[tranquility]

Not talking about tires, I guess it's gonna be Michelin PSS or whatever latest they have, but wheel size, tire size, spacers (or are they only for looks?). Is there a general formula or does it differ from car to car?

EDIT: It's an E89 Z4.

[Sedoy]

The formula is pretty, simple lightweight wheels (reputable forged) + lightweight sticky tires. Typically less unsprung weight leads to better performance, better ride, and gas mileage. Stay away from spaces if you want more performance, just get lower offset wheels.

[tranquility]

Originally Posted by Sedoy

The formula is pretty, simple lightweight wheels (reputable forged) + lightweight sticky tires. Typically less unsprung weight leads to better performance, better ride, and gas mileage. Stay away from spaces if you want more performance, just get lower offset wheels.

So, this has nothing to do w camber but just getting the wheel hub as close to the car as possible?

Is there a universal wheel size? I'm pretty sure tires that go w crazy over-sized wheels like 20" aren't optimized for performance, and probably need something 18" or lower?

[E90convert]

https://support.apexraceparts.com/hc...-Fitment-Guide

It’s a balance. The knobs you can turn are wheel width, offset (track width), diameter, and weight.

Increasing wheel width and diameter will increase lateral grip and tire response. Increasing offset and track width will increase stability but wear out suspension and bearing faster. In generaL, BMW M division does all this optimizing for you. Reducing unsprung mass is great if the wheel remains stiff. It increases wheel response, wheel control, and reduces inertia loss during accel/decel. You pay a lot for a little though.

I’ve personally gone with the Apex “street and track” using a staggered 19x9.5 and 19x10.5 with 255/275 tires. Really loving the grip, fitment, and look of the car.

[jmg]

Originally Posted by tranquility

Not talking about tires, I guess it's gonna be Michelin PSS or whatever latest they have, but wheel size, tire size, spacers (or are they only for looks?). Is there a general formula or does it differ from car to car?

You aren't talking about TIRES, but it's the single most important, complex, and ironically ignored mod that affects performance the most, on the street and the track. MPSS is definitely not the best one.

Everything else depends on if you are looking for straight line speed or cornering handling.

Wheels - You want the lightest possible. Size is dependent on what sidewall you need. Ideally you stick with factory overall rolling diameter, which would involve matching the correct tire profile ratio. For cornering, you want just enough sidewall to protect the wheel, but not give too much sidewall flex for cornering. For straight line drag racing, you want taller sidewall for more grip for launches.

Tires - There are tires that do well in drag, but don't do well in cornering. Then there are tires for endurance racing and sprint. Then there are tires for wear, and for grip. We could talk forever about tires. Street performance overall my choice would be the MPS4S * BMW spec.

Spacers - are largely for looks or to fix fitment issues with rubbing. They don't directly add to performance.

[tranquility]

Originally Posted by jmg

You aren't talking about TIRES, but it's the single most important, complex, and ironically ignored mod that affects performance the most, on the street and the track. MPSS is definitely not the best one.

Everything else depends on if you are looking for straight line speed or cornering handling.

Wheels - You want the lightest possible. Size is dependent on what sidewall you need. Ideally you stick with factory overall rolling diameter, which would involve matching the correct tire profile ratio. For cornering, you want just enough sidewall to protect the wheel, but not give too much sidewall flex for cornering. For straight line drag racing, you want taller sidewall for more grip for launches.

Tires - There are tires that do well in drag, but don't do well in cornering. Then there are tires for endurance racing and sprint. Then there are tires for wear, and for grip. We could talk forever about tires. Street performance overall my choice would be the MPS4S * BMW spec.

Spacers - are largely for looks or to fix fitment issues with rubbing. They don't directly add to performance.

I 'ignored' tires cuz I thought everyone would go to the gold std MPSS (or whatever variant, I'm not up-to-speed w what they're called now).

Ok, I just want everything set up for canyon carving, twisties. I couldn't care less about straight-line speed. Handling is the priority for me.

Tx for your above advice.

[jmg]

Originally Posted by tranquility

I 'ignored' tires cuz I thought everyone would go to the gold std MPSS (or whatever variant, I'm not up-to-speed w what they're called now).

Ok, I just want everything set up for canyon carving, twisties. I couldn't care less about straight-line speed. Handling is the priority for me.

Tx for your above advice.

I would definitely go for the MPS4S * BMW Spec if they have your size. Bridgestone RE71R are also great.

As far as wheels, 18 or 19 inch with a 30 to 35 aspect sidewall, as wide as you can fit no larger than 285 in the front, 295 or 305 in the rear. You lose a little bit of turn in the wider you go in the front, even through it’s ultimately more grip, so keep it at 285 or less. I would follow the apex fitment guide as well.

[G30M]

Originally Posted by tranquility

Not talking about tires, I guess it's gonna be Michelin PSS or whatever latest they have, but wheel size, tire size, spacers (or are they only for looks?). Is there a general formula or does it differ from car to car?

the formula is optimizing tire contact patch for the weight of the car. that is generally the width of the tire.

best overall performance is around the 40 aspect ratio (35-45 range depending on exact tire size).

you don't see race cars with skinny tires and giant bling wheels.

[gabriel.psd]

This thread is insanity.

Sweet lord.

[tranquility]

Originally Posted by gabriel.psd

This thread is insanity.

Sweet lord.

Tx for this useless post. What's so 'insane' about it? Don't bother replying. No idea why ppl feel the need to be rude jerks outta nowhere.

[gabriel.psd]

Originally Posted by tranquility

Tx for this useless post. What's so 'insane' about it? Don't bother replying. No idea why ppl feel the need to be rude jerks outta nowhere.

The insanity of this thread to me is the choice of making it in the first place, on a forum asking for a formula for wheels vs calling a wheel manufacturer to ask about wheels.

Pick a wheel brand, call them, tell them what car you have + mods (brakes, suspension parts) and they will have a recommended fitment for you.

For the other comments... 21", 30 side profile. Is this a donk? No. Literally a GT3 RS rear tire size.

PS: Universal wheel size?! Dude you've been on this forum since 2007. You're not new here.

PS PS: The guy telling you to go 285s in the front... that's why you don't ask a forum. The guy probably didn't even read you have a Z4. Maybe you have M4 now?

[tranquility]

Originally Posted by gabriel.psd

The insanity of this thread to me is the choice of making it in the first place, on a forum asking for a formula for wheels vs calling a wheel manufacturer to ask about wheels.

Pick a wheel brand, call them, tell them what car you have + mods (brakes, suspension parts) and they will have a recommended fitment for you.

For the other comments... 21", 30 side profile. Is this a donk? No. Literally a GT3 RS rear tire size.

PS: Universal wheel size?! Dude you've been on this forum since 2007. You're not new here.

PS PS: The guy telling you to go 285s in the front... that's why you don't ask a forum. The guy probably didn't even read you have a Z4. Maybe you have M4 now?

Well, isn't this better than your first post? If you're knowledgeable, isn't it better to impart what you know instead of just deriding others?

Anyway, I've never been into the modding scene, hence my thread. I'm not asking for a universal wheel size for all vehicle, ofc it's pertaining to what's ideal for my car.

[G30M]

Originally Posted by tranquility

Not talking about tires, I guess it's gonna be Michelin PSS or whatever latest they have, but wheel size, tire size, spacers (or are they only for looks?). Is there a general formula or does it differ from car to car?

EDIT: It's an E89 Z4.

so the E89 Z4 has around 200kW and weighs around 1500kg with 53%/47% front to rear weight distribution

the weight is very similar to a supra. they have on average 265 35 18 tires all round. but they have a lot more power. wider tires and bigger wheels give rotational mass and if you are underpowered the engine can't spin the things and you lose acceleration and because of the rotational inertia braking is compromised.

i'd say 225/40 or 235/35 17 or 235/40 17 with rims that are 8" wide and as light as possible

[G30M]

i have a subaru wrx with 1500kg and 200kW 55/45 weight dist

this is my experience 225 45 18 vs 245 40 18 vs 235 45 17
225 18 on 7.5" rims = harsh and understeer.
225 18 on 8.5" = harsher but driving on rails.
245 18 over tired, steering won't turn, car feels sluggish but best corner speed
235 45 17 on 7.5 is bliss so comfortable, steering great, but bcos wheel is narrow turning is not sharp.

what is your stock tire size?

[G30M]

[tranquility]

Originally Posted by g21

i have a subaru wrx with 1500kg and 200kW 55/45 weight dist

this is my experience 225 45 18 vs 245 40 18 vs 235 45 17
225 18 on 7.5" rims = harsh and understeer.
225 18 on 8.5" = harsher but driving on rails.
245 18 over tired, steering won't turn, car feels sluggish but best corner speed
235 45 17 on 7.5 is bliss so comfortable, steering great, but bcos wheel is narrow turning is not sharp.

what is your stock tire size?

18s 225 front and 255 rear.

[G30M]

is that stock?

looks easy - just make the front tire the same as the rear and you are optimized.

[tranquility]

Originally Posted by g21

is that stock?

looks easy - just make the front tire the same as the rear and you are optimized.

Yes, that's the stock setup, but, really, there must be a reason why they have a staggered setup from the factory as they easily could've just have a square one.

[HighlandPete]

Originally Posted by tranquility

Yes, that's the stock setup, but, really, there must be a reason why they have a staggered setup from the factory as they easily could've just have a square one.

Optimised by BMW for a sporty but safe drive.

Staggered make it safer, as it typically dials in a bit of understeer as you work the RWD chassis harder. Less likely to catch you out, as there's also a bit more lateral grip at the rear.

I've run a 3-series with both square and staggered setups on the same diameter wheels, 8" rims, with 225 all corners and 225/255 on 8/8.5" rims. The 225 square setup was a more balanced chassis, the staggered, you could feel the slight understeer when pressing on.

[G30M]

Originally Posted by tranquility

Yes, that's the stock setup, but, really, there must be a reason why they have a staggered setup from the factory as they easily could've just have a square one.

for understeer, and more aquaplaning resistance on the front (not rear). not for speed.
unfortunately
over 100mph my 340 (err it's heavy, 1900kg) does not brake with 225 tires. car feels like it will fly off the road with pressure on the brake pedal

if you are RWD i'd go 235 or 245 front at least. i don't know if it will fit a 255 hence 235/245.

[HighlandPete]

Originally Posted by g21

if you are RWD i'd go 235 or 245 front at least. i don't know if it will fit a 255 hence 235/245.

If road driving at 'normal' day to day speeds, why sacrifice sharper steering with a baggy tire, assuming the OP is on the OE rim?

Wider rims, then we are changing the whole dynamic set up.

Remember BMW's OE setup is a compromise for a wide range of driving characteristics. Unless you are prioritising a particular characteristic, (you know why you are doing it), you are just experimenting and moving the compromises.

[G30M]

Originally Posted by HighlandPete

If road driving at 'normal' day to day speeds, why sacrifice sharper steering with a baggy tire, assuming the OP is on the OE rim?

Wider rims, then we are changing the whole dynamic set up.

Remember BMW's OE setup is a compromise for a wide range of driving characteristics. Unless you are prioritising a particular characteristic, (you know why you are doing it), you are just experimenting and moving the compromises.

with very similar weight distribution, and RWD

M340i 225/255
M440i 245/255
M3/M4/M3T 275/285
all these cars above have similar weight around 1800kg and same weight distribution

based on that I'd say 245/255 is the sweet spot for OP
i was going to suggest 235/245 but OP already has 255s