BIRDS BMW M235i

Tuner’s up­grade pack­age aims to cre­ate a mod­ern-day E30 M3 – with 390bhp

Evo - - CONTENTS - David Vi­vian (@david­j­vi­vian) Pho­tog­ra­phy by As­ton Par­rott

AFTER 38 YEARS IN busi­ness – a good many as sole UK im­porter of Hartge’s tun­ing parts – there isn’t much that Bucks-based Birds BMW doesn’t know about the in­ner work­ings of the Bavar­ian brand’s dy­namic make-up, or how to mod­ify the com­pany’s myr­iad sus­pen­sion and damp­ing set­ups for the pe­cu­liar de­mands of Blighty’s bob­bly black­top.

Per­haps the most in­trigu­ing ‘dy­namic pack­age’ it cur­rently of­fers is for the M135i and M235i, cars we love for their out­stand­ing tur­bocharged straight-six en­gines and stonk­ing per­for­mance. Nev­er­the­less, they fall a lit­tle flat in the chas­sis de­part­ment, not least by fail­ing to put their 321bhp to the most ef­fec­tive use. Birds’ demon­stra­tor is an M235i and the mission, ac­cord­ing to Kevin Bird, is to ‘pro­vide the driver with the best pos­si­ble com­bi­na­tion of ride, han­dling and trac­tion at­tributes for fast and safe road driv­ing’.

Iden­ti­fy­ing the M235i’s prin­ci­pal prob­lems as the ab­sence of a lim­it­ed­slip diff and the in­abil­ity to smear the rub­ber of both rear tyres more or less evenly on the tar­mac when that lusty pow­er­plant is be­ing ex­er­cised, Birds’ main weapon is a com­po­nent that’s be­come syn­ony­mous with its busi­ness: the Quaife ATB dif­fer­en­tial. At a stroke, the think­ing goes, three ir­ri­tants van­ish. No more need for man­age­ment-pegged power in the lower gears when the beans are de­ployed from a stand­still, no more in­ner-spin­ner when punch­ing out of a tight bend, and no more hy­per­ac­tive trac­tion con­trol, ei­ther.

Next on the hit-list are ride com­fort and body con­trol, which Birds con­sid­ers sub-par whether or not Elec­tronic Damper Con­trol (EDC) is fit­ted. Kevin Bird reck­ons EDC is worse – too soft in Com­fort for medium speeds, too hard and crashy in Sport. ‘Even if it worked,’ he says, ‘why do you have to press a but­ton to get the car to han­dle prop­erly?’ So Birds of­fers its own springs and Bil­stein dampers with cus­tom-spec valv­ing. The front track is also eased out and there are changes to the front and rear ge­om­e­try to im­prove sta­bil­ity.

Kevin Bird has a soft spot for the E30 M3 and reck­ons this Birds B2 Dy­nam­ics Pack­age matches the E30 for body con­trol and trac­tion. In fact, this M235i demon­stra­tor has had a remap to take it within touch­ing dis­tance of 400bhp and un­der­line the su­pe­ri­or­ity of the Quaife diff.

Dur­ing de­vel­op­ment, which in­volved in­put from ex-sportscar racer James Weaver, sig­nif­i­cant ef­forts were made to con­tain body roll with­out re­sort­ing to beefier anti-roll bars, and while ac­knowl­edg­ing their po­ten­tial for bi­as­ing the chas­sis away from un­der­steer, Weaver’s pref­er­ence for the road was to use damper tun­ing to con­trol the body in­stead. That said, anti-roll bars to Birds’ own spec are an op­tion for those want­ing a stiffer, sportier feel with less un­der­steer, although they’re not fit­ted here.

The first im­pres­sion is one of sheer thrust, the way this Quaife- equipped M235i sim­ply hooks up and goes. The meaty en­gine re­sponses are sharp with­out be­ing edgy and de­liv­ered with­out the faintest hint of re­ac­tive nerves from the chas­sis. Although the helm an­swers inputs alertly and ac­cu­rately, it fil­ters out the rigours of bumpy roads with poise. There’s a huge amount to like, here: true re­sponses and acutely re­solved feed­back; thump­ing torque and ur­gently de­liv­ered top-end power.

The abid­ing im­pres­sion is of tautly con­trolled sup­ple­ness that makes the sus­pen­sion’s in­dif­fer­ence to mid-bend dis­tur­bances all the more grat­i­fy­ing. Cus­tomers can opt for the com­plete £9643 pack­age (which in­cludes the en­gine remap, the Quaife-diff Dy­nam­ics Pack­age, 18-inch wheels and tyres, and anti-roll bars) or cherry pick as they wish.

‘There’s thump­ing torque and ur­gently de­liv­ered topend power’

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