BBS RS-007 triple step fitment for e34

[GazM3]

Hey chaps.

Been working hard on the GO equation, but something that bothers me is running those heavy (and unattractive) E39 M5 copies in 18x8 non staggered form.

As they are not original I have no idea on the spec of them, if someone knows that would be a great base.

I have some metric 3 piece bbs rs been hanging around, and there is someone local who can spin up some custom triple step barrels for them. I dont want a crazy oversize wide fitment, but seeing im starting from scratch, I may as well fill the guards right out. With my old E34 I had some ACS type 1, (17x9 et6, and 17x10 et15). The rears fitted well, but the fronts poked out a wee bit too much.

I trial fitted my e24 ones which are 17x9 et15 and 17x10 et15. The fronts fitted well, but were pretty close to the inner strut (talking 5mm or so) and the rears fitted fine.

the measured specs on my bbs rs database are

bbs 007
415x8.26 et15
nominal width 209.8mm
actual width (lip/lip) 230.0mm
backspace 160.0mm
frontspace 60mm
centre thickness 10mm (unconfirmed)
hub to inner lip 135mm

bbs e24 custom front
17x9 et15
nominal width 228.6mm
actual width (lip/lip) 248.8mm
backspace 169.4mm
frontspace 69.4mm
centre thickness 10mm (unconfirmed)
hub to inner lip 144mm


bbs e24 custom rear
17x10 et15
nominal width 254.0mm
actual width (lip/lip) 274.2mm
backspace 182.1mm
frontspace 82.1mm
centre thickness 10mm (unconfirmed)
hub to inner lip 157mm


I rekon a slightly smaller wheel on the front say 3mm off inner and outer will be OK giving a nominal measurement of 18x8.75et15
for the rear probably can go +3mm on each making the size 18x10.25 et 15.

Im pretty confident with the fronts, but ill need to check the rears to confirm how much room I have on the inner side of the equasion.

I want to run a 275wide tire to maximise grip. Will run an adjustable rear sway bar and around -2.5deg of front camber to compensate for the stagger. The rear guards have been massaged already.

Its an expensive mistake if I get it wrong. Anyone else have any data on wide wheel fitments

[jmile46]

All those measurements make my head hurt lol. Put it this way, I fit a set of wheels off my m3 that were 18x 10.5 et 16 in the rear and they fit perfectly. I’ve seen guys with 11.5s in rear of e34 but with stretched tires.

[zubbie]

You can measure all you want and ensure the rims will fit but in the end there is much variation in actual tire size between brands. I.E. no two 275 tires will be the same unless they are the same manufacturer and model. You need to test fit which means you need an understanding tire shop.

Also using 275 in the rear means you need at least 255 up front to minimize "tramlining" so front fitment may be the challenge as it needs more space for turning.

It's been done but usually by rolling fenders etc. Post pics please so we can see.

I'm running the following rondell 58s with 235, 255 tires. Still room to go bigger but not by much without rolling.
Front wheel size: 17 x 8.5, ET 13
Rear wheel size: 17 x 10, ET 15

[GazM3]

I’ll do some accurate measurements tomorrow. I here your point with the 275 wide tire variations. I’m planning to go either Michelin Pilot sport 4 or Bridgestone re-71r. The Bridgestones are a wide fitment so it may work out 245 & 265.

Im not really to worried about the stagger. I have had a good outcome with the stagger on the e24 with using adjusable rear sway bar and running more front camber.

yes the measurements hurt my head. The only way to get it right is to specify an exact back space (and front space) measurements from some known points as it seems the nominal wheel measurements are most likely from inside where the tyre sits which is impossible to measure without removing the tyres.

[GazM3]

Settled on the following.

18x8.5 et13
18x10.5 et21

the rear will give the same outer measurement to the guard but bring it in 12mm. On the 17x10et15 there is a measured 25mm to the strut.

Both wheels will sit approx 12mm from the strut housing which is pretty well close to oem on the front giving room for decent rubber and tyre deflection under load. I could go wider but I don’t really want the rims poking it from the guards.

[BleedsBlue]

Gaz, I performed this project on my '86 911 (albeit just making them wider, not bigger diameter), and I spent several weeks ironing out the measurements before making the expensive lip and barrel order. Just make sure to measure and calculate thrice over before ordering--desired widths are one thing to figure out, but offset and how the wheel center plays into it are another ball game (and that's before the tire brand/model difference Zubbie mentioned--and the way various width wheels affect the same size tire via poke and stretch).

One big question: just how much camber, front and rear? Obviously camber and fender lips have much say in final fitment and potential rubs. And as you've noted, camber can eliminate understeer more effectively than 'square' tires.

Offhand your rear fitment looks safe to me. I've run a variety of rear 9.5 ET21 (and one ET22) 18" rear wheels, with spacers up to 15mm IIRC. On the front I've had no issues fitting 9.5" with effective offsets around ET0-8, depending on camber.

The RE-71R (helluva tire) run fairly narrow, but I would still want more than an 8.5 in that 245. They aren't good pinchers particularly under a heavy chassis.

[GazM3]

Hey Brent.
Cheers for advice. Yes I’ve triple measured everything hopefully it’s all good. That’s the problem with offsets and the like they are a nominal measurement. When getting wheels made u need some exact measurements.

Id like more wheel on the front but with 18” they are tall. Better safe.

Im going to run around -2.5 deg with 0.3mm per side of toe in on the front and around -1.5deg and 0.6mm toe in on the rear. I’m adjusting camber at the front with the weld in Ireland engineering slotted bolts as they will give me a wider track but not so good for wheel clearance. On the rear I’m fitting up the powerflex black series bushes with the eccentric bolts. It sits pretty good now but it would be great to dial in some exact settings. Most of the bushes are pretty flogged out so it makes sense to replace them.

Ive got 245/35 on existing 8” rims. They fit nice. Could probably go for 255 up front and 275 on rear seeing the bridgesonta are relative skinny fitment. I want to do the odd track day in the car. There is no point having c/550bhp without being able to use it in 3rd and 4th gear without the fear of police action.

[BleedsBlue]

Roger on the negative camber- those are good street-driven numbers and will surely help.

I'm not following on the 18" being taller bit, since the 18x9.5 up front I've played with was wrapped in a 265/35, a few mm less OD than your common 235/45R17. Is that not down to tire size? I believe the 18" barrel also nets more clearance to the bottom of your spring perch, but I forget having been on coilovers for a while now.

Nothing wrong or unsafe with 245, 255 etc on an 8J. But both subjectively (squirm, steering feel) and objectively, tires like those 'Stones like a bit of stretch. I've experienced it firsthand, but mainly in autocross and the like--the type of driving us responsible adults surely will not partake in on the street