Useful wheel weights page

[S2central.net]

http://www.pumaracing.co.uk/FLYWHEEL.htm has useful calcs for comparison of this rotating mass stuff and explains the gearing effect I mentioned.

Paul

[Rusty]

Without tyres. Use 10Kg as a rough guide for 17s.

Good 'ol Puma Racing, so many useful articles in there

[Rusty]

The next major category is items which rotate at wheel speed - wheels, tyres, discs etc. These don't rotate as fast as engine components but they can be very heavy. The average car wheel and tyre weigh about 45 lbs together. A good rule of thumb is that in addition to its own normal weight a wheel speed item adds the equivalent of an extra 3/4 of its mass to the effective chassis mass and this figure is not dependent on gearing so it stays a constant at all times. It's a smaller effect than the flywheel effect which can be many times its own mass in first gear but still important. Let's say you fit wide wheels and tyres to your car. If each corner weighs an extra 10 lbs more than the standard items then the effective increase in chassis mass is 40 lbs for the direct weight plus another 30 lbs being 3/4 of the direct mass - a total of 70 lbs. On a light car like a Westfield or hillclimb single seater this could be between 5% and 7% of the effective total car weight. Equivalent to knocking the same percentage off the engine's power in acceleration terms. That's why F1 and other high tech series designers strive so hard to reduce weight in this area and use magnesium instead of aluminium for wheels and the thinnest possible carcasses for tyres. It also reduces unsprung weight of course which helps the suspension and handling. Even on a 1 ton road car the effect of heavy wheels and tyres can be noticeable in terms of reduced acceleration. Wider tyres also absorb a bit more power in friction which doesn't help either if the engine is on the small side. Copyright David Baker and Puma Race Engines

HTH

[EspenW]

This is why I put the 24kg 18" Turbo Cups up for sale and replaced them with 19.9kg original Cups in 17".
16kg saving that equals 25kg off the car due to rotational inertia
(heavy) 18's are for posers

[robo]

These are nice and light but may just be bit to expensive.












http://www.boostcruising.com/forums/...owtopic=272203

[Rusty]

Or you could put you $29k (£15k) into a Caterham R300...

[robo]

Done some weights on good old bathroom scale and

Compomotive 17'' MO with Toyo r888 255/40/17-------> 24kg
Standard 16'' Avus with Michelin Pilot 205/55/16-------> 19kg

[Albert]

http://www.wheelweights.net/

[Rusty]

[S2central.net]

Finally got some wheels and tyres weighed here...

Original 16" Avus on original Kleber 205/55 weigh in at 18.3kg
same rim with Pirelli Winterspors (same size) is 18.4kg

NOW........

The RS6 rep (18x8) with Avon 225/45 rubber is a whopping 23.2kg - ridiculous

So thats an extra 20kg of rotating mass being carried round - no wonder the comfort factor is reduced. Guess the old tired shocks (which work fine on the 16s) just cant cope with the extra weight.

[4WheelDrifter]

My 18" RS4 reps weigh ~15kg IIRC, compared to the 17" Cup reps at 11.5kg. Lucky I have a set of 18s that only weigh ~10kg too.
In a way it's a shame I gave the lighter set of RS4 reps to a new home, but the double drilled set is more useful as a back-up.

[Rusty]

Supposedly 7.3Kg for my OZs

[hiltoa]

http://www.wheelweights.net/

Still no cocking BBS RYs!

[EspenW]

Finally got some wheels and tyres weighed here...

Original 16" Avus on original Kleber 205/55 weigh in at 18.3kg
same rim with Pirelli Winterspors (same size) is 18.4kg

NOW........

The RS6 rep (18x8) with Avon 225/45 rubber is a whopping 23.2kg - ridiculous

So thats an extra 20kg of rotating mass being carried round - no wonder the comfort factor is reduced. Guess the old tired shocks (which work fine on the 16s) just cant cope with the extra weight.

Less comfort due to 20kg extra unsprung weight and a decrease in acceleration/longer braking distances to the tune of the equivalent of an excess 35 kg of static weight being carried around. Not good.

[S2central.net]

All agreed - but they still look nice

Dunno what to do really - maybe I should try wider tyres on lower profile with the 16" Avus - they are the right wheel after all...

There's not many wheel designs I like on the S2 - and my favourites are just too expensive... Perhaps a 2nd set of Avus is what I should be doing. I don't need monster monster brakes - the 996s on A8 discs spund down to approx 308mm will be more than enough for me... I can't be assed with wheel spacers myself... Already fitted standard size wheel studs anyway so that makes spacers an even bigger pain.