Recommended U-Bolt Kit for 3-1/2" Diameter Axles

Published 05/04/2026

Products Featured in This Question

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

(550)

$83.88

Question:

I was looking at your 8K axle u bolt kits. It doesnt specify what grade steel the u bolts are. What grade should I be looking for? Thanks.

asked by: Ken G

Expert Reply:

Hey Ken, welcome back! The 3-1/2" Diameter Axle U-Bolt Kit item # APUBR-35 are made of grade 8 steel and that's exactly what you want. This kit includes four U-bolts, two plates, and 8 bolts. You'll need one kit per axle.

The U-Bolts included with item # APUBR-35 measure 8" long and are 9/16" in diameter. They're designed to work with 3-1/2" diameter axles. You'll want to torque them to 65-95 ft lbs when installing.

What kind of trailer do you have and why are you replacing the U-bolts?

You can add this information, along with any other questions you have, where it says Add Comment.

expert reply by: Jerred H

APUBR-35
(click to enlarge)

Ken G.

5/4/2026

I am replacing my axles because they has short spindles on them and I have to have #42 spindles for disc brakes. Since I am putting on new axles, I want new U bolts.

Jerred H.

5/4/2026

@KenG That makes complete sense! It's highly recommended to replace your U-bolts when you replace your axle. So long as your 8k axle is 3-1/2" in diameter the item # APUBR-35 kit is exactly what you need.

Ken G.

5/4/2026

One more dumb question. If the plates are less than a year and a half, can I just get the U bolts? Thanks.

Jerred H.

5/4/2026

@KenG You sure can. They're the Replacement U-Bolt w/Nuts item # 11-65.