Seat Tube Angle Advice



mjschof

New Member
Mar 30, 2010
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For the fit experts out there... take a look at the geometry of this bike:

Schwinn: 2009 World Tour DLX

It's theoretically a touring bike, so you'd think it would be built for a relaxed ride, but the seat tube angle in the smaller sizes is in the steeper end of what you see out there. Compare it to to Riv, Surly, and other "lower end" road bikes relaxed geometries, which are in the 72-73 in the fiftysmall cm sizes.

I have one on order from Performance at a steal of a price ($500, returnable if the fit isn't right), but am wondering if it's just too far out of the ballpark for a good ride. I'm new to road biking, transitioning from a Target mountain bike, and trying to start out on a smaller budget. Typical use is communting and training for the STP classic (Seattle-to-Portland)

Thoughts?
 
As far as the seat tube angle, 76º is really steep, but it really only matters if you can't locate your saddle relative to the pedals the way you want to ...

Do you know the seat tube angle on your current bike?

How far fore-aft is your saddle currently located in your current seatpost's cradle?

How much set back does your current seatpost's cradle have?
 
I think you're premature in getting concerned - you haven't even mounted/ridden the bike yet. Further, I'm no "expert" but I hope don't mind me chiming in anyway...

As mentioned, you only need be concerned with the getting your saddle position, relative to the bottom bracket, in the ballpark of your current ride. Moving your saddle aft can accomplish this for you, if necessary. Presumably, you're on the shorter side so getting your saddle position more over the BB should help with power transmission (getting your Knee Over the Pedal Spindle) - that's the theory anyway as to why smaller sized bikes have steeper seat tube angles than the larger sizes. Shorter people + shorter femurs = steeper seat angles to get to KOPS.

As far as comfort goes, the long chainstays, relatively fat and comfy tires, and the longish rake of the fork will make this bike ride, and turn (very sluggish handling), like a 70s Cadillac compared to any dedicated "road" bike...my $0.02CAN worth - and today it's free of charge:D...
 
Ignoring time-trial or triathlon bikes, which have steeper seat tube angles, seat tube angles don't necessarily correlate to the level of "raciness" of a bike, in the same way that head tube angles do.

Many race-oriented geometries have relatively slack (low) seat tube angles, even while having fairly steep head tube angles.
 
rschleicher said:
Ignoring time-trial or triathlon bikes, which have steeper seat tube angles, seat tube angles don't necessarily correlate to the level of "raciness" of a bike, in the same way that head tube angles do.

Right-o. On a road bike, seat tube angle has more to do with the rider getting balanced between the saddle, pedals and handlebar. Manufacturers steepen the angle on smaller frames to get a shorter seat tube that will fit between two 700c wheels on a fairly short wheelbase, and reduce or eliminate toe overlap with the front wheel.

The net effect on shorter riders is that most of them are sitting too far forward, causing them to raise handlebars and buy all manner of gel-padded gloves, handlebar preparations, and physical therapy to accommodate strain on their hands, wrists, forearms, and shoulders.

In short, if you can't set the saddle back enough to maintain your center of gravity over your feet without pushing on the handlebar, you'll be using your arms to support your upper body.

REI has a full-load touring bike with more moderate seat tube angles, here--http://www.rei.com/product/776887#