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How tight should leaf spring U-bolts be?

Author

Andrew Vasquez

Updated on March 18, 2026

How tight should leaf spring U-bolts be?

Tighten all U-Bolts until they are snug only. Tighten in the sequence shown to approximately 1/3 of recommended torque.

Thereof, how tight should leaf spring bolts be?

Tightening the shackle bolts too much will squeeze the shackle straps against the leaf springs and the whole suspension system will bind and cause problems. The best thing to do when tightening down shackle bolts is to use lock nuts and tighten them until they are snug and then backed off 1/4 turn.

Secondly, what is the torque specs for U-bolts? A properly torqued u-bolt stretches by design resulting in a clamping force that acts as a spring clamp, holding the components of the suspension together. The torque specs for a 1/2" u-bolts which is the size most frequently used on Venture Trailers is 45ft/lbs-70ft/lbs.

Just so, can you over tighten U-bolts?

The threads on most u-bolts are rolled, not cut. Unlike cut threads, rolled threads are deformed when the u-bolts are first installed and tightened. The correct torque (clamping force) can never be achieved when reusing old u-bolts.

When should the U-bolts on a spring suspension be re torqued after installation?

Also, TMC recommends running the truck on a course where maximum articulation of the suspension occurs after installation, then loading the suspension before retorqueing the U-bolts. They should be retorqued again between 3,000 and 5,000 miles after replacement.

Can you over tighten leaf springs?

If you over tighten either end of the leaf spring attachments you can pinch the spring eye and eliminate all movement. You'll know if you've done this because you'll go from riding like a buckboard to riding like a steam roller.

Are sagging leaf springs bad?

Leaf spring problems: Leaf springs can sag and weaken or one of the leaves can crack, fracture or break. If one of the leaves in the spring is broken, both left and right leaf springs are usually replaced at the same time, unless the vehicle is almost new.

Why would u bolts have to be tightened correctly?

centre bolts hold the spring together for assembly and help locate the spring onto the axle in the correct position. Correctly tightened ubolts are what holds the springs firmly in place on the vehicle when driving. Most times just supplying the vehicle make, model and year will be enough.

What grade are leaf spring bolts?

Grade 8

Do leaf spring shackles move?

Be careful not to overtighten the leaf spring shackles. Overtightened shackles will not move along with the springs or function properly.

How do you remove tension from leaf springs?

Loosen the U-bolts to remove them. Then, slide the bolts off of the axle. The bolts are horseshoe-shaped, so they are very distinct and noticeable next to the leaf spring. If you have an extra floor jack, placing it under the spring removes some of the tension, making the bolts easier to remove.

How do you adjust the angle on a leaf spring shackle?

Since you don't have the full weight, you can pull all but the main leaf from the spring pack. Measure back from the center of the front spring eye the flat length of the spring (54" or 60" as appropriate) mark plumb 0° then, use your sliding bevel/protractor/angle finer to mark your desired shackle angle.

What is a shackle bolt?

Leaf Spring Shackle Bolts, 3-1/2 In. Shackle bolts are used to secure your trailer's spring leaf. This shackle bolt is 3-1/2 inches long and 9/16 inch in diameter. Each bolt is fluted to prevent wear and tear on your hanging plates.

Is it OK to reuse U-bolts on leaf springs?

While the U-bolt has some flexibility in its ability to stretch after being loosened, the bolt will never tighten enough to allow it to regain its full torque spec potential. The next issue with trying to reuse U-bolts has to do with the threads themselves. When being tightened, the threads stretch out under torque.

Do you have to replace U-bolts when replacing leaf springs?

U-bolts are a vital part of your suspension system and should never be reused. Failure to replace or properly fit your U-bolts when maintaining or servicing your suspension could cause premature failure of your leaf springs or other components with catastrophic results.

Do U-bolts need to be torqued?

Do not reuse U-bolts

Deep nuts should be tightened once and retorqued, never loosened and retightened. A used U-bolt may have suffered from fatigue as well excessive stress since achieving accurate torque with commonly used impact wrenches is very dificult.

Should leaf springs be lubricated?

The springs should be kept fairly clean in order to extend their useful life. Modern leaf springs do not need lubricating with oil — which may damage any anti-friction material between leaves. Spray them instead with a silicone-based lubricant.

How much weight can a 5/16 U-bolt hold?

U-Bolt
abbreaking strength
1/4"3/16"2000 lbs.
5/16"1/4"3200 lbs.
3/8"5/16"4600 lbs.

How tight should bolts be?

In general, you should make the bolt tight enough so that the items it is holding together stay together, but not so tight that you damage the bolt's threads. You should tighten bolts properly so that the bolt performs properly.

Can loose U bolts cause vibration?

If the U-bolt comes to lose your rear end of the truck will vibrate. When the bolts come to lose the bolt itself start hitting against the axle, which may lead to bolt breakage. Moreover, it may disassemble the leaf springs, causing even more damage.

What does adding a leaf spring do?

An Add-A-Leaf is an extra leaf added to a leaf spring pack. Added leaves are installed to increase vehicle carrying capacity or to reduce sway by creating a firmer ride. They can also be used to increase the ride height of your vehicle.

What is the torque on 1/2 inch U-bolt?

between 45 and 70 ft lbs

What is the torque on a 7/16 bolt?

ASTM A449 / SAE Grade 5*
Bolt SizeTPITightening Torque (ft lbs)
Galv+Waxed
5⁄16189
3⁄81615
7⁄161425

What is the torque on a 3/4 U-bolt?

I spoke with the manufacturer and they recommend using 160 ft-lb for the torque spec on a 3/4 inch U-bolt # 11-70.

What is the torque on a 1 inch bolt?

US Recommended Bolt Torque
SizeRecommended Torque
Grade 218-8 S/S
3/4"125128
7/8"129194
1"†188287

What is the torque for 5/8 U bolt?

1/2” 65—85 ft lbs. 9/16” 85—120 ft lbs. 5/8” 95—130 ft lbs.

What does torque suspension mean?

A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. Vertical motion of the wheel causes the bar to twist around its axis and is resisted by the bar's torsion resistance.

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