Grit dog wrote:
Started doing it (siping) on mud tires because they don’t have any or few factory sipes.
But it (sipes) even helps on AT or HT treads. Same concept as snow tires.
Generally the trucks that run over the passes in the winter, I sipe the tires.
Difference is night and day on mudders and it makes them not only good in deep/loose snow, with the big open lugs but helps the lugs grip the slippery stuff as well.
On AT tires which are like good at most conditions but not the best at anything, it’s also a noticeable improvement.
On any tires, especially heavier trucks, I don’t have them siped all the way out to the edges. That serves to wear out the shoulder treads much quicker. Just the inner tread rows and maybe halfway into the outer rows.
One of the main reasons I chose the Michelin XDS2 (225/70R19.5G) drive tire was due to all the factory cut SIPES already included and designed into the tire, without having to pay to have the tire tread sliced into by a tire jockey after the fact.
The XDS2 has 700 zig zagging sipes per tire.
There are 200 treadblocks circumnavigating the tire in four rows.
The two center rows of treadblocks have 4 sipes per individual treadblock, and there are 50 treadblocks per row. That's where 400 of the sipes can be found.
The two outer rows of treadblocks have 3 sipes per treadblock, and being outer rows, the three sipes are not cut all the way out to the edges, but rather only extend about half way across the outer treadblocks, from inboard of the tire, such that the outermost shoulder of the outside treadbocks is solid, to provide the shoulder support that @gritdog mentions in the quote above.
The total "half way across" sipes of the two outer rows of treadblocks is 300 sipes, plus the 400 full width cut sipes of the two central rows of treadblocks, equals 700 factory cut sipes per tire.
No other 19.5" tire on the market back in 2011 had more, or even near as many, factory formed sipes in the treadblocks as the Michelin XDS2. As I look to replace these tires solely due to time (10 years) not treadwear (plenty of tread left, with Lincoln's head upside down, the treadblocks still reach his chin!), a sipe count will definitely be part of any comparison of 19.5 tires available on the market this year.