ST4s have 45MM header pipes. ST2 and ST3 models have smaller headers (42MM maybe?).

Just a note. When we say pipes are Ti or Carbon, normally it is referring to the sleeves on the silencer portion. The baffles and connector pipes will normally be stainless steel. The pic you show is stainless, just like the bike's header pipe.

 

pix

hope this clears up what they look like.

 

The picture shows a standard slip joint that is used on all the OEM ST pipes and by some aftermarket makers. I had a carbon DP set early on that had the same joints, but my current FBF pipes have a single wall that measures 45MM for the ST4s. That inner pipe in your pic determines the size. I can roughly convert your tape measure placement to about 42MM, which makes them for an ST2 or ST3. The outer pipe would convert to about 45, so sure, if you cold cut the inner pipe out, you could probably make them work. Might be better to sell them to an ST2 or ST3 owner and then source the correct pipes for your bike though.

 

Just to put into perspective on where to measure, here's a shot of the DP carbon pipes I used to have. They do have the same slip joint you show, but you can see the outer pipe is slotted because these had clamps as well as the normal spring to hold them in place at the cross-over. That inner pipe is the actual exhaust and it measured 45MM to fit my ST4s.

All OEM, and some aftermarket, pipes have that same double-wall slip joint. Some aftermarket pipes are a single wall, like my current FBF pipes.

The pipes in your picture are for an ST2 or ST3 as the inner pipe looks to measure 42MM by your tape measure.

 

Something bizarre is going on with the forum! I posted a picture of my 45MM pipes with a similar slip joint and it wound up in the Supersport forum! I can't delete it from there or repost it here....

:abduct: