333pg333

Just wondering if those that have used both R spec rubber and slicks on the same car...do you have to change your suspension setup at all, much, totally etc?

What tyres have you used (size/brand/compound)?

Am looking at competing in 3 different series next season and it looks like 2 of them will be on R spec. We have a few more options on R spec rubber down here and some of it is soft and very quick, but they only last 1-2 hotlaps. So it's like a qualifying time as such.

I'm still thinking that a soft slick will be outright fastest and have the choice to use that in the 3rd competition but am wondering if I am sacrificing 33% of setup data to switch and also if it may involve a quite different suspension setup.

IcemanG17

on my 928's I ran both R comps (A6 R6 R1 RA1 R888) and slicks Pirelli scrubs.....kept the alignment setting the same on all.....toe at zero and lots of camber....3.3' front and 2.5' rear

The single biggest difference I found in slicks is huge improvement in grip....I also found them easier to control at the limit....once they started to slip it was very easy to control

The downsides.....they take FOREVER to warm up on a cold day....might never really warm up if they are hot weather slicks like the pirellis.....

I did find the slicks tend to like lower tire pressures......for example Pirelli recommends up to 36 psi hot for front engine-rear drive...but the lower I dropped the pressures the better they performed....now I run 30-31psi hot just like the cup cars run

The pirelli P zero slick 275/645-18 in DH (hard) compound...I get them with 2 cycles on them......they perform well for maybe 4 more....cord at about 6..... 18x10x65mm wheels all around 2850lbs off track (wet with driver)...I recently got a set of Michelin N1 Porsche cup tires....they are 25/64-18 and rated as "soft" in reality they are maybe .25" narrower than the Pirellis.....I also have a set of DM (medium) pirellis I need to try.....245/645-18

I ran slightly smaller Hoosiers & BFG R1's....245/45-16 all around

333pg333

Thanks for that feedback. Different cars but valuable info. My biggest concerns are the different sidewall constructions as I understand that R specs are still made much the same as a road tyre. i.e. softer than a slicks stiffer/lighter sidewall. I've always assumed one has to use stiffer springs when changing to slicks but I have had differing replies on this elsewhere.

IcemanG17

I did make suspension changes along the way......I went from 600lb front to 800lb front and had all the shocks rebuilt-revalved to match the motion ratios.... NO DOUBTS....while I haven't tried R comps since I made the change I have dropped 4 seconds per lap....

Slicks are much lighter & much better....there is a reason why they are so expensive and don't last very long.....think about it like an eraser.....a soft one will rub out everything quickly.....but a hard one takes forever to rub anything out....and tears up the paper doing it....just like R comps....

It all comes down to your budget and goals....slicks, especially fresh ones are the single fastest tire out there (michelins are regarded as the best) In terms of R comps......in my opinion Hoosier A6 is the best...but also does not last long and cycles out quickly just like a slick....

333pg333

Thing is, we have faster R comps than you do. Well, not 100% that they're faster than an A6 but I would be 95% sure. They're very soft and as I said, last for literally 1 or 2 (at best) hotlaps each h/c.

To put it into perspective. At our local track a well driven 997 Cup would lap around 1:31 - 1:32. A Cup S might just crack into the .29's. The fastest Aussie V8's qualified in the high 1.27's - .28's at the last Time Attack the winner did a 1:25 flat on Hankook Z221's! That was first time in competition for that car too. The rules are a lot more liberal in some respects but there were a dozen cars running on R spec rubber as fast or faster than a Cup car. You can only get a couple of laps out of these tyres each heat cycle with the soft compound but these Evos etc are going very fast on R spec rubber.

Not the same car but just to give you an idea of how fast these guys are getting out of their R spec tyres.

333pg333

Bump...nobody else runs slicks and R specs on the same car???

CRex

Here's a comparison for you. Times are for ZIC where Group B (non-pro) drivers qualify around 1:40-42 in the PCCA running MY12 Cups on Mich N1 slicks.

Actual laptimes on my 997.2 GT3RS using new tires as baseline. In most cases I've gone through 2+ sets of each:

• Pirelli DH Slicks: 1:47-48 (add 1 sec after ~4HCs, HC out by 10-12th)
• Hoosier R6: 1:49-1:50 (add 1 sec after ~10HCs, another 1 sec after ~20HCs, HC out by 25-30th)
• Pirelli Trofeo (original not newer R's): 1:50-1:52 (add 1 sec after ~10HC, cord by 10-15th HC)
• Mich Pilot Sports Cup+: 1:51-52 (these were my OEM rubber and street-driven, hence no accurate HC count; but they were HC'd out by my 10th track HC)
• Toyo R888: not available in 997.2 sizes but in my 997.1 the times were similar as MPSC+'s, except they heat cycle out even sooner

Hearsay (emphasis being that) is A6's shave a second to a second and half off R6's (which puts it in Pirelli DH territory). Don't know how Mich N1 and Pirelli DH compares since there's no apples-to-apples comparison (the former only available in 18" sizes which I've not tried).

There may be another second or even second-and-half to be shaved from my slick times but I simply didn't have the kahunas (or skills) to take it there when I was on them

wanna911

Some of them are 100% surely faster than A6's but other than an occasional C91 in Evo STI sizes you won't see those tires you see over here. And yes, some of them are ALMS GT fast with just as big of a budget.

Another question for you to ask yourself is what is your budget, how long will you run each set. The longer you run a set, more than likely the more the slicks are advantageous pending your wear patterns.

I think some of it also depends on how many clean laps you can get if you are not driving a heavy car or with AWD. Some of those super fast Rcomps are going to be as fast or faster than off the shelf slicks. Our benchmark here is the A6. From watching my competitors on them I have seen anywhere from about .8-1.5 (AWD-RWD respectively) slower than a Hoosier R80 then up to 3 seconds slower than a Michelin Slick which from what I've heard and read here are significantly faster than the Hoosier slicks. A friend and forum member here ran about 2 seconds faster in his AWD 996 Turbo from R6's to R80/100 and about 3 seconds faster on the Michelins.

I think overall if it's close you will be better served maximizing your potential on the R-comps rather than switching back and forth unless you have enough time to test. Now it may be worth the effort to buy or borrow a set or slicks and run them back to back with same settings (or easily adjustable at track) to see how they do. I may try that this year as well as I have some series that I can run slicks with no penalty in myself. But I'm not going through the trouble if I have to change alignments every event and just haven't put the effort into optimizing slicks. And over here, you get 1-3 clean laps at best so hard to make the slicks work.

But if that 2-3 seconds for Michelins is true

Must try that.

333pg333

Thanks for that. A very nice comparison list of a few different tyres is always handy. I realise that this doesn't apply across the board with different cars, but still can add data to give more than a thumbnail guide. Looks like you're doing some good times compared to the Cup cars. Congrats.

Sure, budget is a big consideration. Testing time = budget also. I guess ultimately some soft slicks perhaps with tyre warmers might still be worth trying. Not really viable in our little racing world. The fastest guys in the series we run that allows slicks are pretty much Cups/RSRs on Michelin stickers but there's one guy doing some very respectable times on soft A050s in a 996gt3.

ps...where do you guys buy your slicks?

IcemanG17

excellent data......I also concur that the Michelin N1's are the best....all of the GT3 cup guys that I talk to confirm it...... They also say the N1's tend to hold performance a bit longer than the Pirelli slick....

For example a friend that races in the GT3 cup would always use scrub slicks when the series ran yokohama....because he felt the small drop in tire performance wasn't something he couldn't drive around....this is the same driver that WON the GT3 cup in 2010 series and got a free trip to germany!!! On scrubs no less.... Once the series switched to pirelli's he can no longer drive around the performance drop of the pirelli's...so he is forced to buy fresh tires per event.....and doesn't run as much because of it

ProCoach

^^This^^

iTrack

In 4 events I ran Dunlop Z1's, Hoosier R6's and Hoosier slicks. I did not make many changes to the car. I did add a little more camber going to the R comp's from street tires, but the rest was done in shocks adjustments. The only thing you may notice is the "feel" of the tire. Sidewalls are different so R comp's and slicks react differently from each other.

I would say give it a try. I think you will spend a little more time learning the difference in grip then changing the setup. .02

333pg333

Very interesting that he did this on scrubs! Well driven him. As for the Michelins being the best, a few guys in here extol the virtues of Dunlops. I didn't think they had much of a presence in the U.S. but there you go.

Ha, Peter, you're normally quite descriptive and detailed in your replies. New Year's still got your tongue?

Thanks for that. On my old car's setup I have run Nitto NT01 and Hoosier R80 slicks on the same day. We had stuffed up the suspension setup for that day and with the Nittos on it was an understeering squeeling pig. When I merely swapped over to a different wheel/tyre combo with the slicks, the car behaved quite differently. It was my first use of a real slick on that car and I was amazed how it transformed the car from bad U/steer to a very sharp turn in vehicle. So much so that I kept cutting over the apex's too much and upsetting the car. The braking was also amazingly better. However that was 2.5 years ago on different suspension, aero and power so I guess there's nothing for it but to try.

ProCoach

Patrick!

My experience is yours. I think you MUST optimize the setup (springs for handling balance/bars for response time/alignment for most efficient and effective use of the tire) for EACH type of tire.

I ran RA1's, R6's and bias-ply Goodyear Blue Streak slicks one day on my Alfa (race car for forty years, not even close to streetable) and when we did temps and pressures, we found that the car drove differently on each and the balance changed, too. Car was MUCH faster on slicks than the other two (was not that much quicker on R6's over the RA1's, much to my surprise) and MUCH easier to drive OVER the limit!

The purpose-built cars I'm driving now are SO sensitive that between Avon, Goodyear and Hoosier bias-ply slicks, there is a substantial alignment (camber) and spring rate (up to 100 lbs or 20%) change required for optimal performance on each. This is at track-record levels of performance. Do your homework and try and make the effort to find out which tires like what, then change between series outings, if you're going to use the slicks.

The US Dunlop slick dealer (well, Dunlop has actually stopped in the US as of the end of last year) is right across the street from me. Dave at SascoSports. Good bloke!

333pg333

Peter

That's interesting to hear of your Alfa. What model? Good to know that was much better on the slicks.

If you speak to Dunlop Dave, ask him if he knows the 280x655x18" and 310x655x18" in the D31 compound. By the sounds of it this might be the combo I'll try next. They're used successfully on cars down here that are modified sedans that run large V8's up front with possibly less aero than I'll have access to but a little bit lighter than my car. So not super close but not entirely different.

Trying to do the homework, but I think there is also the old 'suck it and see' situation. At least the camber shouldn't be too different between a radial slick and R specs, whereas I think a bias ply require less camber than both?