Shock Absorbers on Seat Posts

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Shock Absorbers on Seat Posts

Postby AndrewJames » Mon May 14, 2012 7:08 pm

Hi

This might seem silly. I realise shock absorbers on the front or rear forks of MTBs cause of loss of kinetic energy and therefore require more effort in riding a hard tail? on a stretch of road. But if the only shocky on the bike is the seat post, will there still be a significant or any real world energy loss?

Context - riding say 20kms to the CBD on smooth bike paths with little to no bumps.
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by BNA » Mon May 14, 2012 7:21 pm

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Re: Shock Absorbers on Seat Posts

Postby il padrone » Mon May 14, 2012 7:21 pm

They do tend to work to iron out some bumps. You could get similar effects with a bigger set of tyres at lower pressure. I don't know anything about loss of efficiency, but I believe the Thudbuster is the best one to use (not cheap).

The problems with these telescopic suspension posts comes when they have been used for some time. They wear and the seat mount becomes all wobbly - rotationally and up and down. Generally the only fix is to replace them.

Maybe save your pennies and buy a Brooks Flyer :idea:

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Re: Shock Absorbers on Seat Posts

Postby scirocco » Mon May 14, 2012 8:59 pm

AndrewJames wrote: But if the only shocky on the bike is the seat post, will there still be a significant or any real world energy loss?.


Probably less about wasting energy in the bike than about the loss of your own efficiency. Your pedal stroke gets sloppy if you are bouncing around or pedalling harder. But if you're commuting, why worry? Just do what's comfortable, if a regular saddle is not.
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Re: Shock Absorbers on Seat Posts

Postby R12RT » Tue May 15, 2012 6:22 am

My Giant CRX2 originally came with a suspension seat post.

After about 7500km I noticed it became a bit bouncy so I replaced it with an alloy post.

With the alloy post I didn't really noticed a lot of decrease in comfort. What did surprise me was how heavy the suspension seat post was.
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Re: Shock Absorbers on Seat Posts

Postby rustychisel » Tue May 15, 2012 10:36 am

R12RT wrote:My Giant CRX2 originally came with a suspension seat post.

After about 7500km I noticed it became a bit bouncy so I replaced it with an alloy post.

With the alloy post I didn't really noticed a lot of decrease in comfort. What did surprise me was how heavy the suspension seat post was.



this.

Suspension seatposts are largely speaking, a solution in search of the problem, and the problem is one of use. If your arse is welded to the saddle then you're not using the best shock absorbers you have, your legs. This is more common with upright positioned bikes but not entirely uncommon with road bikes and flatbars as well. Learn to lighten the load on your butt and use your legs to suspend, pivot and smooth out the bumps. Even the bumps you don't see can be tamed with moderately bent elbows and a soft grip (you feel the front wheel rise and move with it) and then use your legs to smooth out shocks to the spine and torso.
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Re: Shock Absorbers on Seat Posts

Postby Ozkaban » Tue May 15, 2012 11:15 am

I had a shock absorber seat post on my old trek hybrid. From what I could tell, it did nothing except add weight.

I could be seriously off on this, but it seems to me that most shocks transmitted to the seat are from the rear wheel. If this is true, then the angle of the seat post is completely wrong for a telescopic shock absorber to have much impact - if the shock travels up the seat stay then the shock is no where near the axis of the shock absorber, being the seat tube.

As I said, I have no idea if the above is remotely close to reality but it seems reasonable to me and in practice I found no difference with the seat post.

I agree with the above posts - use your legs or buy a sprung seat. Another alternative is to run fatter tyres at lower pressures - eg 32s will be much comfier than 23s.
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Re: Shock Absorbers on Seat Posts

Postby ekib » Tue May 15, 2012 1:24 pm

Andrew,

I agree with R12RT and Ozaban. I had a suspension seat post on an old Avanti hybrid. Firstly it tended to pogo a lot then after a while it welded itself in place. I finally swapped it for an alloy seat post. I found the same as R12RT that the suspension post added a lot of weight for no real gain.

I suspect the suspension seat post is mostly for the sale in the bike shop. You go and jump on the bike, take it for a spin around the car park and it feels nice and comfy. You then buy the bike.

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Re: Shock Absorbers on Seat Posts

Postby arand18 » Tue May 15, 2012 5:16 pm

A good to really good carbon fiber frame would work just as well as shock absorbers on the seat post, and even better carbon seat post, also shocks would add weight, not much but the more weight the harder
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Re: Shock Absorbers on Seat Posts

Postby Nobody » Tue May 15, 2012 7:51 pm

AndrewJames wrote:Hi But if the only shocky on the bike is the seat post, will there still be a significant or any real world energy loss?

Context - riding say 20kms to the CBD on smooth bike paths with little to no bumps.
Much good advice already.

Even if you start off with a better suspension seatpost like a Thudbuster or get a Brooks Flyer (as I did years ago) you may find in time you don't need them. These days I find the Brooks Flyer a bit too much for the road or bike paths. I used to use it off road for a while but don't even use it for that now, preferring a Brooks Imperial (no springs) off road. Relying more on the tyres.

The first thing you may want to look at is tyre pressure versus your (plus the bike's) weight on each wheel. You may find you can lower tyre pressure without losing much (if any) speed.
http://www.dorkypantsr.us/bike-tire-pre ... lator.html

As some have said, consider a seatpost with some flex. There are various ones made of carbon, Titanium or steel. Trek are now making frames to actively take advantage of seatpost flex by decoupling the seatpost and seat tube from the frame. Called IsoSpeed decoupler.
http://www.trekbikes.com/au/en/bikes/ro ... ature_tour

Another option is to get a non-sprung tensioned leather saddle like a Brooks which have a bit of give too. Some other saddles are also designed with some give without extra padding.

Image
My Brooks saddle with steel Nitto seapost. My tyres pressures are set near what the link says above. Combined with a steel frame and thick bar tape makes for a fairly comfortable ride on bike paths.
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Re: Shock Absorbers on Seat Posts

Postby trailgumby » Tue May 15, 2012 9:10 pm

+1 to the advice above.

My experience of telescopic seatposts is that grit gets in 'em and then they jam. If you MUST have a susser seatpost, Thudbuster is the go.

I've found a carbon seatpost does a lot to damp road buzz on alloy frames, even with 23c roadie slicks at 100psi.

Off road I tend to use 2"+ tyres at what most consider stupidly low pressures (mid to low 20s), and with 4" or more of suspension travel on at least one end.
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Re: Shock Absorbers on Seat Posts

Postby silentbutdeadly » Tue May 15, 2012 9:28 pm

I found a Post Moderne suspension seat post was more effective as a hammer than as a mechanism for holding up a bicycle seat...

In all seriousnessness...cheap suspension seat posts are an effective demonstration of tool before technique. Which is another way of saying...you're doing it wrong.
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Re: Shock Absorbers on Seat Posts

Postby avroncotton » Wed May 16, 2012 7:02 am

Nobody wrote:
AndrewJames wrote:Hi But if the only shocky on the bike is the seat post, will there still be a significant or any real world energy loss?

Context - riding say 20kms to the CBD on smooth bike paths with little to no bumps.
Much good advice already.

Even if you start off with a better suspension seatpost like a Thudbuster or get a Brooks Flyer (as I did years ago) you may find in time you don't need them. These days I find the Brooks Flyer a bit too much for the road or bike paths. I used to use it off road for a while but don't even use it for that now, preferring a Brooks Imperial (no springs) off road. Relying more on the tyres.

The first thing you may want to look at is tyre pressure versus your (plus the bike's) weight on each wheel. You may find you can lower tyre pressure without losing much (if any) speed.
http://www.dorkypantsr.us/bike-tire-pre ... lator.html

As some have said, consider a seatpost with some flex. There are various ones made of carbon, Titanium or steel. Trek are now making frames to actively take advantage of seatpost flex by decoupling the seatpost and seat tube from the frame. Called IsoSpeed decoupler.
http://www.trekbikes.com/au/en/bikes/ro ... ature_tour

Another option is to get a non-sprung tensioned leather saddle like a Brooks which have a bit of give too. Some other saddles are also designed with some give without extra padding.

Image
My Brooks saddle with steel Nitto seapost. My tyres pressures are set near what the link says above. Combined with a steel frame and thick bar tape makes for a fairly comfortable ride on bike paths.


Very nice seat post!
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Re: Shock Absorbers on Seat Posts

Postby Nobody » Wed May 16, 2012 9:40 am

avroncotton wrote:Very nice seat post!
Thanks. It's a Nitto S-84. Not cheap and not for weight weenies, but I noticed the improvement in comfort from my previous alloy post.
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Re: Shock Absorbers on Seat Posts

Postby DarrylH » Wed May 16, 2012 2:42 pm

Did anyone read the question?
The worst case of energy loss, ie pogoing, is when you are standing, so the seat-post should not have any effect. On cheap end bikes with poor suspension you can get some pogoing sitting down, but this is from putting a lot of force onto the pedals and should not happen with just a seat post.
For those against sprung seat/seatpost, even Brooks recommends a sprung seat if the seat is lower than the handlebars.
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Re: Shock Absorbers on Seat Posts

Postby Nobody » Wed May 16, 2012 8:09 pm

DarrylH wrote:Did anyone read the question?
Yes. I even quoted part of it above.

DarrylH wrote:The worst case of energy loss, ie pogoing, is when you are standing, so the seat-post should not have any effect. On cheap end bikes with poor suspension you can get some pogoing sitting down, but this is from putting a lot of force onto the pedals and should not happen with just a seat post.
Not everyone's experience is the same. Some are heavier, more powerful, or naturally use a lower cadence than others. Then there is differences in style and position etc.

DarrylH wrote:For those against sprung seat/seatpost, even Brooks recommends a sprung seat if the seat is lower than the handlebars.
True, but most enthusiast have their handlebars at or below saddle height. Also we tend to fine tune our bikes, learn to react to terrain better and generally harden up a bit over time. Although spring saddles and suspension seatposts like the Thudbuster may be a good choice initially, unless the conditions are particularly arduous and/or the cyclists rides upright, they end up becoming unnecessary in time for road/path.

Below is my MTB. If I (being middle aged) can ride this off road without issues, then most people in time can ride on bike paths and roads without suspension too.
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Shock Absorbers on Seat Posts

Postby toolonglegs » Wed May 16, 2012 9:40 pm

Interesting bit of design on specialize's new posts... http://www.cyclingnews.com/features/pho ... sl4/216730
Might take out a bit of road buzz... But I like my rigid alloy post... Might be a different story after a week in Belgium.
I know you love quoting that you ride a rigid Mtb no problems nobody but I expect that depends on how and where you ride off road...
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Re: Shock Absorbers on Seat Posts

Postby Nobody » Wed May 16, 2012 11:29 pm

toolonglegs wrote:Interesting bit of design on specialize's new posts... http://www.cyclingnews.com/features/pho ... sl4/216730
Might take out a bit of road buzz... But I like my rigid alloy post... Might be a different story after a week in Belgium.
Thanks. Interesting. The cobble gobbler. :lol:
Image

toolonglegs wrote:I know you love quoting that you ride a rigid Mtb no problems nobody...
Love is a strong word, but I'm comfortable with it. I know there would be people who will think I'm backward/stupid for doing it.

toolonglegs wrote:...but I expect that depends on how and where you ride off road...
How is casually these days. I used to ride a rigid in a MTB club for a couple of years from about 1990, so I don't really see the need to change to a DS for casual riding if I can manage without.

Where I'd rather stay as non-defined. But I've fractured my nose, rib(s), little finger in at least 2 places and put a tare between my fingers. Three separate events. Many other crashes. So I'd say it's a little bit more involved than your average bike path. I'm trying to take it easy these days (less injuries) so I'm not as hard-core as most. Maybe if I get a dropper post I might get more adventurous again.
Last edited by Nobody on Wed May 16, 2012 11:44 pm, edited 1 time in total.
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Re: Shock Absorbers on Seat Posts

Postby DavidS » Wed May 16, 2012 11:42 pm

R12RT wrote:My Giant CRX2 originally came with a suspension seat post.

After about 7500km I noticed it became a bit bouncy so I replaced it with an alloy post.

With the alloy post I didn't really noticed a lot of decrease in comfort. What did surprise me was how heavy the suspension seat post was.


I have a 2009 CRX3 and the seat post has just broken after 15,000KM. The break is effectively in the suspension so the post still holds the seat up.

I am looking at replacing the seat post but I've noticed that I'll need a post with some length as saddles seem to be a lot further from the cross bar than on old bikes. Do I need to worry about the length of the post? Are there particular brands/models I should look for or avoid? I am also looking at replacing the saddle with a Brooks B17 as the CRX saddle (which has been comfortable for me) is knackered so can I assume a Brooks saddle will fit a new alloy post?

As for suspension on the seat post, I really can't see the point.

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Re: Shock Absorbers on Seat Posts

Postby Nobody » Wed May 16, 2012 11:51 pm

DavidS wrote:Do I need to worry about the length of the post?
Yes. It's a good idea for it to be 10cm in the frame for durability of your post and frame.

DavidS wrote:I am also looking at replacing the saddle with a Brooks B17 as the CRX saddle (which has been comfortable for me) is knackered so can I assume a Brooks saddle will fit a new alloy post?
You can.
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Re: Shock Absorbers on Seat Posts

Postby toolonglegs » Thu May 17, 2012 12:09 am

Maybe if you had front forks you wouldn't hit the deck so much Nobody :lol: .
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Re: Shock Absorbers on Seat Posts

Postby mitzikatzi » Thu May 17, 2012 7:00 am

A rigid in action on a bike path :shock:

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more here not sure a suspension fork would make it any easier to ride.
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Re: Shock Absorbers on Seat Posts

Postby thejester » Thu May 17, 2012 9:06 am

I got rid of my suspension seat post and my bum thanked me.
All it seemed to do was increase the intensity of bumps.
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Re: Shock Absorbers on Seat Posts

Postby DavidS » Fri May 18, 2012 12:18 am

Nobody wrote:
DavidS wrote:Do I need to worry about the length of the post?
Yes. It's a good idea for it to be 10cm in the frame for durability of your post and frame.

DavidS wrote:I am also looking at replacing the saddle with a Brooks B17 as the CRX saddle (which has been comfortable for me) is knackered so can I assume a Brooks saddle will fit a new alloy post?
You can.



Thanks, I'll measure it up but looks like they are 40cm and i think my seat is about 25cm above the frame so looking good.

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