EDIT: Back to your questions....as a Parts Manager at an ATV dealership and a avid 4 wheelin' fool...the best tire depends on what you wanna do...and your pocket book. Be careful though with some 27's. A lot of 2003 Grizzlys around here have been poppin' axles.

 

I am running 27'' mudmachine tri-claws on my grizzly.

 

Well, I can tell you this.....

My good friend put on a set of ITP ATR Holeshots on his Prairie 650 and they f'ing ROCK in the hard pack, rocks, hills, grass and believe it or not, the MUD.
I was VERY impressed with the mudding capability of the ATR's in the mud....cleaned out very well, and bite very hard. Unless you're strictly or heavily a mud rider, get the ATR's. You will not be disappointed....I was amazed at the bite.

 

mudlites

 

I have 27" mudbugs on my p650 and they are awesome tires for all round riding and really work well when the going gets ugly. They are also lighter then mudlites. Any of the above mentioned tires will do the job. I found the bugs to be cheaper then most of the other popular tires.

 

StrokedZ400.... i see you have a 2003 Grizzly with the 2004 vented side panels!.... is Yamaha offering these?.... I talked to them just recently and they told me they have a vented side panel kit for the 2003's .. kit # 5KM-SPKIT-01-00 ... is this the kit you got for yours?....

 

Yes they do rock... those will be my next tires...

 

27" vampires only exceeded by 28" vampires if u look at the design the vamps have a channel tha runs around the tire kinda like a aqua tread all other tires have a rib that runs around tire in the center created by the ends of the lugs... i have yet to see a tire that will hold a candle to the vampires.....thinkin from the pics i may try the new maxxis mudzillas next mean lookin tire any1 no anything about them...should i stick to my vampires?

 

My brother has the ITP 589 and it is a good choice but it is rough on the road at slow speeds. The Goodyear Mudrunner or the ITP MudLite are smooth on the road and offer almost as good performace in the mud. All three are well made quality tires.

 

I ended up getting the 27" bearclaws on c-series wheels. I had to put front rims on the back because the ones itp designed for the back stuck way too far out past the fenders. This was great for stability and power slides, but, sucked when you got hit in the back of the head with a rock or softball sized mud clod. The rims on it now still stick out about 2" past the fender, which, is way wider than the stocks.