Does tyre wear affect top speed?

[RH1300S]

You guys just love arguing!

You are both intelligent enough and sufficiently educated in mechanics to know that you both understand what determines ultimate top speed. Also you both know that cars very rarely achieve their ultimate potential speeds on a race track and they adjust their gearing accordingly to maximise the thrust available in all gears without over-revving the engine.

Good luck guys - please carry on............

[xpensive]

You guys just love arguing!
...
Good luck guys - please carry on............

And what is this very forum all about?

[Jersey Tom]

Why is this so hard to fathom, anyway you slice it this will never change as power is force times speed?

Wheel power (Watt) = Aerodynamic resistance (Newton) * Topspeed (meters per second)

Yes but you are considering absolute top speed for 'one' mechanical set up.

Not really... it's independent. The maximum potential top speed is governed by engine power and aero drag. You can screw up the gearing and have a setup with LESS than that number, but the maximum potential across and combination of gear arrangements is a fixed value that is drag limited.

[alelanza]

both intelligent enough and sufficiently educated in mechanics to know that you both understand what determines ultimate top speed.

Hmmm... I know xpensive is, I think you're being too kind with the other guy.

[ubrben]

Autogyro: Top speed is purely an engine power and drag issue.

As has been pointed out already top gear is designed to reach the peak power rpm give or take depending on slipstreaming strategy.

Yes this compromises gear ratios through the rest of the speed range. This is why 7-speed boxes are used with narrow torque bands to reduce this compromise.

A good way to highlight this in another way is do a lap sim with 6 fixed gears and then do the same sim with a CVT modelled. It's a big gain in lap time to use a CVT.

Ben

[ubrben]

As for the OP's original question. I think Tom's numbers show it's unlikely to be a big effect.

The other point was made about pressures increasing. If you actually look at presure vs. laps (my experience is GT2 and LMP2) you see a build-up at the start of the stint followed by a peak and then a gradual decline as the tread wears/compound performance drops off - basically the tyre generates less temp and the pressures come down.

All of these will vary the rolling radius a little.

So basically I go with Tom on this - it's negligible and falls into the category of intellectual masturbation in terms of quantifying it.

Ben

[DaveW]

Autogyro: Top speed is purely an engine power and drag issue.

To continue the off-topic theme... & drag is a function of aero set-up. Increasing D/F (& hence drag) increases corner exit speeds & lowers the top speed for a circuit, allowing shorter gears & increased acceleration once full throttle can be used. The increased D/F also means that full throttle is available earlier, further increasing acceleration away from low speed corners. Hence RBR (with more available D/F) qualified comfortably quickest at Barcelona even though they gave away up to 9 kph through the speed trap.

The logic suggests why aero & gear selection is a "coupled" optimization problem for most circuits & also explains why the "F-duct" is not an earth-moving innovation (the benefit occurs towards the end of a straight & requires longer gears. It has, therefore, only a small effect on lap time at best).

[RH1300S]

both intelligent enough and sufficiently educated in mechanics to know that you both understand what determines ultimate top speed.

Hmmm... I know xpensive is, I think you're being too kind with the other guy.

I think Autogyro knows plenty too......he just can't resist chucking little bombs at threads.

[Shrieker]

The logic suggests why aero & gear selection is a "coupled" optimization problem for most circuits & also explains why the "F-duct" is not an earth-moving innovation (the benefit occurs towards the end of a straight & requires longer gears. It has, therefore, only a small effect on lap time at best).

That is most probably correct. But it is an important asset for the race itself where it's not quite possbile to get closer to the car in front through the corners, isn't it ?

[DaveW]

That is most probably correct. But it is an important asset for the race itself where it's not quite possbile to get closer to the car in front through the corners, isn't it ?

I guess the device wouldn't be discarded willingly if it has no disadvantages &, all things being equal, it should help overtaking, at least in theory. However, the protracted Schuey/Button battle at Barcelona didn't exactly support the theory, I thought.

[Shrieker]

That is most probably correct. But it is an important asset for the race itself where it's not quite possbile to get closer to the car in front through the corners, isn't it ?

I guess the device wouldn't be discarded willingly if it has no disadvantages &, all things being equal, it should help overtaking, at least in theory. However, the protracted Schuey/Button battle at Barcelona didn't exactly support the theory, I thought.

I don't object, but the nature of the circuit had to do more with it. The straights follow fast flowing corners and the first turn doesn't favor overtaking at all. Despite all those, I think his team mate could have pulled off that move.

[DaveW]

I don't object, but the nature of the circuit had to do more with it. The straights follow fast flowing corners and the first turn doesn't favor overtaking at all. Despite all those, I think his team mate could have pulled off that move.

I agree that any advantage would depend upon the layout of the circuit. Oddly, however, I would reason that circuits with very long straights, or with straights following fast corners would most favour the "F-duct" concept. To be fair, I would not include Barcelona in a list of such circuits, although it is held to be an "aero" circuit.

You are probably right that Hamilton would be the more inclined to make a risky move & he seems to be better at coping with handling issues, but results this year to date suggest that Button isn't totally uncompetitive.

[xpensive]

As long as we live in a Newtonian world, power will always be speed times force, end of story.

[DaveW]

As long as we live in a Newtonian world, power will always be speed times force, end of story.

Absolutely for the first part, but not quite the end of story, it would appear. Force is the sum of drag and inertia force (mass * acceleration). There has been some confusion in this thread between terminal speed (when acceleration is zero) and maximum speed (determined by the circuit, vehicle set-up & rpm limit). The two are not necessarily the same thing. In fact, the last time I looked they were rarely the same for a conventional circuit.

[xpensive]

Perhaps something like this then, Dave?

Wheel power (Watt) = Aerodynamic resistance (Newton) plus accelleration (meters per second squared) times mass (kg) * Speed (meters per second)