What is the best (both from a price and performance standpoint) aftermarket rear anti-roll bar for an R50? What size upgrade typically works the best?

My driving experience is daily driver with no track days or autoX, but I would like to tighten up the handling some and most importantly, reduce the understeer. I am running OEM tires with stock 15" rims.

Any input would be appreciated. I am planning on upgrading early next year.

 

I like my bar from Mini Madness, I chose it over the hollow bars because it is forged:

http://www.billswebspace.com/mcs.htm#MiniCSRearSwayBar

 

Here's some quantitative information:
https://www.northamericanmotoring.co...uct/353/cat/69

I'd suggest a 19mm bar as a nice bump for an R50.

 

Yes a 19mm would probably be OK for what you do. I have a 25.5 competition bar on my base MINI, but I drive in very agressive conditions.

 

If you find a used bar from someone's Cooper S, even that will be a small upgrade to what you have (and might be free of super cheap to you). Otherwise a 19mm would be ideal for you IMO.

 

The main issue with understeer is grip at the front end. I would first suggest camber plates so you can increase the amount of negative front camber. You can get fixed camber plates or adjustable camber plates. Fixed would probably meet your needs/plans. Here is a link to camber plates at WMW.
http://www.waymotorworks.com/02-06-c...camber-plates/
After adding camber plates, if you still need to reduce understeer, then a 19mm rear sway bar should do the trick. The H-Sport (Hotchkis) or TSW bars are nice. Here is a link to sway bars at WMW.
http://www.waymotorworks.com/02-06-c...ion/sway-bars/
Also, better tires make a big difference.