What did you do to your mk7 today?

[INSMk7GTI]

Austins are 25 lbs so not terribly heavy.

My wheels are 10 lb lighter per corner and there is a huge difference compared to stock. The car is flying now.

 

[asecondfaster]

Got tint done.

Before

After

I thought CA Law are not allowed tint on driver/front passenger seat?

I own exact car as yours, was it SEL? How much are you paying it for? If you don't mind me asking. Finally to see another twin car within 100 miles, ha!

 

[Johnny Blaze]

In CA there is NO tint allowed on the front windows, however cops usually bust you when they can't see inside...

 

[SixSpeeder]

Got tint done.

Before

After

Nice, looks great with white.

I thought CA Law are not allowed tint on driver/front passenger seat?

I own exact car as yours, was it SEL? How much are you paying it for? If you don't mind me asking. Finally to see another twin car within 100 miles, ha!

It's not really enforced regularly out there. I had a sedan with one notch below limo tint all around for years in southern CA, and I never got written up for it. I even got a few speeding tickets during that time, but the cops never mentioned it. I guess it depends where exactly you live also.

 

[Nevo]

My wheels are 10 lb lighter per corner and there is a huge difference compared to stock. The car is flying now.

That's why you need the GTD in the states!

 

[Shini]

My wheels are 10 lb lighter per corner and there is a huge difference compared to stock. The car is flying now.

Holy moly. That's huge. Something like 400lbs of rotating mass difference.

Man, sort of want some of those wheels now! What do you have? TSW Nurburgrings?

 

[benowid]

That's 10lbs of rotating mass less per wheel as he stated. If you have stock wheels I could figure out an equivalent static mass with respect to acceleration. The geometry of the rotating member dictates the effect on lateral acceleration. You can be sure this -40lbs if total rotating mass will make a noticeable difference in lateral acceleration.


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[Shini]

That's 10lbs of rotating mass less per wheel as he stated. If you have stock wheels I could figure out an equivalent static mass with respect to acceleration. The geometry of the rotating member dictates the effect on lateral acceleration. You can be sure this -40lbs if total rotating mass will make a noticeable difference in lateral acceleration.


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Yeah, if I'm not mistaken it's 10:1 so every 1lb off weight = about 10lbs of rotating mass being shaved.

Huge diff for sure.

 

[benowid]

That is incorrect. The wheels ARE rotating mass. If you remove 10 lbs of rotating mass then that is how much rotating mass you have removed. It is also not true that 10:1 static mass to rotating mass. The effect of rotating mass in lateral acceleration is quite complex. The angular acceleration of a rotating member is a function of the location of the mass about an axis. The angular acceleration is s function of what is called moment of inertia. Moment of inertia is as stated above dictated by the geometry of the object rotating about an axis. Once you know the change in angular acceleration you can then begin to calculate the effect on lateral acceleration which is s multi variable equation.
This is a simplistic explanation but should clear s few things up.
I am a vehicle design engineer and this is what I do day to day. Feel free to ask any question.
Cheers


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[Shini]

That is incorrect. The wheels ARE rotating mass. If you remove 10 lbs of rotating mass then that is how much rotating mass you have removed. It is also not true that 10:1 static mass to rotating mass. The effect of rotating mass in lateral acceleration is quite complex. The angular acceleration of a rotating member is a function of the location of the mass about an axis. The angular acceleration is s function of what is called moment of inertia. Moment of inertia is as stated above dictated by the geometry of the object rotating about an axis. Once you know the change in angular acceleration you can then begin to calculate the effect on lateral acceleration which is s multi variable equation.
This is a simplistic explanation but should clear s few things up.
I am a vehicle design engineer and this is what I do day to day. Feel free to ask any question.
Cheers


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Damn those internet rumors! I was always under the assumptiong 1lb shaved off "unsprung" translated into 10lbs off "sprung" weight.

Thanks for the info

 

[benowid]

Any time. Sprung vs un-sprung. And rotating vs static are two very different things as well. Just to make it even more complicated. I am happy to clear anything up. I hope no offense is taken. I am only trying to provide true solutions to ambiguous Internet gossip. If there is enough interest I can write about either or both of these subjects.
Cheers


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[Shini]

Any time. Sprung vs un-sprung. And rotating vs static are two very different things as well. Just to make it even more complicated. I am happy to clear anything up. I hope no offense is taken. I am only trying to provide true solutions to ambiguous Internet gossip. If there is enough interest I can write about either or both of these subjects.
Cheers


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No offense taken

Would you be able to do the math to figure out the ratio between the two?

Well, okay, so if sprung and unsprung are different, would the 10:1 ratio be more of less correct then?

I know that you get more gain from shaving weight off wheels than just the unsprung/static weight, and I know 10lbs off is a big difference too, just trying to figure how big it is

 

[benowid]

So there are two different things we are discussing here.
1. The effect of spring vs un-sprung mass in lateral cornering acceleration.
2. The effect of rotational vs static mass on lateral forward (straight line) acceleration.

I can do the math and have some spreadsheets I have made in excel to deal with all the mathematics involved. In order to bring you up to speed on ur mechanics and implications of these things would take many hours and a large background in physics and mathematics to truly quantify the methods involved in figuring out these two subjects. In short there is no simple formula to say 1:10 lbs of sprung to un-sprung. I could give you exact solutions to the questions but to make it easy on both of us. I will say this.

1. It is safe to assume any decrease in u sprung mass will aid in bump sensitivity and overall grip.
2. Decrease in rotating mass will increase all lateral acceleration (both radial and tangential)
3 decrease in any mass wether it be rotating, static, sprung or un-sprung will increase acceleration and grip.

Cheers
Your resident vehicle engineer


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[Shini]

So there are two different things we are discussing here.
1. The effect of spring vs un-sprung mass in lateral cornering acceleration.
2. The effect of rotational vs static mass on lateral forward (straight line) acceleration.

I can do the math and have some spreadsheets I have made in excel to deal with all the mathematics involved. In order to bring you up to speed on ur mechanics and implications of these things would take many hours and a large background in physics and mathematics to truly quantify the methods involved in figuring out these two subjects. In short there is no simple formula to say 1:10 lbs of sprung to un-sprung. I could give you exact solutions to the questions but to make it easy on both of us. I will say this.

1. It is safe to assume any decrease in u sprung mass will aid in bump sensitivity and overall grip.
2. Decrease in rotating mass will increase all lateral acceleration (both radial and tangential)
3 decrease in any mass wether it be rotating, static, sprung or un-sprung will increase acceleration and grip.

Cheers
Your resident vehicle engineer


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Very good! Thank you sir

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[corfyboy]

The amount of movement, for short bumps, is inversely proportional to the weight - a lighter wheel which readily moves in response to road bumps will have more grip and more constant grip when tracking over an imperfect road. For this reason, lighter wheels are sought especially for high-performance vehicle's and would improve over all ride quality.. Filling the tyres with nitrogen again can have benefits [emoji2]