Replaces BMW rubber bushing part numbers: 31121141752, 31129068734, 31129071085, 31120006482

Replaces BMW OEM control arms part numbers: 31121092609 and 31121092610

For V8 models only, does not fit 6 cyl models.

Fits the following BMW Models:

• 1997-2003 BMW 540i
  Automatic & Manual RWD Sedan & Wagon 4.4L V8
• 2000-2003 BMW M5
  Manual RWD Sedan 5.0L V8

Technical Info on the GAS Performance Monoball Design.

Like all GAS Performance products, our Monoball kit components are CNC machined by us in here in the U.S.A. to to extremely tight tolerances and with strict quality control. Many of our competitors have gone to a much cheaper to manufacture “press in monoball housing with raised ribs or knurling” to hold them in place. Why is this cheaper to manufacture? Two reasons: One, it eliminates the cost of machining the end cap and the cost of ten stainless steel cap screws; two, it allows looser manufacturing tolerances of the monoball housing. We hold a plus or minus 0.00025-inch tolerance on both the inside diameter and the outside diameter of our monoball housings. This combines to a overall size tolerance of plus or minus 0.0005-inch. These are critical aerospace component manufacturing tolerances. These tight tolerances are only possible when you manufacture your own parts in house with top quality CNC machines and check every single part with precision gauges. Typically asking a production manufacturer to hold 0.00025-inch tolerances will either result in a refusal to accept the job, or a cost increase of up to ten times that of typical production tolerances.

Consider this example, the control arms bores of the E90-M3 and E82-1M are 0.003 inch smaller and 0.034 inch narrower than their non-M counterparts, but we are the only monoball manufacture that makes different specific models for each! To us, 0.003-inch is a huge difference! In fact, 0.003-inch is six times our manufacturing tolerance!

Why do we feel it necessary to hold these tight tolerances? The answer to that question is too long to include here. Please view our monoball design video for more information on this subject.

So what about the end caps? Our end caps and stainless-steel hardware provide over 2500 pounds of retaining force, firming sandwiching our monoball housings within the control arm bores. The end caps, combined with our sleeve locking compound, guaranty that our monoballs will never move around in the control arm bores. Compare that to our competitor’s use of a snap ring that only prevents the monoballs from completely sliding out of the control arms if they start to loosen up. An added benefit of our design is that it allows our monoballs housings to be pressed out without damage and used again in another set of control arms. Try that with a ribbed or knurled design.

When you consider all the features just outlined, then compare the cost of our kits to other brands, why would you consider any brand other than U.S. made GAS Performance monoballs?

Frequently Asked Questions:

What benefits will I receive from upgrading my stock front suspension with GAS Performance Monoballs?

Due to the replacement of the rubber bushings in the tension struts with solid ball joints, you will gain a more connected and precise feel of the road. Steering inputs will be directly and precisely coupled to the front tire eliminating any vague feelings that were the result of the mushy rubber coupling built into the stock control arm design. Front camber, caster and toe values will remain in spec even under extreme cornering loads. Any shaking under braking that was caused by the old rubber bushing system will also be eliminated.

Will I need a front-end alignment after installing this kit?

It depends on the condition of the rubber bushings that were replaced, and whether the car had ever been aligned with the worn rubber bushings in place. Some newer BMW models have the mounting hole in the bushing a little offset from the center of the bushing; these models should have an alignment performed after installation of our monoballs. Toe is the only thing adjustable on most BMWs. A professional alignment check is always a good idea after replacing suspension components.

Will I experience more noise, vibration or harshness?

Yes, but it will depend on the BMW model and what other suspension mods are in place. The reason BMW used rubber bushings in both control arms was to reduce NVH. Feedback from customers, forum posts and our own personal experience has shown that for almost everyone, the increase in NVH is almost imperceivable, and the handling benefits provided by the upgrade out way any slight increase in NVH.

Can I return the kit if I do not like the increase in NVH?

No. Once the control arms have been installed, we cannot re-sell them as new once returned. We guarantee the kit components for defects and failures. NVH is not considered a defect. If you are very sensitive to NVH or live in an area with extremely bad roads use your best judgement before purchasing this kit.

Are there any differences between GAS Performance Monoballs and other Brands?

Yes, absolutely! Click the “TECHNICAL” tab or watch the video to find out more.