Choosing new bike size based on old bike.

by redbeard497   November 25, 2012  

Hey,

Now I ride a 58 cm Trek with the following geometry (in mm) :

Seat tube: 553
Head tube: 190
Frame reach: 391
Frame stack: 596
Chainstay: 441

"Effective top tube": 573

Seat angle: 73 deg
Head angle: 73.8

I ride it with a 90 mm stem (short arms!), +10 degrees, 1 cm spacer.

Saddle height to centre of BB is 81 cm.

For my new bike, I can only choose between 57 and 59 cm:

57/59:
Seat tube: 570/590
Head tube: 163/180
Frame reach: 394/397
Frame stack: 563/581
Chainstay: 406/406

Top tube: 560/575

Seat angle: 70/70 deg
Head angle: 73/73.5 deg

Before you ask, I am ordering it by mail so I can't really try it out. I understand that it's supposed to be a "racier" geometry, it's a lot more money as well!

So, which of the two should I choose? And with what stem and spacers? Any suggestions? Thanks!

7 user comments

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Based on that, If your legs are ok with reaching the little bit further, I'd go with the 59 and then get a slightly shorter stem, maybe a 75mm. Unsure about spacers though Nerd

Gkam84's picture

posted by Gkam84 [8140 posts]
25th November 2012 - 23:59

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Based on the top tube, Id say the larger of the options as it matched your existing closest. Youc an always put a seat post up but theres only so much you can add in a stem.

I ordered my new bike in much the same way but I used measurements form ground as they are more relevant. I actually bought a small frame where I was riding a large as I needed a slightly shorted top tube, seemed really small at the time but its paid off...no more lower back pain.

I used an app called size my bike and it created a sound base that pointed out what I knew, that my frame was too long for me, but it also suggested a starting point that made me realise i should look at smaller frames so its fairly good.

Looks like your existing frame is a lot mroe upright and the new one more racing designed but its meaurements from the ground that will tell you that. Only thing that remains fixed is top tube and seat tube, the rest are design.

posted by Farky [174 posts]
26th November 2012 - 13:28

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If the seat angle on the new frame is really 70 as you quoted then both those frames will be too short in the top tube compared to the trek. you could possibly get around that by getting the larger size and running a longer stem + 3 cm or so over the trek

70 does seen very slack though, I'd check that first.

posted by TheDoctor [63 posts]
28th November 2012 - 13:59

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TheDoctor wrote:
If the seat angle on the new frame is really 70 as you quoted then both those frames will be too short in the top tube compared to the trek. you could possibly get around that by getting the larger size and running a longer stem + 3 cm or so over the trek

70 does seen very slack though, I'd check that first.

You're right, it's actually 73 too! I'm sorry, I don't know where I was looking, really...

posted by redbeard497 [13 posts]
28th November 2012 - 16:14

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are you buying a Canyon per chance?

posted by londonplayer [671 posts]
28th November 2012 - 17:42

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It's a similar company: ROSE. rosebikes.co.uk

posted by redbeard497 [13 posts]
28th November 2012 - 18:49

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how tall are you Redbeard?

posted by londonplayer [671 posts]
29th November 2012 - 20:01

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