Technical FAQ: The benefits of silk tubulars

Lennard Zinn talks about his experiences with silk tires and explains why they're often smother than cotton ones.

Dear Lennard,
I have long heard of silk casings for high-end track tubulars, but it seems that silk casings have begun appearing (or reappearing?) on road and cyclocross tires as well. Challenge, FMB, and Dugast now offer silk for all three types of tires. As someone who races cyclocross and track on an indoor velodrome, I am curious about the advantages silk casings offer over high TPI cotton for these various conditions. Is it lower rolling resistance, lighter weight, increased suppleness, or just myth?
— John

Dear John,
As someone who raced in the early 1980s on Clement Criterium Seta and Criterium Seta Extra tires (“seta” is the Italian word for silk), I can say from personal experience that there is definitely a difference on the road. The closest comparable tire at the time was a Vittoria cotton tubular; it was a very nice tire, but it didn’t roll or corner (on dry pavement) as well as the silks. At the time, Clement and Vittoria tires were still being made in Italy.

If memory serves, the Criterium Seta was 250 grams, and the Criterium Seta Extra was 220 grams (both in 700 X 23C). I did switch to cotton tubulars for racing in the rain because they seemed to offer better cornering traction. Also, a long day in the rain was very hard on natural-fiber tires, and I preferred damaging a less expensive tire.

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I very clearly and fondly remember the performance of Criterium Setas. They were just so smooth and fast! I remember vividly how good those tires felt in 1980 when I dropped my breakaway companion on the descent into Silverton of the Iron Horse (Durango to Silverton) Classic. I have no idea what tires he was riding, but we hit a section of dirt where the road was being repaired on the very fast descent. I just took off through the dirt on those silk tires, and I felt completely confident of traction and very fast on the bumps and gravel. I passed the lead vehicle and then only had the police escort ahead of me. He was doing four-wheel drifts and squealing around the corners in order to stay ahead of me. I won the race, held the course record for a couple of years, and wish I still had those tires.

I quit road racing in 1983. When I picked up road and cyclocross racing again decades later after my kids were adults, silk tires were no longer to be found. I have had wistful conversations about them with people, and they looked at me like I was some sort of dinosaur. I think their attitude was, “If they are so much better, why would they have stopped making them?” I don’t have an answer for that.

However, they are better. A couple of years ago, I got my hands on a pair of Challenge silk cyclocross tubulars. It was just as I remembered — they were noticeably softer and faster than any other ’cross tire I had ever ridden, particularly on bumpy sections. The cornering grip on dry tracks was also definitely improved. I was comparing them with Challenge Team Edition and Dugast tubulars, which are great, supple cotton tires with a super-thin casing. I had been racing on them for years.

I just got some 700 X 30C Challenge Strada Bianca Seta Extra tubulars that I’m eager to try but have not yet mounted. I have only used the Strada Bianca in an Open Tubular before — not a full tubular, so it won’t be a completely fair test. I can’t wait to ride up Fall River Road (dirt) in Rocky Mountain National Park and then descend Trail Ridge Road (paved) from 12,000 feet on them. That is always a great test of a tire’s speed and versatility.

I didn’t hear back from Dugast about your question, but here is some feedback from François Marie, the owner and namesake of François Marie Boyaux (FMB), and Morgan Nicol of Challenge.

Get some silks.
― Lennard

From FMB:

Silk is a material which has three advantages and a disadvantage. It is superior to cotton for its lightness, its strength, and its solidity. Its problem is price.

It is equivalent to carbon and aluminum; carbon is more expensive than aluminum but superior for its qualities.

Forty years ago, the reference of the tubular tires was the Clément SETA Critérium.

A silk tire is very pleasant to ride. In France they give the name of whistler, which means with good legs, he hears a sifting on the road.

The silk tubular is also very accurate in the touchdown, you have the sensations that are very well transmitted. It’s like walking barefoot.

Silk is now essentially used for TT (The last Olympic TT title was obtained with silk tubular tires). Silk should be used frequently on the roads for its comfort; after six hours of racing it is important that the rider is in the right conditions without pain in the shoulders, neck or lumbar region. I advocate silk tires over long distances for flexibility and comfort. For a small criterium too, it is very effective for nerve accelerations.

We obtained performance tests at seven bars of air pressure; the silk was 12 percent superior to our cotton tires (on this test, our cotton tires were superior to other cotton tires, but is not possible to publish).

My feeling is that this type of tire is still current. The tire is an important item of equipment, like wheels. Riders buy wheels that cost fortunes, and it makes no sense not to mount tubulars of the same level on these wheels.
— François Marie

From Challenge:

Basic physics at the rubber/road interface means that with a softer and more supple tire system, rolling resistance is reduced and impacts passed through the wheels, frame and fork, etc. are also reduced, causing less rider fatigue and keeping the tire on the road, improving braking and cornering rather than bouncing. This is especially true with modern carbon fiber road frames, forks, and wheels that are super light and stiff to provide superb power transmission but very little shock absorption compared to traditional aluminum or steel or titanium frames, forks and wheels.

A vulcanized nylon and butyl rubber tire and butyl rubber inner tube (99 percent of the bike market) will bounce like a playground ball when impacting the smallest road or trail imperfection. That pushes the bike backwards, requiring more power (to overcome rolling resistance), and upwards, lifting the bike off the ground (compromising control) and sending shock waves up to and through the rider (causing fatigue).

A softer, more supple tire system with a high-thread-count polyester, cotton, or silk casing and a latex inner tube will absorb those road or trail shocks to reduce rolling resistance to enhance control and reduce rider fatigue. This is why every professional cyclist in every segment of cycling — from track to time trial to road to cyclocross (and even four of the past five MTB world champions and the Olympic MTB gold medalist in Rio de Janeiro) used this construction of tire system. The system is also more durable and safe.

When you compare polyester, cotton, and silk, you can think of the t-shirt you are wearing. First, you would never wear a nylon t-shirt, especially one soaked in butyl rubber. A polyester t-shirt looks good and is less expensive than cotton or silk, absorbs less water, and is pretty durable, but it is not very soft or supple (comfortable) next to the skin, like cotton or silk. A cotton t-shirt is usually the best compromise of comfort and cost. It is softer and more supple than every fabric except silk, so it feels great next to your skin, but it absorbs water, it stains, and requires gentle washing and drying and a special treatment (like Aquaseal or our special S-series factory sealing) to keep it dry and protected from rot.

Silk is the finest fabric commonly associated with the most expensive lingerie, suits, ties, shirts, and scarves. It is the strongest natural fiber except for spider web (and unfortunately, we can’t get spiders to play well together to harvest this fine option). It repels water and holds dyes very well. A silk tire delivers incredible comfort to a cyclist.

I must confess that I find it hard to believe one can feel the soft supple difference of silk on a 22mm track tire inflated to 12 bars on a polished-smooth, Siberian-hardwood track, but our friends at British Cycling swear there is a difference between silk and cotton.
— Morgan Nicol
Challenge Handmade Tires

Gluing tubulars with Gorilla Glue

Dear Lennard,
Is Gorilla Glue OK for re-gluing tubular rim tape? I don’t want a 3M Fastak issue like in the ’80s.
— JD

Dear JD,
Do you mean tubular base tape, not tubular gluing tape that is used in place of rim cement (tubular mastic)? If it’s the latter, I’m sure it’s a poor idea. If it’s the former, then I don’t know. I know Barge Cement works well for re-gluing the base tape to a tubular. I always used that when I used to patch my own tubulars.
― Lennard

Follow-up on storing bikes upside down

Dear Lennard,
I always enjoy your column. I read your June 13, 2017 column that recommended not storing bikes equipped with hydraulic brakes hanging upside down. How about vertically on the wall hanging by either front or back wheel? I’m hoping it’s OK, as I have limited floor space in my garage.
— Kimball

Dear Kimball,
Hang it by the front wheel so the lever is above the caliper.
― Lennard