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

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

Item # APUBR-8
Our Price: $39.71
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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" Long U-Bolts part number APUBR-8 can be ordered online at or call 1-636-306-4830 for expert service.
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Redline Trailer Leaf Spring Suspension - APUBR-8

  • Camper
  • Car Hauler
  • Utility Trailer
  • U-Bolt Kits
  • Round Axle - 3 Inch
  • 7 Inch Long
  • 5200 lbs - 7000 lbs
  • 1/2 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" Long U-bolts (1755892)
    • (2) U-Bolt plates for 1-3/4" or 2" springs (117521)
    • (8) 1/2"-20 Hex nuts (12N)
  • 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"
  • Thread dimensions: 2" long x 1/2"-20
  • Dimensions: see below

U-Bolt Diagram

APUBR-8 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" Long U-Bolts

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

Video Transcript for Redline Trailer Suspension - Leaf Spring Suspension - APUBR-8 Review

Today we're going to be reviewing part number APUBR-8. This is Redline's U-Bolt Kit for mounting 5,200-pound to 7,000-pound round trailer axles. It's going to attach the trailer to the leaf springs. It's going to include four 7-inch-long U-bolts. We get that measurement by measuring from the bottom of the cross member to the bottom of the U-bolt post. The threaded portion is going to measure 1 and 7/8ths of an inch.

Each bolt is going to give us a diameter of a half-inch. The distance that we have between the two posts is going to measure 3 inches. Each U-bolt is going to be identical, so they're all going to offer the same measurements. It's also going to come with two U-bolt plates for 1 and 3/4-inch or 2-inch springs. The overall dimensions of one of these plates is going to measure 5 and 3/8ths of an inch by 3 and 3/4 and again, both of those plates are going to be identical, and then it's going to come with the eight half-inch hex nuts that are needed to secure everything. Spring seats are required for mounting the axle to the leaf spring and those are going to be sold separately. This is designed to fit axle diameters of 3 inches, which is going to be your typical 5,200-pound to 7,000-pound trailer axle, with a spring width of 1 and 3/4-inch or 2-inch. That's going to do it for today's review of part number APUBR-8.

This is Redline's U-Bolt Kit for mounting 5,200-pound to 7,000-pound round trailer axles. .

Customer Satisfaction Score:

Customer Reviews

U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7" Long U-Bolts - APUBR-8

Average Customer Rating:  4.8 out of 5 stars   (275 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.


These seem to be working ok but do not appear to be designed for use with the HD upgraded Moryde greaseable shackle kit that I purchased with them . You can see in the photos that they rub and bind

I do have two recommendations for you. The first would be to make sure that the bolts are not over tightened. The locknuts should only be tight enough to limit as much movement as possible without binding anything up. The second recommendation is that Lippert makes that can be used with the Equa-Flex system. It is part # LC64FR
Lippert Tandem Axle Equa-Flex AP Kit - Wet Bolts - 3-1/8" Long Shackles
. The shackle straps are less thick at 0.212 thickness however they are longer at 3 and one quarter inches.
-- Etrailer Expert Jenny N - 04/22/2022


It was just what I needed for my project. I am converting an old surplus army trailer to a more useful utility trailer. That included changing the axel to lower the higher of the trailer. The axel I had was an old mobile home axel that I shortened. The diameter was smaller than the existing axel and the u bolts were to big. These worked perfect after I modified the mounting plates. Thanks again. I will be using you all again on my next project.


I think you screwed up. I did not receive the U bolt kit, I received Part # CT-3000-RK, Repair kit for 2" straight coupler which I did not order. I reported this upon delivery of the wrong part.

We recently sent you a new u bolt kit and were wondering if you had any feedback about the product for other shoppers? We look forward to hearing from you.
-- Etrailer Expert Jenny N - 07/21/2022


mounting kit and new springs in place and performing as expected!


Excellent product, I used it to beef up the suspension on my welding trailer. It has proven to be a great quality product. Even though local stores carry this kit, I trust a company with the word trailer in its name, and for good reason. I recommend your website to all of my welding students, so if you're ever in the mood to send parts for me to install, test, and review. Please keep me in mind. I'm currently searching for a good 10" electric brake assembly to replace my existing set, and I'm sure I will be reaching out to etrailer for their expertise.


The u-bolts fit and worked perfectly. I didn’t use the included tie plates, my travel trailer has shock absorbers that attach to the tie plates, I reused the originals. I torqued them to 70 ft. lbs. per Dexter axle specifications. I did clean and paint them before installing. I upgraded my 5400 lb. 4-leaf springs to 6000 lb. 5-leaf springs, which required longer u-bolts.


Wow! I have ordered from etrailer for years. Great products. I ordered this on a Tuesday and received it Thursday and shipping was Free!
Painting them now to match trailer and installing them tomorrow. All within a week. Like I said, Wow!


Exact replacement for the original ones


I used these on my M101A2 military trailer after doing axle swap. They work perfect.


I pull a toy-hauler 5th wheel trailer between Alaska and the lower 48 through Canada twice a year. Much of the road is rough and caused me to break a leaf spring every trip. Since installing a shock absorber system and upgrading from 5-leaf to 6-leaf springs, I have so far eliminated suspension damages on the route.


Good equipment


Hopefully adequate. Smaller than what I replaced for lessor capacity springs…. Good fit though…


Not much to say about this item because it’s only a u-bolt kit, but everything went great. The item came on time


Simple hold axle in place.

A year later and thousands of miles still working as it should
Anthony - 08/20/2022


Excellent service- product is just what was shown online- product arrived quickly


these u bolts and brackets arrived quickly, installed flawlessly, and seemed to be heavy duty.
i couldn't be happier.


Easy to find what I needed, easy to order, and everything arrived in a few days and fit perfectly


Easy install , some torque specs with the axle bolts would be nice to have with order. It was easy to find info on Google. Overall good quality product


Have not installed them yet but they look very good. Heavy duty as expected. One u-bolt is a bit twisted fresh out of the box but it should be easy to correct using a vise. Only one of the 8 I bought was this way. Must have slipped past quality control at the factory. It will not affect its integrity or usage.

The kit is working great. No problems with it. Many thousands of miles since the install.
Dave L - 08/28/2021


Quality product. Works perfectly on my 1968 Plymouth leaf springs.


All items arrived as ordered, on time and in tact.
Thank you


Perfect fit.


Fit perfect


Just installed them a few minutes ago. Great product. I liked the extra ribs in the bottom mounting plates. It seemed to add a great deal of strength. I thought the shipping was a little steep but all in all a good experience. Thank you.


Kit fit like it should.

Show More Reviews

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

  • Should the Tie-Plate Bend When Tightening Axle U-Bolts
    The recommended torque for a 1/2" diameter u-bolt like the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-8 is between 45 and 70 ft lbs. If you are having issues with the tie-plates distorting at 65 ft lbs then I recommend going with a torque setting on the lower end of the above scale. If the tie-plate becomes distorted too much this can weaken the metal but only slight distortion should not be too much of an issue.
    view full answer...
  • Can 3,500 lb Axle be Upgraded to 5,200 lb Axle
    I don't see any issues with running a heftier 5,200 lb trailer axle with leaf springs rated for 3,500 lbs as long as you're mindful of any changes that might need to take place like a longer U-Bolt Kit like part # APUBR-8 and larger tires/wheels as the hubs that fit the larger axle capacity have a 6 on 5-1/2" bolt pattern while your current setup likely has a 5 on 4-1/2" bolt pattern. This also means you'll need to make sure you still have 4" of height clearance from your tires to the...
    view full answer...
  • Kit Needed to Move Trailer Leaf Springs Back Under Axle
    If the leaf springs for your trailer are currently installed so that they are sitting on top of the axle, you can just use a standard U-Bolt Kit to move the leaf springs back under the axle. For a 2-3/8 inch, 3,500 pound axle, you will need the Redline U-Bolt Kit # APUBR-1 and for 3 inch axles with 5,200-7,000 pound capacities, you will use # APUBR-8. I have also attached a helpful installation video for you to check out.
    view full answer...
  • Choosing a U-bolt Kit for Trailer with 1-3/4 Inch Wide Leaf Springs
    When choosing a U-bolt kit for you trailer, you want to choose the correct kit based on the size of your trailer's axle. The width of the leaf springs isn't the main factor. The U-bolt kits you referenced will not both work on the same trailer axle. The # APUBR-8 kit can accommodate both 1-3/4 inch and 2 inch wide springs, but it is designed for use on 3 inch diameter round trailer axles that have capacities between 5,200 pounds - 7,000 pounds. The # APUBR-1 kit will accommodate 1-3/4...
    view full answer...
  • How to find the correct replacement trailer axle for overslung setup
    The Dexter Trailer Axle Beam with E-Z Lube Spindles - 86-1/2" Long - 5,200 lbs # 8327816 is the closest option available. The hub face to hub face measurement is only 1-1/2" more than your current setup, which won't cause any issues. The main thing to look at and match up EXACTLY is the spring seat to spring seat spacing. Since you need 68-1/2" spacing, and this axle provides 71-1/2" spacing, you will need to cut the spring seats off and move them to the appropriate spot for your trailer...
    view full answer...
  • 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...
  • 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
  • What is the Torque Spec for 1/2 Inch Axle/Suspension U-Bolts on 5200 Pound Trailer Axle
    On the 1/2 inch u-bolts in U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7" Long U-Bolts Item # APUBR-8 torque the nuts to 70 foot pounds each. If you need a torque wrench we have # ALL944001 good for 10 to 150 foot pounds and it has both a 3/8 inch drive and 1/2 inch drive.
    view full answer...
  • Distance From Inside Arc Area Of U-Bolt To Threads For U-Bolt Kit Mounting Kit
    I pulled one of the U-bolts we offer from our warehouse and took a quick measurement for you. The distance from the inside of the inside arced area of the U-bolt, part # CE23003 to the threads on the leg is 4-3/4 inches. The threaded portion is 2 inches. I also pulled another set of U-bolts, part # APUBR-8 and the measurement from the inside of the arc to the threads is the same 4-3/4 inches as well as the threaded portion being 2 inches. This is a 1/2-20 fine thread U-bolt.
    view full answer...
    Image 1 for
  • Replacement Double Eye Leaf Spring For 6,000 Pound Axle on 5th Wheel Trailer
    Based on my research, your Dexter leaf spring is a double-eye leaf spring with a 3,000 pound capacity for your 6,000 pound axle. The original length of your existing springs is 25-1/4 inches. As springs tend to stretch a bit over time, your existing spring likely measures between 25-1/4 inches - 26 inches. To replace the springs on your axle, you can use the # SP-111275 leaf spring. This double-eye spring has a matching length, 25-1/4 inches, and weight capacity, 3,000 pounds, to your...
    view full answer...
  • Torque Specs For U-Bolt Kit part # APUBR-8
    For the 1/2 inch u-bolts in U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7" Long U-Bolts Item # APUBR-8 torque the nuts to 70 foot pounds each. If you need a torque wrench we have # ALL944001 good for 10 to 150 foot pounds and it has both a 3/8 inch drive and 1/2 inch drive.
    view full answer...
  • Torque Needed to Tighten Nuts of 3 inch Trailer Axle
    The torque needed to tighten the U-bolts of a trailer's 3 inch axle like the # APUBR-8 is 70 ft lbs. If you need a torque wrench we have # ALL944001 good for 10 to 150 foot pounds and it has both a 3/8 inch drive and 1/2 inch drive.
    view full answer...
  • Replacement 24-7/8" Long Leaf Springs for 5,000 Pound Axles
    To replace your existing leaf springs the 6-Leaf Double-Eye Spring # SP-222275 will work perfectly. This leaf spring stack measures right at 24-7/8" from eye to eye (center to center) and its designed for 5,300 pound axles (which will work without issue on your 5,000 pound units). For a U-bolt kit I recommend the Redline # APUBR-8, which includes four 7" long U-bolts, two U-bolt plates, and the needed 1/2"-20 hex nuts. I have attached a couple short video reviews on these products below...
    view full answer...
  • Recommended Tandem Axle Trailer Hanger Kit for 40 Foot Trailer
    Yes, the length of the trailer frame will play a part in determining where to position the trailer axles. The axles will need to be placed under the trailer so that 10-15% of the total weight will be on the tongue. I have attached a photo below with the formula you will need to use in order to find out the best spot to place your axles. In regards to parts needed for the above, I recommend the Tandem-Axle Trailer Hanger Kit for Double Eye Springs part # APT5 with the U-Bolt Kit for Mounting...
    view full answer...
    Image 1 for
  • Does the Dexter 7K Trailer Axle with Electric Brakes Come Assemblied
    The Dexter Trailer Axle w/ Electric Brakes part # 8327864-EB does come with the hubs and backing plates already installed so you would be ready to go once it arrives. It however does not come with u-bolts so if you need those as well you can obtain the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-8.
    view full answer...
  • Heavier Duty Leaf Springs To Replace Dexter 072-097-00 On 2018 Keystone Cougar 311RES 5th Wheel
    I would be happy to help! Since your 2018 Keystone Cougar 311 RES 5th wheel with tandem 5200lb Dexter axles has the Dexter 072-097-00 leaf springs currently installed the 5-Leaf Double-Eye Spring for 6,000-lb Trailer Axles - 25-1/4" Long # SP-111275 you were looking at will be an exact replacement for you. These leaf spring are the same length at 25-1/4" and the 6000lb capacity of the # SP-111275 will give you the extra support you are looking for. For replacement U-Bolts I recommend...
    view full answer...
    Image 1 for
  • Replacement 6,000 Lb 26 Long Leaf Springs for Trailer
    I have just what you need to replace the leaf springs on your trailer, the 6-Leaf Double-Eye Spring for 6,000-lb Trailer Axles part # SP-053275 which has a 6,000 lb capacity and measures 26" from eye to eye. It does have six leaves so this may raise or lower the trailer marginally but other than that they will be an exact replacement. Please note. u bolts are torque to yield so you'll need to replace them when they are removed and I recommend the U-Bolt Kit part # APUBR-8.
    view full answer...
  • Do The Trailer Suspension Hangers & Equalizers Need To Be Changed Going From 3,500 to 6,000LB Axles?
    You may be able to use the same hangers and equalizers that are already being used on your triple axle trailer. First you will need to determine if you will be changing wheel and tire sizes that will require you to move the axles further apart so that the tires do not contact each other. This may also affect your trailer fenders if the axles are being spread further. If your tire spacing is okay you will then only need to find the larger capacity leaf springs that match the length of...
    view full answer...
  • Correct Replacement Leaf Springs for Grand Design 28BH
    The 5-Leaf Double-Eye Spring part # SP-111275 will be a great fit for a Grand Design 28BH with Dexter 5,200 Lb Axles and it offers a bit higher capacity than standard so you'll get more support and life out of the springs. They will be a direct bolt-on fit and replacement. Please note, new springs are shorter than the old ones as the older ones stretch. For a new u-bolt kit, you'll need the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles part # APUBR-8.
    view full answer...
  • Recommended Replacement for Dexter Trailer Leaf Spring 072-099-00 and U-Bolts 011-017-01
    The closest match we have for a Dexter Trailer Leaf Spring 072-099-00 is the 4-Leaf Double-Eye Spring for 4,000-lb Trailer Axles part # SP-051275 which will be an exact fit. The only difference being a slightly higher capacity of 4,000 lbs compared to the 3,000 lb rating of the existing. Please note, the leave count difference won't affect fit or function. The for the Dexter U-Bolts 011-017-01 you cab replace these with the U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles...
    view full answer...
  • Correct U-Bolts For 3,500Lb Dexter Axle
    Every 3,500lb Dexter axle we sell has a diameter of 2-3/8" and typically uses a 5-1/2" U-bolt, such as U-Bolt Kit for Mounting 3,500-lb, Round Trailer Axles - 5-1/2" Long U-Bolts # APUBR-1. You may have a 5,200lb Dexter axle, which has the 3" diameter that you seem to have. With this, you would typically use U-Bolt Kit for Mounting 5,200-lb to 7,000-lb, Round Trailer Axles - 7" Long U-Bolts # APUBR-8, but these U-bolts are 7" long, which seem to be an issue in your situation. The only other...
    view full answer...
  • Recommended Hanger Kit for Trailer With 5,200 Pound Lippert Axle
    There is no specific measurement for how tall your hangers should be. If you are replacing existing hangers then it is best to match the size of what you have now. If not then the # APT8 would work well. Another good option would be the # APT5 which is our most popular hanger kit. We also have a table showing distances between hangers based on different leaf springs for this particular kit to make things easier. If you need U-bolts to mount your axle then you can use the # APUBR-8. I...
    view full answer...
  • Trailer Suspension Kit and Leaf Springs Recommendation for a Tandem Axle Boat Trailer 4,600 lbs
    As long as you are replacing everything (hangers, springs, hardware, equalizer), then yes, you can use our trailer suspension kit, # APT5. In fact, this is the kit that I recommend for your trailer. The hangers must be welded to the trailer. The holes that you see in the top of the hangers are actually for welding, not bolt holes. For the leaf springs, you will be much happier with the ride quality of part # SP-212275 for 3,500 lb axles. The other springs you referenced are for 5,000...
    view full answer...
    Image 1 for
  • Replacing 24 Inch Long Leaf Springs on Trailer with Dexter 3,500 Pound Axle
    The closest option we have to the measurements you took on your existing leaf springs is the 3-Leaf Double-Eye Spring # SP-216275. This 3-leaf stack measures 23-1/8 inches from the center of one eye to the center of the other and is designed for a 3,500 pound axle. Older leaf springs will stretch over time so it's not abnormal that the new leaf spring will be shorter than the measurement you took but I do still recommend verifying the length on your current springs. Make sure you have...
    view full answer...

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