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For those considering the purchase of aftermarket wheels, please consider the following.

1) the Factory OEM wheels weigh 10.71 kg/23.56 lbs front and 11.6 kg/25.52 lbs.

2) The 20" Hartge Nova 7 wheels weigh nearly 9 lbs more than the OEM wheels! This does "wonders" for unsprung weight, steering feel and turn-in! The 9J x 20 fronts weigh 14.65 kg/32.23 lbs while the 10J x 20" weigh 15.5 kg/34.1 lbs. The extra 1" of overall diameter vs. OEM also does "wonders" for acceleration by rendering the final drive ratio "taller" (numerically smaller).

3) The 19" BBS LM wheels are nominally lighter than the OEM wheels. The 8.5J x 19 fronts weigh 10.44 kg/22.98 lbs, while the 10J x 19 rears weigh 11.12 kg/ 24.46 lbs.

CONCLUSION: Unless one wants to purchase aftermarket wheels for aesthetic consideration or to allow the fitment of 380mm front brakes,
the Factory issue OEM wheels are damned light considering that they are one-piece cast wheels!!!
 

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Just my $0.02. I've always loved stock wheels on any M car - even the awful "whitewall" 17's on the early E34's - because it's one of the few identifiers of the M brand. I will never upgrade my wheels...I also deplore M wheel knockoff's.

Alps
 

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I had an earlier post in which I received do response. So let me ask this again. I am interested in set of track wheels (tires and rims).

1.) Would you put 4 equal sizes tires at all 4 corners?

2.) Would you select OEM or aftermarket rims to do this? Cost is a consideration, so I assume OEM are more expensive.
 

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I have a similar question to Jeff L. I autocrossed with my M5 the other day. What a rush!! I was fairly sloppy since it was my very first autoX experience but it was a blast. I really don't want to eat my street tires doing this and would like to have a set of stickier tires mounted on a different set of rims for autoX/track. The Michelin Pilot Sports are UTOG 220 rated. For the track I would like to have a DOT tire <UTOG 150. Also, the wheels don't need to be beautiful(I don't want to spend $500/wheel). Does anyone know the offset of the front and back wheels? I have had a difficult time finding the same size wheels and tires for the track.
John
 

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1. I wouldn't recommend using same sizes tires on all four corners. Here's what I think:

- You don't want to go with a narrower size on the back. The M5 needs all the rubber it can fit on the back to keep the power to the ground. If you go with wider tires, you get better rear traction but the car will have a higher tendency to understeer.

- You don't want to go with a wider size on the front. You will decrease the understeering but you will take away some of the turn-in responsivness.

- Are you planning to upgrade the suspension in the future? If so, you might want to do that before getting the wheels & tires. The handling characteristics will be a lot different after the upgrade.

- Bottom line, I will stick with the same size in the front if possible and go with a wider size in the rear. what sizes are available in the tires you want to get?

2. I will definitely go with aftermarket rims for track use. They are cheaper and some(like the BBS) are actually lighter than the OEM wheels.

Originally posted by Jeff L:
1.) Would you put 4 equal sizes tires at all 4 corners?

2.) Would you select OEM or aftermarket rims to do this? Cost is a consideration, so I assume OEM are more expensive.
 

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Does anyone know the offsets of the front and rear wheels? Aftermarket for the race wheels/tires is probably the way to go. Is there any tires that are <UTOG 150 other than the Michelin Pilot MXX3(UTOG 140) that are compatible with the wheel sizes? So far I have not been able to find any.

John
 

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My message was cut off. Are there any tires < UTOG 150 other than the Michelin Pilot MXX3(UTOG 140 but expensive) that would fit the front and rear wheel sizes? So far I have not had any luck finding a sticky tire in the right sizes.

John
 

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there is good reason for why formula one and cart and indy cars all have larger rear tires vs. front tires. i would definitely not put the same size tires all round. i think bmw has found the right balance with the two sizes currently
 

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Disagreed healeyg!

The M5 has almost 50/50 weight distribution (unlike the F1 and Indy cars, or Porsche and Ferrari for that matter)... For track driving, having the same size tires all around with a good suspension setup may be ideal. On the street, the smaller fronts introduce a bit of safe understeer and tramline much less.

Dan
 

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For what it's worth...

I agree with your comment except for one thing... it's not accurate to compare "weight" distributions of M5 to Porsche, ferrari, and especially F1 for both aerodynamic and power to weight reasons. In all of those cars, the ratio of aerodynamic downforce at speed compared to mass is much greater than with the M5. Especially with the F1, the "weight" distribution of the car due to gravity has very little value in itself. For each track the car is tuned for the speed of the corners they want to go fast on, and the effective weight distribution (gravity plus downforce) is what's important.
 

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Picking up on old topics, Grinch?

Agreed, at speed, the effects of downforce on an F1 car, and to a lesser extent on sporty street cars, is the main factor. My point is that the issue with understeer is at lower speeds. I, for one, certainly prefer understeer at higher speeds (over 100mph). The main complaint is understeer at lower speeds, like tight corners. And that the M5 may benefit from same size tires on all corners. And more to the point was that the F1 example was a poor one to begin with.

Thks, Dan
 

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For what it's worth, if you can get your hands on a nice set of OZ Racing wheels, they are hard to beat in weight of wheel department... especially the Magnesium Alloy wheels... But of course at a price..


Safe, good drinving all

------------------
ho nuovi calzini su!!
 

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Unless you really have money to burn, having the same size would allow rotation, especially of an R compound tire. I would imagine a slightly smaller tire in back would not make that much difference in putting the power down.

I love my BBS RC's. One thought. In terms of track tires, 18" options are rather limited but 19" are very limited. You may even want to explore 17" options.

I run my original turbines on the track and Toyo just so happens to make the RA1 in a 235/45/17.

------------------
Kevin Kelly
91 M5
Dinan chip
Dinan Stage III
Racing Dynamics sway bars
18" BBS RC's
turbines for the track
 

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I agree with Daniel, it would be worthwhile to try a car with same-size all around. Some people would no doubt hate it, but others might like the handling. Different driving styles.

Anyone running 17" on their E39 M5? I forget what the brake rotor size is for M5. I've heard that with some brake upgrades you need to go to 19".
 

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I've successfully run 17"s in a track set-up, so the clearance is adequate with the stock brakes.

I run a staggered set-up to match the OEM gear: 17x8 with 245/45-17 in front, and 17x9.5 with 275/40-17 in back. Wheels: Borbet Type-Es and Tires: Yokohama A032-Rs.

BTW, I used to run the same street set-up at all four corners on an E39 540i six-speed (245/40-18 gForce KDs), before the OEM set-up was staggered. While it helped with treadwear through tire rotation, there was 25-30% less power to the rear wheels!

I'll happily stick with the additional contact patch at the back to put the power to the pavement....
 

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With the problems with E39 wheel bearings, there is a strong probability of shimmy problems with 19" or larger wheels. SD
 

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Y'know, with the amount of money tied up in E39s, I'm surprised there's no permanent fix for this anywhere.
 

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Oh, and by way of clarification: what SteveD is referring to is sloppy tolerances and runout in the front wheel bearings of E39 BMWs in general.
 
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