Author: Fritz Stafford
Published: June 8, 2015
Tubeless tires done right have many benefits over tubed clinchers, but tubeless tires require numerous installation and maintenance premiums in comparison to (easy to use) tubed clinchers. Tubeless tires require skills and equipment that are not required for tubed clinchers, and one may need to rely on bike shop, initially at least.
Tubeless tire benefits can be maximized and premiums minimized by careful selection of wheels and tires. Many “tubeless” wheel models are available that do not provide all potential benefits, and many good quality clincher wheels can be converted to tubeless (e.g., welded rim instead of “sleeved”), but again, may not provide all the potential benefits.
Note the brands and models mentioned herein are intended as examples of the feature(s) being discussed, rather than recommendations.
Tubeless XC MtB and CX Tire Benefits
- Puncture resistance (e.g., goat head and other thorns, cacti needles, tacks and small nails)
- Pinch flat resistance due to tube elimination, although sidewall pinch flats are still possible
- Rolling resistance reduction (i.e., elimination of rubbing between tube and inside of tire casing)
- Traction improvement due to wider tire profile resulting from lower rim sidewall
- Traction and shock absorbtion improvement due to ~30% lower tire pressure enabled by tubeless operation
- Weight reduction possibilities (lower rim sidewall, narrower tire)
Lightweight Tubeless Al alloy wheels are available from all the leading wheel manufacturers, and these are a great choice for XC MtB and CX. Al alloy wheels are proven reliable technology, strength versus weight tradeoffs are well understood, they are widely available with widest range of options, and hence, the most cost effective choice. Stans BST rims have lower sidewall which provides improved wider tire profile and lighter weight.
Tubeless Carbon rim wheels that provide significant weight reduction benefits are also available for XC MtB. One claim of Carbon wheel manufacturers is lateral stiffness equivalency or superiority as compared to Al alloy rims but with improved radial compliance for shock absorbtion / comfort. One key downside of tubeless Carbon rim wheels is the ~2X – 3X price premium.
In addition to rim weight, rim width is an important consideration, especially for tubeless wheels. Wider rims are heavier than narrower rims, but they provide two key benefits, wider tire profile that provides improved traction (especially when utilizing Stan’s wheels with BST technology), and improved strength. The wider tire profile may allow the usage of narrower tires in some circumstances (e.g., 2.1″ tires instead of 2.25″ tires in sandy conditions), and this can more than counteract the increased rim weight.
Some other wheel construction considerations are location of spoke nipples, spoke flange width, and type of spokes (straight pull versus J-bend). Spoke nipples that are accessible with the tire mounted on the wheel are highly desired in comparison to nipples than can only be accessed by removing the tire.
Wider spoke flanges increase lateral wheel stiffness, assuming same spoke count and tension. Increased lateral stiffness improves both out-of-the saddle pedaling efficiency and wheel strength. Spoke flange width is an increasingly improtant consideration for larger wheel diameters, as a 29″ wheel with the same spoke flange width as a 26″ wheel (with all other things equal) will have less lateral stiffness than the 26″ wheel. A similar more suble point here is rear axle spacing, 135mm versus 142mm (i.e., 8-9-10 speed versus 11 speed). Even with the same flange widths (with all other things equal), a wheel with 142mm axle width will have less lateral stiffness than a wheel with 135mm axle width.
Straight pull spoke designs can be more elegant, and can allow higher spoke tension (stronger wheel, or spoke count / weight reduction), but some implementations result in hidden nipples and / or narrower spoke flanges. Straight pull spoke hubs have less wheel design flexibility than conventional J-bend spoke hubs, and hence there is potential for increased cost, and / or utilization of non-optimal hub design.
Resist the temptation of the ultra-light 127tpi race tire for the rear wheel and instead select the 67tpi version with reinforced sidewall (e.g., “Snakeskin” version of Schwalbe Racing Ralph for dry conditions or Rocket Ron for wet conditions). The ultra-light 127 tpi casing is susceptable to sidewall cuts that are not repaired with tire sealant. Also, resist the temptation of ultra-light “reduced knob” tires. Knobs on the back tire are very usefull for climbing the steeper technical terrain, and knobs on the front tire are very helpful for high speed turning and descending technical terrain. In fact, many XC racers are choosing front tires with bigger knobs than the back tires (e.g., Schwalbe Nobby Nic).
“HST” tires and rims should be avoided for racing. HST tires on HST rims are claimed to seal more easily, even without sealant. However, HST tires and rims are significantly heavier than “Tubeless Ready” tires and BST rims, which require sealant AND freshly applied “tubeless tape”.
Tubeless Tire / Wheel Preventative Maintenance
Upon mounting the first tubeless tire wheelset, one begins to notice the benefits immediately, and after a month (or season) without a flat, one concludes these benefits are worth the extra installation efforts (i.e., removing stickers and adhesive from inside the rims with acetone, application of the tubeless tire tape and valve, stretching the tires onto the rims, seating the tires on the rims with compressor equiped with presta valve fitting, sealant application and distribution until tires hold air).
In many cases, the only tire maintenance that was required during the first month (or season) was the addition of sealant that was lost to evaporation and puncture sealing. In order to contnue enjoying the tubeless wheelset benefits, tubeless tires must be removed, replaced (or cleaned and reinstalled) following the complete installation procedure at the begining of each season. It is important to emphasize this includes tape and adhesive removal with acetone, and replacement of the valve. You may notice upon tire removal the presence of tire sealant globs (a.k.a., “Stanimals”, occasionally the size of a golf ball), as this is the action of the tire sealant in the proximity of punctures and it removes the availability of the glob material from sealing any other punctures.
Any time the tubeless tire seal is broken, such as when a tube has to be installed to repair a flat that the sealant could not repair (e.g., sidewall cut or pinch), the replacement or repaired tire must installed following the complete tubeless tire installation procedure.
Warning: hand pumping tubeless flat tire with compact handpump with pump head rigidly attached to pump body can damage the valve stem seal and / or bend / break the valve nipple. Consider handpump with short flexible tube to provide stress relief. Also, it is good idea to carry spare valve stem and nipple removal tool.
Tubed Clincher Alternative
The final point to mention is there is good tubed clincher alternative to tubeless tires that provides equivalent puncture resistance. Continental offers excellent light weight tubes with removable presta valves. Simply mount your clincher (or tubeless) tires with these tubes, and then remove the presta valve and “inject” two ounces of Stans sealant. This is much lighter alternative than puncture resistant tubes pre-loaded with sealant available at bike shops. Note these tubes also need to be replaced every season to maintain puncture resistance.