reliable 45mph rim/tire setup?

Details are unclear to me, among those being what might be 'normal' !

a MTB tire is just not normal for pavement use, though it may be common.

lol people who do it are just wrong! lol

They make fine road tires, metro commuter tires, and city slick tires that should be quite stable at the speeds you describe.

My salvaged 'city slick' type tires worked quite well for me, though I never did reach 30mph!

Perhaps you frame geometry is not quite suitable for stability? and designed more for agility and low speed maneuverability???

Rake, trail, frame length, weight distribution, handlebars, and rider stance are all important contributing factors to stability at some chosen speed.

Oops! I forgot tire pressure.
Low pressure tires are probably not the best for our application, when we get to the higher speeds.

Glad you're having fun with motorized bicycle design!
It's a valuable undertaking, and rewarding.

Best
rc

Could be one, the other, or both.
True the rim.
Then static balance using a bit of electronics solder wrapped around spoke.
Then mount up tire. Run to assure it is seated properly.
Mount back on the truing stand and check for tire runout.
If un-acceptable, break down and re-mount, or replace tire.
Re-balance after runout check.
Somewhere in this mess you must assure bearings are in good order and properly tightened.
headset bearings and adjustment will be a factor, too.

And Pat's Sportsman Flyer is a racer. Probably is a tad skittish and designed that way for racing!

Good luck to you.
rc

For those kinds of speeds I prefer my set-up consisting of Atomlab "Pimplite" rims with Maxxis 2.5" Hookworm tires and a HD motorcycle type innertube and at least 12g. spokes.

I had my bike up to 64.3mph the other day and they were just fine with those speeds. You don't want to risk it with cheap wheel builds at those speeds.....that's just asking to get hurt.

I use whatever rim came with the bike, but I balance them very carefully. I use solder and wrap it around the spoke(s). You can also use stick-on golf club weights.

tires can be out-of-round, too. most of them are, actually, especially cheaper ones.

they're not designed for constant speeds over 10mph, so the manufacturers don't have the same standards as cars and motorcycles.

spin the tire (off the ground) and hold a crayon or chalk near the tread to see if there's a high spot.

three things can cause that.

one, is your innertubes. if you've got a fat tire and a skinny tube (like a 2.5" tire and a 2.125 tube) there'll usually be a low spot at the valve stem, because that's where the most rubber is on the tube, and it doesn't fully expand inside the tire.

(note: if you tell your local bike store that you need a fatter tube and explain why, they'll look at you like you're a total moron and probably tell you that's bs. most bike stores i've tried have been like that. just ask if they have wider tubes, and when they say "no, but..." just walk away.)

the second cause could be an out-of-round tire. buy better ones.

you might also have a "hop" in your rim. it's slightly egg-shaped and bouncing down the road. you need to true it, or find someone who can.

i build all my own wheels, and after trueing them, i mount the tires, ride them for a day or so, then re-true the wheels with the tires still on.

balancing? personally, i don't think it matters. i've been on this controversy before. harmonic vibrations in all vehicles are felt at certain frequencies, almost always most acute at 33mph. then again at 66. that's the speeds you'll notice your car's steering wheel shimmying at. accelerate, and it goes away.

same with bikes. at 33-35, my copper gas tank makes this weird humming sound, until i speed up or slow down.

but if wrapping solder around your spokes, fishing sinkers, or titanium valve caps make you feel better, knock yourself out...

Hi... You are takeing your life for granted over 35MPH..on bicycle rims and tires....need to use lite motorcycle hub -spokes-rim and tire for safety over 35MPH....