I can get hold of a 18.5mm JCW rear sway bar from the JCW suspension kit. Someone I know has had the JCW kit fitted but already had an Alta 19mm sway bar installed. My question is... how much stiffer than my 18mm sport suspension sway bar is the JCW? I think I read somewhere it was about as stiff as the Alta 19mm in its mid setting? is that true? if not how much stiffer will it be?

 

It would be almost as stiff as the Alta in it's SOFTEST setting. Just my opinion but if your upgrading the rear swaybar you should go with an adjustable 19mm such as the Alta or the H-sport and you'll be done with it.

 

At the price I'm getting the JCW sway bar at I'm just on a whim. I had no intension of upgrading but I'm being offered it at a price I can't ignore. I agree with you though, if I were in the market I definitely be looking at an adjustable bar.

 

Ben,

It's myself that fitted the JCW rear ARB. It's about the same stiffness as the 19mm ALTA on mid setting i believe.

Well worth it IMHO

 

can a JCW rear sway be installed without an alignment?
aaron

 

Well... owning a 2010 JCW - I can tell you from experience that the stock 18.5mm bar is SOFTER than an H-Sport 19mm bar on its softest setting. I changed the bar about two months ago. On advice from a track instructor - we put the bar on the softest setting first - just to get the feel of the change. The difference is pronounced! I will be going to the mid setting for street driving when I put the summer tires back on.

I have no specific information on Alta's 19mm bar vs. Hotchkis' 19mm bar... but I would expect them to be somewhat similar. I think you could probably call the folks at Alta to get a definitive answer. They are good people, do lots of research. I'm sure they know.

 

If it was a non sport JCW, it should have had a 17mm rear bar. If it were a factory sport suspension version, it would be an 18mm bar (same as the S with sport option too). The 18.5mm bar is only in the JCW suspension accessory kit used as a separate upgrade as far as I know (OP is also referring to the 18.5mm bar sourcing as a left over extra from that kit); apparently a not uncommon perception is the factory JCW's are equipped the same. Bought the 18.5mm bar myself as a one off (a lot cheaper apparently via a dealer selling on line w/ some discount than the 19mm aftermarket bars, but not adjustable as you mention); hence why I know/found this info via realOEM parts listing.

If true, I think your observations are between a 19mm aftermarket bar and either a 17 or an 18mm factory bar, unless you also separately upgraded to the JCW accessory suspension along the way. Small changes in diameter here of course change the cross sectional area by a greater percentage.

 

Correction

As MP1.6T points out - My comparison was between an 18mm bar and H-Sport 19mm. I did NOT hve the JCW Sport Suspension. So - the 18.5mm would be more stiff than I had experienced.

I still would suggest calling the Alta folks though. I am sure they have direct comparisons (at least the Hotchkis people could tell me the exact % differences between all Mini OEM bars and their 19mm & 25mm Hollow bars)

 

MP1.6T brought up a great point, thanks for clarifying Zephyrgtw. But as to my question, can you have the rear sway installed without an alignment?
aaron

 

Yes - rear sway can be installed with no affect on allignment

 

Thanks.
aaron

 

Had similar experience. I have a 2009 JCW. Swapped out the stock bar for the Hotchkis 19mm and have it on the mid-setting. Very satisfied with the result.

 

Nice, clear explanation.

Have a 2007 S, happy with stock sport suspension handling (with 215/50R16s on 15lb. Konigs), considering downgrading to 2011 Base with $500 sport suspension option - would it be more or less the same (same 18" rear bar, etc)?

Thanks.

 

Sport suspension is consistent across coupes as far as I know. On the roll bars that is; springs vary depending on car options and thus weight. Thus, it would still be an 18mm bar in the rear on a base/Justa. Here is realOEM diagram from last month available in 2010 showing the same--16mm base, 18mm sport: http://www.realoem.com/bmw/showparts...58&hg=33&fg=45

Thus, should feel the same, assuming similar wheels and tire fitment. Given 2011's are known as quieter--apparently w/ more sound insulation--you may have some relief from road noise at the margin. If you keep your lighter wheels, might be more noticeable on the base as far as a bit better acceleration given the lower engine power.

Realize for any wheel swap over involving TPMS (if relevant), the sensors changed w/ 2010's so that would not be interchangeable.

 

Another great answer! Thanks.