Weight of wheels...

[Shad]

How much of an impact does the weight of each wheel have on a cars' acceleration and handling?

My wheels currently are 9.7kg each, which is heavy. The wheels I'd like to get are 11.5kg each, which is heavier still. However most OZ wheels seem to be around the 6kg mark.

Any thoughts?

[Russ]

well, the bigger the wheel, the more surface area thats touching road, and the more grip there is. so to an extent, weight dont matter to much, what size wheels u got now, and what size u gettiin? but, if theres a point where ur gettin the best grip per inch of surface area, and u dont wanna go over that, cos ur carrying excess baggage

[Knoxville]

I'd always thought the best was to have light wheels that covered the maximum surface area possible because if the wheels are heavier no matter how much extra grip they add it still takes more turning force to shift em

[wilsonian]

weight of a wheel does matter. the compound it's made up of can add to this factor too. i have super leggars which i've been told are pretty light in the ways of alloys.

going back to my orginal statement - the less you car weights the more power to weight ratio there is.

what i wana know is would it inprove your grip etc if you did have heavy wheels (as theres more force going down onto the road...)

[TeePee]

Every kilogram extra in the wheels and tires has the same effect as adding 20kgs to the rest of the car. So you're effectively adding another 160kg, or driving around with two strapping passengers the whole time.

[Butuz]

Yep - because the wheels rotate the engine has to use more energy per wheel KG to get them rotating so as TeePee correctly said - wheel weight is equivalent to alot more general body weight.

Thats why i laugh at all the 1.2 corsas with 17" wheels and huge tyres, they dont seem to have noticed that all that extra rotating mass has taken off a second of their 0-60, and also made the car's handling far worse.

Butuz

[Jiff Lemon]

I laugh at them simply because they're 1.2 corsa's!

[Zak33]

Hold up.....glad I'm still here.

Anybody ever heard of....

UNSPRUNG WEIGHT?

No..thought not

here ya go....when a 1 ton car drives along a flat road, and goes over a pot hole, what drops into the pot hole? The whole car? or the wheel and tyre?

Right....so if it weighs LOTS....it needs a bigger control system to stop it bouncing.

People aways imagine that the CARS weight is critical..and it IS for performance and braking...but for HANDLING......not neccessarily so.

How do I explain this....? right........here goes...

If you pick up a wheel and tyre, now pick up a brake disk and a caliper...

put them all in a pile and pick them up....go on.....you big girl PICK THEM UP

Bloody heavy huh...

now imagine going flat out round a corner...and one wheel drops down a hole.....all you have is a spring and a shock absorber to keep it from staying down there....the body shell will only follow a split second after, and by then you're past the hole and onto another....

the SPRING allows the wheel to move down the hole, and then straight back up.....and the SHOCK ABSORBER stops it from bouncing up and down, and up and down afterwards.

The body shell is effected by less than about 10% of the movement. Its only cos there are hunfreds on lumps and bumps on roads that we need to think about it.....every imperfection moves the wheel up and down ...lots more than the body shell

Now.....for you to UNDERSTAND it....in your own house. You are gonna pretend to be a pair of suspension arms....

Get a Bag of sugar....and a box of tea bags.....

the bag of sugar is heavy....its a steel rim, with a heavy set of brakes etc.
the box of tea is light...like a good alloy with a low profile on it....

Hold one in one hand...the other in the other.

Arms out...go on....right out

now....flap your arms....FLAP ..go on F L A P

up AND down...fast....like the two wheels going up and down into pot holes.

now THATS what your wheels do ALL DAY ...even at 10 mph..imagine it at 100 mph in a forest...on a Subaru rally car...the springs and shockabsorbers do that ALL DAY LONG. you gotta CONTROL it...dont just flap to the furthest extension...try to reverse a few flaps really quickly....arms out straight....damn hard but EASIER on the light tea bags

now THATS WHY WE WANT LIGHT WHEELS AND BRAKES.,


Its why some cars have their brake disks INBOARD...ie at the top of the drive shaft, near the gear box, not in the wheel. Old Jaguars had their rear disks inboard.

After all.....who needs the brake to work on the wheel...the drive shaft is quite capable of slowing the wheel cos after all the power is fed in at that end...and having a brake disk and a caliper right up there halves the weight of the wheels bouncing power.

Hope that helps......and thats why you should NOT fit wheels that are just too big for your car....keep it in PROPORTION

[Angus]

Rotating mass has more effect than mass of the car - best way to experience this is if you get some lightweight wheels for a bicycle.

Because you have to turn the pedals and make the bike go; you definitely notice the difference.

If you wanted to put this to the test, I guess you could try and find a bike shop that will let you test ride their bikes.... pick two that are about the same weight - one with lightweight wheels (Mavic or similar) and one with heavy unbranded wheels.

If you get bigger wheels though the chances are that they're going to be heavier anyways - but surely you'll be saving on tyre weight.

[TeePee]

Actually that's not so. Low profile tyres tend to be heavier, since the sidewall is reinforced.

[Angus]

OK, I guess I can see that that would be so.

[Rave]

Hold up.....glad I'm still here.

Anybody ever heard of....

UNSPRUNG WEIGHT?

No..thought not

Hey, hey, don't jump to conclusions....I certainly know about it, I'm just not obsessed enough to hang around this forum all day. I actually learnt about it from my motorcycle reading, where it's arguably even more important.

imagine it at 100 mph in a forest...on a Subaru rally car

As I often like to boast, I did a couple of weeks work experience with the Subaru WRC team at Prodrive a few years ago. There wasn't a single bit on those cars that wasn't exquisite, but the wheels took the biscuit for me. The tarmac alloys were big, probably 18", but with slicks on they weighed less than the 14" steel wheels + tyres on my car. The 15"(ish) gravel wheels you could probably pick up with one finger. I seriously wanted to pinch some.

From an acceleration point of view, where the mass is on the wheel makes quite a lot of difference, the further it is out towards the edge, the harder it is to accelerate. That's why disc brakes on bicycles have a hidden benefit, they weigh more, but you can have a lighter rim and thinner spokes, which cuts rotating weight at the edge of the wheel. I was really surprised what a difference putting some big heavy tyres on my MTB made, it was suddenly a lot more sluggish to accelerate and the braking was poor too. That's why I don't mind splashing out for the best rims, spokes and kevlar beaded tyres now.

Rich :¬)

[unrealrocks]

Zac, very interesting ... never really thought about that sort of thing before!

Thats why i laugh at all the 1.2 corsas with 17" wheels and huge tyres, they dont seem to have noticed that all that extra rotating mass has taken off a second of their 0-60, and also made the car's handling far worse.

Lets not forget theres the difference between racers and boy racers One wants to go fast and one wants to look good Although sometimes the odd one does want to think they can go fast

[Mart]

This guys got a section on wheel/tyre mass on his Astra site. I think Zak posted a link to the site before. This is the link to the wheels page...

http://www.tomstickland.co.uk/astra/...els/wheels.htm