I am planning on getting some BFG KM2s (35x12.5x17). Is there any reason NOT to have them siped at the store?

 

Nope! Not unless you are afraid of the (minor) extra cost. I got mine siped at a local Discount Tire store for the addt'l $10 a tire and am happy.

The only thing that you need to tell them is to only sipe the INSIDE lugs. The KM2's are a really different lug pattern, but it is possible to get just the inside tracks done. If you get the whole tire siped, this will lead to chunking and flying rubber on the highways, thus, destroying your new rubber.

 

dont they come siped...

 

Yes there is a downside. With siping, your tire has a greater chance of shredding when offroad since there are more places the tire can be ripped off from with the new suping. Generally this isn't a huge problem, just might notice some missing smaller chunks of the tire if you offroad hard enough.

I think the benefit outweighs that downside though. The only other downside I can see is cost.

 

IF you get too close to the outside edge, you will certainly get chunking.

 

On my last visit to Discount Tire I asked why they aren't pushing the tire siping anymore? They told me that some tire MFG wont warranty them after it's been done.

 

On the BFG site it says the KM2 is sipped

 

Yes. They are in fact siped as pictured in the above picture. However these are LARGE valleys in the lugs and only break up the pattern. As this helps overall and BFG made huge efforts in R & D for these new tires, I felt that for on-road traction it would be great to have them siped on a screwmachine. The resulting cuts in the treadlugs help with snow/rain while on pavement, which is what I was going for.

 

I have had my stock rubber on all kinds of ice and snow this winter. They just flat out kick butt without any need for sipes. I think it was just another marketing ploy.

 

Your stock tires are heavily sipped from the factory. Go look at them and then compare to any mud tire out there.

Siping makes a big difference in the snow and ice on road.