Just wanted to know if anyone had an idea how much difference (seat of the pants or RR) the weight of wheels and hence rotating mass makes

My current wheels and the standard 16VT wheels weigh about 20kgs including a tyre

I see light weight racing wheels for sale (still alloy not magnesium) and they say they weight about 7kg-8kg for the rim or 12kg approx with tyre

So that is a saving of say 8-10kg by 4 is 30-40kg of weight but more than that it rotating weight.

Any idea if removing that weight will make any noticeable difference??

Reducing the unsprung mass of the wheel assembly (rim, tyre, brake disc, caliper etc) will improve ride and handling.

Hamster

TBH i cant say i have noticed any difference when i was running OZ alloy's on the tipo. I was running some 16's which were black and sort of multi-spoke and weigh a lot, i then got the OZ superleggera's and they were much lighter, but didn't notice any difference in performance. But the OZ wheels were 7kg without tyres and my current compomotive alloys weigh about 9kg each without tyres

I'll agree they should improve handling, but not always the ride...

If it was like this you should get lighter disks also...........
The only think you can expect from lighter wheels is good handling and ride
And the only thing you can get from a lighter shaft is that the engine will spool up easier.....(and higher....)

I think 4-5kgs is a bit optimistic for tyre weight unless you've got a Fiat 500 (60s version)

I'm running 9x17 Team Dynamics BTCC Production spec wheels on my race car, with tyre they weigh 20kgs, think they are about 11 without

Even allowing for your tyres being a bit smaller, still expect them to weight 7-8kgs

Regardless, reducing unsprung weight is a good thing. As Begbie says, don't stop there, get lighter discs/calipers as well as they ain't light

I just weighed my 18" Urban Racers (without tyres) for Barbz last night,they came out at about 10.5 -11 kg not too bad then.
What is the weight of a standard 16" 20V turbo wheel then ?

Around 9-9,5kg I belive, not 100% sure though.

I have bought Team Dynamics Pro Race 1.2 in 7x17", the weight for the wheel is 7.8 kg

I wouldn't have thought the weight of the wheels will affect the power of the car produced on a RR. Accelleration may be slower though as it's more weight to get spinning in the same sense that a lighter flywheel enables the engine to rev easier.

John

Extract from Pumaracing.co.uk in an article about lightening the flywheel:

Quote:

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Other Rotating Components

All other components which rotate absorb energy in addition to them having to be accelerated linearly along with the chassis. Components which rotate at engine speed like flywheels are the most cost effective ones to lighten in terms of their equivalent chassis mass but it pays not to overlook the mass of any rotating component. 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

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Thanks for the answers all

Whittler that puma racing article was very interesting - well looks like I am after some light wheels then for track days.

Cheers

thanks for the article too.

cheers.