How to Upgrade Speed Rating for Ultra-Tow Aluminum Utility Trailer
Updated 12/22/2025 | Published 10/15/2024
Question:
I’m going to build a tear kit and need to purchase a trailer to mount it on. I’m currently looking at the Ultra-Tow 5ft. x 8ft. Aluminum Utility Trailer sold by Northern Tools. This trailer is only rated for 45 mph which isn’t going to be adequate so I’m looking for sensible ways to upgrade the speed rating to around 70mph. I know that I can upgrade the tires to am M rated tire. As I recall, I could also go with a 13” wheel as opposed to the stock 12” wheel but may have to customize the fenders. Finally, I’ve read on your site both that radial and bias ply tires are best. Which is it? Beyond the tires, do I need to do anything on the axle or wheel bearings? I appreciate your thoughts.
asked by: Raymond B
Expert Reply:
Hi Raymond; swapping out the tires for a higher speed rating only works if the tires are the limiting factor. Your basic trailer tires have a speed rating of 65 mph so I'm sure there is another reason for the 45 mph limit. There wouldn't be a need for a larger 13" tire since you could use something like the Kenda Karrier S-Trail ST145/R12 # AM10130 with that M speed rating for 81 mph. Radial tires are better in almost every way so I would definitely choose them over Bias ply.
What you need to do is reach out to the trailer manufacturer to find out where the speed rating comes from. Trailers like these may have that speed rating based on the structure and design which you can't do a whole lot about. If the frame is limited to 45 mph you will need to find a different trailer without these limitations.
Product Page this Question was Asked From
Kenda Karrier S-Trail ST145/R12 Radial Trailer Tire - Load Range D
- Trailer Tires and Wheels
- Tire Only
- Radial Tire
- Load Range D
- 145/80-12
- 12 Inch
- M - 81 mph
- Kenda
more information >
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Robin H.
12/22/2025
Hi Raymond, were you able to check with the trailer manufacturer about the reason for that 45‑mph limit on the Ultra‑Tow trailer? Knowing what you found could really help others trying to upgrade their setups safely. Your update could make it easier for the next person building a teardrop kit like yours.