Mountain bike categories, by and large, tend to get messy. The lines between XC and trail, and trail and enduro bikes, are blurry at best, and continue to ebb and flow from season to season.
The line between hardtails and full suspension mountain bikes, by contrast, is as bright as red race course tape. This got me wondering: How does current hardtail geometry compare to full suspension geometry, and where do hardcore hardtails fit along the riding spectrum? It was time to run some numbers.
Hardtail suspension travel
With few exceptions, hardtails are no longer favored for mountain bike racing outside of the cross-country discipline. For that reason, it makes sense to split hardtails into two major categories: XC (race) and hardcore. The hardcore label became popular several years ago as a catch-all for bikes that are technically capable and are designed for fun, all-conditions riding rather than pure efficiency. If this sounds like the definition of a trail bike and trail riding in general — essentially the only mountain bike discipline that doesn’t involve racing — you’re not far off.
Back in 2016 Singletracks published a list our favorite hardcore hardtails, and we set a hard cutoff at 120mm of front suspension travel, and up. At the time, XC bikes were generally running ±100mm of front suspension travel, though times have certainly changed. Today it’s not unusual to see XC race bikes with 120mm of suspension up front, and it seems 140mm is now the more popular spec for aggressive, trail-oriented hardtails. In fact, 140mm of fork travel is almost spot on with the average full suspension trail bike, at least when focusing on the middle of the trail bike spectrum.
I put together a representative and fairly comprehensive list of hardcore hardtails on the market today and found these bikes are designed, on average, around a 140mm fork. There are certainly outliers on the list; the Chromag Rootdown and Nordest Bardino are both capable of running up to 170mm of travel; the standard Kona Honzo, one of the bikes that has defined the hardcore hardtail category over the years, comes with a 120mm fork. Not only is the average (mean) around 140mm of suspension travel, it also seems to be the most common (mode) among the bikes selected.
|BRAND||MODEL||YEAR||WHEEL SIZE||TRAVEL||HTA||STA||REACH||ETT||CHAINSTAY||BB HEIGHT||WHEELBASE||STACK||BB DROP|
|Commencal||Meta HT AM||2021||29||150||65||74||445||628||432||330||1205||639||40|
|On One||Big Dog||29||130||65||75||460||630||444||312||1223||628||58|
For me, geometry is where things get interesting. It turns out modern, full suspension trail bikes and hardcore hardtails are fairly similar along a number of dimensions including important ones like reach, chainstay length, and even seat tube angles. Again, there are outliers like the Marin El Roy with its 78° seat tube angle and 510mm reach at the upper end, and the Ragley Marley with its 73° seat tube angle and Commencal Meta HT AM with its 445mm reach at the other end.
For some of the other geo measurements, the gap between full suspension and hardtail trail bikes is a bit wider, as you can see in the table below.
|FS Trail Bike||66.0°||75.7°||469.6||627.8||436.7||337.9||1215.8||620.8|
Head tube angle (HTA)
In our test sample of FS bikes taken earlier this year, the average head tube angle was 66°; for hardtails, the average is more than a degree slacker at 64.9°. One explanation could be that sag affects FS and hardtail geo differently and that when both are weighted, their HTAs end up being pretty similar. More explicitly, a sagged (compressed) hardtail fork yields a steeper real world head tube angle, by nearly 1.5° for a typical hardtail running 25% sag, according to this geo calculator. On a full suspension bike, things are more complicated, but in general sag in the rear shifts both head and seat tube angles slacker, while fork sag makes both angles steeper, tempering the overall sag effect on geometry more so than on a hardtail. Note too that hardtail trail bike STAs are slacker by more than half a degree than FS bikes on average, but once sagged, they get 1.5° steeper which likely more than compensates for the difference.
Even among this crop of hardcore hardtails, there’s a wide range of HTAs, with the Thomson Hooch sporting the steepest at 66.5°, and the On One Dave laying back the slackest at a DH-worthy 62°. For hardcore hardtails, it seems a 65° head tube angle is middle of the road and is generally a safe bet.
Bottom bracket (BB) height
Bottom bracket height is an important part of the long, low, slack equation and at first glance, it might be surprising to see much lower BB heights on hardcore hardtails compared to full suspension bikes. If a bottom bracket height is too low, pedal strikes become an issue, but not to worry: Since hardtails BBs don’t sag down as much as their FS trail siblings, a lower height makes perfect sense. How much lower? On average, the hardtails I looked at had bottom brackets 26.1mm lower than FS trail bikes. That’s a lot!
Among those listed above, the 27.5-wheeled Orange Clockwork EVO has the lowest bottom bracket height at 296mm. The Norco Torrent, a 29er, has the highest bottom bracket at 333mm, which is still lower than the average (un-sagged) FS trail bike.
Effective top tube (ETT)
As far as cockpit fit measurements go, ETT is secondary to reach for many riders. Looking at hardcore hardtail vs. full suspension trail bike geo, the reaches are fairly similar (within 5mm) but the ETTs are not. On average trail hardtail ETTs are about 16mm longer than full suspension trail bikes. So given similar reaches, why are the ETT lengths so much longer on hardcore hardtails?
A partial explanation is that while the HTAs on hardcore hardtails are slacker, which effectively shortens the ETT, the slacker STA lengthens the ETT by a larger degree.
Diving deeper, keeping reach constant, a longer ETT also means that the horizontal position of the bottom bracket between the seat and head tube is shifted forward. This affects how weight is distributed between the front and rear wheels which plays into everything from traction to control. Here again, full suspension sag affects the position of the bottom bracket, which in turn affects how the bike is weighted. The simple answer is, a longer ETT on a hardtail can provide a similar ride feel and handling compared to a full suspension trail bike. Or, it could be the other way around, depending on how you look at it.
While researching this list of hardcore hardtails I was surprised to find some of the larger bike brands like Santa Cruz and Specialized don’t offer them. While the brands do offer XC-race and entry-level hardtails, they’re missing more capable (and reasonably priced) all-rounders.
Along many key dimensions, hardcore hardtails actually appear to be more hardcore and progressive than their FS counterparts. Looking closely, however, it’s clear modern trail hardtails and FS bikes are actually very similar, which makes it easy for riders to transition between the two. Both provide a fun, capable platform for tackling a wide variety of terrain, albeit at slightly different speeds — and price points.