I'm commuting four miles wth a few slight hills here and there and am really enjoying it, but my lower back gets a little sore.

It could be from carrying a backpack, but I'm not sure. I'm also about twenty pounds overweight, so that probably has a lot to do with it.

It's a very slight herniated disc thing, I'm fairly sure, and it's only a slight nag in my lower right back (actually the top of my butt).

Anyway, how high should my seat be? The bike is sized correctly (LBS), and it's new. So is there a way for me to know the right level to adjust it?

Thanks

What I've always been told is that a good way to tell is by standing your bike straight up (no kickstand) and make your saddle level with your waist.

Sheldon knows all. Basically keep raising the saddle until it's too high.

Sheldon does know all. You should check this out too: https://sheldonbrown.com/pain.html#back

Your feet shouldnt be able to touch the ground.

Slightly disagree. Your feet should just barely be able to touch the ground on anything other than a BMX/cruiser.

the way we set people up at the shop is when your pedaling you want to have between a 20-25 deg bend in your knee at the bottom of the pedal stroke and we've never had problems sizing people that way.

on your back pain thing, ive got the same problem with a herniated disc and backpacks any bigger than a camel bak really bother me. Id check into getting a rack/panier set up and if you still have issues a shorter or higher rise stem couldnt hurt either

Regarding previous posts, much depends on the bottom bracket height.

If it's relatively high, your feet shouldn't touch the ground. If it's low, they may.

Likewise for having the saddle at waist height. A proper fit may or may not be at waist height depending on how high the bottom bracket is.

Try this link-
https://bikenhike.com/page.cfm?pageid=23&FAQid=25

I basically get up some speed and put my heels on the pedals. You should be able to fully extend your legs, without rocking your hips. Since you ride on the balls of your feet, that puts the right amount of bend in your knees.

if your on the saddle, and you can touch your toes to the ground, would the saddle be a tad to low?

depends, but probably that's just about right. i have to rock the bike over a bit to touch the ground while sitting on the saddle, but i'm told mine is too high. i went w/ sheldon brown's tips, and just kept raising it little by little until it was a little before i had to rock my hips to pedal. works for me.

Toe action sounds about right.

This is a common formula and works well for me. Measure your pubic bone height without shoes. You can do this with a narrow spined book pressed up tight into your inseam. Multiply by 0.883, and make this the distance from the center of the bottom bracket to the seat surface along the angle of the seatpost. For me with a 32 inch PBH, this gives 28.25 inches seat height.

When I had my seat too low, the front of my knees would hurt after long rides. If you get your seat too high, the back of your knees may hurt.

If the saddle is set at waist height for me on my current bike, it's too high. And if I can't touch the ground, it's too high. I've got a low bottom bracket (26cm above the ground) and quite short legs (29" inseam). The fit is fairly similar to a 70s style "racing" bike. Raleigh 3 speeds have a similar fit also. Stuff like an Electra Townie that claims to be "flat foot technology" or crank forward well... I still can just touch a toe.

On my old mountain bike, the saddle was around waist height, and I couldn't touch the ground reliably. That bike had a 30cm bottom bracket... and the fit led to more than one fall. It was easy to end up with a 3-4" drop between my toe and the ground, which can be a leetle problematic if you stop frequently. For someone my size, this makes the bike too big, but for larger people, it's often just fine.

Anywhere in that range is "normal" for a modern bike (some *very* large bikes may have an even higher BB, but I'm too small to try 'em ). On every bike I've ever ridden, there's a certain sort of muscle soreness I get around my knees if the seat is too low.

There's a good discussion on seat positioning on this Thread

"Waist height" isn't very accurate. For me, I can tell within a few millimeters whether the seat is too high or too low - and I can't tell where my waist starts within that limit.

You can use formulas, and that might get close, but really the only way to really tell is ride the bike. Keep increasing it about 2mm at a time until your hips start rocking or you start "tippytoeing" on the pedals, and drop it back to the last spot. Use a Sharpie on the seatpost if you need to.

Another good method I've read is to have someone hold the seat (or otherwise brace the bike) and pedal backwards with your heels on the pedals. When you get full extension with your legs pretty much locked and your heels on the pedals, it will give just enough knee flex at the bottom of the stroke when you're riding normally.

I will say this - beginners almost always have the seat way too low.

https://www.bikeforums.net/recreational-family/449648-little-help-seat-position.html

Have the cranks parallel to the seat tube. On the one that is lower, your heel should be able to barely touch it with your leg fully extended. You could probably lower it a cm or two from that depending on how far your ride and how often you have to stop.

Knees just slightly bent at the base of the pedal stroke. If you are locking out your knee the seat is too high.
Typically you should be able to put a foot down and be on your tip toes, butt on the seat and the other foot on the pedal. But usually you are supposed to come off the bike and straddle the top tube when you stop.

I just thought I'd throw in a word of caution with the "ride and raise until some factor" knowledge. It makes sense, trust me, it worked pretty well on my old road bike, but I foolishly disregarded (truthfully, I didn't know such a measurement existed at the time) the "minimum insertion" point on the seat post and well... lets just say the seat post wound up pretty bent, and the tube that it goes into is going to need some work to make it functional for any other seat post. Yes, n00b mistake, but its one I made after reading the same article and advice here so its worth mentioning.

+1, or at least it worked for me.

+1

This is the old "Fit Kit" formula which then became known as the Greg Lemond formula. Anyway, It's a good starting point. I personally have found that I prefer my saddle a little higher than this, but what the heck, it got Greg Lemond three Tour de France victories!

This is a good link to entire bike fitting...

https://www.cyclemetrics.com/Pages/Do...t_formulas.htm