Parts Needed For Reducing 7,000LB Leaf Springs On a 2021 Keystone Carbon From Flattening

Updated 09/26/2022 | Published 09/24/2022

Products Featured in This Question

U-Bolt Kit for Mounting 8,000-lb, Round Trailer Axles - 8" Long U-Bolts

(557)

$93.13

7-Leaf Double-Eye Spring for 8,000-lb Trailer Axles - 24-7/8" Long

(344)

$240.00

6-Leaf Double-Eye Spring for 7,000-lb Trailer Axles - 24-7/8" Long

(2442)

$80.52

3" Round Trailer U-Bolts (Qty 2)

(142)

$39.69

SumoSprings Trailer Helper Springs w/ Line Relocation Bracket - Single Axle - 5K to 8K - Overslung

(326)

$294.99

Question:

I have a 2021 Keyston Carbon 358 with tandem 7k lb axles and 6 leaf spring pack. They’re flattening out already and I have weighed fully loaded with everything we’d ever carry including 100 gallons of fresh water and it’s not over weight rating 13140 on trailer axles. I want to upgrade the leafs to 8k but stay with the 7k axle. However the axle diameter currently is 3” and the 8k axles are 3-1/2”. The U-bolts match these widths accordingly but I assume I need the longer length of the 3-1/2” wide Ubolt to reach the extra length of the additional leaf. Can a 3-1/3” wide u bolt be used on the 3” diameter axle safely? What other parts would I need to complete this upgrade?

asked by: Steven P

Helpful Expert Reply:

I do have a recommendation for you as switching out all your leaf springs on your 2021 Keystone Carbon 358 is a big undertaking. The SumoSprings Trailer Helper Springs # SS26MV are designed to work on 5,000lb to 8,000lb trailer axles and each set provides 900lbs or capacity at 50% compression. These springs are also progressive so they will help to absorb road shock while also providing support to your leaf springs giving a smoother ride inside your trailer to reduce the odds of damage to your belongings inside.

If you would rather change your 6-Leaf Double-Eye Spring for 7,000-lb Trailer Axles # e64SR for the 7-Leaf Double-Eye Spring for 8,000-lb Trailer Axles # DX74XR you will need to first confirm these are the correct length of 24-7/8" from eye to eye when not compressed. As this is hard to do you can also measure from the center of the leaf along the curve of the leaf spring to the center pin. This spring will have a distance of 13-3/16" for that measurement. As the 8,000-lb is only one leaf taller you will be able to use your same U-Bolts as long as they have the 3/8" thickness remaining on the threads. We do have 7" Long 3" Round Trailer U-Bolts # SP01-060 you can use for longer U-bolts. You would only need the U-Bolt Kit for Mounting 8,000-lb, Round Trailer Axles # APUBR-35 if you are changing to 8,000lb axles.

expert reply by: Bud M