7 June 2005 -- Nanoraptor Blowouts
Problem Summary
Several (at least 5) blowouts, here in the Northeast USA and in other areas of the world, of tubes installed with the Race Version (Kevlar bead) of the 700c WTB Nanoraptor tire have indicated tire problems. We speculate that the tire's lock on the bead is not strong enough, even at well under recommended max pressure, and the tube slips out between the tire and rim and expands until it bursts. Basically there is a slight gap where the bead has folded over and slightly damaged, or deformed. This allows there to be a full fold there, not just a bend. We suppose that these deformations or misalignments help keep the bead from locking in properly, especially with narrower rims where the tire-rim angle is more extreme. This theory is supported by WTB's stipulation that they not be used with tubeless setups.
This problem has occurred on at least 3 different unicycles, one of which was
brand new, custom-built of new, carefully-inspected components. Blowouts
have occurred 4 times while riding and once while unattended, resting in an
apartment.
Latest information suggests that this problem is confined to the Race Version, which has a folding Kevlar bead. The problem is likely due not to a BSD that is too large, but due to the interrupted nature of the bead interface caused by folding deformations.
Suggested Course of Action
Cease using the Nanoraptor tire (Race Version) for unicycling. This suggestion applies to both on- and off-road, since the problem appears to be independent of whether the wheel is under load. It appears that the continuous steel bead version (non-folding) does not have the same issues that the race version does.
It may be true that the Race Version is suitable for the wider KH 700c rim. There is no data available that suggests that this is a bad combination, and LiveWire has a wheel currently under test with this configuration.
Additional Comments
The Nanoraptor tire has been an excellent tire for both on- and off-road unicycling. LiveWire has notified WTB of this problem and have received helpful and informative responses (see "Follow-up" below). We also would like to note that WTB's website indicates that the 700c Nanoraptor tire is designed for off-road use, not for road use.
Alternative tires with similar volume include:
road - Big Apple 700c x 2.3 or x 2.0 (tested extensively by LiveWire), or WTB Nanoraptor 700c (wire bead version only)
off-road - WTB Motoraptor 700c x 2.1 (not tested yet by LiveWire, but we have good reports)
Freshness of this information
This information is the best available as of 31 July 2005.
Follow-up
Other unicyclists abroad (Canada and New Zealand) report similar problems (blowouts) with the folding bead version. It can be identified by the colorful printing on the side, and by the fact that the bead, when folded, appears to be formed of segments, not one smoothly continuous wire. In particular, riders in New Zealand have had enough troubles that one well-known rider actually sold his 29er in frustration. The indications that Tony Melton of www.unicycle.co.nz described, "blowouts, resulting in the inner tube splitting 5 or 10cm dramatically or the inner tube getting shredded" are the same indications we saw here. They also saw that the problem was independent of rider weight.
WTB has contacted LiveWire and suggests that the problem may be with the folding bead (Race) version, and specifically wants to know if the steel bead version is causing problems. They specify that the folding version is not to be used with tubeless setups, and should not be used with rims narrower than 21mm. However, since the Rhyno Lite is wider than 21mm, it appears that, at least for unicycling use, the tire is not recommended. LiveWire currently has a Race Version on a KH rim (about 35mm wide), with no problems so far. However, it seems prudent to avoid using the race version for unicycling.
If anyone else has had a unicycling blowout problem with Nanoraptors, please contact our shop with a brief description of the incident, including the tire, rim, bead type, and any batch numbers on the interior of the tire. Please send your comments through us so that we can organize them into a single communication.
Supporting Links
See the Alps Tour Rider's Blog for descriptions of three of the blowouts. A thread presenting this alert appears in Gilby's Unicycling Community forum here.
Copyright © 2005 LiveWire Unicycles
Last modified:
07/31/2005