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I just got 2 new Panaracer Gravelking SK tires and mounted them tubeless on WTB i21 rims with the correct width rim tape from WTB. I inflated them to 60psi to set the bead and the rear blew off the rim before even taking it off the stand.

The rim is now way out of true. In fact, I think it has to be replaced now.

After this happened, I trued the rear wheel as best as I could and re-installed the rear at about 40psi. I went for a test ride and 2 minutes in, the front blows! It was between 50-60psi at the time. And now the front wheel is severely out of true as well.

  1. Is that normal for a rim to be ruined from a blowout?

I realize that I should not have inflated them to their max rated psi (60psi max for tubeless and 75psi for tubes). But, in my experience, I have never had a tire blow out right at the max psi. Most tires can go way beyond that for a short period, especially for just setting the bead.

  1. Is this rim/tire combo just incompatible?

  2. Should I just run tubes with this combo? (I have trust issues now).

Update (8/8/2022)

Ok, so 60 psi is a little insane to ride on for a gravel tire. I get that now. I talked with WTB about this and they see no reason the tire should have blown off. They did give me crash replacement pricing for new rims. I have since rebuilt the rear wheel with the new rim and I am now running the same tires on the old front wheel and the new rear wheel. I will be rebuilding the front wheel soon, once some more parts arrive. I have been running this setup for about a month now at 35-40 psi with absolutely no issues.

Here is my theory of what happened. I think my floor pump gauge was starting to fail when I originally pumped up the tires and it was reading much lower psi than it actually was. I think this because just recently, the gauge completely failed and reads all over the place. Who knows how high I actually pumped them up to when they blew.

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    what size and model of the Gravelking SK did you use?
    – Andy P
    Jun 17, 2022 at 20:43
  • Hi, welcome to bicycles! The correct size tire shouldn't blow off the rim at the rated pressure, not even max pressure. Even running them with tubes won't fix that because the pressure on the bead will be practically the same. The first order of business should be to make sure you got the right size tires.
    – DavidW
    Jun 17, 2022 at 20:47
  • @AndyP I used the Tubeless Compatible Clincher
    – Geo242
    Jun 20, 2022 at 21:07
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    What pressure are the rims rated to? Perhaps their limit is lower than the tire's, although really there should be a margin of safety.
    – MaplePanda
    Jun 21, 2022 at 1:39
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    There's a good chance that you did not have the tires properly seated on the rims.
    – Daniel R Hicks
    Jun 21, 2022 at 16:46

2 Answers 2

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I'm afraid there might be no good answer that is going to put your mind at ease and guide you what to do next, but i'll have a go based on the information we have available.

From the information you have given, you didn't do anything wrong. 60psi in a 38c tyre is certainly not a crazy amount on a hooked rim, and from looking at the WTB website there is no maximum pressure listed for the rim. Your procedure of inflating to the max pressure to seat the beads was certainly a very normal thing to do a few years back when tubeless was new and products weren't designed quite so well.

  1. I wouldn't say its normal, but its certainly not unheard of for a blowout to severely damage a rim. In addition to re-trueing the wheel i'd also very carefully inspect the rim hook area for signs of damage before attempting to reuse the wheel.
  2. It's extremely unlikely that this rim/tyre combination is incompatible.
  3. You are wise to have trust issues. I would be trying to investigate more into what caused this issue before using this combination again.

One area i would investigate would be the pressure gauge on your pump, it wouldn't be the first time i've heard of a gauge being 10-20psi out. Accidental overinflation would explain what is otherwise quite a strange case.

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  • 60 PSI on a gravel bike with 38C??? I normally ride around 35, sometimes it drops to 20 when I forget to inflate (a non-TLR rim). Why would one do this to themselves? It must ride almost like a solid tyre.
    – Vladimir F Героям слава
    Jun 23, 2022 at 8:33
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    @VladimirFГероямслава 60PSI isn't intended to ride on, its intended to get beads seated, you let it down again afterwards. But in terms of holding pressure and not blowing off the rim 60psi is quite reasonable
    – Andy P
    Jun 23, 2022 at 8:39
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My experiences with Panaracer tyres and WTB rims have been at both ends of the spectrum.

I first set up my Gravelking SK 43mm on WTB KOM Light i23mm rims at 45PSI. I left them for two days with no issues and then set them at 35PSI for riding. About 10km in the first ride the rear blew off both beads while stopped at a traffic light. I used a tube until I could set it up tubeless again. Around ~40km of tubeless riding later it blew off both beads from the rear again while doing 30km/h, which resulted in trashing the rim on the road. I replaced it with a Spank Flare 24 rim.

I sent a report to Panaracer stating that it was operating within pressure guidelines, so they sent me a replacement tyre. I was out of pocket for the rim.

I've since run several sets of Gravelking SK 43mm and a set of Gravelking+ slick 38mm on the original WTB i23 front rim and the replacement Spank rear rim for thousands of kilometers without issues. I've used the same pumps and gauges all the way through.

At the time of my tyre's blowout I read of several other reports of blowouts with the same tyre/rim combo. It seems to mostly happen on the rear.

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