Anecdotal evidence suggests that rims that get hot are more likely to release a tire, resulting in blowoff. The maximum temperature experienced by a rim used as a braking surface depends on many factors, and the rim temperature at which a particular tire will creep off the rim varies by factors that are not easily quantified.
What this study attempts to do is to record new "high temperature events" observed on one of my two bikes, noting various conditions under which the observation was made, the maximum temperature reached, and whether or not the tire blew off the rim. As data is added to the table below, I hope at some point to be able to conclude a maximum safe operating temperature for a particular combination of conditions, and perhaps a maximum safe operating temperature in general.
The rims I use are equipped with non-reversible temperature sensing labels from Omega Engineering. A non-reversible label identifies the highest temperature experienced and does not reset as the measured object cools down. It is a "peak reading" meter. Table data in the "Maximum Rim Temperature" column are given as an interval (X, Y), where X is the highest temperature dot that turned color, and Y is the next dot on the strip that did not turn color. Where there was no "next dot on the strip", Y = '?', which means that the maximum temperature is not known, only that it is higher than X. Data in the other columns should be self-explanatory.
| Bike Ridden | Total Mass (kg) | Front or Rear Wheel | Rim | Tire | Tire Pressure (psi) | Tire Age (years) | Tire Distance (km) | Ambient Air Temperature (C) | Maximum Rim Temperature (C) | Blowoff? | Other Notes |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Power Pursuit F2 | 132 | Rear | Ritchey OCR-Pro 559, ca. 2003 | Ritchey Tom Slick 559x36 (kevlar bead) | 75 | 1 | 300 | 22 | (121, 127) | No | Descending the backside of Mt. Hamilton |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 2 | 6500 | 19 | (104, ?) | No | Descending the north side of Hicks Rd. |
| Power Pursuit F2 | 132 | Rear | Ritchey OCR-Pro 559, ca. 2001 | Kenda Kwest (Hi-Pressure) 559x38 | 75 | 0 | 56 | 12 | (143, 149) | No | Descending the backside of Mt. Hamilton |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 2 | 6700 | 18 | (116, 121) | No | Descending Sierra Rd. amongst crowds slowly, after ToC, Stage 4 |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 2 | 6750 | 21 | (127, 132) | No | Descending Redwood Gulch Rd. carefully, using more front brake than usual |
| Power Pursuit F2 | 124 | Front | Bontrager Maverick 406 | Schwalbe Kojak 406x32 | 90 | 2 | 2500 | 35 | (82, 88) | No | Descending the east side of Mt. Madonna Rd. |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Stelvio 406x28 | 90 | 8 | 300 | 30 | (?, 132) | Yes | Descending Montebello Road carefully, using more front brake than usual, coming to a complete stop at the sensor cutout to activate the gate. The tire blew off while I was stopped trying to trip the sensor. This tire can be mounted on the rim without using tire levers. |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Stelvio 406x28 | 80 | 8 | 400 | 20 | (82, 88) | No | Descending Alpine Road (west) |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 3 | 1500 | 20 | (93, 99) | No | Descending Upper Rock Creek Canyon Rd. |
| Power Gold Rush | 136 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 3 | 7700 | 20 | (116, 121) | No | Descending On Orbit Lane |
| Power Pursuit F2 | 132 | Rear | Ritchey OCR-Pro 559, ca. 2001 | Kenda Kwest (Hi-Pressure) 559x38 | 75 | 1 | 3380 | 12 | (149, 154) | No | Descending the backside of Mt. Hamilton |
| Power Gold Rush | 127 | Front | Bontrager Maverick 406 | Schwalbe Stelvio 406x28 | 90 | 9 | 40 | 20 | (149, ?) | No | Descending Mt. Umunhum Road |
| Power Gold Rush | 127 | Front | Bontrager Maverick 406 | Schwalbe Stelvio 406x28 | 90 | 9 | 190 | 15 | (88, 93) | No | Descending Tunitas Creek Road |
| Power Gold Rush | 127 | Front | Velocity A23 | Ritchey Rov'r 406x34 | 75 | 11 | 180 | 30 | (93, 99) | No | Descending Alpine Road (west) |
| Power Gold Rush | 127 | Front | Velocity A23 | Ritchey Rov'r 406x34 | 75 | 11 | 300 | 25 | (121, 127) | No | Descending Kings Mountain Road (riding brakes behind slower traffic) |
| Power Pursuit F2 | 125 | Rear | Ritchey OCR-Pro 559, ca. 2001 | Kenda Kwest (Hi-Pressure) 559x38 | 75 | 0 | 25 | 33 | (?, 154) | Yes | Descending west Alpine Road. One layer of Velocity Velotape replaced the thicker, cloth Velox rim tape. |
| Power Pursuit F2 | 125 | Rear | Ritchey OCR-Pro 559, ca. 2001 | Kenda Kwest (Hi-Pressure) 559x38 | 75 | 1 | 150 | 40 | (116, 121) | Yes* | Descending Kings Mountain Road. *Failure was not a blow off but a tear at base of the tube's valve stem. I suspect the tire slid circumferentially on the hot rim. |
| Power Gold Rush | 119 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 1 | 800 | 25 | (143, 149) | No | Descending On-Orbit Lane |
| Power Gold Rush | 127 | Front | Sun L14 406 | Schwalbe Kojak 406x32 | 70 | 1 | 5000 | 32 | (154, 160) | Yes | Descending Upper Zayante Road; tire was loose enough to be re-mounted without the use of levers. |
| Power Gold Rush | 127 | Front | Velocity A23 | Panaracer Minits Tough 406x32 | 80 | 0 | 1980 | 30 | (138, 143) | No | Descending Jamison Creek Road |
| Power Gold Rush | 119 | Front | Velocity A23 | Panaracer Minits Tough 406x32 | 80 | 1 | 4300 | 5 | (?, 143) | Yes | Descending Summit Road, Mt. Diablo; tire was an extremely tight fit. |
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