boshk

Went to a Specialized Concept shop today in UK and totally like the Diverge and new Roubaix (beautifully finished bike but out of budget)

Anyway, like the DSW but they only have a size 54 in stock, no 52 in stock.

Not sure whether it was the sales in him, but sales guy was really information and said I'm a 54, explained why while I was on the bike but said if I go for other brands like Cannondale or BMC, do NOT get a 54, its too big.

I did go to another shop after and tried their Cannondale synapse 54....way too big, arms stretched out, BMC gf02 51cm...felt good, slight bend in arms.

I'm 5'7", inseam about 30"

I've been comparing geometry of Synapse 54 (S) vs Diverge 54 (D) and number wise....the 54 Diverge should be uncomfortable.

Reach= 376mm (S) vs 380mm (D)
Stack= 576 (S) vs 565 (D)
Top Tube length= 542 (S) vs 547 (D)

Geometry from a Diverge 52 vs 54 are
Reach= 378 vs 380
Stack= 544 vs 565
Top Tube= 534 vs 547
If I go back down to 52, can a reduction in stack of 21mm and 13mm of top tube length make it 'too small'?

Opinions welcome

I know safest bet is ask or search to see if there are any 52s around for me to try but pressed for time before I leave.

dvdslw

I'm much taller than you so my opinion may not matter but I have always found Specialized road bikes to run big compared to just about everyone else out there. I ride a 60cm Cannondale but would never consider anything above a 58 with Specialized. It's strange you are finding the exact opposite result. Anyway, I wouldn't rush it and be certain you're getting the right sized bike for you. Nothing worse than second guessing yourself every time you ride your new bike.

vinuneuro

According to the Specialize size guide for the Diverge, 5'7 puts you on 52 or 54 assuming you have normal proportions. Fwiw, at 5'11 with long legs and arms, the size guide puts me on 56 or 58. When I rode 56 and 58 back to back, the 58 was clearly too big and the 56 fit perfectly. If one were to extrapolate based on that the 52 might be the one for you. BUT I would highly encourage you to find a 52 to ride. It will be obvious which one is the correct size when you ride them. In such an active cycling country as the UK you shouldn't trouble finding 52 to test ride, the Diverge is popular model.

https://www.hargrovescycles.co.uk/med...guide-road.JPG

mcours2006

When in doubt (or in between sizes) go for the one slightly smaller rather than the one slightly bigger.

rpenmanparker 

I don't understand the question. You are test riding bikes. Forgetting about the bike you don't have to test for a minute, what about the ones you have tested or at least have available to test? Does the 54 cm Specialized fit or not? If it fits, it is right. Regarding other brands, same thing. You are in a hurry and must buy from current stock, so just do it. Find one that fits you, and buy it. Talking about how a size that is not available WOULD fit makes no sense.

Are you saying there are no 52s in any brand/model or just not in the Specialized?

Nothing is more important than fit.

BTW, I am 5'7" with a little more leg (31.5" inseam) and have always ridden 54s. With the saddles all the way back on setback seat posts and at least a 100 mm stem. I only tell you this to demonstrate that you cannot judge from what folks tell you. It will only confuse you. You have the ultimate ability to know the truth by test riding. Don't let what folks say or what the numbers say confuse you.

badger1

For all practical purposes the reach on the 52 and 54 Diverge is the same, if you take into account the .5 degree steeper seat angle on the 52.

So at 5'7" which you prefer will come down to the difference in stack -- which affects effective reach through saddle-to-bar drop; you'll only know by riding both.

I'm 5'8" but with long legs/short torso (33" true cycling inseam); I 'can' ride either a 52 or 54 Specialized Roubaix, according to charts, but 54 fits me much better. I only l found that out by trying both.

rpenmanparker 

Seat tube angle doesn't affect reach (either frame reach or actual finished bike reach) for two reasons. Frame reach is defined related to the bottom bracket, so seat tube angle doesn't matter. As regards your reach from the saddle to the bars on a finished bike, the saddle position is also only determined relative to the bottom bracket. Your saddle on any same-purpose road bike should be in exactly the same place relative to the bottom bracket whether you need a special seatpost or whatever to achieve that. Neither seat tube angle nor saddle height relative to the top tube make any difference. Only saddle position and bar position relative to the bottom bracket.

badger1

I stand corrected. Nevertheless, still seems to me that for all practical purposes the frame reach, as typically measured, on a 52 (378mm) and 54 (380mm) Diverge DSW is the same; that was my main point. Perhaps I am wrong about that?

rpenmanparker 

Sure, if the numbers are that close, then they are practically the same. I'm just pointing out that seat tube angle isn't a factor. Now if you are just looking at top tube length, STA does make a difference in finished frame reach from saddle to bars. Because you need to correct for STA when placing the saddle, you should keep that in mind when comparing top tubes. A 1° steeper or slacker STA means you should think of the top tube as 1 cm longer or shorter when comparing two frames. I use 73° as my standard for STA. So if the STA is steeper I mentally lengthen the top tube. If the STA is slacker, I mentally shorten the top tube for comparison to the other frame.

vinuneuro

I asked about stack/reach vs. frame size when shopping last year for a 56 vs. 58 Diverge. That thread produced some great insight. And in the end even though the 58 only had 4mm farther reach but 32mm higher stack height, it felt much more stretched out when I rode them back to back. There's more to it than just going back stack/reach alone.

https://www.bikeforums.net/road-cycli...ame-sizes.html

berner

I to am 5'' 7" with a 30.75" inseam and ride a Specialized Secteur a nominal size 54mm (effective top tube of 54mm). The bike fits well.

boshk

No, I'm not technically test riding, more 'test sitting' on the bike.

I test sat on a 54 Diverge, 51 BMC GF02 and 54 Synapse, and out of the 3, BMC was the best feel.

I managed to track down a 52 Diverge but its another store in UK which is about an hour out, so I'll go try that.

Guess the questions were, how come geometries can differ so much when it felt ok on a 54 Diverge but on a 54 Synapse, I felt stretched out and can a few mm in reach and stack affect the fit so much.

Anyway, the replies answered most of the questions I think

99Klein 

Geometry may be the same, but stem height, angle and length will make a huge difference.

rpenmanparker 

I don't get test sitting. Is the weather too bad for a ride?

Bike fit and frame geometry/measurements are two very different things. Finished bike setup is as important as frame geometry. You don't say how much adjustment was made to fit the bikes to you: saddle position, bar width, crank arm length, stem length and angle, spacer stack height. Heck, even the twist of the bars and height and angle of the levers matter. Reach to the hoods can vary by a few cm depending upon how the levers are placed on the bars. You could have been comparing several completely different size bikes in terms of how they were set up. You make it sound like you are serious about comparing bicycles rigorously, but that is not the message that is written between the lines.

garysol1 

If you dont want to or can't ride the bikes at least ask the shops to throw them up on a trainer for you. We do it all the time.

boshk

great idea.....if they will do it.

boshk

well, it was 2C and raining, so all I did was sit on the bike with zero adjustment for me, even to saddle.
The measurements you stated above, I don't know, whatever comes as standard on a Diverge DSW.
Bar width-no idea, but this is the handlebar, Specialized, shallow drop, alloy, 125mm drop, 70mm short-reach
crank arm length-no idea, Tiagra compact 50/34
stem length-no idea, Specialized 3D forged alloy, 4-bolt, 6-degree rise
stem angle-6 deg down
Spacers-20mm?....Headset 1-1/8", integrated sealed Cr-Mo cartridge bearings, 20mm alloy cone spacer, w/ 20mm spacers

Guess I didn't have my cash out to show my intention, anyway, I'll be going to a shop tomorrow that has a 52 and 54 Diverge so as Garysol1 have suggested, I'll show my cash and ask for the both bike sizes to be put on a trainer.

San Pedro

The crank arm on the 52 is probably 170mm vs 175 on the 54. FWIW, I am 5'8" and I ride 52cm Allez and a size small TCR, but I need long stems on both bikes.

rpenmanparker 

boshk, here is the thing. When you compare the two size bikes, you should be comparing them as set up with the identical contact points. In other words in both cases the saddle should be exactly where you need it to be relative to the bottom bracket only, both height and set back. The reach and drop to the bars should be exactly the same. In fact you shouldn't be able to tell the difference between the two bikes when you are in riding position on them. For two bikes only one 2 cm size different, that shouldn't be hard to do. If it can't be done on one of the bikes, then that disqualifies that bike. But if it can and barring the ability to ride the bike outdoors, you have to make the decision about which one is right for you when you get off an look at the bike. Which one has the more extreme setup? Too long a stem, saddle pushed all the way back, 40 cm of spacers and so on. Pick the bike that can be fit to you in the middle of the adjustability range, not at either extreme.

garysol1 

FYI.....crank arms are 170 for the 52 and 172.5 for the 54 for the DSW. Interestingly the cheaper A1 uses 170 for both sizes.

garysol1 

I mean this seriously. If the shop in question won't take the time to simply put a couple of bikes on the trainer for you then move on to a different shop. You want a shop who is willing to spend the time with you to help you find the right bike and the right fit.

Chaltierx

I have the same height and inseam as you. I'm also looking to buy a Specialized but I'm getting the Allez. I tried the 54 but I felt a bit stretched out on the hoods and I kept sliding forward on the saddle. I haven't tried the 52 yet but I will soon. Based on my research though, I think the 52 would work better for me.

boshk

52 is way better.