Metrics To Understand And Reach Your Goals



At Datum, we get you clear cut metrics to describe bikes performance by combining high precision reverse-engineered data and simulation models of the whole bike/rider system.
No approximations, No room for interpretation.

Whatever change you make to your bike, it will impact geometry, suspension or both. With Datum's dashboard it's now possible to asses and control these. Using Datum's dashboard, each change of component or setting triggers a simulation in which your bike geometry, kinematics and suspension forces are recalculated. A virtual rider (you) is then put on the bike and the whole system is simulated at sag.
What you get is a geometry and suspension report that makes no compromise on accuracy.

The Dashboard's Anatomy

The following sections explain Datum's dashboard user controls and the output that's generated

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The 3 main sections of the dashboard.

Setup Panels: The inputs


The setup panels are where you can build bikes and make change to them before getting results in the other panels.

User interface options

At the top of each setup panel, the following options are available to help in your analysis and manage setups.

  •   Add setup: Open Setup 2's panel to build a second bike
  •   Close setup: Close Setup 2
  •   Duplicate setup: Copy this setup into the other setup panel
  •   Load setup: Load a previously saved setup
  •   Save setup: Save current setup (uses setup name input as file name)
  •   Clear setup: Clear all components from this setup

Components

Components are changed on bikes to alter their behavior all the time. However, riders have no reliable method to asses the resultant changes. Now you can easily change shock dimension or model, install an angle headset or build yourself a mullet and then track the effect on suspension and geometry.

The following components can be changed in the setup panels of the dashboard:

  • Frame (including frame modes and flip chips when applicable)
  • Shock (including offset bushings)
  • Fork
  • Handlebar
  • Stem
  • Wheel Sizes
  • Special headsets (angle, offset)

Settings

Changing bike's settings can alter it's behavior significantly. Whether it is by running more sag, raising your handlebar or saddle, these changes can blur the line between bikes.

The following settings can be changed in the setup panels of the dashboard:

  • Suspension: pressures, volume spacers, coils, preload, double crown fork height
  • Cockpit: bar width and rotation, headset stack, stem spacers
  • Saddle: seatpost extension and offset, saddle thickness and fore-aft position on rails

Going all out: A disclaimer

Note that even thought Datum let's you explore an infinite number of possibilities, we don't necessarily endorse all of them and you are responsible for the analysis and modification of your bike. Please check components compatibility with respective manufacturers before installing them on your bicycle. In regards to settings, please follow manufacturers' instructions and do not set your components in a way that would not be endorsed by them.

You wouldn't ride an incomplete bike?

We can't generate a bike's geometry if it doesn't have a fork, please make sure all of the opened setups have all their components and settings completed in order for the results to show.

Geometry Panel: Data that evolves with your setup


Even though Datum's bike geometry may look similar to a conventional geo chart, it's not. Conventional charts are static frame geometry, that made sense back when they were printed in catalogs, but it's 2020 now. See below how conventional frame geometry differ from Datum's bike geometry.

Conventional Frame Geometry
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  • Suspensions are topped out
  • Freezed, setup changes not reflected
  • STA and Top tube are not standardized across the industry
  • Reach-stack at HT opening, hands position is highly variable
Datum's Bike Geometry
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  • Geometry at Sag
  • Setup changes are reflected in geo chart
  • Actual saddle and bar tips position is used to calculate metrics

Suspension Panel: Quantifying suspension feel


The primary data you see in the suspension panel is the Directional Normalized Wheel Rate in relation to vertical wheel travel for both front and rear suspensions. You may ask yourself what does that mean? let's find out.

Wheel rate is a measure of the spring rate or compliance seen by your wheels. A bigger number means your suspension is going to feel firmer and a smaller number means it's going to feel softer or more compliant. Simple as that.


Directional Normalized Wheel Rate is a combination of leverage ratio, axle path, the direction of impact, weight bias, shock and fork construction and settings.
Considering all of these variables as a system let us derive precise, comparable and actionable metrics, an impossible feat if one would look at them individually.

    Here's some key features of our suspension graphs:

  • Normalized
  • We normalize wheel force, rate and energy. That means the numbers are relative to the weight on each contact patch of your bike. These numbers are comparable between riders despite different rider weight.

  • Front and rear data aligned at sag
  • Your suspension travel consists of it's negative part and positive part, we label it that way. By doing so, you can easily compare front/rear suspensions as well as different bikes with Sag as a reference, not top out.

  • g-force markers
  • To be fair, wheel rate doesn't give you all the information. The g-force markers are there to give valuable information on force vs travel usage. The first marker is your suspension preload or the amount of g-force needed to initiate travel. Until that force is reached, Rate is essentially infinite (very firm), needless to say preload is a negative trait most of the time unless it's kept minimal. g-force markers also give you an idea of the balance of the bike ie: for a 3 g event, if the front end uses more travel than the rear, you are guaranteed to experience forward pitch, no good!

  • Directional: pumping vs square edge hit
  • Your suspensions don't feel the same whether you're pumping terrain or hitting a square edge hit. Depending on the direction of input, it will be more or less compliant, the wheel path being the cause. By default, wheel rate is given vertically describing suspension compliance under vertical input (pumping, g-out). Rearward wheel rate (defaulted for a 50mm high square edge hit) let's you see how input direction affect compliance for a given bike/setup.

How it is calculated

Wheel Rate = (Suspension Rate)/(Leverage Ratio)²

First, fork and shock forces are modeled based on their specific construction parameters and the settings you run. You will see many approximation for these around the web, this is not one of them.


Example of a total spring forces, in all graphs, you can probe data, zoom on sections and change lines visibility.

Once suspension forces are known, vertical and rearward leverage ratios are calculated. Keep in mind that even telescopic forks have leverage ratios that depends mostly on head angle and input direction. Leverage ratio is actually just the mechanical advantage or lever an input at your wheel's contact patch has over the shock or fork at any position in the suspension stroke. This is the most studied suspension metric for bike's suspension , however, shock rates have generally a greater impact on suspension feel.


Vertical and rearward leverage ratio.

Finally, combining supension forces and leverage ratio and normalizing them reveal your suspension characteristics for your exact setup that you can tune and compare.


Normalized final suspension metrics.

You can't match our sag numbers?

sag is a very hard metric to measure repeatedly because of variations in body position, friction and measuring errors. We still wanted to give it to users as it's still used a lot, however, datum's dashboard can ensure precision and repeatability with the rider always standing in a relaxed position. Here's a few key points if you still want to match sag values: Use a digital pump, analog pumps can be vey off, especially in low pressure systems. Make sure pressure is totally equalized between chambers, cycle around transfer port until pressure stays constant at top out, you can leave pump attached for this. Make sure you have the correct amount of tokens and lubrication fluid volumes.

What about damping?

The suspension metrics we model for your bike consider all the spring force contributors in your suspension systems. Coil springs, air springs, auxiliary springs, ifp force, fork lower legs forces, bottom out bumpers forces etc. Altought most agree the spring part of suspension systems are the biggest factor in suspension feel and performance, damping is also important and can't be ignored. We are already seeking ways to provide information on how damping affect your suspension feel, in the mean time we still offer you the most accurate suspension and geometry data available.

Any more questions? Contact Us

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