Are 18 inch wheels a good thing?

[GTRMagic]

Originally Posted by miatanut

Thank goodness, I'm not going crazy!

I was thinking with a whole lot of rubber being replaced by, well, nothing, and a little more metal needed to make the wheel, the whole thing should be lighter, not heavier.

I'm used to 16's on a small car, and I think they look nice. I have thought the F1 tire to wheel proportions have looked rather old fashioned for many years.

With relatively out of control air-filled rubber being replaced by highly-refined dampers, the lower profile should give a little better corning.

I vote thumbs up.

All that is being replaced is the sidewalls, as the profile is lower yet I wouldnt be surprised if the outer circumference isnt almost identical. So you replace a sliver of rubber with a significant structural piece of metal, its not abnormal to expect weight to increase...

[Richard C]

Originally Posted by wnut

A large rim with a low profile tyre properly designed should always be lighter than the same diameter wheel with a high profile tyre. I guess they just machined up a handy set of aluminium road wheels to do the demonstration laps!

I haven't done the math yet to verify, but my gut does not agree with you. I think that all things being equal as you increase the size of the wheel you have to increase the amount of wheel material while reducing the amount of tire material. I am assuming the wheel material (magnesium or aluminum) is going to be heavier than the wheel material (generally rubber). Overall, I expect the entire 18" wheel tire combo to be slightly heavier than the current 13" setup.

Richard

[NaBUru38]

I'm used to fat tyres, but I'm fine with the 18 inch wheels.

Now, those noses and wings are so ugly that I barely notice the new wheels.

[miatanut]

Originally Posted by GTRMagic

All that is being replaced is the sidewalls, as the profile is lower yet I wouldnt be surprised if the outer circumference isnt almost identical. So you replace a sliver of rubber with a significant structural piece of metal, its not abnormal to expect weight to increase...

You are replacing three or more inches of stiff, relatively thick, cantilever rubber tire sidewall with mostly air, except for a few spindly spokes and a little more rim metal. With the moment going up as a function of a a square of the sideway depth, the much shorter sidewall will need a LOT less rubber and cords to resist the same lateral load.

So, my hunch could be wrong, and in any case, I think it is close to an even trade, but what wnut described is what I would expect.

Originally Posted by Richard Casto

I haven't done the math yet to verify, but my gut does not agree with you. I think that all things being equal as you increase the size of the wheel you have to increase the amount of wheel material while reducing the amount of tire material. I am assuming the wheel material (magnesium or aluminum) is going to be heavier than the wheel material (generally rubber). Overall, I expect the entire 18" wheel tire combo to be slightly heavier than the current 13" setup.

Richard

Have you ever lifted a racing tire? The tread is paper thin because they are trying to make it light, but those sidewalls are anything but thin and the weight of that rubber adds up.

[mikuni]

Yeah, racing slicks are heavy, rubber in general is, while aluminium/magnisium/titanium/carbon fibre/what ever they end up using is not.

If they can get the look right, I'm all in favour of this from a racing car perspective if it doesn't look ricer. I'm a bit conerned because of the sparks and glowing brake disks, it makes me wonder whether this change is being suggested for the wrong reasons.

But in reality 13" tyres are well out of date, they are holding the cars back. Lets make these changes, get the suspension working properly and move into the future.

[GTRMagic]

I thought it was odd that Pirelli went and built a new prototype tyre for it when they likely already have the product and technology in their prototype sports car tyre range...

[Casper]

Originally Posted by TrapezeArtist

So true. I am at a total loss to understand why manufacturers and the car-buying public sacrifice so much refinement and ride quality for some perceived improvement in handling that cannot be used under modern road conditions.

Brakes on road cars have become far better due to bigger wheels allowing bigger brakes. Also cars as they have become heavier create problems in the side wall so it over comes that as well. Put a car that weighs 2000kg on a 100% profile tyre and see what you think after a drive, you won't like it. The rubber bands that are fitted are going a bit far but 50% to 60% presents a good compromise for the road.

[wnut]

On this video you can see the resonance in the F1 tyres 0.15 to 1.30mins:

http://www.youtube.com/watch?v=n_I3hT-qBUw

Here is deformation of a Goodyear F1(Model) tyre on a rig

http://www.youtube.com/watch?v=7mVR-u6lW1w

On a separate note, I don't know whether low profile tyres will make the racing better though, they will make the simulations more accurate and further disadvantage the lower order teams. The ride height of the cars will be far more controlled and help the aerodynamics considerably too.

[BertMk2]

With the lower profile the suspension will have to take more of the load - but will they also have to take more care over kerbs? Are the lower profile tyres going to result in more damaged rims if drivers are aggressive on kerbs? (or am I applying too much "country lane" driving theory here )

[Casper]

I bet the teams do not back off the spring and damper rates too far, if they do it at all. The cars will be rock hard to maintain the ride height and optimise the aero. Was it Alan Jones who retired due to cars with no suspension compliance and the physical beating the drivers were taking when skirts were all the go?

[tristancliffe]

A change based not on handling improvements, economy improvements or some other measurable dynamic improvements. It is based on the fact that road cars have bigger and bigger wheels due to a successful marketing campaign designed to lure idiots to spend money on bigger wheels.

There is no road car in the world that benefits from >14" wheels in my opinion.

When less regulated championships choose massive wheels (because there is a benefit) due to proper performance reasons then I'll agree to the change.

[Casper]

Originally Posted by tristancliffe

A change based not on handling improvements, economy improvements or some other measurable dynamic improvements. It is based on the fact that road cars have bigger and bigger wheels due to a successful marketing campaign designed to lure idiots to spend money on bigger wheels.

There is no road car in the world that benefits from >14" wheels in my opinion.

When less regulated championships choose massive wheels (because there is a benefit) due to proper performance reasons then I'll agree to the change.

For a start they are not asking for your permission so that is cleared up. As for larger wheels on road cars try stopping a heavy modern car from high speed with brakes that go inside a 14" wheel and let me know how it goes.

[SAMD]

Originally Posted by TrapezeArtist

So true. I am at a total loss to understand why manufacturers and the car-buying public sacrifice so much refinement and ride quality for some perceived improvement in handling that cannot be used under modern road conditions.

In that case, prepare to be blown away with info regarding that particular 'car-buying public, sacrifice'
Its 'cos they look good.


I have a friend that works in the Tech dept of our BMW dealers here in BT and he informs me he would be a millionaire if he recieved the appropriate amount for every test drive he has taken with a customer who complains that his new BMW doesnt drive anything like the test car and it is the same car except for the wheels the salesman suggested. My son drives a Vauxhall that arrived with 19in wheels. Personally I prefer a higher sidewall and I ran my 735 BMW with 17in Alpinas and a reasonably high tyre for the very reasons you, no doubt, would cite.

[davyboy]

I more or less agree with Tristan here.

Who is ultimately responsible for introducing changes to F1 ? I can't fathom what they're at. Having managed to get buy in for penis noses, cars that make farting noises and smell of burning electrical cabling as they waft by, they've now decided that F1 needs a Max Power look - 18" wheels and spark generators. It's like reading something from Viz !

[Mike E]

It seems doubtful to me that an engineer would choose high profile tyres over low profile tyres if looking for lap time because of all the distortion in the tall tyre. At the moment a significant amount of the compliance in the car is provided by the tyres and the suspension is rock hard. This is an unintended consequence of driving around on four partially inflated beachballs. With low profile tyres some of that compliance will have to move to the springs/dampers, but really it's just an opportunity to run with virtually no suspension movement at all in the interests of consistent aerodynamic performance.

Anyway, it doesn't really matter. The guys writing the rules will decide one thing or another and that will be that.

One potential positive is that these tyres could result in fewer front wing endplate vs sidewall punctures because of the lack of sidewall.

[Casper]

Do F1 drivers suffer from medical issues caused by driving vehicles with hard suspension? I know that tracks are generally fairly smooth except in the braking area. Kart drivers suffer in some circumstances and these cars will be akin to karts as were the skirted cars years ago. There is no way the engineers are giving up any opportunity to keep the ride height as stable as they can.

[Oldtony]

Originally Posted by SAMD

In that case, prepare to be blown away with info regarding that particular 'car-buying public, sacrifice'
Its 'cos they look good.

I

Don't know if it happens elsewhere but the standing joke around here is the young posers driving Hi-Lux 4x4s fully equipped with winches, tow rigs, bullbars, paddock bashing spotlights etc. sitting on 19"alloys with ultra low profile tyres.

[davyboy]

Originally Posted by Casper

Do F1 drivers suffer from medical issues caused by driving vehicles with hard suspension? I know that tracks are generally fairly smooth except in the braking area. Kart drivers suffer in some circumstances and these cars will be akin to karts as were the skirted cars years ago. There is no way the engineers are giving up any opportunity to keep the ride height as stable as they can.

Yes they do. A lot of older, ex single seater racing drivers have chronic back problems by the time they're in their 50s. A lot of that's down to the decade or so they spent in karting when they were younger, but F1 and the junior formulae had their part to play too.

[TheNo1F1Fan]

Originally Posted by TheNo1F1Fan

If these images can't be viewed try these ones:
http://www.nogripracing.com/gallery/...p?photo=164760
http://www.nogripracing.com/gallery/...p?photo=164759

[Casper]

Originally Posted by Oldtony

Don't know if it happens elsewhere but the standing joke around here is the young posers driving Hi-Lux 4x4s fully equipped with winches, tow rigs, bullbars, paddock bashing spotlights etc. sitting on 19"alloys with ultra low profile tyres.

Yes, they are all show, I wouldn't like to bury a modern 4WD in a river with all the electronics they have now. We used to take the doors off the Landy and hit it with a fire hose inside and out.

[Catingaround]

I don't want to like it, I'm generally not a fan of the big wheel trend on retro-mod muscle cars but I was surprised to find them appealing. fwiw I think they look pretty cool.

[miatanut]

Originally Posted by BertMk2

With the lower profile the suspension will have to take more of the load - but will they also have to take more care over kerbs? Are the lower profile tyres going to result in more damaged rims if drivers are aggressive on kerbs? (or am I applying too much "country lane" driving theory here )

Sportscars went to lower profile years ago, and that doesn't seem to stop them kerb hopping at Le Mans, although there is an occasional puncture that is probably a result of it.

[P38 in workshop]

Originally Posted by wnut

I don't think you can read anything into the weight P38:

" With the concept tyre designed principally to showcase aesthetics rather than performance, and a general-purpose compound, lap times were not the focus. Instead, the objective was to gauge reaction to the very different new design, which received the thumbs up from most observers."

A large rim with a low profile tyre properly designed should always be lighter than the same diameter wheel with a high profile tyre. I guess they just machined up a handy set of aluminium road wheels to do the demonstration laps!

The low profile tyres provide a bigger more stable contact patch for the same wheel diameter, and would avoid the tyre resonance issues, you sometimes see huge tyre shake in the super slow motions after a wheel jumps a kerb.

The only reason that super low profiles are not the best road tyres is that the public roads are not smooth and full of ruts and potholes which the low profile tyres cannot absorb because of their lack of depth in the side wall to cushion road shock.

On a perfect surface there is no question that a low profile setup is the way to go.

While I would agree that a wheel with a tyre of high aspect ratio will weigh more than the same wheel with a low aspect ratio tyre,this is not what we seem to be facing the prospect of.If the 13 inch wheel with the high aspect ratio tyre has the same rolling radius as the 18 inch wheel with the low aspect ratio tyre we have the situation where the rubber sidewall has been partly replaced by metal spokes and rim.Metal normally weighs more than rubber and air and this is where I believe the weight increase has come from.There may also need to be an increase in section of the spokes as the more rigid sidewalls may transmit higher peak loadings.

The cynic in me wonders whether the 18 inch proposal is to soften us up so that the 15 inch they revise it to looks reasonable and may be what they really wanted all along.

[Richard C]

Originally Posted by miatanut

You are replacing three or more inches of stiff, relatively thick, cantilever rubber tire sidewall with mostly air, except for a few spindly spokes and a little more rim metal. With the moment going up as a function of a a square of the sideway depth, the much shorter sidewall will need a LOT less rubber and cords to resist the same lateral load.

So, my hunch could be wrong, and in any case, I think it is close to an even trade, but what wnut described is what I would expect.

So I actually attempted some quick calculations. I had to make a number of assumptions. I assumed that the shoulder and bead construction would remain relatively the same (from an amount of material perspective) and that the reduction in material would come from the part of the sidewall that is not bead or shoulder. The shoulder and tread were ignored as I didn't see addition or subtraction of material. I had to make assumptions as to thickness of the sidewall and bead sections (with the bead section assumed to being about 2x as thick as sidewall). Dimensions for the wheels required fewer assumptions as there is existing specs for things like general dimensions, minimum material thickness and material (magnesium).

The key point is that while you loose a great deal of weight in sidewall material (roughly 55% reduction) you also gain weight in the bead material (roughly 36% increase). If it is not obvious as to why there is an increase in the bead material, that is due to the larger circumference of that part of the tire. Regardless, the overall weight of the tire is reduced as expected. The wheel will pickup at least 725g of weight just via the extra material needed for the outer rim due to circumference alone (assuming 3mm thickness and 350mm width). Given the numbers I was seeing, I stopped before trying to figure out the weight of additional spoke material. At that point it was showing the overall tire being about 500g lighter. Add in spoke material and the new wheel/tire combo might weight the same, less or more. It looks to be very close. So close that given my many assumptions, I don't think I can generate an answer to the question of the new combo being lighter or heavier than the old combo. I believe that typically in road cars, this type of increase in wheel diameter but with same tire diameter generally increases overall weight.

It is an interesting exercise, but I don't think we will know a definitive answer until those who have the details (wheel and tire manufacturers) publish the values. And overall, I agree with the many posts above, that given a set tire diameter, there are a number of performance advantages of having a lower profile tire.

Richard

[wolfhound]

Originally Posted by miatanut

Sportscars went to lower profile years ago, and that doesn't seem to stop them kerb hopping at Le Mans, although there is an occasional puncture that is probably a result of it.

If I remember correctly when Porsche launched their 935 in '76 it had 19 inch wheels on it, so F1 is only catching up with sportscars about 40 years later.