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Discussion Starter · #1 ·
Back story:

Im 6'1 very flexable but have injured my back and am now in recovery mode.

I have been racing mountain bikes for 10 years and currently ride a 21" S-Works SJ 29er that fits amazing.

I plan to use the bike for training not racing. But thought I would drop the stem all the way down on the Roubaix.

Current setup:
Axle to seat measurement is 38.5" or 97.79cm and seat nose to center of stem is 25" or 63.5cm

I've ridden what bikes I can find tarmac and roubaix from last year.

So 58 or 61?
 

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sixteenstone96 said:
Axle to seat measurement is 38.5" or 97.79cm and seat nose to center of stem is 25" or 63.5cm
Is this pedal axle to top of saddle (presumably with crank down and parallel to seat tube)? A more usual measurement would be bottom bracket (center) to top of saddle. It's easy to convert by subtracting the crank length, eg. 175mm. More importantly, how much vertical drop from saddle top to handlebar center are you aiming for?

sixteenstone96 said:
So 58 or 61?
The 61 Roubaix is a huge bike with a very long head tube. The reason to buy the 61 would be to get the handlebars up high to minimize drop, and maybe that's what you want because of your back issue. The downside is that the top tube is also longer, and you may well end up with a reach problem requiring a short stem. Also the wheel base is getting pretty long which adds stability but affects handling (in my experience anyway).

What did the LBS say?
 

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Discussion Starter · #3 ·
yes pedal axle to seat top measurement, i've always hated the bb to seat measurement because the last road bike I had (colnago c-40 61cm) it came with 177.5 cranks throwing off that measurement.

LBS = i look / feel huge on the 58 meaning it felt small and the 61cm felt a touch big but i had street clothes on, so it could be ok.
 

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First impressions are often a good guide. But, yeah, you need to judge it from a test ride with cycling shorts and shoes on. You could also spend some time going back and forth between the 2 in the store on a trainer.

For me, at 6'5", I could have gone either way between a 58 and 61 Tarmac. In fact, I went with the 58 because I was more concerned about bringing in the reach (ie. wanting smaller top tube) and not about reducing the drop (ie. not wanting taller head tube). The trade-off was a lot of exposed seat-post.
 

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I think UK's right on. You can see on the pic the head tube is much larger than the pic on the website.

I'm about 6'3", and I went with the 61" after trying a 58 and feeling cramped, especially on the lower handlebars. However, on the 61, the reach was an issue, and I changed to a 100mm stem from the 110 it came with. After riding for 150 miles or so, I slid the seat up a little and now it seems pretty good. With all that I do wonder if the 58 might have been better after all.

It's possible some of the issue for me was that coming from a mountain bike it took a while to get used to the drop even on an "endurance" bike. You mentioned that you would probably set the stem up in the lowest position - do you know if you'll like that on a long ride? The stem set-up is easier to adjust once you've bought the bike than is trading for a shorter stem.

UK, at 6'5" on a 58 you really must have a huge amount of post!
 

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UK, at 6'5" on a 58 you really must have a huge amount of post![/QUOTE

Yup, I'm within a couple of cm of the limit line but it works for me:

 

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Without seeing you, we're only guessing on size requirements. How a rider is proportioned, their flexibility/ anatomy and preferences/ cycling history play more of a roll in this than just knowing one's height.

You need a fitting in cycling attire, and if I were doing it I'd begin by putting the 58cm on a trainer, 'ball park' saddle height and have you ride. To start, the saddle would already be leveled, so once we determined exact height and fore/ aft (KOPS+/-), I'd concentrate on reach and drop. Being an initial fit, I wouldn't recommend a rider 'drop the stem all the way down'. Rather, my goal would be to get you in what I saw as your range for reach/ drop requirements.

At this point it, based on the final adjustments, we'd have a good idea if the 58 was going to work well for you. If so, you'd be sent out on a test ride - out on the roads, and for some duration. Then you return and we'd tweak fit from there.

Just a guess, but I'd be surprised if the 58 didn't work for you, but during the fitting on the 58, that would become evident to an experienced fitter. You may end up with a fairly long stem, but if the overall fit is right for you, the saddle rails will end up mid to slightly rearward, so f/r weight distribution will be in a good range, and this is generally a good indicator in determining the correct frame size for a rider.
 
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