weird leather saddle tension bolt appears to *decrease* leather tension
 

I recently purchased a leather saddle from Rideable Bicycle Replicas. It's a $20, made-in-India knock-off of a Brooks, and I was curious and not necessarily expecting a lot because of the price. There is another thread discussing knock-off saddles and "you get what you pay for" and all that, please go there if you want that discussion. Again, I'm aware that this is a cheap knock-off in part for show of having a leather saddle, although it is supposed to be rideable.

In this thread, I specifically want to discuss the tension bolt system of the RBR leather saddle, and whether the design makes any sense at all.

Leather saddles work, in part, by suspending leather between metal plates in the nose and at the rear of the saddle (these are what is held to the leather by rivets). The rails of the saddle are the "brace" to hold distance between the front and rear of the saddle.
Since leather tends to stretch a bit over time, there is typically some kind of adjustment bolt to push the nose of the saddle more forward from the rails, to increase tension in the leather as needed.

Here are close-up pictures of the tensioning bolt in a Brooks saddle. By turning the nut, you force the bolt further forward from the front of the rails to increase tension in the leather.
http://bikeforums.net/attachment.php...hmentid=263425http://bikeforums.net/attachment.php...hmentid=263426

In contrast, the tension bolt system in the RBR leather saddle does cannot increase tension in the saddle. Whereas the Brooks (and other systems) push the nose of the saddle forward (braced off the rails), tightening the nut on the RBR saddle pulls the nose back toward the rails, thus decreasing the tension in the leather. (Note that you need a screwdriver to hold the bolt while tightening the nut, but that isn't any particular problem.)
http://bikeforums.net/attachment.php...hmentid=263406http://bikeforums.net/attachment.php...hmentid=263407http://bikeforums.net/attachment.php...hmentid=263410

I realize these pictures aren't perfect for showing the mechanism.
In both the Brooks and the RBR saddles, the rear of the bolt goes through the metal loop attached to the saddle rails, and the front of the bolt goes to/through the forwardmost part of the steel plate that is riveted to the leather in the nose of the saddle.

I have shown the saddle to a mechanic at my LBS, and he thought the same thing that I did, that tightening the bolt would decrease tension in the leather.
But I still kinda hope that I am misunderstanding the mechanism, OR that there is some other way to rig this in order to push the nose of the saddle forward instead of pulling it back.

Any thoughts, either on the design of the tension mechanism, or how it could be modified/rigged to add tension into the leather?

I can't make out the mechanism properly.

Could you take a pic from the opposite angle to the fourth pic?

Regardless, you can prolly re-jig it to work, IMO.

@Kimmo, I added a picture and a bit of text to hopefully explain things better.

Perhaps it was assembled incorrectly?
It may also be a bad copy without regard tom proper function but looks right from a distance.

The way it is currently assembled (which is how it was received), tightening the bolt (while holding the nut with a screwdriver so it does not rotate) will pull the nose of the saddle back towards the rails, instead of pushing it forward from the rails.

There is no obvious way to re-assemble the parts such that the tension bolt would push the nose of the saddle forward relative to the rails. Although there is a fair chance I could rig something up if I get a a different bolts.

+1 to it being assembled incorrectly. I think the nut needs to be behind the nose piece. When unscrewing the bolt, it would push against the nosepiece and move it away.

It looks like it will work to me.
Tightening the nut will pull the one half of the stamped piece in and it will push the other half (not clearly seen in pic) out into the leather.

@demoncyclist, agree that there needs to be some force applied to the backside of the nosepiece, not the front.
I don't think there is room for the nut to fit behind the nosepiece and still be accessible to a wrench. If that did fit, it would work as you suggest.

Put the nut on the other side of the steel nose piece.

If you can reassemble in that order, you would only need to turn the bolt with a screwdriver, not the nut- which would probably be "captive" on the other side of that piece.

I say, have you tried turning it the other direction?

@garage sale GT - if you turn the nut in the other direction, you simply loosen it. The only way that doing this could work to apply pressure to increase tension in the saddle is if the nut fit behind the backside of the nosepiece.

Reassembling this way is trickier than initially appears though, even if the nut does fit behind the nosepiece.
This is because the bolt threads through the metal loop that is attached to the rails. So turning the bolt would thread it at an equal rate through the nut and the plate. So I would need to turn the nut while holding the bolt fixed with a screwdriver.

:d

Remove bolt and nut
Replace bolt/nut with a single bolt with a solid head, that goes behind the metal piece (but does not go through the piece). Take this opportunity to use a bolt with a smooth, round head.
Cut notch in back of bolt to tighten/loosen it with screwdriver
Profit?

My thoughts exactly. I think if you reassembled as DC describes it would work right.

-G

the nut does indeed fit behind the nosepiece, but it is very difficult to turn. Crescent wrenches (even cone wrenches) cannot reach it. So I'll need to use a wider nut or some kind of spacing washer between the nut and the nosepiece.
http://bikeforums.net/attachment.php...hmentid=263524

I have also been planning (as ivan_yulaev also suggests) to put a round-headed machine screw (drilled for screwdriver) in place of the bolt. This could screw all the way into the back of the plate that connects to the rails, and then turning the nut to push the nose of the saddle away from the rails (and thus add tension to the leather) wouldn't require "holding" the bolt with a screwdriver.
Also, the replacement bolt should be a bit longer, as the stock bolt one would run out of real estate pretty quickly if the leather proved stretchy.

I checked other web shots and it appears the tensioner is properly assembled. I also find it difficult to believe that it would loosen turning the slotted end either way! That just doesn't make sense. Your saddle was supposed to come with a manual, but I would assume if you ignore the nut and keep turning the slotted/threaded end counter clockwise, like you are loosening it, the bracket the slotted/threaded pin is screwed into would rotate under the supports and eventually contact the nose piece and push it forward. This may first loosen the tension until the bracket contacts the nose piece, then it should start to tighten the tension.

You increase tension with a screwdriver, turning it clockwise.
The nut is PERHAPS supposed to be used as a locknut, so you tighten it while holding it in place with a screwdriver.

The only thing I don't like is the fact that screw could screw up the leather, it doesn't have a wide, flat head like the Brooks patent. I would put a regular, flat head screw instead of the original one.

http://bikeforums.net/attachment.php...hmentid=263532
http://bikeforums.net/attachment.php...hmentid=263533

@garage sale GT (and onespeedbiker),
by "turn the nut in the other direction" I was assuming you meant "turn the nut counterclockwise relative to the bolt." You may have meant re-positioning it?

@onespeedbiker - this is a $20 made-in-India knockoff of a Brooks, and did not comes with a manual. Where did you find webshots of the tension mechanism of this RBR saddle? (seriously, I'm interested, as I've seen nothing about how their mechanism is supposed to work. That's why I started this thread)

Again, turning the bolt with a screwdriver doesn't do anything to change tension because the bolt will just thread through the nut, and the threaded hole in the curved plate attached to the rails, at the same rate. To move the nosepiece you need to hold the bolt from turning, and turn the nut relative to the bolt.

@Slaninar - are you suggesting the curved-head end of the machine screw at the nose of the saddle, or behind the curved plate that attaches to the front of the saddle rails? Note that in the latter case, the machine screw would need to be threaded along its entire length.

re-assembly completed.
putting the bolt on the other side of the nosepiece (as pictured above, in post #16) allows the assembly to push the nose forward, thus increasing the tension in the leather.
I replaced the no-headed machine screw using a screw with a head.
I also stuck a washer between the nosepiece and the bolt, so I can reach the bolt more easily with a wrench.
With the machine screw all the way in, I can just "loosen" the bolt relative to the screw, which moves the nose of the saddle further away from the rails.
http://bikeforums.net/attachment.php...hmentid=264383http://bikeforums.net/attachment.php...hmentid=264384

Main potentail problem is that the curved metal plate (which fits over the end of the rails, and holds the machine screw) rotates a bit with pressure in this direction. But it doesn't appear to rotate too far.

The only real question is whether a saddle with springs can do much to tension the leather (as the springs will deform under tension, thus limiting the amount of tension which be put into the leather).

Verdict: Even when increasing tension in the leather, sitting on the saddle causes the leather toward the rear of the saddle to sag markedly, and my sit bones feel like they are sinking in just in front of the metal plate at the rear of the saddle. My guess is that the rear metal plate actually rotates forward (and since it is attached to springs, not directly to the rails, it has the flexibility to do so).
Note that I'm 6'5", 200 pounds, but I think that this would happen to a lighter weight rider.

Sure the saddle is rideable, but not remotely comfortably. Not like a leather saddle is supposed to be (and I realize that the leather is supposed to be very hard until broken in).
I suppose I could lace it, but I'm not sure it's worth the trouble.

This makes me curious how sprung leather saddles work to maintain sufficient tension. With the Brooks B67, are the springs just a lot stiffer (particularly toward bending) than this RBR saddle's springs? Or does it depend on lacing?

Sprung saddles, such as the B.67, should have tension rods which link the cantle-plate to a fixed point at the front of the saddle and eliminate the problem that you've got.

Thanks for that mention. Here is a picture of how sprung saddles should be constructed (as you mention about the B67).
http://bikeforums.net/attachment.php...hmentid=264461

In contrast, this RBR saddle only has one set of rails, and so the metal plate riveted to the rear of the saddle is basically floating on the springs.
http://bikeforums.net/attachment.php...hmentid=261678

The RBR saddle could work if it were designed without springs (and, of course, had a better implementation of tension bolt).