One of the user comments left below the article was that hardtails would benefit from being compared at some level standardized sag percentage, which would better reflect the bike’s geometry with a rider on it. One brand taking this approach is Cotic, who currently presents the geometry of their bikes at 25% sag. However, the majority of brands only publish the static geometry chart.
I also subscribe to the philosophy of comparing hardtails against full suspension bikes with the hardtail geometry accounting for the front end sag, and it was my motivation when I developed the Sagged Hardtail Geometry Calculator. Accounting for the sag in a hardtail’s fork to correct the geometry chart provides a good comparison against the static geometry of full suspension bikes, where both ends of the bike sag roughly the same amount. This is generally an improved way of looking at hardtails whether you’re comparing frame geometry or bike fit between hardtails and full suspension bikes.
The steepening of angles is not at all unexpected and as always you would be wise to account for the steepening when looking at your desired head angle. That steepening of around 1.5 degrees might make the super slack hardtail seem more logical than it appears at first glance, or perhaps it would rule out the reasonable head angle once you’ve determined it seems too steep with your weight over it. The seat tube angle however, does seem to be a secondary concern for riders in their search for new bikes. The recent trend for very steep seat angles on hardtails should be looked at with a skeptical eye when you see the resultant angle of a sagged hardtail. If you select a hardtail with a seat tube angle of say, 78°, which seems to be a nice “on-trend” number for a capable trail or enduro bike, make sure to account for the additional increase you’ll get from the front end sagging. It would be a costly way of finding out that super steep seat angles don’t make a whole lot of sense on a hardtail after all.
1. Comparing a hardtail against a full-suspension bike? Use the Sagged Hardtail Calculator to change the static hardtail geometry to sagged and then plug the outputs of the sagged hardtail into the Bike Geometry Calculator to compare the two styles of bike more closely.