Used PWC tires for track days?

Discussion in 'Corner Carver Racing Tech Discussion' started by DILYSI Dave, Jun 4, 2018.

  1. DILYSI Dave

    DILYSI Dave forum member

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    Anyone running the Pirelli 305/680/18 cast offs from the PWC Porsches on their Mustang? Looks like a decent size, and they go for pretty cheap in the used market.
     
  2. Strengthrehab

    Strengthrehab forum member

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    Lots of people seem to be procuring them per FB groups I've seen.
     
  3. Speedboosted

    Speedboosted Found missing cylinders

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    I run the Continental slicks (not sure how much of a difference there is between the two). For what it's worth, I have a set of four 305/685-18 Conti slicks that I'd sell for $400. They have very little use, 2 heat cycles.
     
  4. o2sys

    o2sys forum member

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    I was running N0 Michelin Pilot Sport A/S designed for the Panamera's and they were great tires. For being A/S they hooked great, rode nice, and low tread noise.
     
  5. ShelbyX3

    ShelbyX3 Junior Member

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    For those running 305/680/18 are you having any rubbing issues on the front on hard/sharp turn-ins; especially if you are running brake ducts? Everyone I talk to said 285 is the widest you can go on the front and still maintain the turn radius and minimize the chance of rubbing on the duct work?

    I am looking for another set of track tires but am worried with the 305 width....

    GT
     
  6. ApexRaceParts

    ApexRaceParts Official Site Vendor

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    It really comes down to running the correct offset wheels up front, getting those wheels perfectly centered in the space available. On my personal car, I run our 18x11" ET52 EC-7 with a 20mm spacer (because of the coilovers) with 305 slicks and it doesn't rub the 3" cooling ducts. Before the 11s, I ran the same 305 slick on a 10" wheel and it didn't rub either.

    Certain cars came with different thickness steering rack limiters as well, based on what wheels they had from the factory. This plays a big role into what will rub or not rub at full lock. On my other Mustang (same year, but originally a 6 cylinder car with 16" wheels), the 10s would rub at full lock because of how much more movement the rack would allow.

    - Cory
     
  7. Sky Render

    Sky Render Stig's Retarded Cousin S197 Team Member

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    Rock auto shows 3 different part numbers for tie rods, the difference being where the limiters are for the different wheel sizes:
    • 19"
    • 18"
    • 16-17"
    Which limiters give the most room?
     
  8. ApexRaceParts

    ApexRaceParts Official Site Vendor

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    Limiters for cars with smaller wheels will allow the rack to turn more sharply. It's more about the width of the wheel, not diameter but in this case the larger the diameter, the wider the wheels happen to be. So I guess to directly answer your question, the 16-17" one you listed last would give it the most movement. But because you can turn sharper, greater chance of rubbing at "full lock".

    - Cory
     
  9. Vorshlag-Fair

    Vorshlag-Fair Official Site Vendor

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    So this glut of 305mm PWC tires seems to be hitting the Mustang crowd lately at cheap prices. I wanted to share this experience as a possible warning - I bought two pallets of new/sticker sets of Conti DP slicks in a similar size in 2014. The results were surprising...

    [​IMG]

    I was so happy! I think I paid like $100/each for NEW slicks, so I thought I had hit the Lotto. I was set for tires for like 2 seasons! These were affordable, brand new, and in a fairly wide 305/650/18 size. The street tire I was running at the time was a 275/40/17 on an 18x10" wheel, and as you can see below these 305s dwarfed those...

    [​IMG]

    Height was initially a concern, as these 650mm tire heights were on the short end of the spectrum of what fits an S197/S550. But when you do the math the 650 mm height translates to 25.5" tall, which is almost exactly the same as a 315/30/18, which we ran in Hoosier DOT flavors for many years... works well on a lowered S197 race car.

    [​IMG]

    We tried these 295/40/18 Hoosiers as well - and even though they were close to the OEM tire heights, they ended up being VERY tall for a race tire (and much slower than thee 315/30/18 in back-to-back test). So the 25.5" tall tires are what we mostly ran on our S197 for 4 out of 5 seasons.

    [​IMG]

    We tried mounting the 305mm Conti slicks onto an 18x10" wheel (above right) and it was a very poor fit. The same tire mounted to an 18x11 wheel (above left) worked much better.

    [​IMG]

    Above this is the same 305mm Conti slick mounted to an 11" wide wheel (left) and 10" wide wheel (right). The 10" wheel squeezed the tire BADLY and was too narrow for proper track use. The outer 1/2" of tread on each side wouldn't touch the ground. Wasted tire. So my point is - only use on an 11" wide wheel (or wider) with these tires.

    [​IMG]

    We ran these at an HPDE test event at Texas World Speedway on March 29, 2014, using our 2011 GT / NASA TT3 car which was coming along in its development (had won all of the TT3 events in 2013-2014 to that point). We had set the TT3 track record there the September before so we had a good baseline to work from. The temps were good at this March 2014 event, too.

    [​IMG]

    By that time we had 2 seasons of testing with this car at this track on DOT 315/30/18 Hoosier A6 tires and my previous best in this car here was in September 2013 at a 1:50.675 lap (TT3 record). I was hoping these cheap Conti slicks I got on close-out would be comparable, maybe even faster? I mean, damn... these are REAL SLICKS, right?

    [​IMG]

    Amy drove the Mustang at this TWS event for two days (about 3.5 hours worth) of light HPDE use, running some low 1:59s. I took one session (3 lap stint) each day, and Mike Patterson (AI racer that usually wins all of the races in Texas) took some laps Sunday. I managed a best of a 1:56.2 lap. That meant that these 305/650/18 Continental DP slicks were 5.5 seconds slower than the 315 Hoosier A6. And the all four tires were corded at the end of the weekend.

    [​IMG]

    We didn't run this TWS CCW configuration again until April 25-26, 2015. At that NASA race weekend I ran a 1:49.926, resetting the TT3 track record both days (not one of my better showings, but a win is a win). This was on a 335F/345R Hoosier A7 - again, a DOT rated tire. We would typically run these Hoosier A7s for multiple weekends with 2 drivers without cording.

    [​IMG]

    So my impressions of these Daytona Prototype tires was: they were garbage, and I dumped the rest of the new Conti tires I had, for a loss. Sure, they have shiny letters on the sidewall and are used "on real race cars" but that doesn't mean they still don't suck on 3800 pound pony cars. ;) Your result may vary. These PWC tires are likely different, but I'd still bet money they are slower than a 315 DOT Hoosier.

    Cheers,
     
    Last edited: Jun 25, 2018
  10. SoundGuyDave

    SoundGuyDave This Space For Rent

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    I'm with Terry, on this... Sort of. I didn't do the 305's, I ran a couple sets of CTSCC 275/645-18 slicks on my Enduro car, and while they were stickers, they "felt" like a slightly dead Hoosier R6 (which was my prime rubber) in the same size. What the CTSCC tires did, though, was wear like iron, and the grip didn't fall off like the Hoosiers did on extended runs. With the R6, I would wind up cording the fronts JUST before the three-hour mark, but the CTSCC went a full 4.5hr race, losing around 2 seconds from start to finish. Those same tires then did duty as the "screw-around" tire for track days, and I want to say they finally corded after another full weekend or two running 4 to 6 15-25 minute sessions per day. I'm not sure they'd go a full six hours; I think my math came up with them dying at around hour 5.5. Given that a tire change would HAVE to happen, it just made sense to change them out without pushing them to the ragged end-of-life and taking the lap-time hit.

    IIRC, those DP tires you had were purpose-engineered for high-downforce lightweight cars on banked ovals, so it's not a complete shock that they didn't work on a non-aero 3800lb lead sled. Just saying.

    Recently, I've been able to get scrubbed Pirelli P-Zero slicks from the PWC series (hard compound 285/645-18), and that's a completely different animal. Squirmy/Greasy for a lap or two until the heat comes in, then it's like driving on Velcro. Until you push too hard, then the grip just falls off. Turns out the "ideal" temp range is only about 25* wide. When you're in that zone, though, gawd do they grip. LatG went from 1.4 on R6 to peaking a tick over 1.8. If the tires you're talking about are from the PWC (Pirelli World Challenge) they won't say "Continental" on the side, and they are serious big-boy tires. With 850lb/in front springs, I felt under-sprung for those tires, there's just that much grip available once you get your pressures and temps together. You WILL want to set the car up for those tires, and not run whatever setup you use for streets or DOT-R compounds. They are as much a step up from an R6/R7 as the R6/R7 was from a street tire...

    Finally, keep in mind that in any series that uses a control tire, like CTSCC or PWC, everybody is on an even playing field, so it really doesn't matter (to them) how grippy the tires are or aren't, since everybody is going to have the same issues. So, yes, there is a bit of the "used on real race cars" factor, but for a "budget" track-day tire, you really can't beat the scrubs or scoring last-year's-model of tire that isn't legal any more. If you're on the pointy end of an open-tire class, though, then that's a bit of a different story.