TUBES, ETC. (some ranting too)

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  • TUBES, ETC. (some ranting too)
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Anonymous's picture
Anonymous

For discussion:

My tires are 23s, but some of my tubes cover varying sizes: 20-28 some say. Others 20-23.

I guess weight (wennie) is a factor.

Are there any other considerations??

Also, does anyone ride 20cm tires?

And while I'm at it, who the **** designed those long, narrow-grated storm drains that seem perfect for catching road tires? Huh!?!

John JP

Anonymous's picture
Evan Marks (not verified)
Don't be fooled by the hype

No matter what you've heard, threaded valve stems are completely bogus because A) they wear out the sealing gasket in your floor pump much faster, and B) the locknut is unnecessary and can actually contribute to premature tube failure by overstressing that area of the tube. Smooth valves are the way to go.

Sizes are a joke - 23mm tubes work perfectly inside my 30mm CX tires, for example. Stay away from supermegahyperultralight tubes, which have a nasty tendency to develop pinholes because the rubber is so thin, unless this is your TT bike and you can count on neutral support vehicles to change your wheel when you flat.

Last time I ordered tires they sent me 25s instead of 23s and I was too lazy to send them back. Glad I didn't - they're VERY comfy.

Anonymous's picture
Goon Koch (not verified)

"Well, the threaded stems are not _completely_ bogus.

Their purpose is to hold the tube in place and prevent sliding on the rim while you wrestle with the tire, and also to keep the valve stem from retracting into the rim while attaching the pump. These functions was presumably more useful when more people carried the Silca frame pump which had no locking mechanism. I use such a pump from time to time, and I appreciate all the help I can get.

Yes, the threads will wear your pump head grommet more quickly. That grommet costs, what, fifty cents?

Unless you severely overtighten the nut, your tube should not be at risk for damage. Once the tire has been mounted, and the tube inflated, the nut serves no purpose.

The Michelin ""Service Course"" tubes are the most common model with smooth valve stems.

Jobst Brandt has proven, with extensive testing, that given equal casing thread count and tread thickness, wider tires have _less_ rolling resistance than skinnier ones.

Jobst has advocated using the fattest tube you can stuff in your tire. I'm not sure I would advocate that to everyone, but the tube size designations are probably not something paying a whole lot of attention to.

Tire sizes are nominal. Continentals run narrow, Michelins run wide, your mileage may vary, etc. Avocet recently changed their sizes to reflect ""true size"", so the designations can even change from year to year."

Anonymous's picture
Art (not verified)
Tire Width vs. Rolling Resistance

">>Jobst Brandt has proven, with extensive testing, that given equal casing thread count and tread thickness, wider tires have _less_ rolling resistance than skinnier ones.<<

At a given pressure. But narrow tires are usually are run at higher pressure. Still, I prefer slightly wider tires for their ride qualities.

http://yarchive.net/bike/tire_pressure.html

>>Tire sizes are nominal. Continentals run narrow, Michelins run wide, your mileage may vary, etc. Avocet recently changed their sizes to reflect ""true size"", so the designations can even change from year to year.<<

I find the Michelins are dead on. As you say, the new black sidewall Avocets run true, while the older ones were about one size narrower than labeled.

Art



"

Anonymous's picture
Anthony Poole (not verified)
How about wider riders?

>>Jobst Brandt has proven, with extensive testing, that given equal casing thread count and tread thickness, wider tires have _less_ rolling resistance than skinnier ones.<<

A friend of mine in England once asked a member of staff at Condor Cycles in London whether the same was true of wider cyclists.

Sorry to go completely off subject, but Condor is a great bike shop if you happen to be in London. It maybe found on Gray's Inn Road just north of the junction with Theobalds Road, Gray's Inn Road and Clerkenwell Road. Nearest tube station, Chancery Lane, on Central Line. Walk just over one block north on Gray's Inn Road and the shop is on the left hand side.

Anonymous's picture
John Z (not verified)
True to a Point

This is true to a point -- for two tires of the same type (say my GP3000s) a 700X23 tire will have less rolling resistance than a 700X20, for the same pressure. However, 70X20s can be inflated to a higher pressure, hence having a lower rolling resistance, and tire pressure is a more significant contributor to rolling resistance than marginal width increments.

Anonymous's picture
<a href="http://www.OhReallyOreilly.com">Peter O'Reilly</a> (not verified)
oh nuts!

Fine post; just one small point of contention.

Once the tire has been mounted, and the tube inflated, the nut serves no purpose.

The nut also helps keep the tube and in turn the tire secure when you flat. This is a consideration if you have a blow out at a high speed, on a winding descent, making the tire less likely to roll off the rim.

As for me, I prefer the narrower spec. tubes (2 of them fit more easily in my saddle bag) w/ smooth stems, with or without nuts, fine wine and long walks in the park.

Anonymous's picture
Evan Marks (not verified)
Gimme a break

>The nut also helps keep the tube and in turn the tire secure when you flat. This is a consideration if you have a blow out at a high speed, on a winding descent, making the tire less likely to roll off the rim.

You really think that's gonna save your @$$ in a highspeed blowout? I bet you believe in the tooth fairy too.

No, I refuse to believe that old saw. Maybe it's a carryover from the early days of clinchers - crochet hook rims and steel bead tires - and maybe there was a shred of truth to it once upon a time (though I doubt it) but realistically the tire either stays in place or goes it's own merry way (if you're still upright, which in itself would be miraculous) but that little nut is NOT gonna make one whit of a difference.

Anonymous's picture
<a href="http://www.OhReallyOreilly.com">Peter O'Reilly</a> (not verified)
knowledge v. experience

From what you write, it appears as though you have never had a blow out at considerable speed. I could very well be wrong about this, but you are definitely jumping to conclusions.

I was commenting about _minimizing_ the risk of the tube causing the wheel to jam in a blowout. (I also know from experience having strongly held opinions and biases tends to cloud the mind and limit the interpretation of what others write.) Whether this risk is something of consequence/consideration is another matter. I am speaking from experience with such blow outs and am very familiar with measuring risk (being an actuary once upon a time).

More importantly...
It's just my opinion, but to offer such a strong opinion and conjecture with bombast is incredulous. And why the condescending tone? Let's assume what you write is 100% correct. You lose as you have accomplished creating disfavor and ill will with me and put yourself in a less flattering disposition. The msg brd loses too as folks will be discouraged from posting. As club Msg Brd stakeholders, this is something worth considering much more than the tooth fairy, I think. (end of rant)

Anonymous's picture
Evan Marks (not verified)
blowout experiences

Every blowout I've ever had has caused an immediate crash - highspeed, lowspeed, or no-speed. The tires have always remained on the rims with the shredded tubes still inside. I've never been lucky or skillful enough to bring the bike to an upright stop so it's impossible for me to believe that a tire nut would even matter. To say I'm skeptical would be putting it mildly, but you should not take my sarcastic reply as condescending.

Anonymous's picture
Art (not verified)
YMMV

"Evan Marks wrote:
""Every blowout I've ever had has caused an immediate crash - highspeed, lowspeed, or no-speed.""

I had two blowouts back when I was using Wolber ""Invulnerable"" sew-ups. The blowouts were on the rear wheel and neither resulted in a crash.

FWIW, I don't use those valve nuts anymore.

Art"

Anonymous's picture
<a href="http://www.OhReallyOreilly.com">Peter O'Reilly</a> (not verified)
blowouts

Maybe I am very lucky or very skilled or both, but I have yet to biff on a blowout. On a few occassions I have had the tire roll unseat from the rim with the tube flopping out. For one it was with loose fitting Vittoria tires which I was able to install w/o levers; for another a shallow rim bed on a hot day w/ the air pressure jacked.

And sarcasm is defined as...? Condescending, sarcasm, word du jour, pick your poison, I still stand by my original comments.

Anonymous's picture
Art (not verified)
Tubes and Tires

In general you should get the same size tube as tire. A smaller tube will work, but is more easily punctured due to being stretched thinner. An oversize tube may be difficult to install.

700 x 20 tires are prone to pinch flats unless you run very high pressure. They give a jarring ride and poor traction.

Tire size and pressure have a greater impact on ride quality than anything else including the frame. Experiment with different sizes and pressures to see what you like.

Slightly wider tires (e.g., 700x25 or 700x28) will often provide much more comfort and stability with very little additional weight and rolling resistance. Of course the ultra tight clearances on many modern bikes may preclude anything wider than 700x23.

Art

Anonymous's picture
John Z (not verified)
Winnie Response

I took an integrated approach to building my newest bike. The goal was to build a sub-15 pound bike without sacrificing reliability, comfort was a secondary concern. Without resorting to carbon fiber (reliability concern), tubular (practicality) or other exotic wheel types (reliability concern/repairability) , this was no mean task. In meeting my design goal, tires and tubes were the final consideration. If weight and performance are the utmost consideration, in my estimation the obvious choice is 700X20 Continental Grand Prix Super Sonic. When inflated to maximum pressure (170 psi), these clinchers perform like tubulars. I love the feel of the them. However, they are not really suited for anything other than racing. I settled on an interesting compromise: a 700X20 Continental Grand Prix 3000 in the rear for increased reliability, and a 700X20 Continental Grand Prix Super Sonic in the front for weight savings and reduced rolling resistance. For tubes I use Continental Race Lights (or equivalent). So far, this configuration has not resulted in an increased number of flats, but I also change my tires for frequently than most. I inflate the rear GP3000s to 145 PSI, and the front Super Sonics to a bit more. Some might find the ride a bit jarring; it does not seem to bother me. Rear traction is an issue. When climbing out-of-saddle at greater than 500 watts (a short hill sprint), I must be careful to keep my weight back, as 700X20 Grand Prix 3000s provide less traction than 700X23s (or 700X20 Super Sonics).

Anonymous's picture
Art (not verified)
Loosened Fillings?

>>When inflated to maximum pressure (170 psi), these clinchers perform like tubulars.<<

Ouch! I hope you have a good dental plan.

Art

Anonymous's picture
Tubie guy (not verified)

">>When inflated to maximum pressure (170 psi), these clinchers perform like tubulars.<<

Well, I'm not sure how you define ""perform"", but have you ever ridden sew-ups? Or are you quoting ad copy?"

Anonymous's picture
Don Montalvo (not verified)
Hehehe...I thought it was funny too...

...my very first set of racing wheels were sewups (switched to clinchers after my first flat).

I always get a good laugh when someone (anyone) claims even the best clinchers are anywhere near as awesome as even the cheapest setups.

Don

Anonymous's picture
Mordecai Silver (not verified)
170 psi for the road?

"""When inflated to maximum pressure (170 psi), these clinchers perform like tubulars.""

Sorry to pick on these words, but I would never inflate my Continental Sprinters (tubulars) to 170 psi for road riding, even though that's the pressure they're rated for. I prefer around 115-125 psi. I have used 140 psi, and even that's a little too harsh for me. 170 psi is a pressure one should use on the track, not the road. But to each his own.

People who have ridden sew-ups for many years tell me that the nicest-riding (for the road, not the track) were the silk Clement Campionnato Del Mondos, which measured about 28-31 mm wide.

The G.P. Supersonics are so light because the tread is so thin. And they're expensive. So the manufacturer gives you less for more. I'd be very careful about skidding those tires: one time and they're shot."

Anonymous's picture
Evan Marks (not verified)
aerodynamics

"Getting back to that TT bike of yours, you might think there's an aero advantage of 20mm tires over 23s but according to John Cobb, the aerodynamicist who's done a lot of work with Lance: ""Tires and their blending shape at the rim can make a big difference in ... aero numbers. What tire is the best for one is sometimes the worst for another. I'm working on a chart to help with this."" IOW, there's an advantage only if the tire shape is faired into (or ""blends"" into) the rim, and only if there is no circumferential mold line protruding from the tire and messing up the airflow. To accomplish this, an 18-19mm tire might be necessary for a 19mm rim, and you might have to get down there with an emery board to sand down the mold line.

That's the front wheel, BTW. The rear is a whole 'nother can of worms. Got Cervelo?

"

Anonymous's picture
John Z (not verified)
Test It

Lets do a coast-down test and settle the issue.

Anonymous's picture
JP (not verified)
SCREWS

A while back, I removed the nuts from my threaded stems - and proceeded to get 3 flats in about 400 miles. I put the nuts back on, and I was back to getting flats only sometimes. Someone told me the nut keeps the tube in place, esp. around tight turns or when rocking your bike while sprinting. I really don't know, but it's working for me - is it just coincidence? Maybe the tire pressure keeps the tube stem in place?

John

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