The recent accident reports and spinouts we read here lately makes one start thinking about automotive design and factors such as wheelbase, suspension, etc.

My question: (and nope, didn’t do a search) Is a vehicle with a shorter wheelbase more prone to spinout?

My thoughts: Probably yes (and maybe obvious), but I am guessing. My question is at its most simplistic level since all sorts of factors (road conditions, tires, suspension, weight, FWD vs. RWD, rollover before spinout, and a lot more stuff) all come into play, and probably synergistically. But, I would think a shorter wheelbase causes more oversteer with greater potential for a spinout. Not sure though.

--Spike

 

Shorter wheelbase=more willingness to rotate. E.g. better turn in, more responsive handling and yes...easier to spin.

 

It may not help but I don't think the wheelbase has much to do with all the spinning that seems to happen with Zs.

Here is some food for thought.

When the Audi TT came out, one of the things that they touted was the aerodynamics, a short time later, after several spin accidents and a fatality of a famous race car driver in the UK, they recalled the TT and put on the spoiler stiffer springs and re-valved shocks.

I am of the opinion that the Z has similar issues when the right conditions present themselves.

Chris

 

Shorter wheel base does not neccarily mean 'less willingness to rotate'. Its more or less the rotationa interia that determines that. Thats why mid engine cars turn more naturally than RR which turn more naturally than FR. The center of mass and the radiuis from the center of mass matters more. If it matters, even though RR engines have a lower inertia (' willingness to spin' ) they are less likely too because the rear tires have more friction.
In other words, what matters most is your suspension geometry. I can set my rear camber to -4 degrees, make my rear sway bar real stiff, front real soft, make the rear strut very stiff, and cause the car to spin out with EASE, or I can find a neutral setting which gives me some understeer while still maintining the ability to power oversteer

 

I noticed RWD with a decent amount of torque are easier to spin out. Bad rear tires and more front heavy doesn't help either. That's why I hear a lot of guys are trying to balance the weight more in the front with rear.

 

Increasing grip in the rear will make you less likley to spin out. End of story.

 

At least 90% of all accidents are caused by the operator of the vehicle.

 

+ 1,000,000

 

+2,000,000

 

RWD does not have torque steer. People need to learn how to drive. Most all cars have the alignment to where the cars understeer badly just because of so many bad drivers.

 

This is also true, howerver a shorter wheelbase does equal quicker rotation. Think about it. Imagine if the wheels for the Z were a foot apart. The car would turn really really quickly (and look retarded). For an example of long wheelbase cars taking longer to rotate refer to the most recent epesode of Top gear.

 

and…
I think your response(s) is the correct answer. A simple analysis using physics seems to confirm this. Here is a short read that gives the formulas and discusses the “wheelbase/rotation” issue:

http://en.wikipedia.org/wiki/Wheelbase

The argument certainly becomes more complicated when you introduce factors such as FWD vs. RWD vs. AWD, suspension, slippery road surfaces, inexperienced drivers, etc.). Your argument (“Imagine if the wheels for the Z were a foot apart. The car would turn really quickly…”) reduces this to its most elemental level and makes more sense of the many spin out stories we read here. Good explanation.
--Spike

 

Keep in mind this,

Assuming that a short wheelbase makes it easier to rotate (spin) it also makes it easier to recover from that spin.

A big car, once it starts to go, it goes a long way...

 

has nothing to do with the car, it is 99.9% driver error and not knowing the capabilities of the car they are driving.

 

Longer wheel base = less grip to oppose the rotating (spinning force).

 

That’s a good point. I believe you have the answer or at least a good part of it.

Let’s take two cars: a stretched limousine and a Z. That’s an extreme comparison, but makes the example easier to understand. Both cars go into a turn on a slippery surface, and the rear tires break loose. In this example both rear ends are actually sliding at the same speed, but the shorter wheelbase of the Z causes the car to rotate around the CG much faster than happens with the limo. It is simply that the Z’s rear wheels are much closer to the CG and thus have a shorter distance (less arc) to go before full rotation (spin out). Even though the limo’s rear end is moving at the same speed as the Z’s; the limo’s longer wheel base results in a much larger arc, and more distance and a longer time to fully rotate.

So what does that mean? Well, the limo driver has more time to react since it is going to take longer to rotate. Albeit he has his hands full with that big beast, but time is on his side.

The Z driver doesn’t have this going for him. However, the Z’s driver (as you point out) has a better opportunity to correct the skid. The same forces are at work with wheels closer to the CG so counter steering will tend to bring the car back into line faster. But there’s a caveat. The Z’s driver must react quickly (since he is going to rotate faster) and more precisely (since over correcting will put the car into the same or worse situation, just in the opposite direction).

So… it comes back to driving skills and experience. Probably not the best idea to teach someone to drive using the family sedan, and then quickly turn them loose in a high performance car. I guess we’re reading what happens when you do that. But… good stories anyway.
--Spike

 

It's simple physics.

The force required to keep the car following in the arc (and the rear tires in line) has to be right or the car will spin out, you slide and change the radius that the rear wheels are traveling in, and you change the radius of the CG of the car by turning the wheel to steer less, straight, or counter steer.

You have to have the inward directed tractal force (part forward, part side) be equal to the required force to provide the centripetal acceleration (F = m*v^2/r). Mass is constant, V is assumed constant, thus the only "variable" in the equation is r.

If you have a longer wheelbase, such as the limo, the radius will change a LOT more, meaning the force required will decrease a lot more, than say with a Z... THAT, is why its harder to spin out a longer vehicle.

A truck in the rain is a different story, because the tiny amount of weight in the back will make hydroplaning a piece of cake when turning.

-Tyler

 

Having nearly spun out many many many times (and recovered), I could safely say that the farther back the CG is on the car, the easier it is to spin out. Wheelbase seems to be the opposing force. The longer the wheelbase, the harder it is to spin out. Yes, a longer wheelbase doesn't mean its rear won't break free; the rear WILL break free, but it does it more gently than a shorter wheelbase car.

 

Firehawk... I agree about built in understeer, but to be honest the poster did not use the word torque steer. Bad torque steer is when you stomp on the gas and you change lanes .

 

I spun my 928 a few times. I have never spun out in the Z .