So, i just bought an 06 r53 with 73k, 1owner, manual. what should i most definitely replace other then all fluids right away. ie: water pump, belt tensioner, bushings. this is going to be mostly a street car but, will be doing 3-4 track days a year VIR and Road Atlanta.

 

Nice find! In addition to fluids, I’d also replace filters (air filter and cabin filter) then start looking for what actually needs replacement. You’ve got the usual suspects listed. I’d also look at the power steering lines for leaks, and condition of the serpentine belt. Your in the mileage where a lot of items need replacement (or will soon) so it depends a bit on what’s been done already.

 

Some ideas for you-
If there is a MINI club in your area find out if they have meetings and seek out any owners of R53 that have taken them to the track.

While a MINI does fine at the track there are some things that will make a huge difference with wear and tear on your car. Brake fluid needs to be checked and replaced before track use and afterward. You can even use track brake fluid that allows for a higher boiling temperature. Examine the brake rotors and pads and make sure they are in good shape. OEM brake pads dust a lot and don't stop that well. Standard OEM rotors are OK, nothing special. I use cryo treated plain solid rotors for more durability and stay away from fancy drilled rotors that only look good, slotted rotors are OK as well. Brake pads come in many different types but look for one that gives a little better bite and may tolerate higher temperatures for track use but are still friendly for street use. A true track brake pad is meant to work with higher brake temperatures so it doesn't stop well at cold street use temperatures and it dusts heavier.

For an older MINI I would check all suspension mounts and bushings, many rubber OEM bushings may be worn out and bad, you can replace them with OEM parts or you can use polyurethane replacement parts but the stiffer polyurethane will be stiff riding and rattle your interior revealing many noises common on an older car. Stiff bushings also allow less play so slightly better handling. After about 8-10 years I had to replace all mounts and bushings, I have a 2003 R53 with 135,000 now doing well and ready for track use.

Since you have a reduction pulley the serpentine belt needs to be watched and replaced about every two years with a smaller than OEM belt. The smaller pulley puts more stress on the belt which has been known to tear apart or wear faster. I replace routinely before much sign of any trouble. If you do this yourself you need a special pulley tensioner tool that allows you to put slack on the tensioner and remove the belt easily.

Air filter can be cleaned or replaced. Check if you have an adjustable rear sway bar installed and which setting it is on, middle or softer setting is a good place to start and test with your track tires for how it feels. The MINI naturally will understeer, a stiffer rear bar allows you to reduce understeer by increasing oversteer however you don't want the stiffest setting and encourage too much oversteer. Best setup is controllable oversteer and minimal understeer. No need to change the front swaybar. Additional suspension stiffening like front tower brace is OK but not required. In my opinion after years of use your MINI may have more flex so any stiffening of the chassis is a good thing. I run both under chassis cross bracing and front tower brace but I have rallycrossed my MINI.

Racing harnesses are a good investment, I use Schroth four point quick fit harnesses in both front seats, they are easy to clip in for track events and don't change things for street driving with OEM belts.

Find out the requirements for helmet ratings for the track you are planning to go to, SNELL M vs SA ratings are common, M for motorcycle is OK for autocross and basic track, SA is fire rated for competition track. Helmets are about $150 to $600, open and closed face and vary on weight, lighter carbon fiber will cost more.