Re : The Alpine A110 (finally) cometh | PH Fleet

[otolith]

nickfrog said:

otolith said:

Lighter cars have no more or less lateral grip than heavier cars unless there is significant reliance on aerodynamic downforce. To a first approximation, the lateral force the tyres can generate through friction is proportional to the mass of the car, as is the force required for any particular lateral acceleration. F=uR, F=ma

I think you are confusing traction and lateral grip. Traction is indeed proportional to mass, the heavier the more traction.
Sadly it is the opposite for lateral as the centripetal/centrifugal forces trying to prevent the car from turning are proportional to the lateral weight transfers, which themselves are obviously proportional to the mass, at a given CoG.
So lat grip is inversely proportional to mass.

I'm really not.

The amount of grip a tyre has, whether lateral or longitudinal, is proportional to the downward force acting upon it, which is proportional to the mass of the car. The amount of grip you need in order to apply enough force for a given acceleration, whether lateral or longitudinal, is proportional to the mass of the car. They cancel out.

Where you get a difference in traction it's not to do with absolute mass but in longitudinal mass distribution and which wheels are driven. A heavier car has more traction only to the extent that it needs more traction.

Just take a look at the skidpan lateral g figures. Weight is not a factor.

https://fastestlaps.com/lists/top-grip-kings

[Onehp]

What matters in skid pad is tyre coefficient of friction, and basically balance in the sense that one axle doesn't skid first all the while when some of the wheels are driven.
Wider tyres do give more grip so all of the cars are wide tyred.

It gets more interesting in dynamic sitiations, quick change of direction, approachability of the grip limit, and car's response to disturbances to the grip as the suspension works the surface etc.

[nickfrog]

otolith said:

I'm really not.

The amount of grip a tyre has, whether lateral or longitudinal, is proportional to the downward force acting upon it, which is proportional to the mass of the car. The amount of grip you need in order to apply enough force for a given acceleration, whether lateral or longitudinal, is proportional to the mass of the car. They cancel out.

They would if a tyre's load vs friction relationship was linear. But it's not. Hence the fact that lateral grip in the lighter car will always be higher than in the heavier car, all other parameters being equal. The non linearity simply prevents you to add tyre to compensate, as that won't quite compensate, particularly in extremis.

https://www.paradigmshiftracing.com/racing-basics/...

Edited by nickfrog on Monday 20th January 15:41

[100 OCTANE]

The more information I find about the Alpine A110, makes me think how good the design is. https://www.alpinecars.com/en/wizards-of-wind/

[otolith]

nickfrog said:

otolith said:

I'm really not.

The amount of grip a tyre has, whether lateral or longitudinal, is proportional to the downward force acting upon it, which is proportional to the mass of the car. The amount of grip you need in order to apply enough force for a given acceleration, whether lateral or longitudinal, is proportional to the mass of the car. They cancel out.

They would if a tyre's load vs friction relationship was linear. But it's not. Hence the fact that lateral grip in the lighter car will always be higher than in the heavier car, all other parameters being equal. The non linearity simply prevents you to add tyre to compensate, as that won't quite compensate, particularly in extremis.

https://www.paradigmshiftracing.com/racing-basics/...

But all else is not equal - you are not running a 1400kg 911 GT3 on the same tyres and suspension as a 600kg Caterham 7. The Porsche will pull 1.24g

https://www.caranddriver.com/reviews/a26325525/201...

Can you think of any non-aero road cars which corner harder than 1.24g? An 850kg Elise won't. A 950kg Exige won't. An Atom won't. A Caterham won't.

[nickfrog]

otolith said:

But all else is not equal - you are not running a 1400kg 911 GT3 on the same tyres and suspension as a 600kg Caterham 7. The Porsche will pull 1.24g

https://www.caranddriver.com/reviews/a26325525/201...

Can you think of any non-aero road cars which corner harder than 1.24g? An 850kg Elise won't. A 950kg Exige won't. An Atom won't. A Caterham won't.

Are you saying that weights actually adds lateral grip?

There are too many parameters to take into account I agree and things are not equal. But if you do make them equal, which you can, then reducing weight will lower the amount of lateral weight transfer (obviously) and therefore the amount of centrifugal force exerted. Now you don't need to entirely capitalise on that and can run a relatively skinny tyres like the Exige, Elise, Atom and Caterham to gain in feel and handling. But you don't have to. The basic physics remain the same and the tyre friction coefficient tails off, that's the saillant fact.

[otolith]

nickfrog said:

otolith said:

But all else is not equal - you are not running a 1400kg 911 GT3 on the same tyres and suspension as a 600kg Caterham 7. The Porsche will pull 1.24g

https://www.caranddriver.com/reviews/a26325525/201...

Can you think of any non-aero road cars which corner harder than 1.24g? An 850kg Elise won't. A 950kg Exige won't. An Atom won't. A Caterham won't.

Are you saying that weights actually adds lateral grip?

No, certainly not. Generally, where road cars are concerned, vehicle weight makes no difference to lateral grip.

nickfrog said:

There are too many parameters to take into account I agree and things are not equal. But if you do make them equal, which you can, then reducing weight will lower the amount of lateral weight transfer (obviously) and therefore the amount of centrifugal force exerted. Now you don't need to entirely capitalise on that and can run a relatively skinny tyres like the Exige, Elise, Atom and Caterham to gain in feel and handling. But you don't have to. The basic physics remain the same and the tyre friction coefficient tails off, that's the saillant fact.

Whatever you did to it, you would be doing extremely well to match that Porsche's lateral g figure on street legal tyres, let alone to exceed it.

You may well gain some time in corners by taking weight out of a racing car - you definitely will if it has significant downforce. You may lose some time in corners even in a road car if you add excessive weight. But if you engineer a road car for its service weight, the actual value of that weight won't make much difference.

[Onehp]

It's more a matter of the tyre package optimised on the Porsche, as tyre load is relative to it's size also. A 991 GT3 has huge wheels and is, for the size of them, relatively light.

An A110s on the the other hand runs on PS4 which is the context of things, is a very road biased, comfortable and soft-sidewalled tyre. Stick on some semi's (as in previously posted vid) and watch the magic happen...

[DoubleD]

Onehp said:

It's more a matter of the tyre package optimised on the Porsche, as tyre load is relative to it's size also. A 991 GT3 has huge wheels and is, for the size of them, relatively light.

An A110s on the the other hand runs on PS4 which is the context of things, is a very road biased, comfortable and soft-sidewalled tyre. Stick on some semi's (as in previously posted vid) and watch the magic happen...

Sounds like you have a semi on already ha ha

[bcr5784]

Onehp said:

It's more a matter of the tyre package optimised on the Porsche, as tyre load is relative to it's size also. A 991 GT3 has huge wheels and is, for the size of them, relatively light.

An A110s on the the other hand runs on PS4 which is the context of things, is a very road biased, comfortable and soft-sidewalled tyre. Stick on some semi's (as in previously posted vid) and watch the magic happen...

Exactly put GT3 size wheels and Cup 2r tyres on and I have no doubt an Alpine, suitably set up would exceed the 1.24 G figure . Even Caterhams can exceed 1.24 G on road legal tyres. See https://www.youtube.com/watch?v=itgkSwNJ2k8 and you'll see 1.3 G exceeded. 2 reasons - the tyres are massive for the weight of car AND they are very sticky.

Edited by bcr5784 on Monday 20th January 18:35

[blueg33]

Onehp said:

It's more a matter of the tyre package optimised on the Porsche, as tyre load is relative to it's size also. A 991 GT3 has huge wheels and is, for the size of them, relatively light.

An A110s on the the other hand runs on PS4 which is the context of things, is a very road biased, comfortable and soft-sidewalled tyre. Stick on some semi's (as in previously posted vid) and watch the magic happen...

Surely, with that huge wing on the back, the GT3 has more downforce, hence more lateral grip.

[otolith]

bcr5784 said:

Onehp said:

It's more a matter of the tyre package optimised on the Porsche, as tyre load is relative to it's size also. A 991 GT3 has huge wheels and is, for the size of them, relatively light.

An A110s on the the other hand runs on PS4 which is the context of things, is a very road biased, comfortable and soft-sidewalled tyre. Stick on some semi's (as in previously posted vid) and watch the magic happen...

Exactly put GT3 size wheels and Cup 2r tyres on and I have no doubt an Alpine, suitably set up would exceed the 1.24 G figure . Even Caterhams can exceed 1.24 G on road legal tyres. See https://www.youtube.com/watch?v=itgkSwNJ2k8 and you'll see 1.3 G exceeded. 2 reasons - the tyres are massive for the weight of car AND they are very sticky.

Yep, that kind of cornering performance has everything to do with tyres and sod all to do with weight.

[blueg33]

otolith said:

nickfrog said:

otolith said:

I'm really not.

The amount of grip a tyre has, whether lateral or longitudinal, is proportional to the downward force acting upon it, which is proportional to the mass of the car. The amount of grip you need in order to apply enough force for a given acceleration, whether lateral or longitudinal, is proportional to the mass of the car. They cancel out.

They would if a tyre's load vs friction relationship was linear. But it's not. Hence the fact that lateral grip in the lighter car will always be higher than in the heavier car, all other parameters being equal. The non linearity simply prevents you to add tyre to compensate, as that won't quite compensate, particularly in extremis.

https://www.paradigmshiftracing.com/racing-basics/...

But all else is not equal - you are not running a 1400kg 911 GT3 on the same tyres and suspension as a 600kg Caterham 7. The Porsche will pull 1.24g

https://www.caranddriver.com/reviews/a26325525/201...

Can you think of any non-aero road cars which corner harder than 1.24g? An 850kg Elise won't. A 950kg Exige won't. An Atom won't. A Caterham won't.

Evora 430 GT does 1.5g and is heavier than Alp, Exige etc.

Exige and to a lesser degree the Elise have some aero. The Alpine also has some aero and I think the Cayman does. A GT3 certainly does.

[bcr5784]

blueg33 said:

Evora 430 GT does 1.5g and is heavier than Alp, Exige etc.

Exige and to a lesser degree the Elise have some aero. The Alpine also has some aero and I think the Cayman does. A GT3 certainly does.

Sure as hell the Caterham, far from having having downforce has significant front end lift at the speeds in the video.

[otolith]

It’s all pretty much irrelevant in a road car anyway, how often is your cornering speed limited by grip rather than by vision? The advantage of lighter cars is how they feel, not how fast they go, IMO.

[Gary C]

otolith said:

It’s all pretty much irrelevant in a road car anyway, how often is your cornering speed limited by grip rather than by vision? The advantage of lighter cars is how they feel, not how fast they go, IMO.

Well said, in fact too much grip can spoil the fun.

[TurboBlue]

bcr5784 said:

Gad-Westy said:

Original A110
140ps = 138bhp
670kg
So 206 bhp/tonne

Current A110
249bhp
1103kg
So 226 bhp/tonne

Only 20bhp difference. Though the lighter car's figures always falls off faster once you start adding drivers and fuel into the equation.

True - but when you look at the actual performance the A110 II is in a completely different league.Even allowing for all sorts of fudge factors it's difficult to make the sums add up.

I've dug out an old Autosport test by John Bolster from May 1971 when they drove the A110 1600 S, which I think was the last and fastest of the original A110's. He drove it from Dieppe to Geneva and back, they even managed to fit two spare wheels with studded tyres in the car. Anyway, performance figures are quoted are below, (these may be factory or Autosport's own figures, at this distance in time, who know?) I've put the new A110 figures in brackets (from the Autocar road test of May 2018 - forty seven years later)

Max power is quoted at 138bhp (gross) and 125bhp (net)
No torque figure given

Max speed 127 mph (155mph)

Standing quarter-mile: 15 seconds/92mph (13.2/110)

Accereleration (mph/secs)
0-30mph in 2.5 seconds (2.0)
0-50 in 5.1 (3.7)
0-60 in 6.3 (4.7)
0-80 in 11.6 (7.2)
0-100 in 18.2 (10.8)

Weight is given at 14cwt, which is 1,568 long lbs or 711kg. I'd of thought this would be well over 800kg if measured like-for like with the current car (1103kg)

You can see where all the extra performance is made available by the quicker gearbox and the much flatter torque curve but equally you can see just how blisteringly quick the original car would be when it was working in it's element; that would have the added advantage of being available at fast road speeds, hence more accessible and more fun!

[bcr5784]

TurboBlue said:

Max power is quoted at 138bhp (gross) and 125bhp (net)
No torque figure given

Max speed 127 mph (155mph)

Standing quarter-mile: 15 seconds/92mph (13.2/110)

Accereleration (mph/secs)
0-30mph in 2.5 seconds (2.0)
0-50 in 5.1 (3.7)
0-60 in 6.3 (4.7)
0-80 in 11.6 (7.2)
0-100 in 18.2 (10.8)

Weight is given at 14cwt, which is 1,568 long lbs or 711kg. I'd of thought this would be well over 800kg if measured like-for like with the current car (1103kg)

You can see where all the extra performance is made available by the quicker gearbox and the much flatter torque curve but equally you can see just how blisteringly quick the original car would be when it was working in it's element; that would have the added advantage of being available at fast road speeds, hence more accessible and more fun!

Pretty impressive - about the same as an Elan Sprint (or an E type of that time!). That said the 1600SC with 140bhp net does not seem to be as quick - see http://www.zeperfs.com/en/match1919-1351.htm

[bcr5784]

TurboBlue said:

You can see where all the extra performance is made available by the quicker gearbox and the much flatter torque curve but equally you can see just how blisteringly quick the original car would be when it was working in it's element; that would have the added advantage of being available at fast road speeds, hence more accessible and more fun

While there is not doubt that driving in the past was more fun- far less traffic, no speed cameras etc would (say) a new A110 be less fun than an Elan on the same roads in the 1970s? The Elan's lack of width would be a BIG plus so personally I suspect it would be my preference - but as today, the A110 is far more user friendly on a day to day basis.

[anonymous-user]

bcr5784 said:

While there is no doubt that driving in the past was more fun.....

Wrong. You're just driving the wrong car!