in your college studies that corroborates this? this directly contradicts the prevailing consensus, including every chassis dynamics source i can come up with.

[3liter1]

[bogart]

I don't expect anyone to necessarily agree with me, I'm just trying to help out with the issue based on my education and experience with my own car through trial and error.

According to the following books:

Chassis Design and Race Car Vehicle Dynamics by William and Douglas Milliken

and based on the design of the 1-series front MacPherson strut suspension I believe the following is taking place to cause a tramlining sensation:

- Tires with stiffer and shorter sidewall heights tend to transmit more load from the road through the sidewall to the wheel, and then ultimately to the steering wheel. I believe that wider tires will actually help combat this issue since there is more contact with the road and would have less of a tendency to follow small imperfections in the road compared to thinner tires. I also believe that switching from RFT to non-RFT would help, due to the change in sidewall stiffness.

- Low caster angle will increase tramlining, because as the wheel turns it creates less negative camber during cornering. The solution to this would be to increase caster angle in the positive direction. This will only create camber when the wheel is turned, which is good for handling as well as keeping tire wear in check. It also allows for better longitudinal grip during braking.

- Negative camber with zero toe or toe-in will increase tramlining due to the scrub radius. Negative camber with toe-out will have little to no affect on tramlining. I will address this later.

- Bushing stiffness will affect tramlining. Forces are transmitted from the road through the tire to the wheel, which is connected to the upright. The upright is supported by the control arms and strut. If the bushings in the control arms that are connected to the chassis are too soft, the upright will move at a different rate compared to the rest of the suspension. The tie-rod also connects to the upright as well as the rack and pinion. As the bushings deform and the upright moves, this will cause a force through the tie-rod that will be felt in the steering wheel. Increasing the bushing stiffness or using solid mounts will decrease tramlining. The problem with solid mounts is that it would cause extreme suspension and chassis wear as well as increase NVH. However, this would be the only way to completely control the suspension geometry. Many racecars use solid mounts for this reason.

- The 1-series front suspension is designed with a positive scrub radius. Spacers, wider wheels, and wider tires will all increase the scrub radius even more in the positive direction. The reason that I believe that toe-out will decrease tramlining is because if the suspension is set at toe-in or zero-toe, the positive scrub radius will rotate the wheel toward the toe-out direction automatically during deceleration, such as letting off the accelerator momentarily, and drastically during braking. Tires in a toe-in setting will constantly be pulling inward, this is why it is so stable. However, the combination of scrub radius and toe-in will cause the tire and wheel to rotate back and forth between toe-out and toe-in and this easily allows the tires to follow different irregularities in the road, but if the setting is already at toe-out then during deceleration the tires and wheels will remain stable at the toe-out condition not causing any extra force through the tie-rod.

For a stock 1-series I would suggest:
- Wider tires.
- Alignment: Front camber -1.5 degress, front toe-out 1/8", caster 7 degrees.

For a 1-series with moddified suspension including M3 control arms and sway, coilovers, camber plates, and adjustable endlinks:
- Wider tires.
- Alignment: Front camber: max approx -3 degrees, front toe-out 1/8", caster 9 degrees.

[fourtailpipes]

Originally Posted by bogart

I don't expect anyone to necessarily agree with me, I'm just trying to help out with the issue based on my education and experience with my own car through trial and error.

According to the following books:

Chassis Design and Race Car Vehicle Dynamics by William and Douglas Milliken

and based on the design of the 1-series front MacPherson strut suspension I believe the following is taking place to cause a tramlining sensation:

- Tires with stiffer and shorter sidewall heights tend to transmit more load from the road through the sidewall to the wheel, and then ultimately to the steering wheel. I believe that wider tires will actually help combat this issue since there is more contact with the road and would have less of a tendency to follow small imperfections in the road compared to thinner tires. I also believe that switching from RFT to non-RFT would help, due to the change in sidewall stiffness.

- Low caster angle will increase tramlining, because as the wheel turns it creates less negative camber during cornering. The solution to this would be to increase caster angle in the positive direction. This will only create camber when the wheel is turned, which is good for handling as well as keeping tire wear in check. It also allows for better longitudinal grip during braking.

- Negative camber with zero toe or toe-in will increase tramlining due to the scrub radius. Negative camber with toe-out will have little to no affect on tramlining. I will address this later.

- Bushing stiffness will affect tramlining. Forces are transmitted from the road through the tire to the wheel, which is connected to the upright. The upright is supported by the control arms and strut. If the bushings in the control arms that are connected to the chassis are too soft, the upright will move at a different rate compared to the rest of the suspension. The tie-rod also connects to the upright as well as the rack and pinion. As the bushings deform and the upright moves, this will cause a force through the tie-rod that will be felt in the steering wheel. Increasing the bushing stiffness or using solid mounts will decrease tramlining. The problem with solid mounts is that it would cause extreme suspension and chassis wear as well as increase NVH. However, this would be the only way to completely control the suspension geometry. Many racecars use solid mounts for this reason.

- The 1-series front suspension is designed with a positive scrub radius. Spacers, wider wheels, and wider tires will all increase the scrub radius even more in the positive direction. The reason that I believe that toe-out will decrease tramlining is because if the suspension is set at toe-in or zero-toe, the positive scrub radius will rotate the wheel toward the toe-out direction automatically during deceleration, such as letting off the accelerator momentarily, and drastically during braking. Tires in a toe-in setting will constantly be pulling inward, this is why it is so stable. However, the combination of scrub radius and toe-in will cause the tire and wheel to rotate back and forth between toe-out and toe-in and this easily allows the tires to follow different irregularities in the road, but if the setting is already at toe-out then during deceleration the tires and wheels will remain stable at the toe-out condition not causing any extra force through the tie-rod.

For a stock 1-series I would suggest:
- Wider tires.
- Alignment: Front camber -1.5 degress, front toe-out 1/8", caster 7 degrees.

For a 1-series with moddified suspension including M3 control arms and sway, coilovers, camber plates, and adjustable endlinks:
- Wider tires.
- Alignment: Front camber: max approx -3 degrees, front toe-out 1/8", caster 9 degrees.

this is all true in pieces, but your conclusion essentially challenges the alignment philosophy which has been developed by BMW engineers across decades of macpherson-strut-having platforms (fortunately or not) set up to minimize tramlining. i think it's a much safer bet that there's something else amok with his alignment.

it's also worth clarifying that as long as the positive caster angle is greater than the negative camber angle by absolute value (which is always the case in these cars), wheel tilt increases throughout steering rack travel. but that's just an aside.

[RimasRS]

Thanks again guys but now I'm confused a bit toe in or toe out? Would be interesting to study for example E46 cars like 325i and M3 what differences in suspension and alignment setup those cars have???

[bogart]

Originally Posted by fourtailpipes

this is all true in pieces, but your conclusion essentially challenges the alignment philosophy which has been developed by BMW engineers across decades of macpherson-strut-having platforms (fortunately or not) set up to minimize tramlining. i think it's a much safer bet that there's something else amok with his alignment.

it's also worth clarifying that as long as the positive caster angle is greater than the negative camber angle by absolute value (which is always the case in these cars), wheel tilt increases throughout steering rack travel. but that's just an aside.

True... he should get a 4-wheel alignment to make sure nothing was knocked out of whack. Maybe he should just try toe-in and toe-out and see which setup he likes more. It is a 10 minute adjustment in the driveway.

Good clarification on caster angle. Thanks

[fourtailpipes]

Originally Posted by bogart

True... he should get a 4-wheel alignment to make sure nothing was knocked out of whack. Maybe he should just try toe-in and toe-out and see which setup he likes more. It is a 10 minute adjustment in the driveway.

great recommendations. there are plenty of DIY alignment threads out there to follow if he wants to play with toe, but a clean alignment is always needed as a starting point.

[fourtailpipes]

Originally Posted by RimasRS

Thanks again guys but now I'm confused a bit toe in or toe out? Would be interesting to study for example E46 cars like 325i and M3 what differences in suspension and alignment setup those cars have???

start with a fresh alignment to factory specs (which would include a small amount of toe-in). make sure you get a before/after printout. if there is still a tramlining issue, go from there. my guess is this should solve it, or if it doesn't it'll at least be much easier to troubleshoot from there, since we'll have a solid baseline. right now we don't really know what your alignment looks like, so we can only speculate.

[RimasRS]

Originally Posted by fourtailpipes

start with a fresh alignment to factory specs (which would include a small amount of toe-in). make sure you get a before/after printout. if there is still a tramlining issue, go from there. my guess is this should solve it, or if it doesn't it'll at least be much easier to troubleshoot from there, since we'll have a solid baseline. right now we don't really know what your alignment looks like, so we can only speculate.

Well I can tell you it's 100% stock/oem but thanks

[info@VMRWheels]

OP - Definitely sounds like an alignment issue. I'd recommend taking the car in to see if everything is within spec. A bit of toe might help you with the tramlining you are experiencing.

[fourtailpipes]

Originally Posted by RimasRS

Well I can tell you it's 100% stock/oem but thanks

do you have the spec sheet from your alignment?

[RimasRS]

Originally Posted by fourtailpipes

do you have the spec sheet from your alignment?

I had it somewhere will look for it and will try to share it

[bogart]

My car tramlined a lot more with the factory alignment settings when I first bought the car brand new than it does now.