Classic 'Help me fit' Thread

Questions about purchasing bicycles and parts

Classic 'Help me fit' Thread

Postby TomBikes » Tue Dec 04, 2012 8:50 pm

G'day everyone,

Longtime stalker, first time poster. Been looking around and this looks like a great website. I really want to get into cycling and am in of a new bike (my bmx just doesn't cut it when i try to slug it up a hill). I'm planing to purchase a cyclo-cross bike as an all round bike for commuting, getting around and a little bit of trail riding (nothing that would need a mountain bike). I plan to buy a Masi Speciale CX Comp for $900. I have an instem of 80cm and a height of 171cm. I read that a 54cm frame would be best but i can only get a 53 or 56 in this model ( http://www.urbanvelocity.com.au/bikes/c ... -2013.html ). Could i get away with the 53 or 56 or should i keep on searching. I am still growing though which is another reason why i don't want to burn a whole in my pocket for a first bike.

Other suggestions are highly appreciated!

Tom
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by BNA » Tue Dec 04, 2012 9:37 pm

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Re: Classic 'Help me fit' Thread

Postby Nobody » Tue Dec 04, 2012 9:37 pm

If I was you I'd get a secondhand bike since you are still growing.

If you do the calculator below, it should give you a better idea as to what your best effective top tube length (ETT) is.
http://www.competitivecyclist.com/za/CC ... ATOR_INTRO

I have the same inseam and I'm 1 cm taller. I have a 53cm top tube with a 74.5 degree seat tube angle, but short stem length. For every degree of seat tube angle above 73 degrees, add ~1cm to the ETT because that is how the effective reach of your arms is affected. The CX comp geometry chart says ETT is 53.5 plus it is 73.5 degree seat tube angle (add 0.5cm). So has a total of 54cm effective reach of the top tube for that bike.

I guess you thought all this fit stuff was going to be easy. :)
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Re: Classic 'Help me fit' Thread

Postby jacks1071 » Tue Dec 04, 2012 10:25 pm

You've not posted a link to the geometry for the frame you are looking at.

Someone your height for a road geometry frame I'd be looking for at top tube around 52.5cm.

The best way to size a bike is to actually get on it had have a fit done.
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Re: Classic 'Help me fit' Thread

Postby Nobody » Wed Dec 05, 2012 7:29 am

jacks1071 wrote:You've not posted a link to the geometry for the frame you are looking at.
It's in my post above.

jacks1071 wrote:Someone your height for a road geometry frame I'd be looking for at top tube around 52.5cm.
True, but being such a small frame, seat tube angles vary a lot between brands and models and play a role in overall size. Mine is actually a 52.8mm, but with a 74.5 degree STA it is more like 54.3mm, so I have a short stem and a large setback seatpost (45mm). From what I've seen previously, the fit calculator above assumes a 73 degree STA, which is unlikely in the real world with small frames unless you are getting a custom. I think Baum and Rivendell maintain a ~73 degree STA for small frames. Anyway, I've just bought the old LeMond book on which the fit calculator is partially based to see what the STA actually is (if it specifies).
http://www.rivbike.com/kb_results.asp?ID=73

jacks1071 wrote:The best way to size a bike is to actually get on it had have a fit done.
True, but is it worth paying the money for a proper fit if you're still growing?
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Re: Classic 'Help me fit' Thread

Postby TomBikes » Thu Dec 06, 2012 10:08 pm

Well, im still growing a little, not enough to warrant a cheapo bike, but enough to make anything pricey out of the question. I think the 53 frame should be just fine with the right fit. Thanks
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Re: Classic 'Help me fit' Thread

Postby Baalzamon » Sat Dec 08, 2012 12:54 am

I have a Masi Speciale CX 2008 in 56. I'm 183cm and it fits me perfect. I suggest you try both but 56 may be too big for you
Masi Speciale CX 2008 - Brooks B17 special saddle, Garmin Edge 810
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