I have finally decided on Rineharts. Now next decision is 3.5 or 4. Putting on 2011 ultra with stock 96.

 

Same performance "slightly" difference sound, different look. The 4" pipes look bigger on the bike (if you like that) and they do sound deeper "to me" but sound is subjective and you will get different opinions. If those two things don't matter to you then buy whichever set you can find cheaper.

 

I have the 4" and my buddy has the 3.5" and his sound better. I agree the 4" sound deeper, but the 3.5" sound quite a bit louder. If I had to do it all over again then I would go with the 3.5".

 

I've had both on the same bike in fact....My opinion is go for the 4s. Yes, the 3.5s are a little louder but they also sound a bit more crackly to my ears. I bought the 4s, which aren't quiet by any means, and the high flow, 2.5 inch baffles and the sound is flat out awesome! The 4 inch look is also a plus!

 

X2!! Well said Andy!!

 

I had both on the same bike and sold the 4" and kept the 3.5". Sound is subjective for sure but my bike ran better with the 3.5".

 

In terms of engine balancing & power, the smaller diameter pipe will allow the engine to scavenge more which will benefit you for power & the engine for better breathing!
Hatch.

 

i bought the 3.5s because i don't like the 4in look.. passed a bike the other day with the 4s and couldn't tell any difference in volume, though there may be some.. my advice pick which one you think looks better and pull the trigger.. because neither will run like a 2 into 1

 

I have the 4" & love the looks & sound. What hatchetman says is true though. Doc @ Docs performance Tuning told me that my mufflers hurt my tune a lil cause they are too free flowing. Steve Cole with TTS let me in on a lil trick to restrict the left side though so the O2 sensors can be happy. If you are going to buy either check out www.kostomeemporium.com ,, they can be bought for $500.00 there. I couldnt find them any cheaper.

 

I can't add much in the way of performance testing, but I put 4" ones on my SG and love the looks and sound.