fwiw I am 5'11" and ride a 56 road bike (albeit with a 90mm stem), and a 54 cyclocross.
Looking at the geometry for that bike, (and noticing the sloping top tube and difference between seat tube, top tube and effective top tube measurments) I would be umming and ah-ing between 52 and 54cm frames. I wonder what size stem they supply on what size? If it handled OK with a 100-110mm stem I would be trying the smallest one first even though I am not exactly short!
Their effective top tube number gets closer to the seat tube length the bigger you go, they are both 60cm on the biggest size) but it is curious that their smallest size seems the same as some manufacturer's third smallest/medium ones. For example there are three sizes of the 2014 cannondale caadx (also an alloy disc cx bike) that are smaller than the smallest RX9. 😯
I've got a Trek Alpha somethingorother in 52, and Specialized Langster in 54, there's less than 2mm difference in top tube length on them.
It depends how he is proportioned, and flexibility, and personal preference too, so go by the actual fit, not the numbers.
I'm 5'8 FWIW and have shortish legs but a longer torso, I have barely any seatpost sticking out on either frame, to look a them you;d think I need a 50 but I had to go bigger for the TT length.
I'm 5' 11" and, looking at the numbers, I'd probably pick a 52 Orange - it's got a 54cm ETT,
I ride 565 tt road bikes and 550 tt cx bikes and I'm 5'8"
You're not wrong, this is just to point out how personal sizing is - I'm 6ft, typically ride bikes that suit an average 5'11-6' rider and I couldn't ride anything as short as 540mm for long, and prefer a road or CX type bike with approx 565-570mm TT, similar to someone 5'8" here. I'd look for around 390-395mm reach to start with, not a TT number (since reach can vary +/- 10mm between bikes with the same TT due to front end height and seat angle variations etc). Then there's stem length, saddle position etc. A shorter / smaller CX bike wouldn't let me use a shorter-than-road spec stem and may have toe overlap.
So in summary trying to size a bike by height alone is a bit ambitious.
I'm currently looking at buying a Kinesis Aithein frameset. Based on effective 55cm TT length and 14cm stack I've worked out I need buy a 53cm. I'm 6'1" and Kinesis recommend this size for riders who are between 5'5" and 5'9". But if my calculations are correct (and of course I've double checked them) this will give me, when coupled with a 13cm stem, an 8cm saddle-to-handlebar drop and perfect reach. But then I do have diddy little 31.5" legs.
And nearly forgot to mention - I have a 25mm lay back on the saddle - which adds an extra 25mm to my reach.
Facts: Bike fit dependant on many things, not just height.
long torso, short legs bigger frame.
short torso, long legs smaller frame.
That bike though it says 52 on it should fit like a 54.
trust the shop, they probably know what they're talking about.
Numbers are pointless. Try it on and if it feels right buy it.
The other issue which nobody seems to have picked up on is that the OP suggests his brother has limited knowledge of road bikes. Now I don't know what experience he has of other bikes, but I'd reckon to be selling a smaller size to a lot of mountain bike riders compared to road riders of exactly the same size. Possibly smaller again if he has little experience of riding. This is on the basis that the only important dimension is top tube length, and somebody inexperienced and not used to riding with a flat back and a lot of hip angle is likely to want a significantly shorter reach.
Personally I'm 5'9" and ride bikes with exactly the same dimensions as aP up there, and also 120/110 stems on the roadie/CX, but would be extremely surprised if somebody inexperienced of my height was comfortable on my bikes (I also run plenty of saddle/bar drop - slammed stem on my roadie 8) ).
Numbers are pointless. Try it on and if it feels right buy it.
Not necessarily, if your not used to riding bikes what feels right for you in a car park test or sit on in the shop may be uncomfortable for anything over 15 miles.
Saying someone is 5'10" so they must ride a 54 is pointless.
Don't forget ridley size their seat tube c-c whereas most size c-t
So a 52 ridley x fire (cross bike) is in fact a 56
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http://www.ridley-bikes.com/be/en/bikes/4/148/46/cyclocross/x-fire-10-1403a
54cm effective top tube looks about right for a CX bike at 5'9" - 5'10". Recommendatins are 1 - 3cm shorter top tube for cross - stops the front end washing out.
However, if he's going to use it just for road riding/commuting may go up a size to 55.5cm top tube - wouldn't go any longer!
Of course all the people saying what height they are and what size bike they are riding may not be on the right size frame themselves .
LenBuch - Member
54cm effective top tube looks about right for a CX bike at 5'9" - 5'10". Recommendatins are 1 - 3cm shorter top tube for cross - stops the front end washing out.
Does that assume uniform arm/torso/leg length?
When I bought my Cannondale CX, the shop guy said I should go for the 54cm, I took it for a ride and it felt ok. I said can I try the next size up, just to compare.. Rode it, wasn't as comfortable as the 54, so I bought the 54. I'm dead clever, me.
[quote=Ramsey Neil ]Of course all the people saying what height they are and what size bike they are riding may not be on the right size frame themselves .
Of course not, but fit being such a personal thing, some of us know we get on with the size we have - a proper fitting is unlikely to make a different size righter. On the flipside, for the same reason (and also the reasons I mentioned above) what fits one person won't necessarily fit another even if they have the same proportions, so the examples being given just indicate a range.
mikewsmith - Member
So in summary trying to size a bike by height alone is a bit ambitious.
Definitely. What would probably be easier would be to go into a shop, ride the bike for a bit on a turbo and perhaps a bit outside, and make use of the shop staff who do this day in/day out to make a recommendation.
Oh wait...
OP in not coming back to thread shocker?
