53-11_alltheway

Even though this is meaningless (considering the different seats and range of crank lengths that position the pedal spindle farther ahead in the 3 o' clock position). I'm just wondering how much set-back you use as measured from the BB center to the tip of the saddle?

I measured mine by dropping a plumb bob (set of keys attached to string) from the tip of the seat and marked the location on the chainstay. Then I used a ruler to measure from this point to the BB center.

Mine is 6cm.

krazyderek

mine is at 5.75cm
172.5 cranks,
27cm saddle
5'11 tall

53-11_alltheway

Yeah, list your crank length too.

Good idea.

cydewaze

I wish you had posted this before I sent my Trek back, because both my bikes are different, and I had just eyeballed it.

I'll measure my spare bike when I get home tonight. In fact, I'm going to take a lot of measurements from it and record them, because the cheap thing just fits me so well.

BikeWNC

I use 9.3 cm of setback.
177.5 mm crank length.
6'3" tall.
Fizik Aliante saddle.
7-8 cm saddle to bar drop.

53-11_alltheway

That's a good example of hip angle infleunced by handlebar position and set-back.

(No dount many of your drimensions are different so this is probably an apples to watermellons comparison) I'm 6'2" use a 180mm crank. 6cm of set-back, but have 17cm saddle to handlebar drop.

If I used more set-back I'd have to lower my seat which closes the hip angle. To compensate I'd raise my bars to open the hip angle up again. This is what I'd do for endurance rides (like a double century)

biker7

I have a relatively long femur and use 175mm cranks and my set back is about 9.2cm which is almost all the way back on saddle rail travel with a setback seat post with 72.5 deg seat tube and 77.5cm saddle height. I find this to be a comfortable versus falling forward position for long distance riding and can still deliver respectable power to the cranks.
George

BikeWNC

I primarily ride for longer distances. While speed and aerodynamics are important, comfort trumps both. At 47yo, I find certain parts are not as flexible as they once were. Though I am way more limber than the average joe my age.

berny

This dimension is irrelevant without knowing lots of others in particular the seat tube angle. This refers to the discussion we had recently about power output and distance behind the bb, in which it was suggested that moving the seat forward was an acceptable adjustment to make to correct the seat height for a variation in crank length.

BikeWNC

Pehaps I missed the other thread, but I don't see how STA is at all important to the question -How much set-back do you use? It is all relative to the BB.

As long as the seat is in a postion that works for you without being too far forward or back on the rails, and the TT is the proper length, what does it matter.

Since I have 9.3 cm of set-back, a STA of 72ish is OK. Should I use say 6 cm of set-back, then a steeper STA is more appropriate.

I could fit on a bike with either setup, but the HT length would have to be shorter on the bike with the steeper STA to maintain the same body angles.

53-11_alltheway

Exactly. You are right on the money.

I have two bikes with with saddles 6cm behind the BB. One has a steep seat tube angle and the seat is on a set-back post. The other has a slack seat tube angle and is forwardish on a straight clamp . Even though the relative positions look totally different they are in fact in the same fore/aft position.

It's all relative to the BB like you say.

Only relationship you need to understand is that set-back posts add top tube length and straight clamps don't.

climbo

it's all meaningless depending on the length and design of your saddle and where you sit on it when you ride, what crank length, what shoe size, cleat position on your shoe etc... but keep going....

cydewaze

5.8cm set back
172.5 cranks
5'10" tall
Selle Italia Flite saddle

53-11_alltheway

I've been talking lately about high forward seats opening the hip angle to allow lower handlebars lately, but you also need to understand taking this "forwardness" too far will worsen the knee angle (closes it). The only alternative at that point is open the knee angle up by pulling the torso forward on the frame via longer stem/top tube. etc.

So anybody messing with your fore/aft needs to take this into consideration. You'll have to have another stem handy if you really want to play around with this.

There are tradoffs with this kind of positioning as well. Namely, the center of gravity and out of the saddle climbing. Aerodynamics is the benefit though.

In an ideal world I'd have three bikes (flat ground bike, comprimise bike, out of the saddle climbing bike/comfort bike)

skinnyone

8 cm here..
172.5mm cranks
5'11"
10cm seat to handlebar drop...

baxtefer

hmmm sounds almost exactly like me.

9.3 cm setback
6'2"
175mm
Aliante
7.5 cm drop.

I think i need to slide my saddle ~0.5-0.75 forward. need to get a longer stem first.

berny

Yes I'm sorry, I posted on the run (leaving for work) and didn't think it through sufficiently. BB to seat is a crucial measurement and is independant of the STA as long as the measurement can be achieved with any given STA.