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Mycroft said:
200lb downforce gives 280lbs of sideways resistance on those graphs [roughly]...

At 400lbs there is 560lbs the ratio of the difference remains the same, however with every doubling on the downforce [200-->400] there is doubling of the grip [280--->560]

Can you see that? As one doubles so does the other, the ratio of adherence remains at 1.4 / 1.5 but the grip doubles as the weight doubles.

These graphs were presented as proving that the grip lessens immediately from 1kg... they do not do this they clearly show what I have said all along, 'only after the tyre reaches its optimum adherence/weight limit will the tyre start to show diminishing returns for the weight applied.

This is the first post in here that makes some sense (to me) :)
 

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Mycroft said:
Thorin can you see what I mean?
The graph is in no way detailed enough to show that when load is doubled, grip is also doubled. I still maintain that at best it will still be very slightly less.
 

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Discussion Starter #164
Thorin said:
The graph is in no way detailed enough to show that when load is doubled, grip is also doubled. I still maintain that at best it will still be very slightly less.
Well it's a start.

''The graph is in no way detailed enough to show that when load is doubled, grip is also doubled.''

So on what evidence do you base this statement...

''I still maintain that at best it will still be very slightly less.''
 

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I've just logged on briefly, apologies this will be quick, and that I don't have time to answer questions here.

Mycroft

Please answer my questions put to you. It is up to you whether you do or not, but if you choose not to, I will simply withdraw from engaging you in conversation.

I am growing rapidly tired of this thread, and am certainly not spending all of this time on it to discuss such ridiculous logic with someone who does not answer the questions that he is challenged with, so would rather chanell all remaining time in to dealing with questions from genuine enthusiasts.

All

Apologies for the above, if you have any questions, please ask them and I'll answer them as best I can. If you'd rather I clear off, please tell me :D there will be no hard feelings, I'm only a mere subaru driver after all!!! :D

I think it's best that I (it's obviously up to you whether you do) ignore mycroft from this point on unless something miraculous happens, so please take it as read from now on that my opening line is "what mycroft has just posted is innacurate" :D

All the best

Simon
 

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***warning - serious question***

Simon

If I've followed the posting (on recent pages anyway) a key point of difference stated by Iain is that you believe that "weight of any kind is self defeating to some extent from 1kg onwards"

I didnt think you were saying "from 1kg onwards" necessarily - is that right?

just checking
 

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Discussion Starter #167
:D

You are sounding more like a defeated soul with every post my friend.

Let's face it, you have lost this one, the graphs you have presented have shot you in the back.

I am feeling less than jubilant about it.
 

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Hi Harry

Thank you for the question.

I have no interest in what happens at below 1kg, as I have never driven a car that weighs less than 4kg. :D

What I am saying is that on a real world car, doubling the load on a tyre, less than doubles the grip it produces. I really do not know (As it has never been of interest to, or of relevance to this thread) what happens at 1kg, so I can only give you useful information based on vehicle dynamics rather than "coat hangers and blocks of wood" experiments.

I can't take any credit for the following as it was given to me by Damian Harty (who I will try to temp to post) as a great way to think about the dynamics of tyres... but it was (paraphrased) as follows...

The grip produced by a tyre should not be though of a single object creating friction. Each tread block (remind me to talk about slicks if I forget) is a block of rubber providing friction individually. As the tyre skews, so do they, the load on each one is slightly different, the angle of attack of each one is slightly different, and they all produce slightly difference amounts of friction.

So when a tyre is nearing it's limit, it is not the overall tyre that is simply starting not to work as well, but a greater percentage of the tread blocks letting go.. this is why a tyre starts to make noise even before it actually lets go.

So... whilst friction is part of the story, it cannot be taken as the entire explanation of how a tyre produces grip.

All the best

Simon
 

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In essence to all of this...

You are all quite able to trust me on the following.

Mass, is a negative to performance of a car in that it reduces grip and requires more acceleration (whenever grip is not at it's limit).

The reason it reduces grip, is that tyres produce grip at a less than linear rate to the load placed on them. Meaning... Double the load and you less than double the grip.

As the extra mass still needs to be accelerated, the reduced relative grip provided by the tyres means that they cannot resist the forces of the mass to the same extent they could before it was doubled.

Whilst it is always going to be possible to engineer a heavy car to be more performant than a specific lighter car (the same as it would be possible to engineer a car with 200bhp to be faster than a specific car with 250BHP), the following will always be true.

Build two cars from scratch. One has to weight 1000Kg, and the other 2000Kg. You are allowed to spend 10 trillion dollars on each, and have the entire world of vehicle dynamics experts working on the project.

You will always be able to make the 1000Kg car go immeasurably faster round a circuit.

Regards

Simon
 

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Discussion Starter #171 (Edited)
''What I am saying is that on a real world car, doubling the load on a tyre''
>
A subtle change, but a pleasing one, we can nearly agree on that if we can assume that the car is well engineered and has been optimsed [In the manner I have shown] then what you are saying agrees with what I have been saying all along.

--------

''So... whilst friction is part of the story, it cannot be taken as the entire explanation of how a tyre produces grip.''
>
Absolutely right! and pleasingly backs up what I posted earlier about the co-eff not being the whole story.

-------

There is nothing that I can seriously disagree with in your second post, with that proviso in my first to this:- ''Meaning... Double the load and you less than double the grip.''

With that slightly half-hearted climb down Simon, we may be able to move on.

Good post.
 

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Mycroft said:
''What I am saying is that on a real world car, doubling the load on a tyre''
>
A subtle change, but a pleasing one, we can nearly agree on that if we can assume that the car is well engineered and has been optimsed [In the manner I have shown] then what you are saying agrees with what I have been saying all along.

--------

''So... whilst friction is part of the story, it cannot be taken as the entire explanation of how a tyre produces grip.''
>
Absolutely right! and pleasingly backs up what I posted earlier about the co-eff not being the whole story.

-------

There is nothing that I can seriously disagree with in your second post, with that proviso in my first to this:- ''Meaning... Double the load and you less than double the grip.''

With that slightly half-hearted climb down Simon, we may be able to move on.

Good post.
If anybody feels that Mycroft's last post even warrants a response, please let me know.

I do not have the energy to continue this futility for his benefit alone.

regards

Simon
 

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Discussion Starter #177
Do you really feel that rubbing Simons nose in it will do this thread any good?

Haven't you got a 'home' to run along to now little boy, I believe the MKIV kindergarten is back up. :D:D:D

You could stay and expound on what you think that 'point' may be, that would amuse for a while...:D
 

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Mark and All

If it's any consolation, this thread has become one of those "funnies" that people email each other, within the vehicle dynamics and motorsport fields.

These people have to deal with people of lesser understanding than themselves on a daily basis, but the comments are such that nobody has ever encountered anyone quite like our comedy companion.

The comments on the intelligent questions and reasoning from the general community are quite the oposite.

The good thing, is that we can all continue the discussion and just ignore him. That way, my colleagues will be able to continue their amusement (As he is unlikely to shut up) and we can continue to discuss a fun topic. :)

All the best

Simon
 
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