Are 18 inch wheels a good thing?

[wolfhound]

I remember some F1 cars running 15 inch fronts in the early eighties. Williams FW07 or 08 spring to mind. I thought they lokked pretty good with them.

[mikuni]

Originally Posted by Richard Casto

I believe that typically in road cars, this type of increase in wheel diameter but with same tire diameter generally increases overall weight.

Typically in road cars this is true, but in road cars poor quality cast alloy is used to keep costs down, which is not a particularly light construction.

I run 18" wheels on my race car and they are forged aluminium and I can tell you, they are extremely light, less than half the weight of a similar cast alloy. F1 will use at least this technology, but I would bet with much lighter and stronger material than aluminium alloy.

In a given category the vehicles will run the maximum allowable rim diameter under the regulations. There are various reasons for this, but I would guaranty that if the regulations were opened so teams could choose anything between 13-18 inch they would go for the biggest possible.

[Adam43]

Road car wise, the main benefit is bigger brakes. However, despite an increase in mass over the years realistically most cars do not need discs and callipers that wouldn't fit under 17" wheels. Interesting I think the mass of cars over the last couple of years have got a tad lighter. Over the decades we've added more stuff to cars, but the recent push to reduce emissions has halted or even (slightly) reversed that.

My race series dictates a minimum 60 profile to make the tyres look right

Ultimately, as stated above, F1 wants bigger wheels because that is what people like.

My next road car? I'm going to try and get small - diameter for looks and ride and width for less grip and fun. However I like driving, which I know is not most car buyers cup of tea.

[NaBUru38]

The subject of the thread: is the change a good thing? The question is: what do they want?

Pirelli wants to promote big wheels, so they will be happy.

What do teams want? Faster cars? More reliaable cars? Cheaper cars? More road-like cars? To bet the other teams, no matter the rules?

What do fans want? I would like closer competition, lower cable television bills, and better road cars.

[Richard C]

Originally Posted by mikuni

Typically in road cars this is true, but in road cars poor quality cast alloy is used to keep costs down, which is not a particularly light construction.

I run 18" wheels on my race car and they are forged aluminium and I can tell you, they are extremely light, less than half the weight of a similar cast alloy. F1 will use at least this technology, but I would bet with much lighter and stronger material than aluminium alloy.

I think the use of cheap cast wheels is a common reason, but even with light weight wheels, I believe it still generally holds true for road cars This may, or may not carry over F1 specific designs or other racing series. We are beating a dead horse anyhow.


F1 wheels are forged and use specific magnesium alloys (per spec). I also believe they are run with design margins small enough that they have a relatively limited lifespan (i.e. they are not particularly "overbuilt"). I expect the same will be true with 18" versions.

Richard

[Richard C]

Sorry for the continued thread detour...

Originally Posted by Adam43

My race series dictates a minimum 60 profile to make the tyres look right

I think the trend of larger diameter wheels in road cars has made it harder to find performance tires for older cars that have smaller diameter wheels.

Originally Posted by Adam43

My next road car? I'm going to try and get small - diameter for looks and ride and width for less grip and fun. However I like driving, which I know is not most car buyers cup of tea.

I think I have read somewhere (not sure where) that part of what is pushing this in road cars is regulations the trend toward a higher waistline on cars. I think this is maybe driven by pedestrian impact regulations? Anyhow, with higher waistlines, to maintain classic proportions, designers use larger and larger diameter wheels/tires. Otherwise you have high waistline with small wheel wells.

Richard

[miatanut]

Originally Posted by Richard Casto

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

Thank you!

Looking online, I noticed it appeared that in road cars, larger rims for same overall wheel size does normally weigh more. I didn't know that. With racing cars I guess the whole difference is down to those sidewalls being a lot beefier than street car tire sidewalls, and the racing wheels being very light weight, and when it all washes out, the weight will be darn near identical.

[wnut]

Originally Posted by wolfhound

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.

The Lotus 49 was on 15" wheels = 1967.

1932 C Type Auto Union

Tire size: 5.25x17 front and 7x19 rear

[davyboy]

I think I'd like to see this configuration of wheels/tyres - I always thought they looked like a proper racing car. They're a mix of high and low profile.

[JacobP]

In my humble opinion, the rules of F1 racing have often evolved as a knee jerk reaction to the dominance of the top team. Right now we're observing unusually strong dominance of the Mercedes car, and while the battle of Mercedes teammates is entertaining, FIA is already scratching the head with regards to how it can balance out the field. If the low profile tires will struggle to put down the power and require suspension redesign, then this may neutralize the Mercedes power advantage.

From the visual perspective, the traditional F1 wheels look a lot better to me.

[P38 in workshop]

Given the amount of work that has been done to ensure that the current generation of cars are aerodynamically efficient,we may reasonably assume that the aero guys would want to retain their current ride heights to maintain the effect from the underside of the car.How much of a change of wheel/tyre size can be made before the angularity that the driveshafts operate at would cause trouble with the CV joints?

As for the weight of the rims.If the cross section remains the same-wouldn't the weight increase in proportion to the circumference of the wheel?This would mean that the rim would be 18/13 ths of the weight of the current rim and there would be the additional metal in the spokes.Two annular sections of rubber would almost certainly weigh less.

[Richard C]

Originally Posted by P38 in workshop

Given the amount of work that has been done to ensure that the current generation of cars are aerodynamically efficient,we may reasonably assume that the aero guys would want to retain their current ride heights to maintain the effect from the underside of the car.How much of a change of wheel/tyre size can be made before the angularity that the driveshafts operate at would cause trouble with the CV joints?

Just to be clear, other than a few photos of what has been done in years past, I don't think there is any speculation that they are considering change the tire diameter. So axle height at the wheel would remain unchanged. If for some reason they were to change the overall axle height (via tire diameter changes), I expect the teams would be looking at significant redesign of much of the car anyhow and I don't think that CV joint angularity would be an issue.

Originally Posted by P38 in workshop

As for the weight of the rims.If the cross section remains the same-wouldn't the weight increase in proportion to the circumference of the wheel?This would mean that the rim would be 18/13 ths of the weight of the current rim and there would be the additional metal in the spokes.Two annular sections of rubber would almost certainly weigh less.

I don't think you would just scale it up using 18/13 as some dimensions would remain as they are today (thickness of perimeter of rim using minimum spec and the hub area likely wouldn't grow). But that is likely not a bad place to start for a very quick estimate.

Richard

[P38 in workshop]

I thought I had described the situation where the circumference of the rim increased by the change in diameter and all other factors stayed the same.The circumference is related to the diameter.As a result the extra material would give an increase in weight of 13/18 ths of the weight of the original rim.

[Adam43]

The diameter of the tyre remains the same (or very similar). Surely?

[JeremySmith]

Originally Posted by davyboy

I think I'd like to see this configuration of wheels/tyres - I always thought they looked like a proper racing car. They're a mix of high and low profile.

That has balls...

[Casper]

It really is a bit of a yawn, big wheels, little wheels, so what. The major impacts are yet to be seen but will revolve around weight, tyre contact patch size, and side wall stability. If they change the offset (is it free?) then scrub radius and other factors will creep in. A side benefit will be the potential of bigger brakes and that is the absolute last thing F1 needs as the present stopping distances are way too short now negating the ability for a car to pass under brakes.

[JeremySmith]

Originally Posted by Casper

It really is a bit of a yawn, big wheels, little wheels, so what. The major impacts are yet to be seen but will revolve around weight, tyre contact patch size, and side wall stability. If they change the offset (is it free?) then scrub radius and other factors will creep in. A side benefit will be the potential of bigger brakes and that is the absolute last thing F1 needs as the present stopping distances are way too short now negating the ability for a car to pass under brakes.

I am just reacting as a fan.... The yaw and yawn and scrub radius, whatever that means ? does not really interest me....

I don't want the rims on a F1 car looking like the hoods local drug dealer, do I have to explain any more ???

[wnut]

Originally Posted by JeremySmith

I am just reacting as a fan.... The yaw and yawn and scrub radius, whatever that means ? does not really interest me....

I don't want the rims on a F1 car looking like the hoods local drug dealer, do I have to explain any more ???

I really don't care much what the cars look like or what their technical specs are, I simply want to see 2 hours of the best sprint racing in the world performed by 22 of the world's top drivers.

The rest is just window dressing and actually detracts from GP racing.

[Casper]

Originally Posted by JeremySmith

I am just reacting as a fan.... The yaw and yawn and scrub radius, whatever that means ? does not really interest me....

I don't want the rims on a F1 car looking like the hoods local drug dealer, do I have to explain any more ???

Appearance is more important than a technical change that will affect the cars and their performance? I don't know why you watch car racing, you may as well play marbles. The cars have been a caricature for years and the wheel size is not going to make them any more weird or ugly.

[JeremySmith]

Originally Posted by Casper

Appearance is more important than a technical change that will affect the cars and their performance? I don't know why you watch car racing, you may as well play marbles. The cars have been a caricature for years and the wheel size is not going to make them any more weird or ugly.

That is why I would like them to stop constantly dicking around with the cars and rules.. Aesthetics are a matter of opinion, I have one that is why I am voicing it..

Ohhh and I watch F1 and other forms of motor racing for the same reasons most fans do, to watch cars driven to the limit by the best pilots the world has to offer...

NOT racing that is controlled by a team of rule makers and aerodynamicist boffins..

*As foot note* most road car related tyre people I have spoken to think that low profile tyres are a pain in the neck, due to the lack of rubber between the tire, the rim and the road surface..

[bjohnsonsmith]

Here's an interesting piece on the affect 18'' wheels will have.

http://www.autosport.com/news/report.php/id/114907

[bjohnsonsmith]

Originally Posted by davyboy

A BT44, with Carlos Pace at the wheel.

[JeremySmith]

Paul Hembery explains in that article why this is not a good idea.. The tyres will have a "tendency to leave the rim" and the costs involved will be huge..

I was under the impression that F1 was attempting to control costs??

[miatanut]

Originally Posted by JeremySmith

Paul Hembery explains in that article why this is not a good idea.. The tyres will have a "tendency to leave the rim" and the costs involved will be huge..

I was under the impression that F1 was attempting to control costs??

The lower profile tires have worked out just fine in sportscar racing.

[JeremySmith]

Yes I agree they have and they look fine on a flat plane.. On a F1 car they are exposed and have a "wagon wheel" look to my eyes, but hey it's all subjective in the end it's only my opinion..

I am not opposed to change, I am opposed to change just for the sake of it..

I understand Michelins reluctance to come back to F1 because they produce the tires for LMP so then so why not have F1 use the same specification,if that is indeed even possible ??