Wheel/tire unsprung weight

[freesaints]

If one were to look at two wheel/tire combos - assuming the exact same outside diameter, same wheel and same tire brand - which would have the greater unsprung weight: smaller wheel (R16) but taller tire (245/45) or the larger wheel (R17) and shorter tire (245/40)?

Basically, is there more weight in the rubber or the wheel, going up or down in sizes.

[Cajundaddy]

It's not so black and white. You can find some very light weight large diameter racing wheels and some very heavy cast small diameter wheels. The only way to be precise is to weigh each.

If the tires and wheels are the same outer diameter and width, the wheels are the same mfg. there will probably not be a significant difference in unsprung weight.

[freesaints]

Yep, I hear you, that's why I was trying to control as many variables as possible (same wheel mfg, same tire make/model) and then see which adds more weight: 1" to the wheel or 1" inch of rubber. May still be some additional variables and ultimately there may not be much of a difference, but was curious as I looked to go up in wheel size with smaller tires (arguably better performance) or go down on wheel size with taller tires (worse performance but better aesthetics imo), but both directions controlling for OD.

[Bill Verburg]

Originally Posted by freesaints

If one were to look at two wheel/tire combos - assuming the exact same outside diameter, same wheel and same tire brand - which would have the greater unsprung weight: smaller wheel (R16) but taller tire (245/45) or the larger wheel (R17) and shorter tire (245/40)?

Basically, is there more weight in the rubber or the wheel, going up or down in sizes.

There's generally more weight in the tire
Here's and example that typifies the comparison
Yok A052
245/45x16 24.6" OD 21.4# inertial cost 20lb-ft
245/40x17 24.7" OD 21.4# inertial cost 21lb-ft

gearing cost slightly favors the 16 but not by enough to worry about

Fuchs 9x16 18.7#
Fikse Fuchs 9x17 16#

there are heavier and lighter examples of both though both are near the light end of the spectrum

net mounted inertial cost would be pretty close w/ the nod going to the 17s

Most people wouldn't be able to discern an acceleration/deceleration difference,

the 17s would have noticeably better lateral grip

[freesaints]

Awesome, that's what I was looking for. Thanks Bill.

[roblav]

"The 17s would have noticeably better lateral grip."

Why is that Bill? I will argue that it's entirely dependent on the tire.

[Bill Verburg]

Originally Posted by roblav

"The 17s would have noticeably better lateral grip."

Why is that Bill? I will argue that it's entirely dependent on the tire.

You'll notice the same tire, except for nominal spec, in the example

the 17 will run cooler at lower slip angles and can thus develop more grip

the 17 can even be fitted w/ a 9.5 which will develop even more grip, not so w/ the 16

[roblav]

But Bill, you implicitly assume that lower temperature is better and that wider is better. If the tire is designed to run at a relatively higher temp to maximize grip, then any temp under that design optimum temp will not be maximizing grip. I've had many days on the track where the tire temps just won't get high enough. Increasing tow out in front and toe in in rear is a method to increase tire temps by effectively increasing slip angles while driving straight. I've also experienced that narrower rims can increase tire temps on similar cool days... thereby increasing grip. These examples are why I argue that tire design effects the grip moreso than rim diameter and width. Your other comments and calculations wrt inertia are spot on. I can easily feel the difference between aluminum and magnesium wheels.

[Noah930]

To add to the variabilities in the OP's question, two different model tires with the same sizing specs often weigh different amounts.

[Bill Verburg]

Originally Posted by roblav

But Bill, you implicitly assume that lower temperature is better and that wider is better. If the tire is designed to run at a relatively higher temp to maximize grip, then any temp under that design optimum temp will not be maximizing grip. I've had many days on the track where the tire temps just won't get high enough. Increasing tow out in front and toe in in rear is a method to increase tire temps by effectively increasing slip angles while driving straight. I've also experienced that narrower rims can increase tire temps on similar cool days... thereby increasing grip. These examples are why I argue that tire design effects the grip moreso than rim diameter and width. Your other comments and calculations wrt inertia are spot on. I can easily feel the difference between aluminum and magnesium wheels.

you implicitly assume that lower temperature is better and that wider is better.

No, I stated a fact, though the difference is very small the lower slip angles which the 17s contact patch imparts will cause the tire to run cooler.
No I didn't imply that the width increases grip here, both tires have the same nominal width and construction. The difference is the geometry of the contact patch which will be slightly shorter and wider for the 17

Here are the tires in question



The nominal s/w is identical @245 but the installed s/w w is a tad wider as is the tread width on the 17, the wider tread w/ shorter length of the 17s is the critical thing here, the difference isn't huge but there is a difference

Here is the installed on the car comparison, w/ Fuchs 7 & 9x16 and Fikse Fuchs 8 & 9 x17
net net the 17s have a 2.3 lb-ft edge, this will not be detectable by most drivers, the 17s will also have a small but noticeable edge in lateral grip


In his situation either will run as hot as the other +/- in the same use , sure there are other cases where a tire will not run at design temp but that's beside the point and not what is discussed. And sure there are all sorts of ways that more heat can be put into the tire, examples are narrower wheels and toe changes but again that's not what was originally discussed or relevant to anything I posted. It's interesting that you mention it though because I notice that the Mercedes F1 cars now have a mechanism for the driver to change toe while on track, they use it to up tire temps when running behind the safety car.

[famoroso]

Originally Posted by Bill Verburg

T

Snip

Fuchs 9x16 18.7#
Fikse Fuchs 9x17 16#

Snip

What's the source for those figures?

I just weighed a 16x9 Fuchs, with centercap (no wheel weights) on a bathroom scale and got 16.4 pounds.

For grins, 951 16x8 Fuchs (no centercap, no wheel weights): 15.6 pounds.

16x7 Fuchs with centercap (no wheel weights) : 14.5 pounds.

Fuchs Felge claims 13.22 pounds on their site for their new 16x9s. https://www.fuchsfelgeusa.com/16-inch-silver/#16inchoptions
That seems too good to be true, but I have a set on order.

In a conversation with Brant at Fikse regarding 17x8.5 and 17x10.5 he told me "The weights of our Fuchs wheel is between 18lbs to 18.5lbs for the front and 19lbs to 19.5lbs for the rears."

I currently run 225/50-16 Trofeo R on 951 16x8s and 245/45-16 Trofeo R on 16x9s on my 1987 3.4. This seems like the lightest / grippiest setup available. Although, I'm considering Advan A052s in those same sizes the next time around. Somewhat less grip, but Tirerack shows 1 pound lighter for each A052 vs Trofeo R.

I was considering 17x8.5 and 17x10.5 Fikse Fuchs (with the rears specified to be run w/o the 930 / 491 rear spacers for a deeper dish), with 225/45 x 17 and 265/40 x 17 Michelin PS4S (slated to be released later this year), but I decided against it based on what appeared to be a pretty huge penalty in unsprung / rotational weight between the wheels and the tires versus my current 16" setup.

I'm going to bring my 16x7s, 8s & 9s by the post office and try to get more official weights on one of their lobby scales.

[Bill Verburg]

Originally Posted by famoroso

What's the source for those figures?

I just weighed a 16x9 Fuchs, with centercap (no wheel weights) on a bathroom scale and got 16.4 pounds.

For grins, 951 16x8 Fuchs (no centercap, no wheel weights): 15.6 pounds.

16x7 Fuchs with centercap (no wheel weights) : 14.5 pounds.

Fuchs Felge claims 13.22 pounds on their site for their new 16x9s. https://www.fuchsfelgeusa.com/16-inch-silver/#16inchoptions
That seems too good to be true, but I have a set on order.

In a conversation with Brant at Fikse regarding 17x8.5 and 17x10.5 he told me "The weights of our Fuchs wheel is between 18lbs to 18.5lbs for the front and 19lbs to 19.5lbs for the rears."

I currently run 225/50-16 Trofeo R on 951 16x8s and 245/45-16 Trofeo R on 16x9s on my 1987 3.4. This seems like the lightest / grippiest setup available. Although, I'm considering Advan A052s in those same sizes the next time around. Somewhat less grip, but Tirerack shows 1 pound lighter for each A052 vs Trofeo R.

I was considering 17x8.5 and 17x10.5 Fikse Fuchs (with the rears specified to be run w/o the 930 / 491 rear spacers for a deeper dish), with 225/45 x 17 and 265/40 x 17 Michelin PS4S (slated to be released later this year), but I decided against it based on what appeared to be a pretty huge penalty in unsprung / rotational weight between the wheels and the tires versus my current 16" setup.

I'm going to bring my 16x7s, 8s & 9s by the post office and try to get more official weights on one of their lobby scales.

bathroom scales are notoriously inaccurate

years ago I used 9x16 Fuch and got just under 20 on my bathroom scale, I have seen figures from ~14 to ~20#s in various places, pick a weight it doesn't make much difference either way

the Fikse weights are per Fikse

the unsprung weight is pretty irrelevant

The 2 important #s are the inertial cost which is mostly the tire due to weight and where the weight is situated and even more so the gearing cost from differing loaded rolling radii.

265/40 x17 is fine w/ a stout engine like a 3.6 but as the torque #s decrease that tire is less and less desirable

[famoroso]

FWIW...

[KNS]

Jeez the Fuchs are nice and light.

I recall weighing a BMW 17x8 cast aluminum wheel - I think it was 20 or 22 lbs.

[famoroso]

Adding this impressive datapoint, from this thread: 9 x 16 Fuchs Evolution wheel... 13.15 lbs!

[Bill Verburg]

Remember that wheels are often weighed w/ weights, valves, stem supports and sometimes ctr caps

the scale calibration and +/- error also comes into the picture

It look like you used a good scale so that's not an issue

[JonT]

Originally Posted by famoroso

What's the source for those figures?

I just weighed a 16x9 Fuchs, with centercap (no wheel weights) on a bathroom scale and got 16.4 pounds.

For grins, 951 16x8 Fuchs (no centercap, no wheel weights): 15.6 pounds.

16x7 Fuchs with centercap (no wheel weights) : 14.5 pounds.

Fuchs Felge claims 13.22 pounds on their site for their new 16x9s. https://www.fuchsfelgeusa.com/16-inch-silver/#16inchoptions
That seems too good to be true, but I have a set on order.

In a conversation with Brant at Fikse regarding 17x8.5 and 17x10.5 he told me "The weights of our Fuchs wheel is between 18lbs to 18.5lbs for the front and 19lbs to 19.5lbs for the rears."

I currently run 225/50-16 Trofeo R on 951 16x8s and 245/45-16 Trofeo R on 16x9s on my 1987 3.4. This seems like the lightest / grippiest setup available. Although, I'm considering Advan A052s in those same sizes the next time around. Somewhat less grip, but Tirerack shows 1 pound lighter for each A052 vs Trofeo R.

I was considering 17x8.5 and 17x10.5 Fikse Fuchs (with the rears specified to be run w/o the 930 / 491 rear spacers for a deeper dish), with 225/45 x 17 and 265/40 x 17 Michelin PS4S (slated to be released later this year), but I decided against it based on what appeared to be a pretty huge penalty in unsprung / rotational weight between the wheels and the tires versus my current 16" setup.

I'm going to bring my 16x7s, 8s & 9s by the post office and try to get more official weights on one of their lobby scales.

Did they give a time estimate on the delivery of your wheel order?

[famoroso]

Originally Posted by JonT

Did they give a time estimate on the delivery of your wheel order?

They being Fikse for the 17s? If so, I don't recall at this point, but it was something along the lines of 12 weeks. Which seemed optimistic. They offer a painted version of the RSR frosted finish now that they swear is a dead ringer for actual frosted anodized finish. The turnaround on the painted finish is much shorter.

If, OTOH, you were referring to the Fuchs Evolutions, I put a deposit down on the 9x16s during the summer and just got them a few weeks ago.

[JonT]

thanks Frank sorry for confusion I was referring to the Evolutions so appreciate the clarification. Jon