High speed stability

[Jazzleman1]

i got a phone call the other day and thought that i had better put this to the board.

A colleague was out in a fabia II vrs and travelling at high speed on a test track. apparently, as he approached a sweeping left hander, he got the impression that he had experienced a blow out or similar. the car drifted quite violently to the right, he said it was stable in so much that he could see exactly where he was about to hit the crash barrier. he managed to gather it all in and once his pulse had almost returned to normal he gave me a call.

He checked the tyres and found no visual defects etc, and when he checked the tyre pressures, he noticed that the front offside was 3 psi lower than the rest.

He wondered if i had experienced anything similar. I was unable to answer him as i had literally done 938 miles in it, to run it in, before entrusting him with the keys. I have not been able to get near it since.

So, my questions are -

Are these cars known to be unstable at the upper end of the speed range?

Are they known to be sensitive to relatively small differences in PSI?

Are they sensitive to cross winds

Does anyone have suggestions?

The car is completely stock with about 1500 miles on it, and it was on a dry day. The driver is very competent and experienced.

Would love to hear your comments and/or experiences.

Thanks

[P1TT8ULL]

I wouldn't say its unstable at high speed atall. Yea I'm sure many will say its crap compared to other cars but as a whole its fine. I've been through sweeping bends over 100mph and its felt fine even with the weights taken out no spare Tyre and a low amount of tread on the rears.

3 psi is very minimal unless your talking the very last tenths of a second on track.

Possibly the xds cutting in and playing up??

Edited 28 April, 2012 by P1TT8ULL

[Confide]

Aslong as it's not windy it won't be unstable... But at around 150 mph, it gets abit scary. I defo want more downforce on the drar!

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[jonny boy]

Aslong as it's not windy it won't be unstable... But at around 150 mph, it gets abit scary. I defo want more downforce on the drar!

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150 ? In a Fabia ?

[Jazzleman1]

Thanks for the replies. Will discuss it with him on Monday when in back in the office. I was surprised when he rang me. I thought about whether he might have hit some oil or something on the approach to a bend which unsettled the car. The fact he said it was predictable as it was under steering towards the barrier may be the ESP doing its 'magic.'

Cheers.

[Confide]

150 ? In a Fabia ?

Yeah, software + exhaust helped alot .

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[Ootohere]

The OP says "on a Test Track",

Does this mean a Vehicle Test Track or was it on a Race Track?

*I would think you would ask the question of the Professionals/Employees at the track to get some answer thats worth listening to.

ie How do other vehicles handle in that situation?

If he is an Experienced driver, does he not have experience of tyre pressures,

or what is it he is experienced in, is it BS?

The reason i say this is, a Car/Vehicle test track might well have a hump or off camber high speed corner designed to unweight vehicles & show any or exagerate handling problems.

Race tracks may also, and are often more pronounced when doing in the opposite direction to the Race direction.

I know a couple of Race Tracks that are very different from their usual when being used in reverse for car testing..

??so basically, can i ask where this car was being tested, or was it being Track Day'd?

Just being nosey, but what is the back story,

whos almost new car, is it yours & who is this driver or why is he tanking it around 'a testt track' ?

If he is a tester, does he not check things like tyres pressures before high speed testing?

george

Edited 29 April, 2012 by sk4gw

[vRSy]

Mines stable at speed if the road is smooth. Add any bumps and undulations and the car wanders and moves around alot.

[Reavenger]

Mines stable at speed if the road is smooth. Add any bumps and undulations and the car wanders and moves around alot.

Was same for me. Cornering at speed will make you nervous too as there is a lot of body roll. Had some good side ways action on greasy track especially at Combe last year too.

You'll get a fair bit of road or track noise at 80mph+ as well. Especially if the upper door seals aren't perfect (mine weren't).

But I never completely lost it in the Fabia. Not the sort of car that just goes away suddenly.

Edited 29 April, 2012 by Reavenger

[Ad Lav]

If a strong side/cross wind catches it, this could make it unstable.

[jonny boy]

If a strong side/cross wind catches it, this could make it unstable.

You need roof fins !

[Can]

The MK2 VRS in my opinion is very susceptible to small variations in tyre pressure especially at the front.

I think it's due to the small is tyre size/profile and the setup of the car from the factory.

[Ad Lav]

Johnny - they could suit my car maybe I'll look into some

[32KOFDATA]

When there are strong cross winds I have experienced unstable reactions from the car. Not to the point of losing control but it does scare you a bit as you have to correct with your wheel. I've also experienced the effect when passing by lorries or big trucks. Nothing though to the extend of what your friend had at the race track so it seems a bit of mystery to me what really happened.

[Confide]

Reason to instability : high center of gravity, low weight and short wheelbase.

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[Jazzleman1]

Thank you all for your replies. It is much appreciated.

[vRSy]

Reason to instability : high center of gravity, low weight and short wheelbase.

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Poor damping is a much bigger cause IMO. As said before i have no instability on a smooth road, add in undulations and its rocking all over the shop

[Confide]

Poor damping is a much bigger cause IMO. As said before i have no instability on a smooth road, add in undulations and its rocking all over the shop

If you have no stability-issues on a smooth road then you haven't driven fast enough, it get's quite scary past 150.

Compared to my old car which was driveable with one hand, this is ALOT more twitchy.

I'll try it out with the new dampers / springs and see how it reacts with this, but I'm pretty sure it will just have helped a little.

It's obvious that it will be bouncing all over the road when it's bumpy however...

[P1TT8ULL]

Coilovers make a HUGEEEE difference

[jonny boy]

If you have no stability-issues on a smooth road then you haven't driven fast enough

Obviously you've not seen his in car videos

[Confide]

Obviously you've not seen his in car videos

I've seen them... not fast enough xD!

[Wilko251088]

How fast is fast enough? Falling off the road fast?

[Confide]

Passing 200 km/h and it's starting to get jiggy with it, passing 250 and you need ALOT off space.

Disclaimer : do not test those speeds out on the freeway, do it on an airfield / racetrack!!

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[harryweld]

Going back to an old 5th gear they ran a VRS flat out round a test track until it did a tyre in and there was crosswinds there. So should be no stabliety problems.

Not sure if it had roof fins or not though :think:

[jonny boy]

Going back to an old 5th gear they ran a VRS flat out round a test track until it did a tyre in and there was crosswinds there. So should be no stabliety problems.

Not sure if it had roof fins or not though :think:

That was the Mk1 which was famed for it's handling

Definitely had no roof fins. They're for the select few