Originally Posted by Dave (Post 2681649)

The Cannondale geometry chart is helpful, but the combination of headset top cap and spacers, plus your stem angle would be valuable too. Most standard headset tops are 15mm these days, but adding 20mm of spacer would increase that to 35mm.

A standard Chris King headset has a stack of 28mm, to add to the head tube length listed in the geometry chart, but up to 20mm of spacers can be added without looking too dorky.

The 58cm traditional frame comes the closest to your 56cm C'dale. The top tube is 4mm longer, but the seat tube angle is .5 degree less, which means that the saddle would be a little further forward to place the saddle in the same position relative to the BB and offset the longer top tube. The minimum head tube length,with the headset would be about 179mm.

The problem with this size may be the standover height being too tall.

The shorter reach on the 56cm would require a 110mm stem since the steeper STA requires the saddle to be moved a 5-6mm further back on the post, but the head tube is 15mm shorter. Adding more spacers reduces the reach.

Back in the days when Colnago geometry was developed, the concept of frame reach was not in play and you often see very little difference in reach between two sizes, since the increase in TT length was at least partially cancelled out by decrease in the STA, as the sizes get larger.

https://www.colnago.com/wp-content/u...RADITIONAL.pdf

Here's a picture of my first C-40, a 55cm, probably from 2002. Back then I made the mistake of buying frames that fit my leg length better than my torso length, but I always used a setback seat post and a 110mm stem. Back then nearly all bars and the common ramp down angle that place the brake hoods lower than the top of the bars. These days, most bars place the brake hoods higher.

https://forums.thepaceline.net/pictu...&pictureid=572

At the same time, I had just built up a new 54cm C-40 and planned to sell the first one.

https://forums.thepaceline.net/pictu...&pictureid=573

Today, I ride what would be the equivalent of a 52cm traditional frame, but it's called a 48cm, based on the seat tube length. I use a lot more drop, but I could easily raise the bars by 2cm with a -6 stem instead of a -17.

https://forums.thepaceline.net/pictu...&pictureid=469

Originally Posted by colker (Post 2681667)

What is your center of bb to saddle height Dave? 70.5cm?

Originally Posted by Dave (Post 2681725)

73cm

Originally Posted by Dave (Post 2681649)

A standard Chris King headset has a stack of 28mm, to add to the head tube length listed in the geometry chart, but up to 20mm of spacers can be added without looking too dorky.

Originally Posted by Herder (Post 2682322)

Forgot to ask what's the tire clearance on these?

Just in case I change my mind or decide to go with a 58 size

Originally Posted by Herder (Post 2682133)

Yeah I think if I go with the 56 I'll need 4 cm extra after the headset. Probably would look to dorky. Even with a top cap of 15mm I would need an extra 25mm.

I'm using a - 6 ste. I could go with 0 stem but don't love the look of thay either

Thanks for everyone's help

Originally Posted by sleepyfelix (Post 2685909)

I'm 5' 11' and I've had a few different Masters - three with a threaded stem and one with a threadless fork and modern stem. Three were 57cm and they always felt a bit low at the front and a 59cm that felt about right. If you are used to modern compact/upright geo then the short headtube of a master will seem quite aggressive.

For reference I'm generally fitting a 58cm cannondale, a 56s modern Colnago or a 57 Ritchey if that helps. I'm not overly flexible so you might be able to cope with a lower front end than me.

Originally Posted by mass_biker (Post 2680306)

I have both. 5'11" here.

The 58 (Colnago Sized) master X light I've owned - well, forever - fits me like a 56 "square" (even thought the effective TT is something like 56.3)...within spitting distance of my 56 CAAD (which is truly a 56 TT).

m_b

Originally Posted by pfr (Post 2680611)

I have a 57 Colnago C50, which I believe has similar geo. I use a 110 stem. I'm 6' 1/2 ". Fits great. My son has a 56 Caad12 and that's the size I would use as well. All my other bikes are M and/or 56ish. Hope this helps.