When people speak of bicycle frame sizes, they generally speak in terms of the seat tube length.

人们谈到车架尺寸时，通常是按照立管尺寸来计算的。

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Once the bike's seat tube forms a lock, the only way to steal the bike would be to cut through it, destroying it in the process.

一旦自行车车座杆形成一把锁，偷车的唯一办法就是把车切开，这样做的话自行车也就毁了。

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Our factory specializes in producing three types of polypropylene PP-R pipe, fittings, tube cards, debit seat tube and other products.

本厂专业产三型聚丙烯PP-R管材、管件、管卡、管扣座等产品。

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So when I got my custom bike, I told Seven Cycles this and they built in an oversized seat tube to add rigidity for my standing pedal stroke, an efficiency increase.

FORBES: Why You Need a Custom Road Bike

The bike is a beauty: red and black, with flames painted on the down tube and seat.

WSJ: Cycling: Jason Gay: The Last Big Wheel of NYC