Technical FAQ: All about tubulars
This week, Lennard Zinn addresses questions about tubular tires for off-road riding and cyclocross racing.
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Tubular tire gluing options
Got a question for you about tubular tire gluing. I’m planning on doing a gran fondo next year that involves many miles of tarmac and a few miles of very sketchy dirt, and I’m trying to decide what would be the best tire solution. My old-school brain tells me that a 28mm tubular would be the best performance option. But with the way we glue tubulars these days, if I got a flat it would almost surely mean a DNF, as pulling a well-glued tubular from a carbon rim in the field would be very difficult and overly time consuming. So, my question to you is this: do you know of a tire gluing method that would give the same level of adhesion that we used to get back in the 1970s and 1980s, when we would train on tubulars and regularly swap out tubular tires on the road?
— Bill [related title=”More Tech FAQ” align=”right” tag=”Technical-FAQ”]
Well, you could select glue that doesn’t adhere as well. There are fewer glue options nowadays than in the 1970s and early 1980s, and I remember plenty of them that allowed easy tire removal. Remember Tubasti? That held decently but allowed relatively easy tire removal, and it is still available. I haven’t used it in decades and don’t know if its formula has changed. It also stayed tacky, so if you coated the base tape of your spare tubular with it, you could be fairly confident that it would stay on after a tire change. I think Vittoria Mastik 1 or Continental glue hold too well for easy tire removal and dry too hard to have on the spare tire.
The other thing you could do is use tubular gluing tape. Depending on how much adhesion you think you need (and one variable here is rim width; with today’s wider rims and disc brakes, tire adhesion is improved), you can pick the tape that best meets your adhesion needs and your quick-removal desires. And you can bring another roll of tape along with your spare tubular. It is slower than slapping on a pre-glued tubular, but once you remove the tape (often, the tape comes off with the tire, and if not, you can peel it off after the tire is off), you can put on a new layer of tape, stick on a new tubular, and you’re good to go.
Feedback on ’cross tips for rookies
I have to take issue with this line in one of your recent columns:
Consider tubulars rather than tubeless tires for your race wheels. You will be able to run lower pressures without fear of burping air on corners.
I run Hutchinson Black Mamba tubeless on Shimano RS61 on my CX bike. No issues at any pressure. And I’ve even run them flat after putting an inch-long gash in the sidewall (some things are beyond mere sealant).
It’s fair to say that CX is a bit of harmless fun for me and the RS61s are cast offs from my road bike. But I do see lots of people flatting after picking up a thorn and I ride serenely by. I would have thought that insurance easily offset any small weight penalty.
I understand your perspective, given that you have had stellar results with tubeless CX tires. However, that is not everybody’s experience, and I believe it generally has to do with the rim choice. Furthermore, there is a lot more to the performance difference between tubulars and tubeless CX tires than reliability.
I have been in and seen plenty of cyclocross races in which somebody on tubeless tires came in hard into a sharp corner and burped most of the air out of his or her tire in the turn. I believe that is often the result of using a standard rim with tubeless rim tape. I’ve done a lot of riding on tubeless CX tires at low pressures without ever burping one, but only on two types of rims: tubeless-specific (in my case, a couple of different models of Fulcrum “2-Way Fit”) rims and Stan’s NoTubes rims.
A tubeless-specific rim, like your Shimano RS61 wheels, has a ridge (the “hump”) along the inboard edge of each bead-seat shelf. A tubeless tire mounted on this type of rim is far less likely to burp air at low pressures than one mounted on a standard clincher rim. The hump essentially locks the bead from sliding inward, and it also forms a seal around three sides of the bead, not just two. A standard clincher rim sealed with tubeless sealing tape on it has no bead-retaining hump, is flatter in profile inside, and is slick, all of which tends to allow the beads of a tire at low pressure to slide inward under a high side load and lose air.
Stan’s NoTubes (it’s interesting your name is Stan and you’re a tubeless devotee) rim designs feature a very low internal rim wall — the Stan’s NoTubes Bead Socket Technology (BST), protected by five different patents and licensed to Velocity for some of its rims. I believe that I was never able to burp a tire on these rims because the tire sidewall comes into the top of the rim at a very low angle. On a standard rim with taller rim walls above the bead seats, the tire sidewalls stand up very straight before the tire bulges out above the rim. I think this allows the tire to fold over more easily (and hence be susceptible to burping) than the more rounded tire shape allows on a BST rim.
I also get your point about thorns, since a tubeless tire with sealant in it is largely impervious to them. That said, you can put some sealants (Caffélatex is one) inside of the latex inner tube in a tubular, and it will also be impervious to thorns. I have had personal experience running Caffélatex in tubulars at a race at the Boulder Reservoir where goat head thorns were everywhere, especially in the overflow parking areas; flats were the rule, not the exception, that day, but I didn’t have a single flat despite having goat heads all over both of my tires. I see the main advantage of a tubeless tire as being the much lower rolling resistance due to the super soft, supple casing of cotton or silk tubulars. There has yet to be a tubeless CX tire that approaches a high-end CX tubular in this department. And when glued on properly, the tubular’s cornering performance cannot be matched by a tubeless tire.
Also, running a clincher tire (tubeless or not), at low pressure exposes the fragile rim walls to denting and bending (aluminum) or cracking (carbon). As for running when flat, I think tubulars will generally give you better security — because they’re glued on — than will any clincher other than perhaps a beadlocked tubeless tire like you have with those rims. And see my point above about ruining the clincher rim when you’re running it flat; a tubular rim is much more likely to survive being run flat than a clincher rim.
And yes, the weight of a tubular rim is also much lower than a clincher rim, and this is rotating weight out at the edges of a big hoop, which, in an event involving continuous acceleration, is far more costly due to the increase in rotational inertia than weight on other parts of the bike. Read the last response on the above link about the three Hummers.
I am quite certain that if you were to do some ’cross racing on high-end handmade cotton or silk tubulars on lightweight carbon rims, you would not be eager to go back to your tubeless tires. Of course, there can be a very wide price gulf between these two options, and given that CX “is a bit of harmless fun” for you, you may still prefer the tubeless tires on the old wheels from your road bike for that reason.