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BMW Z3 M ROADSTER SUBFRAME MOUNTING POINT REPAIR

Do you have a 2000 BMW Z3 M Roadster? One thing we recommend checking is the rear subframe mounting points/floor sheet metal. They can be weak and crack. This is a repair that needs to be caught early or the damage can be so bad it can total the vehicle. On this project, our BMW Master Tech Emil basically took the whole back of the car apart. The subframe had to be reinforced which can take up to 25-30 hours of labor. If you are looking for BMW subframe repair near Lexington Auto Engineering is your go-to shop.

PROJECT HIGHLIGHTS

Car: 2000 BMW Z3 M Roadster
Job: The rear subframe mounting points/floor sheet metal is very weak and can crack. If caught early, it can be repaired and reinforced. If caught late, the car is often totaled. This particular one had several spot welds that pulled apart and the chassis was cracked.
Diagnostic: Simple inspection of the car while on the lift, can be easily spotted.
Challenges: Making sure the chassis is straight before welding the reinforcement kit in. Once welded, any misalignment will be permanent. Crucial to straighten chassis first!
Notes: You can do this repair a number of ways. We did the simplest and cheapest way (just fixing the crack and upgrading bushings). Other options include – upgrading the diff to a double mounting system (factory diff uses only 1 mounting point) the randy Forbes kit allows you to add 2 mounts, but requires added parts and costs, only necessary if the car is being used for track racing. You would need an e36 m3 diff cover, and different mufflers to clear the second mount. Another popular upgrade to do at the same time while the subframe is out is to modify the subframe for alignment adjustments. From the factory, there are no camber or toe adjusters in the rear of the car. Garagistic makes a kit you weld onto the subframe allowing you to fully adjust the alignment. This is a great option to do for a streetcar as it can extend tire life and give the driver an optimally set up alignment.
Time: 25-hour repair for the roadsters, 30 hours for the coupe, more time if adding the double mount system or alignment tabs for the subframe.

HOW TO REPAIR A Z3 M ROADSTER SUBFRAME MOUNTING POINTS

 
 
 
 
 
 
 
 
 
 
 
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Inspect for broken spot welds that are seen from inside the trunk after trim removed, and from below the car
Remove the subframe, cut open the upper trunk to expose the inner beam of diff support member. This is where the primary reinforcement happens. Sand paint away to show bare metal in prep for welding.
Lower reinforcement piece positioned and held in place with vice grips. Then spot welded to the base of the chassis beam.
Weld vertical reinforcement to the lower piece, this creates an internal I beam in the factory open channel beam. Then paint with a rust inhibitor paint.
Close the open beam up with two more plates. Then are spot weld to the chassis, and one long weld down the venter attaching the top to the vertical support. You can also see the frame rails reinforced on the sides. After that it was all coat with paint again.

Schedule your next service appointment with us right online and save yourself time. Fill out the form and let us know what you are looking to get done and when!