Bicycle Mechanics - can a suspension seat post make your wheels last longer?

I was debating this with a friend. He thinks it would not matter. I looked all over the net for answers. Any mechanical engineers out there?

My thought is that a body is unsprung weight. You go over a bump and without suspension, the wheel takes more sudden shock. With suspension, the force of the body on the wheels is dampened and the sudden loads are diminished. Think of a hammer with a big piece of thick rubber separating the head from the bulk of the hammer. It would seem to make the hammer less able to pound a nail and a reduced sudden load.

Any ideas?

If all your weight is on the saddle, not really. Getting your butt out of the saddle can help save rear wheels.

Any reasonably rideable post is not going to react fast enough to save your rear wheel from let's say a seated 15 mph curb impact.

First, the rider is not entirely unsprung. You gots the legs and the butt, saddle spings, frame compliance, and the tires.

Second, you have to establish that shock loads are a cause of wheel failure.

Best is to pay attention so you don't hit or run over stuff

Any reasonably rideable post is not going to react fast enough to save your rear wheel from let's say a seated 15 mph curb impact.

+1

A well built wheel will fail due to wear at the braking surface. If you're hitting stuff hard enough to damage rims, suspension post or not, you will damage them.

there's a reason we speak of riding a bike vs. driving it. You're not supposed to be dead weight on the saddle. When negotiating bumps you lift off the saddle, and your knees become suspension swing-arms, allowing the bike to lift over the bumps without having to lift your weight.

So, if you never leave the saddle, a suspension post would reduce stresses below, but since you don't ride that way it's moot point.

In theory you are correct, unspung weight is hard on wheels. This mainly affects cycle tourists who ride rough tracks and trails carrying heavy loads on the frame. Their solution is to use fatter tyres and more spokes.
Experienced riders can respond to big bumps more quickly than newbies so it depends on the rider.
Generally, responsive riders can use much lighter weight bikes and wheels.
Heavyweight riders who are starting out can be particularly harsh on the bike so suspension can be used to reduce mechanical stress.

In summary - yes, but.

The best approach is to spec and build wheels to withstand anticipated loads, ride properly, and don't bother with silly junk like suspension seatposts (they're a bad idea cause they rob power, add weight high up, and develop slop if they don't already have it from day one).

^^^ Sounds like you've never ridden a really good suspension seat post. I have Thudbuster ST. It does not rob power, I think it actually adds power to my bike (a crank forward bike) because it keeps me pedaling hard no matter if I'm riding over bumps or not. The weight is minimal, something like 400 grams; if you're going to be that picky about weight without entering the Tour de France............ And no, there's no slop, never has been; the only way I can see it getting sloppy is if it's set up for a lighter person than the rider or if the bushings are starting to wear (and replacing the bushings is a cheap and easy DIY fix). And bottom line, the ride is amazing, you really do feel it working, it actually feels like the seat is not moving but rather that the rear wheel is moving down/up over bumps which is what a true suspension system should do, and you rarely feel like you are bouncing or altering the distance between the seat and pedals (when crossing very heavily rutted streets, there is some bounce, but those streets are not fun to cross without it either). And no, I don't work for Cane Creek.

For the OP, I think it lessens impact to the rear wheel, which would theoretically keep it in better shape.

I've never felt my cheap-o suspension seatpost robbed me of power either. And while there is a small amount of slop (1/8" maybe) when I grab the saddle and wiggle it, I can't sense it at all when I'm on the bike.

The weight kills me every time I hammer out of the saddle or try to bunnyhop. Mainly due to the height of the weight like Kimmo says. When you're stomping on the pedals swinging your bike to and fro that extra weight up top is unpleasant.

there's a reason we speak of riding a bike vs. driving it. You're not supposed to be dead weight on the saddle. When negotiating bumps you lift off the saddle, and your knees become suspension swing-arms, allowing the bike to lift over the bumps without having to lift your weight.

So, if you never leave the saddle, a suspension post would reduce stresses below, but since you don't ride that way it's moot point.

+1 I'm always astounded by the number of people who don't know this. They sit in the saddle like a sack of potatoes and beat the crap out of their bike and themselves. Most of those kinds of riders are road bikers too. To misquote the Bard "Get thee to a mountain bike!". Fifteen minutes in a hard tail saddle riding like that will teach you more about how your legs and arms work than a life time of road cycling.

douglasseatle: Ride light in the saddle. Flex your arms and legs as you ride over bumps. Also look further down the road so that you can anticipate bumps and holes. You won't need a suspension seat post and your wheels will last longer.

It is astounding how many people missed the question, which is "can a suspension seat post make your wheels last longer?" It was not how can I make my wheels last longer or it was not to invite a response of comments similar to don't run into things. The fact is most of your weight should be on your seat unless you are standing on your pedals to reduce impact. Weight on the handlebars in seated riding should be very light.

I coached and raced for a dozen years as a cat 2. One of my coaches was John Howard. I know something and am not a clutz on my bike.

READ THE QUESTION, RESPOND TO THE QUESTION. Some of you were to the point of being insulting. Others got it (thanks)

It is astounding how many people missed the question, which is "can a suspension seat post make your wheels last longer?" It was not how can I make my wheels last longer or it was not to invite a response of comments similar to don't run into things. The fact is most of your weight should be on your seat unless you are standing on your pedals to reduce impact. Weight on the handlebars in seated riding should be very light.

I coached and raced for a dozen years as a cat 2. One of my coaches was John Howard. I know something and am not a clutz on my bike.

READ THE QUESTION, RESPOND TO THE QUESTION. Some of you were to the point of being insulting. Others got it (thanks)

My answer: Not enough to make a difference. In theory good, in practice poopy.

That was a little rude, also rather bold of you to call the comments of others "insulting". People post here to participate in discussions, even if they don't conform to the unwritten rules retrospectively imposed by a new member.

It is astounding how many people missed the question, which is "can a suspension seat post make your wheels last longer?" It was not how can I make my wheels last longer or it was not to invite a response of comments similar to don't run into things. The fact is most of your weight should be on your seat unless you are standing on your pedals to reduce impact. Weight on the handlebars in seated riding should be very light.

I coached and raced for a dozen years as a cat 2. One of my coaches was John Howard. I know something and am not a clutz on my bike.

READ THE QUESTION, RESPOND TO THE QUESTION. Some of you were to the point of being insulting. Others got it (thanks)

READ THE QUESTION. RESPONSE TO THE QUESTION: No...with the proviso that if you sit on the seat rather than ride on a saddle, slamming into things with your bike isn't going to protect the equipment no matter how much suspension you have.

But, since you aren't a klutz on a bike, you should know this.