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When braking (with any kind of brakes) the tire is subjected to friction against the road. If by mistake a clincher tire has grease all around the two bead sides, it could potentially spin while the rim has locked. Is that right?

We anyway never add any grease to rim, rim strip, inner tube, or tire, but should we ensure that no spinning will occur by adding a hint of glue anywhere? Are the bead friction and a properly inflated inner tube sufficient to avoid slippage?

Mainly I'd like to know (that's my "one question" here; feel free to ignore the many side questions):

  1. Should the rim strip be glued to the rim? I expected rim strips to be sold with paper that gets pealed to reveal self adhesive on one side against the bare rim, but they are fitted to the wheel (rim tape: 700C x 18mm), and without any gluing only the tension will keep them in place. Even though we are not talking here about tubular rims, how do we avoid that the valve loses orthogonality to the rim after many rounds of braking—short of gluing? It would be nice if all rim strips have a self adhesive, no?

    I'm also curious about the logic behind the conventional wisdom of adding talc powder to the inner tube to ensure it doesn't stick.

  2. Could talc powder make the tire spin during (hard) braking if an excess of talc powder makes the tire beads slippery against the rim?

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  • Note that for the question you cite about the valve losing orthogonality, that is a tubular tire in question. The only thing holding that tire onto its rim is the glue. With a clincher, you have the air pressure doing that.
    – MaplePanda
    Commented Apr 17, 2022 at 1:06

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I have seen a tiny amount of tire creep on kids bikes, enough so that the valve stem is moved slightly away from perpendicular to the rim. But these are poorly maintained bikes with tires that are always under-inflated.

In order to reduce friction between the rim and tire enough for the tire to spin freely against the rim (especially when inflated) you would need to have an amazing lubricant that I will speculate does not exist. A dab of grease would compromise braking (as Criggie says) but would not allow free spinning.

Gluing the rim to the tire would be a solution to a nonexistent problem. Likewise gluing the rim tape to the rim.

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  • The spoke holes are not chamfered. They are just drilled. That’s a good thing, because even without glue, the rim tape has no chance of creeping sideways (because, as Criggie mentions, inner tube inflation pushes the rim tape into the holes—fixing its location). Any sideways motion would be particularly problematic because the (nonchamfered) holes have a sharp edge waiting to cut the inner tube.
    – Sam7919
    Commented Apr 17, 2022 at 15:48
  • The summary appears to be: (We're not addressing tubular here) 1- Rim tapes sold as a loop do not arrive with adhesive and do not require glue; they are meant for use with an inner tube. 2- Rim tapes sold as rolls to be cut to measure will have an adhesive; they are meant for tubeless tires. (and 3- Loop+adhesive is overkill) Is this about right?
    – Sam7919
    Commented Apr 17, 2022 at 15:48
  • There is rim tape for tubed wheels that is sold on a roll and is adhesive backed. I've used some from Schwalbe and it is great—thick and stiff, very helpful when you're dealing with a spoke on the edge of pushing through. But it is not airtight, which is the defining feature of rim tape for tubeless wheels.
    – Adam Rice
    Commented Apr 17, 2022 at 17:07
  • Cool... I'm convinced it's a nonexistent problem.. Next point (beyond the original question): Consider this. The cyclist needs to slam the brakes on a wheel. As luck would have it, the valve goes right through the 6-o'clock position during the heavy braking. Everything is held together perfectly by friction and 90-100 psi. Nevertheless, a small residue of the shearing force makes its way to the tube-valve junction, pushing it by 1/10 mm into the valve hole. The rim strip does not cover the valve hole, and the tube is cut at the worst possible location in terms of repairing it. Question is:
    – Sam7919
    Commented Apr 17, 2022 at 19:50
  • Shouldn't the rubber part at the base of the valve be sheathed with some kind of protection?
    – Sam7919
    Commented Apr 17, 2022 at 19:51
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The static coefficient of friction between rubber and metals appears to hover around the 0.80 mark, so I'll just use that as an approximation. Let's assume the worst-case scenario, where the rim has no bead hook effect, and it is of the hookless type with low-profile rim sidewalls. With a 622mm bead seat diameter tire, I calculate a contact area of 2 * pi * (316^2-311^2) = 19700mm^2 (times two because the rim has two sidewalls), which is equivalent to around 30.5 square inches. Assuming a low-pressure mountain bike tire at 25psi, I get a nominal normal force of around 760 pounds-force, which after factoring in our coefficient of friction gets us around 610 pounds-force of frictional capacity.

Let's see how much braking force we need. Let's start at a nice 10m/s speed with a 100kg rider and bicycle. That gives us 0.5 * 100 * 10^2 = 5000J of kinetic energy. Now, let's perform an emergency stop over 5 meters distance. Using the definition of work as force * distance, we get an average force of 1000N, which is equivalent to around 225 pounds-force. Evidently, an unlubricated tire is safe from sliding around on the rim.

You'd therefore need the coefficient of friction to be around 0.30 or so in order for the braking force to exceed the tire holding force, which is not unachievably low. You'd have to specially prepare the wheel for that: trimming the bead to get a looser fit, and using top-quality lubricants. However, of course, I disregarded the contribution of the bead hook/bead seat in my calculations, and I assumed all the braking was being performed by one wheel, so you may very well need to work harder than that. Even without any air inside, locked-in tires are not rotatable by hand.

As a user, I wouldn't want to deal with adhesive rim strips. Regular rim strips just snap on nice and good...imagine having to deal with this contorted, self-adhesive toroidal mess. I'd rather just use tubeless tape in that case.

Do note that lubricants such as dish soap are regularly used to aid the installation of difficult tires, yet reports of tire slippage have not skyrocketed with that practice in place. I doubt talc powder is any more effective at reducing friction.

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  • Dish soap goes tacky when it tries, so it becomes less of a lubricant and leans more toward a "friction enhancer" or the "glue" that OP mentioned.
    – Criggie ♦
    Commented Apr 17, 2022 at 10:31
  • @Criggie I think you'd need to know the shear strength of dried dish soap to determine that -- grease is also tacky, but it's too weak to act as a useful adhesive evidently.
    – MaplePanda
    Commented Apr 17, 2022 at 20:30
  • yeah - grease is oil based and takes decades to dry out. Dish soap will loose its water in days and become tacky.
    – Criggie ♦
    Commented Apr 18, 2022 at 1:09
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Grease in/on a tyre would be a bad thing to do. It will definitely limit friction in places you want friction, and risks degrading the rubbers over time as well as contaminating any rim brake surface.

Normally the friction and pressure from a tube will press the rim tape into the spoke heads/holes and the tyre's bead into the hooks. That is plenty sufficient to stop the tyre moving on the rim.

If your air pressure is low enough that the tyre can move, you're basically rolling on the rim already and asking for pinch flats.

You might be conflating normal tubed/clinched tyres with either of:

  • tubular tyres (which are literally glued or taped to the rim)
  • tubeless tape (where there is no tube, but the tyre and the rimtape work together to make a secure bead lock)

Talc was historically used in tube manufacturing, to stop the new surfaces of a tube from sticking together. If you cut open an old tube it may even have some talc on the inside. Talc is not a lubricant, it simply prevents the tacky rubber from sticking to itself.

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    Spot on. The only thing I would add is that the talc also acts as a release compound from its mold, if I’m remembering my Jobst Brandt canonical FAQ answers correctly.
    – Paul H
    Commented Apr 16, 2022 at 14:26
  • So rim tape that is merely labeled "adhesive" is insufficient for use in tubeless tires. Rim tape must specifically be labeled "adhesive" for tubeless, and in that case it will also use an adhesive. Is that right?
    – Sam7919
    Commented Apr 17, 2022 at 15:54
  • I suspected that with all the goo (i.e. sealant) inside a tubeless tire has little room for budging (and I'm not concerned with tubular in the present question).
    – Sam7919
    Commented Apr 17, 2022 at 15:55
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Some rim strips are glued to the rim, specifically Velox. But with correct tire pressure, a rim strip and a tire will not move. Most new bikes have rim strips which are not glued and they won't move. Tires do not move at all, otherwise, the clincher design would be a failure.

Talc is not slippery enough to make a difference, and it was likely over caution with latex tubes which inspired the use of talc.

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This is a quick guide to the rim tapes on the market for both clinchers and tubeless tires (but not tubular tires). It summarizes the points mentioned by Adam Rice and Criggie.

summary or rim tape styles

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