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U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts

U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts

Item # APUBR-9
Our Price: $49.28
Trailer Leaf Spring Suspension
Shipping Weight: 7 lbs
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Mount your round, 3" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included. Great Prices for the best trailer leaf spring suspension from Redline. U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts part number APUBR-9 can be ordered online at or call 1-800-940-8924 for expert service.
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  • Reviews (272)
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  • Videos (2)
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Redline Trailer Leaf Spring Suspension - APUBR-9

  • U-Bolt Kits
  • Camper
  • Car Hauler
  • Utility Trailer
  • Round Axle - 3 Inch
  • 7-1/16 Inch Long
  • 5200 lbs - 7000 lbs
  • 9/16 Inch Diameter
  • Redline

Mount your round, 3" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included.


  • Attaches trailer axle to leaf springs
  • Includes:
    • (4) 7-1/16" Long U-bolts (176500)
    • (2) U-Bolt plates for 1-3/4" or 2" springs (117521)
    • (8) 9/16"-18 Hex nuts (916N)
  • Spring seats required for mounting axle to leaf spring sold separately


  • Axle diameter: 3"
    • Typical 5,200-lb to 7,000-lb axle
  • Spring width: 1-3/4" or 2"
  • Dimensions: see below

U-Bolt Diagram

APUBR-9 U-Bolt Kit for 5,200-lb to 7,000-lb Round Trailer Axles

Video of U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts

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

Video Transcript for Redline Round Trailer Axles U-Bolt Mounting Kit Installation

Today on our fifth wheel trailer we'll be installing the Red Line U-Bolt Kit for mounting 5,200 pound to 7,000 pound round trailer axles. This is part number APUBR-9. Here's what our kit consists of. We have the two flanges here that will go on top of our axle which will secure our u-bolts to the top and hold our axle in place to release springs. We have the necessary two, one per side and then the necessary four u-bolts, and then the eight nuts to secure it. The reason you want this is in case you ever need to replace a bent or damaged u-bolt or hanger assembly, or if you ever need to remove one a lot of the times they have a nylon lock nut on and you cannot remove the nut easily without causing damage to the threads of the u-bolt.

As you can see here ours rusted and bent and they had to be cut to be removed. If you have a situation like we did here today, this is the perfect kit for you to replace this. Now that we've gone over what's included in our u-bolt kit, we'll go ahead and show you how to install it. As you can see here we just have our axle sitting atop of our release spring here, and it's not secured. This is where the u-bolts come in play, and they'll secure our axle to release spring. We'll take our plate here, notice it's got these ridges.

These bridges need to face up. Here's our centering pin on our release spring, it goes in the center hole here on our plate. We'll drop that over, as you can see that holds it in place. I have our two u-bolts here and our four nuts. We'll start with one u-bolt, come up from the bottom, take two nuts ... We'll take our second u-bolt just like we did on the outside edge, come up and place our nuts on.

Now we use a 7/8ths socket and a ratchet and we'll snug these down. See, now that they're snug we'll torque them down. When we do our final torque we'll do it like the lug nuts on a wheel, in a star pattern, just to make sure the torque is evenly applied to your bolts. With that done we'll do the same on the other side now. That completes our installation of the Red Line U-Bolt Kit for mounting 5,200 pound to 7,000 pound round trailer axles.

Part number APUBR-9 on on our fifth wheel trailer.

Customer Satisfaction Score:

Customer Reviews

U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts - APUBR-9

Average Customer Rating:  4.8 out of 5 stars   (272 Customer Reviews)

Mount your round, 3" diameter axle to your trailer's leaf springs with this U-bolt kit. U-bolts, plates and nuts included.


Ordered a lot of parts for a dump trailer rebuild in Sept. Didn't install some of the final parts until Christmas break. THEY SENT COARSE THREAD NUTS INSTEAD OF FINE. I ruined 2 u-bolts and need all 16 fine thread nuts. I'm outside 60 days so I was told I'm on my own. I've spent $5k+ on etrailer. I'll find some place else.......

Etrailer Expert

Brooke M.


Hmmm...I dont like this either. I am going to send this to a customer service team lead to see what we can do. I am sure they will have a better solution for you! Hang tight!


I chose this particular kit mainly for the 9/16" u-bolts. I could have easily used the 1/2" kit but it was a nice upgrade and not much difference in cost. These u-bolts and plates fit my car trailer perfectly without any modifications. Everything in product description was just what it said when I received them. Shipping was faster than I expected!


Very wonderful and knowledgeable about parts and got parts ordered and paid for and received them very quickly , very happy this place is open on sundays and will use this company again!! Again thank you !!!


Ordered new leaf springs for 2020 Grand Design 303RLS. Replaced OEM 4 leaf spring with 5 leaf spring. Perfect fit.


As described


I had rusted old bolts and leaf springs, these were great replacements. No issues look great work well and fast shipping.


Customer service went above and beyond, had a problem with a bolt missing and they shipped one to me no problems.



Working Great!


The ladies at etrailer are awesome! Unbolts work on the new leaf springs , they know there products. I will buy from them for all my projects!
Thank you


Delivered as promised and installed as required.
No problems with service and the product.
Excellent company to do business with. Always glad to have etrailer available for go to supplies at lowest cost.


U-Bolts and hardware seem to be good quality. Package was delivered when promised. Very satisfied with purchase. Will be buying from E-Trailer again.


Excellent parts for the project I was working on. I installed a 1997 Chevy axle on a 1950 International box trailer. With a few “adjustments”, I made it work!


Got what i was looking for and got great input from Customer Assistance.


Arrived as advertised. I would have liked to have locking washers or any kind of washer for that matter! That would be an opportunity for improvement. Otherwise very good product.


The parts arrived quickly and were an exact fit, thank you!


U-boats were OK, and the correct length. However, the plates were soft and basically junk.
there were no washers. You should never install U bolts without washers.


Replaced the 4 leaf leaf springs on my 5th wheel with the 5 leaf leaf springs and the mounting kit, so far it seems to have solved the problem of the springs breaking. The trailer handles better then ever on the highway and the back roads. Couldn't be happier.

Robert S.


Couldnt be happier with the mounting kit and etrailer


Parts were Exactly what I ordered delivered fast will shop from this company again


After 30 years and many miles of towing, my trailer suspension finally succumbed to the ravages of Michigan roads and the salt used on them. I replaced the original single leaf spring suspension with a new multi-leaf system from and couldn't be happier with the results. The trailer tows much nicer now and with everything new and tight my tires are wearing at a much slower pace. I have since ordered a hitch coupler rebuild kit from which installed easily and is working very well. I wouldn't hesitate to recommend to anyone.


3 U-bolt kits, the hangers, rockers, etc. kit for a triple axle trailer, and 3 new sets of leaf springs went on a home-made 25' gooseneck we converted from 2 axle to 3 axle. We had no problems at all with the trailer since installation, and we've had it loaded down pretty well with logs, lumber, tractors, and equipment. Everything has held up well after several hours of service on the road and off-road. etrailer has always been great to work with, have had fast, accurate delivery, and timely updates on order status, etc. We've never had a problem, so I can't say how well Customer Service is!


The products from etrailer are great quality and received on time and have been very reliable


I bought new leaf springs and all the hardware to go with them. The only thing that was missing with this hardware was lock-washers. There were lock washers on the old springs so I thought it would be a good idea to have them on the new springs. These U bolts were thicker than the ones that I replaced so I had to get new washers at the local hardware store.


The U-bolts work fine - the 'universal' plate not so much. It's at least one steel gauge thickness less then the original Dexter. I reordred replacements for new springs then dug the original plates out of my spares stash, opened the hole a bit and am now using the Dexter's along with some washers Redline doesn't supply.


Great price and quality!



I was finally able to install these after the snow melted in Maine last spring. Very happy with them!


I finished installing my new springs on my trailer today. Every thing went together without any problem.i am very pleased with your product.


Looks to be a perfect fit, but haven't installed yet. Arrived on time and intact, will definitely check for my future trailer parts needs

Jason A.



Show More Reviews

See what our Experts say about this Redline Trailer Leaf Spring Suspension

  • Thread Length of U-Bolt Kit for Mounting 5,200-lb to 7,000-lb Round Trailer Axles
    The threaded portion on each bolt of U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-9 is going to measure 3 inches. I have attached a very helpful video that shows the measurements of the components of this kit for your reference.
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  • Material Grade and Torque Spec of the U-Bolt Kit part # APUBR-9
    The U-bolts of the U-Bolt Kit part # APUBR-9 are Grade 5. The torque specs for 9/16 diameter U-bolts like this is 65-95 ft lbs.
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  • U-Bolt Kit for 6,000 lb Axle
    We have a similar kit that will work for your 3" round axle with the U-Bolt Kit # APUBR-9. This kit comes with four 7-1/4" u-bolts, two u-bolt plates for 1-3/4" or 2" springs, and eight 9/16"-18 Hex nuts.
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  • Torque Specs for 9/16" Trailer Axle U-Bolts
    The torque specs for 9/16" diameter u-bolts like the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-9 will be a range, from 65 ft. lbs. to 95 ft. lbs. If the tie-plates start to bend inside this range that would be a stopping point.
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  • Torque Spec for U-Bolt Kit of 8k Trailer Axle
    An 8k axle u-bolt kit has 9/16 inch diameter u-bolts so the correct torque spec would be 65-95 ft lbs.
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    A 6,000 lb axle is usually going to be 3" in diameter. Therefore, for the u-bolts you can use part # APUBR-8 for 7" long or part # APUBR-9 for 7-1/4" long. You can measure your existing u-bolts or from the bottom of the axle to the top of the leaf spring pack in order to determine which length you need. You can always choose the longer option and cut away any remaining threads if necessary. Most leaf springs for 6,000 lb axles are 1-3/4" wide and will use a 9/16" bolt. If this is the case...
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  • Can a Three Leaf Spring Stack Be Used To Replace a Two Leaf Spring Stack
    Yes, you can replace a two leaf spring stack with a three leaf spring stack so long as your center to center (double eye springs only) measurement matches but please note the loaded and unloaded as well as the new and used center to center measurements will be different. There is a correlation between the numbers of leaves in a stack and the weight capacity of that stack but there are also two leaf spring stacks with the same weight capacity as three leaf spring stacks so going by the rated...
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  • Could U-Bolt Kit # APUBR-9 Be Used with Roadmaster Comfort Ride Shock Absorber
    Since I am not sure the dimensions of your current U-bolts I can only give you a picture that has the dimensions for the # APUBR-9 for you to check out and compare to what you have to see if these will fit and give you the extra length you'd need. These are 3 inch axle U-bolts though which are what the # APUBR-9 is designed to fit.
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    The holes in the top plate of the Roadmaster Comfort Ride Shock Absorbers # RM-2460 are for 9/16 inch diameter u-bolts like # APUBR-9. The system will actually utilize your current u-bolts for mounting those plates. I reached out to my contact at Roadmaster and the bolt hole size on the 3" shock plate is slightly slotted so it is 0.6" x 0.75".
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  • Dimension Of The TruRyde Spring Seat And Compatible U-Bolt Kit
    The Spring Seat for Typical 5,200-lb to 7,200-lb, Round Trailer Axles with 3" Diameter # TRSS300 measures 4" from end to end, and will work with a u-bolt kit, U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axle # APUBR-9. The U-bolts in this kit measure 3" wide, 7-1/4" long, and 9/16" in diameter.
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  • Compatibility of Roadmaster Comfort Ride System With U-Bolt Kit for 7,000 lb Axles
    The U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/16" Long U-Bolts # APUBR-9 will have u-bolts long enough to work well with your axles as well as the Roadmaster Comfort Ride Shock Absorbers for Tandem Axle Trailers - 5,200-lb to 7,000-lb Axle # RM-2460.
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  • AL-KO 5200 lb Axle Mounting Bolt Size
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  • How to Raise a 2011 Dutchmen Aerolite Trailer with Axle Flip Kit
    Yes, you can install lift blocks between the leaf spring perch/seat and leaf springs on your trailer to give you additional clearance between the top of your tire and trailer fender. However, you will also need longer u-bolts for this like the U-Bolt Kit part # APUBR-9 which is 7-1/4" long. We currently do not carry lift blocks so you will need to source these elsewhere. The other option you have which would perhaps allow you to retain more of the factory ride quality is to install taller...
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  • What is The Thickness Of The 4-Leaf Double-Eye Spring # e47SR?
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  • Determining Correct Replacement Axle For Bent Lippert 30817
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Do you have a question about this Trailer Leaf Spring Suspension?

Info for this part was:

Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Jacob T
Video Edited:
Jacob T
Employee Kathleen M
Video by:
Kathleen M
Employee Zach D
Video by:
Zach D
Employee Cole B
Installed by:
Cole B
Employee Wilson B
Updated by:
Wilson B
Employee Alexander C
Updated by:
Alexander C
Employee Brent H
Test Fit:
Brent H

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