Telly

Hello everyone,

Although by all accounts I'm extremely lucky with flats... 4,500 km with 0 punctures, I have had to change three inner tubes because of failure around the base of the valve. Today's ride ended up with a spectacular blowout which emptied the front tubes contents within seconds; this on a smooth paved road with the bike relatively unladen and the temperature in the low 30's(C).

This is the second Michelin ProtekMax tube which has failed at the "weld" around the presta valve stem, albeit the tube did have over 1,000 km on it, while the previous tube lasted around 750 km, and leaked slowly in the same spot. The rims are new Mavic A719s which have been looked over for burs and shavings (absolutely smooth), with a high pressure Schwalbe rim-tape in new condition with less than 500 km on it. Before the ProtekMax tubes, I had a Continental tube with around 2,000 km fail in the exact same spot (different rims).

I'm pretty sure that I installed the tubes correctly (they probably wouldn't have lasted if I didn't), and I take good care not to damage the presta valves or put too much pressure on them, and always use a floor pump to check and periodically top-up.

Ok, here's my two questions:

a. is there anything I should look out for which could cause this type of damage?

b. since the ProtekMax are heavy and my Maxxis Overdrive's seem to offer more than adequate puncture protection, can you suggest good quality inner tubes that are not prone to failing around the valve stem?


Thanks in advance!

Sixty Fiver

We had a blowout yesterday... figure the tube had 5000 miles on it and was pretty generic and had been filled with puncture sealant. as it is my wife's bike and a three speed IGH the less chance of flats the better it is.

Replaced that with a Schwalbe tube which I consider to be some of the best out there (but they are pricey)... they make a beautiful Schrader tube with the classic threaded stem and locknut.

Their Presta tubes are equally great.

cny-bikeman

A true blowout happens much faster than a few seconds, is indicated by either a starburst or long slit, and only occurs when a portion of the tube entirely escapes the tire. What you describe is a sudden failure, due most likely to one of two causes:

1. There is a problem at the area of the valve such that the stem cannot or is difficult to seat properly in the rim, and the tube has to stretch much more in that area because the base of the valve stem is above the rim. Avoid using tubes with excessively heavy reinforcement on narrow rim/tire combos and make sure you push the valve up into the tire, seat the tire into the rim, and then pull the valve stem firmly into the rim.

2. The tire has been ridden underinflated and the tire and tube have migrated, so that one side of the tube stretched out until it failed. I prefer to do without valve stem nuts but if you do use one make sure you keep the tires inflated regularly to prevent creep.

Some tubes may fail somewhat before others from the above problems, or be slightly more likely to have a problem but the base cause is not the tube.

Looigi

Something is wrong somewhere, if nothing other than a defective tube, assuming the tube is the correct size for the tire. My Mich Aircomp ultralight tubes have over 12k miles on them and have multiple patches from punctures, but structurally are fine. I figure they'll go at least another 12k miles. They won't be ultralight anymore with all the patches on them. The only time I ever got a blowout was long ago when I pinched the tube under the tire bead.

One possibility is that there's too much thickness of rubber around the base of the valve stem so it doesn't fit flush against the inside of the rim. When this happens the tube adjacent to the base of the stem can protrude back under the material around the base of the stem causing it to tear or blow out.

edit. I see CNY posted the same at the same time I did.

jsharr

I was a having trouble with tube failures on the front of my mtb, also around the valve hole / stem area. I ended up replacing the rim tape. Used a rim strip from Performanace for the first time. No flats for the last few weeks.

Telly

The rims are machined for Schraeder valves but were given with inserts for presta valves which of course were used. Also since last year where I moved and have the ability to bring the bike into my apartment, I've been adamant about checking the tire pressure at least every two days and have never ridden the bike with under-inflated tires/tubes.

I'll try Sixty-fiver's suggested Schwalbe tubes since the ProtekMax tubes are very heavy (280gr) and the sealant fluid inside can be felt, especially if the outside temperature is low. Do you have any specific Schwalbe tube I should use (my rims are 19mm, and tires are 622-42/700c x 40)?


Edit: The rim tape is by Schwalbe, and is the absolute best quality I could find... I think it's called Super HP and is 22mm and sits very nicely in the A719. I remember the LBS pointing out that it was much better than what was found locally (bought from Rose GmBH).

ksisler

[Partial QUOTE=Telly;15594641]Hello everyone, although by all accounts I'm extremely lucky with flats... 4,500 km with 0 punctures, I have had to change three inner tubes because of failure around the base of the valve. Today's ride ended up with a spectacular blowout which emptied the front tubes contents within seconds; this on a smooth paved road with the bike relatively unladen and the temperature in the low 30's(C).....and always use a floor pump to check and periodically top-up.
[/QUOTE]

Telly; I think your last sentence is the bread crumbs leading to the primal cause of the tube failures. I never have them and one thing I have always done on all high pressure tires is to reduce the pressure to about half at the end of each days ride and then pump them back up the next morning for the next day of riding. Doing that takes most of the stress off the tires and tubes when you aren't riding...for most folks that is about 3/4 of the day in non-riding mode when the tires could be given a break. Suggest give that a try and see how it works for you.

/K

cny-bikeman

It might help to see a clear pic of the failure, especially if you have more than one of the failed tubes. It's not a tube defect. That would only possibly be true if the valve reinforcement actually separated from the tube. Although there are reports of that happening (and more often than longer ago) the OP does not describe that.

Looigi

Deflating tires when not in use is totally wack, IMO. That stem schrader to presta insert thing sounds fishy. Does it prevent the tube immediately adjacent to the stem from sitting flush against the rim? Can you provide a pic of that?

Telly

@ksisler, because of the frequent use of the bike (my only means of transport), I don't think I have the patience to partially deflate and inflate the tires every day... x2 since I just bought another bike.

@cny-bikeman, I disposed of the tube at the spot where it failed, and didn't have the mind to take a pic with my cellphone. I have drawn a pic of the damage I witnessed if that helps, but keep in mind that the tear was a couple of mm inside the valve "patch" which is quite large on the Protek Max.





@Looigi, When I first got the rims during Christmas, I checked to see if the adapter interfered with the tube, and because of the double walled design of the A719, the adapter was flush with the inner surface with zero vertical play in the opening. Since it was stock with the wheels which are designed for heavy touring, I don't believe that the adapter is at fault. Even the rip in the tube is farther out than where the adapter is positioned.

Here's what looks like the stock Mavic fittings look like which came pre-installed with the A719s and was never tampered with or removed/replaced.
https://www.sjscycles.co.uk/mavic-rim...esta-prod3335/

Looigi

Sounds like the adapter is legit. The area where you indicated the tube failed is where it would might fail if the base of the valve was not sitting down flat enough with the inside of the rim. Could be an issue with with the base of the valve in the tube or with the size of the hole in the rim. The diameter of the valve hole on the inside of the rims I have here is 8.5mm.

Telly

I read up on Schwalbe tubes (thanks Sixty-Fiver!), and the touring group (because of my weight!) recommended the SV-18 models, which unfortunately were out of stock locally and at my online locations so I went ahead and order two pairs of the following which are inexpensive and will (hopefully) last until I can find the SV-18s:

Continental butyl inner tube - the robust one
700 x 32 - 47 C, weight approx. 170g Presta valve (42 mm)


https://www.rosebikes.com/product/detail/aid:46399

OneGoodLeg

I've seen tubes that have prolonged use fail at that spot over time, due to the stress placed on the valve when filling the tire. Even with a locknut, the valve moves a bit during the filling process. Sort of like taking a piece of plastic and bending it back and forth. It will eventually break. Actually, so will a sheet of Aluminum.


It Could have been due to the tire already having some miles on it when the valve stem was pulled through the hole in the adapter that weakened the spot enough that subsequent tire refills weaked the spot enough to fail.