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I ride a hybrid (Trek Fx 7.3) as a daily commuter and have found a 143mm saddle to be the right width for me. However I am looking into getting a road bike for long rides and am finding 130mm saddles seem a bit more comfortable on them.

Since I am new to road bikes, drop bars, and the lower position I am having a hard time telling if the better fit is all in my head. Would it make sense that the more aggressive stance on a road bike would result in your sit bones effectively being closer together than the upright stand on my hybrid?

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Yes, a more aggressive stance requires a narrower saddle.

Your pelvic bone is a fairly complicated structure, but there's basically a triangle that you sit on with a saddle. There's two bumps ("ischial protrusions") at the back end that take your weight if you're sitting with your back straight up (such as on a chair or the saddle of a cruiser or dutch bike). The front point of the triangle is the "pubic symphisis" which you don't sit on. Between there it's basically slightly curved like the bottom of a rocking chair.

Look here: http://en.wikipedia.org/wiki/File:Gray237.png
Here: http://en.wikipedia.org/wiki/File:Gray235.png
And here: http://en.wikipedia.org/wiki/File:Skeletpelvis-pubis.jpg

As you rotate your hips forward (for a more "aggressive" position), your hips should be rotating forward and your back staying relatively straight. Because of that, the part of that ischial/pubis structure that you sit on is more towards the narrow front part and the saddle should be narrower. This can also affect the desired tilt of the saddle.

Also, in general, if you're riding more aggressively, all that pedaling removes some of the weight from the saddle and makes any kind of rubbing against the saddle more of a problem, which are additional reasons aggressive road riders may want a narrower saddle.

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  • Agreed! I prefer wider saddles for lower bike speeds. For a sporty one, specially if I'll have to "race" with myself or to catch up with others, a narrower saddle gives you more freedom to move and to accelerate.
    – heltonbiker
    Oct 5, 2011 at 13:07
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There are some very good answers on here that go part way to explaining why there are something like 2000 saddles on the market.

You did not mention whether you dress up for your daily commute with padded cycling shorts, however, your hybrid bike is designed for more general use, i.e. jeans and T-shirt, not the padded shorts. Hence it has a padded seat and a chainguard (to keep your jeans out of the chainset).

Meanwhile, the road-bike is designed for riding with the padded shorts (although you can probably get back from the pub on it with your jeans tucked into your socks perfectly fine, even if you have had a few and take the tow-path route back with no lights, ahem.)

You also did not mention what build you are. We all have physical differences, some people have bigger bones, some people have more natural padding.

Taking the other (very high quality) answers into account, I would suggest going for the narrow seat and investing money in quality padded shorts. Affordable-style shorts will not do, get the deluxe ones and make sure you follow the wash instructions to the letter.

It is also important to get the setup right. You cannot go far wrong with putting the seat (any seat) so that the top is completely level and in the middle of the saddle rails. Then, over time you can fine tune that setup, to make sure you are not repositioning yourself, continually slipping off the front and so forth. Pointing exactly forward is also a detail to get right. An expensive, top-end seat that is setup wrong will give more grief than a seat that is setup as just described. (You should take this into account when choosing your dream-road-bike as some bike shops have nice bikes with seats tilting weirdly and this can put you off the bike as a whole.)

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  • Thanks for expanding the answers--I just had the chance to pick the brain of a true guru (he also sold me a road-bike, whoops!) and he corroborated your advice to a great degree.
    – STW
    Jul 2, 2011 at 22:23
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A significant factor is that the narrower saddle results in less friction on the inside of the legs -- important when you're riding for hours in a relatively fixed position, but less so when riding for shorter periods or in conditions where you're shifting positions frequently.

Likewise, the wider saddle provides more support when you're shifting positions frequently but is unnecessary when you ride in a fixed position.

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Depending on your riding position on the road bike and the commuter bike, you will need up to 4cm wider seats on your commuter bike.

Ask a friend to take a picture of you sitting on the bike, and review the picture, to determine your sitting position.

See my answer here for the details with pictures: Sitbone width recommendations from SQ Lab

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