1 1/8" Compression Plug/Stem on 1" Fork w Shim?

[proletariandan]

Hey everyone,

First post relating to an awesome Landshark I bought from a member here. It has a 1" Carbon Reynolds fork and I'd like to run a 1 1/8 stem and was planning to use a 1" compression plug until I got one from FSA and realized that it doesn't use a standard top-cap so I can't swap it out for a 1 1/8" top-cap. Will a 1 1/8" compression plug work? Suggestions?

Thanks!
Dan

[DRZRM]

The 1" compression cap should work just fine on most 1 1/8" stems, I just did the same thing (and posted pretty much the same question (http://forums.thepaceline.net/showthread.php?t=113585)) with a Serotta F-3 fork, a Moot Open Road stem, and a 1" Reynolds compression plug/cap, and it all worked just fine.

[proletariandan]

The 1" compression cap should work just fine on most 1 1/8" stems, I just did the same thing (and posted pretty much the same question (http://forums.thepaceline.net/showthread.php?t=113585)) with a Serotta F-3 fork, a Moot Open Road stem, and a 1" Reynolds compression plug/cap, and it all worked just fine.

So the 'top-cap' had a large enough OD that it rested on the 1 1/8 stem? I just assumed that wouldn't be the case - I'll try it today.

I was hoping to be able to use a Thomson 1 1/8 topcap but I don't know of any compression plugs that use a removable/standard topcap...

PS. Nice profile pic!

[jtakeda]

You're going to be using a shim to put the 1 1/8" stem on the 1" steerer. The shim will have the correct OD to put the top cap on.

[DRZRM]

You're going to be using a shim to put the 1 1/8" stem on the 1" steerer. The shim will have the correct OD to put the top cap on.

Nope, that does not work because the pressure has to be on the stem, not the shim inside of it. In my case, the Moots stem was a bit taller than the shim. Reynolds wants the stem 3mm higher than the cut steerer, ad as it worked out, with a single narrow spacer under the stem, the shim went right to the top of the steerer, the stem was right around 3mm over that. Reynolds insists that you not use a spacer on top of the stem, but the Reynolds top cap was wide enough that it sat on the stem securely. I can't vouch for the FSA, but the Reynolds works fine.

[jds108]

If the 1" FSA compression plug doesn't work, look for a different brand and style of 1" compression plug. The Look branded 1" plug would allow you to use any kind of top cap, so you could combine their 1" plug with a 1 1/8 spec top cap.

From my experience, the FSA and Reynolds branded 1" plugs are the same (so they both require the proprietary top cap). just fyi.

[ultraman6970]

The top cap is just a top cap, you can put what ever top cap you want as long as it allows you to press the stem down and the screw is long enough.

As for the FSA compressor, Im using one of those and they work better than other ones in the market, just my opinion.

[proletariandan]

Nope, that does not work because the pressure has to be on the stem, not the shim inside of it. In my case, the Moots stem was a bit taller than the shim. Reynolds wants the stem 3mm higher than the cut steerer, ad as it worked out, with a single narrow spacer under the stem, the shim went right to the top of the steerer, the stem was right around 3mm over that. Reynolds insists that you not use a spacer on top of the stem, but the Reynolds top cap was wide enough that it sat on the stem securely. I can't vouch for the FSA, but the Reynolds works fine.

Finally got around to starting this install and it turns out I have a bit more than 1/2 inch of extra steerer with a CK headset, Thomson spacer, and X2 stem. For some reason, the spacer is a mm or two taller than the stem so if the topcap needs to sit on the stem that will be impossible without a 1 1/8" spacer somewhere.

Maybe I'm missing something but I'm trying to think this through mechanically and can't figure out why the topcap needs to rest directly on the stem, ie, why couldn't the top-cap press down on the top of the shim or a 1" spacer sitting above it as long as the stem is below the top cap and centered around the compression plug? Isn't all the stem doing applying inward pressure? I don't see why it needs to have downward pressure applied to it necessarily.

[jtakeda]

Im also curious to the answer of this question. I'm running a 1 1/8'' stem on a 1'' steerer and the top cap goes inside the top of the stem pushing the spacers into the headset. I have no play with the headset and have ridden the bike without any problems.

I've only gone a couple rides so if this is a problem I would like to know.

I think this is the same question OP has. I'm using this shim http://images.jensonusa.com/large/fk/fk306z12_____1____118.jpg

it has a lip on the bottom that is 1 1/8'' in OD so it rests flush with the stem.

[oliver1850]

The top cap is just a top cap, you can put what ever top cap you want as long as it allows you to press the stem down and the screw is long enough.



No, not on any of the FSA plugs I have anyway. The FSA top cap is made like a Reynolds, and doesn't have a screw at all.

[oliver1850]

Finally got around to starting this install and it turns out I have a bit more than 1/2 inch of extra steerer with a CK headset, Thomson spacer, and X2 stem. For some reason, the spacer is a mm or two taller than the stem so if the topcap needs to sit on the stem that will be impossible without a 1 1/8" spacer somewhere.

Maybe I'm missing something but I'm trying to think this through mechanically and can't figure out why the topcap needs to rest directly on the stem, ie, why couldn't the top-cap press down on the top of the shim or a 1" spacer sitting above it as long as the stem is below the top cap and centered around the compression plug? Isn't all the stem doing applying inward pressure? I don't see why it needs to have downward pressure applied to it necessarily.

You need the 1" to 1 1/8" shim to be slightly shorter than the stem bore it fits inside. They come in different lengths, I found 34, 38 and 40 mm listed from a quick look at ebay. The one that Profile provides with their stems is 1mm shorter than the stem. This allows the top cap to compress the whole headset/spacer/stem stack, so there are no gaps. I think what you describe would work if no spacers were used, but if you are using spacers they would rattle around, as the compression is being done by the shim. You could push the stem down to hold them in place, but you'd have a gap between the stem and the top cap. I can send you a shorter shim or cut one down if need be.

As to the original question, the 1" FSA top cap measures 1.18" in diameter, so it engages a 1 1/8" stem by .028 (.7 mm). It will have more engagement surface if you put a thin 1" spacer above the stem, but should work without one.

The shim that jtakeda posted should be installed with the lip on top of the stem, so that the top cap rests on the shim, and the lip compresses the stem onto the parts below. Again, the shim shouldn't stick out below the bottom of the stem.

Most shims I have seen do not have the lip shown in the posted pic. They have a constant wall thickness top to bottom.

[oliver1850]

Nope, that does not work because the pressure has to be on the stem, not the shim inside of it. In my case, the Moots stem was a bit taller than the shim. Reynolds wants the stem 3mm higher than the cut steerer, ad as it worked out, with a single narrow spacer under the stem, the shim went right to the top of the steerer, the stem was right around 3mm over that. Reynolds insists that you not use a spacer on top of the stem, but the Reynolds top cap was wide enough that it sat on the stem securely. I can't vouch for the FSA, but the Reynolds works fine.

I'm wondering why Reynolds is worried about using a spacer on top of the stem. After thinking about it, I think they must want the plug to be at a level slightly below the bottom of the stem. Perhaps they are worried about the effects of too much stem clamping force plus the vertical forces transferred from the handlebar combining to break the steerer off. I'd always thought that compression plugs were mainly to prevent the steerer from breaking from clamping pressure, but I can see that having the plug extend slightly lower than the stem could strengthen the steerer in the area that it's most likely to fail when being ridden.

[Chance]

Finally got around to starting this install and it turns out I have a bit more than 1/2 inch of extra steerer with a CK headset, Thomson spacer, and X2 stem. For some reason, the spacer is a mm or two taller than the stem so if the topcap needs to sit on the stem that will be impossible without a 1 1/8" spacer somewhere.

Maybe I'm missing something but I'm trying to think this through mechanically and can't figure out why the topcap needs to rest directly on the stem, ie, why couldn't the top-cap press down on the top of the shim or a 1" spacer sitting above it as long as the stem is below the top cap and centered around the compression plug? Isn't all the stem doing applying inward pressure? I don't see why it needs to have downward pressure applied to it necessarily.

If my understanding of your question is correct, your implied point seems valid but only to a point. If your goal was limited to only preload the headset bearings then pushing down on shim and down through spacers can preload the headset. At that point if you tighten the stem it will lock the shim tight into place around the steerer and keep everything in place. As long as you are pushing down on something that extends past the top of the steerer you could accomplish preloading of headset bearings.

However, proper function involves more than just preloading the headset. For starters, the sidewalls of a shim are very thin. Going from 1-inch to 1-1/8-inch means the sidewalls of the shim are only 1/16-inch thick. That’s not very sturdy and probably can’t distribute bending loads evenly to the carbon steerer in the same way as the much thicker stem can. There are probably many other reasons not to depend on the shim itself as the primary path to transmit stem “riding” loads to steerer. A thin 1/16-inch thick aluminum shim is pretty strong in pure compression sandwiched between stem and steerer, but beyond that it wouldn’t be all that strong. Would probably be easy to deform if end loaded. Which would then unload the headset. Best to do it right per manufacturers’ instructions in my opinion.

[DRZRM]

I assume that the reason that Reynolds wants there to be no spacer on top is because they want the compression plug to line up with the clamp force of the stem, if you move up the top cap you are likely to move up the compression plus too without moving up the stem. By cutting the steerer 3mm below the top of the stem, it sort of forces you to put the compression plug in the right place. If you need to raise the whole thing (stem and shim) above the steerer (as opposed to recutting the steerer length) you can use 1" spacers below both the shim and stem to raise them slightly (3mm according to Reynolds) above the steerer. They don't want spacers on top of the stem, but I image a narrow one would not displace the compression plug too much, though I'm not really sure what size would work best (1" over the shim or 1 1/8th" around it). With a Moots Open Road and a Thomson shim, the stem was a bit longer than the shim, and ended about in the middle of that 3mm overhang between steerer and topcap. If the shim were longer than your stem, the only way I can imagine making it work would be a 1 1/8th" spacer that the shim slid into to push the stem up, but rather than doing that I'd cut down or replace the shim with a shorter one.

FWIW: My old Legend with the 1" F-3 fork that I got from Oliver1850 is awesome.

Hope that helps.

[proletariandan]

However, proper function involves more than just preloading the headset. For starters, the sidewalls of a shim are very thin. Going from 1-inch to 1-1/8-inch means the sidewalls of the shim are only 1/16-inch thick. That’s not very sturdy and probably can’t distribute bending loads evenly to the carbon steerer in the same way as the much thicker stem can. There are probably many other reasons not to depend on the shim itself as the primary path to transmit stem “riding” loads to steerer. A thin 1/16-inch thick aluminum shim is pretty strong in pure compression sandwiched between stem and steerer, but beyond that it wouldn’t be all that strong. Would probably be easy to deform if end loaded. Which would then unload the headset. Best to do it right per manufacturers’ instructions in my opinion.

First off, thanks for the response. I may, in the end, just cut things down once I get the right cockpit configuration but for now I want to avoid cutting anything since I only have an extra 1/2" or so of steerer.

Apparently Thomson offers different shim heights, which I was unaware of. The shim did feel very sturdy, however. Plus, as long as it is underneath the stem I don't see how it would be subject to any load other than the vertical load of the stack.

Perhaps having the stem fully within the stack allows it to pass some of the force applied to the handlebars to the stack rather than simply around it's contact surface.

It seems like the only way to properly set this up would be to have the right/enough spacers so that you effectively have a solid 1 1/8" stack from the top of the headset, with no gaps in either of the diameters...

[nighthawk]

Bringing this back up, because I'm about to cut a 1 inch carbon steerer, and I'm unsure about figuring out the length.

The fork is a Columbus minimal with 1 inch carbon steerer. I'm using a CK nothreadset, and an enve stem. I'll need to get a shim for the stem, and that's where I'm stuck.

How do I decide which sized (height) shim to use? Do I want it the same "stack" height as the stem or do I want it smaller? Is there a specific size space that I want to leave?

I have two compression plug options, the FSA 1 inch one and I also have a Columbus compression plug. The FSA has a particular type of cap, while the Columbus it looks like I could swap out for any size top-cap I wanted.

So the questions right now, which shim do I use? Are there any reasons to definitely or definitely not put any spacers above the stem? Do I use a 1 inch or 1 1/8th inch top cap? Also, should the spacers be 1 inch or 1 1/8th.

First time mating a 1 1/8th stem to a 1 inch steerer... so feeling sort of stupid right now.

[ultraman6970]

The shim can't be too short neither too long, the problem is that if the shim is too short the stem gets lose no matter how much you tight the bolts, if its too long you might have issues with the spacers. Ran into this problem with a carbon stem and a 1inch fork. The only shim i had was too short and the stem was simply lose big time.

The nice about using a longer shim (couple of mm longer) is that you actually be sure the spacer will fit around the shim, then you put the cap over that 1 1/8 spacer or what ever you want to do.

3 mm longer or shorter is ok, more than 3mm shorter could be a problem depending on the stem as it happened to me.

[oliver1850]

If you have extra steerer length, you could use a shim longer than the stem, then put a 1 1/8" spacer above the stem, and use the plug that will take a 1 1/8" top cap. This will work nicely, but you may want to consider that Reynolds apparently recommends not to use spacers above the stem. They must want the plug nearer to the bottom of the stem rather than nearer the top.

If you don't want to run a spacer on top, get a shim that's just a bit shorter than the clamping surface of the stem, a mm is all you need. Some 1" caps have a large enough OD to engage a 1 1/8" stem, but some will fall through. For that reason, it's better to use the 1 1/8" cap, it will give more contact area on the stem in any case. If you're using the FSA 1" plug, I would think you could use their 1 1/8" top cap with it. They have a pretty good selection of parts on their website, but I don't know if you can buy the top cap seperately from the plug. I may have both sizes on hand, will try to check to see if they are compatible.

You could also use a 1" spacer on top of the stem and the 1" top cap, as long as the spacer is thick walled enough to have good contact area on the top of the stem. You want the shim shorter than the stem for this as well.

I have some shims if you need one.

I would like to see someone come out with a plug that's taller than what's currently available. I try to avoid carbon steerers myself.

[nighthawk]

Thanks for helping me think through this. Part of the problem is that I don't have the stem yet... I just picked it up off eBuy and am waiting on delivery.
Once it arrives I can start putting things together and see where I'm at.

Thanks for the shim offer, Oliver.. but I think I'll just see if I can get one of each that Thomson offers and see how each'll fit with the plugs and top caps that I have.

I'll post up some pics here once I get it all pieced together.

Cheers!

[proletariandan]

I accidentally ordered a shim that was just a few mm too tall but it worked out since that meant I could use a 1.125 spacer and top-cap. I'm currently running a 20mm spacer on top of my stem on the Reynolds. Not recommended but the FSA plug has a fairly long reach so is still supporting the stem. Hopefully I don't regret that...