Crank size difference--will it really help?

I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I was
getting refitted to the bike to help with numbness in my hands and we ended
up moving the seat position and also raising the handlebars. After we did
that it was suggested that I should really be riding on 165mm cranks because
I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter cranks?

How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the gears (it
is a triple) with the cranks as a set?

Thanks in advance...

Chuck

I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I was
getting refitted to the bike to help with numbness in my hands and we
ended up moving the seat position and also raising the handlebars. After
we did that it was suggested that I should really be riding on 165mm
cranks because I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter cranks?

How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the gears
(it is a triple) with the cranks as a set?

Thanks in advance...

Chuck

Chuck: Hard to believe you'd fit a 5200 that came (stock) with 172.5mm
cranks and have legs short enough to justify 165mm. Rarely do I find someone
that would fit even a 50cm bike that would benefit greatly from 165mm
cranks... generally, that would be more likely for the length of leg seen on
a 48cm or smaller. Generally; your mileage may vary.

You can buy just crank arms, but I wouldn't, as a pair of crank arms cost as
much, or more, than a new set of cranks. Given that chainrings do wear out,
the new set would make more sense. But I wouldn't go to 165mm without trying
some first. Changing them out is no big thing; in fact, on Ultegra, all
you'll need is an allen key (8mm? Not at the shop right now, so I don't have
one to look at).

But we really need to know how tall you are, what your inseam is, and maybe
even the size of bike (just to get an idea how the whole package fits
together).

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

"caaron" wrote in
:

I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I
was getting refitted to the bike to help with numbness in my hands and
we ended up moving the seat position and also raising the handlebars.
After we did that it was suggested that I should really be riding on
165mm cranks because I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter
cranks?

How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the
gears (it is a triple) with the cranks as a set?

Thanks in advance...

Chuck



I think Sheldon's a fan of 165s, at least for fixies.

From http://sheldonbrown.com/harris/cranks.html

"165 mm is Good!
We generally recommend 165 mm length cranks for road fixed-gear use.
This shorter length makes it easier to spin faster cadences, and also
reduces the risk of striking a pedal while cornering (with a fixed gear,
where you have to pedal through the corners, this can be an issue.)"

The 5200 was last made with the Ultegra 6503 crank, which was the last
of the 3-piece models. I'm assuming that's the model you have.

Depending on whether you have integrated pullers currently, it could be
as simple as using an 8mm allen wrench and 15mm pedal wrench to make the
switch. At worst, you'd also need an octalink-compatible puller,
probably $10-15.

You'd be best off buying the complete crankset and getting new rings.
The right arm alone is only $20 cheaper than the whole set.

This, of course, assumes you can find a place that still has the
6503/165 in stock, because I don't think QBP has them anymore.

I guess Airbomb claims to have them, $175.99

http://store.airbomb.com/ItemDesc.asp?IC=CR6340

Another option would be to get a Sugino XD600 and a Shimano UN-73 Bottom
bracket, for a little more than half the price of the Ultegra crank. It
has 46-36-26 rings, but some lower gears would be good with the shorter
crankarms.

caaron wrote:
I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I
was getting refitted to the bike to help with numbness in my hands
and we ended up moving the seat position and also raising the
handlebars. After we did that it was suggested that I should really
be riding on 165mm cranks because I have short legs. I'm seeking
opinions
Will there be a noticeable difference in performance with shorter
cranks?
How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the
gears (it is a triple) with the cranks as a set?

Thanks in advance...

Chuck

We need more data. What is your inseam and height?

I'm 5'5", 29" inseam, ride a 48cm bike that came equipped with 165mm cranks
and it was surprising how much I struggled on the first ride to keep up with
the group. I switched them out for 172.5s and I was happy... happy as a...
hippo. Then again, I had been using 172.5s before and probably had some
muscle memory.

--
Phil, Squid-in-Training

On Sun, 25 Sep 2005 16:56:52 -0500, Hank Wirtz wrote:

I think Sheldon's a fan of 165s, at least for fixies.

This is standard belief -- and in this case has some truth to it. I'm
5'11", and started out with 170s on the road bike, 165s on the track, back
in the early '70s. about 5 years ago I tried longer cranks on the track
bike (usually ridden on the road), but went back to the 165s. I feel that
I can spin better with the shorter cranks.

--

David L. Johnson

__o | The lottery is a tax on those who fail to understand
_`\(,_ | mathematics.
(_)/ (_) |

On Sun, 25 Sep 2005 16:47:21 -0400, caaron wrote:

I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I was
getting refitted to the bike to help with numbness in my hands and we ended
up moving the seat position and also raising the handlebars. After we did
that it was suggested that I should really be riding on 165mm cranks because
I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter cranks?

Well, that is a big jump, so, yeah, you probably will notice the
difference. How short are your legs? Usually it does not matter all that
much what crank length you use; you will become accustomed to what you
have. But for really long or short legs, it might be worth dealing with.


How hard is it to change out Ultegra cranks--do I need special tools?

A couple. You need a crank puller. This is a small tool that is quite
inexpensive. Much less expensive than the cranks themselves. You have to
know what sort of crank you have (year, not just model), to get the right
one.


Do I change the cranks themselves or do I also have to change the gears
(it is a triple) with the cranks as a set?

You may be able to find just the arms, but you will have to search for
them. More commonly they come with rings. How old are the current ones?
How much wear do they have? Maybe it would be worthwhile to change them.
Worst case scenario is that you would have extra rings for when the
current ones wear out, if you can't find bare cranks.


--

David L. Johnson

__o | "It doesn't get any easier, you just go faster." --Greg LeMond
_`\(,_ |
(_)/ (_) |

I ride a 2001 Trek 5200 that is 54cm. I'm 163# and just short of 5'9" tall
and have a long torso and short legs. My inseam is 30" and the distance
from the top of my femur to the floor is 89cm. Based on Peter White's
18.5% calculation guideline, 165mm cranks would be just right. Similar
calculations from Ergobike (edward ZImmermann's bicycle sizing site) also
come out at 165mm.

Previously I had a 58cm Trek 5200, which I found too big to ride
comfortably, so I got the 54cm Trek a few years ago and it seems to be a
better fit. At age 60 I find I need the handlebars higher for comfort and
I'm a recreational rider, not a racer, so my rides average about 15mph.
I've always had trouble spinning fast, and although I can get up into the
high 90's I find my average cadence is in the low to mid-eighties on most of
my road rides. So I was wondering if changing over to the 165mm cranks
would make enough of a difference in comfort and cadence to make it
worthwhile to do the change and what downside there might be, if any...

Thanks for the replies

Chuck


"caaron" wrote in message
...
I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I was
getting refitted to the bike to help with numbness in my hands and we
ended up moving the seat position and also raising the handlebars. After
we did that it was suggested that I should really be riding on 165mm
cranks because I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter cranks?

How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the gears
(it is a triple) with the cranks as a set?

Thanks in advance...

Chuck

"caaron" wrote in message
...
I've been riding my Trek 5200 with 172.5 Ultegra cranks. Recently I was
getting refitted to the bike to help with numbness in my hands and we
ended up moving the seat position and also raising the handlebars. After
we did that it was suggested that I should really be riding on 165mm
cranks because I have short legs. I'm seeking opinions

Will there be a noticeable difference in performance with shorter cranks?

How hard is it to change out Ultegra cranks--do I need special tools?

Do I change the cranks themselves or do I also have to change the gears
(it is a triple) with the cranks as a set?

Thanks in advance...

Chuck

When I got my new bike, I begin to worry whether I had the correct crankarm
length. I considered spending hundreds of dollars to replace my brand new
excellent crankset. I read lots of different ideas about what is the
correct crankarm length based on lots different inputs - your size, style of
riding, etc.

Then I realized that the "experts" can't even agree what is the right size.
Also, I noted this fact:

The difference between 172.5 and 165 is 7.5 mm - or about 4%. I wondered
whether I could even feel a 4% difference in crankarm length in a blinded
test. I decided that for me, a few percentage points difference in crankarm
length could not possibly be worth hundreds of dollars for a new crankset.

Just my 2 cents. Your mileage may vary.

BobT

caaron wrote:
So I was wondering if changing over to the 165mm cranks
would make enough of a difference in comfort and cadence to make it
worthwhile to do the change and what downside there might be, if any...

You have to try them and see; there are lots of personal history
stories inre crank length-- short folks happy on 175's, tall ones happy
on 165's, and so on. I went to 165's for "everything" because I was
living near a track and wanted to use the same length all the time
("every little bit helps"). Surprisingly, my knees stopped having a
certain soreness that occurred regularly after hard rides when I used
172.5's. Not an expected result, and FWIW the knees, which have been
iffy for a good long time, have been doing better with 165's for about
five years now. "Works for me".

Park Tool has a "help" section inre bike maintainance. You'll note that
cranks have to be torqued pretty substantially. Sears has inexpensive
torque wrenches, I've seen your crank in 165 length go v. reasonably
priced on ebay, etc etc.; likely nothing you can't do yourself. And
then sell the ones you don't want g.

IMHO, don't let concerns about cadence take away from your riding
enjoyment. Work with it if you want, "spin-ups", telephone pole spins,
etc., but NBD except to make it easier to cope with speed variations in
racing or fast group rides. --D-y

I ride a 2001 Trek 5200 that is 54cm. I'm 163# and just short of 5'9" tall
and have a long torso and short legs. My inseam is 30" and the distance
from the top of my femur to the floor is 89cm. Based on Peter White's
18.5% calculation guideline, 165mm cranks would be just right. Similar
calculations from Ergobike (edward ZImmermann's bicycle sizing site) also
come out at 165mm.

Previously I had a 58cm Trek 5200, which I found too big to ride
comfortably, so I got the 54cm Trek a few years ago and it seems to be a
better fit. At age 60 I find I need the handlebars higher for comfort and
I'm a recreational rider, not a racer, so my rides average about 15mph.
I've always had trouble spinning fast, and although I can get up into the
high 90's I find my average cadence is in the low to mid-eighties on most
of my road rides. So I was wondering if changing over to the 165mm cranks
would make enough of a difference in comfort and cadence to make it
worthwhile to do the change and what downside there might be, if any...

Thanks for the replies

Chuck

What are you using for saddle height (measured from center of crank to top
of saddle)? Traditional wisdom would be around 66cm if I'm figuring
correctly, which, on a 54cm Trek, would place the top of the saddle 13-14cm
above the top tube (or 12cm above the seat collar, which extends above the
top tube a bit and represents the measuring point for frame size on a 5200).

Those all sound like pretty normal measurements (if they're reasonably close
to what's on your bike). If so, I find nothing there to indicate that
there's any "need", based on leg length, for a shorter crank. You might wish
to try one for the heck of it, but I'm not sure what symptoms need to be
addressed, particularly in light of your stated RPMs which are *not* at the
low end. Low-to-mid-80s are perfectly acceptable for most people; not
everyone does well spinning like Lance.

I'm also somewhat concerned by what sounds like a hit-and-miss approach to
fit. How did you end up initially with a 58cm frame? When I mock that one
up, it looks like the saddle would be almost sitting on top of the top tube.
You're potentially over-compensating and swinging from one extreme to the
other, when someplace in the middle might be just about right.

But getting down to the effects of shorter cranks- generally, you'll be able
to spin a bit more (because the crank is traveling through a smaller circle,
so your feet aren't actually moving as far/fast per revolution), but you'll
also be losing some leverage, which could be an issue climbing. In general
there's a trend toward longer cranks these days, seemingly with little
downside (we're not seeing more knee injuries today than back-in-the-day,
even though there are more people serious mile now than back then).

Good luck, and let us know how the experiment turns out-

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com