B3 Dynamics Package Upgrade - BMW E92 335i, 330i, 335d, 330d

The B3 Dynamics Package is a combination of three Birds-exclusive performance upgrades designed to transform the ride quality, handling performance and traction on UK roads.

The package includes the famous Quaife ATB Limited-Slip Differential, the B3 Sport Suspension upgrade, and the B3 Anti-Roll Bar Kit. This package is available for all BMW E9x 3 series variants, most popularly the 335i and 335d.

Specification and price of the package can vary depending on model.

Prices and Applications

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What's wrong with the standard car?

It is widely accepted among enthusiasts that the ride quality and handling of the standard BMW E90 3 series is poor. The reason for this is because BMW have compromised parts of the chassis for the lack of a limited-slip differential.

The basic open diff used on these BMWs means that when a wheel slips and breaks traction, power is spun away through that wheel and the car loses drive. This is because an open differential always applies the same amount of torque to both driving wheels, and will only put through the amount it requires to power that spinning wheel (i.e. very little). The driver will see a light flash up on the dashboard signalling the intervention of the car’s traction control - DTC (Dynamic Traction Control).

While most would think that an open differential will only make you suffer in slippery conditions, enthusiastic drivers of this BMW generation will often see this light flash up in the dry too. The reality is that the wheels lift frequently over our bumpy U.K roads, thanks to the stiff springs, and the open diff means that the resultant wheel slip will slow the car down dramatically. However it also frequently happens on even road surfaces too…

When cornering at speed it’s normal for the inside wheel to want to lift, therefore losing power. BMW have employed a very thin rear roll-bar that helps the inside driving wheel stay as planted as possible (as opposed to using a thicker one that would make the chassis more rigid and more likely to lift the wheel during cornering).

The first obvious downside to this is lots of body roll. BMW have therefore countered by using very stiff springs, which is the main reason for its ‘crashy’ ride (the other being the awful run-flat tyres). The second downside is that BMW had to use a very thick front roll-bar also to limit the body roll as much as possible. Unfortunately now with a more planted rear end and less traction at the front, the driver will also experience understeer.

Ultimately the fact that BMW were so reluctant to install limited-slip diffs on the standard models (reserving them only for the M-Powers) meant that they had to compromise a series of chassis components. The result is a crashy ride that makes you avoid even the smallest pot holes, a frustrating inability to put the car’s power down even in dry conditions, and excessive understeer and body roll.


Birds' B3 Dynamics Package Solution.

After this ‘diagnosis’ was carried out on our 335i demonstrator it was subjected to months of testing, experimentation, data logging, and development work. The answers came in the form of just three carefully measure upgrades but which were designed in conjunction with one another...

The B3 Dynamics Package consists of, first and foremost, the famous Quaife ATB Limited-Slip Differential. This is a unique type of limited-slip diff that uses gears only, meaning it will never wear out, and is smoother and more progressive than conventional locking LSDs - perfect for RWD road cars and is Birds’ only choice of LSD. This will allow the car to vary its torque across the axle and apply power to the ground with maximum affect in an easily controllable way.



The second part of the package is Birds’ own spec of B3 Anti-roll bars. The rear-roll bar thickness is increased by 90%. Since the LSD now enables the car to apply power when one wheel slips during cornering, the stiffer rear roll bar can be used to eliminate body roll. The front is only increased by about 10%, but now closer in size to the rear (carefully calculated), the understeer is also eliminated.



Last but not least is Birds' B3 Sport Suspension. The B3 Sport Suspension stands alone as the only fully customised suspension kit for the E9x 3 series variants that has been made available “off-the-shelf”. Birds’ new suspension consultant Rhoddy Harvey-Bailey advised to look no further than Bilstein for dampers, but none of their sports kits were good enough. After a lot of experimentation Birds commissioned a series of carefully measured spring rates and damper curves for the different 3 series shapes and sizes, and started offering them in suspension packages. 


By combining these three elements you have an upgrade package that enables the BMW to ride, handle, and put power down unlike any other 3 series. 


Editorials and customer testimonials.

Some of our best customer feedback can be found on the BMW internet forums. Google us and our products for real, unsolicited feedback from genuine BMW enthusiasts!

"Birds' B3 is a revelation. It rides out bumps with aplomb with the suspension adjusting and settling in one deft movement, and the front wheels steadfastly maintain their bite with the tarmac when you hit expansion joints with some lock on. Ultimately, Birds has turned a nervous chassis that was at best 'entertaining' into a seriously quick and comfortable missile, proof positive that you can have both ride quality and performance" - Bob Harper, BMWCar magazine.

"Perhaps the biggest compliment we can pay Birds' B3 is that it feels so cohesive. No one element of the conversion dominates the experience, and it's so well-rounded you get the distinct impression that if BMW's M-Division had opted to develop the 335i's biturbo six instead of going down the high-revving naturally aspirated V8 route, the B3 is what they would have arrived at." Richard Meadon, EVO magazine.

(Use the filters in our library to view all editorial features and our growing list of testimonials!).

You can also watch one of our customers demonstrate how the package was developed to work equally well on track as it does our U.K B-roads in his B1 Dynamics Pack equipped 130i at Silverstone and the Nürburgring below: