Why do F1 still run 13" tyres?

[Crazy_Pigal]

This is something that's been bugging me for a while, I sure someone out there knows why F1 still runs 13" tyres?
It appeared that with the change back to slicks for 2009 we were also going to see an increase to 14" rims (I don't know where 14" came from!) & an increase in rear tyre width, but this all got lost when the definitive 2009 regs came out, I think this was a real lost opportunity. I would love to have seen bigger rims (more like 17 to 18") & wider rears on the 2009 generation cars for a number of reasons:

1 - Looks, larger rims look better, that's the main reason road car wheels are so much bigger than they used to be.

2 - Again a visual thing, but wider rears would fill the gap between the new rear wing endplates and the tyres, the (mockup) pictures of the 2009 Ferrari in Thursdays Autosport show how silly the 2009 rear wing looks with skinny tyres (I'm not just blaming the tyres here, the wing looks silly on its own, but wider tyres would help).

3 - Wider tyres (and/or bigger diameter) give greater drag & screw with the aero - the FIA have excepted that F1 needs more mechanical grip & less aero, this can only help reduce the overtaking problem.

4 - The FIA says they want road relevent technology in F1, if KERS is the future then one place to put it is in the wheel hubs, fitting a motor/generator into an 18" rim may be a very relevent technology & a damn sight easier than squezzing it into 13".

5 - Racing tyres on large rims do work, Le Mans tyres are 18" rims, & 406mm width, an F1 car on tyres like that would look sooooo much better!

I read this week that the 2009 slicks demand such a forward bias weight distribution that it could make KERS unviable, Bridgestone offered the teams skinnier fronts to help the balance, & the teams turned it down, No! surely wider rears would have been a far better offer?

OK, rant over, I'll be interested to know what I've missed!

[johnh875]

Load capacity is one factor - with the huge amounts of downforce (even under the new regs), the tyres have to cope with a large load by racing car standards along with the high speed. All things being equal, one of the determining factors of how much load a tyre can take seems to be a function of how much air is inside it.

Also a larger diameter rim weighs more, and has more effect again on rotational inertia.

[Duff_44]

One rumored reason to keep the wheels small is that teams can't fit bigger brake rotors inside them...

I've never heard any 'official' reason for having the smaller wheels

[andy_b]

its actually because if they went any larger, Bernie wouldnt be able to see over the tyres on his gridwalk

[JeremySmith]

Originally Posted by andy_b

its actually because if they went any larger, Bernie wouldnt be able to see over the tyres on his gridwalk

Who would have thunk it!....

[broadrun96]

The biggest reason is most likely weight, teams wouldn't go to a bigger wheel because the weight increase and decreased air volume would be a larger performance loss than gain. If teams really wanted bigger wheels it would have been brought up years ago in negotiations, but haven't even heard a peep about it.

[FPV GTHO]

They still run 13 inch rims because they still run 5mm suspension travel.

17-18 inch rims would need to have the suspension systems radically changed.

[Sodemo]

They should have undoubtedly gone for wider rear tyres.

A real missed opportunity.

As was passing on the wider chassis.

They really haven't a clue.

[tristancliffe]

Originally Posted by Crazy_Pigal

1 - Looks, larger rims look better, that's the main reason road car wheels are so much bigger than they used to be.

A matter of opinion. Nothing is worse to look at than a road car that should have 13" wheels with 18" wheels crammed on. This includes 'modern' cars when the 18" wheels come as standard - they'd look so much better with sensible wheels.

Originally Posted by Crazy_Pigal

2 - Again a visual thing, but wider rears would fill the gap between the new rear wing endplates and the tyres, the (mockup) pictures of the 2009 Ferrari in Thursdays Autosport show how silly the 2009 rear wing looks with skinny tyres (I'm not just blaming the tyres here, the wing looks silly on its own, but wider tyres would help).

No, they wouldn't, unless you mandated that the extra tyre width was all inboard of the current tyre position. Which would look stupid and mess with suspension geometry.

Originally Posted by Crazy_Pigal

3 - Wider tyres (and/or bigger diameter) give greater drag & screw with the aero - the FIA have excepted that F1 needs more mechanical grip & less aero, this can only help reduce the overtaking problem.

I very much doubt aerodynamics are quite as simplistic as that, but I get your point. However, giving extra drag from wider rear tyres would only have a small effect on the aerodynamics, so downforce wouldn't be altered that much. Combine that with artificially narrow tracks and wide rear tyres (from point 2) and you end up back where you started but with more cost and weight. Which is silly

Originally Posted by Crazy_Pigal

4 - The FIA says they want road relevent technology in F1, if KERS is the future then one place to put it is in the wheel hubs, fitting a motor/generator into an 18" rim may be a very relevent technology & a damn sight easier than squezzing it into 13".

KERS isn't the future. And they won't want it in the uprights because of unsprung weight and the fact that two small energy storage devices will be less efficient than one larger one.

Originally Posted by Crazy_Pigal

5 - Racing tyres on large rims do work, Le Mans tyres are 18" rims, & 406mm width, an F1 car on tyres like that would look sooooo much better!

Matter of opinion. Are the Le Mans cars mandated to use extra large wheels, or have they done it through choice?

Originally Posted by Crazy_Pigal

I read this week that the 2009 slicks demand such a forward bias weight distribution that it could make KERS unviable, Bridgestone offered the teams skinnier fronts to help the balance, & the teams turned it down, No! surely wider rears would have been a far better offer?

Presumably a law of diminishing returns. A 10% wider rear tyre might only give 1% more grip, but a 10% narrower front might give a reduction of 8%.

[MagnetON]

increased dimensions = increased drag = more aero fardledardling.

Totally a missed oppertunity but they should have went with just two very narrow wheels, one at the front and one at the back, some aero bodywork at the front and just have the driver sit on top of it, hunched over so that his back becomes part of the aero.....

[Marbot]

Originally Posted by MagnetON

Totally a missed oppertunity but they should have went with just two very narrow wheels, one at the front and one at the back, some aero bodywork at the front and just have the driver sit on top of it, hunched over so that his back becomes part of the aero.....

Err...that would be bike racing would it not?

But as you say,a totally missed opportunity!

[Glen]

I seem to remember it being an easy way to limit brake size being one of the reasons.

I can't see why a proper serious technical formula like F1 would want anything to do with the Max Power/Nova-boy school of car design.

And why does choosing car spec for performance reasons mean the authorities have "no clue" - or was that a joke?

[RaiseYourFist]

Do any open wheelers run with such big wheels?
I think that every type that i've seen runs with decently small wheels

[GolddustMini]

singleseaters would look horrible on big wheels with rubber band tyres on them

[Marbot]

Champ-car wheels were larger if memory serves.They were also fitted with Bridgestone (Firestone) tyres.