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Hey guys,
I'm considering upgrading to a cervelo soloist, and would like some advice on their frame sizing. I currently ride a specialized allez in a size 54, im 5'8" with a 81cm inseam. The confusion is, due to my relatively short femurs I've been having an extremely hard time getting to kops, and i've since resorted to using a zero setback seatpost with the seat slid fairly far forward. So, now for my question, would a smaller sized frame allow for a more orthodox position/weight distribution? Would I fit a 51cm cervelo, or should I stick to a 54? I would of course ride one in person, but the cervelo dealers a few and far, and the few dealers in my area have NO models in stock.
Thanks
 

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more detail...

It would help if you posted your saddle height, the stem angle, stem length and total head tube stack height (with the headset and spacers). Many riders of your height would chose the next size smaller frame. I'm 1.5 inches shorter, with a longer 83cm inseam and 72cm saddle height. I'd chose one size smaller, with my short torso.

The 54cm Cervelo should have a slightly shorter reach since it's advertsied as having a 73 degree STA with a 54.5cm TT. The downside is that this will require the saddle to be moved about 5mm further forward on the post. This can be a problem, becasue the Soloist uses a special aerodynamic post. This post has set back or set forward positions, but no straight up position. The forward position is apparently 3cm more forward. This might work, but the saddle might then be pushed all the way back, making for a goofy looking setup.

The rest of the fit should be about the same, since the 54cm Cervelo has the same HT length.

As for the smaller frame, it will have a 1.5cm shorter TT and a 2cm shorter head tube. Frame size has nothing to do with KOP and the type of seatpost required. That's determined by the STA.
 

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im 5'7 and i rode a 54(which is now on the classified section) there was plebty of saddle to hb drop and was an agressive setup. I also tried the 51, i only got 2-3 cm more of drop and my saddle was pushed all the way back.
 

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well...

This info doesn't mean much. No saddle height, bar to saddle drop, stem angle or spacer info.

I've rarely found anyone of my height with a longer inseam. With a 140mm head tube, I'd use no spacers and only an 80 degree stem to get my 9cm saddle to bar height difference.

I'll repeat the frame size has no bearing on saddle position. It's the STA that determines that. In some brands, it is common for the next size smaller frame to have a .5-1.0 degree steeper STA. That would require the saddle to be moved back in the range of .5-1.2cm.
 

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about KOP...

I'll also add that it's not wise to get obsessed with KOP. Try the Andy Pruitt method os using the front of the knee and the front of the crankarm rather than the boney protrusion below the kneecap and the pedal spindle. You may find different results. Pushing the saddle too far forward will foul up the bike's weight balance and put too much weight on your hands. Moving the saddle back will recruit more use from the hamstrings and glutes. Having the knee 1-2cm behind KOP may work just fine.
 

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C-40 said:
Try the Andy Pruitt method os using the front of the knee and the front of the crankarm rather than the boney protrusion below the kneecap and the pedal spindle.
This is the first I've heard of this method, but I don't see how using the front of the crankarm can give a consistent position. The pedal axle spindle makes some sense as a reference point since it's a point of contact between the rider and the bike, but how far the crankarm extends from this depends on the design. If I glue a 10 mm piece of plastic to the front of my crankarm without moving the pedal, why should I move my saddle forward 10 mm? At one point FSA used a single crankarm length and just drilled the pedal hole in different positions for their different sizes so the distance form the pedal to the front of the crankarm differed by 1 cm between their 165 and 175 cranks.
 

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true...

I'm just quoting the technique recommend by Andy Pruitt, who has fitted many pro riders. It's been around a long time. Of course there could easily be as much as a 1cm difference in the distance from the pedal spindle to the front of the crank. Not too many years ago when all cranks had forged aluminum crankarms, this was probably not the case. You might need some common sense to spot an oddball crank.

I've always found it really tough to eyeball the pedal spindle centerlin while sitting on the bike with a plumb bob pointing at the top of my shoe.

FWIW, the Pruitt method showed me to be forward a bit with my last season's position, so when I built up a new bike recently I moved the saddle back close to 1cm. I've experimented with positions a lot further back than that with no problem.
 
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