Changing stems and estimating new saddle tip to bar "reach"
 

I am trying to figure out how to get more saddle tip-bar length and bar drop from a taller headtube bike currently set up with 30mm spacers under a -6dx100 stem.

Lets say I have my saddle at my desired height and setback.

Now I measure reach from the tip of the saddle to the center of the bar at the interface of the stem and face plate.

If I input the existing stem angle/length along with a new stem angle length into the stem calculator http://yojimg.net/bike/web_tools/stem.php
how close will the approximation of the new saddle tip to bar measure be if I add the existing (which I can measure) with the reach measure delta (27mm) determined by the stem calculator?

current stem 1 is a -6d x 100 with 30mm spacers under it.
proposed stem 2 would be -20d x 120 with 10mm spacers under it.
the bar drop delta would be about 4.4 cm between the two.

I realize the saddle tip to bar is a hypotenuse measure since there is bar drop and the stem calculator reach delta is parallel to the ground so strictly speaking they shouldn't be added together.

how much more than the 27mm spit out by the calculator will the new tip-saddle be? > 5mm? <5mm?

The bigger issue is why make such a large change all at once? Why not take 20mm of spacer from under the stem and put it on top, to start with. That will increase the reach by about 6mm and the drop about 19mm.

Better yet, just move 10mm at a time, for half the amount of change.

One problem with these changes is the potential need to make changes to the brake and shift cables. On my bike, I can't make much of a change without messing up the cables.

On my bike, the saddle tip to center of bars is 54cm, and the saddle to bar drop is 10cm. A horizontal measurement would be 53.85cm, which is only 1.5mm less.

Can't say without knowing what current saddle to bar measurement and what the saddle to bar drop are. Because you're trying to imagine in arc with radius located at the saddle tip.

But I will guess an increase of not more than 5 mm.

Dude needs to post a picture of the ride... 10 cm stem is fairly short... and since he wants to do do such a big change makes me wonder how the fit and the bike is set.

Sounds like he got a new bike with a taller head tube, and now he is working to get his fit right ?

.

Put the formula aside for a moment. Remember that changing one of the three contact points will affect the others. Think about your position on the bike a 3 points on a white paper; hands (bars), saddle and bottom bracket. How are you going to connect the dots? There are many ways each one using different stems, bars, seatposts, saddles, crank arm lengths and pedals. The best one for you is a decision based on your fitness, riding style, handling preferences, etc.
If you change your cockpit length you will be sitting on the saddle in a new position. Your saddle height and fore/aft should be looked as well as your saddle bar drop.
New bars with a longer reach and your current stem might also get you where you want to go. This will also change your saddle position.
Those formulas do not take into consideration your flexibility or range of motion. The combination that works well on paper might make you slower or even cause pain.
My suggestion would be to find an experienced, professional, bicycle fitter. The best results can not be achieved via a forum or photo exchange.

That’s a pretty big change. Since you have so many spacers under the current stem I would start moving those first before fitting a longer and lower stem.

Its not like pdmtong is new to bikes. Its a rather complex question that makes me think he knows what he is looking for so i will assume he has a reason for asking the way he did rather than looking for online bike fitting. Then again ive been wrong before .)

Sorry but i dont know the answer to your question either but i would guesstimate that its less than 5mm. Id guess around 2 or less just because the angle in change is still rather small in total when measured from the tip of the saddle.

you could try my ultra scientific methods,
fit a diff stem and bars and measure?:bike:

Seriously though, im not even sure what you are trying to do...
you want your bars lower and further away... sooooooo
1. longer stem, or longer reach bars are a must
2. lower stem on existing spacers
3. use lower angle stem

see where it gets you.

you ask for an estimate, but surely your own eyeballs can give you a better estimate of something in front of you than extrapolations from a bunch of yahoos on a bike forum?

what is the ultimate goal, its hard to help when im not sure what you are ultimately trying to do.

When setting up my bikes I usually pay more attention to where the hoods and drops end up as I spend much more time there than on the tops. Just mentioning that as a change in bars can extend or shorten reach and/or drop, so that may be another way for you to achieve some of the reach you want.

then disregard saddle to tip of bar entirely. your *ss is in the right place (and presumably feet/legs too), just need your hands in the right place now.

use this spreadsheet: http://gearinches.com/blog/misc/bike...try-comparator

it doesn't take into account where your actual saddle is, but you'll plug your two bike geometries in, as well as stem length/angles, and it tells where they'll end up.

Do like Dave says to start out. Take 10-20 MM of spacers out first. it will be lower and a tad longer, and feel like more than that longer. You will probably have to tip your saddle nose down a tiny tad to be prostate friendly as you go lower and longer. These changes will also change how your hands approach the hoods......there is some reach adjustment to be made there.

The stem chart don't lie.

Well, I "think" I know what I am doing but believe me, reading the forum keeps making me just a little more dangerous in my presumed knowledge. And it's always good to ask since everyone sees things differently.

Thanks everyone for your comments.

My saddle is 75.0 with 7.5cm setback
Saddle tip to bar is 56.0-57.0 at 7.5-8.0cm bar drop.

I am looking at a stock "endurance geo" cannondale synapse eTT 56.1 that is a little taller and a little shorter than my current set ups.

The frame would ship with the stem in the max height position which is 30mm spacers on top of a 25mm cone spacer.

With my saddle in the correct place and the bar maxed upwards as shipped, the saddle tip to bar is 53.5 and the bar drop is 2cm based on the -6dx100 stock stem.

That's why I want to take out spacers and use a
1) 110/120 stem to get my saddle tip to bar reach further by about 25mm to 56.0
and
2) -17d/-20d to increase my bar drop from 2cm to at least 6cm.

the frame angles are normal 73.0 HTA and 73.5 STA
None of the calculators let me estimate this bar reach measure but my guess is like tuscanyswe asserts. I could just add the linear measure to the reach diagonal and be close.

I'll probably order both a -20dx110 and a -20dx120 fizik stem from CC so I can meaure in person and easily return it.

thanks also for your comments about the cables Dave. It's nice to see you back posting as you had helped me a lot with my Campy questions when I first joined the forum.

my premise was if I take out 20mm of spacers and use a longer and steeper stem I can get closer to converting the existing stock set up to my preferred l position.

was asking if there was a way to calculate this before buying and trying and returning a few stems

all comments are appreciated ...

UPDATE:...I think I am going to swap the fabric scoop race shallow with an Arione CX (preferred), re-measure the existing bar drop, and see if I can get there by using a -7d x 110 (and eventually chopping the steerer) I think trying to retain the existing spacer stack for future resale is hampering my progress here.

STAY TUNED

Your 3pm post explained everything a lot better for me.. I would wait till you get the ride and test.because some frames likes the rider seated in another place sometimes. I know common sense tells you the same contact points but had a few frames already that did not like me seated in the correct places, for example my C50 likes me seated like 5 mm further back than any other bike. Other ones dont care...