[pits200]

Just this year I decided it was time to make the jump to summer and winter tires. Im using my stock rims at 225/45/17s for my winter setup. Now as spring is a few months away I am looking at options for my 18 inch setup.

Now I am performance oriented while looks are somewhat secondary. It seems a lot of people on here also have that priority.

Now I'm just curious with the xi why I see some people going with like 255 or 275 tires on an xi? I just don't see the advantage vs going with my setup of 225/40/18 which can handle the power on a launch.

I'm just curious why some people go so wide with the xi?

[gaberoll]

-wider tires for wider rims
-more traction for when you're interested in more than just driving in a straight line
-etc etc

[UltraRacer13]

for me I have to admit it is mostly for looks. The car looks more aggressive from behind with the wider tires.

[pits200]

Originally Posted by gaberoll

-wider tires for wider rims
-more traction for when you're interested in more than just driving in a straight line
-etc etc

Funny post, not sure what other etcs there are for wider tires. Besides the possibility for slightly better handling, even that is somewhat debatable.

[pits200]

Originally Posted by UltraRacer13

for me I have to admit it is mostly for looks. The car looks more aggressive from behind with the wider tires.

Ya, this was pretty much the only reasoning I could think of. I have 10 and 15mm spacers and with my skinny tires pushed out, it looks a little strange. Oh well, I was just wondering and wanted to start a new topic since the xi section is like wnba of this forum.

[Er3k]

I had 225/40/18's and you are correct, they can handle the launch. But I get a cleaner launch with the 275's out back. My car feels more planted to the ground, even on wet pavement with staggered setup. Tried both but I feel that staggered feels a lot better performance wise. I also have et 30 front & back, not sure if that makes a difference or not.

[gaberoll]

Originally Posted by pits200

Funny post, not sure what other etcs there are for wider tires. Besides the possibility for slightly better handling, even that is somewhat debatable.

you're right, tire width has absolutely no proven effect on handling. silly me.

[AllydNYC]

- Greater surface area that makes contact to the road
- Greater choices in tires because of more performance oriented sizes
- ?????

You will get additional understeer when going with a staggered setup. Square setup is better.

[pits200]

Originally Posted by AllydNYC

- Greater surface area that makes contact to the road
- Greater choices in tires because of more performance oriented sizes
- ?????

You will get additional understeer when going with a staggered setup. Square setup is better.

I'm not discounting that wider tires have slightly better handling characteristics. I'm saying that it seems a lot of people feel that trade-off is worth it. The tire width has probably the least effect vs suspension, brand of tire, psi, etc...

I am saying, when it comes down to it, the sole reason I can see someone getting wider tires is when they're maxed out in suspension mods.

Wider Tire Cons:
1.) More Expensive
2.) Harsher ride
3.) More susceptible to hydroing
4.) Heavier
5.) Higher rolling resistance so worse gas mileage

Pros:
1.) Better handling
2.) Looks better

[Sam335ix]

Here is mine

1- Looks, yes I am shallow so bite me
2- Looks, the front of the e90 is aggressive but the rear of the sedan is made for pussys.
3- Looks, the wider the rear looks, the better car looks... its like a girl with a nice hard round ass but not big girl butt... you get my drift?
4- I always felt like the wider the tries the better the grip I have on the road but that is for dry surfaces only to what I hear because I keep hearing stay away from wide tires for winter which that is why I have my winter set up for.

Did I mention looks? Yeah so there you have it

[NiVeDh]

Originally Posted by AllydNYC

- Greater surface area that makes contact to the road

This is not entirely true. The total surface area of the contact patch remains about the same, but the shape is different.

[catcher22]

No hard facts but I feel I have significantly less under steer with my 245 squares.

[AllydNYC]

Originally Posted by NiVeDh

This is not entirely true. The total surface area of the contact patch remains about the same, but the shape is different.

[pdips]

i have 245's in the front, 275's in the back...more for looks then handling and i actually handle better with 225's squared

[DMafia46]

Originally Posted by pits200

I'm not discounting that wider tires have slightly better handling characteristics. I'm saying that it seems a lot of people feel that trade-off is worth it. The tire width has probably the least effect vs suspension, brand of tire, psi, etc...

I am saying, when it comes down to it, the sole reason I can see someone getting wider tires is when they're maxed out in suspension mods.

Wider Tire Cons:
1.) More Expensive
2.) Harsher ride
3.) More susceptible to hydroing
4.) Heavier
5.) Higher rolling resistance so worse gas mileage

Pros:
1.) Better handling
2.) Looks better

Harsher ride really? Rolling resistance that depends alot more on the tire , but you can get more economy oriented tires but then those are noisy and ull understeer into a ditch

[pits200]

Originally Posted by DMafia46

Harsher ride really? Rolling resistance that depends alot more on the tire , but you can get more economy oriented tires but then those are noisy and ull understeer into a ditch

Well considering if you have two exact same brand tires, the one with more contact area is going to have more drag, basic physics.

[nailer335]

Originally Posted by pits200

Ya, this was pretty much the only reasoning I could think of. I have 10 and 15mm spacers and with my skinny tires pushed out, it looks a little strange. Oh well, I was just wondering and wanted to start a new topic since the xi section is like wnba of this forum.

Hahahahahahaha so beautifully articulated

[Doyle]

Hahaha, WNBA. Nice.

However, there is alot of misinformation in here and good info that is getting ignored.

1) Does the xi need wider tires? I have broken traction on all 4 wheels at the same time on 245 RE11's square. I could go wider with a similar compound, or see how a stickier compound in the same size fared. Also, narrow tires have less mass to absorb heat. Meaning that if you track your car, narrower tires tend to grease up quicker than wider ones (all things being equal). Especially with the pig of BMW that we drive!

2) Contact patch size - All things being equal, the only thing that will change the size of the contact patch is tire pressure. Think about it. Tire pressure is measured in pounds per square inch. If you are running 205s or 305s, and they are inflated to the same pressure, you will still have the same normal force. So, since the psi will "resist" the normal force in the same manner, it will distribute the force over the same size contact patch. If you raise the tire pressure, the tire will be able to support more weight on a smaller contact patch. Hence, why you see drag cars running super low tire pressures (to get large contact patches). Different section widths, for the same psi, will only change the shape of the contact patch.

3) Why does the xi need to go wide? Because all the fastest AWD cars on the road have. the Sierra Sierra car runs 295 square.

4) Understeer v. oversteer. I've said it before, but it bears repeating. A: If you don't track your car, understeer v oversteer should mean nothing to you. You shouldn't be reaching the car's limits on public roads. If you are, chances are it is mostly driver error. Stop worrying about it and creating a dozen threads about which bar is best. Just buy a damn bar. If you really are concerned about. It's called google, man. Sorry. B: You tune the chassis before you land on tire widths. Springs, bars, alignment, track width, and tire pressures will all have a HUGE impact on balance. Tire width is only a single factor. C: There are three sections to every corner - entry, apex, and exit. Understeer can occur at any point. Once you determine what point the car understeers, you can then correct it. Staggered tires tends to increase entry understeer. That can be countered with ride height or alignment adjustments (but more likely slower entry speeds).

The bottom line is, you aren't stuck with just one tire choice. Pick one suited to your needs and be happy. DD? Stop worrying and buy the longest lasting tire you can. DD with some drag time? 555r/Mickey Thompson Street. AutoX/Track? Go as wide as you can and as sticky as you can. Pay to play, brothers.

[BAL278]

"It's hit to be square" ... Especially on our xi's.. I think if you run 18's on a lowered car you can get away with 255's all around which is my plan.. But not before I do a rear sway bar/bushings/ and shocks

[M3E46M]

Originally Posted by pits200

I'm not discounting that wider tires have slightly better handling characteristics. I'm saying that it seems a lot of people feel that trade-off is worth it. The tire width has probably the least effect vs suspension, brand of tire, psi, etc...

I am saying, when it comes down to it, the sole reason I can see someone getting wider tires is when they're maxed out in suspension mods.

Wider Tire Cons:
1.) More Expensive
2.) Harsher ride
3.) More susceptible to hydroing
4.) Heavier
5.) Higher rolling resistance so worse gas mileage

Pros:
1.) Better handling
2.) Looks better

Just changed from Stock 18s w/RFT to VMR V701 19 in - staggered setup 8.5 wide in front 9.5 back with Hanhook v12 tires (NON RFT)

1. True
2. False (depends how much PSI u have) at 38 PSI in front feels smoother.
3. Hmm..... maybee if you are going 100 MPH over puddles.. but Hanhooks handle better then stock in this department.
4. False - I lost 5 pounds of weight per wheel and tire in front and 4 pounds per wheel and tire in back (also depends what u buy). I actually took a scale and weight the wheels while changing.
5. False don't see any MPG difference. If you under inflate the tire then maybe. Make sure your tires are inflated properly.

So my conclusion is I lost 18 Pounds of unsprung weight which is a lot and gained more traction. The wheel is 9.5 wide in rear that's 1 inch wider than stock. WIDER = MORE POWER TO THE GROUND.

ALSO NOTE: per SWIFT springs website about unsprung weight:

"For example, lightening the suspension by 2 lbs per spring will actually be equivalent to removing 40-56lbs of equipment from the interior.

The difference there depends on how heavy are the wheels and tires, and reasons like lower profile tires."

I don't believe it's that much, but I can tell you that with stock sport suspension, and these lighter wheels my car handles a 100% better.

[pits200]

Originally Posted by labedra

Just changed from Stock 18s w/RFT to VMR V701 19 in - staggered setup 8.5 wide in front 9.5 back with Hanhook v12 tires (NON RFT)

1. True
2. False (depends how much PSI u have) at 38 PSI in front feels smoother.
3. Hmm..... maybee if you are going 100 MPH over puddles.. but Hanhooks handle better then stock in this department.
4. False - I lost 5 pounds of weight per wheel and tire in front and 4 pounds per wheel and tire in back (also depends what u buy). I actually took a scale and weight the wheels while changing.
5. False don't see any MPG difference. If you under inflate the tire then maybe. Make sure your tires are inflated properly.

So my conclusion is I lost 18 Pounds of unsprung weight which is a lot and gained more traction. The wheel is 9.5 wide in rear that's 1 inch wider than stock. WIDER = MORE POWER TO THE GROUND.

ALSO NOTE: per SWIFT springs website about unsprung weight:

"For example, lightening the suspension by 2 lbs per spring will actually be equivalent to removing 40-56lbs of equipment from the interior.

The difference there depends on how heavy are the wheels and tires, and reasons like lower profile tires."

I don't believe it's that much, but I can tell you that with stock sport suspension, and these lighter wheels my car handles a 100% better.

Overall, you are comparing stock vs aftermarket. Everyone knows the stock rfts are heavy pigs and aren't the best for ride quality.

My comparison was taking two exactly the same brand and model tires. So I was looking at michelin pilot sports but just in different widths. And that is what I was basing my knowledge from.

I went from stock 17s to aftermarket 18s and yes my ride felt better also. But I think we all know that was because I got rid of the rfts.

So your increase in ride quality wasn't from going staggered it was just because of the huge difference in tire quality.

As for hydroplaning, the quality of the tire will play a big role but if you have the same tire in 225 and 275, there will be a significant difference in how planted the car will be in the rain.

Man, people really hate to hear bad things about wide tires, ha.

Also, yes, you lost weight with the 19s being lighter but you do know that there is a negative effect of a larger size rim. You are moving mass further out from the center bore. This makes rotating mass harder to turn. Is it significant, no. But that is why most drag strip rims on cars like ours recommend 17s for optimal performance.

[Doyle]

Originally Posted by pits200

Overall, you are comparing stock vs aftermarket. Everyone knows the stock rfts are heavy pigs and aren't the best for ride quality.

My comparison was taking two exactly the same brand and model tires. So I was looking at michelin pilot sports but just in different widths. And that is what I was basing my knowledge from.

I went from stock 17s to aftermarket 18s and yes my ride felt better also. But I think we all know that was because I got rid of the rfts.

So your increase in ride quality wasn't from going staggered it was just because of the huge difference in tire quality.

As for hydroplaning, the quality of the tire will play a big role but if you have the same tire in 225 and 275, there will be a significant difference in how planted the car will be in the rain.

Man, people really hate to hear bad things about wide tires, ha.

Also, yes, you lost weight with the 19s being lighter but you do know that there is a negative effect of a larger size rim. You are moving mass further out from the center bore. This makes rotating mass harder to turn. Is it significant, no. But that is why most drag strip rims on cars like ours recommend 17s for optimal performance.

I think the issue here is that people aren't debating the same topic.

Pits---It sounds like you are focused mostly on the daily driving aspects of various tires widths (for a given tire). I think everyone else is coming from a "performance" viewpoint.

For daily driver, it absolutely makes sense to go with the narrowest, highest profile sidewall tire that you can get away with. BMW already did the math and it looks like 225/45/17 is it. It isn't sexy, flush, or meaty, but it is practical and frugal.

The second you start talking about "performance", compromises need to be made. Like my link above, haing 295's square is not unheard of. Hell, the winner or Tire Rack's OLOA ran 315 Super Sports square! It is up to the individual owner to decide what those compromises are. Fortunately, we are stuck with only one choice in tires!