Tire Options on my E39 M5 - Page 2 - The Unofficial BMW M5 Messageboard (m5board.com)

CSBM5 · 17th September 2011, 13:22

Quote:

Originally Posted by SoCalE39M5

IMO, I would run staggered too much grip up front is no good on a rear wheel drive car. 275's are only good for people that are trying to get every bit of tread out of their tires because it will allow you to rotate the tires front to back. If 275 square were the right way to go, car manufactures would all be doing it. Square tires is NOT the way to go on a high performance rear wheel drive car.

Let's be honest, we didn't buy our M5's to save money correct? These are for enjoying, no?

You're obviously very new to the E39 M5 world and/or have no significant high level (i.e. instructor) track and/or autocross experience with the E39 M5. The M5 is massively under-tired with the meager stock 8"/245 fronts for a 4000lb (without driver) 52/48 car. It is setup from the factory to massively and continually understeer, and at the limits, turns into a pig of a car by overwhelming those drag racer thin fronts.

The square setup transforms the car. However, you need to take it further than that to even come close to balancing out the chassis. Many years ago when I still ran the stock springs, I had GC camber plates up front on max negative camber, Dinan rear bar and 275/9.5" all around, and the car was almost neutrally balanced, but it still had a bias toward understeer -- just about a perfect one though.

Anyway, the 9.5/275 setup all-around is about the best modification you can make to the E39 M5. I've been running that setup for 7+ years now both on the street and my track wheels (I have four sets of wheels for the M5). Search the board on the subject. You really don't want to argue with the massively experienced user base here on the M5board many of whom have decades of track/racing experience coupled with a decade of E39 chassis experience...especially with making emphatic statements that all here have proved long ago to be false.

Cheers,
Chuck

CSBM5 · 17th September 2011, 13:37

Quote:

Originally Posted by sportscardog

Hello all,

I have BBS LM Rims 19x8.5(front), 19x10(rear) with 25mm and 17mm offset for street use. I have a separate set of of rims and tires for the track use. I currently run on 245/35-19 for the front, and 275/30-19. I also have Dinan Stage 3 Suspension (Koni) for that car.

I want a little more grip at the red lights. I am thinking of going 255/35-19 for the front, and 295/30-19 in the rear. I know the front is fine, but has anyone ever gone up to 295 in the rear? Any rubbing issues or did it clear? What is your rear wheel offset?

Thanks for any help!

Cheers,
John

John,

I don't have specific 295 experience, but I DO have experience with rear rubbing issues and where to look to gain clearance. I ran a set of R-comps from BFG, the R1, a while back on stock 9.5" ET22 rears, and the R1 is an extremely wide tire for its rated size. Not only does it physically measure out about 10mm wider in section width measurements, but it has a sidewall profile that carries the max section width all the way out to the tread face unlike most every other tire which is tapered. Hence it will rub where many other "larger" sized tires will not.

Anyway, the age-old 10 and 2 o'clock positions on the rear fender lip is the spot (on left side of car at 10, on right side at 2). If you look at those areas you will see where the factory fender lip roll stops. That lip roll needs to be continued further down another 30 degrees or so. If you don't do this, and you have the "typical" contact there, what will happen is on the rebound of the first contact, the tire will grab that lip and yank it down/out. Now on the next compression, that pulled out lip with gauge into the tire and chunk the crap out of it (you can see from my language I've dealt with this issue with a less than favorable outcome). So even if you don't think you'll have rub in the rear, I would strongly advise to continue that factory lip roll to rule out a future nasty outcome.

The spot on the inside you need to look at is likely not the strut but the front inside portion of that rear wheel well area which tends to get sidewall rubbing if there is too much backspacing.

Regards,
Chuck

JimBeemer · 17th September 2011, 14:37

Quote:

Originally Posted by mikeoski

You are much better off going with 275s all around.

+3 I recently went to 275s all around and love it! Before the Beast cornered like it was on rails, now it corners like it's on magnetic rails. As for the back end coming loose, with the DSC on it won't be a factor in daily driving and as for going with wider rears, tire rubbing at high speed is dangerous - nothing gets your heart pumping like a blow out at 80 mph after hitting a bump and the rears scraping. If you have your heart set on wider rears, go to a good body shop and get an estimate for wheel flares.

mikeoski · 18th September 2011, 14:16

Quote:

Originally Posted by ECB

Our cars naturally understeer which BMW dialed in for added safety. 275's up front allow for a more neutral setup. It's not done to try to save money.

I could not have said it better myself.

sportscardog · 18th September 2011, 21:59

I run 275s all around on the track. I also have a Dinan Stage 3 Suspension kit with adjustable sway bays. Dinan does not recommend more than a 20mm tread width difference between the fronts and rears for heavy driving with their sway bars and camber plates.

When I have my streets on (245 vs 275), and I am heavy into a corner, I notice the fronts start to slip first before the rears, and that I replace the fronts more often.

gsfent · 19th September 2011, 00:32

Quote:

Originally Posted by sportscardog

I run 275s all around on the track. I also have a Dinan Stage 3 Suspension kit with adjustable sway bays. Dinan does not recommend more than a 20mm tread width difference between the fronts and rears for heavy driving with their sway bars and camber plates.
When I have my streets on (245 vs 275), and I am heavy into a corner, I notice the fronts start to slip first before the rears, and that I replace the fronts more often.

I think it is only with the size change on the front bar, the rear is adjustable. Even with camber plates, 245's are not enough in the front.

Can you post where you saw that?
Regards,
Jerry

sportscardog · 19th September 2011, 08:51

My BBS LMs in the front are only 8.5" wide and so it's not possible to put more than 255s on the front, or I would gladly slap on 275s up front for street. I almost got BBS RGRs which are more racy and would take 275s up front, but I think the LMs are beautiful and it was an emotional decision. I've not been able to source replacement "hoops" to widen the two-piece fronts to 9" ot 9.5", so I'm stuck with my decision.

@ CSBM5 - Thanks for the detail and the warning.
@ gsfent - You are correct, they recommend to retain the factory front sway bar if your front and rear tire widths are more than 20mm different, but the rest of the system should work.

http://www.dinancars.com/shop/D190-5723K-Stage-3-Suspension-System-Koni-E39-M5.aspx#page=2 : "If your vehicle's tires differ in width from front to rear by more than 20mm, it is recommended that you retain the stock 27mm front anti-roll bar."

They "recommend" not more than 20mm. I figure that rule can be bent a little, so keep in mind that I have to monitor front tire temps and pressures aggressively if I push the car hard when I'm running on the LMs.

gsfent · 19th September 2011, 17:28

Quote:

Originally Posted by sportscardog

My BBS LMs in the front are only 8.5" wide and so it's not possible to put more than 255s on the front, or I would gladly slap on 275s up front for street. I almost got BBS RGRs which are more racy and would take 275s up front, but I think the LMs are beautiful and it was an emotional decision. I've not been able to source replacement "hoops" to widen the two-piece fronts to 9" ot 9.5", so I'm stuck with my decision.

@ CSBM5 - Thanks for the detail and the warning.
@ gsfent - You are correct, they recommend to retain the factory front sway bar if your front and rear tire widths are more than 20mm different, but the rest of the system should work.

http://www.dinancars.com/shop/D190-5723K-Stage-3-Suspension-System-Koni-E39-M5.aspx#page=2 : "If your vehicle's tires differ in width from front to rear by more than 20mm, it is recommended that you retain the stock 27mm front anti-roll bar."
They "recommend" not more than 20mm. I figure that rule can be bent a little, so keep in mind that I have to monitor front tire temps and pressures aggressively if I push the car hard when I'm running on the LMs.

Right, but that does NOT contemplate going to 9.5's all around. When you do that and square up the corners, you add significant grip to the fronts and remove the built in understeer. That is why you don't need a bigger front bar, and for street driving, the softest setting on the rear bar should be adequate, with the middle bar for experienced drivers on the track.

I have the Dinan stage 3 suspension with 9.5's all around and the rear bar on the softest setting. It works well on the street, makes the car feel at least 500 pounds lighter.

Regards,
Jerry