Lower pressure tyres vs suspension seat post??

[Jose]

Hi All,

Which of the 2 will make me loss more performance, a tyre with lower
pressure, or a 1 pound heavy suspension seat post?

Of the non suspension seatposts, are they all equally "bad" at
absorbing shock and vibration?

Thanks,
Jose

 

[landotter]

On Jun 12, 8:06 am, [email protected] (Jose) wrote:
> Hi All,
>
> Which of the 2 will make me loss more performance, a tyre with lower
> pressure, or a 1 pound heavy suspension seat post?

Tires and suspension posts vary wildly in design, so one can't make a
blanket statement. For road riding, a 35mm+wide smooth tread tire with
a fine supple casing at 80psi (5 bar) or less is probably the least
fussy way to get a nice ride. Tires with rigid casings will be more
durable--but you'll feel a lot more road noise in your butt and hands--
road noise that even a suspension post won't be able to absorb.

As for performance--again, a supple casing'd tire will offer very
little performance loss--but a thick squidgy one at low pressure can
be downright nasty feeling.

Perhaps someone can chime in on suspension posts--but seems to me that
tires are enough suspension on the road. Suspension posts can add
another layer of complexity to your bike if that's something you find
compelling!

>
> Of the non suspension seatposts, are they all equally "bad" at
> absorbing shock and vibration?
>

Yes.

 

[Woland99]

On Jun 12, 9:05 am, landotter <[email protected]> wrote:
> > Of the non suspension seatposts, are they all equally "bad" at
> > absorbing shock and vibration?
>
> Yes.

I had REI bike with suspension post - looks good on paper but
unless you ride offroad all the time that thing is useless.
Good padded shorts and standing on pedals when going thru rough
surface is more effective. Seatpost on my bike eventually
developed torsional play so it was a really energy sink.

 

[[email protected]]

Jose who? wrote:

> Which of the 2 will make me loss more performance, a tyre with lower
> pressure, or a 1 pound heavy suspension seat post?

> Of the non suspension seatposts, are they all equally "bad" at
> absorbing shock and vibration?

Rolling drag of tires is caused by flexing of elastomers (rubber and
inter ply bonding) in the casing. If you want to get a feel for that,
look at the RR curves at:

http://www.sheldonbrown.com/brandt/rolling-resistance-tubular.html

These losses are not affected by road gradient, but only by speed.
That is, the faster the speed the greater the power required to
overcome RR. Meanwhile, extra weight on a bicycle has almost no
effect on flat terrain and requires a bit more power when climbing.

I don't think the two effects are trade-offs.

Jobst Brandt

 

[smokey]

Jose wrote:
> Hi All,
>
> Which of the 2 will make me loss more performance, a tyre with lower
> pressure, or a 1 pound heavy suspension seat post?
>
> Of the non suspension seatposts, are they all equally "bad" at
> absorbing shock and vibration?
>
> Thanks,
> Jose

I run 700X35 Avocet Cross Ks at 85 psi and find them to be more
effective at muting road vibrations than narrower tires at 100 psi. I
really feel this is a better way to go than a suspension post for road
riding. I do use a Thudbuster for off-roading on my mountain bike.

Smokey

 

[Jose]

On Thu, 12 Jun 2008 07:30:03 -0700 (PDT), Woland99
<[email protected]> wrote:

>Good padded shorts and standing on pedals when going thru rough

I'm not sure I can stand padded shorts - I tend to get numb :-(


>Seatpost on my bike eventually
>developed torsional play so it was a really energy sink.

You mean side play? How was that affecting your performance?

Thanks,
Jose

 

[Jose]

On Thu, 12 Jun 2008 11:47:50 -0700 (PDT), smokey
<[email protected]> wrote:

>I run 700X35 Avocet Cross Ks at 85 psi and find them to be more
>effective at muting road vibrations than narrower tires at 100 psi.

Well, if/when I decrease my tyres' pressure to 70 psi, I find them
confortable too. If you pumped your 700x35 tyres up to 100 psi, would
you still find them better than a 700x28 equally at 100 psi??


> I
>really feel this is a better way to go than a suspension post for road
>riding.

Why?

Thanks,
Jose

 

[Tom Kunich]

"Jose" <[email protected]> wrote in message
news:[email protected]...
> On Thu, 12 Jun 2008 07:30:03 -0700 (PDT), Woland99
> <[email protected]> wrote:
>
>>Good padded shorts and standing on pedals when going thru rough
>
> I'm not sure I can stand padded shorts - I tend to get numb :-(

Then you need a wider saddle or set up your bike so that you sit further
back on the wide part of the saddle. Numbness is not normal and that's the
first thing you need to work on. It took me 3 years to find a saddle that
worked good for me though most people seem to have fewer problems finding a
good fit.

The saddle I use is a San Marco Regal. Remember that regardless of what you
THINK, harder is usually better.

By the way - plastic saddles always hold their shape though if they have a
lot of padding it can squash down and change the dynamics of the saddle fit.
About the best you can usually get from plastic saddles is a fit that is
acceptable.

But leather saddles can stretch and shape themselves to your posterior and
can actually get comfortable. That's why you see some people who have spent
a small fortune on carbon fiber bikes mounting a 3 lb leather saddle to it.

 

[Pat]

>
>>Good padded shorts and standing on pedals when going thru rough
>
> I'm not sure I can stand padded shorts - I tend to get numb :-(
?
>
> Thanks,
> Jose

It's not the padded shorts that are causing your numbness....look elsewhere.

Pat in TX

 

[[email protected]]

On Fri, 13 Jun 2008 22:40:58 -0400, clare at snyder dot ontario dot
canada wrote:

>On Fri, 13 Jun 2008 22:35:37 GMT, [email protected] (Jose) wrote:
>
>>On 12 Jun 2008 17:02:14 GMT, [email protected] wrote:
>>
>>>These losses are not affected by road gradient, but only by speed.
>>>That is, the faster the speed the greater the power required to
>>>overcome RR.
>>
>>Seems logical - after reading your explanation.
>>
>>
>>> Meanwhile, extra weight on a bicycle has almost no
>>>effect on flat terrain and requires a bit more power when climbing.
>>
>>I'm sure I'm follwing you... I've always that a heavier object would
>>take more energy/efford to be kept going. Such as in heavier vs
>>lighter cars...
>>
>>
>>>I don't think the two effects are trade-offs.
>>
>>I'll agree, if I can understand how the heavier object doesn't require
>>more power to be kept going.
>>
>>Thanks,
>>Jose
> The heavier object only requires more power to keep going because it
>causes more flexing in the tires and suspension. Increase the tire
>pressures to compensate for the extra load and the rolling resistance
>does not increase (up to a limit) Smooth roads do not affext the
>suspension losses - which CAN be corrected for to some extent by
>tuning the suspension.
>** Posted from http://www.teranews.com **

Dear Jose & Clare,

For a typical bicycle on level ground, adding a kilogram results in
such a tiny increase in rolling resistance (the tires flex a hair or
two more) that only a theoretical calculator can see the difference.

Here's a side-by-side calculator:
http://bikecalculator.com/veloMetricNum.html

If you raise the bike weight from 9 to 10 kg, the increased rolling
resistance lowers the speed from 24.75 km/h to 24.71 km/h, a rather
theoretical 0.04 km/h drop, about 0.16%

Here's another calculator, with fewer digits:
http://www.kreuzotter.de/english/espeed.htm

Choose on-the-drops, and the result is 19.4 mph for the defaults with
a 20.9 pound bicycle. The predicted cruising speed won't drop to 19.3
mph until your raise the bike weight to 26.7 pounds, adding 5.8
pounds.

Even hauling such extra weight uphill doesn't make that much
difference. Go back to this comparison calculator:

http://bikecalculator.com/veloMetricNum.html

Here are the predicted km/h speeds up a 6% grade for several power
levels:

bike watts watts watts
weight 100 200 300
9 kg 6.70 12.90 18.38 (0.08 to 0.17 km/h faster)
10 kg 6.62 12.76 18.21

And some of that difference is offset by the slightly greater speed of
the slightly heavier bike back down the 6% grade:

bike watts
weight 0
9 kg 51.20
10 kg 51.52 (0.32 km/h faster)

Such tiny speed differences from weight are rarely as important as
wind drag and rider comfort, but weight is much easier to measure and
boast about.

Cheers,

Carl Fogel

 

[Andre Jute]

On Jun 12, 3:30 pm, Woland99 <[email protected]> wrote:
> On Jun 12, 9:05 am, landotter <[email protected]> wrote:
>
> > > Of the non suspension seatposts, are they all equally "bad" at
> > > absorbing shock and vibration?
>
> > Yes.
>
> I had REI bike with suspension post - looks good on paper but
> unless you ride offroad all the time that thing is useless.
> Good padded shorts and standing on pedals when going thru rough
> surface is more effective. Seatpost on my bike eventually
> developed torsional play so it was a really energy sink.

The cheaper suspended seatposts, with only one control for vertical
stiffness and horizontal rotational control, suffer torsional play. I
like the Post Moderne Glide and the cheap Kalloy well enough for
comfort biking, but the amound of torsional play would probably
disconcert a roadie. That said, the much more expensive Post Moderne
Cushy is torsionally stiffer only because it is stiff and obstructive
in all directions, adding zero to either objective or subjective
security of comfort and control.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

 

[Jose]

On Fri, 13 Jun 2008 16:07:31 -0700, "Tom Kunich" <cyclintom@yahoo.
com> wrote:

Hi Tom,

>Then you need a wider saddle or set up your bike so that you sit further
>back on the wide part of the saddle. Numbness is not normal and that's the
>first thing you need to work on. It took me 3 years to find a saddle that
>worked good for me though most people seem to have fewer problems finding a
>good fit.

I haven't tried paded shorts with my present sadle - some Selle
Italia, very similar to models SLC/SLK, with no padding at all. I've
never felt so "free" on a sadlle before; I still need to get my
posterior used to long rides on it, though - last time I did, I think
I ended up with blisters...

Still on the mater of paded shorts, I admit I have some troublke
understanding how such a thin layer of foam can make a significant
diference. Worse than that, what the point of getting a non-paded
sadle, and then wearing paded shorts??

>But leather saddles can stretch and shape themselves to your posterior and
>can actually get comfortable. That's why you see some people who have spent
>a small fortune on carbon fiber bikes mounting a 3 lb leather saddle to it.

Good point! I can imagine that after a while a leather sadle would
accomadate my seat bones quite well. However, I imagine that would
make me "sink" in the sadle and get numb you know where ;-P

Thanks,
Jose

 

[Jose]

On Fri, 13 Jun 2008 20:27:56 -0700 (PDT), Andre Jute
<[email protected]> wrote:

Hi Andre,

>The cheaper suspended seatposts, with only one control for vertical
>stiffness and horizontal rotational control, suffer torsional play. I
>like the Post Moderne Glide and the cheap Kalloy well enough for
>comfort biking, but the amound of torsional play would probably
>disconcert a roadie.

I use a cheap Kalloy. It does have side play; that doesn't bother me.
I was much more disconcerted when I last rode a front suspension MTB
bike from a friend of mine - I felt I couldn't tell which way the bike
was going :-(

Thanks,
Jose

 

[Jose]

On Fri, 13 Jun 2008 21:13:19 -0600, [email protected] wrote:

Hi Carl,

>For a typical bicycle on level ground, adding a kilogram results in
>such a tiny increase in rolling resistance (the tires flex a hair or
>two more) that only a theoretical calculator can see the difference.

OK, that makes feel less guilty about using a suspension seat post ;-)


>Choose on-the-drops, and the result is 19.4 mph for the defaults with
>a 20.9 pound bicycle. The predicted cruising speed won't drop to 19.3
>mph until your raise the bike weight to 26.7 pounds, adding 5.8
>pounds.

So, basically you're saying that aerodynamic drag would play a bigger
role in performance that an increase/decrease of 1 or 2 pounds...

>Such tiny speed differences from weight are rarely as important as
>wind drag and rider comfort, but weight is much easier to measure and
>boast about.

It's easier to sell a lighter bike, than a more aerodynamic position
;-)

I was amazed at the diference in more speed and less efford during a
recent longish ride, after removing the front mudgard. Next, I'll see
if I can lower the handlebar.


Thanks!
Jose

 

[Art Harris]

Jose wrote:
> >As for tire pressure, I would suggest going to a wider tire at lower
> >pressure if you want to minimize road shock. That would minimize
> >rolling resistance and avoid pinch flats.
>
> I'm presently using a 700x25, which I pump up to 90 psi on the road,
> 70 psi around town.  
>

That should be pretty comfortable, although I'd worry about getting
pinch flats at 70 psi on a 700x25.

> I can still fit a 700x28, but I'm not sure I can
> fit a tyre wider than  that.

> Would the wider tyre:
> 1) absorb shock equally well, if pumped at 100, and 80 psi,
> respectivelly?

A wider tire should get _less_ pressure. For example, a 700x28 at 70
psi would have less rolling resistance and less chance of pinch
flatting than a 700x25.

Optimum tire pressure depends on tire width, rider weight, and your
preference for either comfort or lowest rolling resistance. It's a
trade-off.

Note that some tires aren't really the width they're advertised as. A
tire marked 700x28 might actually measure 25 or 26mm on a rim.

In your case, I'd recommend a true 700x28 at about 85 psi rear and 80
psi front (assuming you're not a heavyweight). If comfort is your
primary goal, you might need a bike that takes 700x32 tires.


> 2) would it have a better performance at, say, 70 psi, due to less
> flexing/deformation than the 700x25?
>

Yes, a 700x28 would have better performance than a 700x25 at 70 psi.

Art Harris

 

[Michael Press]

In article <[email protected]>,
[email protected] (Jose) wrote:

> On Thu, 12 Jun 2008 07:05:41 -0700 (PDT), landotter
> <[email protected]> wrote:
>
> >Tires and suspension posts vary wildly in design, so one can't make a
> >blanket statement. For road riding, a 35mm+wide smooth tread tire with
> >a fine supple casing at 80psi (5 bar) or less is probably the least
> >fussy way to get a nice ride.
>
> I've been using Maxis Detonator 700x25. Around town, I need to drop
> the pressure to 70 psi. Away from town, I'm fairly confortable at 90
> psi (+ the suspension seat post I use).
>
>
>
> > Tires with rigid casings will be more
> >durable--but you'll feel a lot more road noise in your butt and hands--
> >road noise that even a suspension post won't be able to absorb.
>
> How do you know if a tyre is less rigid than another (before trying
> both)? Just by looking at the tpi count? I get the feeling that the
> lower tpi count tyres are smoother - could I be mistaken?

A true high thread per inch side wall is thinner than
lower tpi. Thinner side wall means less power dissipated
flexing the side walls.

Before you buy you handle the tire flex the sidewall with
your hands. Check the tread thickness. Flex the tread.

> >> Of the non suspension seatposts, are they all equally "bad" at
> >> absorbing shock and vibration?
>
> OK, so why are so many people enthusiated about carbon and titanium
> seat post? I understand that carbon can be made more flexible, but on
> such a short extension, I have doubts. Titanium - besides
> outrageously expensive - I had the idea was more rigid than
> aluminum...

--
Michael Press

 

[Tom Kunich]

"Jose" <[email protected]> wrote in message
news:[email protected]...
> On Fri, 13 Jun 2008 16:07:31 -0700, "Tom Kunich" <cyclintom@yahoo.
>
>>But leather saddles can stretch and shape themselves to your posterior and
>>can actually get comfortable. That's why you see some people who have
>>spent
>>a small fortune on carbon fiber bikes mounting a 3 lb leather saddle to
>>it.
>
> Good point! I can imagine that after a while a leather sadle would
> accomadate my seat bones quite well. However, I imagine that would
> make me "sink" in the sadle and get numb you know where ;-P

It is possible for a leather saddle to break-in badly and then not work
well. But most of them do not apply pressure to the wrong places. My Brooks
B-17 was fairly comfortable right from the start, but after 500 miles it was
sort of surprising to me that it actually felt good to sit on. I've never
known that sensation before. Of course I always used plastic saddles too.

 

[Jose]

On Sat, 14 Jun 2008 04:41:17 -0700 (PDT), Art Harris
<[email protected]> wrote:


Hi Art


>> Would the wider tyre:
>> 1) absorb shock equally well, if pumped at 100, and 80 psi,
>> respectivelly?
>
>A wider tire should get _less_ pressure. For example, a 700x28 at 70
>psi would have less rolling resistance and less chance of pinch
>flatting than a 700x25.

On a 15 mm wide rim, I doubt it would pinch flat. Anyway, 700x28
seems a better all round choice - it should have better performance at
70 psi around town, and still take 90 or 100 psi for real road use,
without bursting.


>Optimum tire pressure depends on tire width, rider weight, and your
>preference for either comfort or lowest rolling resistance. It's a
>trade-off.

Yes, I think I understand that - my present 700x25 Maxis Detonator, at
around 66 tpi, is significantly smoother than the 700x25 Continental
UltraGatorSkin I used before, at the same pressures


>Note that some tires aren't really the width they're advertised as. A
>tire marked 700x28 might actually measure 25 or 26mm on a rim.

That sucks! Anyway, since I can't find any 700x28 around here, I'll
have to order through Internet, and rely on thread counts, recommend
pressures, etc.


>In your case, I'd recommend a true 700x28 at about 85 psi rear and 80
>psi front (assuming you're not a heavyweight). If comfort is your
>primary goal, you might need a bike that takes 700x32 tires.

I'm not sure if my bike can take 700x32 tyres, but among the 700x28,
some are more confortable (albeit less performant) than others ;-)


Best,
Jose

 

[Jose]

On Sat, 14 Jun 2008 11:29:58 -0700, Michael Press <[email protected]>
wrote:

Hi Michael,

>A good 25 mm wide tire
>can be built with 127 thread per inch casing. A 28 mm wide
>is always built with 66 thread per inch casing.

Vittoria Rubino Pro and Pro Tech, 700x28, 120 tpi, 70-115 psi, 230-250
gr.

The ContinentalUltraGatorSkin 700x28, and Panaracer Pasela 700x28 also
come to mind. At the least the Continental has a hight thread count -
as always...


> This difference
>alone will negate the advantage in width of the 28 mm wide tire.

Not sure what you mean here. I've learned that lower tpi equals more
confort but less performance. Am I missing something?

Aramid vs steel bead: besides a slight weigh diference, what
perceivable diferences do they have?


>I find 25 mm wide tires to be comfortable.
>If you want wide tires for comfort, then you need a new frame.

No, I don't think I want a full suspension frame ;-)

Best,
Jose

 

[Art Harris]

Jose wrote:

> At the least the Continental has a hight thread count -
> as always...
>

Continental counts the threads in each ply. It's not a fair
comparison.


>
> I've learned that lower tpi equals more
> confort but less performance. Am I missing something?
>

A high tpi casing is more flexible and has lower rolling resistance.
If anything, it may be more comfortable.


>
> Aramid vs steel bead: besides a slight weigh diference, what
> perceivable diferences do they have?
>

None, except they're easier to fold and carry as a spare.

Art Harris