Tire Selection vs. Terrain: How Vittoria Rubber Saved 7.5% Effort on the Halo Loop
By Richard Wharton | August 2, 2026
Key Takeaway: The Energy Equation and Tire Selection
By switching to a Vittoria Barzo (front) / Mezcal (rear) tire selection running 19 psi front / 19.5 psi rear with foam inserts, I saved 19.1 Watts of normalized xPower (a 7.5% reduction in effort) compared to my November baseline, and trimmed 1:17 to 1:30 off my June Maxxis baseline climb times.
Multi-Month Telemetry: Tire Selection Comparison (Maxxis vs. Vittoria)
To evaluate true equipment efficiency across changing trail conditions, we must compare the early summer Maxxis setup (June 20) against the mid-summer Vittoria Barzo/Mezcal tire selection (July 24, July 26, and August 2).
Using xPower (Dr. Philip Skiba’s 25-second exponential weighting algorithm), we track normalized metabolic demand alongside speed and heart rate:
| Date | Tire Setup & Trail State | Duration | Avg Speed | xPower (Px) | Avg HR | Efficiency (mph / 100W xPower) |
|---|---|---|---|---|---|---|
| Nov 9, 2025 (Avg) | Baseline Setup (Hardpack) | 22:44 | 8.92 mph | 253.5 W | 164.7 bpm | 3.52 mph / 100W |
| Jun 20, 2026 | Maxxis Setup (Summer Baseline) | 23:20 | 8.69 mph | 222.7 W | 168.0 bpm | 3.90 mph / 100W |
| Jul 24, 2026 | Vittoria Setup (Moderately Packed) | 22:56 | 8.84 mph | 230.6 W | 169.3 bpm | 3.83 mph / 100W |
| Jul 26, 2026 (PR) | Vittoria @ 19.5psi (Packed / Moist Dirt) | 21:50 | 9.29 mph | 244.2 W | 170.0 bpm | 3.80 mph / 100W |
| Aug 2, 2026 (Today) | Vittoria @ 19.5psi (Loose / Dry Dirt) | 22:03 | 9.20 mph | 234.4 W | 168.2 bpm | 3.92 mph / 100W |
June (Maxxis) vs. July / August (Vittoria) Takeaways:
- Climb Speed Gain: In June on Maxxis tires, climbing at 200.7 W average (222.7 W xPower) yielded a duration of 23:20 (8.69 mph). Switching to Vittoria tires allowed speeds to jump to 9.20 mph today (22:03) and 9.29 mph on July 26 (21:50)—a 5.8% to 6.9% increase in climb velocity.
- Time Trimmed: The Vittoria setup trimmed 1 minute and 17 seconds (today) and 1 minute and 30 seconds (July 26 PR) off the June Maxxis climb time.
Descent Telemetry: Tire Selection, FLOW, & ShockWiz Scores
View the raw segment file on Garmin Connect.
Analyzing descent mechanics across the exact 1.92-mile descent segment—from the high ridge coordinate (39.568197, -119.860306) down to the base coordinate (39.573492, -119.848474)—reveals how tire compliance and suspension tuning interact on technical terrain.
Real-Time Coaching: Using Garmin FLOW Live on the Trail
To turn this telemetry into real-time speed on Peavine, standard 60-second rolling averages lag too far behind to capture rapid cornering dynamics. Switching your cockpit display to Garmin’s Instant FLOW field turns your Edge head unit into a live chassis compliance monitor. Because I know every switchback, jump lip, and rock garden on the Halo Loop by heart, seeing Instant FLOW spike above 8.0 on a familiar entry immediately signals unnecessary heavy braking, late turn-in, or suspension packing over chatter. By using Instant FLOW as a real-time feedback loop, you can consciously delay braking, open the bike up through chatter zones, and let the tire casing compliance carry momentum—yielding a smoother line, less wasted energy, and a significantly faster descent split.
| Date | Descent Split | Avg Speed | Avg FLOW | Peak FLOW Spike | ShockWiz Tuning Score & Setup |
|---|---|---|---|---|---|
| Nov 9, 2025 (Lap 1 & 2) | 8:52 / 8:58 | 13.0 mph | 4.10 | 48.0 | Score: 92 F / 92 R (Baseline Stiff / Hardpack) |
| Jun 20, 2026 | 8:44 | 13.2 mph | 3.80 | 52.0 | Score: 88 F / 96 R (Maxxis Baseline) |
| Jul 24, 2026 | 8:41 | 13.3 mph | 4.20 | 58.0 | Score: 88 F / 100 R (Vittoria Setup Baseline) |
| Jul 26, 2026 (PR) | 8:22 | 13.8 mph | 3.95 | 55.0 | Score: 92 F / 92 R (Balanced Suspension / Moist Dirt) |
| Aug 2, 2026 (Today) | 8:35 | 13.4 mph | 5.62 | 56.0 | Score: 76 F / 88 R (Overly Stiff LSC) |
Comparing June 20th to August 2nd highlights the direct relationship between ShockWiz tuning scores and Garmin FLOW. In June, achieving higher ShockWiz tuning scores (88 Front / 96 Rear) yielded a clean 3.80 Average FLOW. Today, with tuning scores dropping to 76 Front / 88 Rear, the Average FLOW degraded to 5.62 due to overly firm Low-Speed Compression (LSC) resisting small-bump compliance on loose dry soil.
The Math: Tire Selection Wattage & Percentage Savings
Comparing my historical baseline on Maxxis tires to my current Vittoria setup running 19.0 psi front / 19.5 psi rear:
1. August 2 (Today) Savings vs. November Baseline
I was 41 seconds faster today than my November baseline while consuming 19.1 fewer Watts of normalized power (a 7.5% energy savings):
Percentage Savings = (19.1 W / 253.5 W) * 100 = 7.5% Reduction in Effort
2. July 26 (PR Run) Savings vs. November Baseline
On July 26, I stopped the clock 54 seconds faster than the November baseline while outputting 9.3 W less xPower (a 3.7% direct reduction).
To ride 9.29 mph on the November setup would have required an estimated ~264.0 W xPower:
Speed-Adjusted Percent Savings = (19.8 W / 264.0 W) * 100 = 7.5% Total Efficiency Gain
Fitness Horizon: METs and Estimated VO₂ Dynamics
Beyond equipment efficiency, my physiological capacity is trending upward. Tracking estimated VO₂ outputs and Metabolic Equivalents (METs) across 1-minute, 5-minute, and 20-minute durations highlights this fitness shift (calculated for a 72.5 kg athlete):
- 1-Minute Peak Surge (Anaerobic Capacity):
- July 26 (PR Run): 337.4 W → 61.9 mL/kg/min (17.7 METs)
- August 2 (Today): 333.8 W → 56.7 mL/kg/min (16.2 METs)
- 5-Minute Peak Effort (Aerobic Power / VO₂max):
- August 2 (Today): 263.7 W → 46.3 mL/kg/min (13.2 METs)
- 20-Minute Sustained Threshold (Climb Pace):
- July 26 (PR Run): 213.2 W → 41.7 mL/kg/min (11.9 METs)
- August 2 (Today): 211.7 W → 38.5 mL/kg/min (11.0 METs)
My sustained 20-minute threshold power sits consistently around 11.0 – 11.9 METs. Because the lower tire pressure setup reduces the mechanical cost of the climb by ~19 Watts, I can stay beneath my aerobic ceiling without crossing into heavy anaerobic depletion.
Course Conditions: July 26 vs. August 2
The most striking contrast between my July 26 PR (21:50) and today’s run (22:03) lies in the soil state:
- July 26 (Damp & Packed): Moisture in the dirt created high traction and low rolling resistance. Tire knob penetration was optimal, allowing aggressive power transfer through every corner.
- August 2 (Loose over Hard): Consecutive weeks of summer heat without precipitation have pulverized the trail surface into loose “dust-over-marbles”.
Despite slipping and losing traction in technical switchbacks where July 26 was pinned, today’s 3.92 mph / 100W xPower efficiency ratio was actually higher than the PR run. This proves that lower pressure in flexible casing tires pays its highest dividends when trail conditions deteriorate.
Conclusion
Tuning tire pressures down to 19.0 psi front and 19.5 psi rear on supple Vittoria casings isn’t just a comfort tweak—it’s a measurable 7.5% performance upgrade on technical terrain, saving over 1 minute and 15 seconds compared to my June Maxxis baseline. When dirt turns loose and draggy, mechanical compliance beats raw horsepower every time.
