fat tires - undulating, uneven, whatever you call that

[weisan]

what's the deal especially with fatter tires (35mm and up) when installed on a wheel, create this undulating, uneven, whatever you want to call it, out of roundness. You can see it easily when you lift the wheel off the ground and spin it a couple of rounds. What's up with that? Does it transfer over to the ride? At first I thought it's the beads not sitting properly on the rim bed and try to adjust during installation but in the end, it's still doing that thing. What's your take on it?

[oldpotatoe]

https://www.youtube.com/watch?v=kixcPuk6p_M

[thwart]

Originally Posted by weisan

what's the deal especially with fatter tires (35mm and up) when installed on a wheel, create this undulating, uneven, whatever you want to call it, out of roundness. You can see it easily when you lift the wheel off the ground and spin it a couple of rounds. What's up with that? Does it transfer over to the ride? At first I thought it's the beads not sitting properly on the rim bed and try to adjust during installation but in the end, it's still doing that thing. What's your take on it?

I've had the same problem, and found that manually trying to move the bead a bit and seat it when inflated to normal pressure (~ 40-60 psi) just wasn't effective. Worst case I remember was a set of Jack Brown green tires.

Inflating to the max pressure on the sidewall (typically ~ 90 psi) has worked well for me. Once the tire is well seated and no longer out of round, I deflate to riding pressure.

FWIW, type of rim strip hasn't seemed to matter much here... cotton (Velox) or DT tubeless tape.

[AngryScientist]

common problem with fat tires, especially those with very supple sidewalls.

i have found that on initial install, if i use a few drops of dish soap on the tire beads, they pop into place a little easier.

these instructions from compass are helpful also:

https://www.compasscycle.com/wp-cont...ns_2015_07.pdf

[weisan]

Thank you, that was helpful.

[AngryScientist]

weisan - are you using tubes in the tires that are giving you trouble?

i dont use any tires tubeless at the moment, but this does sound like it's a problem more common in using nice supple tires with tubes. in any event, i've generally been able to get the tires to run straignt and true with a little fidgeting, and they usually mount the second time easier than the first.

[NHAero]

I had this issue with Velocity Synergy rims. Same 37mm tires on better rims, issue solved. Jan Heine has a blog post addressing rims with poor bead seat characteristics.

[weisan]

Yes. Tubes.

Specifically, 35 mm Panaracer pasela TG.
H+ Son Archetype

[dddd]

I was having this problem with some wide off-road tires last year, they were tubeless tires on standard rims, it always took bead lubrication plus inflation past the psi limit to seat them. I went back to non-tubeless tires so I could get them mounted straight after any mid-ride puncture repairs, since my pocket pump would take all year to achieve such high pressure.
And I've had the same problem with standard wire-bead Continental tires on a couple of different vintage-era rims of completely different make, style and width. In those cases I changed tire brand and got by ok from that point forward.

[Vientomas]

I have the same issue with MTB tires with tubes. Inflating to max recommened pressure usually seats the tire properly. Then reduce to desired pressure.