Experiences 17" vs 18"

Looking to get some dedicated summer wheels for my 325i ZSP. Currently have OEM style 119 17 x 8. ET 47 at 23.1lbs each. Running 225/45/17 rubber.

Looking to go with NIche Targa (cast) in either a 17x8, et 40 at 22lbs each or 18x8 et 40 at 23lbs each. Pic attached of these in a 19" version.

I've read plenty of articles on unsprung weight and the physics of gyroscopic effect but would really like to hear from those with the same car that have actually made the switch from 17 to 18.

Specifically your thoughts/observations on ...
Tramlining
ride quality/roughness
handling changes
affect on acceleration

Assume all suspension is fresh and alignment is correct. With wheels of same proportions and weight (with exception of overall diameter), what effect will l the extra 1/2" of rim together with the 1/2" less tire have on the above topics.

Thanks guys.

NOTE: last summer I ran 2356/45/17 on existing wheels at the recommendation of the tire shop. THese were heavier than my stock rubber and had a higher sidewall and higher overall tire/wheel profile. WHile I would say they gripped beter under hard cornering, the acceleration, turn-in and overall handlilng was negatively affected by these tires. Sold them recently.

I have three sets of wheels (one 18, two 17s), and can say from experience that while there IS a difference, the perception of that difference seems to fade with the passage of time. Tire differences will also influence the "feel".
It`s not a tremendous difference, in any event, being that all wheels are relatively close in weight. Now, if you were switching to a *forged* wheel in the 17 or 18-pound range, THEN you would feel like you added a couple of inches to your Johnson....

The main difference is perception of turn-in, as a shorter sidewall will, in general, flex less. It doesn't affect actual corner speed, just the relationship between steering wheel angle and slip-angle of the tire tread.

Going from 18 to 17, I would say the ride is better.

Originally Posted by Fast Bob

I have three sets of wheels (one 18, two 17s), and can say from experience that while there IS a difference, the perception of that difference seems to fade with the passage of time. Tire differences will also influence the "feel".
It`s not a tremendous difference, in any event, being that all wheels are relatively close in weight. Now, if you were switching to a *forged* wheel in the 17 or 18-pound range, THEN you would feel like you added a couple of inches to your Johnson....

Well...one can always use and extra couple inches

I would expect that the 330 would be less likelyl to feel the difference as significantly as the 325. THose extra horses would be better suited to spin up the wheels.

Ideally, I would like to get lighter wheels but have found them either too expensive, not to my liking or there ae fitment issues.

THere are a number of "rotary forged" wheels out there that are priced reasonably in the 19-20lbs range but haven't foudn one that fits right or if it does, looks right.

I have to admit - and this is shallow of me- I am interested for the bling not the performance. I've got Hotchkis sways and will be going to Konis in the future so I'm not really interested in improving handling with larger wheels, just not degrading what I have.

Main issues would be reduced acceleration and ride quality followed by susceptability to damage.

It's funny, 'cause when I look at the car from the quarter angle, the 17s look great. Directly from the side, they look, meh...

I hate having to balance things...I want it all!

Originally Posted by djstrachan

Well...one can always use and extra couple inches

I would expect that the 330 would be less likelyl to feel the difference as significantly as the 325. THose extra horses would be better suited to spin up the wheels.

Ideally, I would like to get lighter wheels but have found them either too expensive, not to my liking or there ae fitment issues.

THere are a number of "rotary forged" wheels out there that are priced reasonably in the 19-20lbs range but haven't foudn one that fits right or if it does, looks right.

I have to admit - and this is shallow of me- I am interested for the bling not the performance. I've got Hotchkis sways and will be going to Konis in the future so I'm not really interested in improving handling with larger wheels, just not degrading what I have.

Main issues would be reduced acceleration and ride quality followed by susceptability to damage.

It's funny, 'cause when I look at the car from the quarter angle, the 17s look great. Directly from the side, they look, meh...

I hate having to balance things...I want it all!

The design and execution of a given wheel can trick the eye into appearing bigger than it actually is....I have a set of these wheels (Borbet Type E) in 17 x 8 inches. Note that the rims have a "straight-through" design, as opposed to a "stepped" type of rim. The straight-through type tend to look an inch bigger than the stepped design.....optical illusion, for sure....but an effective one. These Z3 wheels (also 17 x 8) give a similar appearance.

I have 17" style 68s and 18" VMR 710s. I don't notice much difference, but I don't drive the car hard very often. The 710s look a lot better though.

Originally Posted by Fast Bob

The design and execution of a given wheel can trick the eye into appearing bigger than it actually is....I have a set of these wheels (Borbet Type E) in 17 x 8 inches. Note that the rims have a "straight-through" design, as opposed to a "stepped" type of rim. The straight-through type tend to look an inch bigger than the stepped design.....optical illusion, for sure....but an effective one. These Z3 wheels (also 17 x 8) give a similar appearance.

I had read that in one of your other posts and agree. I've been limiting my search to that design. Of course, that also allows you to get 18" and looklike you've got 19s

I'm happy with the amount of tire below the rim and feel it is pretty optimal for all around ride/performance which is likely what the BMW engineers thought.

My car isn't really a city car. I live in the mountains of British COlumbia and do lots of highway trips on teh twisty (sometimes a bit rough) roads here. Performance and ride are important.

Originally Posted by chet31

I have 17" style 68s and 18" VMR 710s. I don't notice much difference, but I don't drive the car hard very often. The 710s look a lot better though.

I'm sure they do. I see you have a 330. LIkely that gives you less to worry about when choosing 17 or 18".

LIke I said, I really noticed the difference with the 235/45/17 rubber. It sucked the life out of my 325. Don't want to go down that road again though admittedly, that set up resulted in an overall wider wheel/tire combination with more wieght further from the hub than an 18" 40 profile tire would give.

IDeally, a through design wheel of 19-20lbs in an 18" for around $250.00 matched with the EVo tire should feel and perform well and look great.

There's less out there than I thought.

18" rims are for girls! You need 21"!

Originally Posted by car5car

18" rims are for girls! You need 21"!

You mean something like this?

As far as handling goes tires are going to make the bigger difference on a street car. if you have a pretty low/ stiff suspension set up like some of us going with a bigger wheel will make going over the bumpeties a little more harsh.

Originally Posted by TannerT

As far as handling goes tires are going to make the bigger difference on a street car. if you have a pretty low/ stiff suspension set up like some of us going with a bigger wheel will make going over the bumpeties a little more harsh.

Just a factory drop and suspension with Hotchkis Sways. Not overly stiff.

You can run just about anything you want then. Another thing to think about is accell while I am sure 18vs17 is minimal I can tell the difference when doing a pull between my 19s and 17s weight is also a factor in that but my 19s only weigh 45lbs with tires. The 17s feel much quicker and will chirp in 3rd if I am doing things right. My 19s barely spin in 1st.

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Originally Posted by TannerT

You can run just about anything you want then. Another thing to think about is accell while I am sure 18vs17 is minimal I can tell the difference when doing a pull between my 19s and 17s weight is also a factor in that but my 19s only weigh 45lbs with tires. The 17s feel much quicker and will chirp in 3rd if I am doing things right. My 19s barely spin in 1st.

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Acceleration is a definite concern with my 325. I don't have power to spare to run heavier wheels or com[ensate for the gyroscopic factor.

I's be willing to live with slightly more road "feedback" but not at the expense of any performance.

Ideally, lightweight 18" wheels (20lbs or less) woulf be the ticket. FInding what I like, that fits and I can afford...now that's the challenge.

Originally Posted by car5car

18" rims are for girls! You need 21"!

Go full pimp and get 700mm Campagnolo.

I sold my stock ZHP wheels which were 28 lbs and went to OZ 17's which were 18 lbs.

So it was like a 12 lb drop per wheel. I couldn't tell any difference in acceleration or handling, but did notice an improvement in steering feel.

So I think the angular momentum effect is exaggerated, and my back of the napkin calculation says the effect should be small, like losing an extra 50% in weight. So 12 lbs less unsprung weight is like 18 lbs of car weight, nothing you'd notice.

Originally Posted by Chris90

I sold my stock ZHP wheels which were 28 lbs and went to OZ 17's which were 18 lbs.

So it was like a 12 lb drop per wheel. I couldn't tell any difference in acceleration or handling, but did notice an improvement in steering feel.

So I think the angular momentum effect is exaggerated, and my back of the napkin calculation says the effect should be small, like losing an extra 50% in weight. So 12 lbs less unsprung weight is like 18 lbs of car weight, nothing you'd notice.

Really?! I would have thougth 12 lbs would make a huge difference especially after my own experience with the larger/heavier tires last summer and the obvious impact it had on acceleration and handling.

I found a spreadsheet done up by an engineer tht calculates the effects of size/weight etc on a rotating basis.

The added 1" of wheel does have an inmact on the amount of torque required to spin it up. It's not huge but definitely there.

AS far as my tire experience, I admit the overall diameter increased by approx 1" versus what a proper 18" set up would be and most of the added tire weight would be at the exterme edge of that diameter having the maximum negative impact on acceleration.

If only I knew somoeon with a 325i with 23lb 18" wheels so I could drive it and see for myself.

That can't be real . Omg I'm sick

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@ the horrible 740 pic

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Originally Posted by CamCrazy

@ the horrible 740 pic

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If you ever got that thing up to highway speed, you'd need all that space for the brake kit needewd to stop it!!

Lmao

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Originally Posted by djstrachan

Really?! I would have thougth 12 lbs would make a huge difference especially after my own experience with the larger/heavier tires last summer and the obvious impact it had on acceleration and handling.

I found a spreadsheet done up by an engineer tht calculates the effects of size/weight etc on a rotating basis.

The added 1" of wheel does have an inmact on the amount of torque required to spin it up. It's not huge but definitely there.

AS far as my tire experience, I admit the overall diameter increased by approx 1" versus what a proper 18" set up would be and most of the added tire weight would be at the exterme edge of that diameter having the maximum negative impact on acceleration.

If only I knew somoeon with a 325i with 23lb 18" wheels so I could drive it and see for myself.

It's much easier to spin a wheel than lift it. You can spin a wheel with one finger, and stop it with one finger, but it takes two arms to lift it. That's why it makes so little difference.

other things change when you go from 17" to 19", like the contact patch. That could explain what you felt.

Originally Posted by Chris90

It's much easier to spin a wheel than lift it. You can spin a wheel with one finger, and stop it with one finger, but it takes two arms to lift it. That's why it makes so little difference.

other things change when you go from 17" to 19", like the contact patch. That could explain what you felt.

I think the contact patch was a big difference with my tires last summer. They were an inch larger in diameter (kind of weird), higher sidewall and 10mm wider. That certainly coudl explain the sluggish turn in feel. THey did hold the road good under hard cornering though. As for that set-up's effect on acceleratino, the tire was wider, taller and heavier than my previous tire and most of the added wieght would be at the furthest point from the hub. Certainly that could have had an impact on acceleration.

What I'm proposing is for the weight of the tire and wheel assembly to be the same (or even lighter dependin on the weight of the lower profile tire) with the only change being the wheel's diameter.

As for the wheel diameter, It is easy to turn a wheel from the outside edge but much harder from teh center (hub). It takes more energy to turn an 18" wheel from the hub than a 17" wheel even if the overall weight is the same.

IN my 17 to 18 inch scenario, we are pushing about 65% of the wheels weight (approx. 15lbs) 1/2" further from the hub. That doesn't seem like much and it may not be.

Aside from acceleration and assuming turn in will be teh same or better with the 18" wheel...any thougths on road noise/ride with teh lower prodile tire? Even with my 17" wheels, ther is only about 2" of rubber between the rim and road.

18s are definitely rougher riding than 17s, but also the tire makes a big difference, which I notice everytime I swap my 17" snows for 17" summers.

Originally Posted by Chris90

18s are definitely rougher riding than 17s, but also the tire makes a big difference, which I notice everytime I swap my 17" snows for 17" summers.

Adding in the grooved roads here (heavy trucks) and some pretty rough stretches, I'm leaning towards the 17inchers even though I would like the bling of 18s.

With the Hotchkis adn later, Konis, I really don't need the 18" wheel to improve my
handling and the drawbacks of damage, and rougher ride don't seem to balance out.

I was leafing through some of my old R & T magazines and noticed how the pimped-out street cars all had the 18 or 19 inch wheels almost alwasy accompanied by a seriousl drop while the cars that were actuallyl used for track. auto cross etc all had less drop and higher sidewalls...likely running 17 or even 16" wheels.

There is a message in there. It's just not one I want to listen to