PIRELLI TIRE TEST, WILLOW SPRINGS RACEWAY
TEMP: 99F ambient, surface at 130F
BIKE:Â 2009 Yamaha R1, 6,000 miles on the odometer
-Â Â Â previously owned by Ken Hill of Ken Hill Coaching and Yamaha School of Champions
-Â Â Â at the start of the test, the new Pirelli Pro slick tires were put on by CT Racingâ€™s Chris McGuire during a track day hosted by Track Daz.
- 2008 R1 forks set flush with the 2009 upper triple clamp
- Ohlins 25mm cartridges installed, valving C5 and R3
- Fork springs 1.0kg in both legs
- Fork oil standard Ohlins oil set at 165mm air gap
- Preload at 9 turns in
- Rebound at 12 clicks out
- Compression at 9 clicks out
- 2009 stock R1 shock with stock spacer in place
- Preload at 3 turns back from max
- High speed compression at 1 turn out
- Low speed compression at 5 clicks out
- Rebound at 12 clicks out
- Gearing is stock, stock chain, rear axle position standard, based on correct chain slack
- Pirellia Super Corsa Pro slick front 120/70×17 set at 27 psi cold
- Pirellia Super Corsa Pro slick rear 190/55×17 set at 21psi cold
This was a 4 lap scrub in period. With the track temps being so high, there was plenty of heat in the ground to get the tires hot quickly. Each lap was quicker, focusing on the following:
- lap 1 straight line braking and acceleration
- lap 2 trail braking and mid corner throttle
- lap 3 corner exit acceleration
- lap 4, fast lap at 90%
Once the 4 laps were completed, the in lap was the same pace as lap 4. The pressure gauge was calibrated earlier to ensure accuracy. Upon entering the hot pit, the bike was parked quickly and hot pressure set at 32 psi front and 26psi rear.
Session 2: (started immediately after tire pressure was set, total 8 laps)
The goal of session 2 was to evaluate tire structure under aggressive braking re steering. With 32psi hot pressure, would the tire hold up structurally so that I could steer the bike not only going into the corner apex, but also during initial trail braking? During aggressive straight line braking in turns 1 and 5, the front tire seemed â€˜roundâ€™ allowing easy transitions to trail braking yet felt as though it needed another 2psi to keep better structural rigidity. Brake dive was not an issue as braking at this track is over a long distance at high speeds, but 2 turns of fork preload andÂ 2 clicks of fork compression were added based on the location of the zip tie towards the bottom of the chrome tube. The 2psi was added immediately once I entered the Pirelli compound. There were some severe chassis problems starting to appear creating a lot of instability.
Session 3: (started immediately, total 8 laps)
The goal of session 3 was to assess mid corner stability and turn 2 was the corner of choice. Entry speed was a little too fast allowing the front tire to scrub speed, but the throttle was set for a constant radius arc to assess handlebar action side to side/rowing. After a couple of passes through turn2, changes needed to be made especially with the track going uphill and then flattening out. The bike would turn in well but as soon as the bike started on the uphill grade, the front tire felt as though it was about to let go. If the throttle was backed off a little, the tire gripped well and steering became much more positive.
The tire showed no indication of any tear at all, even with the obvious chassis problems I was having:
The forks were raised 6mm through the triple clamps to put more weight on the front end to give better grip.
Rear tire was showing very rough graining where the bulk of the power was being laid down exiting corners, not where neutral throttle was being applied.
BREAK TIME for hydration and recollection of thoughts â€“ 15 minutes
Session 4: (2 warm up laps on the tires and 6 fast laps;- total 8 laps)
The goal of session 4 was early positive throttle to test rear tire grip in turns 2, 8 and 9.Â As this track requires you to be on the throttle as early as possible, swing arm angle is critical for rear tire and mechanical grip. With the bike at close to max lean at 150mph while dragging oneâ€™s knee, this is a unique characteristic to Willow Springs. You have to slowly work up to this test and when the bike is under the most severe g-load, the tire will spin if the swing arm angle is too shallow.
Once the pace really heated up, the rear tire would most certainly let it be known that help was needed, so we pulled in to add shims to the rear shock.
Note that that front tire is now obviously being worked much harder with a lot more deformation to the tire surface.
With less weight on the rear tire, the graining pattern started t become much more linear and certainly no where near as deep and rough.
BREAK for shock removal and 6mm spacer insertion (took lunch)
The bike was raised on foot peg stands and the top shock mount bolt loosened with a 22m wrench. The rear stand was used to support the swing arm as the clevis nut was removed and the top shock bolt removed. Spacers were placed on top of the OEM spacer, making a total ride height change ofÂ +7mm. The shock was secured, all nuts and bolts tightened and everything double checked. Forks remained in the same position as a control.
Session 5: (2 warm up laps on the tires and 8 fast laps;- total 8 laps)
The goal of session 5 was to reassess mid corner stability given the geometry change with increased swing arm angle and a balance point change in the chassis.Â Turns 2, 8 and 9 were again used for this test, with same corner speed entry and same throttle position during the turn. Turn in was much improved with much less effort required and the mid corner line corrections were much easier to make.
The rear tire wear improved very slightly, but the soft rear spring for my weight really showed itself to be inadequate here at the Big Track. Using the stock shock, we added all the preload and set Low speed compression to 4 clicks out to stiffen the shock in the worst g-load situations, but that did not help at all so we removed those changes.
Session 6: (total 15 laps)
The goal of session 6 was to ride the bike at an increasingly faster pace, using the same testing criteria as in earlier sessions to assess braking/steering, mid corner stability and corner exit drive. In running a high number of consecutive laps that would also allow me to get a great feel for the carcass movement under all skill execution conditions.
At the end of the testing period, the tires wore extremely well, no signs of tearing at all. I was most comfortable with the front at 34 hot and the rear at 26 hot for this track. Â I felt that the front tire was superb in feel and grip and completely trustworthy, but I need a lot more time to play with the rear tire to create settings that will allow me to trust the rear tire the same way. It just didnâ€™t feel as secure, even though other riders were going faster on the tire that weekend during the races. As with all tires, you create geometry and settings that allow you to be comfortable and trust the tires, so thereâ€™s more work for me to do.
For the testing period, that was 51 laps x 3 miles = 153 miles.