Seatpost - Setback or not?

[Tom boyd]

Building up a cross bike and it is time to shop for a post. Leaning toward Thomson Masterpiece or USE Alien TI.

Should I go for the Thomson w/setback or Alien w/o setback? Both are about 155 g.

[Arsbars]

Well setback has to do with your fit. The fore/aft of your knee to the spindle of the pedal.

[Lectron]

Building up a cross bike and it is time to shop for a post. Leaning toward Thomson Masterpiece or USE Alien TI.

Should I go for the Thomson w/setback or Alien w/o setback? Both are about 155 g.

I don't think the Thomson gives you more setback than the USE (that actually has some setback)

[mgwadz]

Building up a cross bike and it is time to shop for a post. Leaning toward Thomson Masterpiece or USE Alien TI.

Should I go for the Thomson w/setback or Alien w/o setback? Both are about 155 g.

It depends on you body dimensions, your bike geomeotry, and your desired fit (such as knee over pedal spindle, set back 2 cm, etc...)- there is no generic answer

marc

[ZenNMotion]

Just my opinion, FWIW (mebbe not much). Assuming you are racing cross (using it for commuting, touring etc is a different story...) you want to be set up for as much power and speed as possible. This is different than setting up for long distance comfort and efficiency. You want to maximize the power from your quads. So you want your seat to be positioned further forward relative to the BB. Cross bikes designed primarily for racing have somewhat steeper seat tube angles and small "setback" than touring or many all-rounder road bikes for this reason. Setback as part of frame design here is the distance between the center of your seatpost to the imaginary vertical line drawn through your seat cluster. More setback = more use of hamstrings and glutes, less quads. More efficient, but less high end power. Think spinning vs. big gear stomping. Classic stage-race road bikes are designed that way. In fact, you can have a clue about how a frame will fit and feel to you just by measuring the setback distance, and compare it to a bike that's familiar to you- no need to know seat tube angle. By the way, you should also consider this factor, and not just the top tube length when choosing a cross frame. Different "cross" bikes have different setback, some really have touring bike geometry and some are even steeper than road race bikes, and the right top tube length for you can vary by a few cm's accordingly, so beware when buying a frame/bike through the mail, as there are more variations with frames sold as "cross" than stock road bikes. Crit bikes, and cyclocross bikes (designed for racing, I'm not talking Surleys and other all-rounders) have minimal setback- built for power and speed, not comfort and efficiency. So choose your poison- in general frames (except maybe tri and time trial bikes, which I think actually have NEGATIVE setback sometimes- and something about saving the legs for running in tri's) are designed for straight seat posts with no additional setback. Unless you know that you want to change the position intended by the frame designer (whether Richard Sachs or Giant, inc) I would go with the straight post, as your better bet. In general, I don't get why someone would buy a setback seatpost unless they have atypical body dimensions on a stock frame, or want to make a steep race bike into more of a tourer, or have the wrong size frame, or are just clueless about position. Just my opinion, sorry if I miffed anyone with a setback post.

[dlbcx]

Just my opinion, FWIW (mebbe not much). Assuming you are racing cross (using it for commuting, touring etc is a different story...) you want to be set up for as much power and speed as possible. This is different than setting up for long distance comfort and efficiency. You want to maximize the power from your quads. So you want your seat to be positioned further forward relative to the BB. Cross bikes designed primarily for racing have somewhat steeper seat tube angles and small "setback" than touring or many all-rounder road bikes for this reason. Setback as part of frame design here is the distance between the center of your seatpost to the imaginary vertical line drawn through your seat cluster. More setback = more use of hamstrings and glutes, less quads. More efficient, but less high end power. Think spinning vs. big gear stomping. Classic stage-race road bikes are designed that way. In fact, you can have a clue about how a frame will fit and feel to you just by measuring the setback distance, and compare it to a bike that's familiar to you- no need to know seat tube angle. By the way, you should also consider this factor, and not just the top tube length when choosing a cross frame. Different "cross" bikes have different setback, some really have touring bike geometry and some are even steeper than road race bikes, and the right top tube length for you can vary by a few cm's accordingly, so beware when buying a frame/bike through the mail, as there are more variations with frames sold as "cross" than stock road bikes. Crit bikes, and cyclocross bikes (designed for racing, I'm not talking Surleys and other all-rounders) have minimal setback- built for power and speed, not comfort and efficiency. So choose your poison- in general frames (except maybe tri and time trial bikes, which I think actually have NEGATIVE setback sometimes- and something about saving the legs for running in tri's) are designed for straight seat posts with no additional setback. Unless you know that you want to change the position intended by the frame designer (whether Richard Sachs or Giant, inc) I would go with the straight post, as your better bet. In general, I don't get why someone would buy a setback seatpost unless they have atypical body dimensions on a stock frame, or want to make a steep race bike into more of a tourer, or have the wrong size frame, or are just clueless about position. Just my opinion, sorry if I miffed anyone with a setback post.

This is how my cross bike is setup; much more forward than my road bike. Also, I wouldn't recommend such a light post since they may not stand too many remounts without breaking. Finally, from my experience from racing cross, is that you do crash so the components need to be tough...as someone once told me, if you're not crashing then you aren't going racing hard enough!