I have been cursing the net a lot and was curious about Lowering. What is the benefit of lowering our cars?

 

It depends on the point of view I guess.

Some folks like the look - and that alone is their joy in the exercise.

Other folks lower the car to improve handling, which if done right can make quite a difference.

A stock Mini on good street tires can pull pretty close to 9/10th of a gravity of lateral acceleration (.9 G).

Mine can do 1.1 G, which is a heck of a thrill if that's what you are in to.

There are surely trade-offs though. Lowering done badly can raise heck with a nice car, and doing it right requires some matched components and real expertise. I'd reckon the price range varies from less than 1k to north of 2.5 k depending on the components used.

A lowered car will teach you to watch speed bumps and driveways very carefully, and will of course ride much more stiffly than the stock set-up.

The physics of lowering includes a reduction in the center of gravity, which can reduce weight transfer from the inner to the outer wheels in the corner. In addition lowering is often accompanied by an increase in the negative camber of the wheels (the top can be made to tilt inwards a bit) which offsets the body roll to put the tire in optimum alignment with the pavement. Getting negative camber on the front axle helps to reduce the natural understeer of the Mini chassis.

It's a bit of a slippery slope though, so I'd make sure you are certain of your goals and approach before starting forwards...

Cheers,

Charlie

FWIW, my chassis was set up by Turner Motorsport of Amesbury MA (one of the top race shops in the country, running BMWs in Grand Am and other series). Marco is the man in charge, and I have found his advice and expertise invaluable over the last six years.

 

Charlie, great advise!

 

That good info thanks. What does the plastic hanging from the bumper do?

 

That is a front spoiler.
It produces downforce on the front of the car.

 

That black thin piece hanging down at 90Deg? Wouldnt that disrupt airflow under the car?

 

The benefit of lower center of gravity is usually offset by increased roll coupling.
A lowered suspension typically has higher roll centers than a stock one,
and this usually increases weight transfer more than the lower center of gravity decreases it.
Also, the decrease in suspension travel (compression) can interfere with the tires and road
staying connected on bumpy roads.

 

the lowering however, can greatly increase the probability of various bits of chassis staying connected to a bumpy road!



and that vertical lip under the bumper is my plow attachment. I also use it to grade the driveway in springtime...

 

This. Lowering the center of gravity is really a minor issue on a street car. There are three main effects: Increase in suspension stiffness, reduction of suspension travel, and changes in suspension geometry, as Cristo explained. Anything more than 3/4" or so on most production cars is going to hurt the geometry more than the additional stiffness and lower CG will help. Most people don't even understand what roll centers and suspension geometry are, so 99% of the time, those effects are ignored, even though they can be the biggest factor in how a car handles.

 

And, that peice of plastic isn't there for downforce (although it may do that as well) . . . it's there to help force more air through the radiator and intercooler.

 

Interesting post. When going with something like the H-sport springs that only lower the front and rear 1"....is anything else really needed (adjustable rear control arms?)? Does the ride change much at all? I'm sure new shocks would be a good idea also....

 

"Only" 1 inch is a LOT for these cars....trust me.

New shocks (Koni Yellow or Bilstein) are a good idea, and would make a big improvement on their own for a completely stock car.

Rear control arms are also worthwhile.

- Andrew

 

Is there a general consensus as to which springs are a better option? I've been looking at getting the H-sport springs, or TSW Mini springs.

I think the H-sports drop the car around 1"...while the TSW's are around 3/4". Is one better than the other?


Thanks!

 

For the 2nd generation Mini, the NM springs are popular (lower than I would go) and the TSW springs seem good too.

- Andrew

 

to the OP, what are you trying to get from lowering?

to maximize any benefit from lowering you're going to have to go to coilovers. springs do the job if you want to get rid of some wheel gap (which may be enough for the OP) but coilovers are going to give you adjustablity and a better ride IMO. i went with H&R lowering springs when i first got my '07 MC and after a year i upgraded to kwv1 coilovers.

for me lowering was for looks but i made sure the parts i got would detract too much from the comfort which i am fine sacrificing. control arms, endlinks, camberplates etc. are things to consider but are not necessary to upgrade unless you are planning on going down low, if you are just dropping an inch or less you its not 100% necessary.

HA! im 4in down. talk to me about low.

http://www.flickr.com/photos/raaawrr/6026277731/http://www.flickr.com/photos/raaawrr/6026277731/ by http://www.flickr.com/people/raaawrr/, on Flickr

 

There was an article from SCC several years that discusses the roll center, center of gravity, and their interaction. It's also got some good drawings to illustrate this.

http://www.modified.com/tech/0508_sc...t_3/index.html

-JL

 

Cristo, Have you got a reference or two for mapping out the roll centers for our cars specifically? You raise an excellent point here, and I've been mulling it over a bit and have difficulty visualizing the geometry.

The illustration at http://www.modified.com/tech/0508_sc.../photo_02.html suggests to me that the -2.5 deg of camber that I am running might actually contribute more to lowering the front roll center than anything else.

I'm going to ask Turner's to re-do my chassis this winter, and look forward to chatting with them regarding the trade-offs involved. I'm hoping to start with a blank sheet of paper - I'm also re-examining the linear versus progressive decision.

Cheers,

Charlie

 

cristo misspoke...a lower suspension typically has lower roll centers than stock, not higher. I think he meant a higher roll couple.

You generally don't want to lower the roll center, which is what happens when lowering the car. The roll center is moved farther than the COG, increasing the roll couple.

If I'm not mistaken, moving the top of the strut in (as in adding negative camber with plates) would raise the roll center, a good thing. It can have an affect on SAI but that's another topic.

- Andrew

 

Yes, andyroo, that's what I meant to say.

I made some handmade drawings on graph paper once (around 11/2004) to illustrate
the approximate roll centers with the suspension in various configurations
(stock, lowered, rolling to one side), but they weren't terribly precise nor pretty.




They were on this thread around post 20/21 - but it seems the images have disappeared - the description remains however:
https://www.northamericanmotoring.co...-geometry.html

 

I mis-read cristo's post - missed what he said, and completely attended to what he meant. Kinda funny.

By changing the strut angle to increase negative camber, the roll couple apparently increases, right? The roll center drops, and the CG remains the same.

So - more weight transfer, but better bite on the loaded front tire as the tire is closer to its "happy place" as the static camber and dynamic roll cancel.

All these factors interplay - leaving the question 'which one dominates?'.

The work Turner's did for me increased the cornering capability of the car significantly and detectably, which suggests that their recipe is informed by experience and measurement.

But that does not mean that there isn't a better recipe out there...

Cheers,

Charlie

 

The roll center is raised when increasing negative camber with plates. Draw yourself a picture.

The drawback is in the steering axis inclination, but that is greatly outweiged by the advantages of a proper alignment.

- Andrew

 

Anyone notice an increase in MPG after lowering their mini?

 

Good advice.... back to my studies I reckon. Thanks for teaching me.

Cheers,

Charlie

 

In theory, lowering the car without any regard to anything else will lower the roll centers, not raise them. Higher roll centers decrease roll moments and lower roll center increase roll moments. A higher roll center will load the tires more quickly, say in transient, but a lower RC will eventually saturate a tire much sooner, think steady state cornering.

The center of gravity and RC are tethered via a virtual lever arm. When the steering wheel is turned all forces migrate from the RC to the center of gravity and then to suspension linkages and eventually to the tires. If the virtual lever arm or moment arm is longer it will act on the CofG with greater leverage as a car reaches steady state. In general terms, placing the rear RC higher than the front will load the rear tires faster helping to rotate the car.

Keep in mind that roll centers move and as they do so they act on the CofG...you can't think of RC location as a static location.

Increasing track width also raises RC locatiion.

 

Re camber, yup. One can correct SAI by installing wheels with lower numeric offset...and by adding spacers. This will help place SAI fulcrum closer to the contact patch's centroid axis...closer to the region where self sligning torque exists at the contact patch. This helps increase steering feel.

Increasing track width also raises RC...on the Mac strut end. Important since this end carries 62% of the car's mass. Increasing rear track will probably decrease camber compensation...add a wee bit more neg camber.