well I have a set of Volk 16" sitting in my closet with 215/40 tires. Is it too small for the mini?

 

You be the judge. Click on this website then put in your stock tire size and the new tire size. It will compare and contrast the two sizes and give you things such as speedo correction and revs per mile, etc.

http://www.1010tires.com/TireSizeCal...?action=submit

 

No.

215/45-16 tires are more common for track or autocross with a MINI.

215/40-16 has a max load of 1047 pounds which is very low for use with a MINI. It might work for the track with only one person in the car. It's usually mounted on rims 7-8.5" wide and the outer tire diameter is a small 22.6".
Overall the tire size is OK. I wouldn't use it much for street driving. Ground clearance will be low- careful with the speed bumps and potholes.

 

It really depends on the brand....A 215/40 16 Hoosier As03 is the same size as their 205/45 As04 so you really need to measure for yourself to see if it's going to work. That said, I wouldn't be too concerned about it. They're going to be a little shorter then the stock tires but a lot of people run 205/50 15's on their MINI's and love them. Sometimes you just have to experiment.

 

I run the 215/40/16 V710's for autocross. They look a little short, but they really work well. I think for the street a 215/45/16 would be a better choice especially if you have expensive aftermarket wheels. As far as the rim width goes, I've got the 215/40's on the stock 16X6.5's. My tire store said it took three people to mount them. They weren't real happy, especially when I told them that I'd be back in a few months to "flip" them.