RE: CHR Fitment Experiments

RE: CHR Fitment Experiments

The initial failures.

Back in June 2022, I experimented a unique tire fitment for the E60. I wanted to run meatier tires taken from the Nissan GTR. 

My first attempt got no where close.  

I got close, but no cigar. 

The second attempt got close, but ultimately a few millimetres made it impossible to make it work within street friendly alignment specs.

"By using a 255/40 and 285/35 on the 20" tires, I was the OEM ratios but going up 1". This made everything more complicated."

The front. 

The 255-40-20 tires cleared the B16 perches once they were fitted. I documented this here

They were still tucked, even when using the BBS provided 10mm spacers for the front. 

I was far removed from my E92 fitment. To get close was ultimately my goal. 

The rear. 

The 285-30-20 rear tire & wheel looked great when mounted. 

The E60 remains a heavy car. Even with the B16s Damptronics, it squats noticeably on hard acceleration.

The tires overwhelmed the rear wheel arch and would rub the inner fender by the rear doors under acceleration. 

The overall diameter was simply too much. 

 

We tried trimming the fenders and playing with negative camber & toe in. 

Nothing would do it. It was quickly becoming unrealistic with reasonable alignment specs and subtle body work. 

We gave up. 

Had it worked out: it would have been more comfortable with better ground clearance, and the tire to fender fitment could have been proper.

Taking a step back, and moving down. 

The natural fitment. 

I ultimately went back to the natural tire fitment with 20in wheels on the E60. I went with Michelin PSS 255-35-20 and 285-30-20. 

This retains the original wheel & fitment overall diameter. I already had the rear tires on hand. The Michelin PSS was getting long in the tooth and few distributors still stock these as Michelin phases these out. 

I found a set of brand new takes off from a demo Shelby GT500 and brought these to the shop. 

The new fit & height adjustments.  

The new tires got fitted and put back on the car earlier in September. This required adjustments to ride height. 

We lowered the rear by 1.2 inches and the front by 1 inches. I wanted to keep the front more compliant, and retain the natural E60 rake for a flat ride.  

BBS quirks & spacers. 

The BBS CHRs have notoriously weak offsets on the E60 and have a larger than required hub bore. 

BBS provides their own PFS (Precision Fitment System) hubcentric & hub bore adjustment spacers to fit. 

We fitted the 10mm spacer to the rear as we could now be much more aggressive considered the lower overall diameter. 

My friend @Gordon.m3 sourced BBS' hub bore rings and supplied a 20mm front spacer for the front wheels. 

The Near-Final Results. 

I felt the rear was too aggressive relative to the front: 20mm still wasn't enough. I also feared the 10mm spacers would be too much as we planned to remove negative camber from the rear for drivability. 

The suspension needed to settle before alignment.

The Final Results. 

The front specs. 

I had Dinan camber plates laying around and ready to fit to the front in order to achieve the ideal fitment. The E60 is commonly known to have limited camber adjustment with the OEM top mounts. 

The quasi-double wishbone front suspension naturally cambers negatively when lowered. I still was genuinely surprised to see it settle to -2.0 at the front without the Dinan camber plates. 

This meant I had room to add 10mm to the front track. Stepping up from a 20mm to a 30mm meant a new level of machining and engineering work was required. 

I ordered a set of H&R 30mm TRAK+ spacers. They are hubcentric and use OEM bolts to attach the wheels to the spacers directly.

The spacers are previously fitted to the wheels using H&R's supplied bolts. 

It's a proper kit without any vibrations. 

The rear. 

The rear fitment was a bit easier. I initially re-fitted the 5mm PFS spacers at the rear as I feared taking out camber would cause rubbing. 

It came out of the alignment rack sitting at -1.5, similar specs to stock. It was mild looking, and just what I wanted considering how I use this car. 

I felt there was still some room at the back and ultimately fitted the 10mm PFS spacers. 

The fitment was now right where I've always wanted it, and most importantly, without any rubbing. 

The final specs table

Wheels (w/ spacer) Tires Ground to Fender  Camber
20x9" -4MM  255-35-20 Michelin PSS 26.5" -2.0 
20x10.5" +14mm
285-30-20 Michelin PSS
26" -1.5

 

"Overall, this was a long, pain staking, yet rewarding process. 

Fitment decisions can take a while to figure out, even more so with the current delays in supplying parts and limited shop time.

The end result was worth it and hopefully brings clarity to a BMW chassis with unique fitment specifications."
-Matt


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