Easton Part 3: EC70 ISA Seatpost
Easton manufactures three seatposts in the ISA range: the EA90 in aluminum, and the EC70 and EC90 in carbon. The EC70 range of products are Easton’s workhorse, rough-and-tumble components, while the EC90 range cuts weight to a minimum. These weight savings are achieved without any loss of strength and durability through very demanding manufacturing methods, which increases cost considerably. Each post is available in either 0 or 20mm offset - I went with 0 for a bias toward my road pedaling position - in 27.2mm diameter. The EC70 post was the logical pairing with my EC70 AX bars.
There’s not much to talk about when it comes to a seatpost shaft; it’s either round and true to size (mine is 27.2mm on the money), or not. It either holds up or not. That leaves stiffness, and this is relative, so hard to provide empirical feedback on, especially since the more post there is extending out of the frame, the more it’ll flex. The EC70 is stiffer than the Specialized CG-R suspension posts I’ve used for the last couple years, which is no surprise; they are designed to flex far more than any typical post. Having ridden the post on three bikes now - Brodie Romax carbon, Brodie Romax aluminum, T-Lab X3 - I would consider the post ‘neutral.’ It’s unremarkable under me. On my most comfortable bike, the T-Lab, the post is a better option than my CG-R, because the suspension of the latter is overkill on that frame. On my Brodie Romax in ‘road mode’ with 32mm Rene Herse tires (pink, below), the post is just flexible enough paired with a stiff Fizik Arione carbon rail and body saddle.
The stand-out aspect of the ISA post is the ISA part: Independent Saddle Adjustment. The post ships with fittings for round and ‘un-round’ carbon saddle rails. These clamps envelope the rails vertically, and easily create enough compressive force to prevent rail migration. This is not the case with many popular posts, let me tell you!
The ISA is accomplished by adjusting the two post’s long ‘grub screws,’ which are heat-treated steel, for strength and durability. The screws are antagonistic; thread one in, and the other must back off to allow the saddle to rotate up or down. The saddle affords infinite adjustment within its range. I ran the post on seat-tube angles right around 73 degrees, which is quite standard. The adjustment range will easily accommodate the steepest and slackest seat angles one might find on any drop-bar bike.
RESULTS and INSIGHTS
A good seatpost should be invisible under the rider once set up correctly. This was my experience with the ISA post once I’d adapted to the overall feeling of the new bike I first mounted it on, which was stiffer in the back end than the other bikes I’d been riding lately. I rode the ISA for thousands of kilometres without a hint of an issue. It wasn’t until I’d returned home from a month of riding and family vacation in Europe (100+ hours on the bike) that I experienced a surprising change: the saddle came loose during a criterium (yes, I racing on my gravel / adventure bike). It was distracting, and somewhat detrimental to performance, but not nearly as bad as it would have been had the saddle used a design that didn’t separate rotation and rail clamping. The crit course was rough, and I was eating my stem half the time, all over my saddle to get aero. The shocks to the front and back of my saddle worked the rotation adjustment bolts loose, which hadn’t been touched since initial set-up. The saddle was able to rotate up and down a few degrees, but unable to actually slide fore and aft, let alone fall off. Since I didn’t want to stop to tighten the post, I put up with it. I any other circumstances, a simple pause would have resolved the issue.
I was a bit surprised this happened in the first place, but soon realized this was simply an adjustment I’d need to adapt to by doing a bolt-check periodically. I normally wouldn’t have to do this with posts, but none of my other posts have anything like the ISA mechanism, which is better overall. I had the same loosening occur a couple months later in a cyclocross race, as I’d forgotten to check the post, and had only added a little Loc-Tite to the threads after the first occasion. So I added more, and thousands of kilometres later, haven’t had a recurrence.
All components have their idiosyncrasies. Many are invisible to an experienced mechanic, as so much wrenching becomes muscle memory. High end components tend to have the most fine-grained nuances and learning curves. As long as learning their ins and outs in the early days through shakedown rides doesn’t lead to part failure, this is no problem. Always bring your tools, and expect the unexpected!
BOTTOM LINE
I really like the EC70 ISA post. For the riding I’ve put on it (>4k kilometres), it’s been a good fit. One of the ISA’s advantages that might not be obvious is that it is close to ‘unbreakable’ under normal use. Its adjustment bolts are not load-bearing (under tension), but under compressive load. A two-bolt post, like a Thomson, is prone to snapped bolts in the event of saddle slamming, hardware fatigue, or both. The ISA’s design makes for one less thing that can fail on the bike while far afield.
The post’s rigidity is a non-issue for me in either direction. I.e., it’s not something I think about when I ride, There’s certainly value in running a really compliant post for a variety of use-cases, but I found no need or desire to grab for my CG-R posts to run on my carbon Brodie Romax or titanium T-Lab while either bike had the EC70 mounted. In a perfect world, I’d ride the ISA on each of my three drop-bar bikes I’m riding all summer, and reserve the CG-R for cyclocross in the fall on my aluminum CX bikes.
