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LIGHTWEIGHT Wheels
- Thread starter MidKnight7
- Start date
Hi, I finally changed wheels from VW Dover 16 inch to OZ Ultraleggera, 7.5Jx17, ET50.
Now I also have Continental PremiumContact 7 225/45R17 91V tyres.
The wheels weigh 7.8 kg, or 17.2 lbs for US citizens.
My totally scientific instrument (AKA my butt) tells me that the car has improved also in comfort.
Placebo effect? Who knows... but Dovers weigh around 10.8 kgs, so that was a massive unsprung and rotational inertia reduction.
Now I also have Continental PremiumContact 7 225/45R17 91V tyres.
The wheels weigh 7.8 kg, or 17.2 lbs for US citizens.
My totally scientific instrument (AKA my butt) tells me that the car has improved also in comfort.
Placebo effect? Who knows... but Dovers weigh around 10.8 kgs, so that was a massive unsprung and rotational inertia reduction.
urtoinpo
New member
- Location
- South Coast
- Car(s)
- 2019 Variant 150 TSI
Welcome to a livelier - and maybe also more economical, (depending on tyre rolling resistance) Golf.
Your tire and wheel combo probably weighs almost exactly the same as before. What you've lost in wheel weight, you've made up for in tire weight, still all unsprung. Inertia may actually be higher since the weight is now closer to the perimeter. That, however, is good for ride. Lighter is actually worse for ride as it has less inertia, will react more easily to road imperfections and send more energy to the suspension. Better for handling which is why it's done but not a solution to improve comfort. Heavier will not react as easily and have the tire deform more to imperfections. Wider tires can also to ride a hair better, simply by more averaging of road irregularities. Other factors like sidewall stiffness also have a large effect. I also doubt you've gained any efficiency via less rolling resistance unless they're deforming less while rolling.
I know people will argue these points but please search 1st. Simple 'unsprung mass' search on wiki will do.
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urtoinpo
New member
- Location
- South Coast
- Car(s)
- 2019 Variant 150 TSI
Highly unlikely that the new 225/45x17 tyres will weigh an extra 3Kg each over the old 16" ones, so an overall unsprung saving
seems certain in this case, even if it amounts to only around 6Kg across all 4 wheels. The wider tyres are likely to have increased
rolling resistance, but then the expected extra grip/traction from takeoff in most conditions should be welcome compensation.
One point regarding ride quality that often gets overlooked is that a lighter unsprung mass gives the suspension and in particular
the dampers/shox an easier time of things, allowing them to react more effectively. On some cars when fitted with a lighter
wheel/tyre combo I've noted that the damper's rebound response was improved, albeit only slightly. In any case the car will 'feel'
a faction livelier/nicer in it's handling, even though you could argue that small differences are a bit pointless on a road car.
3 kgs on a tire that has less sidewall and 20mm more width? That would mean that the cylindrical thread part of the tyre would weigh 225*3/20=33.75 kg. It doesn't.
Conti PC7 at 205/55R16 91V weigh 8.6 kg and at 225/40 R18 92Y weigh 8.9 kg according to tyrereviews.com.
It is safe to assume that the inertia tensor is reduced throughout all its numbers because the wheel is 2.5 kg lighter while the weigh distribution is not that different. I would be very willing to calculate the exact numbers but I do not have exact wheel measurements from a 3D scanner. If I ever get one, I will report the calculations here.
Lighter is not worse for the ride. Road imperfections are forced excitations and more or less they have the same effect on the tyre contact "point", but not on the wheel. Because it is a forced excitation, the amount of energy that will be eventually dissipated by the suspension depends largely on the mass and is more or less proportional to it, so lighter means less energy. More unsprung weight directly means more mass to be damped, hence you increase the time where the tyre has less vertical contact force, if any at all .
Wider tyres might average road irregularities or not. This is a very fuzzy topic and I am not willing to discuss on it.
Fuel consumption will mostly be negatively affected by aerodynamics, not rolling resistance. I have a less aerodynamic wheel and a wider tyre that has increased the cross-sectional area. I am simply expecting less than 0.2lt/100km as an impact. If I get that, I will be happy. I also lost some top speed, but, in all honesty, this is a family car. Braking under risk was my main concern.
I overstated but those aren't the sizes in question.
I checked a Conti that's popular in the states, ExtremeContact DWS 06 Plus, just now and the difference in weight of those sizes is exactly 2 kg so you're likely correct that he's lost a kg or so. Maybe not depending on how worn his old tries were since they lose over a kg before they're done. I don't recall what tire I used to compare before that previous post but the difference happened to be greater. This will obviously vary somewhat by tire chosen. Whether he lost or gained overall weight will be dependent on the previous tire used etc. but as you stated, he's likely lost a bit or even.
Lighter is used for handling as it has less inertia to overcome and will respond to irregularity more easily. Tracks better but sends that extra deflection energy to the suspension as opposed to more tire deformation (better ride). Same weight and more width may actually help as he perceived but lots of variables like sidewall structure etc to argue the point either way. My post was purely theoretical.
I wasn't trying to do anything but supply some good info to an often misstated comment here. Lighter weight on it's own does not improve ride but should help handling/tracking.
Apologies if it came off as more than that. His new tires and wheels look great.
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MonkeyMD
Autocross Champion
Great looking wheel.It’s been a little while since I got my Konig F1M wheels installed. I’ve been happy with them thus far, especially since I didn’t pay full price!
View attachment 310400
View attachment 310401
What's the weight on those?
What tire size? Looks like there's a big gap in the rear
Thanks man!
The weight is listed at 17.4 lbs. Tires are Falken Azenis summer tires (I really like these tires a lot), 235/40/18.
I guess the picture seems to show some gap, but I don’t really mind it, or think it’s too big in person.
I’ve gone back and forth with lowering vs not lowering and I just keep finding that I’m fine with my car the way it is (looks and drive-ability), so I still haven’t messed with it yet. Ha!
