GENERAL MOTORS 13427070 BOLT

This Bolt Kit (GM 13427070) supplies the front subframe body mounting bolt set for the Opel / Vauxhall Corsa D (2006–2014) and the shared SCCS platform family: Fiat Grande Punto (2005+), Fiat Punto Evo (2009–2012), and Alfa Romeo Mito (2008–2018). These are the bolts that secure the front subframe cradle to the vehicle body at its four mounting points. They are single-use stretch bolts (torque-to-yield) that must be replaced every time the subframe is removed — reusing stretch bolts after torquing is a safety risk and is not permitted by the OEM workshop procedure.

The four body mounting bolts that anchor the front subframe cradle to the Corsa D / Grande Punto / Mito chassis are torque-to-yield (TTY) fasteners — also called stretch bolts. A standard bolt is designed to be tightened within its elastic zone: the shank stretches slightly under load and springs back if removed. A TTY bolt works differently: during the final torque stage, the shank is deliberately stretched into the plastic deformation zone, beyond the point of elastic return. Once past yield, the bolt cannot recover its original length. This controlled plastic stretch produces a clamping load that is both extremely high and remarkably consistent — eliminating the variation introduced by friction differences on reused threads, and producing a joint that resists loosening from the vibration loads present on a front subframe carrying engine and suspension forces.

The consequence is that a TTY bolt is a single-use component. Once tightened to its final specification, the shank has permanently changed its mechanical properties. If the bolt is removed and retightened, it enters a region of the stress-strain curve where it can no longer produce a reliable clamping load — and may fail entirely under dynamic load if it has been stretched beyond its ultimate tensile capacity. The GM workshop procedure for this platform explicitly specifies that subframe body mounting bolts must be discarded and replaced with new items every time the subframe is removed, without exception.

On the Corsa D in particular, subframe removal is common due to corrosion replacement — the platform is a well-documented corrosion risk in road-salt regions. Every subframe replacement on this vehicle generates a mandatory requirement for four new body mounting bolts. Supplying this bolt kit alongside the subframe at the point of order eliminates the risk of a technician reusing the old corroded or previously stretched originals, which is one of the most frequent causes of subframe movement, creaking, and workshop return visits after a subframe repair on this platform family.

Old subframe mounting bolts from high-mileage Corsa D examples typically present with heavy surface corrosion, seized thread sections, and visible necking (waist) at the shank mid-point where the plastic stretch occurred. Even bolts that appear visually clean should not be reused: there is no non-destructive way to confirm whether a bolt has been stretched to a safe or unsafe extent. The correct and only safe approach is replacement with new TTY bolts every time the joint is opened.

Automotive structural bolts are typically classified under HS 7318.15 (screws and bolts of iron or steel). Verify the exact 10-digit subheading and applicable duty rates with your customs broker. Commercial invoice description: High-tensile steel bolts for automotive subframe mounting.

1. 1
   Never reuse the old subframe mounting bolts. Discard all four original mounting bolts once removed — they are torque-to-yield fasteners and have already been permanently stretched during the original or previous installation. Reusing them risks under-clamping and subframe movement under load.
2. 2
   Inspect and clean the body mounting holes on the vehicle for corrosion, thread damage, or debris before fitting the new bolts. On corroded Corsa D examples, the body mounting holes are often heavily corroded — repair any thread damage with appropriate inserts before fitting the new subframe and bolts.
3. 3
   Apply a thin film of engine oil or anti-gall lubricant to the bolt threads before installation. Dry installation of high-tensile structural bolts into corroded threads significantly increases the risk of galling and inaccurate torque reading.
4. 4
   Hand-start all four bolts before tightening any of them. With the subframe positioned and all four bolts hand-started, verify the subframe is sitting squarely and all mounting holes are correctly aligned before applying torque.
5. 5
   Torque in two stages using a calibrated torque wrench. Stage 1: snug all four bolts to approximately 30 Nm. Stage 2: torque to the OEM final specification — typically 120–140 Nm for the rear mounting bolts and 100–120 Nm for the front mounting bolts on the Corsa D platform. Verify the exact figures in the GM or Vauxhall workshop manual for your specific model year. Some variants use an angle-torque final stage rather than a pure Nm figure — check the manual before proceeding.
6. 6
   Do not re-torque or retighten the bolts after the final torque stage. Once a TTY bolt has been torqued to its final specification, it must not be retightened. If any bolt was tightened incorrectly, remove and replace it with a new bolt — do not attempt to correct the torque on an already-stretched fastener.