DUNLOP TIRE TEST, THUNDERHILL RACEWAY PARK
TEMP: 95F ambient, surface at 130F
BIKE:Â 2009 Yamaha R1, 5,500 miles on the odometer
previously owned by Ken Hill of Ken Hill Coaching and Yamaha School of Champions
at the start of the test, the new tires were put on by Race Ready Motorsports at Thunderhill during a private day hosted by Dan DeNuzzio who was running the track in a clockwise direction (not the normal direction).
- 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
- Dunlop 211 GP-A front 120/70×17 set at 30 psi cold
- Dunlop 211 GP-A rear 190/55×17 set at 18psi 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 36 psi front and 23psi 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 36psi 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 5, 9 and 11, the front tire seemed â€˜roundâ€™ allowing easy transitions to trail braking yet provided a sensation of excessive brake dive. One turn of preload was added to the front forks which took away the initial brake dive problem and compression and rebound settings remained unchanged.
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 high speed bumps in 2, 5 and 9.
The shock changes were HSC to 1.5 turns out, LSC at 5 clicks out and preload set 2 turns softer at -5 from max. No changes to the forks.
During this session we had the beginnings of a front tire tear:
Note the tearing on the sipe edge and the faint tear line around the circumference of the front tire.
Rear tire was showing initial faint tearing 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 aggressive trail braking to assess front tire tearing and see if we could clean it up by manipulating preload only with the increased tire pressure. We started at max preload and came back 1.5 turns each lap.
With max preload the bike wouldnâ€™t change lines anywhere unless the throttle was closed. As preload was reduced, the chassis became more neutral and could be made to change lines but still required forceful input on the bars.Â At 5 turns back from max preload, the tire seemed to clean up while giving excellent feel during trail braking in turn 14.Â However, the tire tear was still present, therefore we decided we needed to make a geometry change to the bike, mostly based on accelerated rear tire wear.
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 Turn 2 was 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.Â However, the chassis would still not finish a corner unless leaned on heavily.
The rear tire wear doubled in width and depth. The original appearance was that of a cold tear, but this image shows that with much more forceful riding with the hot pressure at 23psi, the tear turned into more of a hot tear, with the pattern curving into the center of the tire.
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 15 laps, the rear tire tear was even worse and testing was suspended as the rear tire was trenched and could not provide any further grip for effective testing.
The 2010 Dunlop USA 211 GP-A cannot be reversed â€“ period, end of story so we could not flip the tire and figure out why the medium hard was tearing and stop that happening.
For the testing period, that was 51 laps x 3 miles = 153 miles.