Sudden O/S riding inside kerbs, why?

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Reece
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Sudden O/S riding inside kerbs, why?

Post by Reece » Sat Oct 07, 2017 11:22 am

I was watching the f1 qualifying from Suzuka today and noticed the shunt Grosjean had in the S curves. It appeared that he lost the rear of the car when he rode on top of and along the inside kerb. They don't appear overly high, certainly designed to be used.

This had me wondering why and I began thinking about what would occur with the car to cause it because I imagine its quite an important trait of a f1 car at this circuit to be able to ride those kerbs to maximise performance.

Am I correct in thinking that the front inside wheels riding up onto the kerb slightly before the rear would cause the inside wheel to move into bump (after being in a rebound phase through the same corner prior to lifting up onto the kerb) which in turn causes the ARB to basically untwist and result in reduced stiffness in the front relative to the rear? This change in lateral load transfer distribution then leads to sudden O/S? Or is it more a damping issue with how quickly the suspension is able to react to the change?

I was also wondering what effect the kerb has on under body airflow and whether it can reduce flow underneath just enough to cause a loss in downforce and instability.

I've only had 2 beers I swear.

Cheers

Shrieker
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Joined: Mon Mar 01, 2010 10:41 pm
Location: Istanbul, TR

Re: Sudden O/S riding inside kerbs, why?

Post by Shrieker » Sat Oct 07, 2017 11:34 am

Reece wrote:
Sat Oct 07, 2017 11:22 am

I was also wondering what effect the kerb has on under body airflow and whether it can reduce flow underneath just enough to cause a loss in downforce and instability.

I've only had 2 beers I swear.

Cheers
Raise ride height and lose downforce. Am sober.
Education is that which allows a nation free, independent, reputable life, and function as a high society; or it condemns it to captivity and poverty.
-Atatürk

Reece
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Joined: Sun Apr 16, 2017 7:17 am

Re: Sudden O/S riding inside kerbs, why?

Post by Reece » Sat Oct 07, 2017 12:12 pm

Shrieker wrote:
Reece wrote:
Sat Oct 07, 2017 11:22 am

I was also wondering what effect the kerb has on under body airflow and whether it can reduce flow underneath just enough to cause a loss in downforce and instability.

I've only had 2 beers I swear.

Cheers
Raise ride height and lose downforce. Am sober.
There isn't an initial reduction when the spring compresses as it rides up the kerb? Does the outside of the front wing and floor also get very close to the ground which can burst vortices?

Shrieker
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Joined: Mon Mar 01, 2010 10:41 pm
Location: Istanbul, TR

Re: Sudden O/S riding inside kerbs, why?

Post by Shrieker » Sat Oct 07, 2017 12:28 pm

I understand some of those words.
Education is that which allows a nation free, independent, reputable life, and function as a high society; or it condemns it to captivity and poverty.
-Atatürk

wesley123
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Joined: Sat Feb 23, 2008 4:55 pm

Re: Sudden O/S riding inside kerbs, why?

Post by wesley123 » Sat Oct 07, 2017 12:32 pm

He crashed because he hit the grass. He had a slight bit of oversteer entering the esses, possibly because of the oil, where he ran wide onto the grass. It then becomes very easy to slide and lose the rear end.
"Bite my shiny metal ass" - Bender

Reece
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Joined: Sun Apr 16, 2017 7:17 am

Re: Sudden O/S riding inside kerbs, why?

Post by Reece » Sat Oct 07, 2017 1:38 pm

That could be the case yes. I do still wonder about the dynamics of it all with this characteristic in general though, not necessarily this particular instance. I often hear drivers and engineers discuss the ability or inability to ride along inside kerbs.