To Square or Not To Square

[EAGLE5]

Originally Posted by MisterSheep

Actually I would like to be focused on track performance because I have friendly competition with the GF's dad who has a E46 M3 stock with MPSS and would like to beat him M around the track. I do know that 17x9 would be the best set-up for this car, but there aren't many 17in wheels that I like that look good athestically on this car.

Well, these will probably make you go slower. If you want to go faster, you should follow a different path.

[MisterSheep]

Originally Posted by jsimon7777

Well, these will probably make you go slower. If you want to go faster, you should follow a different path.

Slower as in because they are heavier?

[jawn]

Originally Posted by MisterSheep

Slower as in because they are heavier?

Yarb.

[MisterSheep]

Originally Posted by jawn

Yarb.

The wheels aren't that much heavier over stock.. Maybe 2-4 pounds including tires. I thought the increase in grip would help the car that much more.

[jawn]

Originally Posted by MisterSheep

The wheels aren't that much heavier over stock.. Maybe 2-4 pounds including tires. I thought the increase in grip would help the car that much more.

2-4 pounds of unsprung mass that take longer to heat up. Also, changing to +33 from +48 will also lower your front roll center, so the front end will not want to change direction as quickly (which is fine on higher speed tracks, but not so great through chicanes).

[EAGLE5]

Plus more rolling resistance. Plus the weight of metal is farther to the outside. Drivers far better than most of us tested a lot on the track. 225 on 17x8 or 17x9 is the way to go. Unless you have a FI and/or down force.

[8R6]

245/255 staggered tires will be trivial to most street drivers. even more so if you're not boosted and putting down tons of power. 245/255 MPSS are sticky enough where it'll most likely be more than enough tire than the car needs, especially on stock suspension and just lowering springs.

i say go for it if you love those wheels and want to save a good chunk of money compared to buying everything brand new.

[Drakiv]

This is actually the setup I'm going to run with the exception of +35 on front. 245/35/18 and 265/35/18

[MisterSheep]

Originally Posted by Drakiv

This is actually the setup I'm going to run with the exception of +35 on front. 245/35/18 and 265/35/18

Lol and we were both a part of the group buy.

[strat61caster]

All these suggestions on fixing understeer just hurt me inside, they're bandaids like a ricer uses duct tape.

FYI big tires and stock power typically result in slower laptimes on track:
http://www.roadandtrack.com/car-cult...ransformation/

There's so many factors to wheel selection, weight, rolling resistance, and gearing contributed to the slower laptimes in the article above.

imo a deal for a deal's sake is never worth it, get what you want, it'll save time, heartache, and waking up your partner in the middle of the night as you toss and turn with regret. I couldn't stand the understeer as the car came off the factory floor, amplify it with a staggered setup? Gross.

[Summerwolf]

You can get rid of a lot of oversteer with a good alignment and application of power.

[Ashikabi]

Moar camber

[HachiRo]

There's a guy sellinng these sick matte blue reps of 57Xtremes in the Wheels and Tires Classifieds.

[pandamancer]

It isn't just unsprung mass(it is this also) but more so that it is added rotational mass. And a lot of that added rotational mass is at the outer edge of rotation(more tire mass than wheel mass).

Both of these factors matter, but in different ways. Do the classic figure-skating spinning physics routine and you can get a feeling for how inertia plays out as you shift the added mass outwards(from the axis of spin). Notice how much more effort it takes to BEGIN or STOP the spin with your arms outstretched vs. near your chest. Then do the same procedure holding full 1 gallon milk jugs.

The sprung vs. unsprung mass business somewhat boils down to how your suspension controls your wheels(and chassis, and consequently traction) during various loading and unloading events like taking turns over cobbled streets. To a reasonable extent, lowering weight(both sprung and unsprung) tends to make the wheels more controllable(increases traction), but dynamics being what they are, you have now changed the behavior of your sprung and damped system.

Rolling resistance(increased with wider tires and stickier compounds), gearing, and other factors come into play as well though I MIGHT argue to a different/lesser extent.

The truth of all of this, vehicles are dynamic systems and without complex modeling techniques or well-constructed(in a scientific sense) tests, the best thing you can do is make some educated guesses or buy what looks good to you.

Edit:
Some folks like CSG Mike have already done relevant and reasonable testing on this platform for you. Heed their advice if you are interested in more than just appearance.