Speed follows what viewers spend. By default every gift has a speed limit set by its price, so a pile of cheap gifts or taps can't beat someone who sent a big gift.

These are only the defaults — every limit below is yours to change. Raise the cheaper gifts' or the hearts' limits if you want small gifts and taps to be able to catch up with (or beat) the big spenders, or lower the top speed for a calmer race.

1. Power-ups (the gifts below) each have a top speed, shown as "Speed it reaches". Every gift of the same power-up climbs a fifth of the way there and adds its time: 1 gift = 20% for its time, 2 gifts = 40% for twice as long … 5 gifts = full speed. After 5 it stays at full speed and each gift just adds more time.
2. Other gifts add a little speed each — more for pricier gifts — and build up. How far they can go is set by everything that viewer has sent together.
3. Hearts on their own top out at a third of your top speed. Send a gift and its higher limit takes over: taps then carry the horse all the way up to that gift's limit, never past it.
4. Every gift lasts its time. When it runs out, its limit goes with it and the horse slows back down — keep the gifts coming to stay fast.

Example with the default 525 top speed (a normal gallop is 75): 1 Corgi (Super Saiyan) runs at ~140 · tap hearts on top and it climbs to its ~404 limit · 5 Corgis reach ~404 straight away · 99 Roses stop at ~273 · hearts alone stop at ~173.