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Today I went through this situation. Rims are Vzan Action with Formula Hub 36 holes.

My rear tire was leaking. A guy patched up the tube and the problem persisted. I went to the bike shop and asked to check the patch, and as done, I went to a gas station, where I usually inflate it (only this year more than 2000km, most of the inflations were done at this station), and after inserting 65 psi and the valve, the tube EXPLODED.

Out of luck it was just that, but I bet everyone heard the sound 2 miles away. The tire was apparently no damaged. I returned to the shop with the intention of changing the tube (I already had another one, I wanted to mend that one to make it last longer), but on the way I saw the real damage. The side of the rim was EXPOSED, completely disabling the wheel.

At the bike shop, they said it was my fault for inflating in a gas station, and they did not offer me an apology, or even a discount for the assembly of a new wheel.

Soon I visited another bicycle shop where the owner informed me that the problem was that the tube was folded. And he also noticed that the side of the tire was damaged and that I would have to discard it, or it would compromise the tube in the future.

I would like some opinions from you. Was it my fault, afterall? If so, how can I check if its safe to ride?

I really like this tire and I did not want to get rid of it like that. It is being used since April. Can I still use it? Please check the images below.

Can I use the spokes of the old wheel? The hubs could, and should, be used, right? Or should I go ahead and buy a pair of new wheels?

Here are some images to illustrate.

Side twisted with the explosion Side twisted with the explosion

Side twisted with explosion 2 Side twisted with explosion 2

Tire on random point

Tire on random point

Region of the tire that the rim exploded Region of the tire that the rim exploded

Update: analyzing some Youtube videos, I think the explosion happened from excessive stress on the rims. Plus, it wasn't completely true, and brakes pads were touching them at some points.

I think that brake pads were bad positioned in the moment, or wore the wheels, or made then weaker in certain spots in the long run, making a crack or making the tube pop and explode in that direction.

I'm almost surely buying a new pair of wheels, which will cost me basically the same price of a single one in the bike shops that I went.

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    I don’t understand. Did the shop not inflate the tube to check the patch? Did you cycle to the gas station? Was the tire flat when you got to the gas station? How is the rim damaged? What does exposed mean? Are the rims worn and weakened? Photos aren’t super clear, maybe take some in daylight and insert them into the answer too
    – Swifty
    Commented Aug 7, 2018 at 22:03
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    Feel the rim, is it flat and thick on each face, or are they thinner and concave?
    – Swifty
    Commented Aug 7, 2018 at 22:11
  • Wheel trueness has virtually no effect on wear from brakes: The wear happens due to the large forces that you apply during braking, the small forces that result from a badly centered brake or untrue wheel are simply not enough to produce relevant wear.
    – cmaster - reinstate monica
    Commented Aug 10, 2018 at 6:57

5 Answers 5

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I don't know what kind of air pump you were using at the gas station. If it was a manual one with just a pressure gauge attached, you can usually use them if you are careful enough.

Automatic air pumps, however, usually have the habit of using this three step algorithm: 1) open the valve to fill some air for a fixed amount of time, 2) measure the effect, 3) correct the error. Problem is, that step 1 is adapted for car tires with their immense volume, so it will over-inflate the tire if the pre-pressure from the pump is high enough. Typical pre-pressure from pumps seems to be around 100psi (my experience), but it can be anything. If your tube has a dunlop valve, that extra pressure will remain in the tire. So, don't use automatic pumps, especially not with dunlop valves.

That said, your rim has a maximum force that it can withstand. And that's where it gets a bit complicated:

  • The maximum force that the rim can withstand reduces over time if you are using a rim brake on that rim. It's not just the brake pads that wear away, it's also the rim. Give it enough wear, and it will even explode at its originally rated pressure. I'm not sure whether that's the case with your rim, though.

  • The force the tire's bead exerts on the rim depends on both the pressure and the width of the tire. The wider the tire, the more the tire will tear on the rim's edge. Your tire seems to be of the wider kind, so, even if the rim could bear a slim 100psi tire, 100psi with your wide tire may have been too much for it.

  • The force on the rim is independent of the tube. The tube is not designed to withstand any forces, the only force that it exerts is the pressure of the air. Whether the tube is folded or not does not change this pressure. So, the opinion of the second bike shop seems to be wrong in this regard.

So, what does that mean for repairing your tire? Well, obviously, you need a new rim.

Looking at the damages to the rubber covering the bead, I would have trouble trusting the bead to remain seated: I would think that the rubber between the bead and the rim does help keeping the bead in place. Without that rubber, I would fear that the bead might have an easier time slipping over the rim. So, I would replace the tire if I were you.

Regarding replacing the rim/tire/tube vs. just replacing the entire wheel, it's a lot of work to rebuild a wheel. If you don't do that yourself, buying a new wheel should be cheaper unless you have a sufficiently expensive hub like an internal gear hub to set off the expenses for work time.

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  • It was an automatic pump. I've a Formula hub, which runs a 7-speed cassette. I was thinking about using the spokes of the old wheel. But I don't know if I can trust them...
    –  deLiz
    Commented Aug 7, 2018 at 23:11
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    The easy way to replace a rim is to tape new one to it and move spokes over one by one. This reuses the spokes. It's not difficult to do but most people here are needlessly afraid of anything that has to do with wheel building.
    – ojs
    Commented Aug 8, 2018 at 5:09
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    @ojs Well, I'm not afraid of wheel building as I'm always building my wheels myself. But I know how much work it is to get the wheel true and an even tension into the spokes. So I know that, were I to look at this from an economical perspective, I'm wasting a ton of time/money each time I build a wheel instead of just buying a new one.
    – cmaster - reinstate monica
    Commented Aug 8, 2018 at 7:26
  • In other comment it's said that the rebuild is 20 Usd with old spokes. I doubt new wheels come cheaper than that.
    – ojs
    Commented Aug 8, 2018 at 10:34
  • @ojs Prices vary greatly by country. In mine, I would not be able to get a rebuild for anything less than 50$. At least not by anyone who's proficient enough to produce a good wheel. Human labor is simply more expensive over here.
    – cmaster - reinstate monica
    Commented Aug 8, 2018 at 13:27
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It's not 100% clear from your pictures and description, but it appears that the rim failed at the outer radius of the "working" portion of the brake surface. This is consistent with failure due to rim wear, a relatively rare condition only because few bikes are used enough to wear out the rims.

How many miles do you have on the bike? Have the brakes been professionally maintained, or did you (or a buddy) do all the adjustment. Poorly adjusted brakes can exacerbate the problem, as can wearing the pads all the way down to the metal.

Inflating with a gas station hose is not the wisest thing to do, but is unlikely to have caused the failure. Unless the rim is already compromised, the tire will fail from overpressure far sooner than the rim.

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  • As can debris embedded in the brake pads
    – Swifty
    Commented Aug 7, 2018 at 22:21
  • I've at least 1500 miles on them. But the bike was bought in 2008 or 2009, I think. I can't assure the maintenance or usage of the previous owner, but as I received it, it was like new, no signs of massive usage, just regular
    –  deLiz
    Commented Aug 7, 2018 at 23:08
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Inflating the tire with a powered compressor meant for cars is not a great idea. I would not trust the pressure gauge to be accurate and they can deliver more pressure than a bike tire (or rim) can withstand. Use a pump designed for bicycles in future.

You cannot pin any blame on the first bike shop, nor do they owe you an apology. You asked then to check the patch on the tube and they did that. A leaking patch can't blow up your wheel.

Re-using the hub and spokes is probably not worth it. You would have to pay a wheel builder to build a new wheel re-using spokes, hub and a new rim. It's more cost effective to just buy a whole new pre-built wheel.

The tires may be OK, as the carcass and bead seem to be intact, just the rubber outer layer seems to be damaged. However, I personally would not risk it and I'd replace the tire.

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  • Thank you. Well, replace the hub will make it costly. I was planning to use it anyhow. They offered around US$30 to make a new wheel using my old hub. I can save around US$10 using the old spokes, I just don’t know if they’re safe. What do you think?
    –  deLiz
    Commented Aug 7, 2018 at 21:26
  • Depends how many miles you have done and if you have abused the wheel. If you have not broken any spokes or had to have the wheel trued the should be fine. If you were happy to ride on them before the run was damaged, you should be happy with them in a rebuilt wheel.
    – Argenti Apparatus
    Commented Aug 7, 2018 at 21:32
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    “Inflating the tire with a powered compressor meant for cars is not a great idea. I would not trust the pressure gauge to be accurate and they can deliver more pressure than a bike tire (or rim) can withstand.” I’d argue that those compressors are actually very accurate. Cars need pressures around 2bar. An inaccuracy of say 0.2bar would make a huge difference there but wouldn’t matter for a bicycle. I think the compressors also get calibrated regularly.
    – Michael
    Commented Aug 8, 2018 at 8:26
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    @Michael I don’t know how accurate those compressors are. You make a good argument that they should be fairly accurate at around 2 bar but that doesn’t say how accurate they are at, say, 6 bar.
    – David Richerby
    Commented Aug 8, 2018 at 9:06
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    @Michael: One supposed danger I've heard of is that the flow-rate from a car pump can fill a bike tire very fast, especially a narrow road tire, and pop your tube before you realize you've gone over pressure. I've had no problem on the few occasions when I filled my MTB tires at the pump to ~60 psi, though. MTB tires having a bit more volume. If it's a gauge that only shows the pressure when you stop filling, do that frequently to get a feel for the fill rate.
    – Peter Cordes
    Commented Aug 8, 2018 at 9:10
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Most of the answer seem to be based on the idea that to replace a rim, you have to completely disassemble the wheel and build a new one from used parts. This is not exactly true: you can replace the rim by taping a new one to the side of the old one and then moving spokes over one by one. This is far less work than lacing a wheel from scratch and the spokes remain in the same position where they have already settled, minimizing the risk of additional metal fatigue.

In a comment it was mentioned that the shop offers a discount for using the old spokes. It sounds like they are planning to do this instead of rebuilding the wheel from scratch. I would recommend taking the offer.

In my opinion the tire is gone. Not only the bead is damaged, but there are also visible cracks on the sidewalls. This kind of damage is often caused by too low pressure, and hitting an object with rim may have damaged it, too.

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  • Are you implicitly ok-ing the spokes for re-use? OP might value quick justification on why they are (or aren’t) safe
    – Swifty
    Commented Aug 9, 2018 at 17:42
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    Yes, if the swap is done right. If the wheel has already been ridden for several thousand kilometers without enough breakages to complain about, they are probably ok quality and shouldn't just start breaking now. I know this is a small sample, but I have swapped the rim on one wheel a few years ago and it hasn't shown any signs of problems.
    – ojs
    Commented Aug 9, 2018 at 18:23
  • Agree, I think it’s perfectly common thing to do but didn’t want to put words in your mouth. So to speak.
    – Swifty
    Commented Aug 9, 2018 at 20:09
  • Oops, should have been "done right and the spokes decent quality".
    – ojs
    Commented Aug 9, 2018 at 20:53
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    Yep, this style of rim replacement used to be commonplace, before pre-built wheels became so cheap. It's not a "winner" for a cheap wheel, but for one with an expensive (or rare) hub it's a worthwhile approach. The labor involved is much less than a complete rebuild.
    – Daniel R Hicks
    Commented Aug 9, 2018 at 21:55
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Tire appears to me to be completely gone. It is hard to tell about the rim, in the first pic, it appears to be a total lose. I have a hard time imagining a rim failing, though. Can you add a pic of the rim without tire, in the area of damage?

Check the brake pad setup, make sure they are not touching the tire. If they do, they will "score" the tire and cause it to fail.

Rebuilding the wheel is a good choice, I would recommend keeping the rear hub. It has the cog set you want, all the spacing for the frame, derailleurs, etc are correct already. You can reuse the spokes, but I recommend against it. They tend to break after being in wheel, then de-tentioned, and re-stressed. ( a wheel does not support it's load thru compression, but reduction in tension ).

Bike shops: at third hand, it is hard to tell, but if you are relating things well, I am not comfortable with either ( 10 years in a bike shop in my early years.... ) I have never seen a rim fail from tire pressure in all that time. Not saying it cant happen, but the tire / tire bead is the weak spot in all this.

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