So, I recently bought a set of used Rinehart 3.5" Slip-ons to replace the set I had on my '03 FLHRIC, (95" BB, S&S Cam, and SERT), because the left one had gotten worn paper thin where it slips over the Header. Anyhow, the baffles in the new set had been changed out to 2.5" from the normal 2.25" that are in mine. They sound just a bit softer and deeper then my old ones, and I'm kinda waffling back and forth as to whether or not to keep them or pull my old baffles out and put them in the new cans. Now to the question......... am I correct in understanding that changing out the baffles, even with as little as .25" difference, might/could/should cause re-tune? Part of me thinks that .25" shouldn't do squat but what the hell do I know? I do know if this new baffle set needs a tune, I will no longer be waffling about what to do......... the old baffles are going into the new cans.

Any thoughts?

 

Yes, there will be some difference given the overall volume that will pass through the pipes now, but honestly I don't think there will be enough for a complete re-tune. If you notice anything, ie. decel pop, or something like that, probably need a little tweak. You will be moving a bit more air and it will slightly change backpressure as well. Honestly, go for a ride and see if you feel any real difference in the performance of the engine, sound under load, coughing or anything else.

 

Change them out. You got nothing to lose but a little time & effort. Highly unlikely that the state of tune will need to be changed.

 

I've put a few hundred miles on them and to be honest, I didn't really notice too much of a difference in power/performance between the two, mostly just the sound. If anything, the 2.5's may seem to have a little less torque....... maybe? It doesn't take long to swap them around so I'll probably go back and forth another time changing out the whole slip-on before I make a decision on the baffles. I was just concerned if anyone thought that the extra .25" was really all that much of a difference. I know a few years back I swapped out my Rinehart 3.5's for a set of Rinehart 4's and that difference was huge! Had to do another dyno for them. Ended up putting the 3.5's back on because I didn't like the softer lower note of the 4's and had to do another dyno again. Lost some money on that experiment, lol.