prb info for dummies by dummies

PRB (Prolonged Rocket Boost) is a quirk of the MKDS's engine that allows players who MT (mini turbo) fast enough to go through offroad without losing speed after "gaining" it either from a perfect boost start or from zippers/boost pads. PRB is lost when the player drops loses their boost for any reason (PRB will be lost after a shroom runs out). It is not something I would immediately go for starting out, due to the MT consistency that it requires.
Because some people can't, won't, and/or don't like doing PRB, there's a separate Non-PRB chart which disallows PRB racing for the most part, but it is allowed at the beginning of certain tracks "if the best 'natural' racing line requires the player to perform miniturbos quickly enough that it will cause PRB". These Non-PRB charts also disallow the use of shortcuts, which consists of any respawn abuse jumping over barriers, or otherwise "cutting a big part of the track in an unintended way".
All times submitted to the Non-PRB charts must be marked as so, in order to avoid guesswork in determining which times are and aren't using PRB in an advantageous way. If you didn't know what PRB was before you read this, your times are probably Non-PRB. But in any case...please just let the updaters know.

Let me be clear by saying that this is just an interpretation of the Non-PRB chart rules, which are old and unclear. This is NOT official in any way. If there are any discrepancies between this pastebin and the official site rules, assume the site rules are correct unless told otherwise by a site admin (Etch).
Let me know on Discord (Mr. Kickstart#2907) for any confusion in the list.

F8C: PRB can be used to cut through the grass up to and including the third MT of the race. If PRB is active after, you can't cut through the grass.
YF: PRB does not meaningfully impact this track.
CCB: PRB cannot be used to cut through the water.
LM: PRB can be used to clip the grass before the mansion. If PRB is kept after, you can't cut through the grass.

DH: PRB can be used to cut through the sand before the ridge (just after the third turn). You cannot go to the right of the trees or the left of the pyramid. If PRB is kept after, you can't cut through the sand.
DS: PRB can only be used to cut through the grass after the bridge.
WP: PRB does not meaningfully impact this track.
SR: PRB cannot be used to cut through the grass.

DKP: PRB cannot be used to cut through the snow.
TTC: PRB does not meaningfully impact this track. Do not abuse any respawn shortcuts.
MC: PRB can be used to cut through the sand/grass up to the curve with the piranhas before the tunnel. You must go to the left of the goomba after the first turn. If PRB is active after, you cannot release an MT offroad until PRB has worn off. Do not use the wallhop.
AF: PRB does not meaningfully impact this track.

WS: PRB cannot be used to cut through the mud. Do not use any respawn shortcuts.
PG: PRB cannot be used to cut through the flowers/grass.
BC: PRB does not meaningfully impact this track.
RR: PRB does not meaningfully impact this track. Do not use any shortcuts, respawn-oriented or otherwise. The corner cut is allowed.

rMC1: PRB can be used to cut through the sand up to but not including the second turn. Do not cut inside the pipes. If PRB is active after, you can't cut through the sand.
rMMF: PRB does not meaningfully impact this track.
rPC: PRB can be used to cut through the first turn. If PRB is active after, you can't cut through the grass.
rLC1: PRB cannot be used to cut through the grass/sand.

rDP1: PRB can be used to cut through the first turn before the bridge. If PRB is active after, you cannot release an MT in the grass until PRB has worn off.
rFS: PRB can be used to cut through the snow up to and including the big jump over the snow (the third turn, which is the sharp left one at the top of the minimap). If PRB is active after, you can't cut through the snow.
rBC2: PRB does not meaningfully impact this track.
rBP: PRB does not meaningfully impact this track.

rKB2: PRB can only be used to cut through the grass on the first turn before the giant water area.
rCM: PRB does not meaningfully impact this track.
rLC2: PRB can be used to cut through the grass up to and including the first 180 degree right turn. If PRB is active after, you can't cut through the grass.
rMB: PRB cannot be used to cut through the sand.

rCI2: PRB can be used to cut through the gap in the wall directly ahead of the starting line. If PRB is active after, you cannot release an MT offroad until PRB has worn off.
rBB: PRB does not meaningfully impact this track.
rSG: PRB can be used to cut through the clouds up to and including the first rainbow bumper and the clouds directly next to it. If PRB is active after, you cannot release an MT in the clouds until PRB has worn off. Do not use any respawn shortcuts.
rYC: PRB can be used to cut through the grass up to and including the cut over the water (where Yoshi's hands are). If PRB is active after, you can't cut through the grass.


The leniency of keeping PRB depends per kart.
Perfect boost start: 3-4 frame window at the start of every race, then you have 100 frames to perform an MT.
Zipper boost: 100 frames to perform an MT after you leave the zipper.
A perfect MT takes 46 frames (16 frames for the hop, then 30 for the actual MT).
Below is the length of the MT for every kart that can theoretically perform PRB, from easiest to hardest. All of these karts have more than 46 frames of boost, so there is some leniency. Leniency is the difference between a perfectly executed MT and the MT length of any kart, assuming the latter is at least 46 frames. MKDS runs (for all intents and purposes) at 60 frames per second, so to get the leniency in seconds, divide the leniency frames by 60. Do the math yourself, it's not that hard.

Dry Bomber: 73 frame MT.
Egg 1: 68 frame MT.
Standard DB: 65 frame MT.
Poltergust 4000: 62 frame MT.

Any kart below this line cannot perform "double hop PRB", essentially PRB with a hop between the drifts.

Standard YS: 60 frame MT.
Mushmellow: 56 frame MT.
ROB-BLS: 56 frame MT.
Standard LG: 55 frame MT.
Shooting Star: 51 frame MT.
Standard TD: 50 frame MT.
Banisher: 50 frame MT.
Standard RB: 50 frame MT.
Cucumber: 47 frame MT.

Any kart not listed here cannot keep PRB, as they have an MT length of at most 46 frames. It's not like the karts not listed are particularly useful but it is still something to note.