Another fitting dilemma

[MajorMantra]

Please bear with me, this is rather lengthy...

I'm on the verge of buying a new bike and have almost come to a decision but I'm having trouble determining the best frame size for me. The bike I've (almost) settled on is the Ribble Sportive Racing that everyone's been raving about lately. This is the geometry:

I'm having trouble choosing between the 49 and 52cm frames. From their height table I would definitely want the 52 as I'm 5'8.5", but what concerns me is the TT length. For comparison, these are 3 of the road bikes I've ridden a reasonable distance on over the past few months:

Genesis Flyer - 54.5cm TT - seems quite comfortable and offers a reasonably aggressive riding position

Cannondale CAAD5 R900Si - 56cm TT - a bit stretched, I have problems with my arms stiffening up after riding for a while. I tried switch to a shorter stem (90mm) but still felt stiff.

Old hi-ten lump - 58cm TT - quite comfortable. I think this is because the saddle and bars are roughly level, but I still find it odd that this works as well as it does. It makes me wonder if I'm misunderstanding my problems with the Cannondale - could it be something about the ride quality rather than the reach? Or is it the rather wide bars on the Cannondale causing the problem?

To complicate things even more, I tried the Competitive Cyclist fit calculator and these are the numbers it spat out:

Measurements
-------------------------------------------
Inseam: 81.2
Trunk: 64.25
Forearm: 33.0
Arm: 60.5
Thigh: 56.5
Lower Leg: 52.0
Sternal Notch: 142
Total Body Height: 174


The Competitive Fit (cm)
-------------------------------------------
Seat tube range c-c: 52.6 - 53.1
Seat tube range c-t: 54.2 - 54.7
Top tube length: 53.1 - 53.5
Stem Length: 10.7 - 11.3
BB-Saddle Position: 73.0 - 75.0
Saddle-Handlebar: 50.8 - 51.4
Saddle Setback: 4.1 - 4.5


The Eddy Fit (cm)
-------------------------------------------
Seat tube range c-c: 53.8 - 54.3
Seat tube range c-t: 55.4 - 55.9
Top tube length: 53.1 - 53.5
Stem Length: 9.6 - 10.2
BB-Saddle Position: 72.2 - 74.2
Saddle-Handlebar: 51.6 - 52.2
Saddle Setback: 5.3 - 5.7


The French Fit (cm)
-------------------------------------------
Seat tube range c-c: 55.5 - 56.0
Seat tube range c-t: 57.1 - 57.6
Top tube length: 54.3 - 54.7
Stem Length: 9.8 - 10.4
BB-Saddle Position: 70.5 - 72.5
Saddle-Handlebar: 53.3 - 53.9
Saddle Setback: 4.8 - 5.2

I don't know if I should take any notice of this, but it seems to think I ought to have a really small frame.

Can anyone offer an insight?

Matthew

 

[RedBike]

I'm of a simular height (5'9"). Having owned Ribbles I would advise you to ignore the seat tube lengths completely and go on the top tube lengths (Far right of that table).

Which would mean you'd want the 52cm Ribble. This isn't a small frame at all, most other manufatures would probably call this a 55cm bike.

 

[MajorMantra]

I'm of a simular height (5'9"). Having owned Ribbles I would advise you to ignore the seat tube lengths completely and go on the top tube lengths (Far right of that table).

Which would mean you'd want the 52cm Ribble. This isn't a small frame at all, most other manufatures would probably call this a 55cm bike.

I was actually worrying that the TT on the 52cm frame (that they call a "medium") might be too long, not too short, but my experience so far has been rather inconsistent. 55cm is only 5mm more TT than on my Flyer but I'm suffering the usual doubts of someone about to spend a grand on a bike.

Matthew

 

[spandex]

Going by the measurements of your self that you posted the 52 will be the best fit

 

[MajorMantra]

Thanks spandex, I'm leaning that way now.

(You know, this thread just proves to me that half the time, I just want people to reinforce decisions I've already made. Not that I wouldn't welcome more replies.)

Matthew

 

[bonj2]

On my bike i got a 52", despite the fact i'm 5'10"/5'11", so would normally get a 56", which is what my other bike is.
When it's in the stand it looks really diddy, i had to put the seatpost on to convince myself that it was big enough, but sure enough it is - it easily goes more than high enough, and I've got the same length stem as my other bike and it's stretched out just right - reach to the bars is fine. Just a different geometry.

I did as RedBike says, which is to go on toptube lengths. Even the 'L', 'XL', etc is more useful than seat tube length - i.e. both my bikes are 'L', but one is 56" and one is 52"...but they're both about 55cm top tube.

 

[MajorMantra]

I did as RedBike says, which is to go on toptube lengths. Even the 'L', 'XL', etc is more useful than seat tube length - i.e. both my bikes are 'L', but one is 56" and one is 52"...but they're both about 55cm top tube.

I am going on TT lengths, it's just I'm starting to wonder what TT length I actually need.

Matthew

 

[RedBike]

If the Genesis flyer is right (at 54.5 I assume?) and the Cannondale is right at 56cm then the Ribble at 55, just 0.5cm larger than the Flyer / 1cm shorter than the dale should be alright too.

You can easily compensate for a 1cm difference by changing the drop from the saddle to the bars as well as a shorter stem length.

The only way you will know for sure is to go and try one!

 

[jimboalee]

How did you measure your 'Inseam'?
Did you take 'Seated height' from 'Standing height'?

From your body dimensions, I would suggest the 49cm.
My calcs give 51.5 cm for a Horiz' toptube.

I get your 'Reach' at 630 mm, so its the 49cm size with a 10cm stem. Pretty well std average.

 

[bonj2]

I am going on TT lengths, it's just I'm starting to wonder what TT length I actually need.

Matthew

well, if you can answer the questions (a) what is the TT length of your current bike, and ( do you think your current bike is too big or too small, then that should help you to come up with an answer.

e.g. in my case, my current bike was the correct size, so its TT length was equal to the TT length that I need.

If you have more than one bike list the answers to those two questions for each bike.

That may sound easy, but you have got to answer ( literally - i.e. ONLY consider whether it is the right size - not whether it is a comfortable bike generally, whether you like the aggressive riding position, whether the saddle is the same height as the bars, what the ride quality is like, etc etc etc., because so many other different factors can influence those.
Without wanting to sound obvious, the only thing that can influence whether or not the bike is the right size for you or not is the size of the bike! if you know what I mean...
if you're trying to analyze things other than JUST whether the size is right, then you're only going to confuse yourself.
if you ask yourself 'is the bike right for me' instead of 'is the bike the right size for me', then you're not going to be able to deduce anything meaningful, because it could be the right size, but wrong for some other reason.

 

[MajorMantra]

If the Genesis flyer is right (at 54.5 I assume?) and the Cannondale is right at 56cm then the Ribble at 55, just 0.5cm larger than the Flyer / 1cm shorter than the dale should be alright too.

You can easily compensate for a 1cm difference by changing the drop from the saddle to the bars as well as a shorter stem length.

The only way you will know for sure is to go and try one!

Thing is, I can't decide if the Cannondale is right. It's ridable, but I have been having some comfort problems with it. I'd like to go try it, but if I want the Ribble that's not really an option.

How did you measure your 'Inseam'?
Did you take 'Seated height' from 'Standing height'?

From your body dimensions, I would suggest the 49cm.
My calcs give 51.5 cm for a Horiz' toptube.

I get your 'Reach' at 630 mm, so its the 49cm size with a 10cm stem. Pretty well std average.

I'm not sure I follow completely, the equivalent TT length of the 49cm frame is 52.9cm. It sounds like you're suggesting I need a 51.5cm TT which would mean the 44cm frame!

Inseam was measured per the instructions on Competitive Cyclist:

Inseam
Wear your cycling shorts, and take the measurements in bare feet.
Set your feet approximately 8" apart and straddle a straight edge - something like a square or a 2' level is ideal. Put as much pressure on your crotch as you feel when sitting on your bike seat. Measure the distance from the top of the level to the ground. Alternatively, mark the wall, then step away and take the measurement of the mark to the ground. And whatever you do, please don't use the inseam measurement from your Levi's! Pants inseams are at least 2" shorter than your actual inseam.

well, if you can answer the questions (a) what is the TT length of your current bike, and ( do you think your current bike is too big or too small, then that should help you to come up with an answer.

e.g. in my case, my current bike was the correct size, so its TT length was equal to the TT length that I need.

If you have more than one bike list the answers to those two questions for each bike.

That may sound easy, but you have got to answer ( literally - i.e. ONLY consider whether it is the right size - not whether it is a comfortable bike generally, whether you like the aggressive riding position, whether the saddle is the same height as the bars, what the ride quality is like, etc etc etc., because so many other different factors can influence those.
Without wanting to sound obvious, the only thing that can influence whether or not the bike is the right size for you or not is the size of the bike! if you know what I mean...
if you're trying to analyze things other than JUST whether the size is right, then you're only going to confuse yourself.
if you ask yourself 'is the bike right for me' instead of 'is the bike the right size for me', then you're not going to be able to deduce anything meaningful, because it could be the right size, but wrong for some other reason.

I take the point, but I'm still not sure. For one thing, I think my Flyer is the right size but since I've never actually been fitted to a bike, it's possible that another setup could be better.

If I assume for the sake of argument that the Flyer is the right size, then with 5mm more TT, the 52cm is closest. To go down to the smaller frame would mean losing 16mm of TT.

I'm hard to help, aren't I?

Cheers,
Matthew

 

[Radius]

I think you'll be fine with the larger size, and you can always get a shorter stem if it's too long. Sor'ed.

 

[MajorMantra]

I think you'll be fine with the larger size, and you can always get a shorter stem if it's too long. Sor'ed.

Can I blame you if it turns out to be too big?

Matthew

 

[RedBike]

Im roughly the same size and there's no way I could cope with the 49 with a 53cm top tube.

I would of been torn between the 52 and the larger 55, although I would of probably settled for the 52.

 

[Radius]

Can I blame you if it turns out to be too big?

Matthew

Yes. Yes you can.