A straight that has been ridden hard stops being a straight. Braking bumps appear where riders slow down, acceleration bumps appear where they get back on the throttle, and a section that started life smooth ends up carrying a regular line of ridges that nobody built. Riders treat these as obstacles to be survived. It is more useful to treat them as a frequency, because that is what the suspension experiences, and a frequency has two numbers in it that you can actually go and look at.
Where do the ridges come from?
Nobody digs whoops on a practice track. They are made by repetition. A rear wheel under power lifts material and throws it backward, a front wheel under braking pushes material forward into a small ridge, and both processes are repeated at almost the same place by almost every rider on the property because everybody is braking and accelerating at roughly the same points.
Once a first ridge exists it enforces the ones after it, because a bike leaving a ridge lands at a distance set by its speed and its suspension, and it lands hard enough to start the next one. That is why the ridges arrive evenly spaced rather than scattered: the spacing is not chosen, it is the print left by the bikes that made it.
Spacing plus speed equals frequency
If the crests are a certain distance apart and you are travelling at a certain speed, the number of crests you meet each second is simply the speed divided by the spacing. That number, and not the height of the ridges, is what determines whether a suspension can keep up. The table below is that division, with speeds converted at 1.4667 feet per second to the mile per hour.
| Crest spacing | At 20 mph | At 30 mph | At 40 mph |
|---|---|---|---|
| 6 ft | 4.9 per second | 7.3 per second | 9.8 per second |
| 8 ft | 3.7 per second | 5.5 per second | 7.3 per second |
| 10 ft | 2.9 per second | 4.4 per second | 5.9 per second |
Read across a row and the reason speed helps becomes clear. Read down a column and the reason a short section is worse than a long one becomes clear too: taking two feet out of the spacing at 30 miles per hour moves the demand from 4.4 to 5.5 crests per second, a change of a quarter, without a single ridge getting any taller.
The two ways through
There are exactly two, and mixing them is what goes wrong.
The first is to skim, meaning to carry enough speed and enough weight to the rear that the front wheel touches only the tops of the crests while the rear drives across them. Skimming depends entirely on arriving with enough speed, because the whole method rests on the bike not having time to fall into the troughs. Backing off halfway through a skim is the classic way to put a front wheel into the face of the next crest.
The second is to work through, meaning to accept the frequency and use the suspension deliberately, often jumping in and out in pairs so that the bike crosses two crests per cycle instead of one. Working through halves the effective frequency at the cost of a much larger movement each time, which is why it needs a section long enough and even enough to establish a rhythm.
Choosing before the run
The choice between them is made on the ground before the run, not on the approach. It depends on the spacing, on whether the crests are even, and on whether the exit of the section leaves room to recover, which is the same reasoning applied to a corner in rut corners, picking a line and holding it.
The one thing to take away
Whoops are not fought with height, they are fought with spacing, and spacing is something you can go and pace out on foot.
Why does the spacing drift?
A whoops section never keeps the spacing it started with, and the drift has a direction. At the braking end, riders brake progressively earlier as the surface deteriorates, so new ridges appear upstream of the old ones and the section grows backward into what used to be clean straight. At the driving end, the ridges spread as riders carry more speed and land further along.
The result is a section that is tighter at one end than the other, which is precisely the thing that breaks a rhythm halfway through. That uneven end is worth identifying on foot, because it is where a rider who committed to skimming discovers the crests have moved closer together than the ones they set the speed on.
The maintenance answer is not to shave the tops off. Cutting the crests alone leaves the troughs and the section re prints itself within an hour. The material has to be moved back into the hollows and the whole surface reworked, which is a different operation with a different tool, described in grooming a track. Where the whole line matters more than the section, the reasoning is in riding lines, where the clock is actually won.
Sources checked for this note
The crests per second figures are a division performed by this desk, converting miles per hour at 1.4667 feet per second and rounding to one decimal. They describe the rate at which crests arrive and nothing else: they are not a suspension specification, they take no account of ridge height, tire deflection or the bike leaving the ground between crests, and no whoops section anywhere was measured to produce them. The description of how the ridges form and drift is this desk's own account of a mechanism, offered as a way of looking rather than as a finding.