Modified 944's
- Thread starter rickware
- Start date
Let's say on your road tyres you can generate 0.5g through a corner then what happens to limit you to that 0.5g? Your tyres lose adhesion; it is as simple as that. On your warm, sticky and stiff sidewalled slicks you might generate 0.85g through the same corner, so everything is subjected to an extra 0.35g.
That is so obvious to me that I really wonder if I am missing the point, but if I am then I can't for the life of me see where.
That is so obvious to me that I really wonder if I am missing the point, but if I am then I can't for the life of me see where.
AndrewS
Member
Hi Simon,
I have been running slicks on a standard road going 944 Turbo for the last 10 years and have done over 60 track days in that time.
I see plenty of other Porsche cars being used on slick tyres (or road homologated track tyres) with no ill effects.
The stresses on the bodyshell are not significantly increased as the cars are invariably running on standard (or mildly modified) suspension which ultimately limits the cornering abilty becuase of roll and reduced tyre contact with the road.
For example: At Castle Combe slick tyres are worth nearly 10 secs a lap (in my current 944 Turbo) and over 20 secs at Silverstone GP. However, my previous Porsche Cup 944 chassis would have been another 4 to 10 seconds a lap quicker still. All Cup cars had standard body shells (seam welding was not allowed within the regulations) and ran on slick tyres (2000, 2001). I don't recall any Porsche Cup race cars having chassis integrity or flex issues as a result of racing on full race suspension and slick tyres.
Regards,
Andrew
ORIGINAL: AndrewS
...........[FONT=arial"] I don't recall any Porsche Cup race cars having chassis integrity or flex issues as a result of racing on full race suspension and slick tyres.![[FONT=verdana,geneva"]](/forum/styles/default/pcgb/space.gif ". [FONT=verdana,geneva\"]")
Hi Andrew,
Did any of the Cup cars avoid sufficient body damage long enough to be able to make that assessment? [
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Hilux
New member
Co-incidence, cos thats what my current project is [
] (any tips) Back on the original topic........................
Seam welding has two main benefits 1) it stiffens the car and reduces deformation of structural panels in an accident 2) copes better with the stresses than spot welded panels that only assume a normal road life for the car.
Diver944
Active member
ORIGINAL: John Sims
Did any of the Cup cars avoid sufficient body damage long enough to be able to make that assessment? [
Heh, heh, heh - I remember watching some of those demolition derbies............, erm races [
]Without getting all brand snobby, it's important to remember that Porsche cars (certainly in the 80's) were built to a very high standard for a roadcar and you can't compare them to an old Golf or Beemer in that respect. They knew they would be 'club raced' when they built them and they have a huge history of being used in this way. I too have done many days on full slicks in my S2 and Turbo (though I am nowhere near driving the handles off them as Andrew does
)Particks fine. []
We do mostly 4 lap sprints like in the video clip I linked to.
http://uk.youtube.com/watch?v=JygHyzK4ZKc
That is the format of our club events. Of course we can do a lot more laps on basic midweek trackdays. So I guess it's possible for some negative effects due to sticky tyres. That has piqued my curiosity. I really wonder what the far reaching effects are? I suppose you could equally deduce that replacing all the rubber bushings/bearings with metal would also have an effect (apart from road noise)? I mean are we going to break welds, is the metal going to lose it's memory and the whole car sag? I really don't think these cars will but perhaps that's naivety combined with wishful thinking.
Having said all that, I still plan very much to do a trackcar (if the damn economy ever recovers!!) and I will have a full and correct cage and have some body strengthening done also. I've already got a special gearbox and the motor's half done so I guess I'm locked in. Anyone need some Coal over there?
]We do mostly 4 lap sprints like in the video clip I linked to.
http://uk.youtube.com/watch?v=JygHyzK4ZKc
That is the format of our club events. Of course we can do a lot more laps on basic midweek trackdays. So I guess it's possible for some negative effects due to sticky tyres. That has piqued my curiosity. I really wonder what the far reaching effects are? I suppose you could equally deduce that replacing all the rubber bushings/bearings with metal would also have an effect (apart from road noise)? I mean are we going to break welds, is the metal going to lose it's memory and the whole car sag? I really don't think these cars will but perhaps that's naivety combined with wishful thinking.
Having said all that, I still plan very much to do a trackcar (if the damn economy ever recovers!!) and I will have a full and correct cage and have some body strengthening done also. I've already got a special gearbox and the motor's half done so I guess I'm locked in. Anyone need some Coal over there?
ORIGINAL: edh
Lots of good points Patrick (or can I call you Partick? [
There are fewer crashes on trackdays compared with races - But I have seen a few cars that have rolled on trackdays at Donington (digging in at the gravel trap at the Old Hairpin). None of them were flattened in a way that would have threatened driver safety.
You may be increasing the stresses on your shell by running r-spec tyres, but I can't quite see it being significant. It's just something else to worry about, but way down my list. I wonder how Andrew Sweetenham's 944 is holding up? - he runs it pretty hard on trackdays on slicks. With the money you've spent, a re-shell every few years would be negligble anyway....
That talk of blancmanges reminds me of my first track car - A v6 Jelly Mould that I ran on s/h slicks (because it was faster & was fun to go past cars in a £500 shed [
btw - 3-6 laps? - I thought you Aussies were real men? [
For those who run slicks on their cars, Andrew and Paul, I'm interested to know what changes if any you've made to your sump to guard against the significantly higher chance of oil starvation. Also Andrew what suspension do you have in your car and what sort of springrates? From memory Paul I thought you had a stock sump? On one hand I'm delighted that you've not had any issues with your motor, but I'd also talk to Jon to cover off what he might think just as a precaution. If I'm out of line tell me to get back in my box. It's only out of concern of course. Then we get into what oils you use on the track..........perhaps leave that for another thread?
A fair question. I can get my oil light on going around Luffield with road tyres in the dry. Greater cornering/braking force will obviously move the oil more but, either way, it is sustained load corners that seem to be the problem in my case. Once the oil has gone from the pick up it makes no difference if it is at 40º to the sump pan or 60º to the sump pan, through greater force, it still isn't there.
I've never seen my oil light on John and to date all I've got in my sump is a LR pan baffle, which to the naked eye could be mistaken for a door hinge. I have had more than my share of engine failures and although only one has been due to a spun bearing, I have upgraded my sump significantly in the incoming engine. It's not much fun being on the sidelines with expensive repairs needed. I would stress that it's a good idea to modify our sumps if we go onto the track, especially with Slicks.
Diver944
Active member
I only ran slicks on my original 2.5 engine, possibly 20 days over 3-4 years, no adverse effects. Jon has asked me not to run slicks on the 3.2 unless I go dry sumped so I have only used road tyres and road legal track tyres on the 3 days I have done since the rebuild. Andrew will confirm I'm sure but I'm positive his is a standard sump too, on slicks for many, many days driven nice and hard. Again no ill effects.
My personal mantra is to ensure the oil is topped to FULL before every session, vastly reduces the risk of any starvation issues
Ok Paul, that's good. I agree with Jon. Especially on a rare motor such as yours. The question is what do we declare Hoosier type tyres to be? R-spec or slicks? I am intending to run them next season with a custom sump and will have a dry sump on the trackcar. I know that some people feel that the Hoosier and others, are a slick, but I believe they're not constructed quite like a slick and that they have road legal status in some cases/countries. I wonder what 'slicks' Andrew is running?
MarkK
Active member
I used Slicks (Pirelli) 7/8 years ago on my 968CS,it was a road car(no cage just big brakes,harnesses and aggressive geometery) with new M030 suspension cranked right up,did alot of trackdays over two seasons or so,wore out quite a few sets (i was getting them cheap from the guy that supplied tyres to the trackday company i used to use)as far as the bodywork was concerned it felt tight as a drum when i sold the car,but i think running slicks may have had something to do with the variocam going bang at Spa on the big uphill straight,as Paul says its a really good idea to keep your oil right at the top,and i didnt do that religiously and i reckon there might have been some oil starvation...??
Those trackdays running the slicks on the 968 were some of the most fun i ever had on a circuit -catching much "faster" big ego machinery up in the bends,brilliant fun,if i were to do it again one day it wouldn't be the stress on the chassis that would worry me it would be keeping the oil topped right up so the engine does't suffer as much.Brilliant fun,a new set of slicks gives such amazing adhesion but these days i would just be worried about all the stonechips you get at the track....sad or what.....
Those trackdays running the slicks on the 968 were some of the most fun i ever had on a circuit -catching much "faster" big ego machinery up in the bends,brilliant fun,if i were to do it again one day it wouldn't be the stress on the chassis that would worry me it would be keeping the oil topped right up so the engine does't suffer as much.Brilliant fun,a new set of slicks gives such amazing adhesion but these days i would just be worried about all the stonechips you get at the track....sad or what.....
Diver944
Active member
Yes they had no grooves - totally illegal for the road. They were Pirellis that were the one make supplied for the Porsche Cup over here around the year 2000. I bought them from the series tyre supplier at the time, real cheap and heavily subsidised at £55 per tyre fitted. I chose the hardest compound available (D5 I think) and the fronts lasted about 8 days each before the outer edge showed canvas due to running a road camber setup. Still had plenty of life left in the centre and inside edge. The rear tyres actually lasted 20 trackdays and still had lots of rubber left but I disposed of them because of age and cracks were starting to appear in the sidewall.
MarkK
Active member
I was driving up the main straight up the hill,car made an unhealthy noise and then there was some smoke out of the back,the car still managed to limp slowly around to the pits which was quite a way,opened the bonnet and there was oil everywhere,not good,it had been transported out to Spa on a lorry anyway so was going back on a lorry,it got back to England and i had it valeted (so it didn't look abused and got rid of all the rubber flicked up off the track)then i put its road wheels back on then called porsche assistance and it went back to the OPC )( BIG bill under warranty),but eventually it was fixed ,and i think i sold it pretty soon after...the guy who bought it after me tracked it alot too,he really liked the car,and i don't think he had any further problems with it.The slicks were great fun and the adhesion is more than double michelin cups or P zeroCs,had a couple of cheesed off people come up to me in the pits with comments like "oh thats why you were that fast,you are on slicks" but they are so much fun i didn't care[]
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