Why no puncture resistance tubes in expensive bikes?

[merckx56]

does anyone want to explain the concept of threads per inch to the OP, or shall we just leave it alone?

[BsickPassat]

does anyone want to explain the concept of threads per inch to the OP, or shall we just leave it alone?

he didn't ask.... but now that you're going to pique his interest.... you;ll be the sucka explaining it.

[Saintor]

P.S. Don't bring the TCL attitude over to the Cycling forum.

Actually start with *yourself*.

[Saintor]

Back to rims... when you look at a cross section, the double wall boxes in the sidewalls, which gives the wheels strength, while able to reduce wall thickness to reduce weight. Without the double wall design, the sidewalls will have to be significantly thicker to handle the shear applied to the walls from the tube/tire bead, the cross section would be a U shape.



for applications where a wheel will see more impacts, wheel designers don't beef up the sidewalls, they add more to the box section

Example:


or...in the case of the rim for the cyclocross bike I ordered


and I would expect the rim cross section of your Giant TCX bike would have something similar.

There are wheels where the spoke holes don't penetrate into the rim bed


Guess what? Even stronger!!! since it lacks all the stress risers found in conventional design rims. (and no need for rim rape)


DOing it wrong anyway. A drill bit doesn't create a perfectly round circle. An oblong circle will concentrate stress on certain areas of the stem, instead of a a more consistent load around the stem.

YOu should be drilling to a size slightly smaller, then use a straight reamer drill bit to get to the final size. (you won't find that in the PE exam)

Nothing new under the sun. Adding more to the box section is by far the best method. The reason why the upper section is thicker is two fold as I can see it. First you gotta have some meat to build threads in it!!! Second the stress is pretty much concentrated in the first 1/16"s around the hole but not necessarily away at more than 1/4"-3/8". Each spoke on my bike is distanced by approx 1.5". There is plenty of room to add another hole between *all of them*. "Structural reason" is not a reason not to drill / install a schrader valve. Don't worry. I bought a tons of reamers in the past and I have a set of unibits. I chose rather to go with a 21/64" drill bit (as recommended on another site - I am not alone to not like the Presta valves), deburr and the job just works; my rims don't like altered at all unless you put your nose on the valve.

I didn't know that the Presta valve thing was a religion.

[Biz]

The reason why the upper section is thicker is two fold as I can see it. First you gotta have some meat to build threads in it!!!

Thread's over, everybody go home.

[Saintor]

Thread's over, everybody go home.

Yeah... I see what you mean. Scratch that part.

[withnail]

Besides the issues with structural integrity that people have brought up, there is one other issue you might have. Valve stem length... I'm not sure what kind of profile rims you have but most modern road wheels have a deeper profile than the Schrader valve stem length. Just a heads up, you might end up with something that looks like this:

[ironmule]

thread jack questions: I tried going tubless but setting the bead on my Sun Doublewides was impossible- so i threw in a tube and added Stan's milk to it. Will this help eliminate pinchflats and punctures?

[Biz]

thread jack questions: I tried going tubless but setting the bead on my Sun Doublewides was impossible- so i threw in a tube and added Stan's milk to it. Will this help eliminate pinchflats and punctures?

Short answer: Maybe.

Long answer: You're probably screwed on pinches, since they're usually big holes with rapid loss of pressure. The sealant can't keep up. Small punctures you'll probably be okay. I ran Stan's in the tubes on my CX bike when I lived in Utah because of all the goat heads and had good luck with it sealing those holes up. The punctures were so small and the pressure so low that the tube didn't tear at all, it just got tiny pin pricks.

Questions, not answers: Are your Doublewides tubeless? Did you use a Stan's kit to convert them if not? Were you using a compressor to seat the beads or trying to do it with a floor pump? Did you lube up the beads with soapy water before trying to seat them? Are your tires tubeless? Did you put a metric asston of sealant in there if not?

[BsickPassat]

thread jack questions: I tried going tubless but setting the bead on my Sun Doublewides was impossible- so i threw in a tube and added Stan's milk to it. Will this help eliminate pinchflats and punctures?

start a separate thread

[DJKhakiPants]

To answer the original question - high end bikes do not come with flat resistant tubes because they are heavy and will still flat. On a test ride the bike with flat resistant tubes will feel sluggish and hard to get up to speed, vs company B's bike that is nimble and quick to accelerate. They also cost a little more and add zero value to the bike. It doesn't matter much on one bike, but scale it up and it will start to show.

As far as tires, the bike companies will put the cheapest thing they can on there to sell it because that should be the last thing that makes the decision for you on anything >$1k, and tires are largely personal preference. Most of the people serious about riding will take off the house brand tires that came on the bike and throw on a performance set.

Presta valves are for high pressures and lock by tightening the top of the valve. Mechanically this was determined to be the better valve type and thus was adopted by the industry as the standard for high performance wheels. By drilling out your rims you void the warranty on your month old wheels. If you spent a grand on a bike, go ahead and spring for a $40 pump.

Flats are a part of cycling. The flat you got from glass is purely chance. I have gone a year with 1 flat and a week with 3 flats. One of the rules of cycling is to keep a spare with you. Be sure to avoid the pinch flats by topping off your tires before every couple rides. Your tubes will lose a few PSI each week due to rubber being a naturally porous material. Do not use CO2 to inflate unless you are stuck on the side of the road. The CO2 will leak from the tube over the course of a week or so until the tire seems completely flat again. If you use CO2 on the road changing tubes, air down the tire when you get home and pump it with your regular pump. Compressors are OK, but check that the tire is completely seated on the rim, because if that tube explodes in your face you may have to change your pants.

[J-Tim]

Well said.

With 23mm tyres, you want to top up before every ride as there isn't much air in them to begin with.

If I pump up mine to 120psi in the morning, they are down to 80-90 by the next day.

[TW@]

Lighten up people.

Yes, you can drill additional, much larger holes in your rims, it's been done lots of times in the "fat bike" community with no ill effects. It's been found to be structurally sound, and reviewed by more engineers than the number of PE Stamps in your typical PE's desk. (Edit: I am a Mech E. as well)



Gratuitous road bike trials video of a good buddy to lighten the mood.

[colnago]

Well said.

With 23mm tyres, you want to top up before every ride as there isn't much air in them to begin with.

If I pump up mine to 120psi in the morning, they are down to 80-90 by the next day.

So i'm not the only one? Thought I had "Underpants Gnomes" stealing air out of my tire for "Phase 1".

[J-Tim]

So i'm not the only one? Thought I had "Underpants Gnomes" stealing air out of my tire for "Phase 1".

Nope, just pure laws of physics.

[username]

Compressors are OK, but check that the tire is completely seated on the rim, because if that tube explodes in your face you may have to change your pants.

....and buy a hearing aid

[Biz]

Yes, you can drill additional, much larger holes in your rims, it's been done lots of times in the "fat bike" community with no ill effects.

Those guys consider 15psi to be "too high", though.