Comopact Frame Sixing & Saddle

"Paul" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On my previous bike, which I was fitted for using a jig, the crank was a
172.5 and resulted in a recommended saddle height of 761 cm from the

centre

Quoted message said:

of the BB to the top of the saddle. Having previously had a major problem
with numb nuts this fitting, in conjunction with fitting a Selle Flight
saddle, really solved my problem. Until some scrote nicked the bike I had
set up perfectly....

However I now have a new bike (Giant OCR2) with which my problem has
returned with a vengeance - 16 miles today and there's no doubt about it -
something's wrong. I have again stuck a Selle Flight on the bike but note
that the frame is far far more compact than my previous one and has a 170
crank. I had therefore assumed that the original calculation of BB -

saddle

Quoted message said:

= 761 cm should just be reduced by 25 cm to achieve parity, given the
shorter crank length - not the case. My frame size is medium and this set

up

Quoted message said:

hasn't worked, so I need some help.

As a layman's guide, when sitting on the bike with the crank at its

nearest

Quoted message said:

to the floor, am I correct on saying that with my heel on the pedal then

my

Quoted message said:

leg should have only a very subtle bend in the knee? I have re-adjusted

the

Quoted message said:

saddle height this evening and it feels like I am sitting on the correct
bones rather than the bits I shouldn't be. If I am right (and I am no
techie) then compact frames can really throw out your usual assumptions.

To be honest I am totally fed up with it - tried countless saddles and set
ups but still having the same problem, which is worrying and a REAL issue.
If I can't solve it I am honestly considering selling up and giving up
cycling altogether. That's not a dummy spit - just a measure of the
discomfort I am constantly experiencing. My LBS have been really helpful
and are as baffled as I am.

All help appreciated, as ever.

Cheers,

Paul

Typo - 761cm etc should read 761mm. I am not that big!!

Paul said:

On my previous bike, which I was fitted for using a jig, the crank was a
172.5 and resulted in a recommended saddle height of 761 cm from the centre
of the BB to the top of the saddle. Having previously had a major problem
with numb nuts this fitting, in conjunction with fitting a Selle Flight
saddle, really solved my problem. Until some scrote nicked the bike I had
set up perfectly....

Quoted message said:

To be honest I am totally fed up with it - tried countless saddles and set
ups but still having the same problem, which is worrying and a REAL issue.
If I can't solve it I am honestly considering selling up and giving up
cycling altogether. That's not a dummy spit - just a measure of the
discomfort I am constantly experiencing. My LBS have been really helpful
and are as baffled as I am.

There is more to this than leg length and crank length. Are the handlebars
the same distance below the saddle? are they the same distance away? Are you
sitting in the same relative position over the bottom bracket?

All these things are worth examining to see if they can replicate your old
position on the bike.

...d

On Sat, 02 Oct 2004 22:35:13 +0100, David Martin
<[email hidden]> wrote in message
<[email hidden]>:

Quoted message said:

There is more to this than leg length and crank length. Are the handlebars
the same distance below the saddle? are they the same distance away? Are you
sitting in the same relative position over the bottom bracket?

I bet not on a compact bike; I would look first at handlebar height
and saddle angle. Even very small tweaks to the angle of the saddle
can make big differences to comfort IME.

It's quite likely the frame angels [ToBAGO] are different, too. I
would suggest a computerised frame fit (my LBS does this for free if
you buy a bike).

But what do I know? I have waved goodbye to sore [censored] misery with
New! Improved! Recumbent :-)

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

in message <[email hidden]>, Paul

(') said:

"Paul" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On my previous bike, which I was fitted for using a jig, the crank
was a 172.5 and resulted in a recommended saddle height of 761 cm
from the

centre

Quoted message said:

of the BB to the top of the saddle.

However I now have a new bike (Giant OCR2) with which my problem has
returned with a vengeance - 16 miles today and there's no doubt about
it - something's wrong. I have again stuck a Selle Flight on the bike
but note that the frame is far far more compact than my previous one
and has a 170 crank. I had therefore assumed that the original
calculation of BB -

saddle

Quoted message said:

= 761 cm should just be reduced by 25 cm to achieve parity, given the
shorter crank length - not the case. My frame size is medium and this

Typo - 761cm etc should read 761mm. I am not that big!!

You made the same mistake twice. A 172.5mm crank is 2.5mm longer than a
170mm so if your 761mm should be reduced it should be reduced not by
25cm not by 2.5cm but by 2.5mm; my bet is that you've got it 22.5mm too
low, which is quite a lot. Actually I don't think it should be reduced
at all but either left at 761mm or increased to 763.5mm, because the
critical distance is not that to the top of the pedal rotation but that
to the _bottom_ of the pedal rotation, which is now 2.5mm nearer to,
not further from, your saddle.

The distance from your saddle to your handlebars, not just horizontally
but also vertically, wants to be right too.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

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