Side effects of semi-slicks?

[deviant]

I have been doing a few trackdays but feel the need to be competing so I am going to enter my daily driver Impreza in to a sprint / hillclimb championship.

I am going to get a second set of rims and use semi-slicks but I am wondering if I am likely to see greater wear placed on other parts of the car...has anyone else had any problems arise from running more grip than normal?

[DavidY]

The more 'grip' you have the more stress you will potentially put on the suspension and driveline.

Also although the breakaway point will be higher, when it happens it will happen more quickly and at a higher speed (and therefore be harder to catch)

Sprinting and Hillclimbing in general probably puts less stress on a car than a hard trackday.

Personally, I would put the wheel/tyre idea on hold and compete in a couple of events in the standard car, this way you'll find out if its really for you without incurring too much expense. Decent overalls, boots, gloves, helmet cost enough to start with!

[swtmerce]

The greater grip will also make the car more susceptible to fuel and oil surge i.e. starvation of either due to the cornering forces. With Imprezas, it sometimes ends in a blown engine. There are ways to combat these issues however - fuel swirl pot and baffled sump.

[LaurenceFrost]

I think that for sprinting you normally have a control tyre in the class you enter in an effort to even things up, so you might not actually have a choice in which tyre you run.

[steveavxt]

There have been problems with the Elise and is variants when semi slicks are used. It puts too much stress on the Track rod end and they have been known to snap.

[deviant]

I should have mentioned...the regs are a lot more relaxed here in Aus. There is no real Aus wide championship or standard regs to stick to so tyre choice is pretty much up to the individual or the organiser to pic a reg to apply to the series themselves and there is no requirment for overalls and gloves though they are reccomended.

I'm guessing that semi's are not really going to get up to temp on a 60 second or so hillclimb so I would need something soft?
The series also includes regularity trials which are normally 4 or 5; 5 lap sessions on a full circuit so anything soft enough for a hillclimb is likely to be to soft for a circuit session?

Oil surge is a worry and I know Imprezas have a bit of a weak spot when it comes to oil control so I definately need to keep that in mind.

[steveavxt]

Soft compound semi slicks are available. Toyo do the R888 ggg series.

[Jubal]

My STI used to eat wheel bearings when wearing semi slicks. It did take grip to another level tho!

[blueg33]

DavidY said:

Sprinting and Hillclimbing in general probably puts less stress on a car than a hard trackday.

I wouldnt be so sure. Sprints and hillclimbs stress the drive train through repeated standing starts. Leaving 10 metre long 11's off the line must cause stress. Track day is harder on the brakes as you are running the car for longer.

[GreenV8S]

If you're pulling higher lateral G then you'll get higher roll angles which will affect the optimum geometry. This will probably mean more -ve camber all round for a start, and you would probably want to increase the roll stiffness all round to prevent the peak roll angles from getting excessive.

[deviant]

GreenV8S said:

If you're pulling higher lateral G then you'll get higher roll angles which will affect the optimum geometry. This will probably mean more -ve camber all round for a start, and you would probably want to increase the roll stiffness all round to prevent the peak roll angles from getting excessive.

Hmmm thats something I had not considered...As I understand it semi slicks generally dont work very well with more tyre friendly factory geometry settings which would make it hard to just swap rims over at each event.

[GreenV8S]

deviant said:

Hmmm thats something I had not considered...As I understand it semi slicks generally dont work very well with more tyre friendly factory geometry settings which would make it hard to just swap rims over at each event.

Yes, the more extreme you go the greater the impact on the rest of the car. A fully committed track setup is going to be pretty miserable on the road just in terms of ride comfort, feel and kickback as well as running the tyres on their corners. Depending how soft the tyres are they could suffer a great deal of wear gently pootling on the road just because of the camber you need to exploit that grip on the track.

[blueg33]

GreenV8S said:

deviant said:

Hmmm thats something I had not considered...As I understand it semi slicks generally dont work very well with more tyre friendly factory geometry settings which would make it hard to just swap rims over at each event.

Yes, the more extreme you go the greater the impact on the rest of the car. A fully committed track setup is going to be pretty miserable on the road just in terms of ride comfort, feel and kickback as well as running the tyres on their corners. Depending how soft the tyres are they could suffer a great deal of wear gently pootling on the road just because of the camber you need to exploit that grip on the track.

But you can have so much fun on the bendy bits!

[Zumbruk]

deviant said:

there is no requirment for overalls

Also, the more grip you have, the higher a chance you have of rolling the car.

[GTWayne]

I really do think that you are all overdramatizing a little as to how you need to be sooo careful when using slicks. Yes, all of what has been mentioned COULD happen, but is it really more likely if you are running slicks?, I don't think so. I used a set of full slicks for the first time on my BMW e36 M3 @ Goodwood ( a fast track ) earlier in the year and entered into the situation bearing most of what has been mentioned in mind and to be honest, there was no need. If you are a bit of an overenthusiastic driver with little or no feel for how settled a car is then maybe you should think again ( or even stay at home )but anything other than that and I would say no problem. I have done around half a dozen T/D's since and have used slicks every time , I think they are fabulous. Several T/D's ago it started to rain @ GW and I stayed out just to evaluate the tyres behavior and I have to say I was most surprised to find the slicks reacted without issue in all but standing water ( little different to 888's in my experience ). When I did eventually come in the Marshall's at the pit lane entrance cheered and clapped, I would like to think it was my ability that impressed them but it think it was more than likely they were just relieved that they did not have to come and retrieve me from a tyre wall or some such

[shim]

the extra grip of slicks shoulnt be underestimated

if you look at the cornering G forces from data loggers it shows the disproportionate increase in G force on the car and driver as you move up to semi slicks but especially slicks

if they let go at max force the way the car behaves will be significantly different

i am certainly no safety nerd but the two things i promised my self for track days are;

1. not to run slicks without a cage
2. not to do the Nordschliefe without a cage

i know lots of guys that do and none have had bad offs so it can be fine but if you look at the data closely you may have some new pros and cons to weigh up

[weed]

Once you put slicks on the car, you and your wallet have just fallen off the top of a slippery slope.
you'll discover that the standard suspension geometry cannot keep the tyre treads flat on the road. the wear on the outside tread/shoulder of the tyres will be excessive.
So the new menu will be:
1,Anti roll bars.
2, Camber plates.
3, Stiffer springs.
4, Matching dampers.
5, Tools to manage the above.
6, safety equipment.

But the ride will be fun.

m

[deviant]

Thanks for the further advice guys. I'm swaying towards not getting them for now and just going for some high end, road performance tyres instead.

I'm hearing some good things about these new Toyo R1R's

http://www.toyo.com.au/Proxes%20R1R.htm

More grip than a normal road tyre but not as hard core as a semi-slick so should be friendly on the car and wallet!

[shim]

i agree slicks are tempting and i get tempted every year but always manage to persuade myself to save it for my race car 9when i get one)

as saiud above the car will need suspension and geometry changes to work the slicks properly and the bushes will need upggrading or they will not cope very long with the stresses

[GTWayne]

^^^ You are indeed correct in what you say with regards to geo, bushes etc. but having used slicks ( and still doing so ) myself I can not agree that they are some kind of 'top secret weapons grade type weapon' that deserves ultra respect and caution whilst in operation. Having an opinion based on technical knowledge is one thing but it will always be no better than a close second behind practical experience