285/30/18's on front? - The Unofficial BMW M5 Messageboard (m5board.com)

TiSiBeast · 3rd February 2008, 01:08

I have searched and searched but can't find anyone that has attempted this. I have scored a SMOKIN deal on a set of R compounds in this size, 4 of them. Rear I don't forsee an issue - fronts not sure if they will fit without rolling the fenders. I have rears on all 4 corners.

TiSiBeast · 3rd February 2008, 04:03

Bump - No one has any input on this? Someone MUST have tried it! If not, I may be breaking new ground here. For the price I am getting these tires for I have to buy them.

CSBM5 · 3rd February 2008, 05:04

Wow, if they are BFG R1s, then they will likely be more like 300mm section width mounted if my experience with the R1 is any guide. I had run 265/35 Dunlop R-comps on my 330i zhp for autox, and so I ordered some BFG R1 265/35-18s for it, and they are simply HUGE. In additon they are "section-width-wide" all the way out to the tread face (as opposed to being tapered like most tires). The mounted section width of the 265s on an 8.5" rim was more than 275mm. They ended up rubbing badly in the rear, so BFG stepped up and sent me some 245/40s (which are much wider than the 255 street tires on the car, lol).

Anyway, back to your request. I've looked at doing 285/30s all around on 9.5" OE wheels on my M5. Based on my experience with 275s all around on 9.5's, you'll need more than a 3mm spacer up front, especially with the R1 285. In order to have enough fender clearance with a spaced out 285, you will need some decent negative camber. I think it will fit on my car as I have a bit more than 2 degrees negative camber up front, but I've not tried it yet.

I would try them up front with a 10mm spacer with the OE 9.5" rear wheel. This gives an effective offset of 12mm. You would need at least 3+5mm to clear the strut, so a 10mm spacer should be the best bet...but again, you have to have serious negative camber.

If this was a 285/30 street tire, I think it would fit fine following the above. If it's an R1 or some other R-comp (which almost all run wider than their stated section width), it might be tough. Use OE rear wheels, 10mm spacer and try it out though!

FWIW, here is a shot of a 265/35 BFG R1 next to a 275/35 Nitto NT-01 R-comp (and the NT-01 is a tad wider than a typical street tire 275!).

Chuck

TiSiBeast · 3rd February 2008, 05:15

Thanks for the input Chuck - WOW that's a wide tire! I have 5mm spacers up front currently but clearly I will need more than that. I guess I need to get in touch with Ground control as well and order some camber plates. Anyone want to buy me a full set of coilovers with camber plates?

For the money I am getting them for though, I'll flip em to someone else at the same price if they don't work.

TiSiBeast · 3rd February 2008, 07:42

I did some more research, here is the technical spec info from BFGoodrich

According to this it will be 11.4 Inches on a 10" rim. I did a crude measurement on my car with a take and an eyeball, came up with a section width of about 10". That makes it 1.4" wider - that is A LOT more tire to try and stuff into the wheel well. I don't even think the rears would squeeze them without rolled fenders. Maybe I could put the rears on my 993... Hmm.....

Tire Size	Service Description	Sidewall	MSPN	Rim Width Range (inches)	Section Width on Measuring Rim Width	Overall Diameter	Tread Depth (in/32nds)	Revs/Mile at 45 mph	Max Load (lbs@psi)
P205/50ZR15	84W	BSW	62485	5.5 - 7.5	8.4 on 6.5	22.8	4	912	1113@51
P225/50ZR15	90W	BSW	06811	6 - 8	9.1 on 7	23.6	4	881	1301@51
P205/55ZR16	89W	BSW	21509	5.5 - 7.5	8.4 on 6.5	24.5	4	849	1279@51
P225/50ZR16	91W	BSW	12323	6 - 8	9.1 on 7	24.5	4	849	1367@51
P245/45ZR16/LL	88W	BSW	22748	7.5 - 9	9.57 on 8	24.65	4	844	1235@51
P225/45ZR17/LL	84W	BSW	09627	7 - 8.5	8.9 on 7.5	24.8	4	839	1102@51
P235/40ZR17/LL	84W	BSW	19220	8 - 9.5	9.5 on 8.5	24.2	4	860	1102@51
P245/40R17/LL	86W	BSW	39601	8 - 9.5	9.8 on 8.5	24.2	4	860	1168@51
P255/40ZR17/LL	89W	BSW	27377	8.5 - 10	10.2 on 9	24.8	4	839	1279@51
P275/40ZR17/LL	93W	BSW	95479	9 - 11	10.9 on 9.5	25.5	4	816	1433@51
P315/35ZR17/LL	93W	BSW	96664	11 - 12	12.6 on 11	25.5	4	816	1433@51
P225/40ZR18/LL	83W	BSW	09117	7.5 - 9	9.1 on 8	24.9	4	829	1074@51
P245/40ZR18/LL	88W	BSW	15639	8 - 9.5	9.8 on 8.5	25.4	4	819	1235@51
P265/35ZR18/LL	85W	BSW	03040	9 - 10	10.7 on 9.5	25	4	832	1135@51
P275/35ZR18/LL	87W	BSW	26533	9 - 11	10.9 on 9.5	25.4	4	819	1201@51
P285/30ZR18/LL	86W	BSW	39643	10 - 11	11.4 on 10	24.9	4	829	1168@51
P335/30ZR18/LL	95W	BSW	42166	12 - 13	13.5 on 12	25.7	4	809	1521@51

CSBM5 · 3rd February 2008, 14:23

...and if anything, they will be a bit wider than the tech spec shows. I think it will definitely take some serious effort to make them fit in the rear too now that I think about it. One thing you have going for you is their smaller diameter however.

If you go with GC coilovers, get the "jaj" style (i.e. board member jaj worked with GC to come up with a clearanced front strut design so no spacers are needed for 9.5/275 up front, hence that would help with room up front).

FWIW, here's another R1 picture...this time of the 245/40s they sent me compared to the 255/35 street tire on the zhp (which is a BFG KDW2).

SleepRM3 · 3rd February 2008, 16:36

Man, the BFG R1s are the teets; gotta try these on my M3 at my next DE.

Quote:

Originally Posted by CSBM5

...and if anything, they will be a bit wider than the tech spec shows. I think it will definitely take some serious effort to make them fit in the rear too now that I think about it. One thing you have going for you is their smaller diameter however.

If you go with GC coilovers, get the "jaj" style (i.e. board member jaj worked with GC to come up with a clearanced front strut design so no spacers are needed for 9.5/275 up front, hence that would help with room up front).

FWIW, here's another R1 picture...this time of the 245/40s they sent me compared to the 255/35 street tire on the zhp (which is a BFG KDW2).

EM5PWR · 3rd February 2008, 17:00

Nice tires.. Can I ask why would you want that big of tire in the front?? Isn't the 275 big enough?? Other than the fact your getting a killer deal on them..

TiSiBeast · 3rd February 2008, 17:46

Great deal plus I am DYING for a set of R Compounds for the track. You can NEVER have too much tire...

CSBM5 · 4th February 2008, 01:31

By the way, BFG has a manual you can download about the R1. If you have decent front camber (-2.0 or more negative), so you don't have to be compensating proper tire pressures too much, I would shoot for 39psi up front and 37psi rear hot pressures as a starting point (probably 32/30 cold or so depending on ambient temp and driving style). You may have to go a bit higher if you have street rate springs and less than ideal camber...check sidewall wear/roll over.

Here's the link to the R1 manual.

The R1s are VERY sweet R-comps. They are extremely communicative -- much better than a Hoosier A6 in that regard. They are great at trail braking since you can so finely feel what the contact patches are doing, plus they are somewhat forgiving if you go over the peak of the tractive force/slip angle curve unlike a Hoosier that just says goodbye, good luck. The generate lots of grip at low slip angles, so the steering response is fantastic. If you've not ever driven on R-comps before, take it easy, work up to speed, and DO NOT over do it.

Chuck