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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
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Trailer Leaf Spring Suspension
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APUBR-9 - Round Axle - 3 Inch Redline Trailer Leaf Spring Suspension
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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. Lowest 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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Redline Trailer Leaf Spring Suspension - APUBR-9

  • U-Bolt Kits
  • Axle Mounting Hardware
  • 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 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   (200 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.


There was a mix up between original estimated delivery before and after purchase. Sent an email regarding the matter, the team responded quickly and got my products out the next day.


Looks like good quality. The U-bolts are bigger than what is on the trailer and that is good!


Received an empty box with a hole in it. Contents must have fallen out somewhere and Fed Ex delivered me an empty box. Maybe use UPS to ship items.

I will have our customer service team reach out to you.
-- Etrailer Expert Jenny N - 02/19/2022


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.


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!


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!


All arrived on the date committed and was complete.


Very happy with the service ( no nonsen se)


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


Perfect fit, another quality set of parts from etrailer. Cut the old ones off. Put new ones on. No fuss.

As good or better than original, no problems at all
Chuck - 07/01/2021


I orderd u bolts and when we went to use them found the nuts that came with them was coarse threads instead of fine. We purchased the correct ones and then found they would not tighten all the way up do to threads being flattened half way up the u bolt. Had to end up using some old ones I had to complete the install of springs on trailer.

For a shorter 3 inch round axle u-bolt, we have part # CE15287GA
CE Smith Replacement U-Bolt w/ Nuts for 3" Round Axles - 1/2" Diameter - Galvanized
, which measures 6-11/16 inches long x 12 inch diameter. This u-bolt will work with u-bolt plate part # CE20003G
U-Bolt Plate for 3" Diameter Axle, 1-3/4" Wide Spring - 1/2" Bolts - Galvanized
-- Etrailer Expert Victoria B - 11/25/2019


Heavy Duty U bolt kit worked perfect for my round 3" trailer axles.


i have installed them but have never taken the trailer out of the barn


These i bolts work perfect great product. Also very pleased with the customer service


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


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.

Couldnt be happier with the mounting kit and etrailer
robert s - 04/06/2018


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


Worked great for my application. Quick shipping, pricing was best around.

Great. Just what I needed.
Alexander P - 03/28/2021


Great price and quality!


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!


Just what I needed....


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.


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.


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 - 10/08/2017

Show More Reviews

Ask the Experts about this Redline Trailer Leaf Spring Suspension

  • 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.
    view full answer...
  • 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.
    view full answer...
  • 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.
    view full answer...
    Image 1 for
  • 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.
    view full answer...
  • Recommended Slipper Spring And U-Bolt Kit For Trailer With 7,000 Lb Axle
    We have just what you are looking for. The slipper springs we offer for a 7,000 lb axle are part # SP-232275. This is a 5-leaf spring that measures 26-5/8 inches long and 2 inches wide. It is always recommended to replace both sides of the trailer suspension at the same time to make sure they wear evenly and support the trailer evenly as well. You can check out the attached photo with the dimensions noted for the leaf spring. When checking the dimension of the spring you will want to...
    view full answer...
    Image 1 for
  • How to Determine Correct U-Bolt Kit and Leaf Spring Bushing for a 6,000 Lb Trailer Axle
    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...
    view full answer...
  • 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...
    view full answer...
  • Will 2-1/2 Inch U-Bolts Fit a 6,000-Lb Hammerblow Axle On a Homebuilt Trailer
    The U-bolts on a trailer suspension are designed to attach the leaf springs to the axle of the trailer. The U-bolts will need to fit the diameter of your axle. I would recommend to measure the diameter of the axle. A 6,000-lb axle should have a diameter of 3 inches. The spindle that is attached to the axle will measure 2-1/4 inches in diameter. There is not a U-bolt available in a width of 2-1/4 inches. The Redline Replacement U-Bolt, part # 176500, is a U-bolt that is designed for 5,200-lb,...
    view full answer...
  • AL-KO 5200 lb Axle Mounting Bolt Size
    The U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/4" Long U-Bolts # APUBR-9 are 9/16 inch diameter. These hold the axle to the leaf springs. The bolts that hold the springs to the frame are also 9/16 inches and # 166081.
    view full answer...
  • Compatibility of Axle U-Bolts for the RM-2460
    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".
    view full answer...
  • U-Bolt Kit for a Trailer with 3 Inch Diameter Axles Rated for 7,000 Pounds
    Sticking with the 1/2 inch u-bolts is perfectly fine for your 7,000 pounds axles. Going to 9/16 inch wouldn't hurt either and if you decide to go that route then you will also need to replace the u-bolt plates and the nuts. For a kit that includes the u-bolts, plates, and nuts I recommend # APUBR-9. You would need 1 per axle. I have included a link to a video of this product for you.
    view full answer...
  • Recommended Replacement Leaf Springs and U-Bolts for 2005 Sierra Sport 24 Foot Toy Hauler
    For your 2005 Sierra Sport 24 foot toy hauler, you will want the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles # APUBR-9 for each axle, and then you will want the 4-Leaf Double-Eye Spring for 6,000-lb Trailer Axles - 25-1/8" Long # SP-221275. This will work well with your current EZ-Flex Equalizer.
    view full answer...
    Image 1 for Image 2 for
  • 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.
    view full answer...
  • 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.
    view full answer...
    Image 1 for
  • 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...
    view full answer...
  • Recommended U-Bolts for Weekend Warrior LE-3305 Axle Flip Project
    To convert your axle for a top mounted leaf spring I would recommend replacing the U bolts, nuts and tie plates, so your best bet would be to go with a U bolt kit. For a 2-3/8" round axle use # APUBR-1 For a 3" round axle use # APUBR-9 You don't want to actually turn the axle over, because it would have your wheel camber going the wrong way.
    view full answer...
    Image 1 for
  • Correct Replacement Leaf Springs and U-Bolts for Grand Design Imagine 2150RB
    The 2019 Grand Design Imagine 2150RB will most likely use the 4-Leaf Double-Eye Spring for 3,500-lb Trailer part # SP-212275 (25-1/8" Long) but you can take a simple measurement to confirm. Please note, old springs are longer than new ones and they should be measured unloaded. In regards to a u-bolt kit, this trailer will use a U-Bolt Kit part # APUBR-1 for 2-3/8" axles or a U-Bolt Kit part # APUBR-9 for 3" axles.
    view full answer...
  • Will the 8K Roadmaster Comfort Ride Leaf Spring Suspension Kit Work With 7K Axles
    The Roadmaster Comfort Ride Leaf Spring Suspension Kit part # RM-2460-2580 will indeed work on 7,000 lb axles. The leaf springs would just be slightly overrated for what you need but there will be no problems with compatibility. It does require that you un-bolt the u-bolts so we recommend replacing them at this time using the U-Bolt Kit part # APUBR-9.
    view full answer...
  • Can a Dexter 5,200 Lb Axle Be Replaced With a Dexter 6,000 Lb Axle
    It sounds like you are asking if you can use the Dexter Trailer Axle Beam part # 8327826 to replace the axle beam included with Dexter Trailer Axle with Electric Brakes part # 8327816-EB and reuse the braking assemblies and hubs/drums. If that is the case then yes you can as the diameter of the spindle where the bearings and grease seal ride are the same. Therefore, even though they may use a different outer bearing, the diameter for the inside of the bearing where it sits on the spindle...
    view full answer...
  • Recommended Replacement 5.2K Square 89" Trailer Axle
    I do have an option for you but we only offer round axles in the size you need, the Dexter Trailer Axle Beam part # 8327820 would be a great option. It matches the 89" spring center but you will need to cut and move the spring seats to your 72" requirement. I also recommend new seats for this as well, part # TRSS300. The axles can be flipped with a new u-bolt kit, the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-9.
    view full answer...
  • 3 inch Axle U-Bolt Kit Recommendation for Trailer Suspension
    Sounds like you are looking for a 3 inch axle u-bolt kit. For that you would need the part # APUBR-9 which comes with the U-bolts, plates, and nuts.
    view full answer...
  • Dimensions of U-Bolt Kit for Mounting 5,200-lb to 7,000-lb # APUBR
    The U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7-1/4" Long U-Bolts # APUBR-9 you asked about has overall bracket dimensions of 5-1/4 by 3-3/4 inches. The center on center hole measurements are 3-3/4 inches for your u-bolts and 2-5/8 inches between them for your leaf springs. Most double eye leaf springs will be 1-3/4 inch wide like # SP-198275 where slipper springs can be 2 inch like # SP-232275 and still work with this kit. Wider slipper springs like the 2-1/2...
    view full answer...
    Image 1 for
  • Determining Correct Replacement Axle For Bent Lippert 30817
    I may have an option for you but we do not carry Lippert axles. We do have a few different 6000lb axles that could work for your Heartland 5th Wheel Trailer but you will need to take a few measurements from your current axle to confirm the fit. You will need to know the hub face to hub face measurement, and spring seat to spring seat measurement. For example one of the 6000lb axles we offer is the Dexter Trailer Axle Beam # 7461121 has a hub face to hub face measurement of 95", and a...
    view full answer...
  • Replacement Axle Needed for Dexter Axle Mobile Home Axle
    Thank you for all of the good info! Since mobile home axles are just meant to be used once we want to focus on weight capacity and fit with your trailer frame to make sure we get something that is a good replacement. I'm guessing that when you measures the 75-1/2" width of your trailer frame that you were measuring outside to outside so the 6K Dexter Trailer Axle w/ Electric Brakes # 8327830-EB with the 74" spring-center and 89" hub-face measurements should do the trick. I do recommend...
    view full answer...
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Info for this part was:

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Video Edited:
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