Do heavier wheels overly affect performance
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From: On a street corner
I can't make the calculations for you so I won't try however I remember a lecture from the guy who designed the suspension set-up on the McLaren F1 whilst I was at Uni.
Someone asked him what was the weakest design point of the F1. He answered the brake disks. He went on to say that you cannot have the best performance of any vehicle with large rotating masses unsprung. The weight of the disks was said to be 6kg each and he thought this was far to hi and work would need to be done in materials research to reduce this.
So I guess the same logic applies to the wheels. The lighter the better generally.
Someone asked him what was the weakest design point of the F1. He answered the brake disks. He went on to say that you cannot have the best performance of any vehicle with large rotating masses unsprung. The weight of the disks was said to be 6kg each and he thought this was far to hi and work would need to be done in materials research to reduce this.
So I guess the same logic applies to the wheels. The lighter the better generally.
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From: Northampton
What I don't understand is that people worry about the increased weight of bigger alloys, but don't seem to factor in the probably lower weight of the lower profile tyres. Or is tyre weight not changed much by the lower profile? 
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From: Hertford
Originally Posted by Richieh,Aug 5 2005, 02:48 PM
What I don't understand is that people worry about the increased weight of bigger alloys, but don't seem to factor in the probably lower weight of the lower profile tyres. Or is tyre weight not changed much by the lower profile?
Also, a larger diameter alloy rim requires more metal, for the same reasons. (Which is why the mass increases with each increment in diameter.)
It also increases gyroscopic and unsprung masses.
Interestingly, even the rice brigade has noticed that JDM racers tend to stick nearer to the original diameter, increasing the width instead. A recent trend amongst custom cars is to do so too.
Unless you are a rap artist with a Hummer on dubs, big wheels are so passe!
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From: Heart of England
Originally Posted by phase_k,Aug 4 2005, 02:51 PM
Have you taken into consideration whether or not your wheels have a overall bigger radius? If they do that will increase top speed but reduce acceleration. Again I'm not sure if it would be to a level that you would notice it but hey ho!
My last S had the 18" EVO's on as well.
My current S has very light 18" Volks.
Both used the same size and make of tyre.
Massive difference
Current car is great apart from one problem on the rear
(no comments Craig or StevenM
)The unsprung weight thing is sooo true, I have noticed on my current car.
Much more complaint to hard corners and changes in road surface.
More feel on braking as the wheel is not got so much inertia.
The quote above on the rolling radius is also spot on.
On a 1st Lotus day my car with the EVO's on could reach the end of the straight in second everyone else was having to change to third. Increase in diameter increase gearing, making it slightly slower with a higher top end.
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From: Southampton
here's a post I made on another forum when I got my new TE37s last year
hope that helps!
Originally Posted by ctrlaltdelboy
Hi all
my new 'Volk Racing' wheels arrived and I have just ordered the tyres to go on them, just thought I'd share the technical elements of the wheel tyre change for those who are interested.
wheels
as you can see the oem wheels grew by 1" diameter and 0.5" width both front & rear between the orig spec in 1991 and the revised spec in 1994, and my new wheels have retained the larger 16"/17" diameters of the revised sizes, but added an extra inch width at the same time. Crucially this extra width in the larger size has come not only with zero weight overhead but has reduced the wheel weight below both the revised AND original weights.
Tyres
I have gone for Kumho V70A tyres front & rear for 3 reasons:
1. excellent trackday grip
2. lowest weight I could find
3. comparatively inexpensive
see in the chart above how 3 different sets of tyres compare - there's not quite so much of a weight saving for me on the tyres, but not bad considering the extra tyre width though - up from the current 225 front to 245 with a minor saving of 0.4kg per tyre, and up from the current 255 rear to 275 for the same weight.
so I have gained 20mm per corner over my current setup at the same time as trimming 8.7kg of rotational unsprung weight from the car (that's 30mm per corner over standard oem 94-01 sizes with similar weight savings), and a whopping 40mm per corner front and 50mm per corner rear over the oem 91-93 sizes at a weight penalty of just 3.2kg - although this last comparison is largely academic for me and most NSX'ers since most are on the oem 94-01 wheels anyway, but useful for anyone who is still on the smaller oems.
here is how the dimensions vary between the different setups
the Volk TE37s look like this
the website is here http://www.rayswheels.co.jp/emenu/wheel.html
my source for the wheels was Dali Racing - details here
useful tool here for calculating tyre sizes etc
UK & Europe info on the Kumho ECSTA V70As is here
my source for the tyres was South Shore on 01253 761362
my new 'Volk Racing' wheels arrived and I have just ordered the tyres to go on them, just thought I'd share the technical elements of the wheel tyre change for those who are interested.
wheels
as you can see the oem wheels grew by 1" diameter and 0.5" width both front & rear between the orig spec in 1991 and the revised spec in 1994, and my new wheels have retained the larger 16"/17" diameters of the revised sizes, but added an extra inch width at the same time. Crucially this extra width in the larger size has come not only with zero weight overhead but has reduced the wheel weight below both the revised AND original weights.
Tyres
I have gone for Kumho V70A tyres front & rear for 3 reasons:
1. excellent trackday grip
2. lowest weight I could find
3. comparatively inexpensive
see in the chart above how 3 different sets of tyres compare - there's not quite so much of a weight saving for me on the tyres, but not bad considering the extra tyre width though - up from the current 225 front to 245 with a minor saving of 0.4kg per tyre, and up from the current 255 rear to 275 for the same weight.
so I have gained 20mm per corner over my current setup at the same time as trimming 8.7kg of rotational unsprung weight from the car (that's 30mm per corner over standard oem 94-01 sizes with similar weight savings), and a whopping 40mm per corner front and 50mm per corner rear over the oem 91-93 sizes at a weight penalty of just 3.2kg - although this last comparison is largely academic for me and most NSX'ers since most are on the oem 94-01 wheels anyway, but useful for anyone who is still on the smaller oems.
here is how the dimensions vary between the different setups
the Volk TE37s look like this
the website is here http://www.rayswheels.co.jp/emenu/wheel.html
my source for the wheels was Dali Racing - details here
useful tool here for calculating tyre sizes etc
UK & Europe info on the Kumho ECSTA V70As is here
my source for the tyres was South Shore on 01253 761362
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From: Isle of Man
Originally Posted by mikey k,Aug 5 2005, 07:32 PM
My last S had the 18" EVO's on as well.
My current S has very light 18" Volks.
Both used the same size and make of tyre.
Massive difference
Current car is great apart from one problem on the rear
(no comments Craig or StevenM )
My current S has very light 18" Volks.
Both used the same size and make of tyre.
Massive difference
Current car is great apart from one problem on the rear
(no comments Craig or StevenM
)All I've ever read on this indicates designing the unsprung weight to be as low as possible is an important performance parameter. However, the chances of us ever being able to notice differences on the road are pretty remote.
By its nature, a valid comparison is almost impossible to make even on the same car, simply because different tyres also have to be used and you would be evaluating the tyre/wheel combination as well as any differences made in unsprung weight. Even on the track where you can eliminate other variables, the same is true and all you can compare are the combinations of factors. That isn't to say in controlled conditions you won't find one 'combination' quicker/more responsive than another, but it's not necessarily possible to isolate the cause.
If you were obsessive enough, the only way this seems do-able to me is to add weights to a wheel to simulate the bigger wheel while using the same tyre and, back to back, see what difference it makes. In theory it could be detected, simply because the rotational mass is a power equation, the effective weight increasing exponentially as it gets further from the axis, but what do I know - I push a pen for a living!
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From: Heart of England
I understand what you're saying. But with out going the obsessive route IMHO my two cars are as close as anyone will get to being able to see a difference on the road.
Same driver
Same tyres
Same roads
Same diameter
Only differences are
04 vs 00
0.5 inch on the width of each wheel
Volks vs EVO
Ian is asking about unsprung weight in relation to EVO's so I've added my 2p as I've been there and changed for the reasons he identifies.