Hi folks,

 

I am tageting on a 2010 S1 frame. However I still cannot decide which size to buy. Here is my fitting information. My body height is 172cm, arm is 66cm, and my inseam is 79cm. Please give me some suggestions? Shold I buy 48 cm or 51 cm frame. Thanks.

 

-tony

I wouldn't listen to what anyone tells you online on this subject. It is so 'subjective'. Go get yourself professionally fit and then ride that size to see what you think. It's beyond a personal preference depending on riding style, your build, etc. You're basically writing to an online forum and doing the equivalent of asking what size shoe should you wear. Try it on. Best of luck.

48 is almost certainly way too small for you. You are most likely between 51 and 54.

But a bike fit, as mentioned above, is the best way forwards.

 Get a professional fit!

Here are some related discussions.

http://forums.cervelo.com/forums/p/3038/19340.aspx#19340

http://forums.cervelo.com/forums/p/3023/19089.aspx#19089

http://forums.cervelo.com/forums/t/2846.aspx

Only you can determine the correct size for you as there are too many factors to take into account including personal preferences and experience. To make the decision, you can: test ride the different sizes; get a fitting; and, compare the geometry of the bike that you currently ride with the Cervelo geometry, particularly the measurements of stack and reach.

I'm almost exactly your size, 5"8 with a 30 inch seam and ride a 51cm frame with a 110mm stem for my S1.  With a 48cm frame you'd probably be way to cramped. 

But just as the other posters suggest, try a couple sizes at a bike shop where they know how to fit riders and see what feels best.

Thanks to all of your suggestions. I did a professional fitting last night. The data indicates that I should take a 49~50 size. My flexibility is not very good (my finger cannot touch ground when stoop.) Therefore I will take a 51cm one.

 

-tony

Good for you! Flexibility can be improved over time. It is not a constant. Riding my Cervelo motivates me to undertake other efforts that enhance fitness and health.

Cheers to all that got back to me which no one ever did. I too was seeking for help with sizing and posed a lengthy detailed measurement on another thread (not his one) and guess what -- not a soul gave me any insight, 2 cents, help or advice, not even a sausage!  Except for top man Jasann who did point me in the right direction. 

Yes, I am fully aware of the need to get a professional bike fit, however, I was interested in hearing from you guyz who are on 54s ad 51s just so that I can compare myself. Granted that even riders of the same height and inseam have different torso and leg lengths and flexibility, perhaps my expectations were high. Oh well never mind.

So anyway in the end, I did manage rule out the 54cm completely after a second test ride on the 54cm (fitted with a whopping 120mm stem). After getting good feedback from few S1 riders on 54's and 51's, the 51 would be perfect for me. It also turned out that my LBS was "pushing" me hard to get a 54cm even when he sized me up and saw me stretched out on the hoods and drops and despite this, the LBS tried very hard convincing me the 54 was best for 170cm tall rider with 30.5 inches inseam with very good flexibility. My gut feel was to run like hell and be patient until I find the 51cm no matter how tempting the sale price!

 

The Rock:

Cheers to all that got back to me which no one ever did ... Yes, I am fully aware of the need to get a professional bike fit, however, I was interested in hearing from you guyz who are on 54s ad 51s just so that I can compare myself. Granted that even riders of the same height and inseam have different torso and leg lengths and flexibility, perhaps my expectations were high ... So anyway in the end, I did manage rule out the 54cm completely after a second test ride on the 54cm (fitted with a whopping 120mm stem). After getting good feedback from few S1 riders on 54's and 51's, the 51 would be perfect for me. It also turned out that my LBS was "pushing" me hard to get a 54cm even when he sized me up and saw me stretched out on the hoods and drops and despite this, the LBS tried very hard convincing me the 54 was best for 170cm tall rider with 30.5 inches inseam with very good flexibility. My gut feel was to run like hell and be patient until I find the 51cm no matter how tempting the sale price!

By your admission, it seems that you know better than to rely on sizing your bike based on someone else's reference to their specific size.  (Yet, you still wanted to make that comparison!) 

I don't recall your post. While I have responded to some of the posts that involve size 48  vs. size 51 whose sizes are of particular interest to me, I find that the requests occur too frequently.  Moreover, the responses to these type of posts become a popularity contest of who rides which size. It is meaningless data other than to the manufacturer or to the seller of the product. Consequently, I am trying to ween myself from responding to such enquiries.

You seem to have your sizing issue figured out; and, I agree that you should "run like hell" from your LBS. When I bought my Cervelo RS in February, having confidence in the advice and guidance that the LBS would provide me, was a key factor in my choice as to where I would make my purchase. Consequently, I went further afield to make my purchase to a location where I had previous and satisfactory experiences.

The Rock:

not a soul gave me ... a sausage!  Except for top man Jasann ...

Don't mention me on top and sausage - even if it was 2 different sentences;-) Don't want people getting the wrong idea. Top shelf, The Rock, top shelf.

 

lol!!! ooops wasn8t intentional Jasann,,, just got my words twisted :)

It just dawned on me that Cervelo's top tube measurement on the S1 is an "effective" top tube length i.e. NOT the "actual" (as one would physically measure along the actual length of the top tube). The "effective" length on a sloping top tube is always going to be slightly longer than the "actual" length by about 10mm-15mm (guesstimate).

Reason for revisting S1 geometry against the CAAD9 simply because I know the 52cm CAAD9 fitted me perfectly whereas the 54cm CAAD9 felt overstretched even with standard 100mm stem.

 

Which S1 frame best matches the 52cm CAAD9?

Comparing REACH, 54cm matches best (380 vs 382).

!!!Note: difference in REACH between 52cm and 54cm CAAD9 is smaller (only 1cm) vs 10cm difference between 51cm and 54cm S1.

Comparing Stacks, 51cm matches best (522 vs 529)

Comparing Head Tubes, 51cm matches best (120 vs 120)

Comparing "actual" Top-Tubes, 54cm matches best (535 vs 535) 

 

Now the dilemma being it's not clearcut.

• 54cm S1 trumps based on REACH and "actual" Top-Tube. !!!Caveat: 54cm S1 felt overstretched during two long test-rides. Was that because of the 120mm stem or something else? Didn8t get chance to switch stem down to 100mm. Could 20mm made a significant difference?
  
  
• 51cm S1 trumps  based on STACK and Head-Tube.
  

 

???Based on REACH, Stack, Head-tube, "actual" (not "effective") Top-Tube; which of these four criteria should be used in what order of priority to select the optimum frame size??? knowing that one could tweak and adjust stem length, saddle height and set-back after the correct frame size is determined.

Conclusion:
Given that Cervelo focus on REACH based geometry where top-tube (actual or effective) probably does not play a vital role, 51cm S1 looks 2B the "safer" choice as there's more room to play with stem length, saddle height, setback etc. to get the best optimum fit. Infact, the REACH on the 51 would be even better with less chance of being over stretched.

73 Degree Seattube Angle (rear facing seatpost position)
Size	Wheel Size	Head Tube Angle	BB Drop	Top Tube	Head Tube Length	Front Center	Rear Center	Stand Over Height	Stack	Reach
48	700c	72.5°	68	515	100	547	399	709	502	361
51	700c	73°	68	530	120	558	399	729	522	370
54	700c	73°	68	545	140	573	399	746	541	380
56	700c	73°	68	565	160	593	399	764	560	394
58	700c	73°	68	580	180	608	399	781	580	403
61	700c	73°	68	592	200	620	399	800	599	409

 

To all the technical guru's out there, does this seem quite reasonable assumption and correlation to make or am I completely off the rails?

Actual fittings are better than calculations.

With that in mind, I thought you'd already had a fitting done?

In fact, since then, *some people* may have noted your preferred option of a 51.

The Rock:

am I completely off the rails?

By Jove, he's finally got it! :-)

* When I say "some people", I mean "every freaking member of every freaking cycling forum in the whole freaking world".

Stem length differences have a bigger impact on fit than handling. My team bike is a CAAD9 size 52. My R3sl is a 51, the CAAD9 has a stem 20mm longer for the same fit. I think you're on the right track.