Geometry choice - please help!

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KH
Posts: 196
Joined: Fri Feb 27, 2004 3:56 pm

by KH

For logistical and financial reasons I need to make a decision on a new bike today. I am clueless about geometry so any help would be very gratefully received.

The bike I have just broken (56cm) was a perfect fit. The key geometry stats for that bike were:

Effective top tube: 560mm
Seat tube: 540mm
Headtube: 155mm
Stack: 560mm
Reach: 394mm

All angles etc are pretty much the same as for the new bike I am looking at. The issue is that my old 56cm bike would sit somewhere in between the 54cm and 56cm sizes for the new bike I am looking at. I realise that bike fitting over the internet is dubious at best but I'm really struggling to make a decision today and I won't have a chance to test ride. For the new bike these are the geometry stats:

54cm:

Effective top tube: 549mm
Seat tube: 540mm
Headtube: 135mm
Stack: 537mm
Reach: 390mm

56cm:

Effective top tube: 565mm
Seat tube: 560mm
Headtube: 160mm
Stack: 565mm
Reach: 398mm

Is it possible from just those key stats to determine with a reasonable degree of accuracy whether the 54cm will be too small or the 56cm too big? Which do you think is the closest match to my old bike.

Thanks for reading and I await the wisdom of the resident geometry gurus on here!

by Weenie


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CPongpanich
Posts: 100
Joined: Wed Nov 11, 2015 9:36 am
Location: Yorkshire, UK / Bangkok, Thailand

by CPongpanich

That's tricky. I'm by no mean a guru in geometry but I'll suggest you to go for the smaller one - the 54. As with small frames, you have more flexibility afterward, eg. extend the stem length. But with larger frames, you tend to be stuck with it.

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wheelsONfire
Posts: 6283
Joined: Mon Jul 07, 2014 8:15 am
Location: NorthEU

by wheelsONfire

The 56 sized is only 5mm higher than your previous bike (stack).
The bar will be 4mm further forward (reach).
You could change headset top cap for a lower (see link below) and either you handle the 4mm longer reach, or you change to a handlebar with shorter reach.

Here is the lower headset covers
http://www.certifiedslammed.com/#_=_
Bikes:

Ax Lightness Vial EVO Race (2019.01.03)
Open *UP* (2016.04.14)
Paduano Racing Fidia (kind of shelved)


Ex bike; Vial EVO D, Vial EVO Ultra, Scott Foil, Paduano ti bike.

Tenlegs
Posts: 289
Joined: Wed Jul 16, 2008 10:37 am

by Tenlegs

Include in your Key geometry stats details like stem length and angle, how many spacers if any?
seat tube angle

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Mr.Gib
Posts: 5577
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

if your broken bike was indeed a perfect fit, the new 56 can also be a perfect fit with some very minor tweeks. The 54 not so much.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.


fignonsbarber
Posts: 146
Joined: Fri Jun 25, 2010 10:24 pm

by fignonsbarber

Also need to consider what your saddle height is, and how many spacers you had on the broken bike. The only reason to not go with the 56 is if your old bike had a very low saddle height and/or lots of spacers (the 54 has a 2cm shorter HT than your bike).

KH
Posts: 196
Joined: Fri Feb 27, 2004 3:56 pm

by KH

Thanks very much for all your input; really appreciate it and you have helped to clarify my thoughts.

I have gone for the 56cm. I had a fair amount of seat post showing on my old bike and I also had a 120mm stem.

I will be sure to post the eventual build in a week or two on here once I have swapped out some parts!

tinozee
Posts: 764
Joined: Wed Jun 01, 2011 7:53 am

by tinozee

the 56

edit - oops just saw you decided. Enjoy new frame.

KH
Posts: 196
Joined: Fri Feb 27, 2004 3:56 pm

by KH

Thanks! Always good to get a little extra reassurance!

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



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