Menu

Technical FAQ with Lennard Zinn: Tubular vs. tubeless, tire pump gauge accuracy, and more

  • By Lennard Zinn
  • Published Aug. 2, 2011
FMB: Tubular tire maker for the classics

Q. Dear Lennard,

I recently had a tubular tire, which I had installed one year ago, peel off the rim enough that the tire felt wobbly while riding through turns. I deflated the tire and inspected my glue job.  While my glue job looked great, I noticed the cloth tape had peeled off the tubular tire in a couple of sections over several inches.

A stack of nearly completed tubulars at the FMB factory in France. Photo: Philip Gale

Upon reflection, I remembered this tire had been bought a few years earlier as a spare and was stored in a box in my sometimes-warm garage. My question is: do tubular tires need an expiration date, assuming this failure was caused by an aged tubular? Have you seen this failure before?  I can’t be the first one, can I?  I found it quite unsettling that this problem could haunt me again: e.g. a bike shop sells me an aged tubular.
— Dayne

A. Dear Dayne,
Well, there’s little question in my mind that over time the glue holding the base tape on starts to break down. The question is, how long does it take? I’m certain that it varies with the tire as well as with the rim cement.

I recently threw out a few 30-year-old tubulars I had in my (often hot) attic. They were used and had been glued on at least once, but the tread was practically new, so I’d hung onto them. But the base tape glue was so dry that the tape was crinkled along the edges and pulled away from the tire, and if I peeled back on those edges, I could pull the tape completely off of the tire’s stitching very easily. These were inexpensive training tubulars from the days when clincher rims and tires were not anything like they are today, and all of my riding was on tubulars. And in general, my experience with cheap tubulars has been that they age poorly, especially in the bonding of the base tape.

On the other hand, I have a number of expensive racing tubulars that are 10 years old and have been in the same attic aging all of this time and are now on my wheels and on my bike. I’ve been riding some of them all summer with nary a problem. I test them frequently for adhesion, since most of my riding is in the mountains, and I like descending fast because I can at least still go fast one direction as I age, but those tires are really stuck onto the (carbon) rims as well as to the base tape.

And as you’re probably aware, many riders and mechanics intentionally age racing tires for periods of years before using them. You would have heard about it if the tires that Julien Devries used to age for Lance Armstrong had rolled off of the base tape on him. (Indeed, the rolled Challenge tire that Armstrong suffered in his untimely crash in his last Tour de France actually did roll off of the base tape, according to one of his RadioShack team mechanics, our own Nick Legan. But the rolled tire was a result of that crash, not a cause of it, and in all of Armstrong’s seven Tour wins he was remarkable in the fact that crashes and mechanical disasters did not seem to happen to him).

I know back in the day, I learned not to use some brands of rim cement (3M Fast Tack and Tubasti both come to mind), as their solvents seemed as though they could soak through the base tape and break down the bond between the base tape and the tire (especially on Continental tires, I remember). This, of course, could cause the tire to roll off of the base tape. I used to use Clément rim cement for that reason; it dried out, but it definitely didn’t seem to affect the base tape’s bond to the tire. That glue’s not available any more, and I’m quite satisfied with Vittoria Mastik One these days.

So, it’s a long “answer,” but I don’t think there can be a single answer as to an “expiration date.” I think it depends on the construction of the tire and of which rim cement is used.
— Lennard

Q. Ciao Lennard,
I’ve read your column about tubular vs. tubeless, and I would like to go through it a bit more in detail, as I’m not convinced about the superiority of the tubeless setup at such high pressure (while I’m of course enthusiastic about tubeless tires at inflation pressures below 45/55psi).

The reason why Vittoria isn’t on board with it, even though we have developed the technology already, is the balance between various factors:

  • safety and mounting: a tubeless bead that will hold safely at 120psi will be almost impossible to mount safely (safely means with almost no tire levers); a mountable one won’t keep pressure or keep the bead in place instead (which is the case with products actually available in the market which of course we have tested internally)
  • air tightness and riding quality: a casing wall which will keep 120psi has to be so thick that it will make the overall performance drop, first of all rolling resistance (we tested it with an external laboratory), even if the rolling feeling is of being faster. On the other hand, a thin casing won’t hold pressure enough, even with dense latex sealant (we tested it too, making a 120tpi 230g TNT 23mm prototype, amazing riding quality but lost too much pressure even in short time and with a modified sealant inside).

These key compromises are made by no other tire industry (truck, aircraft, automotive, motorbike, industrial) using a tubeless environment; none go above 45/55psi…

On the whole other hand, tubulars are still proving (laboratory tests and feedback from pro riders) to offer unmatched performance (grip, speed, comfort) not only in road racing, but in MTB too, where the tubulars are so damn much faster than any tubeless around that it’s just a matter of letting riders try them to fall in love…
Samuele Bressan
Product Manager & Designer
Vittoria S.p.A.

Q. Dear Lennard,
I race on carbon tubular wheels using carbon specific brake pads (Swiss Stop Yellow King), but prefer to train on aluminum clinchers. I thought I’d read somewhere that carbon specific brake pads may embed bits of metal when used with aluminum rims. Am I risking damage to my carbon rims by not swapping out brake pads?
— Jesse

A. Dear Jesse,
You are risking damage, yes! When used on an aluminum rim, any pad will fill with aluminum chips. Just look at yours closely; you’ll see it.

Swap your pads when swapping wheels or accept shorter life for your carbon wheels.

— Lennard

Q. Dear Lennard,
I looked through your online archives at VeloNews, but didn’t find anything regarding this issue (didn’t read each article in detail, as you have many on tubeless, so I could have missed it quite easily).  I work in the parts department of a LBS, and we have now finally started seeing a good number of customers running tubeless road setups.  My question is; When do you need to replace a tubeless tire b/c sealant isn’t going to get the job done?  In other words, when a customer comes in with a flat tubeless setup, what is a good rule of thumb to use as far as punctures and tears go for replacing tires?

If it’s the same general idea as a standard tire+tube setup then that’s easy, myself and my mechanics are just unsure of what to look for in tubeless setups.  Are they similar to tubed tires as far as replacement goes, or are they more finicky b/c of the different method of air pressure?

— Henry

A. Dear Henry,
Once the tread is worn flat on the top, I think it’s time for replacement. Once the tread gets so thin that it starts revealing the casing, the tire is no longer dependable. Once tread peels off of the casing; it won’t hold air anymore.

And when a customer has a lot of problems with air leakage from a sealant-filled tire that looks good, it’s time to peel that tire, remove the valve stem, and inspect the rim for corrosion. I’ve talked about it here, and even though all of the sealant manufacturers claim that their sealants don’t corrode rims, the fact remains that there are a lot of rims out there that have been corroded by sealant. And I know from personal experience that if the rim corrodes around the valve stem, you often won’t see it from the inside or the outside until you remove the valve. Air leaking around the valve stem can be an indicator of this.

And some tire/rim combinations occasionally seem to be problematic for sealing. Life’s too short for leaking tires; if it’s been causing repeated problems despite sealant inside, just replace the tire.
— Lennard

Q. Dear Lennard,
I’m not talking about absolute accuracy, but how do you pick a number on your floor pump and actually know that you’ve reached it?

I’ve been thinking about this for years. As far as I’m concerned, bicycle floor pumps have gauges that are way too small. And, what usually happens is, as you pump the tire up to pressure, the dial never stops at a hash mark but almost immediately starts to drift toward zero. Getting an accurate reading, relative to whatever floor pump I’m using, is virtually impossible because for various reasons, it’s unavoidable that air will leak from the chuck right away. These are the two big gripes I have with floor pumps.

I used to think that the air I heard leaking as I watched the dial indicator return to zero was from the tire. But today I left the chuck on as the dial returned and when it stopped, the tire was still inflated at what felt like the pressure I stopped pumping into the tire. Make sense?

So here’s what I tried today: I pumped the tire up with slower strokes than I’d normally use. At pressure readings on the gauge that are lower than what’s in the tire (as long as the chuck isn’t leaking), I’ll observe the dial indicator stop and hold a reading (i.e. 30, 40, 50psi.); it dawned on me today that the reading is what’s in the hose and not in the tire.

All this would be easy if chucks didn’t leak air. But I’ve found that even brand new pumps will leak at the chuck once the hose pressure exceeds the chuck’s ability to retain air in the hose, and the dial indicator usually drops to ridiculously low readings, if not to zero. What I’ve observed is I can continue stroking the pump slowly (about half normal speed) and the pressure will rise, then this will occur: I’ll hear a little “snap” as the hose pressure exceeds the presta valve’s backpressure, forcing air into the tire. If I watch the gauge as this occurs, I can more readily read the pressure and reliably assume the peak reading when I heard the snap is the actual pressure in the tire. Slow pump strokes make this easier to see as the dial indicator isn’t dancing about. Then I can ignore the dial’s trip back to zero, and the slower strokes let me fine tune the air entering the tire to at least the 2psi hash marks on the dial.

Of course, I just realized that the higher the pressure and the more worn or ineffective the chuck’s ability to seal the valve, the faster air will leak, and the faster I’ll have to pump to achieve high pressures. Today I pumped my tires to 80psi, and my theory seemed to work like a charm; I don’t usually venture to the higher pressures many cyclists use, particularly track riders, so I don’t know if my method is valuable to others, but there’s got to be an easy, more accurate way to inflate tires given the gauges on them and the limitations of thumblock chucks as well as Silca-style chucks.

Does my idea “hold air” (Sometimes I kill myself!)?
— Peter

A. Dear Peter,
Well, this is a beef of mine as well, and I have written about it, with my suggestion being to use a separate gauge if you’re running low pressures in low-volume tires, since the pump gauge pressure is particularly unreliable then.

Your method is actually what I use when pumping my own tires, when I get close to the desired pressure; I slow down just as you say and listen for the Presta valve to open. But I think that it’s too inaccurate for cyclocross tubulars, when you want to hit, say, 28 psi right on the nose, because the hose pressure has to exceed the tire pressure to force the valve open. I don’t know how much it has to exceed it by, and I’m sure it depends on the valve and if there’s any sealant or other sticky stuff in it that resists its opening. But if it only requires a couple extra psi that the pressure above the valve has to exceed the pressure under the valve (the tire pressure), that’s no big deal if you’re up around 100psi; it’s only a couple of percent. But if you’re talking about 30psi, then a couple psi is closer to 10 percent inaccuracy. That’s when I think you need a separate gauge.
— Lennard

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: / / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

Get our best cycling content delivered to your inbox

Subscribe to the FREE VeloNews weekly newsletter