Review: The Digit Datum & Its Integrated 'Analog' Suspension

The design came to life for a few reasons: for one thing, Tim likes simplicity. Fewer suspension components means less weight and fewer bearings, bushings, and pivots than the Datum's more traditional counterparts. Tim says that also makes the bike stiffer because there are fewer places for the system to flex. To make this thing happen, Tim ran a successful Kickstarter campaign, raising $89,386 to bring the bike to production. I'm clearly not the only one who was intrigued.

While the shock looks miniature at first glance, there's actually much more to it than meets the eye. It extends about halfway up inside the top tube, with the air valve, compression switch, and rebound adjuster poking out of the middle of the top tube.

At the moment, the Datum is available only as a frameset for $3,500 USD or in custom anodized colors for $3,700. There's a good chance that Digit will offer complete builds in the future, but supply chain issues at the moment mean that complete bikes would have very long lead times. My build came with a SRAM GX AXS drivetrain, Spinergy MXX 30 wheels, and a Manitou Mezzer fork, putting the complete build weight at 28.6 lb / 13.0 kg.

The Datum is available now for order online, and Tim is just beginning to send out the first production models.

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Frame Details

I've been riding a pre-production frame from Digit's pilot run, so my comments may not be fully applicable to the production run. Still, the frame I received has space and bosses for two water bottle cages (extra space in the front triangle being one of the biggest advantages of this design) inside the front triangle plus one below, rubber frame protection on the chainstay, and rubber internal routing ports.

The 12"-long strut provides not only suspension but also structural support. It extends up into the frame and has large oil and air volumes in order to provide consistent damping throughout the full travel range.


The bike has an emphasis on longevity and serviceability, with a suspension design that can be fully maintained by a competent home mechanic, requiring no special tools. Digit will also offer mail-in services, and each frame will come with a voucher for its first mail-in shock service.

Other details include a SRAM universal derailleur hanger and a Cane Creek press-fit bottom bracket, which comes with the frame.

In terms of sustainability, Digit points out that the most environmentally friendly parts are the ones not manufactured, purchased, and used, so the minimalist design has some roots in sustainability, too. For those parts that do come into existence, Digit uses aluminum and build its frames in California, where a significant portion of the state's electricity comes from renewable sources.

Geometry & Sizing


The Digit Datum is available in sizes S, M, L, and XL. The L frame I tested has a 1239 mm wheelbase, 480 mm reach, and 649 mm top tube. The head tube angle is 65° on the M, L, and XL sizes and 64.5° on the S, and all the sizes share a 75° seat tube angle and 435 mm chainstays.

Note that the relatively slack seat tube angle creates more space at the front of the bike than an average 480 mm reach bike these days - the top tube length of 649 mm is approaching lengths found typically on XL frames.

Digit recommends the M frame for riders 5'5" to 5'9" and the L frame for riders 5'9" to 6'1". At my 5'10" height, I fit neatly into the size chart for the L frame, but after spending some time on it, I recommend that anyone in doubt size down. Update: Digit has revised their sizing recommendations - the current suggested sizes can be viewed here.

I felt right on the cusp of what felt comfortable for me. The reach is right in my ideal ballpark for modern bikes, but the 75° seat tube angle sat me back far enough that the front end of the bike felt too far away from me, making me hyperaware that the seat tube angle was slacker than what I prefer. That feeling of being stretched out toward the front of the bike was exacerbated by a low 623 mm stack and 110 mm head tube.

I asked Tim about the seat tube angle and he explained that the seat tube angle isn't steeper because to steepen it he'd either have to reposition the upper pivot, which would change the linkage behavior, or give up the uninterrupted seat tube, which is nice because it accepts long dropper posts.

All of that said, most of the geometry is spot-on, especially for rolling terrain rather than the ride-up-to-ride-down style that we tend to have in more gravity-oriented zones.

Suspension Design

The obvious talking point about this bike is the suspension design. Tim created the Analog suspension design - named because the strut is an analog of the rocker link typically found at the top of a standard four-bar design.

Essentially, the idea behind the design is that compared to a more conventional dual-link, four-bar design, the upper link assembly is replaced by a strut that's housed in the top tube, and the lower link is placed right behind the bottom bracket. The rear triangle is a single piece, and unlike in many traditional designs that see the upper shock link moving in an arc, the strut is designed so that the rear triangle moves in a straight line relative to the front triangle - a slider, rather than a pivot.

The idea is to keep the instant center from wandering too much, keeping the suspension feeling consistent throughout its travel.

The leverage ratio averages a low 2:1 - the shock moves a full 70 mm as the bike moves through its 140 mm of travel. Both anti-squat and anti-rise are moderate and seem aimed at doing just enough but not too much to quiet the bike down.

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I spent time riding the bike first in Whistler, then in Bellingham, and most recently in Utah.

Climbing


As mentioned above, it took me a bit of tinkering to set up the Datum the way I wanted it, but once I moved the seat forward and sped up the rebound, the bike climbed nicely. Its behavior was very quiet while seated, and there was just a bit of bobbing when mashing on the pedals. On loose, even grades and on choppier trails, the bike held traction nicely, feeling sensitive without giving up too much efficiency.

I didn't love the slack seat tube angle, mainly because it moved my pedaling position far enough back (even with the saddle slammed forward) that the front of the bike felt a bit stretched out. At times, I struggled to feel like I had enough authority over both the front and back ends of the bike at once. I also ended up perched at the nose of the saddle quite a bit, which isn't my preferred position, and required me to be much more dynamic moving forward and backward over the bike than I would be on a bike with a more compact feel.

That said, despite the long top tube, the wheelbase isn't actually any longer than average for a size L bike with mixed wheel sizes, and the bike itself felt fine when maneuvering through twisty sections of trail and up stair steps - as long as I made sure I was in a position to put down power.

On more moderate terrain, especially once I moved down to the Utah desert for a few weeks, the stretched-out position was less noticeable than on some of my climb-steep-to-descend-steep rides in the Northwest. When in flatter, rolling terrain, which required dynamic movement over the bike all the time anyway, the pedaling position felt reasonable. I still found myself perched at the front of the saddle when climbing, but was out of the saddle enough that the forward and backward movement that I felt the bike required felt very natural. And, the slightly slacker seat tube angle meant that flat sections of trail didn't roll too much of my weight forward, which can sometimes contribute to arm, wrist, and hand discomfort on bikes with very steep seat tube angles.

Descending

My experience descending on the Datum was pretty similar to my experience climbing: the suspension performance is quite good, and the geometry is more niche, working well for me in some places and less well in others. When pointed downhill, the Analog suspension does its job precisely, soaking up both small and large hits in a variety of terrain, staying extremely predictable and holding traction nicely.

When the trails got steep, I wished for a higher front end, as the stack is on the short side. That meant that despite the respectable 65-degree head tube angle, I still felt pulled forward over the front wheel in a way that made me feel slightly uneasy. That feeling disappeared, however, once I left the Northwest, and I loved the sporty feel of the bike and the descending position once I was hopping around on choppy, rocky desert trails. It shines on technical cross-country trails that require a very dynamic riding style, and it provided plenty of forgiveness on awkward drops to flat, natural rock doubles, and ledgy stair-steps, both up and down.

While the bike is, in many ways, a generalist - its 140 mm of rear travel, 160 mm fork, and light weight make it a reasonable choice for a variety of terrain, and it'll certainly work on steep all-mountain trails and flatter trail systems alike - I felt happiest on trails with more meandering ups and downs than on the "get up to get down" rides.

I need to mention the sizing caveat again, since I think the size L frame that I rode will feel most natural for riders with long torsos or those taller than me. Being at what I consider the bottom of the proper sizing for that frame (according to me, not the size chart, which puts me in the middle), I was more bothered by the extra space between the slack seat tube and the low front end than taller riders likely would be. For my part, I'd happily take the Datum down any trail bike trail, but I'd be inclined to install some higher rise bars, and possibly an even shorter stem to improve the fit. I have no doubt that those changes would give this bike a chargier feel when pointed downhill.

How Does It Compare?

The most similar bike to the Datum I've ridden recently is the new Santa Cruz 5010, which sports 130 mm of rear travel paired with a 140 mm fork on mullet wheels - so 10 mm smaller than the Datum in terms of rear travel, but with a similar ride feel. However, the Datum has a slightly longer reach and a significantly lower stack, making the riding position feel more strung out than the 5010's - which is compounded by the Datum's seat tube angle being slacker than that of the 5010. Suspension performance is similar on the two bikes, with the Datum giving a bit more sensitivity and the 5010 falling on the more efficient, firmer side of the spectrum. Ounces to ounces, the Datum beats the 5010's weight by 2.4 lbs (1.1 kg).

Compared to my current favorite 140 mm bike, the Propain Hugene, the Datum is a tad more maneuverable, feels slightly more sensitive in its travel, and positions the rider a bit lower over the bike. The Hugene rolls on dual 29" wheels and has a steeper seat tube angle, more stack height, and a marginally steeper head tube angle than the Datum, positioning the rider over rather than in the bike but keep the riding position centered in a way that makes both the front and back of the Hugene very easy to manage and creates a very composed feel. The Datum has a pretty similar riding position, but while the Hugene feels as if it skips in straight lines over the terrain, the Datum wants to be pumped through compressions and maneuvered through all the twists and turns on the trail, giving it a more engaging, rather than quiet feel. The 31.2 lb / 14.2 kg Hugene build that we tested weighs 2.6 lbs (1.2 kg) more than the Datum.

Technical Report

The Digit Datum will initially be sold as a frameset only, so these comments aren't necessarily relevant to buyers' decisions and discussion of parts-for-money value, but, like on any bike, the parts did influence my experience of the ride, so I'll still mention the highlights.

OneUp cockpit: I've been wanting to try the OneUp cockpit for quite a while, so I'm glad I had the opportunity to try the bar and stem on the Datum. The bar and stem combo are quite light, which of course help contribute to the bike's overall low weight, and they feel very comfortable to ride. While there are so many variables at the front of a bike and it's tough to exactly determine how a particular cockpit setup contributes to the overall feel of the ride, I have absolutely no complaints about how the carbon bar felt, and since the ride felt appropriately dampened and precise, I can only assume that the system did its job flawlessly.

SQlab 611 saddle: The SQlab saddle is one that I'm always excited to see on a bike, since it's my all-time favorite. Tim warned us when he sent the bike over that the shape may be polarizing, but maybe I was lucky in that it suits me. SQlab places heavy emphasis on designing products that are "physiologically correct" and work with, not against, the body's natural movement to support longevity on the bike, plus help prevent saddle contact zone and back pain. While I'm not a physiologist or someone who can really evaluate what SQlab claims to do, I can say for sure that SQlab products tend to be tried-and-true winners for me.

Integer strut: And then, of course, there's that strut. It took me a while to make up my mind about the Analog suspension design, mainly because it's up against some serious competition. Mountain bike shocks are so, so good today. What can a simpler, more eccentric newcomer do? The strut did its job, maintaining traction and cushioning the ride on par with some of the other light trail shocks out there. In terms of feel, there's a smaller range of adjustment than most high-end shocks out there, but Tim is open to custom-tuning for his customers. As is, there's quite a bit of compression making the shock feel a bit less plush than most of the competition, and I had to run the rebound quite fast to make it feel composed and responsive. There's a compression adjustment switch that is extremely subtle, but again, that's custom-tunable. In short, the strut with its base tune should work well for most riders who run average, middle-road settings, and the custom-tuning option is great to have, but the design doesn't offer quite the same range of adjustments we're used to seeing.

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Pinkbike's Take

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Reviews and Tech Reviews Trail Bikes Digit Digit Datum