BIKEPGH MESSAGE BOARD ARCHIVE

I had the forte ultra thin long valve tubes. Im not sure what happened to the first one, but it lasted me 6 months or so. The other one just blew out last week, after patch #5...lasted around 9 months. I think one of my current tubes is an avenir (sp?) and I'm not sure about the other. One is brand new and the other was brand new a few months ago, got my first flat on it last week (pinch flat from hitting a pothole in the rain).

Almost all of my flats have been mysteries, though.

I have used Bontrager tubes and never got a flat while using Bontrager. I have been using then for 2 years even in the winter. The only time I had a flat I was switching my summer tires to winter tires and I'm not that good at changing tires. I didn't line up the tire and the tube right and had a blow out. I was closer to Performance Bike than Trek so I got a tire change there the next week I got another flat. That time I got a tire change over at Trek with Bontrager tubes and I've been good to go. So except the Performance Tube and my blow out because of my poor tire changing skills no flats in two years.

I have no idea what tubes came on my bike (well, maybe "Cheng Shin" - that's what the current Cross-Check page says), but no flats for >1.5 years until I ran over a tack. So, the front one's streak is still going, almost 2 years now.

I replaced it with a Bontrager although I don't like the long valve, it seems damage-prone.

But, I assumed it was the tires more than the tubes?

Happy with Bontrager. No flats for over 3 yrs, except for a pothole snakebite which also bent my wheel. I run Continental 4 seasons or 4000s, 23mm. Also happy w/Continental for durability & flat resistance.

In the case of the forte's, I'm fairly certain its a combination of how thin the rubber is with how cheap it is.

Certainly having cheap tires don't help much in protecting your tube, but a cheap tube is more prone to pinch flats and not having enough body to keep air in even when slightly compromised.

I haven't had any flats on my MTB for 2+ years either although I don't ride it that much and don't ride it that aggressively anymore. But I got talked into putting some ridiculous "thorn-proof" tubes on that thing. If you haven't seen them, the box they come in was seriously like 3-4x the size of a normal tube box. Seemed like a good idea at the time but holy crap do they weigh a ton and I'm sure they contribute to making that bike even slower than it already is.

I'm no expert but I always assumed the better the tire the less flats you get. I'm so bad at changing tires especially in a pinch that I was looking at getting the Thick Slick tires, I just need more info on them. But if good tubes is what I need then I'll stick with my Bontrager tire and tube combo.

Interesting conversation.

Until now, I would never have guessed that the tube would make a difference. I assumed that if something penetrated the tire deep enough, it was going to go through the tube too.

I bought a "back-up" Forte a couple months ago (cheap, I think, it cost maybe $4??). I expected that the tube was basically the same as all others, now I wonder. I'll be watching.

It would seem that forte tubes have a chronic stem separation problem, which is confirmed by the flat that I got today. (Found reports of this dating back a few years at a few different places)

Should also clarify that any ultra-lite, ultra-thin racing tube, even high performance types, can be more prone to pinch flats just with how thin the material is. Latex tubes for instance aren't exactly the best idea on city streets, but they can be great for racing on blacktop or on a track. Thats why the average tube is made of butyl.

I've got some model of Forte tubes that is touted as a "commuter" tube...the OD wall thickness is about 5x the thickness on the ID. There's an abrupt change in the cross section at the transition point. They are heavy as all hell. I haven't had a flat with them yet due to any road events, but I've had two failures where the valve stem attaches to the tube. When I go through this 4-pack, I won't buy them again.

[Edit my last comment ]

I have a Forte in my rear tire now (installed on the day of the keg ride) and a back-up Forte. I'll be watching.

I've had flats with both trek and performance tires and tubes. They always seem to come in waves. I'll go six months or more without a flat, then get three in a month. FWIW, the majority of my bad luck comes from glass I see too late to miss.

The last batch came from Scholl's in West View, and appear to be SunLite.

I'd never paid attention before, never cared. I just walk in with the size written on a piece of paper and buy two or four of whatever's there.

In my experience, tube life has far more to do with luck and proper inflation than brand.

I have used all types and brands of tubes, and I have had tons of flats. I haven't been able to make any correlation between tubes and flats.

I think a lot of it is (lack of) luck.

I tried Forte Lunar Lights, then Lights, then Standard; all crap.

No flats since switching to Bontrager. Until last week when my front tire (5-week-old Bontrager) came unraveled at the bead and punctured both tubes I had with me. The tire was replaced no questions asked at Trek.

When possible, I'm a Schwalbe snob with regards to tubes. Can't speak to flat prevention; they just hold air far longer than any other brand I've used.

(Although, come to think of it, I suppose a tube that holds air longer might ward off pinch flats a bit better...)

can't say I'm a tube snob at all... generally use whatever's cheapest and put money in the tires.

I have been working in bike shops for 20 years (just to give a little background on where this is coming from).

A tube is a tube. They are all pretty much the same. I know bontrager had a defective batch of tubes a few years ago. Other than that, if we are talking about regular tubes, no tube is going to be any different than another.

Ultra light tubes are just as puncture resistant as regular duty tubes. The ultra light tubes will pinch flat more easily. heavy duty puncture resistant tubes will puncture just as easily. A piece of glass or a thorn will work through one of those tubes too, it will just take another mile or two down the road until it works through.

A good puncture resistant tire is what you should be more concerned with. I have 10's of thousands of miles of city riding over broken glass and shards of metal and I can only remember ever getting one flat tire while running good tires. I believe that flat was because my tire was getting thin and worn out.

I know a few people who have gone tubeless on their commuter bikes and they are running low tire pressures for comfort without fear of pinch flats. If they do get a puncture the sealant fixes the hole. I am going to go that way in the near future.

*edit* I just want to say I have no experence with the Forte tubes, only Specialized, Bontrager, Quality Q-tubes and Cheng Sin. All of those tubes are exactly the same thing.

I had a failure on sunday... I don't know what tubes I had (this was the one remaining from the factory). It was a valve issue though - I pulled off the pump after attempting to top off, and a small piece of metal came with as all the air simultaneously left the tire. I have utter faith that it was user error rather than valve or pump error. Will replace tonight. I cant find the replacements I got when I had my first flat (tiny stone made it through factory tires, replaced the tire with Schwalb marathons to flat-free riding ever since).

My goal is to have so few flats that I never get very fast at repairs/fixes, but to have enough flats that I can actually repair/fix them myself with confidence (and no more valve errors). I am not there yet.

What kind of tires did you buy? I would guess that your flat has to do more with the tire, or something sharp in the tire or rim when you changed it.

I break or bend alot of presta valves, but I have the touch of a gorilla.

Coming from a mountain bike perspective, tires make all the difference. I've had cheap Kenda and Bontrager tires that would flat on about 1 out of 5 rides. I got some good durable WTB tires and I get about 1 to 2 flats per year. Tires are also more prone to flat when they wear out. Either from worn tread or dry-rot. Their casing just isn't as strong as it used to be and that makes the tube more vulnerable to sharp, pointy things and pinch flats.

Edited to say: It is also about where you ride and what you run over (luck). I've pinched flat hitting big rocks on trails. But I've also had flats from running over crap like staples in my basement when taking out my bike.

ejwme: You probaly broke the tip off of the presta valve. It is a common thing to do if you are not very careful taking the pump on and off. It is very easy to do with my blackburn floor pump if I am not careful and I am rushing to get out the door. This makes for a lot of choice 4 letter words.

I think I am going to buy a prestaflator: http://www.prestaflator.com/ to use on my air compressor at home. Pushing the inflator straight on and off will eliminate bent/broken valves.

Jason: I've been looking for exactly that (prestaflator) for a year and couldn't find a cost effective solution. Thanks a ton for posting that!

When the Performance store opened I took advantage of their tube-recycling promo and got two cheap Forte tubes. I went home, installed one and pumped it up. At 60 psi it blew out catastrophically, shredded along the seam. I installed the other one and it's been fine ever since.

On a related note, make sure you're using the right size tube that matches your tire. Tubes that are oversized are easy to pinch between the bead and the rim, and tubes that are undersized get stretched real thin when you inflate them fully.

the best tubes are a rim strip and a bottle of sealant. i am switching all the bikes in our house over to tubeless this summer.

jason, boazo - yup, that's exaclty what happened. I'm going to replace it and get very precise and thorough hands-on instructions on how never to do that again. If I do it again, I'll be trying to figure out if I can get some form of military industrial complex valve meant to withstand the delicate touch of hormonal 19 year old enlisted men. sigh.

cburch... you speak of tubeless (which I imagine would be breakable valve-less too)... what magic is this? pros? cons?

nope still has valves.

the only real con is that its more difficult to swap tires for different conditions. which only really bugs me on my downhill bike since all the other ones are pretty much ridden in only a few specific conditions and therefore don't require swapping of tires.

some form of military industrial complex valve meant to withstand the delicate touch of hormonal 19 year old enlisted men

That would probably be Schrader.

*face palm* yes, valves would still be necessary - unless magic is truly involved. But pros? is it just the weight loss?

No pinch flats.

EJ, I didn't know what tubeless was either so I did the youtube. Look at this demo

http://www.youtube.com/watch?v=9sjvJXJWtAA&feature=related

The tubed/tubeless debate is much like the helmet debate, just amongst really tech nerdy cyclists. I am on the tubed side.

@Marko, that video demo is great: Makes me want to go run over nails right now!

a little less rolling resistance, lower pressure (smoother ride), puncture resistance, no pinch flats.

^exactly^

lower rolling resistance because there is no internal friction between the tube and tire. Rolling resistance is lower because you can run lower pressure, high pressure equals higher rolling resistance on rough roads. A high pressure tire bounces back and up when encountering bumps, a low pressure tire will conform to the bumps and keep going. No punctures because you run a sealant. No pinch flats because there is no tube to pinch.

Now the down side, setup can be difficult if you do not use a Stans rim. I set other brand rims up all day but it is difficult and every one is different. Stans rims setup perfectly almost every time. Setting up tires less than 30mm wide can be a bit scary, I have had a couple blow off the rim while inflating.

I am saving my pennies and I am going to put a set of Stans Alfa rims on my commuter and setup my 28mm tires tubeless and enjoy 50psi comfort.

@ejwme

There is a little screw on adapter to convert presta valves to shreader . + then you can fill your tires at the gas station if you break your frame pump or something.

running 28mm tires at 50psi is just counter intuitive to me... are you not worried about rim damage at that point?

Rolling resistance is lower because you can run lower pressure, high pressure equals higher rolling resistance on rough roads. A high pressure tire bounces back and up when encountering bumps, a low pressure tire will conform to the bumps and keep going.

i would like to see this backed up, as it runs counter to most everything i understand about physics and rolling resistance.

Rolling resistance due to deformation of the tires themselves is always lower with a higher pressure. But a lower pressure can sometimes give you lower overall rolling resistance on soft ground since you sink in less. Also, you get better traction on uneven ground so you can go faster.

Here's what Rivendell sez. It may or may not be true.

There has to be some limit to this > flat.

also http://www.bikequarterly.com/images/BQ64TireTest.pdf

again, fwiw

Obviously there's lots of competing concerns in tire design: cost, long-term durability, puncture-resistance, comfort, rolling resistance, cornering ...

@Hidden Variable http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf

Assuming rough roads the higher the pressure the more you bounce up and down rather than the tire conforming to the bumps and allowing you to roll forward.

@hiddenvariable: Try it your self. I run about 65-70psi in my 28mm tires right now and they roll great. The first thing you need to understand is roads are not smooth. You are constantly hitting bumps. I don't have any evidence other than knowing I have read a few articles on it and have tried it myself.

@dmtroyer: We are talking about tubeless (for the most part). You can't pinch flat if you don't have a tube in there.

@Chris: Am I reading that correctly? Were all of those tests done on rollers?

Jason, I'm just curious what the limit is to the low pressure side... obviously 1 psi isn't going to get you anywhere. What about 2 psi? What about 3? etc.

Also, in regards to my other comment, I guess I was curious if you're not worried about bottoming out on your rims with a 28mm tire at 50psi.

@Jason, yes. I thought there was one test with different pressures but I could be wrong on that. Been awhile since I looked at it.

In general the accepted wisdom that higher pressure does not translate into better rolling resistance. This link may be a bit better:

http://www.slowtwitch.com/Tech/What_s_in_a_tube__1034.html

omg - Brad, you were totally right this is eerily similar to the helmet discussions (just more physics and less statistics)

And thank you everybody for explaining it, I had no idea it was even possible. I like mentally rolling tires/tubes/wheels over things in my mind pondering how things interact, very entertaining. No idea what I should do, but that's ok for now

I have read all the comments and I think I'm more confused as to what is the best way to go. I have lots of different valves, tires and tubes running around in my head, but I still don't know anything. I am a little slow with the technical side of cycling.

ok that last link was the most helpful, so there is an optimal pressure, not just as low as you can go.

Q Tubes! FTW

@dmtroyer: Yes, you still want a decent amount of pressure in the tire. At 50psi my tires bulge just a bit when I am sitting on them. I am about 155lbs. Different weight riders are going to require different pressures. The other issue is if you go too low and you dive into a turn the tire could want to roll out from under you.

Denting the rim is a concern, if you ride with bags and/or can't bunny hop you might want to bump up the rear tire pressure.

@chris: The first article you posted showed that lowering tire pressure increased rolling resistance. He started at 200psi and went down from there. That makes sense on perfectly smooth rollers.

That second article is a great article. That is the first graph I have seen that shows the effect tire pressure has.

It seems in that article he was using innertubes. Innertubes cause internal friction and will increase rolling resistance at lower pressures. In the article his optimum pressure was about 110psi (with what I assume is a 700x23mm tire). I have read that in a 700x23 tire you can safely run about 80psi when setup tubeless with no increase in rolling resistance (assuming average rider weight of about 140-150lbs).

"assuming average rider weight of about 140-150lbs"

That right there is a huge assumption, that most of the information in the links seems to brush right over. The tire pressure you want to use depends ENTIRELY on your weight. I weigh 2XX lbs (and I know I'm not the only non-skeleton on here), so I run 90 psi in my 28mm tires to keep from bottoming on the rim. On 23's I don't use much more than 100. If you sit at a standstill with all your weight on the bike, and you can see more than a slight bulge in the tire, the pressure is too low! Tire performance is based entirely on the contact patch, visualize the oval shape made by the area where the tire and the road are in contact, and the contact patch is based entirely on the psi.

Also, question on tubeless, if you flat in the middle of nowhere, how do you patch that on the side of the road? It seems like something that needs to be done in the shop. Or do you just carry the right size tube, and tube it in the case of a flat? I base all my bike equipment decisions on the ability to fix things on the side of the road, in the middle of nowhere, with no cell service, with banjos playing in the background.

I think "rolling resistance" needs to be redefined for the context in which it is being used in this thread. In basic physics, it involves factoring the coefficient of friction for the tire material and the amount of surface area the tire has against the road/trail. In that case, the lower the pressure, the greater the surface area and, thus, the greater the rolling resistance.

This would also mean that better traction equals greater rolling resistance.

The reaction to the bumps and such is an entirely different issue from resistance. It is more of a handling issue. IMO, of course.

@edmons: You can just put a regular tube in there like you would fix any other flat.

@morningstar: You are right, the terms are confusing a bit but it is still rolling resistance. It is just rolling resistance on an uneven surface, not a linoleum floor. Have you ever gotten a pebble stuck under a shopping cart wheel, where if it was a pneumatic tire it would have rolled right over? That is the kind or rolling resistance I am talking about.

I think any confusion can be sorted out with the Wikipedia page. It discusses rolling resistance and rolling friction. It counters a lot of arguments on here so you will still be left with the question of "who to believe?", but it gives some good examples.

@jason - I think I like Morningstar better. Thanks.

oops, star/sider, same thing right?

resistance vs. friction, yea, makes sense. All I know is I run lower pressures and I don't feel any slower and I am a lot more comfortable so I fell that I can focus on pedaling.

The Wiki page I just came up with supports almost everything I was saying. http://en.wikipedia.org/wiki/Rolling_resistance

Can you provide the page the counters it?

Same page. It says:

"Extent of inflation - Lower pressure in tires results in more flexing of sidewalls and higher rolling resistance.[5]"

The reference is actually from Schwalbe.

The Wiki page I just came up with supports almost everything I was saying. http://en.wikipedia.org/wiki/Rolling_resistance

[citation needed]

so, schwalbe has a good description of rolling resistance in a bicycle tire, and includes this line:

In practice, the energy saving is even greater than in theory as the elasticity of the tires absorbs road shocks, which would otherwise be transferred to the rider and so saves energy.

this seems to hint at what you said, but to me it's so imprecise that it's difficult to even guess at what is being communicated. if the contention is that the elastic pneumatic tire at a lower inflation pressure absorbs road shocks better, and thus transfers less energy to the inelastic parts of the bicycle (fork, frame, rider, etc.), i could believe that. but it's not clear that that's what is being contended.

edited to add: and if that is what's being contended, it has nothing to do with rolling resistance.

I think Jason hit the nail on the head with:

"All I know is I run lower pressures and I don't feel any slower and I am a lot more comfortable so I fell that I can focus on pedaling."

Everything else is just hot air.

edit - I meant hot air from every side of the argument. Not one side specifically.

true. and that's grant peterson's point as well. still, i'm a physics nerd, and i like to get these things right.

My take-away from what Petersen and Bike Quarterly say is that high volume, low pressure tires are not necessarily slower than low volumne, high pressure tires (typically your skinny tires). Yes, it would be kinda dumb to run a 23mm tire at 50-ish psi (3.4 bars for you Euro-weenies). Riv pushes 28mm+ tires because you get a more comfortable ride (thanks to lower pressures) without losing much in terms of overall performance.

I find all of this interesting. For many years it has been pounded into my head that you nee to run the maximum pressure that is printed on the side of your tires. I even used to do that with mountain bikes as a kid. When I grew older I learned that lower the pressure the better on a mountain bike, as long as you can avoid rolling a tire or pinch flatting. For some reason I did not translate that to road bikes or commuter bikes. In the last few years I have been experimenting with lower pressures in the skinny tires. It makes a huge difference. I want to eliminate the tubes because I can eliminate the chance of a pinch flat. I am not real worried about denting the rim because I hit the rim a lot on my mountain bike have yet to dent it. We will have to see what happens on the commuter.