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      02-11-2011, 10:38 AM   #1
alefcole
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Rotational advantage for square vs staggered, experience needed.

I am thorn between ordering a set of APEX ARC8 NEW RIMS 10F/R with 275/35/18 tires square set up vs a 10F/10,5R with 265/35/18 and 285/50/18 tires staggered set up. People have mentioned the advantage of ROTATING tires with the SQUARE setup.

My question is basically on how much of an advantage I really get if a choose the SQUARE?. Is it worth it to create a little oversteering?

From people that went from square to staggered, how many EXTRA track days did you get? 1.5x, 2xmore track time? with the square setup.

Another way to put this is: If you have a staggered set up How many more rear tires do you buy rear vs front, or do you end up replacing the 4 of them at the same time?...

Plus if you buy directional tires in the square setup then you can only rotate front to back and viceversa unless you actually mount/dismount and balance tires adding around $200 to the cost.

I am a NOOB starting to get my feet wet in this awsome hobby and I need the humble opinion of my forum friends based in their past experience...Which setup will you choose? why? Thank you in advance
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      02-11-2011, 10:53 AM   #2
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Bump.

I'd like to know too, since I'm thinking about getting a track wheel setup.
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      02-11-2011, 10:53 AM   #3
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I'd much rather be able to switch from left to right than front to back, and you can do that with a staggered setup. That said, it's also nice to be able to take your worst tire and stick it on the corner that sees the least load, can't do that if your worst tire is a rear and it won't fit on the front. There aren't very many track tires that are directional unless you're using them in the rain and that's just for performance, not safety. I've used R888's backwards in the rain before, for instance. Not really a big deal.
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      02-11-2011, 10:53 AM   #4
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If you are buying new wheels with track use in mind, I see no reason not to go with a square setup. You will not have a general balance of oversteer, but rather, less understeer. If you rotate on a regular basis, you should wear out all 4 tires at about the same time. Regarding rotation, yes, for general street use you will need to flip the tires on the wheel at some point if they are directional. For dry track use, it makes no difference, run them backwards. Depending on the proportion of street and track, you might get by with never needing to flip the tires.
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      02-11-2011, 11:25 AM   #5
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I went through two sets of BFG R1 tires on this car, and they wore out fairly evenly F/R, so I didn't see the ability to rotate F/R as a big deal. You do need to rotate them L/R though depending on track layout etc. as indicated above.

However, the situation might be different for street tires or tires that can't cope with heat all that well. PS2s that came with the car (and I used before finding a track setup) did not do well up front at all under braking and wore out faster than the rears on the track.

I think the reduction in understeer you get from a square setup depends on your driving style. I experience severe understeer in my Z4M with its OEM staggered setup, but that was never really an issue in the E92 M3 for me after dialing -2.0 camber up front.
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      02-11-2011, 11:29 AM   #6
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For a pure track wheel & tire combo, I would absolutely go square.
Don't forget the better brake pads and higher temp brake fluid, however.

In 2009 I did several events (NJMP T-Bolt & Lightning, Watkins Glen, Pocono)
in my 08 E90 M3 with OE style 18" wheels and 265/40/18 PS2s on all 4 corners.
I also I ran 10mm spacers in the rear to make the rear track as wide as the front.

My car weighed 3,660lbs with 3/4 of tank of fuel. The car handled exceptionally well.
It surprised me all season long, at each track with its excellent capability.

The big wheels & tire up front took at out that last bit of understeer.
BTW: I think understeer is a very minimal issue in stock E9X M3s anyway.

As Radiation Joe and I found out, running the factory 18" rear wheels and tires up front with 265s will cause rubbing in the front inner fender liners (both in the front and at the firewall.

I expect the same will happen when I try 4 ZCP 19s on all 4 corners later in 2011, but at least it won't understeer.

As Lucid states, PS2s get a heck of a workout up front, so if you are using those or any street tire, the square setup with be best used if you swap front to back each track day.
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      02-11-2011, 11:47 AM   #7
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Quote:
Originally Posted by davem3fan View Post
BTW: I think understeer is a very minimal issue in stock E9X M3s anyway.
This seems to be the consensus. I suspect it has something to do with the front dynamic camber curve.
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      02-11-2011, 01:47 PM   #8
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Quote:
Originally Posted by lucid View Post
This seems to be the consensus. I suspect it has something to do with the front dynamic camber curve.
Yeah the E90 front suspension was a big leap forward there. I remember seeing an article on it but of course I can't find it now.
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      02-11-2011, 01:51 PM   #9
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I think the answer to your initial question regarding the choice between square vs. staggered wheel/tires setups depends on many things, only ONE of which is tire longevity. I think what's more important is the alignment. Slapping a square setup on a car with stock everything else, including alignment, will result in increased oversteer (becasue you'll be adding grip to the front via larger contact patch). Even if this is minimal, it affects the handling characterisitics, and by associatation, the manner in which you must drive your car. When I was faced with this very conundrum, I chose to maintain a stagered setup, although I increased the front AND rear contact patches slightly. The wheels and tires I selected are considerd a "+1" setup (front and rear) over stock. The end result is not much improvement, so if I were to do it all over, I would still go with a staggered setup, except go even wider. Your 265/35/18F and 285/30/18R (assuming you meant 30 and not "50") sounds a little better than my 255/35/18F and 275/35/18R, although I suggest 295/30/18 in the back.

PS, by "front dynamic camber curve", do you mean scrub angle? There is an article on this in the latest Car & Driver... it mentions how advances in McPherson strut technology has greatly reduced one of it's biggest shortcomings, mainly with respect to torque steer, but affects other aspects as well.
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      02-11-2011, 02:03 PM   #10
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A 285/30-18 or 295/30-18 on the rear also has the same effect as changing the final drive on a 6MT from 3.85:1 to about 4.0:1. Not a bad side benefit, at least not if you're at a track that doesn't use 2nd gear. A 305/30-18 or 315/30-18 is going to start approaching the same diameter as the 275/35-18.
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      02-11-2011, 02:35 PM   #11
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I'm a big fan of being able to rotate front to back as you wear out the outer edge of your front tires more, and the inner edge of your rear tires. You can rotate left to right as well with most track oriented tires. This has cost savings benefits that will vary by owner.

If you want more rubber out back then go staggered as the 10.5's will accommodate more rubber properly. There's no other way to do it.
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      02-11-2011, 02:57 PM   #12
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Quote:
Originally Posted by Richbot View Post
Yeah the E90 front suspension was a big leap forward there. I remember seeing an article on it but of course I can't find it now.
Right. When this car came out, many people assumed that it would have the same kind of understeer dialed in as the E46 M3 for instance.

Quote:
Originally Posted by M3V8Driver View Post
When I was faced with this very conundrum, I chose to maintain a stagered setup, although I increased the front AND rear contact patches slightly. The wheels and tires I selected are considerd a "+1" setup (front and rear) over stock. The end result is not much improvement, so if I were to do it all over, I would still go with a staggered setup, except go even wider. Your 265/35/18F and 285/30/18R (assuming you meant 30 and not "50") sounds a little better than my 255/35/18F and 275/35/18R, although I suggest 295/30/18 in the back.
I agree. Also, one should keep in mind this car has a good deal of wtq, so giving up rubber one could potentially have in the rear for the sake of reducing understeer might not be such a good trade-off in terms of being able to get on power on corner exit.

Quote:
Originally Posted by M3V8Driver View Post
PS, by "front dynamic camber curve", do you mean scrub angle? There is an article on this in the latest Car & Driver... it mentions how advances in McPherson strut technology has greatly reduced one of it's biggest shortcomings, mainly with respect to torque steer, but affects all other aspect as well.
I believe you are referencing scrub radius, which is the distance between the steering axis and the center of the contact patch of the tire.

Dynamic camber is the change in camber due to compression. In this car, my assumption is that there is significant decrease in camber (as in more negative camber) with compression.
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      02-11-2011, 09:08 PM   #13
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Thanks everyone for the wonderful feedback, I feel i will go for a square set up since at my level I feel slight understeer in this car. I feel that as you get in the more advanced groups people like to push harder and start finding the tail being happier.

I have another question. With a square 10 inch rim, what will be the cons of running 265/35/18 front and 285/35/18 rear? (I can potentially made a staggered set up if i decide in the future right?...opinions?)
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      02-11-2011, 09:38 PM   #14
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Aside from the tire being a little stretched in the front (and giving up some grip relative to a 275/35-18) I don't really see a downside.
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      02-11-2011, 09:43 PM   #15
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Dont see an issue, you could always do 275F/285R as well.
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      02-11-2011, 10:19 PM   #16
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I went square... got the APEX ARC-8 wheels 18x10 all around and now about to get the Nitto NT05 275/35/18...

The wheels look great .. and *light* .. Can't wait to put them on!
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