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Old 26 February 2000, 11:03 PM
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PhilBennett
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It is so funny but there are so many people with an obession for horsepower and yet, in my opinion, the money spent would be better spent in better suspension or brakes - or even just a spare set of rims with slicks mounted.

For the track day element a set of slicks around Donington National circuit is probably worth around 5 seconds. Which is at least 100 horsepower worth!
Old 26 February 2000, 11:24 PM
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Stef
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Really?
5 seconds, cool!

Stef.
Old 26 February 2000, 11:29 PM
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PhilBennett
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Honestly Stef - You're going to this track day on the 5th - Well he's a quick lap...

Start/Finish line will be flat out until you get to the end of the blue & white markings at the end of the pit lane. Then get on the brakes. 3rd for Redgate. Then on slicks it will be totally flat down the Craners, no lifting at all.

Back to 3rd for the Old Hairpin and it will be flat out all the way to McLeans, 3rd, and probably hold 3rd all the way to Coppice which is 3rd again then on down the straight.

Then which circuit you using? GP or National?
Old 26 February 2000, 11:30 PM
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johnfelstead
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just think, if i keep adding mods to my car i will knock so much time of the lap time i will be finishing it before i start it
Old 26 February 2000, 11:33 PM
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johnfelstead
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3rd down the back straight, thats pants. i was using fifth in my cossie
Old 26 February 2000, 11:58 PM
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NeilR
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Wales is a bit too wet for Slicks. I'll keep the extra 100 horses

No seriously, It rains all the time and also, the local bobbies might have something to say about them.

NeilR

Is the Impreza body strong enough to handle Slicks?

Old 27 February 2000, 12:04 PM
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PhilBennett
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You know loads of people are worried about damaging shells through the use of slicks.

For sure if you are always on track with very stiff springs then OK you may see a problem but the odd track day won't affect things at all.
Old 27 February 2000, 02:01 PM
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firefox
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What do you do when you have the brakes.. the suspension... and the ponies and still do a slow lap time?

J.

ps - And dont say rebuild the engine.. lol
Old 27 February 2000, 02:19 PM
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sunilp
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Jay

i know, i know...you let someone else drive it!!

[This message has been edited by sunilp (edited 27-02-2000).]
Old 27 February 2000, 03:21 PM
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PhilBennett
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Still slow after all that modification - That's easy to fix.

Just go and get some proper driver coaching -it is the cheapest and most effective way to go faster!

Oh - plus you don't have to worry about going bang or the change to 97 Octane fuel!!
Old 28 February 2000, 04:49 PM
  #11  
Stef
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Phil.
We use the shorter circuit normally.
I do pretty much everything you say above (although a tiny lift through Craner is sometimes necessary to prevent going straight to Mcleans!! ) , but I really can't see how using slicks would reduce my lap times (if we were allowed to time of course ) by 5 seconds.
I've always been concerned about the stress they would put on my standard suspension components.
Add to that the fact that it'd also be much harder to slide the car (wouldn't it?). I think I'd miss that!


Stef.

[This message has been edited by Stef (edited 28-02-2000).]
Old 28 February 2000, 05:17 PM
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PhilBennett
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Stef - Firstly this thing about slicks adding so much stress to your shell (and or suspension) that you wreck it is a myth.

I've seen 10 year old one make Rovers, with competition springs, that have only ever been raced on slicks with no cracks in the shells - so a 2-3 year old Impreza doing 3 or 4 track days is going to be absolutely fine.

The thing that will do most damage to the above is taking kerb - the harder you ride the kerbs the more you stand the chance to damage something. However we are talking constant use here - not a one off track day.

For instance at Silverstone school we use Peugeot 306 GTi 6's and Lotus Elise. I've only ever seen one suspension failure and that was on an Elise after an instructor was using it as the "fast-ride" car all day - who took kerb!

When all is said and done it is a personal choice. I guess ultimately you are happy to take some risk in that you are doing the track day in the first place.

Regards slicks - in a 280bhp WRX if I couldn't find that kind of time on the National circuit I'd be very surprised. You have two big braking points on the National circuit - into the chicane and into Redgate. There is no way you'll brake as late on road tyres as on slicks. So in those two places alone is 7-8 tenths lost.

Then we have the corner speed. On road tyres your minimum corner speed will be way down on slicks. If you take Coppice alone.

If you are just 5mph down in Coppice that will be 5 mph slower all the way down the straight - then the fact you get on the brakes earlier and you can see how the time saps away.

The final two point on road tyres is this. One they will overheat lots quicker so you will suffer from understeer sooner.

Two road tyres are easier to "over drive". It is so easy to just push too much and slide about more - which makes them hotter so they slide even more, etc, etc.

Getting the picture?!!!

I think that a 280BHP WRX on slicks would lap as fast as a near 400BHP car on road tyres. And would be able to keep those fast laps going for longer.

As for the Craners - on road tyres it would never be neat keeping flat. You'll just understeer wide and as the tyres get hot you'll be on the grass!!
Old 01 March 2000, 12:01 AM
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johnfelstead
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My own personal opinion would be to stiffen the suspension up first for 2 reasons.

1) you will generate more roll and pitch when on slicks as the tyre can produce more lateral G.
2) Slicks work much better when the roll centres and camber changes are minimal, they tend to dislike changes in camber in particular under breaking.

Please remember however, if you stiffen the car up for the track, it will be slower on the road as the suspension will not be as good at soaking up the changes in surface you see on the road.

It allways makes me laugh when i read posts on the BBS by people complaining about how the car rattles its nuts of with crap trim. I bet most of these cars are running uprated suspension that passes a lot of the stresses into the shell and distorts it under load rather than letting the springs/dampers soak up the road stresses.

In wet conditions in particular your scooby will be much faster on softer suspension than rock hard suspension.

I used to alter the damper settings on my cossie depending on whether it was wet or dry on the road.

On the esprit race car we take the anti-roll bars off in the wet and soften the dampers to increase mechanical grip, then increase the rear wing angle of attack and put dive vanes on the front to increase the downforce, this adds more drag but reduces lap time significantly from running with dry settings in the wet.

Thats why you see in F1 for example all the fannying on the grid if it is going to rain, settup in the dry is very different in the wet. I believe that is why shuey is ace in the wet, he spends more time than anyone else on his out laps before forming on the grid fine tuning the car settings just before the race starts, watch him this year, he is usually doing lots of one lap runs and back in the pits to fine tune in the 15 minutes before the grid closes, most of the others just go and sit on the grid and pose for the spectators.
Old 01 March 2000, 12:10 AM
  #14  
Stef
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John.
So basically, adjustable suspension IS the answer if I want to use slicks on track, and revert to normal setting for road use?
Hmmm...time to start saving perhaps?

David.
I'd love to! Come and see me in the morning.
Are you running with them straight away?

Stef.
Old 01 March 2000, 12:24 AM
  #15  
DavidLewis
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Stef,

I doubt if I'll go straight out on them, even if its a sunny day. I'll wait until the track has cleaned up a bit first. I've also got a set of part-worns booked with Mark to cover all options with regards to weather/track conditions. I'm sure we can work something out. I must insist on being in the passenger seat though
See you there (or at Watford Gap!)

P.S. I'll also be bringing spacers (just in case)

[This message has been edited by DavidLewis (edited 01-03-2000).]
Old 01 March 2000, 12:52 AM
  #16  
johnfelstead
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you have to be carefull with running very stiff rebound settings on your shocks when still on the standard spec springs. This is due to an effect called reverse jacking.

What happens here is that the suspension compresses then on rebound the damper doesn't allow the sping to extend back to its original lenghth fully due to the rebound setting being high, the next bump you hit the same occurs again. On an undulating surface this can keep on happening untill you have reverse jacked the car onto its bump stops, the next undulation you hit is fed straight into the shell as though you have no springs at all and you fly off the track totally bemused as to what the hell just happened.

You must match springs to dampers, whenever we are setting a car up and trying significantly stiffer springs we send the shocks of to Koni for revalving.

As you can see, its a bit of a black art, this is why people like the handling engineers at lotus can transform a crap car into an awesome car, just by getting the spring/damper settings spot on.

And this is why when you uprate the suspension you should do a complete package in one go, not shocks one week, springs the next.

confused now
Old 01 March 2000, 11:24 AM
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Stef
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Cheers guys.

I did think about putting slicks on my current wheels when I get my new ones, but was put off due to the stories about stress etc.
I suppose using a harder tyre would still enable some sideways movement though.
Is it advisable to have a stiffer suspension set-up before using slicks though, or are you saying that a standard UK car would be ok? Considering the amount of roll I get now I dread to think what it would be like using slicks!
Braking later is a plus I hadn't considered either, but I poo myself already sometimes!!!
See you both there.

Stef.
Old 01 March 2000, 11:44 AM
  #18  
DavidLewis
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Stef,

As I've offered before, I'll be bringing a set of hard compound Michelin slicks (bought from JohnS's Mate) on a set of standard 16in alloys. I'd be most happy to let you try them for size on the condition that I ride in the passenger seat
Old 01 March 2000, 12:14 PM
  #19  
johnfelstead
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Welcome to the BBS PhilBennett.

It is always great to see someone of your caliber join us in the banter/serious issues on the BBS. I am sure we can all learn something from your experience in top level racing.

I would just like to add to the issues on the use of slicks on a road car.

There are a few issues i feel are very important to note.

1) when on slicks the likelyhood of having oil surge problems is greatly increased as the standard engine does not have a particularily large capacity sump, slicks will make the car corner at higher lateral G and may cause oil starvation.
2) most of the drivers on track days have no experience of the immense grip you can generate with slicks, the down side to this is that when they break away, especially radial slicks, they tend to let go very quickly. Most people on track will never have experienced this and may overcorrect and end up in the pit lane wall.
3) I think it is actually more fun on a hard compound road tyre as they slide far more progresively, at a rate most drivers can cope with.
4) All the single make racers you mention will have seam welded shells and integrall roll cages, this adds masively to the strength/longevity of the shell when using slicks and when kerb hopping.

I have to agree with you that i would be very dissapointed if i could not knock 5 seconds off my lap time at donno when going from road to slick tyres.

I think people must try to remember that track days are for fun and not racing, i beleive more fun is to be had with crap tyres rather than top spec slicks. Personally if i were to use slicks i would go for a relatively hard compound to still have the car sliding, the main benefit would be that the tyres would last much longer than road tyres.

I think your offer of racing spec fuel is a very good one to help protect the higher spec STi engines in particular from det.

I use ELF Turbo FIA on the Group A rally car, and it is unbelievably expensive, it is worth 1 second per mile in the forest however which adds up to one minute by the end of the rally, a massive difference.

I think the guys running high boost or STi spec motors would be well advised to use a mix of SUL plus the fuel you could supply.

cheers
john


Old 01 March 2000, 01:35 PM
  #20  
PhilBennett
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Yeah agree with John - and in many respects have multi-way adjustable dampers (i.e Bump, rebound - and now you can get 4-way adjustable i.e High & Low speed Bump & rebound) just isn't worth it unless you are on-track all the time.

One reason is that to get it right you need to spend alot of track time just setting things up.

As a rule of thumb if you get to full bump adjustment and you feel that you still need more bump - it is time to get stiffer springs.

I've not really driven an Impreza hard on a proper race track - I imagine that they understeer quite a bit?

I guess one thing you could try is to go up on front & rear rollbars - that way like John said you could disconnect them if it rains, which is a quick "fix" compromise?! (is that a real phrase?!).

If lap time isn't important then I'd buy the hardest 165/60 M + S tyres, run them at 3 bar and practise reverse flicking all day!!

Oh and that way you can forget the kerbs - you can take grass, gives you more room to turn in!

Come on Cadwell Park!
Old 01 March 2000, 01:48 PM
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Pete Croney
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Wow, at last a thread with some seriously good discussion.

Here's my twopeneth...

John and Phil, I couldn't agree more.

On the subject of slicks, I use these if the circuit is dry and the difference is just incredible. The pointability and amount of lateral G can never be matched with road tyres and standard suspension. Have a look at the footage at the end of Scoobytrax. It is easy to take 150m out of an STi, through Craner alone.

Anyone using them for the first time... pressures and temperatures are very important. You should aim to have 28-30 psi when they are hot. I run approx 32 psi for the first two laps of the day, to heat them up and then re-set the pressures. The first lap, on cold slicks offers less grip than a standard road tyre, so caution is required. As they come up to temperature, it as though the car locks into rails

As John says with suspension, I run very soft in the wet (6-8 clicks) and near max stiffness (20-22 clicks) with slicks in the dry.

As for Phil's description of Redgates and Craner, I am flat from the exit of Redgates, into 4th at Hollywood (the fast right hand bends after Redgate) and flat in 4th all the way down to the old hairpin. This gives over 110mph down Craner, probably 15 to 20mph faster than is possible in the standard car.

The other point about slicks is the effect on braking distance. If the brakes can stand it, you can use so much pedal that you can move your brake points nearly 50% further. It is possible to lose over 1mph per metre.

Perhaps I have always been lucky with build quality, as I have never had any squeaks from any of my Imprezas.
Old 01 March 2000, 04:26 PM
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James Adlington
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'...if the brakes can stand it...'. What effect would running slicks have on standard brakes (MY98 in my case). Is it a case of having to modify both brakes and suspension(?) before using slicks becomes at all sensible, or more a matter of not being able to making best use of slicks with a standard car?
Old 01 March 2000, 04:47 PM
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PhilBennett
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Pete - just out of interest do you run on standard springs and roll bars?

Yeah slicks are mega.

As an aside the best way to get cheap slicks is to ask the race teams for their cast offs. Most of the time they will give them to you for free as they have had the best out of them.

If there is a tyre van there and anyone has a spare set of rims I've got some old Rover turbo slicks people can try.

I think they are 210 size for 16 inch rims. I'll need them back however but it will give people an opportunity to try them. Let me know.
Old 01 March 2000, 05:19 PM
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Blow Dog
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James,
When brakes are mentioned, I always have a say. Standard Impreza brakes arent any cop, especially for track days. Couple this with slicks and I would imagine you would be coming in from brake fade every 2 laps (thats if you ise brakes to the max, like i do).

If you can, get some uprated pads and discs, it will be totally wise to do so, especially if you plan on running slicks.


John,
I am running my 97 again at Donnington, and as far as I know, I am as race prepared as I can be. One of my priorities on my wish list is a better spoiler. I see you mention them above so I have a question for you. Although an STI spoiler or Prodrive high rise (RB5) looks the part, would I notice any difference in handling over a 97 low spoiler on track days if I was to buy one of the monster ones? At £500 a pop, they arent cheap, but does their purpose serve function as well as aesthetic value?
Cem

Old 01 March 2000, 05:37 PM
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PhilBennett
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John can't you get a Performance Friction or Mintex 1166 or 1177 pad for an Impreza?
Old 01 March 2000, 06:23 PM
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chambjj
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Phil Pete and Co, I have bought a set of 16inchers for the track and I see that you advise hard compound slicks, for some ssssslide-ability.
Can you recomend a set that suit the scobby and do not have the sudden breakaway that some tyres seem to have.
Old 01 March 2000, 06:34 PM
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James Adlington
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Cem - I thought as much! I'm currently using Mintex 1155s, but the brakes still aren't up to much even with road tyres. Guess I'll have to leave the slicks in the garage until i can afford some brembos
Old 01 March 2000, 06:49 PM
  #28  
Ian Cook
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PhilB, Pete runs Leda adjustable gas suspension on his car, with matched springs.
Old 01 March 2000, 07:20 PM
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johnfelstead
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BlowDog, take a look at this thread, it has some pictures of the esprit race car i am talking about when talking about changing aero load in the wet.
Old 01 March 2000, 07:21 PM
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Pete Croney
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Hi Phil

I use adjustable coilovers.

If you use slicks with the standard brakes, then the braking performance is unchanged... are just as effective/ineffective. The difference with slicks is that the extra grip can be transfered into extra braking performance, without locking up. With big brakes, it almost feels like hitting something and is very scary for passengers... eh Stef (Cadwell)?


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