Should I Go With SumoSprings or Timbren for 2023 Grand Design Reflection 320MKS

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Question:

I have a 2023 grand design reflection 320 mks fifth wheel and wanted to add sumo springs on top of leaf springs or even timbres Which one will I need to order for 7 k axles. What’s your recommendations. Thank you

asked by: Jeff Q

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Expert Reply:

Hey Jeff!

For your 2023 Grand Design Reflection 320MKS with 7,000 lb axles, both the SumoSprings and Timbren SES are good options since they work with your existing leaf spring suspension rather than replacing it.

My recommendation would be the SumoSprings because their progressive design does a great job of absorbing road shock, reducing bounce and sway, and adding support without making the ride unnecessarily harsh. For your 7,000 lb axles, you’ll want the SumoSprings rated for 5,000-8,000 lb axles. If your leaf springs are overslung, meaning they sit above the axles, you’ll need the SumoSprings SumoSprings Trailer Helper Springs w/ Line Relocation Bracket # SS26MV. If they’re underslung, with the leaf springs below the axles, you’ll need SumoSprings Trailer Helper Springs w/ Line Relocation Bracket # SS33HR.

Are your leaf springs mounted above or below your axles, and what are you mainly trying to improve

expert reply by: Jerry B

0

Jeff Q.

8/12/2026

Above axle and want g to improve the ride of trailer. Just finished a 5400 mile trip and everyday there was some broke from the roads because of the ride of trailer. I’ve read enough in grand design owners group that people are saying it helps with the chucking you get. Are timbrens more reliable since there more of a commercial quality? Thank you jeff

Jerry B.

8/12/2026

@JeffQ That makes perfect sense. Upgrading the suspension will help prevent both chucking and the broken accessories inside your trailer. I wouldn't say the Timbren are better than the SumoSprings, but they are comparable and give the SumoSprings a good fight. The Timbren are made of rubber, while the SumoSprings are made of microcellular urethane, which gives the SumoSprings a softer, more progressive feel. In your situation, that softer compression is why I prefer the SumoSprings. When the trailer hits a bump, they’ll compress more progressively to absorb the impact and help smooth out the ride rather than transferring as much of that jolt through the trailer.

Jim

8/14/2026

@Jeffq Jeff, I put lots of miles on my Grand Design 337RLS to the point of breaking my leaf springs somewhere in New Mexico about four or five years ago. E-trailer came to the rescue and shipped heavier duty springs along with a shackle upgrade. Fast forward to last year…I noticed the newer heavy duty springs were starting to sag a little bit so I added the Sumos. They worked very well in stability and control but I’m not sure about smooth ride. They do prevent over stress of the leaf springs in my opinion but you will still break stuff on most every trip if your on the road as much as we are. Nothing works. If you intend to keep that trailer until she comes all the way apart I would look into adding completely new suspension called Torsion. Look it up. I sold my fifth and bought a motorhome…now I am breaking stuff on the motorhome. Especially drawers. Anyway get big oversized 14 ply tires and run them at 80 instead of 115 and get the heavy springs and shackles and add Sumos and that will get you a torpedo straight and stable fifth wheel. You will still break stuff though. Cheers.

John M.

8/13/2026

I installed the Sumo-Springs on a 2022 Grand Design and they fit perfectly. They seem to help, I have not put a lot of miles on the camper (probably less than 2,000) but them seem to be working just fine.

Jerry B.

8/14/2026

@JohnM That's great! As time goes on, you'll see that they're going to hold up really well and keep your vehicle in good condition. Any trips coming up with your Grand Design?

John M.

8/14/2026

Taking a trip from Richmond Va to Outer banks NC soon. About 200 miles one way. Love the set up, 33' - 5th wheel pulling with an F250 Diesel. Best pulling combo I have had in over 30 years of camping.

Jerry B.

8/14/2026

@JohnM Nice! My family just got back from a trip to Williamsburg and the kids had us stop in Richmond.

Jd

8/13/2026

We have the Sumo Springs on our triple axle Momentum and they have made a noticeable difference. They are easy to install. I just recommend checking the bolts after a hundred miles or so as mine have need to be tightened. Highly recommend them.

Jerry B.

8/14/2026

@Jd Thanks for your feedback and advice! After tightening, was everything good? Did that affect your ride at all?

John

8/13/2026

Hello Jeff, I have a grand design momentum 2020 376 42' triangle. I bought 6 springs. One for each axle. Was very easy to install. Better to take each wheel off easier access. We took the rv through the mountains of Virginia and Tennessee. Our RV TRIP WIZARD GPS went out on us so my truck map program took over. It took us through some sketchy roads. Should of stopped and repaired gps but didn't that RV never leaned the whole way. I thought there is no way I could make it. Used driving skills. Wide turns, never had a problem. Would recommend these in a second. Safe travels..

Jerry B.

8/14/2026

@John Thanks for the real-world experience! I think it's awesome it was able to hold up and keep you moving steady in a tough spot. How was the trip? I actually just recently came back to Missouri from Virginia through Tennessee, so I bet we took the same path at some point.

Pat G.

8/13/2026

I installed Summo springs on my tri-axle Raptor after experiencing a lot of bounce at highway speeds on a trip to Yellowstone in the sumner after bouncing through a couple of their famous frost heaves and finding things on the floor upon arrival. I could not have made a better decision, no more or very little bouncing and I have been down the same roads. Rough bridge approaches used to cause me to brake way down, not an issue any longer. A little side note, it also handles a lot better in side winds. You can’t go wrong with this upgrade!. Safe travels.

Jerry B.

8/14/2026

@PatG Thanks for the info! That Raptor sounds well traveled! I'm looking forward to going to Yellowstone hopefully next summer. Did you get to camp in the park or just pass through?

Pat

8/14/2026

@JerryB No the toy Haulers are mostly too long for the national parks, some State parks are ok. My Raptor is pretty close to 43’ with a crew cab truck. We stayed outside of Jackson Hole both times we’ve been up there. Can’t remember the campground my bride/navigator handled the reservations. It was perfect with equal access to Teton, Yellowstone and Jackson Hole. A little hint, plan on minimum a week, two if you can. Lots to see and experience up there.

Jerry B.

8/17/2026

@Pat That's perfect, I appreciate the advice!

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Should I Go With SumoSprings or Timbren for 2023 Grand Design Reflection 320MKS

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