Well Would You Believe It...

[alfiejts]

I remember an old thread discussing the virtue of alloy wheels over steel wheels and the fact that reducing unsprung weight by a pound or two would make a massive difference to a car's handling.

And I thought to myself at the time - Well that might make a slight difference in motorsport using a proper magnesium alloy racing wheel, but I'll bet there's not much in it between a standard steel wheel and an aluminium alloy road wheel - and even if there were a couple of pounds difference - you're really not going to notice it on a road car.

Well the basic question stayed with me and I now just happen to have a bare set of 15" Yaris steel wheels and a bare set of 15" alloys awaiting winter tyres.

So basically, the wheels are a direct comparison between the standard fit steel wheel and a manufacturer supplied equivalent alloy.

So I've stuck them on the scales....

The steel wheel weighed in at 7.0kg and the alloy wheel weighed in at 8.5kg....

So there you have it.

Don't pretend any longer that specifying alloys on a road car is a performance upgrade because of the reduced unsprung weight - but treat it as a pure fashion accessory and you'll be fine.....

[minidoughty]

lol...sweeping generalisation if ever i've heard one...

That's just for those 2 specific sets of wheels you weighed, were both purposely built for that exact model of car?

A P1 Tsport alloy wheel weighs 6.6kg, and something like a rota make alloy can be around 5kg.

Surely they would make a difference, being a clear 1-2kgs lighter per wheel.

And then there's the factor of tyre type/size/tread FOR those wheels... which would all affect the "performance"...

[Sico2]

I am quite open to believe you, but can I just ask if there is no difference in tire weight? Or were there weighted tireless?

[Sagitar]

I am quite open to believe you, but can I just ask if there is no difference in tire weight? Or were there weighted tireless?

It wouldn't surprise me if the lightest wheels, size for size, are still going to be an old fashioned rim with high tensile steel wire spokes. Does ayone have any hard data?

[Bibbs]

Also depends on where the weight is in the wheel.

It's all about rotational mass.

5kg on the lip is harder to turn than 5kg on the hub.

[alfiejts]

These are the same size wheels for the same size tyres....

The same "standard" wheels for the same car, as supplied by Toyota.

They were weighted "bare" without any tyres or balance weights.

And yes - aftermarket wheels can all weigh differently, but my point was that for the same size wheel and tyre, as a manufacturer option on the same car, there's little difference.....

And I'll bet too that the "classic car" old fashioned spoked wheels are still the lightest - which is why they still use them on cycles....

But it always makes me smile how these posts bring out the extremes in all of us...

Are we saying that in a road car anyone is really going to notice the difference in handling in wheels that weigh a kilo or two differently?

I can't even tell the difference in performance between when I'm driving solo and when I'm driving with a passenger - and that's another 70kg of weight , stuck high above the centre of gravity....

Equally, a tank of fuel in my A3 weighs 40kg. Can I tell any difference in handling between the car with a full tank or an empty tank - with all that weight balance shift between the front and back? Can I heck....

Its great to have a theoretical debate, but I'd challenge anyone to say that it makes any real difference in an ordinary road car on the public road.....

[Sagitar]

These are the same size wheels for the same size tyres....

The same "standard" wheels for the same car, as supplied by Toyota.

They were weighted "bare" without any tyres or balance weights.

And yes - aftermarket wheels can all weigh differently, but my point was that for the same size wheel and tyre, as a manufacturer option on the same car, there's little difference.....

And I'll bet too that the "classic car" old fashioned spoked wheels are still the lightest - which is why they still use them on cycles....

But it always makes me smile how these posts bring out the extremes in all of us...

Are we saying that in a road car anyone is really going to notice the difference in handling in wheels that weigh a kilo or two differently?

I can't even tell the difference in performance between when I'm driving solo and when I'm driving with a passenger - and that's another 70kg of weight , stuck high above the centre of gravity....

Equally, a tank of fuel in my A3 weighs 40kg. Can I tell any difference in handling between the car with a full tank or an empty tank - with all that weight balance shift between the front and back? Can I heck....

Its great to have a theoretical debate, but I'd challenge anyone to say that it makes any real difference in an ordinary road car on the public road.....

Well, we are getting a lot of different issues confused. The thread started (I think) with comments about unsprung weight - that has nothing to do with rotational mass, but everything to do with the way that the suspension behaves. There are all kinds of trade-offs, but generally, the less the unsprung weight and the more readily the road wheels will follow (i.e. remain in contact with) the surface of the road and will not transfer the effect of road imperfections to the body of the vehicle. The unsprung mass is everything that is on the "outside" of the spring system that isolate the body of the vehicle from the road wheels, so it includes axles, brakes, transmission components etc. as well as wheels and tyres, but passengers, cargo and fuel are not part of the unsprung weight.

If the mass of the other unsprung components involved is large, then a small change in the mass of a wheel should make little difference, but in a vehicle where all the unsprung components have been configured and designed for minimum unsprung mass, a change of wheel mass may be significant.

Inevitably, these effects have more importance as we push vehicle performance. In a low-powered vehicle driven sedately they will be difficult to detect. But putting power down and maintaining grip when driving at the limit will depend crucially upon maximising the extent to which the wheels are kept in contact with the road.

Of course, many of the things done for effect in performance motoring are done for "appearance" in everyday motoring. Go-faster stripes will always be with us . . . . . :P

[reece]

For the normal family car hatch or saloon the only reasons for alloy wheels in my opinion are they look a lot better than steel wheels and plastic trims, and also by their design, the brakes will be cooled easier as more air reaches them (for the more spirited drivers). Its also easier to keep an eye on pad wear and disc condition. When my boot is full of shopping, a wheel that is 2kg heavier or lighter isn’t on my radar.

[gar]

These are the same size wheels for the same size tyres....

The same "standard" wheels for the same car, as supplied by Toyota.

They were weighted "bare" without any tyres or balance weights.

And yes - aftermarket wheels can all weigh differently, but my point was that for the same size wheel and tyre, as a manufacturer option on the same car, there's little difference.....

And I'll bet too that the "classic car" old fashioned spoked wheels are still the lightest - which is why they still use them on cycles....

But it always makes me smile how these posts bring out the extremes in all of us...

Are we saying that in a road car anyone is really going to notice the difference in handling in wheels that weigh a kilo or two differently?

I can't even tell the difference in performance between when I'm driving solo and when I'm driving with a passenger - and that's another 70kg of weight , stuck high above the centre of gravity....

Equally, a tank of fuel in my A3 weighs 40kg. Can I tell any difference in handling between the car with a full tank or an empty tank - with all that weight balance shift between the front and back? Can I heck....

Its great to have a theoretical debate, but I'd challenge anyone to say that it makes any real difference in an ordinary road car on the public road.....

So can you tell the difference between a full car, fully gassed and an empty one with an empty tank? My guess is you can and if you cant, you need a bit of driver training! LOL!

Oh, and also, you can get what is often called "Light alloy" wheels, even lighter than standard but don't forget, they will damage easier!

[alfiejts]

As a qualified "Advanced Motorist" taking in three months of driver training and passing the IAM advanced driving test (based on the Police method of advanced driving) I suspect I'm at the top end of the civilian "driver training" table...

Having driven Caterham Superlights, VX220 Turbos, Formula Audi single seaters, Renault Clip Cup touring cars, Mitsubishi Evos and many others on racing tracks, I can appreciate the balance of all these factors in a competition environment.

My point was that driving an ordinary family road car, within the limits that you should be driving it on a public road, you'd be hard pushed to pick up any of these "theoretical" factors we're discussing in this chain.

So I'm with Reece on this.

I've solved the previous query of just how much lighter and how much real performance difference to "same size" alloys make - the answer is none, they're just cosmetic...

All the rest is great banter, but irrelevant for the public road (or it should be.....) :-)

[alfiejts]

I've just spotted your comment "Full tank and a full car compared to an empty tank and empty car - you should be able to tell the difference" - I totally agree but that's not the point I was making.

Full tank and a full car - you're talking of 4 x 70kg people plug 40kg of fuel - at least 320kg - of course you'll notice that difference.

My comment was that in a car of the same state (be it full or empty) you'd struggle to notice any difference between a full and empty fual tank - which is 40kg more weight at the back - and we're debating whether you'd notice the difference a couple of pounds of unsprung weight would make.

So again - its a great theoretical debate but of no real meaning in a road car under normal use...

As a further question - do you allow your partner to raise the passenger seat or insist that its left on its lowest setting to keep the centre of gravity low? Again that will affect the handling but again, whilst I consider the matter each time I see my passenger seat set higher than my drivers seat I don't bother insisting that she lowers the seat because of the impact she's making to the car's handling....

[minidoughty]

bored now.....

[carlowlad]

As a further question - do you allow your partner to raise the passenger seat or insist that its left on its lowest setting to keep the centre of gravity low? Again that will affect the handling but again, whilst I consider the matter each time I see my passenger seat set higher than my drivers seat I don't bother insisting that she lowers the seat because of the impact she's making to the car's handling....

I've never bothered with such a trivial matter. Even if i was, i doubt it would make the blindest bit of difference to anything under normal circumstances. Rally drivers do it, yes, but they are at the edge and little things make big differences.

If you get the chance could you measure the weight of your new versus old tyres? There may be a difference there, even if they are the same size and allowing for tread wear......heh!

I'm a fuel economy nut and have seen discussions on wheel/tyre weight affecting fuel economy. The general outcome is that it makes a negligible difference. I can only assume that any differences in handling will only surface in a race application when the car is at the edge of traction a lot. Or if you drive very fast all the time.....

[reece]

It’s all academic really. My passenger sits in the lowest position, my alloys are a kilo each lighter, or I run on minimum fuel just so I can get to Sainsburys to 2 tenths of a second quicker

Of course all my weight saving techniques are in vain when I see the Christmas 2 for 1 special offers

[alfiejts]

bored now.....

I'm just getting into the swing.....

Has anyone worked out how much less helium weighs than air for the volume of air in a tyre?

That must take a pound or two off the unsprung weight too....

[hertsnminds]

Can't say I have ever had the chance to compare the difference in feel/drivability between alloys and steels. However things that I do notice make a difference are the tyre tread patterns, the amount of wear and the tyre pressures.

As for full and empty fuel tanks it depends on the car, I have owned some cars where you cannot tell the difference and others where you can. The only car I have owned where it seemed to behave the same no matter how many passengers, how much fuel or how much junk was in it was a Citroen BX GTi. The 2 litre engine had more than enough power and the pneumatic suspension meant the ride quality never changed.

[aygoal]

bored now.....

I'm just getting into the swing.....

Has anyone worked out how much less helium weighs than air for the volume of air in a tyre?

That must take a pound or two off the unsprung weight too....

Do the upgraded bulbs weigh more than the normal ones???

[reece]

Do the upgraded bulbs weigh more than the normal ones???

Not as much as the chrome valve dust caps...

[alfiejts]

bored now.....

I'm just getting into the swing.....

Has anyone worked out how much less helium weighs than air for the volume of air in a tyre?

That must take a pound or two off the unsprung weight too....

Do the upgraded bulbs weigh more than the normal ones???

Upgraded headlight bulbs will have thinner filaments (which is why they're brighter), so they will weigh less.

And on a front wheel drive car that will be really useful as it will help shift the weight distribution more to the rear

[aygoal]

bored now.....

I'm just getting into the swing.....

Has anyone worked out how much less helium weighs than air for the volume of air in a tyre?

That must take a pound or two off the unsprung weight too....

Do the upgraded bulbs weigh more than the normal ones???

Upgraded headlight bulbs will have thinner filaments (which is why they're brighter), so they will weigh less.

And on a front wheel drive car that will be really useful as it will help shift the weight distribution more to the rear

Granted the filament is thinner, but I thought they were also filled with a different gas so we need to check the relative atomic weights!!!

Also have you upgraded any rear bulbs???

[Cyker]

[Chris81]

No comments to make on the wheel debate - but on my t-sport I definitely notice the difference in weight when the petrol tank is full vs. when it's one quarter full, same goes for passengers. Even with one passenger rather than just the driver the car doesn't pull as well. Thing with the t-sport, with just 105bhp its half decent performance is largely down to the Yaris's low weight. As soon as you fill the tank or stick a passenger in the car that weight advantage (over e.g. other 105bhp hatches) is gone.

[GIDDLEPIN]

Anybody going to mention spoilers?

I was thinking of fitting one to mine but testing the handling characteristics of going round a roundabout at 30mph before fitting, then seeing what the comparison was with it on. ;)

[alfiejts]

As I found out in the pub car park last month - the rear spoiler's primary benefit is as somewhere for people to leave their empty beer cans on, as they pass the car....

Other than that, I fear it is another case of style over function - but it looks great though.....

[gar]

As I found out in the pub car park last month - the rear spoiler's primary benefit is as somewhere for people to leave their empty beer cans on, as they pass the car....

Other than that, I fear it is another case of style over function - but it looks great though.....

Surprisingly, racing cars DO fill their tyres with a different gas then usual... Can't remember what it is, nitr or something. Makes a small diff!

This debate is often bullishly argued over by motorcyclists, who try to save weight with lighter wheels, carbon bodywork etc. Even down to the "I've got a small numberplate to shave off a few ounces" Arguement... better off going without a few pies and having a toilet break before riding!

Don't forget though, that wheels are unsprung weight so the suspension will work better with less weight to push about!