What size bike frame - Advice Please

iammap
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What size bike frame - Advice Please

Postby iammap » Wed Dec 07, 2011 8:39 am

I am starting to look at buying a drop bar roadie to commute to and from work on a semi regular basis.The distance to work is 50k

I am not sure what size bike frame I should be looking at, since I am 182.5cm tall but only have an inseam of 79cm. According to the sizing chart at ebicycles I should fit a frame size of 57 to 59 for my height, but my inseam suggests I should be looking at a frame size of 54.

What frame size would be best and what could I change to ensure the bike fits me properly.

Thanks in advance
Michael

TDC
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Re: What size bike frame - Advice Please

Postby TDC » Wed Dec 07, 2011 10:00 am

Check this site out. It is quite helpful, and can steer you in right direction.

http://www.competitivecyclist.com/za/CC ... ATOR_INTRO

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sherlock
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Re: What size bike frame - Advice Please

Postby sherlock » Wed Dec 07, 2011 10:15 am

Top tube/seat tube length should not be relied upon as a sole measurement. Stack/reach are what's important, but to be honest, just go to a shop and try a few bikes. You'll narrow things down fairly quickly.

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jacks1071
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Re: What size bike frame - Advice Please

Postby jacks1071 » Wed Dec 07, 2011 10:18 am

iammap wrote:I am starting to look at buying a drop bar roadie to commute to and from work on a semi regular basis.The distance to work is 50k

I am not sure what size bike frame I should be looking at, since I am 182.5cm tall but only have an inseam of 79cm. According to the sizing chart at ebicycles I should fit a frame size of 57 to 59 for my height, but my inseam suggests I should be looking at a frame size of 54.

What frame size would be best and what could I change to ensure the bike fits me properly.

Thanks in advance
Michael


In a Pro-Lite you'd be a size 54.

Different brands however use different geometry and different ways of sizing the bikes so you can't really compare them with the size number - you really need to look at the geometry charts.
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Nobody
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Re: What size bike frame - Advice Please

Postby Nobody » Wed Dec 07, 2011 10:58 am

sherlock wrote:Top tube/seat tube length should not be relied upon as a sole measurement. Stack/reach are what's important...
True, but the calculator posted by TDC above doesn't have an output in reach and stack. Reach and stack is mainly helpful if you already have a road bike to take measurements from.

Iammap,
Just keep in mind that the output from the calculator (effective top tube) is with reference to average frame angles. The seat tube angle is going to make far more difference than the head tube angle. For example, if the seat tube angle is lower in value than average for a bike of your size, then the reach for the same ETT is going to be slightly shorter.
http://www.rivbike.com/v/vspfiles/asset ... xcerpt.pdf

Having said that, I have personally used the calculator above for two bikes and got remarkably good results from it.

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Re: What size bike frame - Advice Please

Postby TDC » Wed Dec 07, 2011 12:30 pm

Michael,

I have the same inseam measurement as you, but am only 169 cm tall. A 57 or 59 cm bike could be a problem for you with regards to saddle height, and also with the corresponding head tube length. ie seat will be very low and n relation to the handlebars which will be high.

You might need a frame that has a long top tube and comparatively short seat tube & head tube.

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Re: What size bike frame - Advice Please

Postby satanas » Fri Dec 09, 2011 10:33 pm

Stack and reach are useful, but do not give the whole story as they only relate the position of the top of the head tube relative to the bottom bracket. Seat position is ignored, so if you need a particularly forward or (more likely on a road bike) rearward position, stack + reach don't help, and one needs to look instead at seat angle, seat post offset (not often stated in an understandable or standard format) and saddle rail length and position.

Ultimately *all* dimensions need to be considered to be sure a frame will fit, and hopefully without needing extra long or short stems or weird seatposts.

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Re: What size bike frame - Advice Please

Postby Nobody » Fri Dec 09, 2011 10:55 pm

satanas wrote:Stack and reach are useful, but do not give the whole story as they only relate the position of the top of the head tube relative to the bottom bracket. Seat position is ignored, so if you need a particularly forward or (more likely on a road bike) rearward position, stack + reach don't help, and one needs to look instead at seat angle, seat post offset (not often stated in an understandable or standard format) and saddle rail length and position.

Ultimately *all* dimensions need to be considered to be sure a frame will fit, and hopefully without needing extra long or short stems or weird seatposts.
Agree, but taking all angles into consideration can be a bit daunting for a first timer.

Being short, I've got the problem you describe above with saddle position, but I find almost all frames for my ETT have either 74 or 74.5 degree STAs. So because I have a Brooks Pro and 165mm cranks to complicate matters, I've ordered a seatpost with a 40mm setback. I could get a custom frame, but the seatpost is far cheaper.

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Re: What size bike frame - Advice Please

Postby Nobody » Sat Feb 04, 2012 11:22 pm

I'd thought I'd add the Baum geometry diagram here as it shows most important measurements clearly.
Image
http://www.baumcycles.com/bikes/espresso

I also noticed from my measurements with the Surly CC, that the Baum with almost the same ETT (TT above) of 53cm has a reach 2.2cm shorter than the Surly. Shows what a difference 1.5 degrees of STA can make. I'd prefer the Baum's 73 deg STA, but it's just a wee bit out of my price range. :|

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Re: What size bike frame - Advice Please

Postby Nobody » Wed Feb 06, 2013 11:16 am

Because I can't edit the statement in post above, I'll correct it here to say it probably should be closer to 1.5cm difference, rather than 2.2cm.

Also adding this useful explanation of effective reach and seat tube angles from Rivendell.
http://www.rivbike.com/v/vspfiles/asset ... xcerpt.pdf

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