Chitown_Mike

Got into a conversation with a coworker who also bikes and got to talking about the position of the seat clamp. I stated that I have seen the clamp both fore and aft of the seatpost, he said it should only be aft otherwise it will cause the seat to nose down.

My question is can the position of the clamp nuts be in front of the seat post or has to be behind it? And either way, why?

pursuance

Either way.

But... To the front if rain/mud spray gets on the seat post as to the front blocks some of the wet from getting into the post/tube area causing possible corrosion resulting in a frozen post.

In the olden days a bit of tube was installed on the post, then drawn over the clamp to prevent moisture, to include sweat, from getting in there.

HillRider

I assume you are referring to the clamp the saddle rails fit into. Most seat posts have what is known as "setback", that is the clamp is off-set behind the center of the post. When saddle is installed, the setback allows the saddle to be positioned far enough back to suit the rider. There are some seatposts designed with no setback and the saddle clamp is centered directly above the post. Rider leg length, frame design, etc, determines if you need a setback seatpost or not

For most seatposts, the saddle clamp had limited tilt capability and positioning the "setback" forward won't let you level the saddle. Some have a wide enough range that you can level the saddle even with the seatpost rotated 180° from it's correct position but most don't.

So, your friend is correct most of the time. If you install the seatpost with the setback pointed the wrong way, you won't be able to set the saddle angle properly.

fietsbob

Some Bikes Like Brompton, A folding bike, made in only 1 size Use the saddle clip as part of the bike fit.
near/far reach.. the setback from the BB-axis changes too .. effectively a seat post angle, steeper or shallower
depending on which side of the seatpost the saddle clip is fitted.

Some seat posts which have been designed to be set back, the integrated rail clip design,
dont have the angle range of adjustment to be in front,

other seatposts, specially made for Triathletes needs, are not designed to be rear set.

Zero setback seat-posts are neither.. clamp mech is directly on top.

Chitown_Mike

Perfect info! Looks like we were both right, I have my clamp with the nuts in front of my seatpost and I have a full 360* serrations on my clamp which is probably why I didn't have a problem.

Much appreciated to the geniuses that run in this part of the forum!

sreten

Hi,

If your talking the very standard seat clamp then
the position of the nuts fore or aft affects the
range of fore or aft of the seat position a lot.

The standard position is bolts to the rear and the
middle of the rails, bolts to the front is much
further forward, could work for some I guess.

I always use the standard seat clamp upsidedown
with the bolts always to the rear, as ever, YMMV.
(It looks the best by far.)

rgds,sreten.

ksisler

P; In almost 40 years, I haven't seen that trick but it looks highly usefull. One more add to the tricks log book. Thanks! /K

Continuity

And/or you can put an O-ring or rubber washer where the seat tube meets the frame.

If you put say a bit of old inner tube as a 'sleeve' over the clamp area, I would think that it would be best to check that it's not actually *holding* any moisture there occasionally, especially after riding in the rain/snow.

I read about how someone got an old frame where someone had placed a wadded-up rag down the seat tube, presumably to stop water/gunk from getting down to the BB, but the rag had the unfortunate effect of holding moisture at the point where it was wedged in the tube, and led to it rusting out in that area, from the inside.

HillRider

Yep, the problem with "waterproof" is that it works both ways. Once water does get in, it can't get out.

Kimmo 

I'd say you have a bike fit problem. If your frame is too large it might be making the best of a bad situation, but my guess is it's most likely from clueless assembly.

With the seat knuckle in front of the post, your effective seat angle is likely too steep; for best results you should start with a position that allows the bottom of your patella to sit directly over the pedal spindle, and tweak slightly to taste.

And if you're going to do that, you might as well ensure the seat is as high as you can get it without your hips rocking, keep the ball of your foot above the pedal spindle (toe clips are good) and spin a cadence of 80-100rpm.

The difference between the horribly inefficient way most casual cyclists ride and the proper way to do it is night and day.

dabac

That might have been me, I had a beater bike that died that way. A quite surprising experience.

pursuance

If we look hard enough, we will find fly poop in the pepper.

A friend was a mechanic for the Schwinn race team back in the early '80s and they used tight fitting tube over the seatpost clamp because the BB was not sealed(cartridge) and it kept moisture out.(road water/sweat/pee, as some did on the bike)


I will try to post less in this forum as there are already enough guys here with pliers & hammer.

Continuity

Naww - don't get me wrong - it's a potentially really useful tip. I guess I just wanted anyone reading who might want to try it to know to check the sleeve occasionally to make sure that it's not holding any moisture in that area.

I myself recently fitted a 'sleeve' made from cut-up bits of old MTB tube to wrap around my lower headset race to hopefully prevent road spray/salt etc. from contaminating the grease there. Seems to be working fine up till now, and doesn't seem to tend to hold any moisture there after riding in the rain.

A tight-fitting sleeve could be fantastic at keeping nearly all rain/piss/sweat etc. from going down the seat-tube, but could still hold a small (only has to be a layer not many microns thick) amount in place that wouldn't evaporate for a *long* time, and be enough to start corrosion.

PS - I like that expression.

Chitown_Mike

I have been tweaking the bike more this season but come to find out that the hoods are a little too low, I set them at the very end of last season and didn't get any real rides in, so the tape has to come off and I need to move them around. Hopefully that will fix some of the seat issues.

I will ask, I noticed the clamp I have has a very limited aft position with the nuts IN FRONT OF the seat post, but if I put them in BEHIND it allows for more movement to the rear, which as given me a more even and comfortable stroke the last few rides. I also have not lost any angle on the seat by doing so, should I be wary of positioning the seat too far aft even if it creates a more comfortable riding position?

I should also say I am definitely not racing this, it is my long distance rider/nice day commuter.

Kimmo 

What do you mean by 'a very limited aft position with the nuts behind the seat post' exactly? If the knuckle is behind the post, the seat a couple of inches further aft. I don't understand how 'if I put them in front it allows for more movement to the rear' makes any sense.

Also, when I refer to a steeper seat angle, I'm talking about the angle from the BB to the centre of the seat against horizontal. 74° is steep, 71° is slack.

Grand Bois

You have that backwards. If the clamp nuts are behind the post it allows the saddle to be moved back farther. The saddle rails are clamped just above the nuts.

Some very old frames with very laid back seat tubes require that the clamp be installed backwards in order to get the saddle far enough forward. Some even had a seatpost in the shape of a "7" where the saddle was clamped to the horizontal part to move it well ahead of the seat tube. I'm sure your bike wasn't built in the '30s, so the nuts go behind the post.

Chitown_Mike

Kimmo, you're right that didn't make any sense, because I wasn't making any! Fix the post above. And thanks for the clarification on the angle you meant, I was thinking the angle of the nose of the seat not the middle of the seats relation to the BB.



I realized I had the nuts originally in front of the post, but once I switched them that allowed for my stroke to even off, I just had everything backwards in my head. Probably because I was working on the bike by looking upside-down as I tightened the nuts on the seat the other day when I posted this. I didn't realized my mistake till after I got home and looked at it.