How to stop a saddle slipping back?

[mjr]

When tightening the screws on the base of my old saddle (yay, it stopped the squeaking!), I noticed the saddle had a cut on it. Rather than wait for it to split nastily, I bought a new saddle which is a bit more suited to our rough roads (longer rails and a base with a bit more flex) and put the old one in the spares box... BUT

I fitted the new saddle where I want it and then, as I ride, it slips back in the clamp and if left, it goes back beyond the "Max" marked on the Cr-Mo rails. How should I stop that?

I'm contemplating a) tightening it up more and hoping I don't bend, snap or strip anything; b) dismantling, cleaning and trying to refit it with less/no grease (I don't think I used much anyway); c) adding a thin rubber or cork shim to the two clamps in an attempt to increase friction. Or is it a sign that something is already bent and should be replaced? It all looks OK but I've only the one clamp like it.

[CREPELLO]

Where did you grease the clamp? I might grease the bolt thread, but leave it at that. Do clean everything though.

You could try applying Loctite Threadlock compound. Or there's something called anti-slip paste for fitting carbon and alu parts. I've not used it before but it might help. http://www.sjscycles.co.uk/icetoolz-ice ... prod32547/

[531colin]

I have seen 2 causes for that.....
1....part of the clamp at the top of the seatpost bent
2....a shaped nut at the top of the assembly fitted the wrong way up, so it didn't exert pressure where its needed.

....I suppose if you omitted a washer, the bolt thread could bottom before the clamp is tight?

[mjr]

I greased the rails too. Maybe whatever I read was wrong or it's not needed for this type, so I'll clean it off and refit as the next move.

The seat post is alloy AFAIK and I think the clamp may be, but I'll test it with a magnet. I'm 99%sure I've not lost any parts and it's all the right way up. It may be bent but it looked OK and seemed to grip.

[misterrea]

had a problem with a brooks myself, overtighten was plan A -ended up wrapping emery paper around rails clamped on that cured it. rails ended up rougher and now
don't move without emery

[Vantage]

Can't for the life of me see any reason for anyone to ever grease saddle rails. Never did it myself and never had a problem. I suspect that's your biggest problem. Are the rails on the new saddle thinner than the old ones? Coke can shim maybe?

[mjr]

Thanks all. Clean and refit hasn't cured it, so next will be something to make it grippier. I don't think the rails are thinner but they might be very slightly.

[Brucey]

have you a picture of the clamp you are using?

In the broadest terms the clamp could be;

- bent
- misassembled
- simply not tight enough
- vulnerable to being greased
- unable/unwilling to grip narrower rails

BTW I would fight shy of deliberately roughening the saddle rails; this may well reduce their fatigue life. Having said this, if they are chromed steel, once greased, you will struggle to find anything much slippier.

cheers

[mjr]

Here's a back view of the seat clamp. A magnet will stick to the clamp but not the post. I also held the saddles against each other and could see that both of my old saddles (one too wide, one torn) have rails that are maybe 1.5mm wider in diameter, so I wonder if the clamp actually goes tight enough.

For my next trick, I'm inclined to try making it grippier and pad it by putting a very thin strip of either rubber or synthetic cork bar tape in the bottoms of the clamp, cut to thickness first and then side by side so there shouldn't be much variation in thickness between the two sides that could make it lopsided.

[Brucey]

steel clamps like those often bend when the bolt is tightened 'enthusiastically'. Once bent the arrangement won't hold a saddle with skinnier rails.

cheers

[CREPELLO]

Well something looks bent from the picture. Shimming with soft material isn't going to work. Time for a new post me thinks - they're not expensive..

[mjr]

The cork grippers seem to have worked on a short test ride of 3miles. Tomorrow is a day trip, so we'll see.

I know it's only £20 or so for a new post, but it's still £20 and a bit irritating if only the rails clamp is bent. Also, what's a good post that won't suffer the same fault?

[CREPELLO]

The 'hockey stick' pattern is popular and reliable for all but the heaviest or roughest users http://www.ebay.co.uk/itm/VAVERT-MICRO- ... 1e7a5fc882
£11 should cover it.

[Brucey]

if the seat pin works Ok on fatter rails then maybe you can fix it. If you can find some brass or aluminium shim stock ~0.5mm thickness then making a 'sleeve' for the rails might work.

I have tried all kinds of peculiar things to try and make bits work OK for just a little longer. The trick is knowing when to cut your losses.

In terms of time spent, for many working folk it just isn't worth the time to fiddle about with stuff like this; a new part could be a fifteen minute fix. It gives you a chance to upgrade, too. [For example the cheapo hockey stick seat post is actually a nice piece of kit in that they are reliable, there are no serrations to strip out, and they are infinitely micro-adjustable.]

Even if you are willing to spend a little time on it, you have to ask if the resultant part is really going to be reliable or not. One way of looking at it is that if you have more than fifty parts on your bike that are only 99% reliable, (or more than 25 parts that are only 98% reliable, etc) your bike is more likely than not to be 'not working' at any given time.

cheers

[PT1029]

The (steel) lower clamp plate (that the saddle rails rest in) has bent/sagged down (I've seen it often). Even if you got it tight, the plate would sag more with time.
When you get a replacement seat post, make sure the lower clamp plate is alloy. They are much thicker, do not bend/sag, and I have never seen them break as they are quite thick.
If you have another old seat post but the wrong diameter, sometimes the clamps can be swapped over, but the posts need to be pretty much the same make and same model, otherwise they to don't fit the seat post properly (different profile).