Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
As the temperatures drop in North America this week, we’ll focus on follow-up on my October 23 column on cyclocross gluing tape.
Why Mastik and Belgian tape?
On Saturday I rolled a tubular mounted with Tufo regular tape and Mastik.
I’ve been gluing this way with success, but couldn’t believe Saturday night after looking closely I found the same thing your article two years ago describes: a thin plastic layer in the glue on the rim that came off in one piece and another on the base tape. I actually thought I had screwed up and somehow not taken the protection layer off correctly when I mounted.
I just ordered the Belgium tape today, as I need to get it done solidly for this weekend’s Verge race in Sterling.
I have only run a clincher setup for cyclocross and would like to switch to tubs (tubulars). My question is: why is not glue only enough (when done properly)? I have ran Mastik One on my track wheels, riding at ADT Center, thought that those conditions would be tougher on a tire and glue job than ’cross racing would. I don’t know; that’s why I am asking.
Properly done, Mastik One glue can be sufficient by itself, but I remain convinced that greater retention can be achieved by combining the glue with Cyclocrossworld.com’s Belgian gluing tape. The reasons that getting cyclocross tires to adhere in a bombproof way is a tougher gluing job even than for track tubulars are threefold.
Firstly, the ’cross tire is fatter than the rim was made to fit. The radius of curvature of the rim bed is smaller — meant usually for 21mm-23mm-section tires, in some cases maybe as much as 25mm-section tires — whereas cyclocross tires are at least 30mm and usually 33mm in cross-sectional diameter. So, there is a gap under the center of the tire between the base tape and the rim. Gluing tape helps to fill this gap and constrain and conform layers of glue above and below it to better fill that gap with structural material held together by woven fibers. This is much better than a thick bead of glue alone gravitating toward and filling that space and becoming a hard, glassy material that has no structural integrity. It’s like the difference between pouring a concrete driveway with and without rebar in the concrete. The fibers, like the rebar, hold the entire job together.
Secondly, the tire pressures in ’cross are low, which, when combined with the larger tire and consequently higher leverage trying to peel it off of the rim on a turn, put more stress on the glue joint. When you pump up a road or track tire to over 100 psi, it is pulling ever more tightly in toward the rim, increasing the security of the glue job. A cyclocross tire, by contrast, will be run as low as 25 psi or even lower — at the kind of pressure that you normally move a tire around on the rim to seat it straight when gluing it before pumping it up so that it will tighten up on the rim. Furthermore, it’s much easier to knock over something tall than something short; the road or track can’t apply as much rolling-off torque on a skinny little tire as on a big, fat tire.
Thirdly, the mud, water, dirt and foliage that a cyclocross tire goes through will all be working harder on the glue joint than the more pristine conditions encountered on a velodrome or on pavement on nice days.
How many layers, exactly?
So, last question. When you’re gluing the cyclocross tires on to the rims, how many coats of glue total do you end up with on the rims? Three? Or, four? … i.e.,
1. First glue layer on rim: Let dry 24 hours
2. Second glue layer on rim: Then apply Belgian tape
3. Third glue layer: Over Belgian tape
4. Then mount tire right away, while third glue layer is still wet? Or, let third layer dry tacky… and finally add fourth glue layer and mount tire, while wet?
I do two layers on the rim that I let dry completely after each layer. Then I apply a third layer and stick on the Belgian tape right over it. Then I put another glue layer over the Belgian tape and mount the tire right away. That’s a total of four layers.
I should do what to my carbon wheels?
I just read your response to Jon about stripping tires glued with Belgian tape. You said to “dig off the chunks of tape left on the rim with a screwdriver… scrub the rim with a wire brush.” Really? For a carbon rim? (Jon was asking about his Zipp 303s.)
Absolutely. This is all on carbon rims. You still have glue on the rim underneath the globs; you’re not sticking the screwdriver into the carbon. I’m not removing any material from the rims in either method. If you try it, you’ll see. The wire brush is just roughing up and brushing off excess dried-up glue, and then you’re just knocking down the bigger globs.
You can also use acetone or VM & P Naphtha to remove the glue. However, I personally think that if some glue is left well-adhered to the rim, especially on a carbon rim, that I might as well leave it on there as long as it’s not lumpy. It can only help to hold the tire on better.
Sometimes the tape remains very well adhered to the rim and, after much effort, I peel the tire off of it. If the tape is on there that well, I often leave it on. I put a layer of glue over it, let it dry overnight, then apply another layer followed by mounting the tire.
Sweeping your tubulars
You didn’t mention the broomstick step for securing tubulars to the rim.
After getting the tire on the rim straight, you deflate the tire and set it on a broomstick laying on the floor. You then roll the wheel back and forth so that the broomstick presses the base tape into the rim channel, which pushes out air bubbles and promotes a better seal between tape and rim. Laatste Ronde has a good description to better illustrate. I used this method and have had no rolling after 20 races, including the mud, snow, rain and USGP Mercer peanut butter at 28psi for a 6’4″, 185-pound rider (we met briefly at the Munich airport baggage claim in 2008 when you were there for Eurobike).
Keep the tires on!
Yes, I used to always do this, but I’ve gotten out of the habit. I think it’s a good idea.
Shortcuts and a pump trick
I don’t strip my tubulars each season. Once I have them glued and taped, I deflate them at the end of the season. Before the new season, I get them down from the garage loft and run my thumb firmly between the edge of the tire, just where it meets the rim. If there is any lifting of the tire, I use a small tube of Conti or Vittoria glue and just squirt some in. Then, I pump up and leave them somewhere warm for 24 hours. I then check again with the tire deflated and invariably we are good to go. So I would advise always having a small tube of glue as well as a big tube of glue.
Another tip is to put some Velcro tape (aggressive side) and a couple of layers of duct tape on any mini pump that you stick in your back pocket. The Velcro will grip the pocket lining, stopping it from jumping out (especially when ’cross training) and the duct tape protects the pump and can also be used for sidewall puncture repairs inside a damaged tire. This second tip has got me out of the crap twice now.
I always enjoy your column and always respect the views of a fellow ’crosser as we tend to know what’s what.