Glueing tubulars [the tubular thread]

[josephtroppo]

Thank you for replying fdegrove!
Guess I'll just have to remove the tape then.

[11.4]

For my cyclocross tubulars I use to glue a piece of cotton rim tape in the first layer of glue to make the rim bed less hollow for a stronger hold.

Is this something to do with a road tubular as well or will it do more harm than good?

This is basically what Belgian tubular rim tape does. This used to be a more common practice with shallow section rims that had spokes pretty close to the rim bed (and because the rims were so shallow, they flexed radially a bit more and could rub or punch holes in the underside of the tubular. It also helped when various tubular rims had ridiculously oversized holes drilled in the rim bed -- nowadays the holes are barely larger than the nipple head but there were some (mostly Italian) rims that had holes almost the width of the rim bed. There were also some rims that were extruded by folding the initial tubular section over onto the rim bed to create the bed with a groove for the tubular's stitching ridge down the middle. When tires had pronounced ridge, this was a very nice feature, but the folded edges would crack over time and you wanted to protect your tire from the resultant sharp edges.

The general issue is that your rim bed needs to match your tire curvature, or vice versa. If you already own the rims, you have to be selective about tires. If you are buying rims for certain tires (e.g., cross tires or very small diameter tubulars) you need to pick rims carefully. People don't commonly use 18-19 mm tubulars in time trials or track any longer and road tires have gotten wider, so as rim manufacturers have wised up and had to buy new extrusion dies, they've focused on more usable bed shapes within a reasonable range of curvature.

To your question ... I wouldn't bother with it unless you have very problematic deep tire beds on your rims. And even if you do, the most important places to get the glue are along the edges of the bed. The worst situation is when the tire sits on its center seam and the edges aren't glued down because the tire can rock back and forth and pull away from the narrow center glued area, and because the glued area is exposed to dirt and water so it gets compromised over time.

[Kraaf]

The general issue is that your rim bed needs to match your tire curvature, or vice versa. If you already own the rims, you have to be selective about tires. If you are buying rims for certain tires (e.g., cross tires or very small diameter tubulars) you need to pick rims carefully. People don't commonly use 18-19 mm tubulars in time trials or track any longer and road tires have gotten wider, so as rim manufacturers have wised up and had to buy new extrusion dies, they've focused on more usable bed shapes within a reasonable range of curvature.

Yes, and a rim can be too deep, or too shallow. I cannot get a Vittoria Evo 23mm to sit well on my Edge 1.38's (pre Enve). As they're good-weather/race wheels, not much chance of dirt getting in the sides, but still not something I'm happy with. Having said that, after seeing the absolutely perfect job my LBS did in glueing Thomas Dekkers' Dugasts for his attack on the hour, I may just give up on the glue alltogether and have them do it from now on.

[11.4]

Yes, and a rim can be too deep, or too shallow. I cannot get a Vittoria Evo 23mm to sit well on my Edge 1.38's (pre Enve). As they're good-weather/race wheels, not much chance of dirt getting in the sides, but still not something I'm happy with. Having said that, after seeing the absolutely perfect job my LBS did in glueing Thomas Dekkers' Dugasts for his attack on the hour, I may just give up on the glue alltogether and have them do it from now on.

Trackies are usually a bit more obsessive about glue jobs. Doesn't mean they glue up road wheels the same way. And tires for a special one-off event usually get much better treatment than routine jobs. I can criticize myself for that behavior as well. Put the new tire on the rim and pump it up to your operating pressure. You can quickly tell whether it's sitting high on the edges or sitting high in the center. Then apply a couple coats of glue appropriately -- either in the center or along the edges of the bed. If I put a couple extra coats near the edges, I'll take a box cutter and trim the glue at about a 45 degree angle to the top of the rim so I have a nice clean edge (cosmetics, mostly) and make sure it dries really well before putting on the last coat -- otherwise your last coat can make it slide a bit. I generally try to build up the glue itself rather than inserting a piece of fabric into the rim bed. On the track I've had stayer tires pull loose with fabric inserts, and don't want that happening again. (Stayer tires get glued on (usually still get shellacked rather than glued with rim cement) and if you're traditional and careful you wrap strips of silk around the tire and the rim between the spokes so you make absolutely sure the tire doesn't come off. Then shellac the wraps so they stay in place. More and more riders skip the process these days, but for big steyr races in Belgium it's usually recommended.)

[Kraaf]

Thanks,
Though I'm not planning any stayer racing, I love learning this kind of stuff. As for building up the rim, I'll try your approach to it. I have to say that the batch of Mastik1 I have does seem to end up a bit brittle. Where I tried to fill the gaps on the side, the tire just detaches when the tire deflates, even though the central channel holds very well (tires are really difficult to remove from the rim). No fear of the tire rolling, but it can't be optimal in terms of rolling resistance. I did notice that after putting layers on the base tape, the 'v' shape of the tire/base tape gets more pronounced, making it even harder to get a good fit. Again, I've only had this issue with the Vittoria Evo / Edge 1.38 combination.

[11.4]

Thanks,
Though I'm not planning any stayer racing, I love learning this kind of stuff. As for building up the rim, I'll try your approach to it. I have to say that the batch of Mastik1 I have does seem to end up a bit brittle. Where I tried to fill the gaps on the side, the tire just detaches when the tire deflates, even though the central channel holds very well (tires are really difficult to remove from the rim). No fear of the tire rolling, but it can't be optimal in terms of rolling resistance. I did notice that after putting layers on the base tape, the 'v' shape of the tire/base tape gets more pronounced, making it even harder to get a good fit. Again, I've only had this issue with the Vittoria Evo / Edge 1.38 combination.

What you are experiencing is indication of separation occurring in the colloid of the rim cement. I wouldn't use that glue and I'd clean off the glue already on the tire or rim. It won't hold properly and can be very unpredictable. Get some newer rim cement and it should do better.

[Zoro]

Data point. Sometime the most adhesive glue job is not the best glue job.

[Kraaf]

I'll get the white spirit...

[fdegrove]

Hi,

Data point. Sometime the most adhesive glue job is not the best glue job.

Please explain.

Cheers,

[Zoro]

Hi,

Data point. Sometime the most adhesive glue job is not the best glue job.

Please explain.

Cheers,

It is possible to glue a tire significantly beyond what the adhesion of the base tape to tyre is.
I don't see any point in that. If done with lots of love and attention, it is still possible to dismount the tyre leaving the base tape on the tire.
A good glue job minimizes movement on the rim/tyre contact area and makes sure that the glue is not the weak factor in potential tyre roll. Beyond that, it just becomes difficult to replace tyres.
Some brands have more base tape adhesion (to tyre) than others. Exceeding that with base tape to rim seems pointless.

Reason I made my first comment is some mechanics I know go through an almost impossible to remove the tyre without damage, glue job. Too much.

[fdegrove]

Hi,

Some brands have more base tape adhesion (to tyre) than others. Exceeding that with base tape to rim seems pointless.

Exactly. It's always a compromise.

Track usage is a different story but then they often sacrifice the tubular in order to reduce risk of roll off and to reduce rolling resistance to the least possible.

Cheers,

[sungod]

seem to be some confused/extreme positions emerging here, applying the test of reason...

unless you ride tt, tri or on the front in a race the aero differences between wheels in a straight line are negligible, and if you're not racing they are completely irrelevant

vs. a more advanced profile, lw's rim profile does catch more in crosswinds, but at least for me they're ok until winds reach c. 40kph+ and gusty, then i get very cautious, but other deep rims still need care at these wind speeds

i've had two sets (obermayers gen iii and iv) both perfectly true, ymmv, that's my experience, handmade stuff varies, it's no big deal, bikes are crude mechanical things, not lhc vertex detectors

and of course the ultimate decision factor, this is weight weenies, not a tt, or tri or aero site, lw wheels are lighter therefore they are better

[Zoro]

Different tires/glue/pressure for different purposes. Its not just one way for every wheel set. Sometimes that 1 sec does matter a whole bunch and besides the weight - everything matters.
I glue differently for smooth TT roads - run a 24mm 190g Vittoria Crono CS and use different pressure.
I glue differently for dirt/rough - Dugasts PR 25s that measure 26mm and are 350g.
While I would want to go much lower pressure flat spotting is an issue. A 27mm tire is too big for the frame. This is a hard one and the rims are heavier.

I glue differently for RR - run 25 mm FMB silk Competition cx 260g and run different pressure.
I glue differently for training - run Veloflex 23mm Carbons 260g and use different pressure.

[11.4]

I'm not getting where this thread is headed at this moment. Yes, every tire and rim combination needs a glue job optimized for that particular combination -- more or less rim cement required, different numbers of coats due to base tape absorption, etc etc. But in the end, everybody argues how track tubulars are under so much more stress or under so much less stress -- and I don't think most posters have actually raced track tubulars all that much, perhaps other types also. The stress on the tire and the glue joint is different from what one expects, and it isn't about just racing that you worry -- it's when you've flatted, when someone hits your wheel, when you are trying not to go down and need that tire to stay in place, and so on. When actually racing, there are issues as well, but the point is that the model for the ideal glue job, if you want to think of it that way, is much more complex even on the track.

I won't bother to get into what's the most aerodynamic because this is about gluing tires, not optimizing aerodynamics. But if you're racing, it's fair to say that the glue job and the aerodynamics share one issue: everything is fast and the effective wind velocity vector is pointed pretty much right down the centerline of the wheel. This is why so many people can ride with less than optimal wheels and with less than optimal glue jobs and do fine. It's when Joseba loses it and needs to keep his tire on that things turn bad. I hear all the time about how lighter glue jobs are fine because tire pressure holds the tire on the rim, when one really wants to consider the failure mode with no pressure. I hear people talking about centrifugal pressure and centripetal pressure on the track without ever really considering how one steers in real life on the track. Ditto for how one really descends when one can do it fast. Someone really could start a thread on developing a solid comprehensive model for the stresses on a glue joint (and also on a wheel itself, for that matter), taking real life racing into account.

Anyway, after that diversion, my question still stands. Where are these posts headed? What is the point being made? I'm intrigued by the contributors and their perspectives; I just seem to be missing something here.

[Calnago]

There are over 3000 posts to this thread. I guess you have to expect a bit of wandering off the beaten path now and then.