i28 or i35 vert

[SteveAZ]

Originally Posted by TheSt|G

So really, the tires were the upgrade.

Transitioning from 17" to 18" wheels would reduce ride comfort, increase rotational inertia(meaning that a similar or even lighter wheel will act like a heavier wheel than a 17"), and in the extreme sense will reduce the contact patch. Think of drag radials on drag cars, small wheels for additional flex and squish off the line.

Not necessarily....Some hard data...

I had stock 17" wheels with 205 G/Y run flats and went to the setup in my sig. Front wheel/tire combo lost 13#s a piece and rear lost 10#s a piece.

Stock wheels were 26#s each and tires were also approx. 26#s
New wheels were 18#s and change each
New front tires were 21#'s each
New rear tires were 24#'s each
Front tires gained nearly an inch of contact patch
Rear tires gained about 2 inches of contact patch

New tire and wheel setup is noticably smoother and didn't notice much different in handling characteristics, maybe a tad more understeer but better traction...but now the car has new control arms and is at the shop to be aligned as I write this, so we'll see how it is after that.

[Obioban]

Originally Posted by SteveAZ

Not necessarily....Some hard data...

I had stock 17" wheels with 205 G/Y run flats and went to the setup in my sig. Front wheel/tire combo lost 13#s a piece and rear lost 10#s a piece.

Stock wheels were 26#s each and tires were also approx. 26#s
New wheels were 18#s and change each
New front tires were 21#'s each
New rear tires were 24#'s each
Front tires gained nearly an inch of contact patch
Rear tires gained about 2 inches of contact patch

New tire and wheel setup is noticably smoother and didn't notice much different in handling characteristics, maybe a tad more understeer but better traction...but now the car has new control arms and is at the shop to be aligned as I write this, so we'll see how it is after that.

I think you're missing the point. All else equal (same wheel design, same width, same rolling diameter, same tire model), a 17" wheel will weight less, will act (from a handling/acceleration/braking perspective) like a lighter wheel than an equal weight 18" wheel (because it has less rotational inertia), and ride better (more sidewall).

You may well have upgraded vs stock (easy on a car with heavy wheels and runflat tires), but that doesn't mean it wasn't a compromised upgrade as compared to what you could have done with 17" wheels.

[BrokenVert]

Originally Posted by Obioban

I think you're missing the point. All else equal (same wheel design, same width, same rolling diameter, same tire model), a 17" wheel will weight less, will act (from a handling/acceleration/braking perspective) like a lighter wheel than an equal weight 18" wheel (because it has less rotational inertia), and ride better (more sidewall).

You may well have upgraded vs stock (easy on a car with heavy wheels and runflat tires), but that doesn't mean it wasn't a compromised upgrade as compared to what you could have done with 17" wheels.

To put it simply - when a skater is looking to do spins they tuck their body in tight. This reduced your rotational inertia as Obioban said, making you spin faster with less energy input.

Thats what happens when you downsize to a 17" wheel - you tuck the main weight of the wheel (the barrel) in closer to the hub - just as a skater pulls their body in.







Anecdote time - I ran 18" wheels and PS2s for a very long time on this car. Then I cracked a wheel, said eff big wheels in NYC and went as small as I could go - 17" - its the best decision you can make from a handling perspective.


I also think that well designed 17" wheels look better on the 1er than bigger ones, but im weird, I like a bit of tire to show.

[SteveAZ]

Originally Posted by Obioban

I think you're missing the point. All else equal (same wheel design, same width, same rolling diameter, same tire model), a 17" wheel will weight less, will act (from a handling/acceleration/braking perspective) like a lighter wheel than an equal weight 18" wheel (because it has less rotational inertia), and ride better (more sidewall).

You may well have upgraded vs stock (easy on a car with heavy wheels and runflat tires), but that doesn't mean it wasn't a compromised upgrade as compared to what you could have done with 17" wheels.

No....I wasn't missing the point at all, I completely understand the concept. I've done enough motorcross and bike racing to know exactly what effect rotational mass has on accelleration and handling the futher it gets from the hub and the pros and cons of it.

You missed my point. Roundel335 said that he switched from his stock 17s with run craps to 18s and no run craps and got improved handing and ride comfort. TheSt|g questioned how that was an upgrade and 335 explained. Stig said he upgraded tires then....my point was no, it can be an overall upgrade and provided the data to support my statement...did I say it couldn't be improved upon...no. Did I say a 17" wheel of similar weight as that of my upgraded wheels wouldn't be a better choice...no. By dropping 8#'s from my wheels and only increasing the distance from the hub to the edge of my wheel by .5"s...you can't argue that's not an upgraded wheel. Throw in the fact that my tire's rotational mass was reduce on average of 3.5#s...I think my point and statement was pretty spot on for the example I gave. I also said "not necessarily", meaning not in all cases.

Add to that the fact that in removing the RFTs from a car that was designed to have them, with a 17" wheel the concern of increased sidewall deflection over that of an 18" may have even more of an impact on handling if that is your biggest concern. So, certainly a trade off and one I certainly gave some consideration to.

...and if we're going to start dismissing people's upgrades because it wasn't the optimal upgrade...well then very few people on this site have upgraded their cars at all, because unless money is no object for you, there is almost always something better to be had.

So basically, yes you are right and I fully understand that....but so was I

Originally Posted by BrokenVert

To put it simply - when a skater is looking to do spins they tuck their body in tight. This reduced your rotational inertia as Obioban said, making you spin faster with less energy input.

Thats what happens when you downsize to a 17" wheel - you tuck the main weight of the wheel (the barrel) in closer to the hub - just as a skater pulls their body in.



Anecdote time - I ran 18" wheels and PS2s for a very long time on this car. Then I cracked a wheel, said eff big wheels in NYC and went as small as I could go - 17" - its the best decision you can make from a handling perspective.


I also think that well designed 17" wheels look better on the 1er than bigger ones, but im weird, I like a bit of tire to show.

Brokenvert....your example isn't necessarily as cut and dried as you present it. A figure skater will start with their arms extended in order to gain leverage in initiating that spin, they will then pull their arms in as they speed up.

Yes, a lighter wheel will accellerate faster, but once at speed the weight of the wheel is of no consequence...as a matter of fact, the heavier wheel may even provide a smoother ride as it will have a greater mass and thus resist deflection that much more. In addition, a larger diameter wheel and tire (all else being equal) will also accellerate slower but definitely provide a smoother ride. Hence why all the serious Mtn bikers now ride 29ers instead of 26ers. Yes, they accelerate a bit slower, turn a bit slower, but they maintain momentum that much better, provide a smoother ride, and aren't as susceptable to slight terrain changes and deflection.

In my particular case...my "upgraded" wheels and tires are virtually the exact same outer diameter as stock, so in that regard I haven't changed anything. Do I notice a difference in accelleration...not really because it's too damn hard to keep the wheels from spinning...I probably should have gone with heavier wheels along with the wider tires

[Bmwbreed]

Originally Posted by Gray_Panther

Damnit we lost another one!

Well if its any consolation (eventhouhg im a 135 owner) I was on on you guys side. But I'm always routing for the under dog haha.

[Obioban]

Completely agree that you upgraded vs stock!

Originally Posted by SteveAZ

Yes, a lighter wheel will accellerate faster, but once at speed the weight of the wheel is of no consequence...as a matter of fact, the heavier wheel may even provide a smoother ride as it will have a greater mass and thus resist deflection that much more. In addition, a larger diameter wheel and tire (all else being equal) will also accellerate slower but definitely provide a smoother ride. Hence why all the serious Mtn bikers now ride 29ers instead of 26ers. Yes, they accelerate a bit slower, turn a bit slower, but they maintain momentum that much better, provide a smoother ride, and aren't as susceptable to slight terrain changes and deflection.

While that's true, all else equal, lighter unsprung mass lets you run softer springs and get equal contact patch control, which in turn allows you to run softer shocks (or shock settings)... which ride better. In next, of two properly set up cars, one with light wheels/tires, the other with heavy, the lighter setup car should ride better.

Mountain bikers bigger from bigger wheels because it gives them a larger rolling diameter so things that they hit have a smaller effect on the bike. Cars keep the same size rolling diameter as they change wheel sizes but upsizing and downsizing sidewalls.

[SteveAZ]

Originally Posted by Obioban

Completely agree that you upgraded vs stock!

While that's true, all else equal, lighter unsprung mass lets you run softer springs and get equal contact patch control, which in turn allows you to run softer shocks (or shock settings)... which ride better. In next, of two properly set up cars, one with light wheels/tires, the other with heavy, the lighter setup car should ride better.

Mountain bikers bigger from bigger wheels because it gives them a larger rolling diameter so things that they hit have a smaller effect on the bike. Cars keep the same size rolling diameter as they change wheel sizes but upsizing and downsizing sidewalls.

Agreed on all a counts and I understand that...I went off on a tangent replying to BrokenVert...it wasn't really relavent.

[BrokenVert]

Steve. It was a purposely simplistic model - much how we are taught that electrons travel in set orbits and how aerofoils produce lift by ventouri properties in highschool...


as in it was simplistic and somewhat flawed so people who dont have a great knowledge of physics will understand.

[SteveAZ]

Originally Posted by BrokenVert

Steve. It was a purposely simplistic model - much how we are taught that electrons travel in set orbits and how aerofoils produce lift by ventouri properties in highschool...


as in it was simplistic and somewhat flawed so people who dont have a great knowledge of physics will understand.

I guess I felt like I was being talked down to and for whatever reason I felt the need to show my understanding with relevent and irrelevent experience and got carried away....my bad.

[angler]

Who knew, that I would learn about electrons and aerofoils and other random stuff just by asking a simple question 135 or 128? Can't wait for my second semester.

[TheSt|G]

Originally Posted by BrokenVert

To put it simply - when a skater is looking to do spins they tuck their body in tight. This reduced your rotational inertia as Obioban said, making you spin faster with less energy input.

Thats what happens when you downsize to a 17" wheel - you tuck the main weight of the wheel (the barrel) in closer to the hub - just as a skater pulls their body in.

Anecdote time - I ran 18" wheels and PS2s for a very long time on this car. Then I cracked a wheel, said eff big wheels in NYC and went as small as I could go - 17" - its the best decision you can make from a handling perspective.

I also think that well designed 17" wheels look better on the 1er than bigger ones, but im weird, I like a bit of tire to show.

Looks like we finally agree on something.