Alloy wheel 'performance factor' ?

[nissangeek]

large doesnt always mean heavier, thats like saying a baloon is larger than a brick so it must be heavier

Such a pedant ! You misunderstood what I said.

[skyshack]

One piece alloy wheels are unless pushing around £1000 each are always heavier than steel.

2 or 3 piece can be lighter but it depends a lot on center section.

Race wheels are magnesium. Even the slightest bit of damage to the paint will result in rapid corrosion.

[bobbitt]

the faster cars do tend to have larger wheels but i suppose this is because it makes some sense and they are designed to match the vehicle in some way! i know f1 cars are not huge!

[Oyama]

Now hooooold on theeeeere , we're not driving torqueless n/a hondas here are we ? Just wind up 1 more psi and all the saved grams look pointless when you feel the difference .

[bobbitt]

large doesnt always mean heavier, thats like saying a baloon is larger than a brick so it must be heavier

it did in ancient egypt!

[zeppelin101]

Now hooooold on theeeeere , we're not driving torqueless n/a hondas here are we ? Just wind up 1 more psi and all the saved grams look pointless when you feel the difference .

Turning the boost up doesn't change unsprung weight or rolling resistance properties though does it?

[John Bennett]

I beg to differ How can large (by this you mean heavier right) wheels increase top speed ?

When the rev limiter in top limits your speed, the bigger the wheels, the faster the car is moving.

[nissangeek]

When the rev limiter in top limits your speed, the bigger the wheels, the faster the car is moving.

You mean bigger diameter wheels overall ?

[CNHSS1]

dont confuse wheel diameter and rolling radius of the tyre which is dictated by profile. Larger rolling radius = higher top speed.

unsprung weight doesnt make you car 'fast' it makes it handle better.

race split rims, billet centres, spun ally outers



but they can get damaged....



as has been said, if its not for track work and unless its against the clock, then the differences are tiny so the cost vs the gains may not be waht you need.
If you are competing lighter wheels and tyres as part of reduced unsprung weight is a no brainer

[croustibat]

One piece alloy wheels are unless pushing around £1000 each are always heavier than steel.

2 or 3 piece can be lighter but it depends a lot on center section.

Race wheels are magnesium. Even the slightest bit of damage to the paint will result in rapid corrosion.

i paid 350€ (around 310£) for 4 wheels, 18" x 7.5" , "used" but never installed on a car (the guy crashed the car beyond repair before fitting). they weight around 10kg each. i dont think any steelie in these dimensions weight less


john bennet > bigger wheel does not mean bigger wheel + tyre diameter.

[zeppelin101]

unsprung weight doesnt make you car 'fast' it makes it handle better.

True, but from my perspective anything that improves a car to make it quicker in any condition is an improvement over straight line speed only or acceleration only...

[Chriscooke]

I'm a little confused why people are getting defensive in this thread
I know next to nothing on how wheels effect performance with regard to unsprung wieghts so look at it as an ideal way to learn something

[John Bennett]

john bennet > bigger wheel does not mean bigger wheel + tyre diameter.

I know it doesn't mean that, I was just pointing out (to our departed guest) how a larger rolling radius can allow a higher top speed.

It's a bit confusing when 'wheel' can be taken to mean the 'wheel rim' or 'wheel rim and tyre'

[nitrodave]

as a wheel contributes to the unsprung weight, a lighter wheel will reduce the comfort the suspension provides. Also, as it is a rolling mass a heavier wheel will help with the cars moving momentum and when up to speed requires less energy to maintain that speed

[zeppelin101]

as a wheel contributes to the unsprung weight, a lighter wheel will reduce the comfort the suspension provides.

I'm not sure about that. A lighter wheel will allow the suspension to do it's job more efficiently. Likewise if you had lighter than standard arms and other parts of unsprung weight. The spring and damper will be able to react faster to undulations in the road surface. If they're correctly matched and setup I would imagine you would end up with a better ride quality.

[Chris B]

as a wheel contributes to the unsprung weight, a lighter wheel will reduce the comfort the suspension provides. Also, as it is a rolling mass a heavier wheel will help with the cars moving momentum and when up to speed requires less energy to maintain that speed

Completely incorrect at every level

The opposite is true, suspension works better with less unsprung mass

Also, heavier wheels mean more momentum (and inertia) and also more rolling reisitance due to extra mass, so the car requires slightly more energy to maintain speed, although the difference is rather small, it's mostly wind resistance at speed.


I use lightweight wheels. Most manufacturers don't seem to publish wheel weights and I don't know of any that publish inertia specs, I've looked into it but it's not worth the research.
Just buy the lightest you can afford (for performance), inertia, most likely, is fairly linearly proportional to wheel mass and radius.

My wheels are around 6-7KG (8.5JJ x 17") the tyres weigh around 10kg, so the majority of the inertia is in the tyres anyway IMO.

Interesting to hear how much lighter slicks are, I reckon Toyo R888s are light for similar reasons.
Pretty impressed with the mass and price of Image wheels too

[CNHSS1]

Interesting to hear how much lighter slicks are, I reckon Toyo R888s are light for similar reasons.
Pretty impressed with the mass and price of Image wheels too

slicks will be at least 2/3rds if not half the weight of an R888 for the same given size its shocking how light they are

EDIT:-

found this list i made

tyre and rim weight comparisons may 08

kumho 205/50x15 V70 list 1B 7" split rim 15.2kg
Kumho 225/50x15 V70 list 1B 8.5" split rim 16.3kg
No tyre 7" split rim 5.6kg
No tyre 8.5" split rim 6.05kg
No tyre 9" split rim 6.2kg
No tyre 10" split rim 6.35kg
Avon 8.5x21.5x15 crossply slick 9" split rim 13.7kg
Avon 10x21.5x15 crossply slick 10" split rim 14.8kg


worth noting the Kumhos are similar to the R888s
also worth noting that List 1B tyres are generally lighter than a normal road tyre too

also the 10" wide slicks were a good 2.5"-3" wider in terms of footprint as they are measured differently than road based tyre which tends to include shoulders (225 road tyre is around 195-200 max actual tread footprint)

HTH
Craig

[Chris B]

That's a saving of 3-5kg per corner over standard tyres

[CNHSS1]

That's a saving of 3-5kg per corner over standard tyres

no point eh?

[dunc]

I compared compomotive one piece rims with image and the weight difference was minimal if any at all unless you went with the billet stuf at double the price (probably getting on for triple the price of the compo's).

My compo's on the radical are 4.9Kg fronts and 5.2Kg rears IIRC (not 100% sure on those). Could probably find the comparitive weights between that and the image's if anyone's interested. Even the old school heavy rally alleys cats were only 6.1kg and 6.2kg, which is not too bad. The tyre is the vast majority of the weight here thouhg because the wheels are 13"

Think I worked it out that you could replace an entire compomotive for not much less than a rim section of a 3-piece so the advantage there was smaller than I thought as well.

Saying that if you're competing then it would probably be worth it for the billet items if you could

Dunc.