I just noticed the sticker on my bike says the front tire should be 30 PSI, but the tire itself says max psi 40. It's the original tire. It's the 21" incher with the thin white wall.

What psi should I be using for maximum performance?

 

As it says, 40 psi is the max you should be putting in. I use 30-32 psi in front and 36 psi in rear (pretty much all the time solo riding).

 

The max pressure isn't for maximum performance, it's for maximum weight. Harley manuals assume 180 pounds of rider weight, I believe. So if you're about that, I'd run 30 psi. If you're heavier than that or you're carrying something, I'd run more. I wouldn't run less. And don't run over 40.

 

I would follow the tire. A tire dealer on here recommended pressure be kept on the higher side. Even the dealership said to use 38 front and back. I use 38-40 front and back, but my max is higher than yours and I have saddlebags with stuff in it.

 

Here we go again - this is a 'problem' across HDF! The words on the side of the tyre should be ignored as being misleading, unless you plan on riding your bike at its max permissible weight. Unfortunately tyre pressures and rider/passenger weight has been a weak point on Harleys in all the 40+ years that I've ridden them. The factory owners manual does a poor job in providing advice and guidelines. Fortunately those words on the sidewall are a US regulation only, which means that the rest of us can indeed forget them!

The weights in the manual should be considered a guide or starting point, that's all! Also, if changing tyre brand then ignore the manual, as well as the words on the tyre, and check that brand's website for recommended pressures, as not all brands are the same.

If you are of average weight, as mentioned by JustOneDean, then the owner's manual pressures should be reasonably close. There is no reason why you should not adjust them a little, for your personal preference. Personally I prefer mine slightly higher, which seems to give me better feel and tyre life. Especially if you are significantly heavier then increase pressures, by several psi if necessary - you be the judge!

 

My first bike was a V Star 650 and the sticker actually gave two different values for each tire based on how much weight was on the bike.

 

Round of applause for Yamaha! All the other brands of bikes I've owned over the last 40+ years also give guidelines for carrying extra loads, such as a passenger or luggage. The nature of the advice varies quite a bit, something we could do with an industry standard on. Harley's lack of advice is useless!

I prefer Avons on my Glide, which use higher pressures than stock tyres, so I use 38F/44R on MT tyres, up to 44F/50R, when we're 2-up and loaded for the grand tour. I have derived those numbers based on guidelines from other brands, plus the tyre makers, spiced up with a bit of experience.

 

You should always go off of what the sticker on the bike says not the tires

 

I run 30 psi front and 36 psi in the rear on my 883 sporty no passengers or baggage that's what the Haynes manual recommends

 

Don't worry about 40 max. You could go well over 40psi, and not risk a blowout. The problem is ride, performance, tread wear, etc...

Do what's comfortable for you without being squishy, or riding like it's got a steel wheel.

Personally I like mine with a bit more pressure so I can "feel" things. I run 38 up front, 36 or so in the back.