I looked around the internet to find any evidence of the effects of tire liners on speed, but couldn't find any. I was considering using them while touring. So, I did my own test.
My bike is a mid-range steel framed tourer with Schwalbe 26" x 1 3/8 Delta Cruisers. The tubes are Bontrager. I installed the liners as per instructions and took the bike out for a spin. It was like riding through treacle. I wasn't carrying panniers and luggage, but it felt the same. I thought I had fitted them ok and therefore was at a loss as to how these really light nylon liners could have the effect of a fully loaded bike, but worse.
So, the next day, I thought I'll try again - maybe it's just me. I'll take the bike on a training route I use a lot. Here are the results: 24 kms., 16.1 kph average, 1 hour 30 min.
And I didn't enjoy it. My bike had turned into a turkey overnight.
Next morning, I headed out again on the exact same route (no traffic lights, country roads, no hills) without the liners, same tire pressures. What a pleasure - lovely ride, responsive, gliding. Results: 24 kms., 20.3 kph average, 1 hour 12 min. That's a 25% difference in speed and time. And I would need a flat every 20 kms. to make up the difference. Hard to believe, isn't it?
When I examined the liners they had turned black,, on both sides, from bright orange, which I assume was from the tire and tube rubbing on it. It had also stuck to the tube in one or two places, necessitating me to peel it off. I will never be using them again. It would be interesting to hear of any other people's research into tire liner use. Is this just a one off? What about thick tubes and reinforced tires? How do they affect performance?