Ask a Mechanic | Sealing Tubeless Compatible Tires & Internally Geared Hub Compatibility







Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at In this installment Daniel reviews questions concerning the use of tubeless tire sealant in “tubeless compatible” tires and how to convert a fixie or standard singlespeed into a geared bike using an internally geared hub.


I just installed a pair of brand new Continental X-King 29er tires on my UST Easton Haven 29er wheels and I am getting a lot of sealant leaking out of the sidewalls and around the bead. Is this normal? Do I have defective tires? From: John


There is no need to weep when your tires do the same, John. This is how non-UST “tubeless compatible” Continental RTR tires are designed to work. The sealant seals the pores of the thin, lightweight “tubeless compatible” casing that would otherwise require a heavy extra layer of rubber to be air tight.

Stan’s No Tubes valves have removeable valve cores that make sealant refreshes a snap.

UST casings are made to a universal tubeless standard that requires an additional layer of rubber that extends from bead to bead so that the tire can be theoretically used without sealant. This additional rubber adds weight and stiffens the tire, but it can also serve as an effective layer of armor to protect the sidewall from cuts should you live in an area with sharp rocks or flora. These tires do not weep sealant from the sidewalls. If they are used with sealant, something I highly recommend, they will leak a bit at the bead until the sealant can properly dry. Even with a true UST tire and rim, without sealant the combination will likely leak down to an unridable air pressure within 24 hours. If you want a stronger, stiffer tire that doesn’t weep sealant, then UST is the way to go. We have a few guys here at Art’s that won’t run anything else in the mile-long rock gardens that are common in our area.

Just refill the sealant in your RTR tires every 2-3 months and you will be good to go. I like to use valve stems with removeable cores so that I can install the sealant without removing the tire from the rim. Just use one of the Stan’s 2oz bottles or a syringe to pump the sealant into the tires.

In short, I give your current setup my personal “seal” of approval.

Shimano’s Alfine 8 hub is a marvel of engineering and it extremely reliable


I like the simplicity and look of fixies, but I want more than one gear. Can I put an internally geared hub on a fixie to convert it into a townie bike for hauling heavy loads or pulling a trailer uphill? From: Timothy


Fixing to fix your fixie, Tim? Most fixies have 120mm rear end spacing, which limits you to only 3-speed hubs such as the Shimano Nexus 3. These hubs are good little workhorses and come equipped with a coaster brake so you can keep the clean fixie look. Just lace one to a 36 hole rim of your choice, or buy a prebuilt wheel, with this hub and you will be ready to roll.

However, if you really want to handle a heavy cargo then you will need a wider range of gears, a front brake, and maybe a stronger rear brake too. Shimano’s Alfine 8 and Alfine 11hubs are outstanding pieces of engineering and we have them on closeout making them more affordable than ever. The problem is that internally geared hubs with more than 3 gears generally require a frame with 130 or 135mm rear spacing. Most bikes that have this spacing have vertical dropouts and no way to tension the chain short of using a single-speed chain tensioner like a Surly Singulator. You could spread the rear end of your 120mm spaced fixie frame to accommodate the wider Alfine hub, but this usually results in misalignment. Even so, if you want to take the risk and your frame is steel, then go for it. Just remember that if you go too far you could end up destroying your frame, so take it easy.

Shimano’s Alfine 11 hub packs in a full range of mountain bike gears and is robust enough to handle off road applications.

Your best bet is to purchase a single speed mountain bike and then rebuild the rear wheel with an Alfine hub. The spacing will be right at 135mm and you will have the option of disc brakes which will better handle the added weight of cargo.


Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly University. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.