Stabilising rear end a bit

[Wild E. Coyote]

Hi all,

You all probably know that our cats like to go wide with their rear ends in curves. While I like it and don't mind it actually, had a situation in which alomst got hit because of it. We have few roads that are smooth almost like glass and on one I entered a curve slightly fast(ish) and when added some steering angle close to the apex point the rear end stepped out quite a lot. I corrected it without a problem, but the car from another direction almost hit me since my rear end stepped in his lane! I mean, puma has more grip on front than rear; unlike almost all other FWD cars!
Now, my question would be aimed especially at you guys going to do the puma cup or regular track addicts. How did you set up your rear suspension? Is your car still tail (to)happy?
To answer in advance: front springs and shocks (KYB excell G) are new, rear shocks are new (again KYB), rear bushes are new, droplinks in front are new (the adjustable ones) and tyres are stock dimension on props, new goodyear efficient grip performance.
I was thinking adding some camber to the rear tyres, not to much, about -2 degress similar to the front using this http://www.ebay.co.uk/itm/270613723415?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649" onclick="window.open(this.href);return false;
IMHO that should stabilise rear end somewhat, don't you think? Or do you have any other idea?

Thanks in advance,

 

[Sjoerd]

I adjust my suspension according to my needs; on track I like a bit tail happiness when entering the corner. For the street definately not. I did still find it twitchy on the 'Ring (high speeds) so I made some designs and added a tiny Gurney flap. Works a treat. It's just the right size for disturbing the airflow and increasing downforce, without increasing drag too much. It's been on for about 2 years now, never regretted it.

What toe-settings are you running on the rear?

Before and after:

 

[Wild E. Coyote]

I am running stock geometry at the moment. Hence why I am thinking of adding some slight camber to match the front which is at -2 degrees IIRC.. Negatice camber should in theory offer better stability

 

[Wild E. Coyote]

Anyone has any experience with setting rear suspension to negative camber as per first post?

Thanks,

 

[quest63]

Wouls axle spacers not help?

 

[Sjoerd]

Depends on the exact geometry. Is the Puma rear axle set to negative camber as standard? Offcourse widening would give it extra camber in this case. Might cause uneven wear of your tyres (which is an MOT fail over here) though if you overdo it.

 

[Wild E. Coyote]

Puma is standard at 1 degree negative camber at rear. I am not thinking going mad like those lunatics for show that put crazy cambers at rear in excess of 15 degrees; just a tad more. Say 2, 2.5 max. I guess focus uses something like that, possibly even more at rear axle as standard….
That is why I wanted to consult with someone who is regular at tracks to ask for his experiences

 

[Sjoerd]

Puma is standard at 1 degree negative camber at rear. I am not thinking going mad like those lunatics for show that put crazy cambers at rear in excess of 15 degrees; just a tad more. Say 2, 2.5 max. I guess focus uses something like that, possibly even more at rear axle as standard….
That is why I wanted to consult with someone who is regular at tracks to ask for his experiences

I am and with the above mentioned things (spring/damper setting + gurney flap) the Puma is more than stable enough for me. Just on Döttinger Höhe at the 'Ring it feels a bit light, but you can predict that.. At the other tracks (Zolder, Zandvoort, Assen, Lelystad, Papenburg) the car felt quite stable. My in-depth simulation/calculation of the suspension is in the works, if you can wait..

 

[Wild E. Coyote]

Of course I am waiting… I am using stock components. The car isn't lowered as I didn't feel like it. Firstly, we have snow during winter and lower the car, more problems you have on snowy roads.
And secondly, our roads are very bad and bumpy; in those circumstances the softer and higher is better and faster!
I think the bushes might be the (or a) part of the problem. When I am in the corner, the car has leaned on the suspension and then if I add some steering angle the rear end steps out adn have to countersteer it to correct it and collect it. Perhaps adding some pressure to rear tyres, but not to much?

 

[Sjoerd]

Of course I am waiting… I am using stock components. The car isn't lowered as I didn't feel like it. Firstly, we have snow during winter and lower the car, more problems you have on snowy roads.
And secondly, our roads are very bad and bumpy; in those circumstances the softer and higher is better and faster!
I think the bushes might be the (or a) part of the problem. When I am in the corner, the car has leaned on the suspension and then if I add some steering angle the rear end steps out adn have to countersteer it to correct it and collect it. Perhaps adding some pressure to rear tyres, but not to much?

To be honest I'd get good coilovers then. My set of AVO's is adjustable and can be just as soft as the standard when set right. On track it can be extremely hard. Offcourse height is adjustable too. Mine is raised +/- 10 cm's again in the winter as I use it on the street too some days. Being that low means it needs to be set harder, in which it can be quite jumpy (in rain).

On the street tyres I run mostly on 2.4 bars, on my semi-slicks I sometimes go as low as 1.7/1.8 bars. Usually front slightlly harder (rears need longer to warm up otherwise).

 

[PumaJay]

I found my puma became a lot more stable when it was on 17" wheels, the bigger more square edged tyres made a big improvement to rear end grip... but seeing as I like a bit of over steer I went back to 15's, more comfort and much better for the track.

 

[quest63]

Throw a dead politician in the boot that should fix it :thumbs: