BMW Subframe Reinforcement

The E46 M3 Is highly regarded by enthusiasts as one of the best cars BMW has ever built. Precise road going feel , 333 naturally aspirated horsepower , lightweight construction and more make it still one of the most desired M models on the road! This of course comes at a price as these models continue to age, and one ever increasing problem we see here is rear subframe damage in the form of cracks and tearing. Luckily this is a well known issue these days, and many kits are out there to allow us to reinforce the subframe after any crack repairs are performed.

The Process of subframe reinforcement is quite straightforward-- although tedious and time consuming to do correctly, especially when done in conjunction with recommended bushing upgrades!


Normally at the time of reinforcement, the normal course of action includes complete subframe removal, cleaning of the subframe and associated chassis floor and an up-close inspection for damage. If cracks are spotted, they are individually addressed by drilling the ends to terminate the cracking, ground down and welded. After the cracks have all been repaired, the chassis is prepped for the installation of reinforcement plates such as the ones here from Turner Motorsport.These are stitch-welded to the chassis, and then coated in POR-15, and then seam sealer/undercoat for rust protection.

After that, we move onto the subframe itself, as most customers elect to have the complete rear end re-bushinged using Powerflex Polyurethane bushings, which are lifetime guaranteed. Replacing the worn factory rubber bushings with the Powerflex bushings throughout greatly increases the feel in the rear end adding stability , traction and many other benefits, including more accurate alignments ! We normally press or burn out the worn existing bushings in the following areas and replace them with the upgrade parts:

  • Subframe Mounting Front and rear
  • Differential Mounting Front bushing and rear cover bushings
  • Rear Trailing Arm bushings (RTAB’s)
  • Various control arm mounting bushings as desired by the customer

After the rear end is reassembled, we re-mate it to the car, bleed the brakes and perform a laser 4 wheel alignment!

Upon completion of this service customers have peace of mind of no continuing damage to their chassis, and usually report that the car now feels like new again thanks to the host of new bushings in the back , restoring and even improving original handling characteristics!

If your BMW has an issue that another shop can’t fix, BimmerService by Tyspeed can fix it.