Freddyonabike

Hey!

My seatpost has a setback, and I dont really know which part of the clamp i'm suppose to go by in terms of saddle fore/aft limit. The center of the seatpost clamp is obviously between the two bolts?
So I should use the blue line as reference regards to saddle fore/aft limit?

Thanks!

DaveSSS 

You should be able to push the saddle as far back as it can go, with just about any seatpost. If I really needed that much setback, I'd look for a different post. I use FSA K-Force posts with 32mm of setback.

aliasfox

I’d go by where it’s actually doing the clamping - ie blue line. If you use the yellow line as a marker, the back of the top plate will end up being a fulcrum around which the rail will bend (as you tighten the rear screw). Kind of a stupid design if you ask me.

If you have to put your seat so far forward, it may be worth asking your LBS to try a straight seatpost instead. I’ve always gotten my favorite fit on straight posts, but I also have relatively short legs for my height - 5’10”, and jeans with 30” inseams are sometimes too long for me.

cyclezen

Not sure what you're getting to, but the 'limit' is set by the combination of flat saddle rail available to clamp on to and how far fore or aft you can set based on the clamps...
certainly not used for any measurement . Although you can use a 'relative' measure from a current position on the rail to move the saddle some defined measure fore or aft from there.
A good reason for having that extra length on the lower rail support would be to give additional support for a saddle which is pushed all the way back, since most of the weight is carried on the rear part of the saddle. Saddles with Ti, CF and Mg rails would certainly benefit from as much support as possible, since they are more susceptible to rail bending or breaking, if the rear of the saddle rails is less supported.
Ride On
Yuri

Iride01 

Don't worry about the seat post itself. Just look to see how much of the saddle rails are in front of the clamp and how much is sticking out behind the clamp.

A good starting place is to have an equal amount of rail sticking out either side of the clamp. Then you can adjust fore/aft as needed after that. The closer you get to one end of the rails, the more stress that will be put on one side instead of the load being shared. So depending on your weight and how hard a bump you hit, the rails might be more likely to break when at or near their limit of all the way back or forward.

So if you find you have to have the saddle all the way forward or aft in the clamp, then you might should consider a seat post with a different set back amount.

Freddyonabike

My Selle Italia SLR superflow saddle has outer limits. Its marked on the rails with marks like this "< >". So say I want to push the saddle all the way to the front, should the saddle rail's "<>" mark be at the blue or yellow line(view pic above)??

Thanks guys! Sry for my bad english :/ Hope this last post makes more sense

cyclezen

Images online of the saddle are not great in showing the rail marks, there seems a section marked with mm measures... and the the outer limit marks (which seem to designate the extreme ends of the possible flat rail section).
Having some experience with Sella Italia Flite Ti, I would respect the Saddle manufacturer's marks. If you're a heavier rider, say above 75-78 kg, I would keep the last mm scale mark on saddle rail even with or behind the yellow line/rear edge of lower clamp/support. If a much lighter rider, I would be OK with wandering a few mm past the end of the scale.
In any case, certainly keeping the rear mark behind the yellow line.
...I've seen the results of a sizable, shorter rider, who pushed their Flite Ti forward as far as it would go...
Your english is good
Ride On
Yuri

Sy Reene

I understand the question as to whether in his instance the top or bottom of his clamp can go to the "Stop" line on the saddle rail. Eg. pic below. I'd definitely at least my case assume it's the bottom clamp surface as shown.

Recycled Cycler

That "STOP" is pretty self-evident. It's where the rail starts to curve. Even without the stop line, it'd be hard to go any farther. If it were me and without a stop line I'd have to stop at same place on bottom clamp it won't go past that curve.

Sy Reene

Well I imagine I could slide the saddle further back until the top of the clamp hits the curve and Stop line (while the bottom clamp would lose contact in that ~1cm length), which I think was the question. But that seems like a bad idea :-)