Who did your suspension mods?

Being that you have had the suspension all apart, my guess is that something might be loose or installed incorrectly. I would first suspect the front struts and their mounting points.

 

ok this is weired, again theirs tourq steer but very little torq steer, its not totally eliminated but awsome compared to normal ff cars, i had no torq steer with my oem wheels then after changing to lighter wheels that very day i noticed it ware i couldent before

the driver side half shaft is a solid half shaft the passinger side is a segmented half shaft so the passinger side is longer than the driver side by a bit, not shure if that really has a huge affect but man mini is good at marketing hehehhehe

 

found this pretty reasonable discussion of steering and gassing it for a FWD:

http://www.sportcompactcarweb.com/ed..._technobabble/

basically, the driving force comes from the contact patch, which lies behind the steering axis. the result is like trying to change the direction of a caster wheel: it wants to swing around. small changes in toe, alignment, caster, softness, etc will make one side respond differently than the other and basically try to steer the car.

traditionally torque steer was a RWD problem, corrected with linkage bars. With FWD cars, it was realized that if one axle was longer, it would wind up more (although I'm not exactly sure what effect this would have, other than hop) this is the problem Mini addressed.

 

I'd like to ask a question that I've been wondering about for a while. Please don't laught at me too bad if it's a stupid question:

I never really understood how 'equal length driveshafts' could make any difference, unless the MINI actually drives both driveshafts? Does it, or does it just drive one side?

If it already does drive both driveshafts, then what is LSD there for, and why would you need LSD for more power, since the MINI would already be driving both axles anyway? (If both axles are driven, LSD is only advantageous for allowing slippage when traction is lost or when turning, but be of no advantage in a straightline)...

 

I run 36/36. You should choose a number around 34-36 and use it all around. The perfect number depends on the weight of the car, really. You should choose one pressure and run it for a few thousand miles, making sure that you do not vary from that pressure. You will begin to see how all 4 tires wear. If they're wearing too quickly in the middle, you should take out some pressure. If on the sides, add some. It's trial and error, to a point.

 

get some 14 lb wheels and low profile tires and experience torque steer !!!!

 

Another thing which should be said about tire pressure...

The MINI has more weight up front than in back- significantly more [worse than 60/40 I think?]. This means that you may not need the same pressure in all wheels. BUT, be very careful in choosing relatively higher tire pressures in back, because theoretically you can really oversteer-bias the car, which can be dangerous if unexpected. It's safer to run less pressure in back...which can add a little understeer, but keep it controlled.

 

FlynHawaiian,

I think it is related to the new wheels. Are they the same width and offset as what you replaced? By changing the offset and width you can move the center of the contact patch further from the centerline of the car. This will change the leverage that the wheel/tire has and make any surface imperfection more noticable.

There is something known as "tramlining" that feels like torque steer but can occur even while traveling in a straight line at a staedy speed, no acceleration. It is caused by an uneven pavement surface. The car will want to pull from side to side when you negotiate this uneven pavement.

I notice it everytime that I change from my 175/65-15 wheels to my 195/55-16 wheels. The 16" do it all the time, but it is pavement related. Nothing to do with alignment or suspension.

Try changing back to your original wheels and tires.

Just a thought.

 

Well, I went from 205/45/17 to 215/40/17. I figure it has something to do with that. The wheels weigh about 16 or 17 lbs. The car seems like it has so much more power, than it did before, it's kinda scary :D

 

Okay this might be the problem, there is 29psi in the front and 30psi
in the rear. I have a set of BFG g-force KDW2 215/40/17. What pressure should I be running :/

 

^^ might want to be around 34psi. 29-30 is too low for street.

you would feel less torque steer on a low pressure tire though...so pressure
it up and feel the real torque steer, i guess....

 

I'm running 215/45-17's on Flik Wasps. I run 34-35 in the front and about 32
in the back. Again, I have no LSD and I have no torque steer problem.

 

^^ on mine, it's not so much torque steer, but more of a steering feedback
(response) issue. you can feel the front tires pulling the car through the
steering wheel as it should...but that feeling is not the best feeling.
that's all.

 

Here's a scary thought. The Menehune's apparently have fixed my car. The torque steering is gone, the clutch feels better. But the brakes cannot keep up with the car at high speeds :/. Ugg... how are you people doing engine mods without upgrading the brakes, when the stock ones, cannot keep up with my stock engine :/

 

What brake problem? In Germany on the autobahns, you only use the left lane for passing. So it's common to be blasting down the road at 130 mph and move to the left without slowing down to pass a few cars in succession. Inevitably, the first car in the string you're about to pass sees you and pulls out to cut you off even though you may be doing 50 mph faster than they are. I've had to stand on my brakes many times in the above scenario and the stock brakes pull the car down very rapidly and in complete control. You must drive faster than me.

 

I was also doing curvies not straight lined driving. Dynamic forces are quite different then in straight lined driving.

 

SAI will have some affect on steering input especially on bumpy roads; most FWD cars have negative offset - the SAI falls outside the tire's center line. This will help to keep the front wheels pointed more or less in a straight line if one wheel loses control while the other one does not...like driving on a bumpy road.

Imagine your own feet for example as a tires. Imagine a center line running the length of your feet. Negative offset places the SAI leverage point outside the center line. As you run, try to feel what your feet might feel like with a point of leverage to the outside, and another to the inside - positive offset. Negative offset trys to steer your feet towards the center line - stablizing the direction. Positive offset trys to steer your feet towards the center line too, but the tires are now point away from the center fo the car allowing each tire to grab in opposite directions.

I don't know if this is really your steer problem...small changes in SAI dur to wheels alone have not made much difference in my car. and, if you've adding in a little negative camber, SAI is kicked back out any way.

An LSD can - depending upon the type - affect steering response. If it locks and unlocks it will allow an on-off torque syeer feeling.

To another question above - Equal length half shafts absorb the same amount of energy at the same time. A shorter half shaft will absorbe energy quicker.

tire pressure difference act like changing trail/caster and pneumatic trail; the differences place one tire ahead of the other, or behind the other depending upon stock orientation.

 

MEB
What you are talking about is the scrub radius. {the point where the imaginary line SAI intersects the road in comparison to the center of the tire} negative scrub radius, as you mentioned, is when SAI intersects the road to the outside of the tires centerline. A change in wheel diamater normally doesn't effect scrub radius to much, but a change in wheel off set sure can.
However I think the feel in the steering wheel on this particular car is probably normal, for the mods.

 

I didn't read all the replys, but my over-all reply was meant to remind the reader that offset will indeed affect those little steering torques generated first at the contact patch - as you also wrote. The degree of this feeling - good or bad - is really determined by the car's over-all design; some cars, because of other geometries, can 'absorb' more change without much degredation steering wheel force or stability. This is rim width and or tire width dependent. Negative offset and negative scrub radius are like saying 12 or a dozen; these two terms are inextricably linked...the two terms describe the same thing in practice. As well, SAI is the same thing as Kingpin axis, the latter being a more internationally recognized term.

Camber influences SAI as well - directly!

But also, that tire psi deviations can affect steering torque dramatically by changing mecahnical trail/caster and therefore pneumatic trail. This one is independent of tire width and diameter...although the degree will depend upon diamter and width.

FlynHawiian,

Okay, I went back and re-read...What is your camber set at? Extreme negative camber REQUIRES a little more caster to get back some straight line stablity - tracking. And, what kind of LSD do you have? These, as I wrote above, can make the steering do very 'funny things'. The combination of the two, especially if too much camber on a bumpy road is aggravating traction, can cause the sensation you describe. Lots of camber will cause tires to crawl along the side of some compression bumps, rather than over the top of these types of bumps if camber were set to zero for example. This is part of a phenomenon known as camber thrust; compression inputs are no longer vertical,(simplified) but at some angle to vertical.

Extreme camber and toe out angles degrade braking performance...sometimes by a bunch!

 

You need to re-read your post. I'm not a mind reader. Not sure how you got from A to B. But interested nonetheless to know why you think you need better brakes. Please and thank you...

 

if I told you I don't know what the settings are I doubt you would believe me. I need to call up the shop and have them fax me over what the settings were. The lsd was a stock lsd on the 06

 

It would be helpful to know what the offset of the new wheels is. Any decrease of the offset would make tramlining more noticable.

The 215 tire would also make tramlining more noticable. The wider the tire the more noticable the problem. Also the shorter sidewall, 40% aspect ratio vs 45% apsect ratio, would also translate into more noticable tramlining.

So there are a whole bunch of things happening here. Difficult to point a finger at any one thing.

I would try 3 psi more in the fronts and leave the rears where they are.

 

I thought tramlining was caused by the grooved tread design of some tires, adn those grooves catch the rain grooves of some American Interstate highways??? I've never heard tire width alone had anything to do with it. I can tell you the Pirelli Eufori@ equipped '04 test car I drove tramlined, but my Dunlop SP 9000 equipped '05 MCS has never tramlined (on the same stretches of autobahn).

 

Tramlining can be caused by a few things, but more than likely here, a 215 sized tire; the tire grabs at every undulation and yanks the steering wheel. As noted above, offset may or may not aggravate this condition. Directional tires usually tramline much more than any other type. Sidewall compliance will contribute much to this phenomenon...as will suspension compliance. But a stiff sidewall combined with a resiliant suspension setup will tramline less than a stiffly sprung car shod with short, stiff sidewalls.

Tire size or range s is part of working suspension design. subtle movements in the suspension may work for some sizes while not others.

Part of the difficulty here is that this setup is niether fish nor fowl - niether road nor track. A setup designed specifically for either - by BMW - is more than likely vise free...like the stock car. FlynHawiian, not picking on you, hope you know that. You're trying to set your car up for aggressive driving and there will be compromises...I know you know this truth. Some of these compromises will not be desirable to you. Super wide tires on anything but glass smooth roads will from time to time send sensations to the steering wheel that you will not like. It takes less suspension movement to 'upset' a wide tire than it does a narrow tire if the original suspension design factored a narrow tire. 'upset' above is a whole bunch of bad things we can feel, but perhaps not measure...or even describe fully.

Stability is a very important component to consistency. There will be a fine balance between stability and responsivness. That balance is determined by the individual...hopefully with a little knowledge.

 

Good post MEB
The more mods I do to my car, the less efficient it becomes as normal transportation.
But it sure is fun