Hi

I have a normal MINI Cooper with SS suspension (non SS+) with the following mods:

- Eibach lowering springs (-1" front and 1.2" rear)
- Bilstein SP sport shocks
- 215/35/18 tires

My question:

What to do next to get a better ride without loosing more comford?
I only use the car on street (no track and...)

I am thinking to get another rear swaybar. But which size is best for me. 19 or 22mm (for only street using)?
Is it a good idea to change it or should I leave it stock?

 

definitely change it to a 22mm and preferrably an adjustable one.

 

control arms would help, in your case i'd get h-sport, which is softer feel, the alta and madness ones are helm joints and will transfer just about every single bump to your spine.. believe me!

 

How have the new springs and dampers changed your Mini's roll couple distribution? If you can answer that, you can determine what size bar to use. And bar size increases are in the forth power, that means cubed! A 22 mm bar is 35% stiffer than a 19mm bar and 60% stiffer than the stock bar. If the bar's design incorporates a more effective lever arm, ie longer, it will be even stiffer.

Is the car lower? If so, roll couple moment has increased - not a good thing. How much longer is the lever arm up front verses the back? What will you do to compensate for this...this can really screw up roll distribution.

Can you move roll centers so that the actual migration of the roll centers cause weight to transfer without the aid of big springs, dampers and sway bars? Probably not, but coming to that answer will teach you a lot.

At some point, there is a disadvantage to transfering more weight out back. Much of this concerns wheel rates - the actual spring and damping rates at the contact patch based upon suspension leverage and swaybar size - camber curves and finally tire compliance. If you transfer too much weight to one set of tires, the tires saturate and poof, no more traction. And, what are the spring rates? What are their frequencies/sec or /minute? Do the front and rear spring frequencies match based upon the sprung weight of the car?

Getting the center of gravity as low as possible is the single most beneficial thing you can do for handling. However, doing so comes with compromises with a non-race one-off plateform - roll couple is increased. This means weight is transfered with more force which requires more resistance - bigger springs and dampers - not necessarily a great thing for ride and traction in the heaviest cases...you need to preserve good camber characteristics too so grip is good thru as much of roll as possible. And you must keep a handle on the absolute distribution of weight as determined by springs, dampers and sway bars. Hint; which ever end of the car resists roll more, is the end of the car where more weight is transfered to or distributed to.

Or, you can guess.

I'll disagree with my friend Kenchan and suggest a 19mm bar. Then, go to at least one track event. You may feel the car is perfect, or a little twitchy or not responsive enough. You have to push the car to its limit...or near its limit to find out what is working and what is not. Don't exeed your own limits in the process. You may come away thinking, as I did, that I can push this stock Mini waaaaaaay beyond any reasonable speed on the street. If it were a track only car, I would have lots of work to do...

 

ok doc, no apple for you today.

 

I have ordered a H&R 19mm sway bar for my car. The shop didnt recommed a 22mm bar for my Cooper with standard SS front bar.

I first will try the softest setting. If it isnt enough I can always use the stiffer one

Is there a lot off difference between the stock and the H&R 19mm swaybar under normal (street)driving? I wont use my car for tracking. Only on the street.

What are the pros/cons between the stock and H&R sway bar?

 

do you also not have the ss+ rear sway? its 1mm thicker (i think) than the one on the cooper suspension. there was an ss+ bar in the marketplace yesterday for 30.00. another option if you dont like the 19mm.

 

chows4us is selling his. i sold mine to a MC owner too when i bought my
22mm Alta...that and the springs.

 

I'm confused about something...you're worried about comfort but you've lowered the car, obviously less travel in the suspension and therefore stiffer rates. The thing that really confuses me is that you're on 18's. If you're really worried about the comfort of your car then drop down a size or two and put some sidewall on the tires. That will do more for comfort than anything else you could do right now.

Personally i would not put a 22mm bar on any of these cars. My dad finally realized I was right after he spun the car 2 or 3 times out of 5 runs! The 19 feels more stable, but we'll have to see once the season starts back up. On a full out race car I would do things differently but it's not a bad combo for a street car.

 

the reason why I noted 22mm is because im running 22mm on my MCS
at the firmest setting and i can go even a tad stiffer if I wanted to on my
car without becoming tail happy. some use the h-sport 26mm bar on their
MCS on the middle setting which i am assuming is probably a tad stiffer
than wat I currently have.

considering that, i think the 22mm at the soft setting would be quite
the level of turnability one might want on the MC with the ss, but
again i have no experience with the Eibachs + the shocks that he has
or fiddling with the MC so I am assuming what Meb mentioned above
is what one might want.

stores can tell you their experience or wat their customers prefered,
but it's ultimately your driving style, other components on the car
that will tell you if stock, 19, or watever would suit your needs.

 

i have spun my car on the middle setting, but personally ive never had a single problem aside from that single spin (when i stomped on the brake when the rear started going, and i learn now that's the worst mistake i can ever make!)

anyways... i still think with my bar in the middle on the street is fine... i dont drive it like a stole it and honestly on the street even on the middle setting there isn't noticeable changes in the handling... autocross there's a noticeable rear end drift, but you ask me, easiest thing in the world to do is to just add gas!

 

here, refresh your memory...

https://www.northamericanmotoring.co...427#post592427

 

Totally agree

Because of the lowering, different dampers, lower profile tires I lost a lot of comfort. So I dont want to lose more comfort by adding a sway bar or other things. I choose 18" and lowering and lower profile tires only for the looks of the car. Even if it take away the comfort of the car.

 

sway bar takes side way actions, not vertical load, therefore, the swaybar as nothing to do with ride-comfort

 

Thanks Will fit the sway bar next week. Cant wait to test it

 

Actually, it does affect ride. Another reason a large swaybar may not work for some applications.

A sway bar is a torsion bar. In use, one end turns up as the other end turns down, amplifying additional force to suspension movements as it returns. A sway bar also ties the two suspension sides together. This is of particular importance with an independent suspension; as the suspension moves up and down, the sway bar twists as noted above. But also, an input from one wheel will be shared/transfered to some degree by the other wheel. To what degree depends upon sway bar size and to a lesser degree suspension geometry - camber in particular.

One of the biggest challenges is to figure out what wheel rates are required whcih is determined by roll couple distribution - how much weight transfer you want over which set of wheels. Once you've figured this out, you have to decide how you want to allocate the work load to the springs and sway bars since each affect weight transfer and therefore wheel rate. You can simplify your work and get the springs rates just right, and use only a front sway bar to adjust weight transfer. In this case you might have fairly large rates in the rear, but tone them down - add in a little understeer - with the front bar. Comfort is a big part of the performance picture on the track too. A driver who is beat up by his or her car isn't going last long. So splitting the work load between springs and bars is a good idea.

A 22mm or a 26mm bar might be an excellent choice for autoXing, but I would never use a 26mm bar for long fast sinuous roads.

You can also fine tune the action of a sway bar by using soft or hard bushings.

And keep in mind what I wrote above; sway bar increases are in the forth power. This makes a 26mm bar 39% stiffer than a 22mm bar and 133% stiffer than the stock 17mm bar - if my math is correct. That is a HUUUUUUUUUUUUGE difference. It's huge because these differences affect wheel rate. Another way of looking st this is by comparing spring rates; lets use a 300in/lb linear rate spring. 39% stiffer equals a 417in/lb spring and 133% stiffer equals a 699in/lb spring. This is a huge contribution...one of the reasons I constantly rant about overly large sway bars. If on the other hand you increase the size of the front bar proportionately, roll distribution remains the same. However, roll distribution becomes much quicker. Stiffer suspension set-ups also require stiffer tires - less compliance.

[/quote]

 

Very true, it does affect ride, just not the same as stiffer springs, but don't think sway bars are magical things that will improve cornering and doesn't affect ride

If its to the 4th, then a 19mm sway bar would be 1.99 times stiffer than the 16mm bar in the SS suspension (not SS+), and a 22mm bar would be 3.57 times stiffer than the 16mm bar.

My recommendation is either an 18mm or 19mm rear bar for the MC (SS) suspension, going 22mm will most likely be too stiff. I have the H&R 18mm bar in my MC (SS) and there is some rotation when I trail brake or lift the throttle mid corner. On icy/snow covered roads I can quite easily bring the tail out by just doing quick left/right twitch with the steering. Unless you are experienced with controlling oversteer I think 22mm will be a little too much.

 

hey how dead can a horse get?

 

Well if you stop beating on it maybe it'll stay dead.

Its actually after reading your post that I was a little worried someone might try and go with the 22mm bar with the normal SS.

Ok I'll stop beating the dead horse now, before I rank up 6000 posts too.

 

yah, you do that post *****. read the entire thread again from the beginning!

 

i heard something about horses, that is Berky territory, what is going on now?????

 

nothing... he wanted to post again that 22mm was too firm for MC's from
his hypothetical calculation without considering the other aspects
of the car like which springs, damper settings, tires, wheels, etc. etc. and
blaming me that i had BS'ed my way over and over to 6000 posts.

well ok, maybe 1/2 of it was crap...

 

I'm going to have to disagree with you there, partially anyway. A sway bar is another way to stiffen the suspension. Putting big sways front and rear can be like putting 1000lbs springs on. The problem with it, even not taking it to that extreme, is that you're taking the independant-ness out os the suspension. Also the quickness of the weight transfer depends on the shocks.

 

I've got no numbers or theory to back it up, but I've got a Cooper that came with sports suspension (not plus) and now has the JCW suspension upgrade springs and struts, the stock sports suspension (not plus) front swaybar, and the RDR 22.5mm rear swaybar set on the softest setting.

Yes, the above is correct... JCW springs and struts with SS (not SS+) front swaybar.

It works for me. I've only experienced oversteer at a level that can (and did) cause a spin on a sweeping turn in an autocross, in the wet, when I was trail braking.

Other than that, on the autocross course and the track, I still have a some understeer when on throttle (accelerating), a hint of understeer with maintenance throttle (steady speed), and neutral to a hint of oversteer when engine braking in a turn. Brakes in a turn at speed is bad with my car.

Once my car starts to come around, it spins really fast.

I'm sure if I moved the bar to full stiff, I'd have all kinds of problems though.

I'm not recomending that big a rear bar with that small a front bar, just stating that that is what I have, and it works pretty well for me. We'll see what happens when I add camber plates - gaining more front grip... it could cause a problem in that I cannot back the rear bar off any from where it is now, and more front grip will mean (relatively) less rear grip.

 

This gets my vote for honest response of the year!