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Redline

1-1/2" Square Trailer U-Bolts (Qty 2)

Part Number: SP01-120

705 Reviews | 16 Questions

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$22.17

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Comprehensive Review: 1-1/2" Square Trailer U-Bolts (Qty 2)

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Great Prices for the best trailer suspension parts from Redline. 1-1/2" Square Trailer U-Bolts (Qty 2) part number SP01-120 can be ordered online at etrailer.com or call 1-800-940-8924 for expert service.

Redline Trailer Suspension Parts - SP01-120

Square Trailer U-Bolt

Width: 1-1/2"
Diameter: 1/2"
Length: 5"
- Threaded portion measures 2"
For 3,500-lb axles only
Includes Lock Nuts

071090 Redline Square Trailer U-Bolts with Nuts and Washers

Video of 1-1/2" Square Trailer U-Bolts (Qty 2)

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Demo Redline Trailer Suspension SP01 120

Comprehensive Review: 1-1/2" Square Trailer U-Bolts (Qty 2)

Video Transcript for Comprehensive Review: 1-1/2" Square Trailer U-Bolts (Qty 2)

Today we'll be reviewing part number SP01-120. This is Red Line's 1 1/2 inch Square Trailer U-bolts. You're going to get two U-Bolts and you're going to get four nuts. The width of the U-bolts. We're measuring the distance between the two bolt posts. Is going to measure an inch and a half.

Each bolt is going to give us a diameter of a half inch. The length that we have from the bottom of the cross member to the bottom of the mounting post or the bolt post is going to be 5 inches. The threaded portion going to measure right at 2 inches. This is for 3500 pound axles 00:43 only. Again, you're going to get two U-bolts, measure a half inch in diameter, and you're going to get four nuts.

That's going to do it for our review of part number SP01-120. This is Red Line's 1 1/2 inch Square Trailer U-bolts. .

Customer Satisfaction Score:

97% were satisfied with this product

3% of customers were not satisfied

Product did not meet expectations
Wrong item was ordered
Did not arrive in time

3% of customers were not satisfied

Product did not meet expectations
Wrong item was ordered
Did not arrive in time

4.8

705 reviews

5 Stars		(605)
4 Stars		(66)
3 Stars		(19)
2 Stars		(5)
1 Star		(10)

by: Kurt 08/12/2025

Worked for upgrading the leaf springs on my boat trailer to 3,500lbs. Needed longer bolts. Standard size was long enough since the new spring have more plates.

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by: Joshua 05/31/2025

Strong hardware and good quality of hardware.

Joshua One Year Later

6/3/2026

Good travels straight down road better balanced than oem design in 1978

by: Doug 02/19/2025

My brother could't find correct size U bolts anywhere. I easily found em for him and received them from etrailer in no time. He said they fit perfectly and work great!

Doug One Year Later

2/20/2026

Fantastic, no issues at all!

by: Shawn 03/26/2026

Looked high and low for this exact U bolt for my trailer. Not a very common size. ETrailer was one of the only places I could find it. Quickly shipped. Worked perfect.

by: Richard 06/07/2026

They seem great, right fit, have yet to install them, waiting on spring seats.

by: Kenneth 05/03/2019

I purchased these U bolts to upgrade the suspension on my trailer. I would get a a lot of trailer sway when I was towing my jet ski trailer. I bought the trailer used and never really looked at the springs. Unfortunately for me, There was nothing but one U bolt strapped diagonally across the spring. I'm no suspension expert but I knew this could NOT be safe. I did extensive research on trailer suspension. It was difficult to find parts for a 11/2 inch square axle. It was until I came across etrailer webpage. They had everything I required to upgrade and make my trailer safe to operate on the road. It was actually criminal what the person did to attach the original spring. I am greatful nothing ever happened while towing. Now with the new parts installed, I feel a lot better and my trailer does not sway anymore.

I will definitely purchase my trailer needs from etrailer from now on. The pictures and videos make finding what I needed so much easier. The complete transaction from order to delivery was extremely efficient and the customer service is absolutely outstanding.

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by: Bird Dog 07/15/2023

I'm working on a 12 ft long 1957 Corvette trailer. Easy install, and perfect fit. I dropped the axle to gain 3".

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Bird D. One Year Later

7/16/2024

Still working out just fine.

by: randy b. 02/18/2014

I purchased the 3000# axle springs and all mounting hardware to replace the old ones on my 1963 travel trailer. My trailer no longer leans to the left and goes down the road better than new. I should have done it many year ago. I received my package on time and installation was easy and fit perfect. Thanks Bridget

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by: Weston 06/26/2020

These U-Bolts were exactly what I needed to replace the 1 1/2" wide ones on my 1966 Silver Streak travel trailer. When I started this project I had no idea how hard parts were going to be to find. When I brought the original U-Bolts in to my local (Anchorage, AK) trailer supply place and also a custom spring shop they all looked at them like they had dropped in from outer space. etrailer had exactly what I needed to get our vintage trailer back on the road. This will be my first stop the next time I need parts for my not so standard trailer. Thanks etrailer.com!

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by: Snerd 09/23/2025

Held one star because they were covered with grease. Made a mess and couldn't paint without a bunch of cleanup.

Mike L.

9/23/2025

Since the U-bolt has a raw steel finish, the coating of grease is necessary to prevent the bolt from corroding. It's kind of unavoidable.

by: Wendell 07/13/2026 One Year Later

The U-bolts worked as advertised.

by: John 04/26/2020

Excellent product, bolted right on, great fit. Several orders through etrailer.com have yet to be disappointed

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by: Bobby 05/31/2026

Perfect fit and speedy delivery, thank you!

by: Dale Hobbs 07/31/2014

I was very impressed with the quality of these square U bolts. The bends were smooth with no stress cracking. The legs of the bolts were parallel and the nuts were a very high quality.

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by: Michael M. 05/09/2018

Perfect fit. Everything went together very smoothly.

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Michael M. One Year Later

5/10/2019

great, no problems with about 1000 miles on the new parts now.

by: Armando 10/22/2025

Just what I needed thank you sara and alexis lol awesome customer service will highly recommend your company to others

by: Al from Maine 07/16/2013

I ordered these bolts to use on my '63 Shasta (Canned-Ham ) Compact camper. The old girl had developed a squat worse than factory and that sat low. I removed the axle and springs and moved the axle below the springs and added a new plate with a tab to mount shocks that this trailer never had. The ubolts arrived in about 1 week and worked perfectly. The camper is a joy to tow now.

Don M.

8/11/2014

Al, how did you deal with the nub on the bottom of the spring stack? I have 1 1962 Compact.

8/13/2014

There is a square plate top and bottom .There is a hole I drilled in one for the rivet that hold the springs together.

by: Robert 03/08/2018

These U-bolts were hard to find any where else. As always, etrailer came thru. The U-bolts went perfect with the plate that I also ordered from etrailer. The part went on with ease on my old Gamefisher trailer. Road tested it today and its holding good and no problems. Everything that I have ordered from etrailer has a very good price and great inventory that no one can match.

Robert One Year Later

3/8/2019

Its been a year since I put this on my trailer and its working great. No problems at all. Thanks etrailer for having hard to find parts and great service.

by: Roller trailer sales 07/21/2025

A very hard to find part, locally. The price was good, shipping was reasonable, and delivery was fast

by: Joe 06/01/2025

These worked out well for me, but were very close to being too long with 3500# springs. They could stand to be a shade shorter. If they had been any longer at all I'd have to use washers.

by: Shawn 10/21/2016 One Year Later

Well I can't believe it's really been a year since I purchased all the parts from Etrailer to rebuild my jon boat trailer. I bought this tilt trailer on craigslist and well let's just say needed some MAJOR TLC. From the roller brackets, fenders, tires/wheels, hitch coupler, winch, etc.. All the parts have held up extremely well and I am VERY happy with not only the quality of the parts but the customer service as well. This is my "GOTO" place to buy parts for all 3 of my trailers!!

by: Charles S. 04/19/2017 One Year Later

very good products and excellent customer support.

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by: Paul C. 11/20/2013

Was just barely able to use to the min thread. 1 1/2" thick axle and 4 leaf 3500lbs springs. Had to add standard Split Lock washers under nuts to get enough thread available. Torqued to 50 Ft Lbs and there was less than 1/2 of a thread available if I need to retorque. These are nice and heavy. 1/2" x20 Nuts that come with U-Bolts are Non Locking and you will need to add Lock washers and the thread should be higher up the U-Bolts like another 1/2 to 1 inch if a person uses a 3 leaf 3000lbs spring or less thickness in my opinion.

by: Josh 03/07/2025 One Year Later

Rebuilding the leaf springs on my 1975 Hale 2 horse straight load. These U-bolts were what I needed. Very happy.

by: John 05/24/2025

Replaced my old U bolts perfectly. Went over the 1 1/2" axle and through the holes in the plate with no stretching or cussing. Highly recommended.

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See what our Experts say about this Redline Trailer Suspension Parts

Do you have a question about this Trailer Suspension Part?

Recommended U-Bolts And Plate For A 1-1/2" Wide Square Axle
Hey Roy, The only U-bolt kit we currently only offer for 1-1/2" square axles is part # CE23102, which only has a 3-3/8" length so it likely wouldn't be the best option for you. Instead you'll want to order the 1-1/2" Square Trailer U-Bolts # SP01-120 and two of the U-Bolt Plate # 115983 to mount your axle to the leaf springs # SP-210275.
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Availability of Stainless Steel U-Bolts for 1-1/2" Square Axle
The # SP01-120 with the raw finish is the only option we carry for a 1-1/2" square axle. I was able to find some searching the internet for "1-1/2" square axle stainless steel U-bolt" so I would give that a try.
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What U-Bolt Plate Goes With The SP01-120 1-1/2" Square Trailer U-Bolts?
Hello Damian, thanks for reaching out. We do offer a U-Bolt Plate that will work with the # SP01-120 1-1/2" Square Trailer U-Bolts, but the # CE20023G would not be correct. Instead you will need the following: - U-Bolt Plate for 1-1/2" Square Trailer Axles with 1-3/4" Wide Springs # 115983
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Are there Bolt-On Hangers for Trailer Leaf Spring Suspension
We do have a couple of bolt-on spring hangers # CE14017G and # CE14016G but they are designed for slipper springs and not double-eye springs like # e77SR. Its not likely that professional welder would charge that much. You might be able to find one locally via an iron workers union near you. For u-bolts for your 1-1/2 inch square axle you can use # SP01-120 for 2 u-bolts and 4 nuts. For a u-bolt plate you can use # 115983. For a hanger kit you could use # APS1. Now what you could do is...
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Can Round U-Bolts Be Used On a Square Axle Tube?
You need to use square U-Bolts with having a square axle tube. Trying to use round U-Bolts you risk damaging both the bolts and the axle as it creates pressure points rather than distributing the load across the surface. We have a few different size bolts you can see in the list below. 1-1/2" U-Bolts # SP01-120 1-3/4" U-Bolt # 175130 2" U-Bolts # SP01-160
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Is 1-1/2 Square Trailer U-Bolts # SP01-120 Galvanized
The 1-1/2" Square Trailer U-Bolts # SP01-120 is not galvanized and we don't have any in this size that are.
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Will 1-3/4 Inch Wide Leaf Springs Fit a U-Bolt Plate for a 1-1/2 Inch Wide Square Axle
Regardless of the axle diameter, generally most modern double-eye springs are 1-3/4 inches wide. U-bolt plate # 115983 works with u-bolts # SP01-120 which have a 1-1/2 inch width to fit around the axle. The u-bolt plate will set below the the leaf spring stack, the u-bolts will go around the axle and through the u-bolt plate and then bolted on. Take a look at the FAQ on double-eye suspension I have linked for you.
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Torque Specs for Nuts that Come with 1-1/2" Square Trailer U-Bolts # SP01-120
Yes, my contact at Redline said the nuts that come with the 1-1/2" Square Trailer U-Bolts # SP01-120 should be torqued anywhere between 45-75 ft-lbs.
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Availability of U-Bolt that Fits 1-1/2 inch Square Axle
The closest option we have is the part # SP01-120 which is U-bolt that is 1-1/2 inches wide, has a diameter of 1/2 inch, and has a length of 5 inches.
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Length of U-Bolts Needed for Trailer Suspension and a 1-1/2 Inch Square Axle
The typical length of u-bolts for 1-1/2 inch square axles is 5 inches such as # SP01-120. The u-bolt length should not be any different whether the axle is above or below the leaf spring stack unless you go to leaf springs that are taller (more leaves) than the old springs. If you are moving the axle from above the springs to below the springs then since you have a square axle there aren't any special parts needed. The plates you mentioned for each spring should be welded to the axle.
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U-Bolts And Mounting Plates For A 1-1/2" Square Trailer Axle
After a bit of research, I have determined that item # 49133 is a 1-1/2" square trailer axle. The correct u-bolts and mounting brackets for this axle are the 1-1/2" Square Trailer U-Bolts part # SP01-120 and the U-Bolt Plate for 1-1/2" Square Trailer Axles with 1-3/4" Wide Springs part # 115983. I have attached a video review for both of these products for you.
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Length of Threads on 1-1/2 Inch Square Trailer U-Bolts Part # SP01-120
I pulled one of these from our warehouse and there is 2 inches of threads on the U-Bolts.
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Replacement U-Bolt Plate and Bolts for 1-1/2 Square Axle
The smallest square axle U-bolt kit and bolt plate is for 1-1/2 inch axles. For that you would want the part # SP01-120 for the U-bolts and part # 115983 for the plate. You might double check the axle measurements, they might actually be 1-1/2 inch square axles.
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Brackets Needed to Mount Fulton Single Axle Trailer Fenders with Top and Side Steps F008584-2
You will need 4 of bracket # PF1135-BKT to mount fenders # F008584-2. Because your frame is so narrow you will need to drill a hole in each bracket to accept u-bolts that fit around your frame. We do have some 1-1/2 inch wide, 5 inch long u-bolts you could use, # SP01-120, sold as a pair. You would need 2 pair. If you don't mind drilling into the trailer frame you could also use # PF775-BKT-2 and place them wherever you can on both the fender and the trailer. You would need 2 pairs of...
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How to Determine the Correct Leaf Springs and Parts for Suspension 1956 Shasta Camper
To determine the correct parts you need to replace the springs on your trailer you will need to do some measuring and find the GVRW, Gross Vehicle Weight Rating, of your trailer. Measure the distance between the center of each eye on your trailers existing springs. The new springs you select should then match 1/2 of the trailer GVWR and the distance of the measurement you take. If you find that the measurement on your springs is 1/2 to 1 inch longer than the measurement of a spring that...
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Need Replacement Square U-Bolt for 1-1/2 Inch Axle
For a replacement U-Bolt closest to your measurements, I have the Replacement U-Bolt with Nuts, part # 1753223, which is for 1-1/2 inch wide, square axles. We also sell these U-Bolts in a pair, part # SP01-120. The Replacement U-Bolt, part # 1753223, will work great with your 1-1/2 Inch, 1800 pound capacity axle. U-Bolts do not typically carry a weight rating.
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Do you have a question about this Trailer Suspension Part?

Info for this part was:

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Expert Research:

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Video by:

Kathleen M

Installed by:

Cole B

Updated by:

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Updated by:

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