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Discussion Starter #1 (Edited)
I started with a '13 RWD, CC short bed with stock suspension. I had the "hit a big pothole and the rear of the truck almost changes lanes" effect for years. When I started towing a travel trailer at 95K, that effect was accentuated to a "white-knuckle" degree. I put Bilstein 5100 (silver) shocks on the rear, and instantly the ride was sure, rock-solid and predictable. Fast forward to 130K, and I add Blue (1,000 lb) Sumo Springs to reduce the sag and to try to preserve the life of the the original leaf springs. With ~300 lb tongue the sag was on the order of 1.5" to maybe 2". The Sumo Springs are in constant contact with the frame, as most here have found, and that is fine. They reduced the sag to about 0.5" at ~300 lb tongue. But now I am almost back to the original ride -- bouncy almost like a pogo stick, feels like getting airborne sometimes. This is with and without the load. I understand how springs and dashpots (shocks, here) work together and I know that they have to be tuned to each other to work properly. I am just surprised that I threw it so far out of whack that I am falling almost back to the beginning from such a nicely-performing setup. I do have new KYB struts on the front with new coils (SR4201 kit) with <1K on them.

Next chance I get, I will jack the thing up and unscrew the helper spring bodies and go for a test drive to compare. I am cautious about new leaf springs from (e.g.) General Spring, since that could throw out the apparently-sensitive balance with the shocks as well.

Could it be that ~35K on the Bilstein 5100s is near the end of their life, with fairly extensive towing during that time?

Does anyone else have a similar setup?

Thanks for any insight.
 

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My stock yellow Bilstein shocks were pretty done at about 40K. The shock dampening rate is not tuned for over sprung or heavy loads. Don't think the sumos are to blame but the weight of the trailer.
 

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But now I am almost back to the original ride -- bouncy almost like a pogo stick, feels like getting airborne sometimes. This is with and without the load.
Could it be that ~35K on the Bilstein 5100s is near the end of their life, with fairly extensive towing during that time?
Possibly. Not only does the trailer add downward force on the truck when stationary, but it also pulls up on the ball when it hits a bump in the road. The shocks on the truck resist this upward movement, but I could see them having additional cycling (wear) due to heavy trailer use.

For reference, I also have blue Sumo Springs. But I also have General Springs 69-285HD leafs. I think the ride is better than stock, and that's with stock shocks. I tow a car on a flat deck or a 6x12 enclosed trailer (both around 4000lbs) a couple times a year.

Tire type and tire pressure also play a not-insignificant factor in suspension tuning and overall ride comfort.
 

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I am cautious about new leaf springs from (e.g.) General Spring, since that could throw out the apparently-sensitive balance with the shocks as well.

Could it be that ~35K on the Bilstein 5100s is near the end of their life, with fairly extensive towing during that time?

Does anyone else have a similar setup?
I just now called GeneralSpringsKC.com and inquired about the 'newer' design. His words: are that they're equivalent to what the older design provided as far as ride quality & 1.5"-2" of lift.

2005 - 2018 Nissan Frontier heavy duty rear leaf spring, 4(3/1) leaf

My words:
~ Keep in mind that if the factory leaf springs have sagged or gone to the dreaded W-shape that the amount of lift from HD replacements might appear greater in comparison.
~ I never wanted to lift my work truck at all, but replacing the leaf springs w/ HD units seemed absolutely necessary since I haul +/-600lbs of cargo & topper. Therefore, it then became necessary to lift the front for leveling purposes. I went w/ 5100s in the stock springs set at 1.5". Maybe a spacer would've been better? IDK. Regardless, 30K miles later I have zero complaints about ride quality - whether loaded or unloaded - w/ 5100s at all four corners.
 
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