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Square Trailer U-Bolt
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
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
Ratings & Reviews
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.
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.
Rebuilding the leaf springs on my 1975 Hale 2 horse straight load. These U-bolts were what I needed. Very happy.
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!!
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.
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.
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.
Al
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.
A very hard to find part, locally. The price was good, shipping was reasonable, and delivery was fast
Perfect fit. Everything went together very smoothly.
Michael M.
5/10/2019
great, no problems with about 1000 miles on the new parts now.
Just what I needed thank you sara and alexis lol awesome customer service will highly recommend your company to others
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.
Excellent product, bolted right on, great fit. Several orders through etrailer.com have yet to be disappointed
Perfect fit and speedy delivery, thank you!
The U-bolts worked as advertised.
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.
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!
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
I'm working on a 12 ft long 1957 Corvette trailer. Easy install, and perfect fit. I dropped the axle to gain 3".
Bird D.
7/16/2024
Still working out just fine.
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.
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.
They seem great, right fit, have yet to install them, waiting on spring seats.
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.
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
2/20/2026
Fantastic, no issues at all!
Strong hardware and good quality of har dware.
Joshua
6/3/2026
Good travels straight down road better balanced than oem design in 1978
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Robert
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.