I have a harsh grind on the rear (it's eating my koolstop reds hehe) and my front has a bit of tar, mainly cos the sound turns me on and pisses people off! for whoever it ws who asked what tar is, it's a waste product type thing i think they get it out of oil! and it's sticky as fook and makes your rims go HONK! little tip for putting tar on your rims, tar up your rim but be realy generous find a big hill ( i mean big) and go down it with the brake scraping at the rim, just to slow you a little bit, it melts the tar and makes a realy thin layer on the rim that doesn't hold your pad back but still gives a good grip! never use tar on the rear though!