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[shuotong]

Looking to purchase a new set of lightweight staggered rims for summer / track use, unfortunately I'm short on money and CDN dollar being so cheap now, I can only go for Canadian wheels, the only problem is I couldn't find any 17x9 or even 17x8.5 sizes for rear, I'm pretty much stuck with 18s.

I wonder how much difference would it make, performance wise, comparing 17' to 18'? Not only the 18's are heavier, but the barrel is also larger. Even assuming the barrel weights the same, the barrel of 18's has 12% more rotational inertia than 17's.

However, since lightweight wheels are... lightweight, I doubt their role in the overall rotational inertia of the entire wheel including tire, since tires are heavier than rims already and seat further from the rotation centre.

Continental ECS, 255/40/17 or 255/35/18 (according to tirerack): 23lb
typical flow formed 17x9: ~17lb
typical flow formed 18x9: ~19lb

Can anyone with 17's wheels tells me if you can feel any improvement? Any input is appreciated.

The attached image is Fast FC04 18 inch wheels, the model I'm considering to buy, on metallic grey E90 (colour of my car).

[BM3Rrrr]

I believe you also need to factor in the coriolus effect and the earth gravitational pull of 9.807 m/s² whenever deciding between 17's and 18's

[shuotong]

Originally Posted by BM3Rrrr

I believe you also need to factor in the coriolus effect and the earth gravitational pull of 9.807 m/s² whenever deciding between 17's and 18's

You only factor Coriolis effect on much longer intervals, not considerable for wheels
Tbh, I have oem 17 and 19 and they feel quite different.

[avocet]

Originally Posted by shuotong

However, since lightweight wheels are... lightweight

I think this pretty much sums it up... I recently went from style 230 19" rims to a square 18" ARC 8 set up and holy cow.

[ttthai]

Originally Posted by avocet

I think this pretty much sums it up... I recently went from style 230 19" rims to a square 18" ARC 8 set up and holy cow.

I went from style 230 19s to square arc-8 17s and I also experience holy cows. I would recommend 17s if you can. Tires also end up being cheaper and daily ride comfort is much much better. To be fair I have no experience with 18s. Just make sure you'll be okay with the barrel size in case you have any BBK plans in the future.

[avocet]

I dug this up. Remembered reading this some time ago. Although a very different chassis, I think the take away is the same. And as relevant today as then.

https://www.caranddriver.com/feature...-wheels-tires/

[shuotong]

Originally Posted by ttthai

I went from style 230 19s to square arc-8 17s and I also experience holy cows. I would recommend 17s if you can. Tires also end up being cheaper and daily ride comfort is much much better. To be fair I have no experience with 18s. Just make sure you'll be okay with the barrel size in case you have any BBK plans in the future.

Wouldn't go larger than my current 335i brakes, I can hardly find 18' winter tires in stock within the performance winter category, or the prices are usually prohibitive💰
The road surface is bad here as well... ride comfort might be a thing in shitty downtown road.

[shuotong]

Originally Posted by avocet

I dug this up. Remembered reading this some time ago. Although a very different chassis, I think the take away is the same. And as relevant today as then.

https://www.caranddriver.com/feature...-wheels-tires/

I saw this as well, too bad they didn't get W rated 17's as Goodyear sent them the wrong tire. Usually taller sidewall means less support, but that I think also has something to do with tire models and speed ratings, as my summer sidewall felt much firmer than winters, even they're same in size. This car and driver journal also mentioned it.
I guess summer tires has firm sidewalls to minimize the impact of the taller tires? I have all seasons on another family car in 235/45/18, similar side height than E90's 225/45/17, but I can feel that sidewall is much softer.

[Sgop335]

I recently put 18lbs 17" wheels from Tirerack. 17x8 and 17x9 for the 535i. Its fine but I should have gone with 18s. The weight increase is not much, also I found the "sticky" tire selection is better for 18 than 17...

Not even a question...square 17s is the obvious answer here.

Why on earth anyone would want to run a larger/heavier/more expensive wheel/tire setup for track purposes is beyond me.

Originally Posted by Sgop335

I recently put 18lbs 17" wheels from Tirerack. 17x8 and 17x9 for the 535i. Its fine but I should have gone with 18s.

Well, obviously...those cars are massive. Plus, on the street, it obviously matters less anyway.

[Sgop335]

Originally Posted by FCobra94

Well, obviously...those cars are massive. Plus, on the street, it obviously matters less anyway.

Looks like everything is obvious to you lol
If you read a litl further i would have picked 18 for the tire selection.

[shuotong]

Originally Posted by FCobra94

Not even a question...square 17s is the obvious answer here.

Why on earth anyone would want to run a larger/heavier/more expensive wheel/tire setup for track purposes is beyond me.

I still prefer staggered setup on track so I can have more stable rear.
Of course this is personal preference, some feel comfortable with squares.

Using 17 is definitely the rational choices for me but 17 staggered is expensive, the only option is apex arc 8 17" priced at $1514 (thanks to the exchange rate) and Fast FC01 18" is only $886. Which is why I'd need some advice if 18 are much worse or just okay comparing to 17.

[shuotong]

Originally Posted by Sgop335

Looks like everything is obvious to you lol
If you read a litl further i would have picked 18 for the tire selection.

Lucky I do have all the tire models I want stocked in 17" section, it's probably because 5 series has larger wheels than E90 so you don't see much choices for 17 inch.

[Emilime75]

Originally Posted by shuotong

I still prefer staggered setup on track so I can have more stable rear.
Of course this is personal preference, some feel comfortable with squares.

Going squared doesn't have to mean going narrow in the rear. Going squared with wider fronts typically reduces/eliminates understeer. The aim is for balance, a car that doesn't under/oversteer much more than the other.

[shuotong]

Originally Posted by Emilime75

Going squared doesn't have to mean going narrow in the rear. Going squared with wider fronts typically reduces/eliminates understeer. The aim is for balance, a car that doesn't under/oversteer much more than the other.

Yes, however I have bad experience with 235/265, the steering feels less agile than 225/255 on same tire model Michelin PSS. With 225/255 I still experience oversteer more often, I have a 328i with MT and zero front toe, not sure if this setup helps the front to stay on ground.
Staggered doesn't mean better, but I kinda like it.

Originally Posted by Sgop335

If you read a litl further i would have picked 18 for the tire selection.

What are you finding in an 18 that you cant in a 17?

Originally Posted by shuotong

Yes, however I have bad experience with 235/265, the steering feels less agile than 225/255 on same tire model Michelin PSS. With 225/255 I still experience oversteer more often, I have a 328i with MT and zero front toe, not sure if this setup helps the front to stay on ground.
Staggered doesn't mean better, but I kinda like it.

Just because it "feels more agile" likely doesn't correspond to faster track times. Overall grip should be the main goal here. If going with such a setup means that your car no longer feels "balanced" than you likely have some tweaks to make on the rest of the car.

Current camber settings front + rear? Spring rates/dampers? Etc.

Originally Posted by shuotong

Using 17 is definitely the rational choices for me but 17 staggered is expensive, the only option is apex arc 8 17" priced at $1514 (thanks to the exchange rate) and Fast FC01 18" is only $886. Which is why I'd need some advice if 18 are much worse or just okay comparing to 17.

What do you mean by "just ok?" It sounds like you're not really interested in making this a holistic approach, but rather, just care more about owning a set of "track wheels + tires." Since thats the case, just go with whatever is cheapest...likely not worth the extra cost for your intended pupose anyway.

Also, even if you go with square wheels doesn't mean you also have to go with square tires. Staggered tires on square wheels, within reason, would likely work here too. Again, budget is your goal here so focus on that first.

[shuotong]

Originally Posted by FCobra94

What do you mean by "just ok?" It sounds like you're not really interested in making this a holistic approach, but rather, just care more about owning a set of "track wheels + tires." Since thats the case, just go with whatever is cheapest...likely not worth the extra cost for your intended pupose anyway.

Also, even if you go with square wheels doesn't mean you also have to go with square tires. Staggered tires on square wheels, within reason, would likely work here too. Again, budget is your goal here so focus on that first.

If you take a look at OP, I actually need a summer + track set (not dedicated track day set) so steering feel does matter to me. I used my old rims for winters now.
But you're absolutely right , I should just go with 17 squares to both fit the budget and reduce weight. Still, I'd like to keep all tires at 225-235 range to keep the steering feel comfortable on street, my steering wheel already got heavier on summer tires compare to all season.
I do realize I only want to have fun on track, not setting new lap times so why not just choose with the lightest and most cost effective option.

[Canadiesel]

I found a set of staggered style 286 which are 17s off of a 328i sport package. Personally I prefer this over the staggered 18s I was running prior.

[shuotong]

Originally Posted by Canadiesel

I found a set of staggered style 286 which are 17s off of a 328i sport package. Personally I prefer this over the staggered 18s I was running prior.

That's a very rare set, congratulations. I didn't realize how hard it could be to find staggered 17 in Canada until I tried.