Unsprung Weight / Rotational Mass / Wheel + Tyre Weight

[ATM]

Is this the correct place to ask about Unsprung Weight / Rotational Mass / Wheel + Tyre Weight.

Would a change of wheels to reduce weight by 1kg be noticeable?

[ATM]

Standard Road car weighing 1,730kg.

Currently wearing 19 inch Run Flat tyres.

Cant decide if 19 inch Go Flat tyres will make much difference or if I should go all out and switch to 18 inch wheels and Go Flat tyres.

I know Run Flat tyres are heavier than Go Flat.

When comparing the standard 19 inch and 18 inch wheels for my car there is a 1.5kg weight difference per wheel.

[ATM]

19 inch wheel weight 13kg.
18 inch wheel weight 11.5kg.

BMW also sell some forged 20 inch wheels which only weigh 10kg - tempting right.

The car wears exactly same size tyres as the e46 m3. So I popped along to the m power section and did some digging. Seems the Goodyear asymmetric 2 is recommended and available for 660 for a set of 4 in 19 inch. 18 inch is pretty much the same price for tyres only. So in terms of price 19 inch or 18 inch are pretty cheap I'd say. 150ish per corner isn't awful. 20 inch are more like 250 - ouch.

I will try to find some info on tyre weights. Then I can compare the overall weight of wheel and tyre.

[ATM]

Camskill quote weights for some tyres and are better than tyrerack as they include decimal places. I've found looking at different tyres and their weights that they get heavier as the load rating increases. Interestingly the load on the Run Flats supplied by BMW are quite low and therefore not too heavy.

Current Bridgestone Run Flats supplied by BMW

Front
225/40RF19 89Y

Tyre Weight (kg) 11.5
Tyre Weight (lbs) 25.31

http://www.camskill.co.uk/m55b0s5062p110650


Rear
255/35RF19 92Y

Tyre Weight (kg) 13.1
Tyre Weight (lbs) 28.86

http://www.camskill.co.uk/m55b0s5068p110648


Goodyear Eagle F1 Asymmetric 2 Go Flats

225/40 R19 89Y

No weight on Camskill

http://www.camskill.co.uk/m55b0s467p105524


255/35 R19 96Y XL

Tyre Weight (kg) 11.6
Tyre Weight (lbs) 25.52

http://www.camskill.co.uk/m55b0s337p109698

[ATM]

I've been toying with the idea of getting some light weight forged wheels. 9kg compared to 13kg for my OE fitment wheels. Will I notice a difference?

[ATM]

one eyed mick said:

ATM said:

I've been toying with the idea of getting some light weight forged wheels. 9kg compared to 13kg for my OE fitment wheels. Will I notice a difference?

If you curb them they will bend easier !!!!!

I thought forged meant strong. Do they bend?

[ATM]

dblack1 said:

Forged can bend, but they are more likely to crack (than cast). Usually lightweight forged wheels are fragile.

So where does one go for lighter wheels. I see a lot of people using Racing Dynamics. Some of the OZ wheels specs sound light too.