Recommended Suspension and Disc Brake Upgrade for a Tandem Trailer w/ 4,400 lbs Axles  

Question:

Expert Reply:

Hey Ken thanks for all the information! I can help you with your suspension upgrade but i have no way to add disc brakes to a 4,400 lbs axle and keep your 6 lug pattern wheels. You would need to upgrade your axle or find a 4,400 lbs idler hub with a 6 on 5-1/2 bolt pattern. You could use the Hydrastar Disc Brake Kit item # HYD24VR which is a slip-on rotor if you do find an idler hub. We only have a hub and drum assembly left for 4,400 lbs axles item # 8-407-5UC3-EZ.

As far as suspension goes. I don't have a database that shows me what springs or the size you have on your Keystone. I'll need you to jack up one side of the trailer, to take the weight off of the suspension, and measure from the center of one eye hole to the other eye hole on one of your springs. The springs stretch out after years of use and this is the most accurate way to find a replacement. I have linked a diagram below so you can have a visual aid. I would need measurement C.

For your suspension upgrade, I recommend a set of SumoSprings. These are our best option for trailer jounce springs as they do a great job of providing additional support as needed as well as helping to reduce body roll and sway. These springs are a progressive type so they will compress to absorb bounce as weight is placed upon them.

There are a couple of different options for SumoSprings on your Keystone Travel Trailer, which one works for yours will depend on the location of your axles in relation to how they are mounted on the springs. If your axles are above your leaf springs you will want the SumoSprings Trailer Helper Springs w/ Line Relocation Bracket item # TSS-106-40. These are for underslung axles. If your axles are mounted below your leaf springs you are going to need the SumoSprings item # TSS-107-40 for overslung axles. You will need one of these sets for each axle.

I have linked a review video below so you can get a walk through of these springs. If you have any additional questions feel free to reach out in the comment box below.

expert reply by: Jerred H

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Spring Measurements
(click to enlarge)

Jerred H.

10/30/2025

Hey Ken, how did things go with the suspension upgrade on your Keystone Bullet? Were you able to get the right measurements for your leaf springs and choose between the SumoSprings options? Your update could make it easier for others working on similar trailers.

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Ken S.

10/31/2025

@JerredH, Thanks Jerred, we are going into Fall and Winter here and it's time for trailer maintenance so we will do our upgrade over the next couple months.

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Jerred H.

11/1/2025

@KenS Sounds good! Let me know if you have any additional questions.

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