I've only had this bike a few days. Went up my driveway at speed and both tires blew (My full weight was on the seat at the time). Air began to almost immediately gush from in-between the rims and tires.
I assume the tubes are just old or underinflated, because the tires seem fine [to me]. The bike is a new-to-me REI Novara Safari (700×38). Xl frame. Purchased recently. Unsure of the year.
There is the factor that I'm a larger rider, though (6'2 and roughly 300 lbs). And also a new one. Haven't had a bike since I was a kid—and those were all bmx bikes. Still trying to get comfortable with gears and being on a bike again, but I was enjoying myself.
Ordered rim tape, tires and a pressure gauge under the assumption I was right, but the thought hit me that I could be completely wrong in my estimation. I would imagine this falls under the most basic of bike maintainance, so rather than mucking along in ignorance with trial and error I thought I'd bring it here. At the very least I figure my situation may inspire a few light chuckles—and laughter is medicine. Thoughts? Advice?
by inkandhunger
21 Comments
Too low pressure, hitting the bump on the driveway caused a pinch flat in the tube most likely. New tubes, and look up a pressure gauge based on tire size and weight.
How many psi did you run your tyres at? Since you’re quite heavy, you need to pump up the pressure otherwise you’ll get pinch flats.
However, just to eliminate other variables, take off the tyres, run a cotton ball along the inner side to see if there are any debris that can puncture the tubes. Then check for burrs on the wheels, particularly around the valve hole.
if both tubes went at the same time it would be no rim strips, rubber rimstrips, you should be using nylon, in use with double walled wheels or tiny tears in the tires, or both wheels have spokes that are to long and punctured the tubes. my guess is the rim strips, or the pressure was to low, those tires should at a minimum be at 60 psi.
Quite possibly you experienced pinch flats where the inner tubes were not properly seated in the rim and became pinched between tire and rim. You also need to properly inflate to near maximum pressure.
If the tire inflation was far too high or half of what it should be, that can happen. (250 lbs checking in.)
Replace the tubes, and probably look on Silca’s Tire Pressure Calculator for how much air to have in ’em. [https://silca.cc/pages/pro-tire-pressure-calculator](https://silca.cc/pages/pro-tire-pressure-calculator)
(The answer here is “about 50 psi”.)
Initial though – under inflated tires/tubes caused pinch flats. What pressure was in them at the time? Also wonder about old tubes but the pinch flats make more since because both tires went flat at the same time.
The current Continentals are decent tires too. Did the flats damage the tires? What tires/tubes did you purchase?
Velox rim tape is really the only one to use and if you can’t mount the tire with your hands, get a Crank Brothers lever; don’t use a traditional lever to mount. At your weight, you should inflate to max recommended pressure.
Just to be sure, since you mentioned it – you *already* had rim tape in them when the blowout occured, correct?
You can look at the hole in the tube and it should help diagnose. Snake-bite, rim imperfection, foreign object, etc.
Also make sure you’re using the correct tube for the tire size. Some leeway is okay, but too small and it can thin the tubing walls, too big and it can cause folding inside.
Frame bag is installed wrong. It should be the other way around, following the contour of the frame.
I think you’re on the right track with the steps you’ve taken.
If they were underinflated, that’s exactly what would happen on rough terrain : “pinch flat” puncture caused by the tube being pinched on the rim on a bump.
Do inspect your tires for any foreign objects stuck in the rubber, as well as the rim strips, but the most likely candidate here is inappropriate pressure.
A pump with a gauge is a must. If you’re on the bigger side + riding mixed terrain, a good starting point is the maximum pressure stated on your tires.
A bit off-topic, but I have never seen handlebars of that shape. Could someone enlighten me on what style those are / why you’d want them?
Double check your rims and tires; if they are stiff or frayed on the rim where the bead catches they should be replaced. That would cause your tubes to pinch and blow or flat as well because the tire doesn’t stay in place or flex as intended.
You Pinch flatted both tires. It’s ok. Now you get to work on it. Make sure to pump them up next time
Flip your frame bag around! It has a place for a strap on the back to stop it from flapping around like an exposed undercarriage.
If you really did manage simultaneous pinch flats, you should check for rim damage, too.
Also, some may disagree but if you’re using this as a commuter/all arounder, I would run the biggest tires that will fit in the frame.
Sweet bike…I really am kind of fond of these, every time I see them.
“6’2” 300” there you go.
As others have said, this is not weight related, it’s setup. Fresh tape, good tubes, correct PSI, go forth and kick ass.
Almost certainly tyres at too low a pressure and when you went over the bump it caused pinch flats.
On the sidewall of the tyre there will be a recommended operating pressure range for the tyre, for example 30 – 70 psi, It is important for you to know going forward that this does not mean you can run the tyres at 30psi and all will be good.
The pressures on the sidewall are the range you should use so for example a light rider carrying nothing can use the lower end of this range but the more the rider weighs plus the weight of anything else you are carrying the higher up the range you have to go.
As a rough guide Silca pressure calculator ( https://silca.cc/en-gb/pages/pro-tire-pressure-calculator ) suggests for your weight with out carrying anything else you should be running around 52psi on that size tyres
Odds are pretty high that it was a pinch flat especially with that much weight on the bike.
When you get new tubes, make sure that you have a bike pump with a pressure gauge to get them inflated to the proper PSI.