R60 hoosier compound weekend
So, all this talk about the R60 rear tire being so bad is interesting because I ran this last weekend with AAS and it was 100 degrees, crazy weekend.
The numbers are this, with the R20 compound tires I'm within .200 sec of Andy Mckee (thats who I compared too) but this weekend I was 1.000 sec slower but it was very course dependent (super fast course), but with new R60 I thought I would be closer. No big deal on average I'm .880 sec slower.
I'm not trying to be an advocate for the R60 compound tires because I believe you don't have a site like Crows Landing where you can take full advantage of the R60 tires. Still not as fast as the R20 Formula ford tires and that's where the Formula continental rims and R20 compound tires would come into play, so all can play through out the Nation.
Ben
Testing FC Sized Wheels/Tires
Hi all,
Dan Cyr and I have been testing a borrowed set of FC sized wheels and tires on my Reynard for a couple of events and have some data and observations to share. The tests were very positive.
First off, the tire specs. We are comparing a borrowed set of Hoosier FC 20.5x7 front/ 22x8 rear R60A new this season with 8 club racing heat cycles, compared with Hoosier FF 20.5x7 front/ 22.5x7.2 rear C2500 R25B 5 year old tires (my 2018 Nationals tires) with approximately 40 runs. We did not intend to test both a tire construction difference and a compound different, but that is all we had to work with.
The test vehicle: My long time Reynard 88F, which, despite my 9 year sabbatical from the sport, has been both autoxed and club raced bouncing between the two disciplines from 2000-2008 and then from 2017 to current. We used the chassis set-up from 2005 (the last year Nationals was at Forbes Field Topeka) which garnered 2 Pro Solo class wins, a Pro Solo Open Challenge win (Toledo), and 2nd (Dan) and 3rd place at Nationals, and 2nd in CML (Dawn Odoi). It is a good car.
Test Site: We attended an open test at Grissom AFB (all concrete, high grip, similar to Lincoln) in late June, at which we had approximately 1.5 hours of testing and laid down 20 test runs between us. We also ran the two sets of tires at the CAM Challenge event this past weekend at Grissom. I plan to test the tires on a low grip asphalt lot at a local test and tune this weekend.
The results: First off, the FC rear tires are quite a bit shorter than the cantilevered FF tires (69 1/2" circumference vs 70 3/8") which necessitated a minor rear ride height correction when changing tires. The rear camber was also corrected to be consistent between the two tires/ride heights at 0.8".
At the test and tune, we ran 4 sets of 5 hot laps, me driving the FF tires, Dan on FF tires, then Dan on FC tires, then me on FC tires. The track was quickly drying after a brief misting/drizzle. Weather was cloudy/partly cloudy, 78F. Track temp 85-90F. After learning the track on the first two runs, both Dan and I ran consistent 40.0 times on the FF tires, hot lapping the tires at 4-6 minutes between runs (start of lap to start of lap). The track was still slightly evolving from a brief shower just before the start of our testing. On the FC tires, hot lapping at a consistent 3.5 minutes run start to run start, Dan's last two runs were 39.8, which I matched by my 3rd run, with the final two runs at 40.1 due to a downed pylon in the fast 7 cone slalom.
Considering the track evolution, we consider the tire performances to be equal, but the following items must be taken into account:
We are trying to separate the tire size/construction from the differing compound and age of the tires.
Addressing the tire sizes and construction:
1. We see no real difference in performance between the tires. The FC rear tire is actually slightly smaller than the FF cantilevered rear tire, both in height and in width. Where the FC tire has the advantage is the non-cantilevered design actually plants the tire better. We actually preferred the feel of the FC tire on turn-in and in slaloms as the rear of the car felt more predictable with less lateral movement. There was no issue putting the power down with the smaller FC tire.
2. We did not make any chassis adjustments to compensate for tire performance. The cornering balance of the car felt the same between the tires. That said, the car had a slight understeer that we addressed at the CAM event that was not tire dependent.
3. The shorter FC rear tire changed the shift points slightly, allowed us to shift to 4th in a high speed section of the course, where we used 3rd on the FF tires. This could be an advantage or a disadvantage depending upon your gearing. We have the Reynard geared very tight with lots of overlap between gears.
4. Tire pressures: FF 15/17 stabilized, FC 15/16 stabilized. The tires grew 0.5 psi from the cold settings, and stayed there. Pressures were checked, but not reset, between runs.
Addressing the compound differences:
1. We are comparing newer R60 tires to 5 year old R25s. How many of us would consider 5 year old tires competitive on a national PAX index?
2. The R60 did not have the grip of the R25 at the beginning of the run, despite hot lapping the car as fast as possible considering the format of the test event. We were not able to take the first 2 turns at WOT on the R60 tires, but were able to take those turns easily flat WOT on the R25s. We believe that this speaks to the inability to get the R60s into their temperature operating window, even with hot lapping the car.
3. Due to time constraints, we were not able to get data of 5-15 cool down times between runs on either the R25 or the R60 tires. We were literally the last car to run at the test event. We suspect that the difference between the R25 and R60 compounds would be greater in that environment.
4. Tire temps were 125-130F as measured between runs on both the R25 and R60 tires.
5. Given the high grip nature of the track surface, the hot lapping nature of our testing, and the warmer summer temperatures, these conditions would most favor the R60 to perform similar to the R25. Lower grip surface, lower temps, and longer time between runs would most likely create a larger difference in tire compound performance.
Results from the CAM Challenge event: This past weekend we ran the CAM Challenge at Grissom, running the Sat morning session on the FF R25 tires, and the afternoon session on the FC R60 tires. We let both Robert Christmas and Dale Frame (Area 4 director who was on site for the AM) know our intentions. Temps were in the 80s, track temp in the 90s, with sun in the morning, and a partly sunny afternoon after a rain shower. Again, times were similar between the tires running with 2 drivers and 10 minutes between runs, both Dan and I in the 41 second range, but we were 4 seconds off the pace in the indexed Race tire class, and 2 seconds off of FTD of David Montgomery running his XP Porsche in the 39s raw. That speaks a little to our driving, and more to the overall grip level we had with 5 year or R25s and newer used R60s. We kept overdriving the R60s on corner entry and getting into the marbles, costing us time. There is no way that new R60s would have kept up with Dave on raw time, but new R25s would have. We had a small ignition cut out issue that made us decide to not take our final runs on Sunday as we did not want the car to die on course. (I am suspecting that my 20 year old soldered wiring job is starting to fatigue.)
Overall, we really liked the performance of the car on FC tires/wheels, and those tires/wheels did not force any changes to the car other than a simple ride height correction. The R60 compound, however, was given the best opportunity to outperform 5 year old R25 tires, and it only matched it. Based on my experience being forced to run R60 compound in club racing, I expect the R60 performance to degrade much more than the R25 in anything less than ideal conditions similar to what we tested in.
I am going ahead with again recommending the allowance of the FC sized wheels and tires for the class for the following reasons:
1. The wheel and tire sizes are used in several club racing classes (FC, S2000, F1000, etc) and therefore the tire options should not be in danger of shrinking or being eliminated.
2. There is no real change in the vehicle performance envelope and thus the PAX does not change.
3. Only rear wheels need to be acquired, which should be available used for almost every vehicle eligible for the CM class. (Remember, wheels are cheap, tires are expensive.)
4. Allowing wheel/tire options are consistent with previous modified class rules changes and does not devalue the CM cars nor prevent them from moving back and forth between autox and club racing nor between different sanctioning bodies. (Remember the allowances granted to create the FM Solo Vee.)
5. In our opinion, the FC wheel/tire combination actually drives better than the FF tires do.
I am also writing against the R60 spec tire for the following reasons:
1. Forcing a spec tire or a tire rule would create a new precedence within the modified classes which is outside of the objective and the spirit of the modified classes.
2. A spec tire would immediately obsolete every tire that we have in our inventory, costing all of us over $1200 per set to replace. Money that we could never recoupe by selling the old tires. This would cost us much more money than a couple of wheels.
2. The PAX index would need to be greatly adjusted and would never be correct for any given weather and environmental conditions, thus handicapping all CM classes by rule in any combined class situation, both Nationally and locally.
3. A spec tire would intentionally reduce the performance level of the CM cars, which creates a dire issue of class sustainability. If the CM class is restrained by tire, as some have proposed, then the FM class would most likely have a higher performance level than the CM cars. Considering that the initial purchase price of a decent CM car is 2-3 times the initial purchase price of an FM car, and the FM car has higher performance and would be more enjoyable to drive on a non-restricted tire, why would anyone want to buy a CM car? Ultimately, the CM class would be eliminated and merged with FM, and FF would be uncompetitive in that class.
I am concerned that, after a discussion with Dale Frame at the CAM Challenge, he stated that they were seriously considering the spec R60 tire option (mostly likely with a lot of prodding from Hoosier). If that is the case, then anyone who is not in favor of that needs to write a lot of letters, to the MAC, the SEB, your area director, and anyone else who matters. I still feel that any tire or wheel allowance decision should be made by the class members, not the SEB, the MAC, or the tire suppliers. We are talking about the survival of the class, and the wrong decision will most likely lead to the demise of the class. Do we want that to happen? Remember, it is not in the best interest of the MAC or the SEB that the class survives as both the MAC and the SEB are under constant pressure to reduce the number of classes within the solo program. This would just be an convenient way of moving forward toward that target.
As stated above, we plan on testing the FC tires/wheels on a local asphalt lot for more data. I will let everyone know what we find. If anyone is in the Detroit area this Saturday (for anything besides the Dream Cruise), you are welcome to join us and drive the car.
R&S Taking Orders for R20 Rear w 2024 Delivery...
Via R&S:
Quote:
2024 CM Rear Tire
Pre-Orders for the CM Rear Tire is open until 2/1/2024.
If we get enough pre-orders (60 or 108 Tires), Hoosier Racing Tire will build them.
This is the only planned build for the 43305 in R20 Compound, CM rear tires in 2024.
Use our handy Pre-Order form at:
https://www.rsracing.com/cmreartiref...KT_6HzfcoHOED8
Time for the class to "put up or shut up" w regards "qualifying" tires :beer::beer::beer:....