175 mm vs 165 mm cranks for touring?

[justareader]

Is there a rule of thumb for crank length that takes into account the
type of riding you do?

Most mountain bikes have longer cranks since riders tend to do more
climbing than spinning.

My pants inseam is 30" and my knees have been doing fine for the last
30,000 miles with 170 mm cranks. Recently I have run across some
deals on crank/chainring combos with varying crank length.

Are my knees going to instantly explode if I try riding 175 mm cranks?

 

[Jim Smith]

justareader <[email protected]> writes:

> Are my knees going to instantly explode if I try riding 175 mm cranks?

Yes. Wear goggles.

Just kidding. Wear earplugs.

All BS aside, I can't tell the differance between 170mm and 175mm.
Just my 0.02

 

[Art Harris]

> My pants inseam is 30" and my knees have
> been doing fine for the last
> 30,000 miles with 170 mm cranks.

With a pants inseam of 30" I think 175s may be too long for you. Why
look for trouble just to get a "good deal."

Art "pants 34 inches, cranks 175mm" Harris

 

[Qui si parla Campagnolo]

Put three people in a room and ask about 'proper' crank length, get
four opinions. If 170s work for you, stay with 170s..
"if it ain't broke, yada, yada."

 

[Luke]

In article <[email protected]>, justareader
<[email protected]> wrote:

> Is there a rule of thumb for crank length that takes into account the
> type of riding you do?

The rule of thumb is to opt for the crank which is most comfortable.
This is not meant as a facetious reply. I've a 32 inch inseam and
consider 175mm arms too long; I'm most comfortable with 170mm cranks,
but others with identical inseams harbor different opinions.

>
> Most mountain bikes have longer cranks since riders tend to do more
> climbing than spinning.
>
> My pants inseam is 30" and my knees have been doing fine for the last
> 30,000 miles with 170 mm cranks. Recently I have run across some
> deals on crank/chainring combos with varying crank length.

Rule No. 1: Let necessity and suitability take precedence over price
when qualifying a good deal. This is a lesson borne of experience:
there's a box of ill-suited parts in my closet brimming with 'good
deals'.

>
> Are my knees going to instantly explode if I try riding 175 mm cranks?
>

Not unless you load your trousers with TNT.

Luke

 

[chalo colina]

Qui si parla Campagnolo wrote:
> Put three people in a room and ask about 'proper' crank length, get
> four opinions. If 170s work for you, stay with 170s..
> "if it ain't broke, yada, yada."

If 90mm cranks work for you, why not stay with 90s?

If you've only ever tried one crank length, you don't really know
whether it "works" for you, now do you?

As for the OP's question: if you're going to experiment, you may as
well go up or down by an increment you can clearly feel, e.g. 10mm or
more. And it's advisable to use your leg length as an indicator of
whether you should go longer or shorter. For instance, if you are
taller than a pro bike racer, you should experiment with longer cranks
than a pro bike racer would use.

If you are of average height, going from 170mm cranks to 175mm cranks
seems like a reasonable thing to do, considering how many slightly
shorter-than-average folks seem to prosper with 170mm cranks.

I have a very long inseam, and I really like my 196mm and 205mm cranks.
However, those carry limitations on acceptable BB height, so most of
my bikes use 185mm cranks as a compromise. One has 170s, another has
165s, and my big Big Wheel has 127mm cranks. They all work fine for
their respective uses, but I can apply more power and turn higher gears
by using a longer crank.

Chalo Colina

 

[David L. Johnson]

On Wed, 27 Apr 2005 20:29:59 -0400, Luke wrote:

> In article <[email protected]>, justareader
> <[email protected]> wrote:
>
>> Is there a rule of thumb for crank length that takes into account the
>> type of riding you do?
>
> The rule of thumb is to opt for the crank which is most comfortable.
> This is not meant as a facetious reply. I've a 32 inch inseam and
> consider 175mm arms too long; I'm most comfortable with 170mm cranks,
> but others with identical inseams harbor different opinions.

The type of riding also matters. I have three bikes (track, road,
mountain), and they have, respectively, 165, 170, and 175mm cranks. I
tried longer cranks on the fixed gear, and found them uncomfortable. I
was happy to go back to 165s (thanks, Sheldon).

But, oddly, I hardly notice the different crank lengths. Part of that is
that the crank length is part of the whole feel of the bike, and I do
expect different things from each.

To the OP: what crank length you want for the tourer will depend on a lot
of things. Some tourists kind of plod along under load, and others keep
up a high cadence. I'd imagine the fast-cadence types would prefer a
shorter crank, but the difference will not be a big deal.

--

David L. Johnson

__o | Deserves death! I daresay he does. Many that live deserve
_`\(,_ | death. And some that die deserve life. Can you give it to
(_)/ (_) | them? Then do not be too eager to deal out death in judgement.
-- J. R. R. Tolkein

 

[Qui si parla Campagnolo]

I guess my point is for the vast majority of riders out there, 5mm
incremental changes will make no real difference in riding.

Power out is power out, regardless of crank length.

Leverage may change but the power generated by your leg stays the same.

As an aside, i worked on a lady's DeRosa once that had 170s on one side
and 172.5 on the other and she didn't even know it.

 

[[email protected]]

your knee is a complex mechanism-check the anatomy book's overlays
for me at nearing 60 but 38 in shape
the knees have wear points
shifting sizes or seat post lengths
shifts the wear points
gotta berak it in

 

[Peter]

Qui si parla Campagnolo wrote:
> I guess my point is for the vast majority of riders out there, 5mm
> incremental changes will make no real difference in riding.
>
> Power out is power out, regardless of crank length.
>
> Leverage may change but the power generated by your leg stays the same.

I've found that to be true for me. My tandem has 165s, my folding
travel bike has 170s, and my usual road bike has 175s. I switch between
them and hardly notice any difference, but my typical cadence is
slightly higher on the tandem with the shorter cranks.

 

[Booker C. Bense]

-----BEGIN PGP SIGNED MESSAGE-----

In article <[email protected]>,
Qui si parla Campagnolo <[email protected]> wrote:
>I guess my point is for the vast majority of riders out there, 5mm
>incremental changes will make no real difference in riding.
>

_ Perhaps it's just hallucinations on my part, but I definitely
notice the difference in switching between two largely similar
steel bikes one with 165mm and one with 170mm cranks.


>Power out is power out, regardless of crank length.
>
>Leverage may change but the power generated by your leg stays the same.
>

_ I don't think it's that simple, nothing that involves human
biomechanics is. But I don't really care about
power, but long distance comfort. Even though the bike with
165mm cranks is heavier, I much prefer it for long rides.
Granted it is only 1cm difference in step height, but I think
that adds up over many thousands of steps.

_ While it's a fuzzy and potentially expensive experiment to
make, I think it's worthwhile to try. Even if it's only a
placebo effect, if you think you're more comfortable, you are.

_ Booker C. Bense

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[LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m]

Peter wrote:

>> Leverage may change but the power generated by your leg
>> stays the same.
>
> I've found that to be true for me. My tandem has 165s, my
> folding travel bike has 170s, and my usual road bike has 175s.
> I switch between them and hardly notice any difference

Same here: 170 on the tandems and the short recumbent, 175 on the MTB,
180 on the long recumbent, and I barely notice any difference. My wife's
bike has 165 cranks, however, and I would hate to do a long ride on it.

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

 

[Luke]

In article <[email protected]>, David L.
Johnson <[email protected]> wrote:

> On Wed, 27 Apr 2005 20:29:59 -0400, Luke wrote:
>
> > In article <[email protected]>, justareader
> > <[email protected]> wrote:
> >
> >> Is there a rule of thumb for crank length that takes into account the
> >> type of riding you do?
> >
> > The rule of thumb is to opt for the crank which is most comfortable.
> > This is not meant as a facetious reply. I've a 32 inch inseam and
> > consider 175mm arms too long; I'm most comfortable with 170mm cranks,
> > but others with identical inseams harbor different opinions.
>
> The type of riding also matters. I have three bikes (track, road,
> mountain), and they have, respectively, 165, 170, and 175mm cranks. I
> tried longer cranks on the fixed gear, and found them uncomfortable. I
> was happy to go back to 165s (thanks, Sheldon).
>
> But, oddly, I hardly notice the different crank lengths. Part of that is
> that the crank length is part of the whole feel of the bike, and I do
> expect different things from each.

Different folks, er, different cranks. At various times, I've had the
three crank lengths you mention as well as 172.5mm long arms installed
and though the others were by no means intolerable, I would still
return to 170s as the most comfortable. This despite the different
cranks being used for different purposes: fixed gear, touring,
MTBiking, recreational riding, etc.


> To the OP: what crank length you want for the tourer will depend on a
> lot of things. Some tourists kind of plod along under load, and others keep
> up a high cadence. I'd imagine the fast-cadence types would prefer a
> shorter crank, but the difference will not be a big deal.

Yes, the impact of different crank lengths tends to the subtle rather
than the extreme.
Luke

 

[Luke]

In article <[email protected]>, Qui
si parla Campagnolo <[email protected]> wrote:

> As an aside, i worked on a lady's DeRosa once that had 170s on one side
> and 172.5 on the other and she didn't even know it.
>

A few years ago I installed an RSX crankset bought from a bike show.
The vendor had them in a bin, left and right arm twist-tied together,
along with a few dozen other cranks. I rode them for several days but
they never *felt* right. I raised and lowered the seat; then moved it
fore and aft. I repositioned the cleats but nothing worked.

Then, when I went to verify that I had indeed purchased the right
length (170mm), I discovered that the right was 170 and the left 175.
Arghh!

luke

 

[Qui si parla Campagnolo]

My comment was for Chalo about power out. Cadence does change, leverage
and riding style may but how much 'power' your leg can produce is not
really determined by a crank length that may vary by 5-10mm per arm.

 

[chalo colina]

Qui si parla Campagnolo wrote:
>
> I guess my point is for the vast majority of riders out there, 5mm
> incremental changes will make no real difference in riding.

I think that's a fair assessment.

> Power out is power out, regardless of crank length.
>
> Leverage may change but the power generated by your leg stays the
same.

That is not true, in my opinion. If you have found it to be so, I
suggest that's because you have only tried crank lengths within a size
range so limited that it keeps you from noticing a difference.

If it's true, as you say, that crank length does not impose a limit on
power output, then racers ought to be able to use 2-inch cranks at 300+
rpm, generate the same amount of power as they do now, and enjoy
noticeable aerodynamic and handling benefits from a lower position.
But they can't do that.

There are upper and lower boundaries on the amount of force a rider can
put on the pedal, on how rapidly and efficiently he can reciprocate his
leg, and on how high he can "step" for a given amount of knee bend.
Those with long legs probably must work harder to reciprocate their
legs than riders of average size, but they can easily step higher. If
a tall rider's body size is in proportion to his height, then he can
also push the pedal harder than an average-sized rider. All these
things have implications for optimum crank length, gear ratios, and
cadence.

Just because a very tall rider can make do with a normal length crank
does not mean that such a crank allows him to develop his maximum
power, any more than a 140mm crank would allow an average sized rider
to do so if it were the only generally available choice.

The same principle applies to unusually short riders, too.

Chalo Colina

 

[justareader]

On 28 Apr 2005 07:54:52 -0700, [email protected] wrote:

>your knee is a complex mechanism-check the anatomy book's overlays
>for me at nearing 60 but 38 in shape
>the knees have wear points
>shifting sizes or seat post lengths
>shifts the wear points
>gotta berak it in

Good point, I would be lowering my seat a little which would leave
most of the change to the starting height of the down stroke. A hard
50 miler too soon could really leave the top of your knees sore.