if having to buy a bike on frame measurements alone, whats MOST important?

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reohn2
Posts: 39681
Joined: 26 Jun 2009, 8:21pm

Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby reohn2 » 31 Jul 2020, 9:43am

531colin wrote:
De Sisti wrote:Different length top tubes, so seats postions are adjusted accordingly.


This is the bit that I (and many others) can't do.
I need to sit a fairly precise distance behind the bottom bracket (although in reality I suspect plus/minus 5mm is close enough, as I move about on the saddle anyway).
Having set the saddle setback, reach is adjusted with different stem lengths.
Saddle setback is critical for me because it governs how much weight is on my hands, and what proportion of pedalling "work" is done by quads vs. hamstrings.
I'm sure I'm much fussier over this in my seventies than I was in my thirties; in my thirties I think I could jump on just about anything and ride it.

I agree,as I've got older(not quite 70 yet)saddle position has become more critical for comfort,especially on longer rides not just that but saddle shape and type though that's a subject for another thread.
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I cycle therefore I am.

Manc33
Posts: 1659
Joined: 25 Apr 2015, 9:37pm

Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby Manc33 » 31 Jul 2020, 2:49pm

I had the saddle on a seatpost with 50mm setback so it was 34mm further back than I had it on my Thomson - but it felt weird. There were also times it felt like I could accidentally pedal backwards, which seems odd considering the saddle position, I would have thought it would be the other way around (positioned to feel like pedaling forwards more) but no. I swapped back to my Thomson (it has 16mm setback) and all of a sudden it feels a lot better.

I'm sure my legs are short compared to my reach (going off the knee at 3 O'Clock plum line rule, with the line about an inch behind the pedals on a 16mm setback seatpost). Meanwhile I am always messing about trying to make the reach big enough.

I have seen people say the further back your saddle is, the comfier it is (because of weight on your hands?!) but to alleviate weight on my hands I just put a higher handlebar on and try to not mess with the saddle.

Other times I have had that 50mm setback is when the frame is too small for me (putting flat bars on a bike I had drops on etc).

You can experiment, but I have found deviating away from how it's always been done is always a step in the wrong direction.

The other problem is, bike manufacturers seem to think we are all racing, I mean if you buy a carbon frame, it's tailored to racing usually. What if we just want a lighter bike that soaks up the road vibration a bit better... they never thought of that? :roll: The days of people not being able to afford these "racy" frames is long gone!
When two cyclists get married, they should throw anodized cable crimps instead of confetti.

reohn2
Posts: 39681
Joined: 26 Jun 2009, 8:21pm

Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby reohn2 » 31 Jul 2020, 6:28pm

Manc33
The seatpost doesn't matter it's the saddle position in relation to the BB that does I find KOPS to be a good place to start with saddle position,only needing to tweek it slightly for optimum.
Once the saddle's set to optimum then and only then do you set the handlebars(whether drops or flats)to their optimum in relation to the saddle position.
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I cycle therefore I am.

Jamesh
Posts: 1326
Joined: 2 Jan 2017, 5:56pm

Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby Jamesh » 31 Jul 2020, 6:50pm

Manc33

There are carbon bikes that are slacker geometry and handling usually called endurance bikes synapse, Roubaix, etc.

It does seem counter intuitive that having a saddle futher back reduces load on the hands when a shorter reach would also reduce loads on the hands.


Cheers James

martinn
Posts: 343
Joined: 1 Dec 2012, 8:20pm

Re: if having to buy a bike on frame measurements alone, whats MOST important?

Postby martinn » 1 Aug 2020, 5:33pm

I put the measurements into the bike geometry calculator and then used the measurements from the spa site for the 58 and 56, tried to aim to have the saddle nose to BB distance, and the saddle nose to the end of the stem.
fading the one bike geometry over the other until the saddle and end of stem position were the same and didn't change, when toggling between the two.
the 56 seemed the better match, interestingly i then tried the 54...... that seemed to be an even better match, as long as I didnt mind a large amount of seat post showing, 20+cm, and 130cm stem..

think I will go for the 56

Martin