Tiny gap between spacer & -17 stem because geometry?
 

Is this normal/ok? Slid my -17° stem onto the steerer and because of the angle it doesn’t fully clear the spacer width so it kind sits slightly off kilter and there’s a small gap where you can see the steerer.
Will this cause bad wear/tear on the stem or mess with anything? Is it because it’s only an 80mm stem and if it were longer it might clear?


https://cimg9.ibsrv.net/gimg/bikefor...8826c0c8f.jpeg

Was the frame faced when headset install? I always have a pro install headset, because I don't have the tools to check the frame. I think your headset is crooked.

It is hard to tell from the photo provided. That Zipp stem has rounded contours whereas the spacers are squared off. The angle on the stem looks like it is beyond horizontal making it look like a track stem. Bike shops may have a stem facing tool where they can freshen up the mating surface.

God I love my quill stem…

it’s a +/- 17° stem which when you flip it over makes the stem pretty parallel to the ground - depending on your headtube angle. It’s not as drastic as a track stem.

If you flip the stem from how you have it in the picture, it will be not almost parallel to the ground. It will be rising 17 degrees in relation to the head tube. With it oriented like you have it in the picture, that is the closest it will be to parallel on that bike. I am not an expert, by far, and not sure from the picture, but it does look like the head set cup could be set crooked. Look at the interface between the top cap and the spacer below it. Does it look like the top cap is centered and square on with that spacer? Depending on the shape of the underside of the cap, if it is not, it could interfere with the stem seating correctly when the cap is torqued.

It may or may not be an issue. If the head tube ends are not parallel to each other, (and perpendicular to the head tube), and the steerer is not centered, it will probably cause more stress on the bearings at a particular point since any impact will not be absorbed evenly over the headset bearings. How this effects longevity, in miles, is hard to say.

It may also impact how smooth the handlebars turn through the entire arc.

If it is a spacer issue and you are able to pre-load the bearings so they are smooth with no play, it probably has no impact once the stem is tightened to the steerer tube.

John

Take the stem off and examine the mating surface. It should have been machined flat where it meets the spacers.

Are you saying that the steep downward angle of your stem causes the stem to ride up from the spacer below the stem at the front of the steerer? Somehow that does not seem too likely.

No. Stem angle and length do not affect each other.

After checking to make sure the headset was installed square, I'd bevel the spacer and call it good.

That looks like a knock off stem that was not properly faced to make the mating surface flat.

Good point. Here's some photos from the SRAM/ZIPP site of the current model. The Zipp logo is larger and there is a sharper bevel at the steerer clamp area groove and slightly extended tapered area on the top and bottom clamp in the photos. The OP's stem is shorter and could account for using a smaller Zipp label and graphics come in different versions over the years from what I've seen. It could also be an older version stem that doesn't look exactly the same at the steerer clamp or just distortion from the photos but maybe worth contacting SRAM about. Service Course SL Stem | ST-SC-SL-B2 | Zipp (sram.com)

As far as I know it’s a legit stem. It came from a bike shop and came in normal Zipp packaging:


https://cimg8.ibsrv.net/gimg/bikefor...983fff22f.jpeg

The stem on the website you linked to is showing the +/- 6° stem, so the angle is much less than the +/- 17° stem I ordered.
And the logos are slightly different due to its shorter length (80mm) than what’s usually shown on websites (100mm or more most likely.)

I ordered a cheap headset press that should arrive today and I’ll double check making sure the cups are in and straight. I will also try a different spacer though pretty sure it won’t matter because they all came in the same package.

Stay tuned?

Update:

got the tool today and pressed the headset cups more snugly and straight - as far as I could tell. So I’m happy about that.

The spacers are a bit thick I guess their circumference is a little more. Than the stem steerer clamp area.

The kicker is, once I got the stem on there after putting on a different spacer, the gap looked closed on the right side. But still persisted on the left side (same as first pic in first post)

Looks good? (Zoom in )
https://cimg6.ibsrv.net/gimg/bikefor...754c32645.jpeg

and the left side (zoom in to see gap)

https://cimg6.ibsrv.net/gimg/bikefor...d7675387c.jpeg

https://cimg5.ibsrv.net/gimg/bikefor...3ea31fd8c.jpeg

so now my question becomes why is it showing on one side and not the other? Is the internal facing of the stem uneven? Is the headset uneven? Is the…?

Oh and the angle of the stem still barely clears the upper edge of the spacer. The metal black spacer I had before, the stem was still laying on it so it raised it a mm or so like in my first post.

Certainly looks like the stem isn’t properly faced. I would take it back to the shop where you bought it, ideally still on the bike, so they can get eyes on the problem.

Reviving this thread: I've had the exact same issue with multiple (5) Zipp Service Course SL stems now (both the 17-degree and the 6-degree variety). This is not a bug, but a feature on these stems. SRAM customer support are telling me it's fine, but I'm giving up on this stem, as I'm just not sure how the uneven, not perfectly square lips would affect headset durability in the long run. The main reason is that these stems are rather thin at the steerer clamp and the top/bottom circumference is not machined/faced flat. The cheaper 6061-alloy non-SL Service Course stems are much better in this regard, so'll I'll take those for a small weight penalty instead (though they don't come in a 17-degree version, but the 6-degree version will do for one bike of mine)

Certainly looks like the lower face of the stem isn't flat, rather than the stem snagging the edge of the spacer. I don't know if there's such a thing as a "stem facer" tool, but I suppose you could flatten the face by running is along a broad file of on some emery paper tape to a bench top. The problem would be ensuring that the bottom- and top faces were truly parallel. If it bothers you, I suggest sending it back for replacement - it's clearly faulty. However, apart from being a little unsightly if you go looking for flaws, I don't know if it makes a lot of difference. The stem-spacer interface isn't weight-bearing - once the stem-spacer-headset stack is preloaded with minimal torque (1-2 Nm) through the top cap, it's the stem-steerer friction that carries any rider weight on the bars/stem

Check the post dates people!

Did you try it with a conical aluminium spacer?

Thank you for the update information... it appears Zipp is doing too much surface finish/prep work after machining the working surfaces..My Fuji has a Zipp stem on it... same thing found... it's also been in place and ridden like that for the last 5 years, with my pudgy old butt stomping on it, on a roughly paved linear trail, mostly.
i'll conclude it's annoying to see, but doesn't seem to effect performance much, if at all.
And Zipp needs to have a long talk with the finish dept.

This is what SRAM customer service has told me: "The ends of the steerer tube clamp are machined thin for weight savings. The unevenness you notice should not affect preload." The thing is, I don't buy 100% the claim that the unevenness should not affect preload, though I'm glad to hear you've had no issues. I've a few similar lightweight alloy stems, and none of them had those lips machined so thin. The Zipp Service Course SL is the only stem I've had in 20+ years of riding multiple bikes that has this issue. Every other stem (including the cheaper Service Course 6061 alloy version) has the edges of the clamp machined thicker and faced perfectly flat. Whereas I've now had 5 Service Course SL stems plagued by this unevenness. A uniform, even pressure from contact between the lower edge of the stem and the spacer/top bearing cover underneath should be much better at distributing load.
Here are some photo showing the issue (these are the photos I sent to SRAM/Zipp)


https://cimg6.ibsrv.net/gimg/bikefor...2977853543.jpg
https://cimg7.ibsrv.net/gimg/bikefor...c45d969a29.jpg

You say it is a issue. But what is the trouble that this is causing. Other than just not looking like others.

uneve pressure on the tapered cone, which can cause uneven loading of the top headset bearing.
they are rather thin, flimsy little rings of steel.
they also have tiny tiny little bearing balls in them, making them more vulnerable to warpage of the races.

frankly, i find the go-to sizes of bearings for the semi and integrated headsets ridiculously inadequate for long term durability.
we've both seen the now shunned "Caged bearings" outlast the bikes and riders, with basic minimal care.

Seems likely that the headset isn't preloading evenly, which could accelerate wear. Or it might be rigid enough to spread the load.