You put side bites in your 2+1 and the board went stiff. It tracked down the line like it was on rails and felt gutless off the bottom, so you pulled them out and decided side bites weren't for you.

The side bites were almost certainly fine. You left a full-size single fin in the center box and bolted two more onto the rails, and your board is now carrying more fin than it has ever had in its life.

The mistake wasn't the side bites. It was the fin you didn't change.

If you're still deciding whether to run side bites at all, that argument is over here. This one assumes you said yes.

What the side bites take over

A single fin does two jobs at once: it resists sideways slip when the board is on rail, and it gives the tail something to pivot around when you turn.

Put fins on the rails and the first job moves. On rail, the side bite on the engaged rail sits in cleaner water than anything near the stringer and is already angled into the flow by the boxes. It grabs. The center fin, meanwhile, is sitting along the axis of the turn doing far less than it was.

The second job stays. Through the flat, off the bottom, between rails, the side bites are barely loaded and the center fin is the only thing organising water at the tail. That is the part you cannot delete — and it is why a 2+1 with the center pulled is not a twin. The boxes are in the wrong place for one.

So the side bites take over hold-on-rail, and the center fin keeps drive-through-the-flat. But you just added area to do a job the center fin was already doing. Take none of it back out and you are running more total fin than the board was ever built for. It tracks. It doesn't turn. That is a fin-area problem wearing a side-bite costume.

The number you cannot work out, and the one you can

Every guide, ours included, says drop the center fin an inch or two. Now try to check it.

Side bites are sold with a published area. Center fins are sold with a depth and nothing else — of the 108 single fins on our own shelf, none publishes an area figure. So the trade you are being told to make is between a number you have and a number nobody prints. The arithmetic cannot be shown, by us or anyone.

What can be shown is where the manufacturer itself stops. True Ames' own 2+1 chart:

Board type Center fin Side bites
Shortboard 5.5" – 6.5" 2.6" – 3.7"
Mid length (egg shape) 6.5" – 8" 2.6" – 4"
Performance longboard 6.5" – 8" 3.25" – 4"

They footnote it honestly — "a few examples of standard 2+1 setups," not a rule — and they state the relationship it encodes: "as the size of your center fin increases, the size of your side bites can decrease, and vice versa."

The combo sets say the same thing a second way. Every center depth True Ames will sell you paired with sides falls between 6.0" and 8.0", against sides of 3.25" to 4.0".

So the working range tops out at 8". If you are running a 9" single and adding side bites without touching the center, you are an inch past the deepest center fin True Ames will put in a 2+1. On a 10" log, two. That is the whole diagnosis for most boards that have never felt right.

One thing to buy on, not depth: base. Depth is what fins are labelled with, but the base is what sits in the water when the board is flat and driving, which is the job you just gave the center fin exclusively. Two fins of the same depth with different bases are not the same fin.

Which one is yours

A mid-length you want more drive from. Wayne Rich Power Tilt at 6.5", $83.75, with Wayne Rich 3.4" side bites, $73.75 — $157.50 the pair. (The Futures set is the same price.)

The Power Tilt ladder stops at 7.5" and never had a 9", because it was never meant to work alone — True Ames calls it "our favorite 2+1 option in all conditions." If it feels loose after a few sessions, go to the 4.0" Wayne Rich rather than up in center fin. Add the area to the rails, where you wanted it.

A log with side-bite boxes you rarely use. California Classic at 7.0", $86.75, with the generic 3.25 side bites at $73.75 in either FCS or Futures — $160.50 the pair.

Then pull the sides on small clean days and put your usual big fin back in. This setup admits what it is: a log with an option. The Cutaway is the wrong fin here, because it frees up the tail and the tail is the thing you like about this board.

A 2+1 that has never felt right. Change one thing, and it isn't the side bites. Take the center down to 7.0" and leave everything else alone. If your board came with a 9" fin in it, that was the only variable outside the manufacturer's range to begin with. A Cutaway at 7.0", $86.75, does it and frees the tail at the same time — its cutout removes area from exactly the place that resists a fast direction change.

You keep sliding out, not tracking. Then you have the opposite problem, and the Cutaway is the wrong direction — you would be removing the thing that was holding you. Go up in side bite before you go up in center fin.

A bigger, heavier board in waves with push. Smith / Parrish Full Base at 7.0", $86.75 — extra rake and hook in the tip, narrower base, drawn for Hawaiian power. In small clean surf it is more fin than the wave is asking for.

One fin has to serve two boards. The Greenough 4-A ($84.00–110.00, from $69.00 in orange; also in Volan) or the California Classic ($80.75–107.50) — nine depths each, and usable as a 2+1 center only in the bottom third of the ladder. Neither is the sharpest 2+1 center here, because neither was drawn to be one. The Greenough family argument has its own post.

You want it decided. The Performer at 6.25" with 3.25 sides — $157.50 the pair. True Ames credits John Perry and Dave Lamberston with inventing the 2+1, which they called the "Threedom," and this is the template it was invented on. On Futures, take the Performer 2+1 combo at $133.50 instead — the same two fins for $24 less, the largest combo saving we list. Ride it a month before you change anything.

On a classic log the Performer is the wrong tool. It is drawn for competition longboarding, and in a board built to noseride it works against the outline. Take the California Classic at 7.0" and read the log branch above.

Two exceptions to the rule above

Lovelace Side Runners are the set you do not size down for, and Lovelace says so: "ride these with the same center fin you'd usually ride or a tad smaller — you don't need to step way down." A pair adds barely half what a pair of 3.7s does. The rule holds; the input changed.

A small fin behind a twin is a trailer, not a 2+1 center. A trailer is added to a board that never had a center fin, to buy back hold. A 2+1 center is reduced on a board that already had one. Opposite directions, opposite mistakes — and the trailer question has its own post.

If you take one number away: the manufacturer that makes almost every fin in this shop will not sell you a 2+1 with a center fin deeper than 8". Whatever is in your board right now, that is the ceiling.

Bring the board in and we'll measure what's in it.

Related reading

Sources

True Ames 2+1 sizing chart and product copy from https://www.trueames.com, retrieved 2 August 2026. Prices and stock from our own catalog, 2 August 2026. The 108-single-fin count and the combo-range working are on file.