wet handling problems

[greenfingers964]

any ideas please for wet handling woes?

944 s2 track day car, leda coil overs, lightened, re-bushed with fresh geo check. etc. great in the dry but when it rained buckets at Bedford a couple of week ago, it was dreadful. the engine braking locked the rear end in change down to third and worse in second gear. (not brake lock ups). I don't heal & toe which i know would help.
it was dramatically badly behaved!!

a little more detail on the car. It is set to 10 clicks of 23 on soft, 250lb springs on front. car is set low, m030 anti rolls.

 

[Flick]

H&T would certainly help, a friend of mine had a TVR SEAC that would spit you off the road if he didn't H&T but to be fair the chassis couldn't cope with it's monstrous engine.

What tyres are you using?

 

[Neil Haughey]

You can make the back end of these cars dance around in the dry if you don't heel and toe let alone in the wet. I know some ppl don't heel and toe but tbh I believe the only way they could get away with it is to ease the clutch back in latter i.e. coasting

When you say re-bush has that included the gearbox mount and the mounts for the torsion bar carrier tube? If the bushes on the torsion bar tube are worn it can make the back end pretty wayward.

Once all of the above have been covered I would be looking at your rear damper settings, it sounds like your rear dampers are single adjust? If so they could be too stiff on the back, remembering that the ideal dry setting will be pretty stiff as its matched to the maximum dry grip of the tyres on the surface in question. I would soften up your dampers and maybe take one setting of the rear ARB if your still getting problems. I assume you have coil overs or much thicker torsion bars on the back to match the front 250 lb front springs and shocks. What are your rear spring rates and torsion bars and more importantly what are they relative to the dampers as supplied from new i.e. is it all a matched set with suitable damper valving for the spring rates. As an example with standard rear S2 torsion bars one would need a rear coilover spring of roughly 150 lb/inch to match a 250 lb/inch front spring.

 

[944 man]

Continuing what Neil has said above: have you tried to deal with a lack of front grip stiffening up the rear? This is common (and always suggested on internet forums, and befiore that in pubs by 'in-the-know' sorts but its bollocks) but it is always a mistake. When you have a lack of grip at the front you need to find grip there, as opposed to making the rear loose to in order to 'balance it out'. If this is how the car has been set up then the overly stiff / high rear will be a liability in the wet.

 

[Neil Haughey]

The example you give of understeer, and I understand that as corner entry understeer as this is common on our cars, is to increase the castor, increase the toe out and lower the front of the car a touch. However you are right ppl see a car that doesn't want to turn into a corner the way they want and go about stiffening up the back of the car loads. The result is something that will oversteer disastrously mid corner if you push hard enough and will be a nightmare to drive in the wet.

I would recommend anyone to buy the book 'Competition Car Suspension' by Allan Staniforth and published by Haynes, its a superb book that I have read through 3 or 4 times now.

I bet the case in hand here though is just a couple or 2 of simple problems. Tyres as said can make a massive difference as these cars can be awful in the wet on the wrong tyres with too much pressure in them, the Hankook RS'2's I have on the 968 being a good example, useless in the wet. As much as I hate the Toyo T1-R I have to say they work really well on our cars in the wet.

 

[edh]

Can't add much more than Neil & Simon - maybe you can get away without some of the gear changes as the car has a fairly wide power band? It doesn't sound like the car is very stiff - I'm assuming it has standard torsion bars?

I do think H&T is important though - and I find the 944 well set up for it when you brake hard on a track. You might find that solves most of your problems.

I try to cope with initial understeer with a bit of trail braking - until you start to feel the rear end come round a bit. Although that's more on dry track days, where I'm a bit more brave []

 

[944 man]

My example was more general Neil, rather than being 944-specific.

Ive got a couple of AS books (Race & Rally Car Sourcebook was a disappointment though): did you know that he died the other day?

 

[greenfingers964]

many thanks there's some great stuff here. to add a little more detail to narrow down the issue the torsion bars at the rear are standard s2 so the ledas may not be best matched now I have upgraded most other areas?
haven't re-bushed the gearbox mounts so this is a good route to follow.
I tend to keep the rear quite soft though.

With all this in mind, most issues happen in a straight line! ie axel locking with engine braking on change down. old tyres must be a contributing factor?

I was interested in the hankook rs2 wet wether performance as these were my choice for a new set - NOT now though!
Khumo track day tyres anone - they seem good value as I hate paying inflated 888 prices.

On the Alan Staniforth loss yes he passed away earlier this year and was a bit of a guru and big loss. Designer of the terrapin racer and writer of many books. need to aquire a copy.

I really thought i had gone through every aspect of the running gear but have question marks particularly matching springing and damping.
I 'll have to hope the 'ring stays dry next year!

 

[Peter Empson]

What tyres are you running? Have you done wet trackdays without problems before and if so have you made any changes since?

I always rev match on down shifts, it's really very easy with a little practice and so much kinder on the car. A few years ago I messed one up going into Copse, that locked the rear up and gave me a bit of a moment! As Neil says, the other option is to drag the clutch in slowly. To be honest I'd expect any RWD car to do this, there simply can't be enough grip in the wet to let the rear tyres do the braking for you.

My car is probably fairly similar to yours (just stiffer spring rates) and if you saw the video of my last wet trackday you'll see I had an 'exciting' time, but I never once felt like the car had it in for me, all my moments were down to my own ham fistedness [].

<Edited to add> Please ignore the question about the tyres, we must have cross posted

 

[greenfingers964]

thanks Peter - looks like you have lots of experience in wet - perhaps my expectations are too high for wet driving but the it was almost a joke slowing down even de-clutching gently so i think there is an issue.
But just picking up the tyre aspect, if you were buying a new set of track day tyres that were good if it rained ? not 888s as I don't like the 'new ' inflated prices.

ps super charger project looks interesting - will follow this one!

 

[Peter Empson]

I have very little experience in the wet, I've probably only done about 10 really wet trackdays over the 10 years or so I've been doing them, but getting tuition this last time out was such a tremendous benefit. The 888's are an awful wet weather tyre as you'd probably guessed, I've always found the Toyo T-1R to be a very good compromise (this is on 17" wheels, I'm wary of recommending them for 16" ones based on reports from others), but I'm sure any of the high performance road tyres should be pretty good.

 

[greenfingers964]

thanks Peter - will consider the toyo tr1/r.

 

[944 man]

Do you still have a glass rear hatch, and have you corner weighted the car? I took that much out of the rear of my track car that it weighed next to nothing. This made it extremely skittish and it was almost impossible to drive in the snow (I still drove past every BMW that I saw though!), going sideways whenever I touched the accelerator...

 

[Neil Haughey]

ORIGINAL: greenfingers964

many thanks there's some great stuff here. to add a little more detail to narrow down the issue the torsion bars at the rear are standard s2 so the ledas may not be best matched now I have upgraded most other areas?
haven't re-bushed the gearbox mounts so this is a good route to follow.
I tend to keep the rear quite soft though.

I was interested in the hankook rs2 wet wether performance as these were my choice for a new set - NOT now though!
Khumo track day tyres anone - they seem good value as I hate paying inflated 888 prices.

On the Alan Staniforth loss yes he passed away earlier this year and was a bit of a guru and big loss. Designer of the terrapin racer and writer of many books. need to aquire a copy.

I really thought i had gone through every aspect of the running gear but have question marks particularly matching springing and damping.

Yes 250 lb/inch on the front is way too hard to match the stock rear 140 lb/inch or so torsion bars. I bet what you are finding is the dampers on the back match the dynamics of the front of the car but alas are far too stiff for the rear torsion bars. In the dry you can get away with a fairly lively back end but not in the wet. Frankly with 250 lb springs on the front you would end up with the fronts then being far too soft for the front springs if you soften all 4 shocks up enough. You probably need full soft on the rears. As an example the cars as standard have very very soft compression on the rear, I reckon the rebound is several times the bump setting and you can easily compress a standard S2 rear shock in your hands. If strong enough you can even pump it in pretty quickly, it may shock some ppl pardon the pun but the rear dampers for my mums polo felt like they had as stiff if not stiffer compression. Standard front shocks have much much harder compression in comparison, I can only push one in by leaning very hard on it and then it moves slowly.

Quick question to confirm my analysis above, do you get predominantly a lot of understeer in the corners? if the answer is no then the only thing that is holding back the understeer is excessive damping. My S2 for example used to understeer like a pig on 190 lb/inch front lowering springs and stock rear torsion bars. OK it had less body roll but it cornered slower then a standard car.

The Hankooks work OK of you can get them hot enough and therein lies the rub as I found in the wet you just can't work enough heat in them. The one good thing is they have a really solid construction and the car feels like its on rails. They don't really have any more grip then standard road tyres though which is a major killer.

Real shame about AS I had no idea he had passed away, he will be remembered for a long time though.

 

[greenfingers964]

This is fantastic detail and throws up many possibilities.
In answer to your questions I would say it does understeer a bit but not excessively. (I am coming out of 911s so the S2 feels great on turn in!) I do keep it soft at the rear as it feels easier to drive due to my relative inexperience.
, To recap the spec, all areas of my suspension are upgraded, ledas coilovers with 250il front springs, 968 m030 arb, long pin A arms, poly bush, lowered rear, 968 castor mounts. The unknown is spring rates on rear coilovers.

with all this in mind i have most of 'right' bits. would you upgrade the torsion bars to 968 and either check or replace the coilover springs? what springs rates would you go for if you had my car. It is NOT a road car and quite extreme!

any other views on getting the right set up and spec?

Couple of other things - whats the spec of your s2 race car as I am looking for tips! do you have perspex & plastic windows.

again thanks for great detail
Phil

 

[Neil Haughey]

Hi Phil glasswork in my car is standard to meet the rules, the biggest differences between a race car and a track modified car are the extensive use of fibreglass and the body shell prep, although you don't have to do either. The best ppl to talk to by a long way are EMC in Birmingham.

I seem to have misunderstood your spec though. I thought you had plain dampers on the back with standard torsion bars. If you have coilovers on the back then that changes things somewhat, it would be good to know what the rate of those springs is though. Personally I wouldn't bother upgrading torsion bars when you can just put different springs on the coilovers.

None of us would claim a limo smooth ride but does your car feel skittish on the road? My S2 used to have 190 to 220 lb rising rate front springs and 225 lb/inch torsion bars and was fine to drive pretty much anywhere, it was completely flat on the bumpiest b roads. I didn't find it any less comfortable then my bone stock 968 for example.

How fresh are your coilovers? Is this a kit you bought secondhand perhaps or is it a new set from Leda? If they are old they may just need a rebuild and re-valve by GAZ.

Lastly how much camber are you running on the back end? Loads of camber could exasperate any problems back there, generally would use less camber in the wet then what is ideal in the dry which is why I am often surprised that some ppl run a lot of camber on the back of these cars. Its not something I think one can adjust quickly like if it start to rain before a race.

 

[greenfingers964]

more great food for thought!
camber is 1 degree all round so quite sensible and the ride of the car is quite soft too.
Its strange really as it rides large bumps well on the road but is very harsh on cats eyes and similar 'sharp' bumps!
For what I consider a dedicated track car it rides ok on the road generally.

The leda's condition seems ok and i will look at a rebuild in the future - or a move to gaz/kw but intend to get some value for now.

(looks like i need to pin down the coil over spring rates)

assuming these springs are sensible balanced rates, then I need to have a track day and experiment with damper settings rather than thrashing round blindly!! thanks again for you advice regards - ~Phil

 

[944 man]

Get the Ledas rebuilt by GAZ.

 

[edh]

ORIGINAL: 944 man

Get the Ledas rebuilt by GAZ.

+1 - cost me £90 for my rears earlier this year (single adjustable Leda, non-coilover)

 

[944 man]

I understand that a knowledgeable man, and all round top fellow; steered you in the right direction there? []