U Bolts — Sizing, Fitting and Why They Are Not Reusable

U bolts clamp the leaf spring pack to the axle on trucks and pickups. They are stretch fasteners: torquing them takes the steel past its elastic limit on purpose, which is what holds the clamp load. That is also why a used U bolt must never be refitted. This article covers measuring, ordering and fitting U bolts.

U bolt သည် leaf spring ကို ဝင်ရိုးနှင့် ချုပ်နှောင်ပေးသည်။ တင်းသည့်အခါ သံမဏိ ဆန့်သွားသောကြောင့် ပြန်လည် အသုံးမပြုရပါ။

1. The four measurements to send us — တိုင်းရမည့် အချက် လေးချက်

1. Thread diameter — for example 14 mm, 16 mm, 18 mm | ချည်အချင်း
2. Thread pitch — the distance between threads | ချည်ကြား အကွာအဝေး
3. Inside width — the gap between the two legs, which must match the axle | အတွင်း အကျယ်
4. Leg length — measured from the inside of the bend to the end of the thread | ခြေတံ အရှည်

Also tell us the bend shape: round bend for a round axle tube, or square bend for a square axle. A round bend on a square axle will not clamp correctly.

2. Fitting — တပ်ဆင်ခြင်း

1. Support the axle and relieve the load before removing the old U bolts.
2. Clean the spring seat and check the centre bolt is located correctly in the axle seat. If the spring pack is not seated properly, new U bolts will not fix the axle position.
3. Fit new U bolts with new nuts.
4. Tighten in stages, alternating across the pair rather than fully tightening one at a time, so the plate pulls down evenly.
5. Torque to the manufacturer's specification. Do not judge this by feel — under-torque lets the pack move, over-torque can crack the plate or strip the thread.
6. Re-torque after a short period in service. New U bolts settle, and most manufacturers specify a check after the first few hundred kilometres.

အနည်းငယ် မောင်းနှင်ပြီးနောက် U bolt များကို ပြန်လည် တင်းရမည်။