2022 Tyres Thread

[henry]

In the meantime it’s worth noting that when Ferrari kit out for their clients to go 488s go racing they wear 315/705 19”.

That's interesting. I think it could just be because the 19" wheels are lighter, while still being large enough to clear the brakes.

In which case there would be no need to increase the rolling radius. But they do.

In my experience, having tried out 18" 40%, 17" 45% and 16" 50% tyres all of 225mm width on the same road car, the 18" tyres provided the most precise handling, the 17" tyres were in the middle (but I selected them as the 17" forged wheels were 2.5kg lighter than the OEM 18" wheels) and the 16" tyres, which were the minimum size to the clear the (small) 12" brakes, had noticeable slop, delay and vagueness in handling (not enough to compensate for the advantages of the 16" wheel being 3.5kg lighter than the OEM wheel).

Of course, different makes and model of tyre vary in their sidewall stiffness.

There was certainly not any increase in traction or grip with the 16" tyre compared to the 18".

Interesting. Did you tune the suspension for each different tyre? How did you compare the grip levels?

I can imagine that there was a subjective change in feel. I experience the same when I switch my summer/winter tyres. The summers are wider and lower profile. At my normal road speeds it makes no difference to me.

What matters to F1 teams is lap time. They will cope with tardy response in the same way they cope with turbo lag, or used to.

Another way of observing their desire for high conformance is their wish for low tyre pressures. I don’t know what tyre pressures they’ll run with the 18”. The regs have kept the tyre measurement test requirement at 1.4bar. The teams will, I think, want to run lower than now which may be possible since the magnitude of the tyre flex on the straight might reduce the fatigue levels.

[Tommy Cookers]

.....having tried out 18" 40%, 17" 45% and 16" 50% tyres all of 225mm width on the same road car, the 18" tyres provided the most precise handling.....

because (at high lateral loads) the 40% AR tyre's contact patch is distorted/displaced less than the 45%'s and the 50%'s
more precise handling implies this and so a higher ultimate lateral load than the 45% and 50%'s
much of the so-called slip angle is the angular displacement ie distortion of the contact patch

and fwiw elsewhere I have said that lower % AR needs higher inflation pressure

[Tim.Wright]

In the meantime it’s worth noting that when Ferrari kit out for their clients to go 488s go racing they wear 315/705 19”. Smaller rims and larger OD with a taller sidewall. Equivalent to 35% profile. So a knowledgeable F1 manufacturer does something different when outright performance is the goal.

I'd say more likely because there aren't any 20" racing slicks on the market - at least not from anyone reputable.

[henry]

In the meantime it’s worth noting that when Ferrari kit out for their clients to go 488s go racing they wear 315/705 19”. Smaller rims and larger OD with a taller sidewall. Equivalent to 35% profile. So a knowledgeable F1 manufacturer does something different when outright performance is the goal.

I'd say more likely because there aren't any 20" racing slicks on the market - at least not from anyone reputable.

Fair point.

[quote=henry post_id=872055 time=<a href="tel:1572870470">1572870470</a> user_id=509]
In the meantime it’s worth noting that when Ferrari kit out for their clients to go 488s go racing they wear 315/705 19”. Smaller rims and larger OD with a taller sidewall. Equivalent to 35% profile. So a knowledgeable F1 manufacturer does something different when outright performance is the goal.

I'd say more likely because there aren't any 20" racing slicks on the market - at least not from anyone reputable.
[/quote]

[henry]

.....having tried out 18" 40%, 17" 45% and 16" 50% tyres all of 225mm width on the same road car, the 18" tyres provided the most precise handling.....

because (at high lateral loads) the 40% AR tyre's contact patch is distorted/displaced less than the 45%'s and the 50%'s
more precise handling implies this and so a higher ultimate lateral load than the 45% and 50%'s
much of the so-called slip angle is the angular displacement ie distortion of the contact patch

and fwiw elsewhere I have said that lower % AR needs higher inflation pressure

I’m not sure about the correlation of handling precision and ultimate lateral, or longitudinal, load. I would expect a tyre with a a higher AR to have have a lower vertical spring rate, distort more vertically and so have a bigger, mainly longitudinal, contact patch. I’d expect this to generate higher lateral/longitudinal loads. This will be emphasised on aero cars with the much higher vertical loads.

I’d be interested in the reasoning behind the need for higher pressures on lower %AR.

[Tommy Cookers]

I’d be interested in the reasoning behind the need for higher pressures on lower %AR.

yes, so would I
the length of the contact patch is due to the relief of the tyre's internal radial load by the 'corner weight'
internal radial load (per unit of circumferential length) is due to inflation pressure and the tyre 'size'
yes if tyre 'size' is effectively tyre width (not sectional height) then higher pressure wouldn't be needed with lower %AR

we've all been in this situation - determining inflation pressure for lower AR than our car maker foresaw
but don't the car maker's figures for such ARs he recognises usually imply higher pressure is needed (with lower %AR) ?
his view is maybe driven by the bicycle analogue - a 2" tyre at 50 psi has the same compliance as a 1" tyre at 100 psi
pressure for pressure car maker's low AR tyre 'bump absorption' is qualitatively the same - but quantitatively less
so he might increase tyre pressure to help the low AR bump absorption quantity

our F1 case here is potentially informative (as unusually AR is the major variable and tyre OD and width are only slightly varied)

[AngusF1]

Here's an alternative to this silly idea.

How about Pirelli makes a high performance street tyre to fit a 13 inch wheel? They could demo them on the latest Mercedes super-saloon. We might discover that not only are they sufficiently sticky but actually provide sufficient ride comfort, too!

[JordanMugen]

How about Pirelli makes a high performance street tyre to fit a 13 inch wheel? They could demo them on the latest Mercedes super-saloon. We might discover that not only are they sufficiently sticky but actually provide sufficient ride comfort, too!

Where are Mercedes going to put the brakes? (Inboard?)

[trinidefender]

In the meantime it’s worth noting that when Ferrari kit out for their clients to go 488s go racing they wear 315/705 19”.

That's interesting. I think it could just be because the 19" wheels are lighter, while still being large enough to clear the brakes.

In my experience, having tried out 18" 40%, 17" 45% and 16" 50% tyres all of 225mm width on the same road car, the 18" tyres provided the most precise handling, the 17" tyres were in the middle (but I selected them as the 17" forged wheels were 2.5kg lighter than the OEM 18" wheels) and the 16" tyres, which were the minimum size to the clear the (small) 12" brakes, had noticeable slop, delay and vagueness in handling (not enough to compensate for the advantages of the 16" wheel being 3.5kg lighter than the OEM wheel).

Of course, different makes and model of tyre vary in their sidewall stiffness.

There was certainly not any increase in traction or grip with the 16" tyre compared to the 18".

"Slop, delay and vagueness in handling," would be more of a descriptor of sharpness of the steering and reaction of the car to steering inputs would it not?

How exactly did you measure if there was an increase in traction or grip or not? Was the same make and model of each tyre used on the same surface? It seems there are too many variables here to objectively make this claim.

Maybe you are right but there is something to be said for compliance provided by greater sidewall height allowing greater tyre deformity for grip, especially over road imperfections. The trade off being, as you described, more vague steering feel and less responsiveness to steering inputs.

That trade off seems perfectly fine in the road car world where ultimate grip isn't too much of a factor, even in 'high performance' models and steering feel is, arguably, more important to most buyers.

[trinidefender]

.....having tried out 18" 40%, 17" 45% and 16" 50% tyres all of 225mm width on the same road car, the 18" tyres provided the most precise handling.....

because (at high lateral loads) the 40% AR tyre's contact patch is distorted/displaced less than the 45%'s and the 50%'s
more precise handling implies this and so a higher ultimate lateral load than the 45% and 50%'s
much of the so-called slip angle is the angular displacement ie distortion of the contact patch

and fwiw elsewhere I have said that lower % AR needs higher inflation pressure

question...does, "a higher ultimate lateral load than the 45% and 50%'s" mean that you get higher lateral grip with the lower profile tyres? Even with the decreased contact patch of a tyre with higher sidewall stiffness (I.e. A more round tyre)?

[Tommy Cookers]

I would say yes - based on a semi-regular trackdays with a bit of car setup evolution
(25 years ago and going from 65% ? AR to 55%)

the sidewall stiffness is really the stiffness from inflation pressure used
(so in principle could be kept constant as there's no car maker standing over you)

and there's more lateral to be gained by a bit more pressure even if the patch is a bit smaller
more pressure makes the tyre stiffer directionally - which causes less distortion of the contact patch

the major benefit of lower AR is on directional stiffness
ie less difference between the wheel direction and the contact patch direction
giving less distortion of the contact patch distortion and so enabling more of its area to grip
agreed the last few years of F1 tyre design makes the low AR seem less than compelling

[JordanMugen]

Was the same make and model of each tyre used on the same surface? It seems there are too many variables here to objectively make this claim.

No I didn't, but here is a proper test done with the same tyres in each size:

Maybe you are right but there is something to be said for compliance provided by greater sidewall height allowing greater tyre deformity for grip, especially over road imperfections.

The more compliant sidewalls of the 17" tyre made a faster lap time in the wet where a pliable tyre conforms to the road better, but the low profile 19" tyre was, however faster in the dry...

Dry lap times
225/45 R17 > 1.39:30
225/40 R18 > 1.38:07
225/35 R19 > 1.37:90

Wet lap times
225/45 R17 > 1.05:05
225/40 R18 > 1.05:34
225/35 R19 > 1.05:60

Source: http://www.tyrereviews.co.uk/Article/Th ... -tyres.htm

(note: Goodyear's wet handling test track is a different circuit to the dry track, hence the shorter lap)

A further advantage of the wobbly broad sidewalks is that they allow the tyre contact patch to be larger and to conform more to irregularities in the track... They will struggle to match the current levels of traction on exit kerbs,

Anyhow, I think the suggestion that the 2021 18" F1 tyres are going to have a smaller contact patch than the 2019 13" F1 tyres due to less deformation, just makes no sense to me at all. The contact patch size, surely, is *only* a function of tyre pressure & corner weight and nothing else.

The aspect ratio may change the shape of the contact patch -- apparently with the advantage going to the low profile tyre in the case of a Golf GTI road car lapping a test track in the dry -- but I don't see how using a lower aspect ratio can reduce the area of the contact patch.

It is for this reason that the overall tyre diameter has been increased as well as the rim size.

I do not believe this is correct. Other categories like V8 Supercars use 680mm diameter 18" tyres (close to the 670mm diameter currently used for the 13" tyres in F1) and V8 Supercars seem to have no issue at all with riding kerbs and finding traction on bumpy and uneven surfaces...



IMHO, I think they are going to up 720mm tyre diameter in F1 solely for the purpose of bringing F1 tyre size into line with LMP1 tyre sizes.

[henry]

A further advantage of the wobbly broad sidewalks is that they allow the tyre contact patch to be larger and to conform more to irregularities in the track... They will struggle to match the current levels of traction on exit kerbs,

Anyhow, I think the suggestion that the 2021 18" F1 tyres are going to have a smaller contact patch than the 2019 13" F1 tyres due to less deformation, just makes no sense to me at all. The contact patch size, surely, is *only* a function of tyre pressure & corner weight and nothing else.

My way of thinking is that the tyre is a gas spring. The higher AR tyre has a greater gas volume than the lower. This means it will have a lower spring rate and so will deform more under the same load. By deforming more it will increase its contact patch area. In my model it is not solely dependant on initial pressure as you suggest. I may be wrong, I’m really thinking aloud here.

They use hollow spokes on F1 wheels. This will also reduce the spring rate. They may do that on the larger rims to increase compliance.

The aspect ratio may change the shape of the contact patch -- apparently with the advantage going to the low profile tyre in the case of a Golf GTI road car lapping a test track in the dry -- but I don't see how using a lower aspect ratio can reduce the area of the contact patch.

The road car, and the V8 supercar are non-aero so the load levels are nothing like F1.

IMHO, I think they are going to up 720mm tyre diameter in F1 solely for the purpose of bringing F1 tyre size into line with LMP1 tyre sizes.

They’re going to 725mm whilst I think LMP1 are 710. So similar but not the same. How “into line” that is I don’t know.

[henry]

I do not believe this is correct. Other categories like V8 Supercars use 680mm diameter 18" tyres (close to the 670mm diameter currently used for the 13" tyres in F1) and V8 Supercars seem to have no issue at all with riding kerbs and finding traction on bumpy and uneven surfaces...

I realise from this picture that I haven’t been clear when mentioning kerbs. I don’t mean that they will avoid kerbs in general, such as illustrated. The key area where tyre stiffness might impact is external kerbs on exit of corners. In fact anywhere traction is impacted. They’ll still keep cheating the length of tracks by hopping across inner kerbs.

I made a quick estimate of the change in tyre volume. It’s not as big as I thought. The 18” is around 90% of the 13”. Had they stuck with 670mm OD it would have been about 85%, not as big a change as I had expected.

Maybe the change will be less than I expect which will make the loss of inerters more problematic.

[AngusF1]

How about Pirelli makes a high performance street tyre to fit a 13 inch wheel? They could demo them on the latest Mercedes super-saloon. We might discover that not only are they sufficiently sticky but actually provide sufficient ride comfort, too!

Where are Mercedes going to put the brakes? (Inboard?)

https://eb28d90ee083bd53ca3c-b1a685dfca ... 23557b.jpg

Ha. Inside the wheels, just like normal. The engineers can figure it out.