April 2020 – KneeDeepMoto

Which Tire Tube Size is the Correct Replacement? The correct tire tube sizes for the Africa Twin are 90/90-21 TR4 for the front tire and 150/70-18 TR4 for the rear tire. The front tire tube size is very common however the rear tire size is less common. The best substitution for the rear tire tube is a 140/80-18 tire tube. I will cover additional considerations and my choice for tube replacements below. Africa Twin Tire and Tube Size (Model Years 2016 - 2019) The stock brand and model tires on the 2016-2019 Africa Twin are: Dunlop TrailMax The stock tire and tube size on the 2016-2019 Africa Twin are: FrontRearTire Size90/90 - R21150/70 - R18Tube Size* (metric/inch)90/90-21 TR4 / 2.75-3.00 - 21150/70-18 or 140/80-18 TR4 / 6.00-6.25 - 18*multiple rear tube sizes meet OEM spec. Michelin UHD (4mm) Inner Tubes Africa Twin 90/90-21, 140/80-18 Recommended Heavy-Duty Tire Tube Replacements I chose to use Michelin's Ultra Heavy Duty tubes. These are the correctly matched heavy-duty tire tube sizes commonly available for the Africa Twin motorcycles. While the front tire size is quite common and exact matches can be found using both Imperial and Metric measurements, the rear tire size is less common and is more frequently found in its Imperial Measurement (6.00-6.25 - 18). The exact tube size match for a 150mm tire would be a 5.9 inche-wide tube which are not made. However, a tire tube sized for 5.50" up to 6.25" R18 will fit and seat the rear tire well. A tire tube measuring 140/80-18 or to 5.50 inches also works well for this purpose and is a more commonly available size. I have read reports of other riders using rear tubes measuring as small as 4.00-4.50, however there is greater internal stretch of the tube occurring in these applications and better options are available. In this instance, Michelin does manufacture tubes for both the front and rear tires using metric measurements sized for the Africa Twin so there is not much need to look further unless you are looking for a lighter option. **Note** While tire sizing for any motorcycle wheel is constrained to fairly specific parameters and limited margins of "plus sizing" tires, tire tubes are more flexible in their application. While it is desirable to use the tubes closest to the correct size as possible, tubes are capable of stretching and matching the inside dimensions of many tires close to their size and profile. It is not uncommon for adventure riders to only carry one spare tube for a 21 inch front wheel and use it as a "temporary repair" in an 18 inch rear to limp home. It is worth noting though that while a larger diameter tube can be used on a smaller diameter wheel, a smaller diameter tube cannot be used in a larger diameter wheel. In either case, it is recommended to replace any miss-matched wheels / tubes as soon as possible. Africa Twin Tires and Tubes Both trims of the Honda Africa Twin (model years 2016-2019) run Tube-Type (TT) tires. For anyone who is unfamiliar with this tire orientation, it simply means that the tires must have an inner-tube inflated inside of the tire to hold shape and pressure. In contrast, Tubeless tires do not need a tube and rely on a tight seal between the bead of the rim and the tire to hold pressure. While the use of tube-type tire orientations is still comon on most dirt / off-road focused motorcycles, tubes are all but extinct on road focused machines. The latter opting for "tubeless" tires (TL) as standard kit. Both tire configurations still have their place in motorcycle design and application with pros and cons on each side however general trends show the move towards tubeless tires in the dual sports categories becoming increasingly popular. Case in Point, Honda's recent update of the Africa Twin for 2020 has both models switching to tubeless tires. Tube Thickness Tire tubes come in various thicknesses usually ranging between 2mm and 4mm. The tube's thickness is commonly described by retailers as Standard, Heavy, and / or Ultra Heavy Duty Tire tubes (2mm, 3mm, and 4mm respectively). However there is no actual rating system for tire tube thickness or labeling standards so it is important to confirm actual tube thickness rather than rely strictly on the manufacturer's labeling. Michelin Ultra Heavy Duty Tube (4mm Thickness) Conventional thinking might lead people to assume that the thicker the tube is always the better option but this not always the case. While heavy duty tubes defiantly have their advantages (resistance to pinch flats) in off road riding when particularly low pressures are used, thinner and lighter standard tubes may deliver better on-road performance. With each increment a tire tube's thickness increases, not only does it become heavier (which translates to more unsprung weight in the wheels) but also more expensive and more prone to holding heat. You should consider your riding application and choose the weight of the your replacement tire tubes accordingly. Pinch Flats For anyone agonizing over which tire tube replacement to select, it is likely that the thought of "pinch-flats" has crossed your mind. A Pinch-flat is a puncture in the tire tube that usually results from running low air pressures over sharp-edged terrain. Effectively, it is when the tire contacts the edge of a rock or tree root under low pressure and the tube inside the tire gets crushed (or pinched) between the collapsing sidewall of the tire and the rim. This causes a weak spot or puncture in the tube to develope that will eventually let the air completely out fo the tire. "Heavy" tire tubes can resist this phenomenon better than lighter tubes at low air pressures and are thus popular for off-road riding applications. They are however more expensive and are usually not provided from the factory. If you are new to working with tube-type tires and / or are purchasing your first replacement tubes after the stock tubes have worn out or got a puncture, you may have only heard of "pinch-flats". If you are an experienced rider or someone who rides aggressively off road it is likely you have experienced one before. In either case, they are an unfortunate reality of off-road riding and something that riders running tube-type tires have to deal with.