Tandem Cycling - Tire Cord Breakage

I think we broke the cords in both our front and rear tires last weekend. Both tires have a bulge in the sidewall. The rear tire has two bulges about 120 degrees from one another. There is no damage to the tread in either tire. We completed the ride and did not notice the front bulge until starting a ride the next day. We did not notice the rear tire bulge until another rider commented on the rear tire during the ride. I'm assuming we must have went over a nasty pothole. Am I correct? We inflate the tires to 135 psi. Their maximum rating is 165. Would we be better off to lower the pressure?

I think I would change tire brands before I went on another ride.

Assuming they're the tires I think they are and they don't have a lot of miles I'd contact the US distributor / importer (Veltec) and ask for warranty replacements. I've had a couple tires over the past 10 years that went out of round for no apparent reason. I contacted their US rep via Email to report my problems and they were really good about sending out replacements. I've also had no problems returning a defective tire via my LBS for a warranty replacement tire.

To your original potential prognosis, you would have noticed a pot hole that was bad enough to damage both tires and I'd recommend keeping the tire pressure in the 135psi - 145psi range if you end up with replacements.

+1 - sounds like a faulty tyre. I went through a batch of cheap vittorias on my single bike that would bulge after one turbo trainer session.

My rule of thumb nowadays is to use the best quality racing tyres and tubes I can afford, since it's about the cheapest way to upgrade the performance of the bike, plus if you save falling off once by having stickier rubber, you've easily saved the extra cost of the rubber both in stoker confidence and in ripped clothing.

Sometimes it's just a batch of lousy tires (quality control issue).
If you hit a pothole nasty enough to bulge out both tires, you and stoker would certainly have felt it and you'd be re-trueing both wheels!

Sometimes it's just a batch of lousy tires (quality control issue).
If you hit a pothole nasty enough to bulge out both tires, you and stoker would certainly have felt it and you'd be re-trueing both wheels!

The wheels are fine so I guess I just got some defective tires. I'll follow TandemGeek's advice and send Veltec an email.

Were they Vredestein tires? I had a bad batch with similar problems to yours, that I returned. I changed to the Continental GP-4000's. Their quality seems better. Vreds used to be a better tire IMO when they were made in Holland.

Were they Vredestein tires? I had a bad batch with similar problems to yours, that I returned. I changed to the Continental GP-4000's. Their quality seems better. Vreds used to be a better tire IMO when they were made in Holland.

I use the GP-4000s on my single bike. However, they have a maximum pressure of 120. Do you use a higher pressure on a tandem?

Yes, I pump the GP-4000 to 125 psi on the tandem. I'm using 700x25mm on the tandem. I use 700x23mm on singles with 115-120 psi.