Question for handling experts

[ukkid35]

http://vimeo.com/158817288

Why does the rear break away at 2:15? Tyres are up to temp, only done 3 laps, so they can't have gone off yet. I change in to 4th at 00:11, whereas I kept in in 3rd on the next lap, but surely it should be more stable than that?

Car is running AD08 at 22/24 cold and Protech single adjustable. Any thoughts?

[Tanguero]

Hard to be sure but it looks like there is a slight dip in the surface just after the apex. Would the combination of that making the car go light as you were feeding on power explain it?

[ukkid35]

Thanks, there is a dip there, but I had plenty of PAX laps in cars that were much quicker than me, and none of them had issues. It left me feeling very uncertain about the car, as it really didn't feel as if it should have broken away.

Edited by ukkid35 on Sunday 13th March 17:26

[Mark_S_24]

Just some thoughts

The cars you PAX lapped in, were they all RWD? Were they as light as the TVR, do they have as much torque?

If you were in a different gear the car would be at different revs & there for a different place on the torque curve.
(Not sure of the technical details, but that could be a reason?)

Mark

[ukkid35]

Mark_S_24 said:

Just some thoughts

The cars you PAX lapped in, were they all RWD? Were they as light as the TVR, do they have as much torque?

If you were in a different gear the car would be at different revs & there for a different place on the torque curve.
(Not sure of the technical details, but that could be a reason?)

Mark

One of the cars I rode in was a Series 3 Exige S, which has very similar performance on paper, but is in a different league handling wise (vs my car at least). Needless to say I was letting him past when we were on track at the same time.

[gruffalo]

ukkid35 said:

http://vimeo.com/158817288

Why does the rear break away at 2:15? Tyres are up to temp, only done 3 laps, so they can't have gone off yet. I change in to 4th at 00:11, whereas I kept in in 3rd on the next lap, but surely it should be more stable than that?

Car is running AD08 at 22/24 cold and Protech single adjustable. Any thoughts?

I run mine at 18/18 cold for a track day.

I found out about this at a day where some techs from Michelin were offering advice, they kept playing with tyre pressures then sent me out for a few laps and then checked the tyre wear pattern and case temps as well as tread temps.

The interesting thing was that the tyres were showing about 30PSI hot with the cold pressure set at 18/18 or 22/24, the difference was that the whole tyre was warming up more with the lower cold pressure making the tyre more sticky without over heating the tread and ending up with the higher pressure increase with the added heat.

[ukkid35]

gruffalo said:

The interesting thing was that the tyres were showing about 30PSI hot with the cold pressure set at 18/18 or 22/24

That certainly matches my experience, as they were 31/29 hot when I checked. I will follow your advice next time - many thanks.

[JezF]

ukkid35 said:

One of the cars I rode in was a Series 3 Exige S, which has very similar performance on paper, but is in a different league handling wise (vs my car at least). Needless to say I was letting him past when we were on track at the same time.

I'm afraid a S3 Exige is likely to be in a different league handling wise.

[ukkid35]

JezF said:

I'm afraid a S3 Exige is likely to be in a different league handling wise.

I completely accept that, but I don't accept that it was reasonable for the rear to break away in benign conditions with decent tyres, as it does. So I'm trying to understand what I need to do to fix that. Is is simply a case of throwing money at the car by fitting Nitrons, Intrax or perhaps Ohlins; or could a simple setup change fix it?

[Jhonno]

What are your geo settings Paul?

[phazed]

As said previously, it seems the car went, "light" and you lost a little grip for a split second.

I wouldn't worry unduly, just be aware that these things happen.

Would different dampers improve on that situation, most probably.

My experience with Pro-Tech single adjustable is that they are fine for the road but as laps pile on they overheat and severely loose their damping ability. They are a twin tube damper and not a mono tube like the better dampers.

I had this to the point that after 20 mins on track they had no damping ability at all! I experimented with Nitron 46mm Pros but as good as they were on track they were lousy on the road.

My Monos suit the car well with a 450/400 spring setup, (chim).

[Mr Cerbera]

Also don't forget that Donington is a dumping ground for fuel from the aircraft using East Midlands airport

[thebraketester]

What was it like on subsequent laps?

[ukkid35]

thebraketester said:

What was it like on subsequent laps?

That was my penultimate session, and since I'd already spun once at the beginning of the day http://vimeo.com/158797927 I didn't feel like pressing the issue on subsequent laps.

On the final session I was with a coach who was showing how much room for improvement there was with my lines, so I wasn't pushing as hard at all.

[JezF]

ukkid35 said:

I completely accept that, but I don't accept that it was reasonable for the rear to break away in benign conditions with decent tyres, as it does. So I'm trying to understand what I need to do to fix that. Is is simply a case of throwing money at the car by fitting Nitrons, Intrax or perhaps Ohlins; or could a simple setup change fix it?

Firstly I'd make sure your geo and bushes are all good.

I love Nitrons and that's what I have fitted to my Cerb. I've had four Elise's and have driven a S2 Exige S. They all cope with road imperfections and lumps and bumps brilliantly and having driven an Exige S cross country in Wales, they stick to a road like you wouldn't believe so they are always going to cope with undulations better than a Cerb. I love my Cerb but it's very different and imho not as good in the handling department.

[ukkid35]

JezF said:

Firstly I'd make sure your geo and bushes are all good.

I replaced the front bushes last summer, it transformed the car. I admit I have yet to replace rear bushes, that is next on my list.

Springs and Geo settings are all standard.

[billynobrakes]

ukkid35 said:

That was my penultimate session, and since I'd already spun once at the beginning of the day http://vimeo.com/158797927 I didn't feel like pressing the issue on subsequent laps.

On the final session I was with a coach who was showing how much room for improvement there was with my lines, so I wasn't pushing as hard at all.

Watching that video and you can correct me if you had come in to the pits and went straight out but I always do a warm up lap to get tyres / brakes up to temperature and looking at that you come straight out the pits let other cars go by so tyres will not be getting warm then you floor it so it could simply mean tyres was cold and just let go as they was not sticky enough, its the same with brakes you need to warm them as well, that's IMHO

[thebraketester]

That looks to break away far too easily with no real warning. :-S

[JezF]

ukkid35 said:

I replaced the front bushes last summer, it transformed the car. I admit I have yet to replace rear bushes, that is next on my list.

Springs and Geo settings are all standard.

I imagine Nitrons would make a fair difference, as they were already fitted I can't tell you how much difference though.

[Gazzab]

I have nitrons and handling set up by someone very good. Was overtaking a slow car on an incline with a patchy and undulating (?) road surface a couple of days ago..the car decided to try and go sideways. Whilst on one hand I would blame the road surface and tyres...ultimately a Cerbera's chassis is a little crude and will bite you in the ass when in a scenario that goes beyond its capability.