tire questions

If you keep getting flats?, mark the flat tube (& the wheel) when you take it off, so when you find the hole in the tube you can then check the exact same place on the wheel to see if there's anything thats puncturing the tube.

35 to 40 may be a little soft if you are a "heavier" person. I need to run tires at 50 - 65 to avoid rolling in corners.

Did you run your fingers all around inside the tire?
Sometimes a small staple or thorn is too small to see but you'll sure feel it with your finger.
Make sure you aren't pinching the tube by barely filling it after you remount it,squeeze the tire all the way around the wheel near the rim. Let the air out and fill it all the way .

Are you spokes tight? Pluck each one and listen . One really loose spoke will poke through your rim liners once you put weight on your bike.
All your spokes should have about the same pitch when you pluck them or tap with a screwdriver.

I put talcum powder or cornstarch on my tubes before I shove them into the tires to keep them from binding. Just like your " frank and beans " on a hot summer day.

I'm sure there is something simple you've overlooked.
I sure hope you find the little prick hiding in your tire.
Best of luck man,
TIM

why does my back wheel keep locking up on me

Welcome to the forum.
There are a lot of knowledgeable and creative minds here.
(excluding me)
You came to the right place for help, but provide us detailed information .
When does it lock up?
Are you on the brakes?
What kind of brakes do you have? Coaster, caliper,disc, V-brakes,cantilever,internal hub?

Many different kinds of brakes, each can have different problems.
Can you take some pictures if you aren't sure what you're dealing with so someone can help you ?

I have the same problem with now 4 tubes all new flat with holes on rim side but I have 2 of those straps to protect the tube. I just bought the last one 2 days ago and it got flat not even 24 hours later and this one was a Schwinn with slime. So I am planning to get those super thick tubes because I think the problem is that how the bike is built (Lowrider) all the weight is in the rear tire, bike and my body weight and the streets in PR are rather crappy. So yesterday when it broke down again I walked back to sears and left the bike on a gas station and got another but regular tube and when I got back to the gas station I empty the flat tube of the smile, used super glue to glue the old tube without air all around the rim and the strap on top of it (gonna post a pic of that below) and THEN the new tube/rim on top. I couldnt find any reason why the tube get pinched but if now it happens again, I really dont know what to do. I thought it would be an experiment worth to try.