# saddle rails too small for seatpost clamp



## centurionomega (Jan 12, 2005)

I just got a new Selle Italia SLR on eBay for pretty cheap. My first impressions are that this is the firmest saddle I have ever ridden. You can tap the top with your thumb and it sounds like a bongo drum!

That firmness is taking a little getting used to, but I like the look of the saddle and the shape fits me pretty well too.

I bought it for my commuter road bike, but am thinking about moving it to my main super bike where I might enjoy its assets more fully.

The problem is the FSA SL-K seatpost won't clamp down on the SLR saddle rails. And when I say won't clamp down, I mean not even a little bit. The Flite that is on there now must have bigger saddle rails than on the SLR.

My question is, does a LBS have some sort of shim to slip on the saddle rails before you tighten it down? Any ideas for rigging it at home?

If not, I guess I'll have to leave things as is because I'm not getting a new seatpost.

Thanks for reading.


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## rx-79g (Sep 14, 2010)

I'd be pretty shocked if this was the case. Could you post a picture of the post with the seat that doesn't fit - a closeup showing where the rails enter? I imagine something else is causing the problem.


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## FTR (Sep 20, 2006)

Had this problem with a new San Marco Zoncolan saddle and my Moots seatpost.
The San Marco saddle rail diameter is so narrow that the clamp cannot be tightened far enough to hold it before bottoming out.
$120 down the drain until I can find someone to buy it.


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## cmg (Oct 27, 2004)

contact FSA and see if they can't send you the 2 pieces that clamp on the saddle rails of correct diameter.


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## centurionomega (Jan 12, 2005)

*I saw your post...*



FTR said:


> Had this problem with a new San Marco Zoncolan saddle and my Moots seatpost.
> The San Marco saddle rail diameter is so narrow that the clamp cannot be tightened far enough to hold it before bottoming out.
> $120 down the drain until I can find someone to buy it.


I did a search for this problem and found your post in the Moots forum.

It is weird that the Selle Italia Flite works so well with the FSA SL-K seatpost, and the Selle Italia SLR does not.

I have heard of saddles with differing rail diameters. This must be a case of that.

If I had some calipers I could add some solid numbers to the thread.

@rx-79g. I will post a video of the SLR rattling freely in the SL-K seatpost clamp if I get a chance. Does RBR allow videos?


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## rx-79g (Sep 14, 2010)

centurionomega said:


> I did a search for this problem and found your post in the Moots forum.
> 
> It is weird that the Selle Italia Flite works so well with the FSA SL-K seatpost, and the Selle Italia SLR does not.
> 
> ...


If you have a place to post a video, you can always link to it here.

I'm just interested to see if there is something interfering with the clamp - or get an idea how much of a difference there is. It's just suprising that something as standard appearing as metal seat rail diameter could be a problem.


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## FTR (Sep 20, 2006)

rx-79g said:


> If you have a place to post a video, you can always link to it here.
> 
> I'm just interested to see if there is something interfering with the clamp - or get an idea how much of a difference there is. It's just suprising that something as standard appearing as metal seat rail diameter could be a problem.


Looking at my 2 saddles side by side I would suggest that there is approx 4-5 mm difference in rail height.
So it does not appear that there is any standard.


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## wim (Feb 28, 2005)

FTR said:


> Looking at my 2 saddles side by side I would suggest that there is approx 4-5 mm difference in rail height.
> So it does not appear that there is any standard.


Not quite sure what you mean by "rail height," but the standard for round rails is 7.0 mm diameter; for oval rails it is 7.0 x 8.5 mm.


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## Kerry Irons (Feb 25, 2002)

*Something's funny*



centurionomega said:


> The problem is the FSA SL-K seatpost won't clamp down on the SLR saddle rails. And when I say won't clamp down, I mean not even a little bit. The Flite that is on there now must have bigger saddle rails than on the SLR.



This does not make sense. Please explain where the interference is. I wore out my Flite and put on an SLR, no issues whatsoever. If your problem is that the upper clamp and lower clamp are touching before they fully grab the saddle rails, then you should modify your seat post clamp to eliminate that interence. 15 minutes or less with a hand file should do the job. There's something wrong with a seat post clamp design that lets this occur.


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## FTR (Sep 20, 2006)

wim said:


> Not quite sure what you mean by "rail height," but the standard for round rails is 7.0 mm diameter; for oval rails it is 7.0 x 8.5 mm.


Will take some pics when I get home but suffice to say the diameter of my San Marco saddle rails is far smaller than my Selle Italia.


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## frdfandc (Nov 27, 2007)

I was using a Selle Italia SLR XC Gel Flow with my FSA SL-K seat post without issue.


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## centurionomega (Jan 12, 2005)

*yes, that's it.*



Kerry Irons said:


> This does not make sense. Please explain where the interference is. I wore out my Flite and put on an SLR, no issues whatsoever. If your problem is that the upper clamp and lower clamp are touching before they fully grab the saddle rails, then you should modify your seat post clamp to eliminate that interence. 15 minutes or less with a hand file should do the job. There's something wrong with a seat post clamp design that lets this occur.


I made an impromptu caliper set with an open-end adjustable wrench and a metal ruler.

The rails on the Flite measured 8mm.

The rails on the SLR measures ∼6.25mm.

My seatpost clamp on the SL-K apparently only works with the oval saddle rails on the Flite? It is bottoming out before it closes enough to clamp the SLR saddle rails. 

I didn't think about grinding down the inside of the clamp so it would close more. What's a measly 1-2mm on a seatpost clamp?:thumbsup:


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## centurionomega (Jan 12, 2005)

*here's some pics*

One thing I forgot to mention if it matters. It is a Flite Genuine Gel saddle with the oval rails.

Here's a couple of shots of all the offending parties.

Overall, it's not that bad is it?

I just need to shop for a saddle with giant rails to one day replace my Flite.


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## ocd (Jul 9, 2004)

*i have had the same thing happen several times*

with cheaper stuff and w a campy seatpost also w. newer saddles w older posts, but same head design on the post. i wrapped some black friction tape around the seat rails where it will sit in the posts craddle, building it up. clamp the seat in the post's head tigten up and cut away the excess tape that is still visible. i have this arrangement on my fixed gear. hasnt moved a drop in years. not elegant, but it works.


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## rx-79g (Sep 14, 2010)

centurionomega said:


> One thing I forgot to mention if it matters. It is a Flite Genuine Gel saddle with the oval rails.
> 
> Here's a couple of shots of all the offending parties.
> 
> ...


That's funny. It doesn't look like the FSA post couldn't compress another coulple of millimeters. What part of the clamp is stopping it from doing so?


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## wim (Feb 28, 2005)

centurionomega said:


> Here's a couple of shots of all the offending parties..


Does that FSA have a two-bolt (left-right) head?


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## centurionomega (Jan 12, 2005)

*blow-apart view*



rx-79g said:


> That's funny. It doesn't look like the FSA post couldn't compress another coulple of millimeters. What part of the clamp is stopping it from doing so?





wim said:


> Does that FSA have a two-bolt (left-right) head?



Here is a disassembled and assembled view of the seatpost clamp. The lowest part is to the left, the top clamp is in the middle. and the single attaching bolt is to the right. The two clamp pieces are arranged book leaf style. The 2nd shot is of how it all goes together on the seatpost.

There is this central channel in the clamp that bottoms out before it clamps down on the smaller saddle railed saddles.

It looks like if I could get a new top part of the seatpost clamp with a slightly different geometry to close up tighter. That seems too much like getting a whole new seatpost and I am quite the cheapskate.

But someday, when I need a new saddle, does anybody have any recommendations for saddles with oval saddle rails? CF preferably.

Until then, I am getting more than awesome at setting up my saddles the same way every time on my bikes.


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## rx-79g (Sep 14, 2010)

centurionomega said:


> Here is a disassembled and assembled view of the seatpost clamp. The lowest part is to the left, the top clamp is in the middle. and the single attaching bolt is to the right. The two clamp pieces are arranged book leaf style. The 2nd shot is of how it all goes together on the seatpost.
> 
> There is this central channel in the clamp that bottoms out before it clamps down on the smaller saddle railed saddles.
> 
> ...


Well, no fixing that. I would not remove any material from the clamp parts - you'd be thinning the thinnest parts.

If you contact FSA with the problem, they may simply give you a new clamp, if they have one.

You could also put bottom and/or top shims of thin aluminum on the rail clamps.


I didn't realize carbon seat rails were very common anymore. A poor material for rails, IMHO.


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## FTR (Sep 20, 2006)

rx-79g said:


> Well, no fixing that. I would not remove any material from the clamp parts - you'd be thinning the thinnest parts.
> 
> If you contact FSA with the problem, they may simply give you a new clamp, if they have one.
> 
> ...


I looked at shimming my Moots seatpost.
I would worry about this as a long term solution as I think that the aluminium would end up breaking.
Looking at centurionomega's pics and I would estimate that there is a similar difference in rail diameter between my Flite and San Marco's rails.


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## rx-79g (Sep 14, 2010)

FTR said:


> I looked at shimming my Moots seatpost.
> I would worry about this as a long term solution as I think that the aluminium would end up breaking.
> Looking at centurionomega's pics and I would estimate that there is a similar difference in rail diameter between my Flite and San Marco's rails.


A shim, done correctly, can't break. It has nowhere to go, and isn't structural. It is just a spacer made of some material that resists crushing.


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## FTR (Sep 20, 2006)

rx-79g said:


> A shim, done correctly, can't break. It has nowhere to go, and isn't structural. It is just a spacer made of some material that resists crushing.


Well maybe on some seat clamps you can find a safe way to do it but with my Moots post I would have needed a pretty thick piece of aluminium and then bent it to fit inside the head to compress the 2 pieces that ultimately clamp the post.

Mine is this design:


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## rx-79g (Sep 14, 2010)

FTR said:


> Well maybe on some seat clamps you can find a safe way to do it but with my Moots post I would have needed a pretty thick piece of aluminium and then bent it to fit inside the head to compress the 2 pieces that ultimately clamp the post.
> 
> Mine is this design:


If you wrap the rails in thin sheet of aluminum the length of the clamp surface then tighten, the extra will stick out of the side gap. Disassemble, trim the extra and re-assemble.


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## FTR (Sep 20, 2006)

rx-79g said:


> If you wrap the rails in thin sheet of aluminum the length of the clamp surface then tighten, the extra will stick out of the side gap. Disassemble, trim the extra and re-assemble.


Tried that.
Because you sort of have to twist the saddle into position, the wrap gets carved up and pulled off.
The clamp design is a pain to use even without having to contend with something wrapped around the rails.
With the San Marco rails the clamp completely bottoms out so I would need a substantial amount of extra material.


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## Kerry Irons (Feb 25, 2002)

*Thinning?*



rx-79g said:


> Well, no fixing that. I would not remove any material from the clamp parts - you'd be thinning the thinnest parts.


All you would have to do is grind a mm or so off the "tips" of the upper clamp. It wouldn't weaken anything. You're not thinning anything by doing this.


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## rx-79g (Sep 14, 2010)

Kerry Irons said:


> All you would have to do is grind a mm or so off the "tips" of the upper clamp. It wouldn't weaken anything. You're not thinning anything by doing this.


What's that going to do? The clamp is bottoming out in the rounded middle area.


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## Gimme Shoulder (Feb 10, 2004)

centurionomega,
I have the same FSA post as you have, with the same clamping mechanism. Without the saddle in it I can close it almost down to nothing. I've had seven different saddles of various brands on it with rails of steel, Ti, and carbon with no problems. I'm sure neither of the saddles you picture would be a problem either. One thing that bothers me about your photo is that you can see the head of the bolt in the photo. On mine that bolt head recesses completely into the bottom of the clamp such that you should not be able to see it from that angle. Are you sure the bolt isn't somehow binding in the clamp?


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## rx-79g (Sep 14, 2010)

Gimme Shoulder said:


> centurionomega,
> I have the same FSA post as you have, with the same clamping mechanism. Without the saddle in it I can close it almost down to nothing. I've had seven different saddles of various brands on it with rails of steel, Ti, and carbon with no problems. I'm sure neither of the saddles you picture would be a problem either. One thing that bothers me about your photo is that you can see the head of the bolt in the photo. On mine that bolt head recesses completely into the bottom of the clamp such that you should not be able to see it from that angle. Are you sure the bolt isn't somehow binding in the clamp?


You can see the top and bottom parts touching in the center in the second picture. That has nothing to do with the bolt.

Maybe, since your's is different, FSA changed this clamp, which means that the OP could get the revised one from FSA for free.


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## Gimme Shoulder (Feb 10, 2004)

rx-79g said:


> You can see the top and bottom parts touching in the center in the second picture. That has nothing to do with the bolt.


Of course they're touching in the second photo. There's no saddle in the second photo. The question is, are they touching with the offending saddle installed? The OP did not provide a pic with the SLR on the FSA post. If the top and bottom are in fact touching with the SLR in place, then yeah, the bolt is not the problem. But not having all the information or the parts in front of me to compare, the suggestion is worth making.

By the way, this clamp would be super easy to shim with just about any malleable metal.


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## Kerry Irons (Feb 25, 2002)

*Oops*



rx-79g said:


> What's that going to do? The clamp is bottoming out in the rounded middle area.


When I looked at the picture, I thought it was the clamp tips that were hitting. Looking as hard as I should have looked the first time shows how wrong I was. The only solutions are to shim the saddle rails or get a different saddle.


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## centurionomega (Jan 12, 2005)

*SLR can stay on the commuter for now*



Gimme Shoulder said:


> Of course they're touching in the second photo. There's no saddle in the second photo. The question is, are they touching with the offending saddle installed? The OP did not provide a pic with the SLR on the FSA post. If the top and bottom are in fact touching with the SLR in place, then yeah, the bolt is not the problem. But not having all the information or the parts in front of me to compare, the suggestion is worth making.
> 
> By the way, this clamp would be super easy to shim with just about any malleable metal.


The clamp bottoms out on the central channel thingy before it puts any clamping pressure on the rails on the SLR. A picture wouldn't really show enough detail about how the SLR saddle is loose. That's why I was gonna post a video of the saddle flopping around, but...

By my saddle rail measurements there is only a ∼1.75mm difference in thickness between the saddle rails on the Flite and the SLR. The Flite rails are oval-shaped and thereby taller.

I also have started looking around on the side of the road for a small strip of aluminum I could use as a shim. I tried wrapping the SLR saddle rails with inner tube. It worked and didn't slip, but it looked kinda janky, and this is my super bike that we are talking about here.

I like the suggestion about contacting FSA to see if I could get a replacement clamp. I will give that a try too.

Plus, I've been riding the SLR a lot in the past few days, and my ass doesn't feel as much like tenderized meat as it did on the first day. I even went on a 25-mile ride in cargo shorts and didn't fare too badly.

Thanks for all of your kind replies, and if I find a shim, I'll post a pic of the patch job.


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## Gimme Shoulder (Feb 10, 2004)

centurionomega said:


> The clamp bottoms out on the central channel thingy before it puts any clamping pressure on the rails on the SLR. A picture wouldn't really show enough detail about how the SLR saddle is loose. That's why I was gonna post a video of the saddle flopping around, but...
> 
> By my saddle rail measurements there is only a ∼1.75mm difference in thickness between the saddle rails on the Flite and the SLR. The Flite rails are oval-shaped and thereby taller.
> 
> ...


Regarding the shimming, if you have a dremel tool with a cutting wheel (or know someone who has one), you could find a small piece of aluminum or brass or copper tubing at the hardware store and slice it down the middle to make two little "half pipes". The size would not be all that important as long as it's close, because it will open or close up when you clamp it. Or you could lay in a small piece of roof flashing sheet (also available at the hardware store). This stuff is malleable and easy to cut with scissors. make a one piece, with a hole for the bolt, or two half pieces. Again, it will shape itself when you clamp it. Like you said, you only need 2mm. Good luck.

P.S. If you do use a shim, it would work better between the rail and the bottom half of the clamp since it has more contact area.


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## rx-79g (Sep 14, 2010)

Gimme Shoulder said:


> Regarding the shimming, if you have a dremel tool with a cutting wheel (or know someone who has one), you could find a small piece of aluminum or brass or copper tubing at the hardware store and slice it down the middle to make two little "half pipes". The size would not be all that important as long as it's close, because it will open or close up when you clamp it. Or you could lay in a small piece of roof flashing sheet (also available at the hardware store). This stuff is malleable and easy to cut with scissors. make a one piece, with a hole for the bolt, or two half pieces. Again, it will shape itself when you clamp it. Like you said, you only need 2mm. Good luck.
> 
> P.S. If you do use a shim, it would work better between the rail and the bottom half of the clamp since it has more contact area.


These are both excellent ideas, and the tube idea would probably work on Kerry's Moots post, even.

For aesthetics, once you install the tubing or flashing sheet (good stuff - you can cut it with a couple passes of a razor), clamp it down real good. Then take it out and use the clamp impression to cut away the extra that sticks out. Reinstall and it should be really clean looking, and weight nothing.


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