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Tire slip angle diagram, wet vs. dry


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#1 giskard

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Posted 19 June 2012 - 03:29

Hi all,

Does someone have a link to a tire slip angle diagram, so I can see how it changes from dry to wet?
I want to understand why tires behave the way they do in the wet (e.g., cornering force past the peak at very high slip angles, is a larger % down from the peak, in the wet vs. dry, or the dropoff is more abrupt).

Cheers.

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#2 TC3000

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Posted 19 June 2012 - 20:10

not many "takers" for your question so far.
Perhaps it helps, if you explain a bit better what you would like to know, and if you wanna talk about
a race car or a road car.
I doubt, that someone will/can post some "real data" on here for racing tyres. You will at best get some
generic data such as this one, to explain the principles/general trend.

If you want to talk specifically about racing tyres ( F1, LMP etc.), you have to keep in mind, that you talk
about two complete different tyres to start with. Not only in terms of slick vs. profil/grooved tyre, but also
in terms of compound and possible internal construction of the tyre, as well as inflation pressures etc.

For a road car tyre, the situation is different, and a comparison/conclusion probably easier, comparing
wet vs. dry road performance.

Not sure, if this is what you where looking for, but at least it's a start :) (but it's from an aircraft tyre)

Posted Image

maybe this is worth a quick look/read

Edited by TC3000, 19 June 2012 - 20:41.


#3 TC3000

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Posted 19 June 2012 - 20:47

Posted Image

#4 giskard

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Posted 20 June 2012 - 03:18

Thanks.
I was curious about street tires.

Basically I want to understand why a car behaves like this in the wet:
http://www.youtube.c...player_embedded

The diagram in your first post doesn't make sense wrt what I think it should be.
Upper left hand diagram in 2nd post does:
- wet grip peaks early then drops

Have you seen any more diagrams? The tire book by Haney is good but doesn't show any comparison of wet vs dry for a hi perf street tire.

The paper you linked was pretty interesting BTW.


#5 Greg Locock

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Posted 20 June 2012 - 04:51

The diagram in your first post doesn't make sense wrt what I think it should be.
Upper left hand diagram in 2nd post does:
- wet grip peaks early then drops

And there I was thinking how well they agreed

#6 giskard

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Posted 20 June 2012 - 14:48

And there I was thinking how well they agreed


So do you agree or disagree that they agree? :)

#7 TC3000

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Posted 20 June 2012 - 18:03

- wet grip peaks early then drops


But it does so too, in the first diagram - No?
The main difference is, IMO, that the second diagram, does not show the slip angle range past peak value for the dry road.

Anyways, it's a complex matter, and I'm not the expert for it.
There are many factors coming into play here, and all of them have a effect on the final outcome.
Not sure, how deep you want/need to dive into the subject, but you may find some "food for thought"

Here CAUTION !!! it's an 850 page pdf file, so may take a while to load

and

here

good luck

#8 giskard

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Posted 21 June 2012 - 15:58

But it does so too, in the first diagram - No?
The main difference is, IMO, that the second diagram, does not show the slip angle range past peak value for the dry road.

Anyways, it's a complex matter, and I'm not the expert for it.
There are many factors coming into play here, and all of them have a effect on the final outcome.
Not sure, how deep you want/need to dive into the subject, but you may find some "food for thought"

Here CAUTION !!! it's an 850 page pdf file, so may take a while to load

and

here

good luck


Thanks. I looked at all the diagrams and didn't see a slip angle diagram showing wet vs dry.

#9 TC3000

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Posted 21 June 2012 - 18:20

o.k. apologize, I thought that you had a deeper interest in the topic, and where not just looking for some graphs.
I somehow, doubt, that you will get your answer from looking at some slip angle diagram.

if you are still interested you will find some graphs in this & this pdf file, and in book preview

some "real test data" can be found here, may need to plot/fit your own curves.

anyhow, seeing that you have ask the same question on different BB's over the last years, it seems, that you still have not found what you where looking for.

If you want to understand the car behavior, then you need to look at more then just a two dimensional curve, where other important parameters such as tire construction, profile pattern, groove depth, inflation pressure, sliding velocity, vertical load etc. etc. are held constant.
It's a multidimensional problem, a single graph/diagram will not give all the answers - IMHO

If you want to know, how it relates to driver feedback, then you may want to/need to include things like Self Alignment Torque and Pneumatic Trail into your considerations, as well as steering system design,stiffness & geometry, and parameters like caster and KPI/SAI etc. etc. the list goes on.

Edited by TC3000, 21 June 2012 - 19:01.


#10 Greg Locock

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Posted 21 June 2012 - 23:04

The Milliken Moment Method plot is a nice way of looking at a tire. I don't remember seeing an MMM for a wet tire. Thanks for all the refs, there's a lot in there. I like the data one, as you can imagine the files off a modern tire rig look much like that.