Which SumoSprings Are Best for a 2005 Toyota 4Runner Towing a 3,500 lb Casita?  

Question:

Expert Reply:

Hello Gary,

Thanks for writing in, great question.

For your setup, I would recommend the SumoSprings Solo Custom Helper Springs for the Rear Axle # SS68DR.

Even though your Casita weighs around 3,500 pounds when fully loaded, your 4Runner's rear suspension is only supporting the trailer's tongue weight, not the entire trailer weight. For a trailer of that size, the tongue weight is typically around 350 to 525 pounds, assuming it's loaded properly. That's the weight the SumoSprings are designed to help support to reduce rear-end squat and improve ride quality.

I think the # SS68DR is the better choice because it provides additional rear support without being overly stiff for everyday driving. Since you only tow your Casita a few weeks each year but also travel a mile and a half on a bumpy dirt road to get home, these SumoSprings will help reduce sag while towing and provide additional suspension support on rough roads without making the unloaded ride unnecessarily firm. Your Bilstein rear shocks will continue to control suspension movement, while the SumoSprings help carry the additional load.

I've also attached a photo showing what the SumoSprings look like once they're installed. You'll notice there's a small gap between the SumoSpring and the contact point. That's completely normal. They aren't intended to be under constant compression. Instead, they make contact as the suspension compresses under load, providing additional support only when it's needed while still allowing for a comfortable ride when you're not towing.

Getting things geared up for the next great adventure, where are you headed to this time?

expert reply by: Kate F

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SumoSpring Installed
(click to enlarge)

Gary P.

7/6/2026

Thanks so much for your help Kate! I will be ordering the SumoSprings very soon ! Gary P

Kate F.

7/6/2026

@GaryP My pleasure Gary =)

Matt G.

7/7/2026

@GaryP, Just wanted to add my quick 2 cents here since we have a very similar setup i.e. 4Runner 4x4 with a similar trailer weight. I went with the very product Kate recommended and they were great for supporting cornering, etc. but they did not eliminate the squat that I experienced. I ended up putting in a set of coil spring airbags in the back and that did the trick. When I hook up I simply inflate until level and I'm good to go. Your mileage may vary so take my experience with a grain of salt but good luck in whatever you end up with!

Kate F.

7/7/2026

@MattG Thanks for the response Matt.

Jeff B.

7/7/2026

Gary, I have a 2016 SR5. We have a 21 Independence. I installed blue Sumo on the 4Runner, couldnt be happier, towing the Casita or not.

Kate F.

7/7/2026

@JeffB Thanks for the response Jeff. I am glad the Sumos fixed your issue =)

David

7/7/2026

Just throwing it out there since I couldn't find much on this when I was ordering, the sumospring is designed to engage for that amount of load with a vehicle at OE ride height. If you have a lift the springs won't engage or give you as much suspension stiffness as designed. E-Trailer makes rubber "pucks" of varying thicknesses that can help maintain the engagement with a lifted vehicle.

Kate F.

7/8/2026

@David Thanks for the response David. Yes, if you have any kind of lift please let me know Gary.

Hiroshi

7/8/2026

I installed the Sumo blue ones on my GX550 because there are no air suspension bags on the market for his rig. I tow a 18ft Oliver travel trailer and the blue ones work the best because it keeps the back from too firm of a ride. I did have to cut about one inch off the bottom of the Sumo since I wanted a little clearence between it the the axle when I wasn't carrying a load. With the trailer hooked up and back of the suv loaded, it worked out great. I really liked the ride. No sage.

Kate F.

7/8/2026

@Hiroshi Thanks for the response Hiroshi. Great idea to cut that 1' off the bottom, although I am sure that does void the warranty. These things are built to last anyway =)