Staggered refers to different sized wheels in the front and rear, '98 M3s and up have had a staggered wheel size, 17x7.5 in the front, and 17x8.5 in the rear. (E36) Staggering is done as to add traction, on a car with decent power and RWD, having some more rubber in the rear will give it some more grip and reduce oversteer. (bmw seems to think that unsersteer is much safer than oversteer.) A good example for this is Porsche, they stagger wheels due to their high rear weight bias, again per reducing oversteer, which rear engined cars "suffer" from. Staggering can include not only width, but height as well, this is to compensate for power, the bigger the wheel the more reduction in rotation, which equates to less spin and more grip. I hope that helps, if you managed to get through the rather longwindedness of it.

 

I'll put it even simpler. You want wider wheel/tires on the end with the most weight.
On a 911, this would the rear.
On a modern BMW the weight split is pretty close to 50/50, hence staggered wheels/tires are not required. Staggered wheels/tires on a car with a balanced weight split = understeer.:thumbdwn:

 

good point.

 

Except that staggering also reduces power on oversteer, so it is required on higher HP cars, even with 50/50 weight distribution.

BTW 95 M3 LTWs also have staggered rims.

 

Couple points from my exhalted, self-appointed position:

- staggering does refer to the relative wheel width - typically wider at the back although not always

- staggering is a tool in the suspension designer's kit box for adjusting the relative grip, front and rear, to achieve the car's design aims, along with static weigh distribution, suspension choice (i.e. strut or double wishbones at front; multi-link semi- or full-trailing arm, live/dead axle at the back, as well caster, camber, toe-in etc.)

- on racing cars (with serious power to weight ratios) staggering is used to transmit considerable (e.g. F1 - 850 HP) force to the ground via the contact patch and also provide a slip angle for the rear to exert cornering force

- on street cars (say most) stagger is mainly window dressing, with few exceptions being high-end supercars (M3, M5, 'Vette, Viper, Saleen etc. etc.)

- Having said that, if a designer chooses to introduce stagger it does need to accounted for in the design of the car in terms of overall safety and benefit

- Most people that are not "professional" do seem to feel safer in a car which resolutely understeers, and definetely do not feel happy in a car in which this tendency changes in mid-corner (as, sometimes happens in my Mini in a tight turn if you lift off).

- The classic definition of understeer is that the front tires run at a slip angle less than the rears, but the story of the car that enters the hedge back-first (oversteering) or front-first (understeering) is pretty accurate too :rofl:

Fun topic...

 

m3, corvette, m5........"high end super cars"???

come on. i thought that would be porsche gt, gt2, gt3, gt1, most ferrari's, lambos, mc12, etc, etc...

:angel: :angel: :angel:

 

Staggered tires for US drivers to reduce snap oversteer issues so you don't spin it while out joyriding. Cheaper for them to set up some plow in the front end instead of crashed cars. The 95's had it right on 7.5/7.5 widths. Staggered for the looks...

 

Uuh, understeer is running at a higher slip angle front versus rear, thus the front slides out.

Understeer is ALWAYS safer, but may not be as fast. Understeer is safer because the reacton of most people to the car not doing what they want is the right thing to do to reduce understeer, they lift off the gas. Doing the same thing in an oversteering car can lead to snap oversteer and spining down/off the road and hitting at odd angles.

And many "common" cars are starting to have enough power to require staggering to control power on oversteer.

But the big thing that you point oput is it is ONE TOOL to get teh desired handling, and that tool has be used with some degree of understanding.

 

Thanks a lot for your replies.

 

Uuh, understeer is running at a higher slip angle front versus rear, thus the front slides out.

Understeer is ALWAYS safer, but may not be as fast. Understeer is safer because the reacton of most people to the car not doing what they want is the right thing to do to reduce understeer, they lift off the gas. Doing the same thing in an oversteering car can lead to snap oversteer and spining down/off the road and hitting at odd angles.

And many "common" cars are starting to have enough power to require staggering to control power on oversteer.

But the big thing that you point oput is it is ONE TOOL to get teh desired handling, and that tool has be used with some degree of understanding.

If understeer is a safe thing, why do so many people add sway bars and increase tire pressure in the front (among other things) in an effort to decrease it? In other words what is the benefit to reducing understeer?

 

Understeer is safe. Manufacturers tend to over do it, so many people try to reduce it to a more reasoanble level.

Also if you reduce or eliminateundersteer teh car will be faster, but harder to drive at teh limit. Also if YOU reduce understeer, then stuff your car, it is YOUR fault. Not the car manufacturer.

 

If understeer is a safe thing, why do so many people add sway bars and increase tire pressure in the front (among other things) in an effort to decrease it? In other words what is the benefit to reducing understeer?

Terry, go after me if I'm wrong here, but wouldn't adding tire pressure in the front and adding a larger sway bar, also to the front, add understeer?
And as to add my two cents about why understeer, amongst other things blows..., I find it to be a lot easier to control oversteer and use it to my advantage, when I'm plowing straight (heavily understeering) I try to get some oversteer to correct it, there is nothing good about understeer if you know how to control oversteer.

 

I thought they were going to understeer for the driver impression of it "Wow, this car holds the so straight on the highway".

Everyone who drives my car is impressed with the understeer! So I thought it was for the consumer, not the accident.

 

I might be wrong here, but if you drive in everyday traffic and are not out on the track, is having less understeer something one might want to have?

I'm sorry guys, I'm just looking for the answer as to what the advantage of less understeer really is. Pinecone said less understeer makes the car faster but harder to drive at the limit. What does that mean? Do you mean the car is harder to handle at higher speeds and if so, in what way?

Tia.

 

this topic should really be answered by "the stig" around the airfield in a staggered/unstaggered ZHP and a staggered/unstaggered M3. :angel:

 

I'd like to see that, shall I call the boys at topgear? haha
For everyday "in traffic" driving, you should have no understeer or oversteer. These things happen when the car is push to its limits. But then you're at the limits, US will slow you down, OS is controlable and can keep speed up through a turn. (what drifting is based off) I'll just wait for pinecone to tidy all this up...

 

For everyday "in traffic" driving, you should have no understeer or oversteer. These things happen when the car is push to its limits. But then you're at the limits, US will slow you down, OS is controlable and can keep speed up through a turn. (what drifting is based off) I'll just wait for pinecone to tidy all this up...

I get it now. I did change my tire pressure to 36f/38r and it does feel faster and more nimble :thumbup:

 

OK, most recommended tire pressures are lower than optimal for grip. So adding front tire pressure tend to add front grip. Yes, there is a limit, but it is higher than most people run their tires.

In most cars, adding front sway increases understeer. Except that the BMW strut front suspension has a very poor camber curve, so you actually get less understeer it you limit front roll with a stiffer bar. Look at just about any picture of a racing BMW and see the inside frotn wheel lifted off the ground at the apex. YMMV.

Less understeer means the car is more balanced and thus using the front and rear more to their maximum grip and also not scrubbing speed off with one end. But you are closer to getting into oversteer.

Understeer is safe because ones natural reaction to the car not doing what yo uwnat is to lift the throttle or hit the brakes. This moves weight onto the front tires, giving them more grip and the car begins to turn. Also if yo ugo into a corner to fast, the front end scrubs and adds drag, reducing speed until you get to a point where the car can turn the corner.

Oversteer is the opposite, in most cases lifting or brakes are the WORST thing you can do and may have you immediately leave the road backwards. Read the threads of people in E46 M3s who always turn off DSC and then later wrap their car up due to power oversteer.

How much understeer is right for you? It depends. Your skill level, how close to the limit you drive and other factors lead into it. Realise for the manufacturer it is sometimes the legal department who sets the level, not the engineers.

But in accessing your skill level, be real, just because you THINK you are a good driver, is not enough, be sure, with track days, skid pad sessions and autocross. Over estimating your skill level can lead to a wrecked car and possibly injury or death.

If you don't know how to decide, DON'T CHANGE ANYTHING. Do some track days, autocrosses, schools, etc. When you are ready to do things, yo uwill know what is right for you and how you use your car most of the time.

 

OK, most recommended tire pressures are lower than optimal for grip. So adding front tire pressure tend to add front grip. Yes, there is a limit, but it is higher than most people run their tires.

Why? I would think that a lower pressure, due to a higher cf, would add grip. This because of the "larger" surface area provided. There certainly are limits, but what kind of limits are you talking about? At the track, I'll run high 20's in front and rear. On the street I'm high 30's. So, what are we talking about when "limits" come into in?

 

BTW, with proper camber in the front, is a larger sway bar still beneficial?

 

At the track and autocross you should set HOT pressures, for street cold pressures. Of course, at the track for the first session you set a cold pressure to give you a specific hot pressure, then adjust right after the session. For a high performance street tire the optimum grip comes in the 40 - 55 psi range depending on the tire construction. Lower tire pressure does not increase CF, and while it increases footprint, it does not change the load per square inch of contact patch.

Higher tire pressures increase grip due to the reducing in tire deformation during cornering. Low tire pressures allow the tire carcass to deform and can lead to lifting of the tread at the edge, reducing the contact patch. Really low tire pressures can lead to the tire deforming enough to actually unseat the bead causing immediately loss of air, in the middle of the corner, normally leading to the loss of the car. Race or R-comp tires have stiffer sidewall construction to allow lower pressures without deformation.

Yes, even if you get enough camber (and there are those who will say you can't get enough camber in a BMW front) the camber curve means reducing body roll tends to be a good thing. The camber curve effects what happens to the cmber during body roll, and in a BMW, the camber reduces as the car rolls. And if yo uhave lowered the car, it is worse. You get more static camber, but less dynamic camber to degree of roll. And if you lower the car too far, the camber curve will invert, meaning the camber will go positive with body roll. NOT GOOD.

If you car is really lowered, look under the front. The Lower control arms should slope DOWN from the car to the wheel. IF they are level or tilted up (which can happen, ask BahnBaum about his E30) you are in for an interesting ride. According to TC Kline Racing, the BMW frotn suspension has about 2.5 - 3 inches of total usable suspension travel. You can use that up by lowering, or by car dynamics during driving. But once you hit that point, the camber curve inverts.

 

Except that staggering also reduces power on oversteer, so it is required on higher HP cars, even with 50/50 weight distribution.

BTW 95 M3 LTWs also have staggered rims.

Right, because the weight distribution is only 50/50 when you're not accelerating, decelerating or turning. And since we're driving BMWs I'll assume we're always trying to do one of those three things, sometimes two at once.

The staggered rims were an option on the 1995 M3.

 

will staggered 20" wheels fit without rubbing on 2000 528I tire size 245/35/20 front & 275/35/20 rear

 

Probably better to ask on the 5er section