AMA report from Barber Motorsports Park, AL

SAFETY FIRST RACE REPORT, AMA NATIONAL
BARBER MOTORSPORTS PARK, AL
4/17 to 4/20


Thursday Promoter Practice:
Session 1, ride the bike and validate reference points from last year.

BIKE 1:
Gearing 15 x 45
Rear axle at 39.5mm

Fork Position +7mm
Springs .95kg
Preload 10 turns in
Rebound 1.5 out
Compression 1.25 out

Shock ride height: +5mm
500lb spring
10mm free sag
HS compression 40 out
LS compression 9 out
Rebound 12 out


Session 2 evaluate gearing:
BIKE 2:
Gearing 15 x 44
Rear axle at 56.1mm

Fork Position +7mm
Springs .95kg
Preload 10 turns in
Rebound 1.5 out
Compression 1.25 out

Shock ride height: +7mm
500lb spring
10mm free sag
HS compression 40 out
LS compression 9 out
Rebound 12 out

Session 3:
Bike 1 gearing at 15 x 44, Rear axle at 42.2mm
Bike 2 gearing at 15 x 46. Rear axle at 32.5mm
Fork height retained, rear ride height changed to +6mm on both bikes.

Focus: gearing for drive off the corners, chassis geometry for finishing the corners, 6 laps per bike.

Result: Bobby stayed out for the entire session leaving no time for Bike #1


FRIDAY:
Focus: repeat session 3 to evaluate chassis and gearing.
Bike #2, 6 laps, Bike #1, 8 laps.

Result:
46 rear sprocket chosen
Fork preload changed to 11.5 turns in to eradicate chatter.
Bike # 2 had better geometry, base line chassis chosen

BIKE 2:
Gearing 15 x 46
Rear axle at 32.5mm

Fork Position +7mm
Springs .95kg
Preload 10 turns in
Rebound 1.5 out
Compression 1.25 out

Shock ride height: +5mm
500lb spring
10mm free sag
HS compression 40 out
LS compression 9 out
Rebound 12 out

Lap times in low 1:30’s but race time will be in the 28/29’s. 45 rear sprocket may be more appropriate, and Bobby’s poor sector 2 times validate this. After discussion with Owen, Bobby and Gabor 45 installed (new chain on bike #2 to retain axle position, rear ride height change to reflect geometry differences).


SATURDAY:

BIKE 1:
Gearing 15 x 45
Rear axle at 37.08mm

Fork Position +7mm
Springs .975kg
Preload 8 turns in
Rebound 1.5 out
Compression 1.5 out

Shock ride height: +6mm
500lb spring
10mm free sag
HS compression 40 out
LS compression 9 out
Rebound 11 out

Practice 1:
Focus: work hard on 2nd segment to improve times from 27th position, and trying to get to target time as set by leaders (too fast and you loose entry speed into segment 3). Also evaluate fork changes for initial turn in.

Change to bike #2 for back to back comparison. Rear axle at 37.38mm.

Result:
Fastest time 1:28.9 on bike #2
Fork preload changed to 11.5 turns in to eradicate chatter.

NOTE: make both bikes identical for qualifying in all aspects as far as possible. Only discrepancy was rear axle position off 0.3mm between bikes.

QUALIFYING: 25 mins

Focus:
Use Bike 1 to get warmed up for 5 laps, 6 max. Yellow front at 31 psi, White rear (2 hard laps on it yesterday) at 26.5psi after 90 minutes on the warmers.
Bike #2, new yellow front and new white rear and get 5/6 laps with faster riders.
Preload changed to 12 turns in.

Result:
Qualified 14th on the 4th row. Goal achieved.

SUNDAY:

RACE:
Yellow front at 31psi hot and 234 rear at 26.2psi after 90 minutes on the warmers.
Track temp 127 degrees, ambient 86 on pit clock.

Bobby finished 12th, Gabor 13th.

Final settings:
Fork height: +7mm
Spring rate .95kg
Preload 12 turns in
Rebound 1.5 turns out
Compression 1.25 turns out

Shock ride height +7mm
500lb spring
10mm free sag
HS compression 40 out
LS compression 9 out
Rebound 12 out