SOLVED: Length of Fox 4” Air Bumps for Towing w/ RPG

I have the RPG Stage 3 rear suspension with Deaver +3s and I want to use the air bumps for towing a travel trailer with a 715 lb tongue weight. The standard Fox air bumps that come with the Stage 3 kit are 2.5”. I have the 3” bump extensions for towing short distances, but I am considering the taller 4” air bumps for longer trips.

For anyone who has them, I would like to know how much longer the 4” air bump are vs the 2.5”? Are they exactly 1.5” longer or is the top part longer as well? I sent a couple emails to RPG, but I have yet to hear back from them.

For reference, here is my RPG setup with the standard 2.5” air bumps.

ok, I can see this is a very hot topic on FRF...

I was finally able to find a website which lists the length of the 2.5" and 4" Fox air bumps. In case anyone is looking for the answer in the future, the 4" bumps are 4" longer than the 2.5" bumps.

2.5" x 2.5" Fox Air Bumps = 10 3/4"
2.5" x 4.0" Fox Air Bumps = 14 3/4"

Here is a shot of my 2.5" bumps and one of the 4" extensions from RPG: (While I had them out for cleaning, I lowered them to 50 psi for towing a TT with 715 lb tongue weight)



From this picture, you can see there is only about a 1/2" of clearance when there is no weight on the back of the truck with my SD Deaver +3s. Those with Deaver +2s or stock height leafs would be riding on the air bumps w/ extensions all the time. I drove it around town and you hear an occasional banging when going over larger bumps in the road.

This also means the same length 4" bumps would have to be removed every time I arrive at a campground to avoid them bouncing off the bump plates with normal driving. I am probably going to pass on the longer ones for now. The extensions are really easy to remove (3 minutes total for both sides) and I can put them back on when I am ready to pull out.






Once I pickup the trailer and get it loaded with my WDH, I will take some pictures before and after and let you know how it rides.