Buying mods for speed secondaries, looking for some advice

I believe speed secondaries can go over 20.

If speed is the first secondary listed it is more likely to increase. Always look for purple or gold mods with speed secondaries as they may increase that speed secondary 3 or 4 times.

Good luck!

I've seen speed secondaries over 20

I think a speed secondary can get up to 26 or something if it starts off as a 5* yellow mod and upgrades speed each time (but this is absurdly rare). Typical speed secondaries will start off as 3-5 speed before you start upgrading them

Fairly certain that:
As a 5 dot mod speed secondaries start at 5 and can increase 4 times adding 5 each time.
4 dot, start at 4 increase 4
etc.

TL;DR - buying gold mods with speed as a secondary will give you the best chance of getting very high speed secondaries.

OK here goes. This is my understanding of how it works.

The maximum a speed secondary can start at is 5. The maximum it can be upgraded to is 25.

Upgrading of secondaries on mods works the same no matter what the secondary is. When you upgrade, at levels 3, 6, 9 and 12, you will either reveal a new secondary or upgrade a previously revealed secondary. You can only upgrade secondaries that you can see when the mod is level 1.

Gold mods are the best. All secondaries are already revealed. You will therefore randomly upgrade one of the four revealed secondaries at each upgrade/reveal level. This is the way you get a +25. Speed has to be one of the four listed and it has to be randomly chosen for upgrade at each opportunity. It's very rare.

Purple are next. Three secondaries are revealed. You will randomly upgrade one of the three revealed secondaries at level 3, 6 and 9. At level 12, you will reveal the last secondary.

Blue up next. Two secondaries are revealed. You will randomly upgrade one of the two revealed secondaries at level 3 and 6. At levels 9 and 12, you will reveal the last two secondaries.

Green. One secondary is revealed. You will be guaranteed to this secondary at level 3. At levels 6, 9 and 12, you will reveal the last three secondaries.

White. No secondaries are revealed. You will reveal a secondary at each of the 3, 6, 9 and 12 upgrade/reveal levels.

So to get high secondaries, you need them to be already revealed at level 1. The position of the secondary has no effect on whether it is upgraded or not (so 1st does not mean better). This might come from the fact that if you have a green mod with speed as the revealed secondary, it is guaranteed to be upgraded so you'll end up with something in the 8-10 range. But doesn't mean it's the best.

Hope that helps and make sense. If anyone thinks I've made a mistake somewhere, let me know.

My best speed secondary is +22. That was really lucky. That one had 2 adds of 6 and 1 of 5. I have never seen one start at 6, but rarely see them add +6. From that, I would estimate that 5 +6+6+6+6 for a total of 29 would be the best you could get.

Of course, the odds of getting that are much worse than winning the lottery. I feel like won the lottery with my +22, especially since it is on a speed set.

I have a couple 20's. Also I've seen a few reach +18 without being in the first slot as long as it's listed (i.e. Colored mods).

Ok great, lots of good advice, and it's nice to know just how wrong I was. @BingBang, very thorough explanation. I think the highest speed secondary I've seen is 19 (I have one at 18) and that's after I combed over all 50 toons in my arena top-10. Thanks again to everybody for your wisdom!