Thursday, November 3, 2011

Q&A: Gluing and Repairing Sew-Up Tires

Today I'm answering a couple of questions about sew-up bicycle tires, also known as tubular tires, and not to be confused with tubeless tires (it's easy to get mixed up!). Sew-ups are special tires used mostly used by road racers and roadies looking for the lightest, fastest, smoothest ride. They're a little fussy to deal with so they're definitely not for everyone. But if you're interested in sew-ups or riding them, this column has some good background and tips.

A little background on sew-ups
"Sew-up" tires are sewn together around the tube
Before I get into the QandA, here's a little basic information on sew-ups (sometimes called "tubs," too) for those new to them. Sew-ups have been around since some of the earliest bicycles. Today, these special tires are most closely tied to racing and performance riding.

Benefits
This is because the construction of sew-ups and the special sew-up rims required, provide a truly round tire profile, that many riders feel offers superior cornering and a significantly more compliant ride (less shock to the rider = more energy throughout the race and quicker recovery, too). You can see the round profile on this photo showing a cutaway end view of an old tire.

Even more important to some riders is the weight savings provided by less material in the rim due to its simpler profile, and the lighter tires available (since the closed design of sew-ups allows the use of lighter tubes and casing materials with less risk of flats).

Also a significant advantage, you can inflate them to extremely high pressures for racing on super-smooth surfaces like some velodromes (cycling tracks), or on the other extreme, for racing like cyclocross where traction is all important, you can run them at low pressures and not risk pinch flatting). For some of these reasons there have even been mountain bike sew-up rims and tires.

Sew-up tires require sew-up rims and glue
Understand though, that sew-up tires are only for use with sew-up rims. Unlike clincher rims that have upright walls on either side so that they can hold onto the sidewalls on clincher tires so the tires stay on when inflated, a sew-up rim is a closed section, like a box, and the top surface is flat and curved to perfectly match the curve of the sew-up tire profile.

Sew-up repair is a little tricky
Since the sew-up rim does not have sides to hold onto the tire, and because the tire has no sidewall to hold onto the rim, the way sew-up tires are attached is with adhesive (glue or tape). Having to glue the tires on, and having to perform minor surgey to fix them if you puncture (photo) are the reasons most roadies today ride clincher tires and more riders don't use sew-ups.

Interestingly, the newest tire, the tubeless is gaining popularity because its ride feels similar to sew-ups. Yet, because it's just like a standard clincher tire, except made not to require a tube inside, there are none of the gluing or surgery-to-repair hassles of sew-ups.

The sew-up questions that follow allow me to go over some common issues with repairing and installing and removing sew-ups, the two biggest hurdles with these tires.

FYI: All of my regular and training rides are done on clincher tires. On race days I usually use my carbon wheels with sew-up tires because I believe they're advantageous.

Q: Hi Jim,
I recently started riding again after a 20-plus year layoff. Here's a little equipment background: I have a Bianchi Reparto Corse-built SLX frame with Campagnolo C-Record and Campy Record Strada tubular wheels.

Two days ago I flatted a Vittoria CR sew-up and it took 3 of us and what seemed like 20 minutes to roll it off the rim. I'm used to being able to do this by myself without too much effort. The tire, which was new, had only been on there two weeks, w/Vittoria clear glue. If I had been by myself, I don't think I could have gotten it off. What did I do wrong, did I use too much glue?

I used about 3/4 tube between the wheel and the new tubular. On the wheel I applied one coat, waited 45 minutes, then a second coat. On the tire I only applied one coat - went away for about 4 hours came back and mounted the tire, inflated it and rode around the block to set everything.

What do you think? I'd like to learn how to do this properly and avoid that kind of herculean effort in the future. I read your article on installing tires and don't see where I deviated too much.

Appreciate your help,
Jon

A: Welcome back to riding, Jon! There’s no way to really satisfactorily answer your question because it’s an age-old issue with sew-ups. Basically you have a choice: 1. Glue them on good and tight so they’re as safe as possible and there’s little chance of them coming off when you’re riding. Or 2. Use a little less glue so that they are easier to get off and take the risk that they might come off when you’re riding.

From what you wrote it doesn’t sound to me like you used too much glue. It just sounds like a good glue job. To me the most important thing is to make sure the tires won’t budge when you’re riding. And these days with carbon rims, tires stick even tighter than they did with aluminum rims. So it’s actually getting harder to pull them off if they’re glued on nicely.

But with any rim, I would expect to have to wrestle to remove a tire. If it came off easily I’d be concerned that it would come off in a corner. Of course, the older the glue job is, the looser it may become making it easier to remove the tire. But a new, good glue job should be really tight.

Vittoria Pit Stop sealant
So what some riders are doing is using sealant in the tires and carrying sealant inflators to fix flats on the road so that they can then remove the tire at home if it ends up flatting again. The one I’ve used is made by Vittoria and called Pit Stop. It’s about the size of a mini pump so you can carry it in your jersey pocket. There's even a bracket for it so you can carry it on your frame like a mini pump, too.

Another approach is to carry tire levers to help get tires off, but riders with carbon rims want to use them carefully. It wouldn’t be too hard to damage a carbon rim if you were too rough with the tools. And it can be a struggle to remove a tough tire even with tire levers.

You could also experiment with other gluing “tricks” such as using tape glues instead of liquid glues. I’ve never tried them but I’ve heard some mechanics say they work fine. And in theory, they might act as a release strip when you’re trying to peel off a tire.

Tufo Gluing Tape Tufo is one such product. I put their video showing how it's used below. It looks like a nice alternative to glue that I need to try. This article also provides some excellent tips on using gluing tape - some not shown in the video.

Ultimately, though, I would say you know how to glue tires just fine, so I wouldn’t worry about that part of it.

To no more tire trouble,
Jim


Q: Hi Jim,
We exchanged some information on sew-up tires a while back. I thank you again for your valuable insight which I've put it to good use. Since our correspondence I've laced a pair of 36-hole vintage Aspin rims with 2mm spokes, using Campy Record hubs and 3x pattern. It all went well. I installed a pair of Continental Sprinter tubulars.

The gluing job so that the mounted tire wouldn't move off the rim took several attempts but overall I was happy with the results. After about 100 miles, I had my first flat on the front: a 3mm horizontal cut on the tread. I used Stan's sealant which didn't work at all. I slowly rode back 2 miles on a completely flat front tire - this alone may have compromised the inner tube.

My first attempt to repair the sew-up was a complete failure. I'm not sure what went wrong. I opened the stitching of the base tape, opened the inner stitching (noticed this was lightly sewn with finer thread). Used a Park sticky patch that doesn't require glue. I also used a Park boot patch on the inner tire casing wall. The inner tube held the pressure well.

I used a sewing awl with curved needle to stitch the inner casing. Continental uses stitching for the liner tape. I used a fine waxed thread for this [editor's note: some tires have a strip of cloth between the bottom of the tube and tire]. I glued the base tape back in place.

I next mounted the tire on a spokeless rim to stretch it. I inflated it to 20 psi and everything seemed fine. But, as I pumped, going over 120 psi, I noticed the repair section of the tire was bulging and ballooning. Before I could relieve pressure with the valve, it exploded like a gunshot.

The inner tube must have worked its way out of the inner casing, which is puzzling because I stitched the inner casing tighter than the original pattern which was spaced out more. The inner tube exploded next to the repair area, a longitudinal section 2-3 inches along the stitching. I'm suspecting the waxed thread may have been too rough chafing the inner-tube at higher pressures. But I'm not sure.

I'd be very happy if you can comment on what I might have gotten wrong. In the meantime I'm going to ride my clincher tires. I'd be interested in what tires you ride, Jim.

Regards,
Mike
PS: Next time I may use a sew-up repair business called Tire Alert in Florida. They have very good customer feedback. I read accounts that they install a higher quality base tape than most manufacturers. They charge $22 per sew-up repair which includes new inner tube, base tape and free shipping on the return. A removable valve core and new Presta valve is $25. They offer discounts if you have more tires to be repaired. They take credit cards and PayPal. If you are interested their address is:
Tire Alert
2320 Hawthorne Dr
Clearwater, FL 33763
800-735-5516
Please let me know if you're aware of any other sew-up repair services.

A: Sorry to hear of your sew-up trouble, Mike. I save my Vittoria sew-ups for racing and log most of my miles on clinchers due to the frustration of flatting an expensive and time-consuming to fix tubular. I ride on Continental Grand Prix 4000 clinchers in 700 x 23c and they fit in any road frame just fine and ride great and are highly flat resistant.

I also ride a fair amount on Dura-Ace tubeless clincher wheels with Hutchinson Fusion 3 700 x 23c tubeless tires that almost ride as nice as sew-ups. Both these sets of tires are easy to fix flats on by simply popping in a spare tube. But, I’ve had very few flats with these tires. You can buy the 4000s at any bike shop. To use the Hutchinsons you would want to be on tubeless rims or convert your rims to tubeless.

On fixing sew-up tires, it’s not always easy to figure out what went wrong when something does. Reading your email I wondered if you marked the original casing stitching (see photo below) before you cut it so that you could run your new stitches in exactly the same place and in exactly the same angle as the original stitches?

That’s very important since the tire is stitched a certain way at the factory so that the stitching doesn’t change the shape of the tire or interfere with the tube. If you stitch it wrong during a repair you can put an S in the tire casing and the stitches may work loose.

It's actually not easy to line the holes up right once the original thread has been cut and pulled out of the holes. If you mark it first, before cutting, you'll have guidelines to follow and always get the restitching right.

Also, I wondered whether the base tape was glued down well enough after your repair. Usually they glue it down with a liquid latex glue at the factory and that helps seals the stitches in the casing. Maybe if you didn't get it to stick fast, it was able to lift.

You mentioned using a Park glueless patch, which I wouldn't have done because they are best used for emergency flat repair on a mountain bike with low pressure tires. When going to all the trouble to operate on a sew-up I would always use a proper self-vulcanizing patch that uses glue to becomes part of the tube and create a patch even stronger than the original tube.

Overlap the factory stitching on both ends
But, from your description of how the tire exploded, my best guess is that the stitching next to your stitches may have let go, letting the tube poke out and explode.

You always want to run your repair stitches so that they run over the factory stitching for an inch or so on both sides to prevent this. That's because those stitches become loose when you cut the adjacent stitches. Maybe that was the issue.

As you can tell, there's a lot to learn about fixing sew-ups. A good quick resource is cycling technical expert Jobst Brandt's article. There's also a nice step-by-step repair article on the great bicycle shop Yellow Jersey's website.

I don't know of any other sew-up repair services for you. Perhaps we'll receive some suggestions from readers. But I have heard of Tire Alert. They say they've been in business for 15 years, which is impressive. Sometimes bicycle shops repair sew-ups so if you need it done quickly, you might call around and ask.

If you decide to fix any more sew-ups yourself and you follow all these tips, I think your repairs will hold up fine,

Jim

4 comments:

ann said...

r.e. removing sewups: carefully push 6"long screwdriver to other side under tire, pull directly up one side at a time to release rim tape, slide screwdriver toward yourself one side at a time, repeat, until all glue separated. Takes five minutes. R.e. marking holes for new sewing, buy a 3.50 pair of reading glasses, pinch both sides together and cross stitch diagonally through existing holes like a shoelace.

Jim Langley said...

Thanks for the tips, Ann. You have to be super careful working on carbon rims with metal tools. Plastic tools are less likely to damage anything but even with them you have to be careful. Something like a wooden spoon can be made to work, as one idea. I don't quite understand how you are saying to use the reading glasses, but I would emphasize that whenever and however you stitch up the tire, one of the most important things is to be sure the stitches hold the two sides of the tire at exactly the same orientation they were in when you opened it up. That's why you should draw lines on the tire stitches first so you know exactly how to line them up. If you don't do this and you stitch through the wrong holes left/right, you end up like you do if you button up your shirt with the buttons in the wrong holes: your repaired tire will have a bend in it and it won't roll right down the road and you'll see this as soon as you put air in the tire. Just wanted to explain a bit more so people don't run into these problems. Thanks for your tips!
Jim Langley

Chip said...

Hi

I have a perfectly good Conti Sprinter tire that has a circular tear around the valve -- so the inner tube is no good. I took the tire apart, but as it turns out the inner tube size is quite a bit smaller than a standard 700c inner tube for a clincher. The circumference is probably 4-5 inches smaller than the 700c tube.

I didn't realize this when I started; is there another inner tube size that I should use (650c?) or is it possible to buy an inner tube for a sew up?

Thanks & thanks for your blog...

Pete

Jim Langley said...

Hi Pete,
You said you took the tire apart, which is not the easy way to replace a bad tube, if by take it apart you mean you completely unstitched it. The way tire repairers do it - and how I did it is by just cutting the tube and then pulling it out of the tire through the hole. You then start with whatever tube you want and feed it into the tire through the hole and then splice the tube back together again. That way, you size the tube as part of putting it into the tire and even if it's long it's not a problem. It's easier to do this with latex than butyl tubes since the glue sticks better. To do it you put one end of the tube over a mandrel to stretch it and remove wrinkles, like the flat end of a ballpeen hammer. Then you take another hammer and manipulate the other tube so that it's rolled back over the ballpeen hammer once and then back over itself. Now you have both ends of the tubes with no wrinkles held on the hammer mandrels. Put glue all around the tube ends and let it dry. By putting the hammers close to each other and rolling the tube end over onto the other tube end, they will stick tight, wrinkle free and you'll have a perfect airtight new tube. It's not as difficult as it sounds and you then only have to stitch up a small hole in the tire. Stitching up the whole tire is hard to get right. I've never tried to do that. I hope this helps. Sorry for the long explanation. In cycling and sewup repair, Jim Langley