# How is a firm ride defined?



## beware_phog (Mar 7, 2003)

I've been reading a lot about cars that have a firm ride as opposed to another car. This is obviously all pretty subjective, but it there some sort of standard "FIRM" rating where an F150 on a rail road is on one side and a Mercury Grand Marquis is on the side?

Is there really a big difference between a 330 with and without sport package? is a 330 with the sport package "rougher" than an X3 with a sport package? without the sport package?

Anybody who's driven a lot of Bimmers provide me with some generalities?


----------



## Fisch330ciTB (Jan 10, 2002)

In my mom's non-sp seats, 02 330ci I hardly feel the road, pretty smooth.
It is a little rougher of a ride with my '01 330ci SP, but now with my coilovers and sways and 18's, it is like a world of difference on the lower back. My ride is a lot stiffer now, but I wouldn't change it for something softer.


----------



## The Roadstergal (Sep 7, 2002)

The only real metric would be spring and shock rates, no? But I don't know enough to speak to how you'd integrate them into a number you could compare across cars. The weight of a vehicle would be a factor, too.


----------



## CaliJeff (Jan 28, 2002)

You can bounce a quarter off her ass?

EDIT:
OOPS!!! I thought this was in off topic. Mybad.


----------



## doeboy (Sep 20, 2002)

The Roadstergal said:


> The only real metric would be spring and shock rates, no? But I don't know enough to speak to how you'd integrate them into a number you could compare across cars. The weight of a vehicle would be a factor, too.


Tire profile and wheel size also have an effect on ride "firmness".

Given the same diameter, the 16, 17, and 18 inch wheels will all feel different, with the 18 most likely feeling the most "firm".

Tire sidewall thickness also effects perceived ride quality.


----------



## F1Crazy (Dec 11, 2002)

IMO firmness defines car movement in the corners, ea body roll and how it copes with elevation changes, not only what the ride is. 
Springs and shock absorbers have bigger effect on firmness than tire and wheel package. Both SP and non-SP 330s come with so called sport suspension but different wheels and tires. You may say that both cars have the same firm suspension with non-SP car trading the grip for more supple ride.


----------



## ObD (Dec 29, 2001)

> Is there really a big difference between a 330 with and without sport package?


Yes. To the point that anyone who rides in my car notices the stiffness immediately. It's really a personal preference. My preference is the SP. :bigpimp:

The X3 with SP will probably be as stiff but with the X3's higher center of gravity the dynamics will change.


----------



## mkh (Mar 24, 2003)

Let me see if I can explain what firmness means. First, I don't think there is a rating (number) for firmness. It is a subjective feeling that everyone interprets differently. A soft ride to me may be a firm ride for you. Second, firmness is NOT directly related to the profile of the tire, but the suspension. I'll explain this later. Third, there is a difference between "firmness" and "harshness".

Now let's imagine a car going slowly over a speed bump. Normally, when the wheel hits the bump, you'll see it moving up first, and then the front of the car will also moves up but not as much as the wheel. Part of the wheel travel is absorbed by the spring/shock so the car only moves slightly. In case of 100% firmness (ie. without suspension), the car will move up INSTANTANEOUSLY with the wheel in exactly the same distance as the wheel travel.

On the other extreme (ie. 100% softness), the wheel moves up but the car does not. All the wheel travel is totally absorbed by the compression of the spring/shock. So, *firmness is the change of amplitude of the vehicle's vertical movement in reference to the wheel travel AND the response time of the vehicle in reference to the wheel motion.* The softer the ride, the longer the response time of the vehicle following the wheel moving up and down. So when you are going on a road with continuous minor ripples, and with a very firm suspension, your car will constantly bounce up and down.

The profile of the tire plays very little role in this regard, but will let you feel the "harshness" (impact) when you go over a pothole. With 70-series tires, you know that you went over the pothole but you didn't feel much impact. With 30-series tires, you will feel the impact hitting so hard just like it is hitting directly on you. This is what a "harsh ride" means.


----------



## nate (Dec 24, 2001)

It is all relative.

One's definition of a firm ride changes with his or her perceptions and expections. If you are used to, and happy with the ride of a '94 Lexus, then you likely will think that the ride of a non-SP E46 is very harsh.

While those used to a modified Miata may find it floaty and disconnected.

Drive and make your own decision.


----------



## Capitalist (Oct 12, 2002)

ObD said:


> Yes. To the point that anyone who rides in my car notices the stiffness immediately. It's really a personal preference. My preference is the SP. :bigpimp:


As far as I know, all 330's save for the ZHP have the regular sport suspensions by default. The perceived difference in "stiffness" is most likely attributable to lower profile tires because they ride rougher.


----------



## bmw325 (Dec 19, 2001)

Capitalist said:


> As far as I know, all 330's save for the ZHP have the regular sport suspensions by default. The perceived difference in "stiffness" is most likely attributable to lower profile tires because they ride rougher.


Even that difference is pretty negligible on the 330s-- because the regular 330 still comes w/ 17" wheels-- so there's about a the same amount of sidewall.


----------



## ObD (Dec 29, 2001)

Capitalist said:


> As far as I know, all 330's save for the ZHP have the regular sport suspensions by default. The perceived difference in "stiffness" is most likely attributable to lower profile tires because they ride rougher.


True, but I drove a non-SP suspension 330 before it was made standard on all 330's. Night and day.


----------

