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Racer Tech Thread

Old 02-13-16, 12:56 PM
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Originally Posted by bostongarden
In addition, the main reason that I have this question is because it is my understanding that one of the key functions of the EXPANDER PLUG that goes inside the steerer is to keep the stem, when tightened, from crushing/compromising the steerer.
I've never heard this myself and don't worry or think about the location of the plug when installing the stem. That said, most carbon fork manufacturers specify a relatively low maximum spacer stack for safety reasons.
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Old 02-13-16, 02:17 PM
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i don't know anything about cannonade headsets, BUT, i've been told that the "expander plug stops the stem from crushing the steerer tube" myth isn't actually true. that being said, it's pretty easy to adjust the location of the expander plug in the steerer tube, no? not like the star plug on a metal steerer that can go down but not up.
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Old 02-13-16, 06:25 PM
  #3103  
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FWIW, my 2010 Look 585's fork uses no expander plug, and I think current ones are the same way. Proper use of the torque wrench is what keeps you from messing up your steerer.
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Old 02-13-16, 07:00 PM
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Originally Posted by mike868y
i don't know anything about cannonade headsets, BUT, i've been told that the "expander plug stops the stem from crushing the steerer tube" myth isn't actually true. that being said, it's pretty easy to adjust the location of the expander plug in the steerer tube, no? not like the star plug on a metal steerer that can go down but not up.
Correct.
I think the advantage of an expander plug is that it spreads the load inside the steerer tube compared to the star nut. Nothing to do with the stem.

Anyone tightening a stem enough to damage a steerer tube should be tested for steriods.
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Last edited by Homebrew01; 02-17-16 at 05:55 AM.
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Old 02-13-16, 09:10 PM
  #3105  
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Thank you all for your replies to my headset question!!
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Old 02-13-16, 11:00 PM
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I don't understand why Cannondale says no spacers on top of the top cap. Doesn't make sense.
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Old 02-14-16, 11:32 AM
  #3107  
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Originally Posted by shovelhd
I don't understand why Cannondale says no spacers on top of the top cap. Doesn't make sense.
So, it sounds, practically, I don't need to worry about stem aligning with the plug, assuming that I tighten stem bolts to spec
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Old 02-14-16, 12:33 PM
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Oh, you mean so you don't crush the steerer? It would take a heck of a lot of torque to do that. The main reason you want to use an expander plug is that star nuts cut the inside of the steerer, but expander plugs don't. Use carbon paste on the plug and torque to spec. Then set your stem height where you want it, tighten down very lightly. Set the preload to remove all play. Make sure there is no binding lock to lock. Straighten the stem and torque the steerer bolts to spec. It took me longer to type this than it would take to do this job.
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Old 02-14-16, 08:59 PM
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Originally Posted by shovelhd
I don't understand why Cannondale says no spacers on top of the top cap. Doesn't make sense.
brand image is the only thing I can think of.
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Old 02-14-16, 09:48 PM
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Originally Posted by shovelhd
I don't understand why Cannondale says no spacers on top of the top cap. Doesn't make sense.
it has to do with the design of their expander where the top cap itself is the expander. The idea for any expander is that the stem has a portion of the carbon steerer that is 'reinforced' by the expander. That expander , unlike specialized or other brands where there is an expander sleeve and top cap, is about the same length of the stack of a stem. So if there are too many spaces above the stem (imagine 30mm of spacers above, then the bottom bolt (and potentially the top bolt) of a two bolt stem will be clamping a portion of the steerer below the expander



and it looks sweet with no spacers....
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Old 02-14-16, 10:08 PM
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Cervelo actually uses an aluminum inner sleeve glued inside the carbon steerer tube, with a star nut. Seemed a little strange to me, and made cutting the steerer tube a little more work, but I guess it works fine. Their manual also states no spacer needed above the stem.
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Old 02-15-16, 07:27 AM
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Specialized also says no spacer above the stem, or at least that was what the instructions said for my wife's 2011 Tarmac.
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Old 02-15-16, 07:41 AM
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I see nothing in my 2015 Tarmac's manual about that, but I'm sure they'd still take extreme issue with the stack I've got going on.
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Old 02-15-16, 07:59 AM
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Originally Posted by topflightpro
Specialized also says no spacer above the stem, or at least that was what the instructions said for my wife's 2011 Tarmac.
iirc that's only if you're using specialized's stupid adjustable angle stem.
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Old 02-15-16, 09:15 AM
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Originally Posted by mike868y
iirc that's only if you're using specialized's stupid adjustable angle stem.
That may be the case.

Originally Posted by TheKillerPenguin
I see nothing in my 2015 Tarmac's manual about that, but I'm sure they'd still take extreme issue with the stack I've got going on.
IIRC, it was in the separate instructions for the fork/headset.
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Old 02-15-16, 09:59 AM
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On a side note: I once took a cut piece of steerer tube and attempted to crush it with a stem and a torque wrench. I maxed out the torque wrench, then went gorilla on it, it never broke.
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Old 02-15-16, 10:06 AM
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yeah i'm pretty sure the crushing the steerer tube thing is a total myth.

speaking of steerer tubes, i cut my first one yesterday. granted, it was steel so not that complicated/high risk. roommate now thinks i'm a psycho after he walked into the kitchen and caught me hacking away at it.
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Old 02-15-16, 10:50 AM
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On a related note, I love my Giant Propel, but damn, it's _super_ hard to find decent stems/spacers/microspacers for the 1-1/4" steerer in the US.
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Old 02-15-16, 05:36 PM
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Everyone, I can't thank you enough for the many comments about the Cannondale steerer and their topcap and expander system. Indeed, Cannondale wants the stem to be aligned with the expander.

However, it sounds like many are suggesting that the alignment is not critical because it is hard to imagine that the stem would crush the steerer were it overlapping a space where there was no expander.

I could go with a different brand expander and top cap system. Although, I have the Cannondale SI as pictured by jdms, and, I wouldn't mind using it.
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Old 02-15-16, 05:49 PM
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Originally Posted by mike868y
...
speaking of steerer tubes, i cut my first one yesterday. granted, it was steel so not that complicated/high risk. roommate now thinks i'm a psycho after he walked into the kitchen and caught me hacking away at it.
I knew you had Dremel envy.
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Old 02-16-16, 01:36 AM
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Originally Posted by mike868y
yeah i'm pretty sure the crushing the steerer tube thing is a total myth.

speaking of steerer tubes, i cut my first one yesterday. granted, it was steel so not that complicated/high risk. roommate now thinks i'm a psycho after he walked into the kitchen and caught me hacking away at it.
carbon's not some special material. it cuts just like anything else.

Originally Posted by mike868y
iirc that's only if you're using specialized's stupid adjustable angle stem.
that 'stupid' stem is pretty useful for people dialing in their position. the reason there are no spacers allowed on top is that the top-cap is angled so that the whole thing sits flush when the stem's angle is adjusted.

Originally Posted by TheKillerPenguin
I see nothing in my 2015 Tarmac's manual about that, but I'm sure they'd still take extreme issue with the stack I've got going on.
test: is the expander plug's bottom above or below the bottom of the stem? if it's below, you're good to go.

specialized now supplies as default it's longer expander plug...so unless someone is doing something very weird with spacers, everyone should be good to go. you don't really NEED the expander plug, but it does distribute the forces on the stem and prevent slight/accidental over tightening from instantly ruining the steerer. one could even do some JRA with a huge spacer stack to dial in position before cutting...if one is careful.
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Old 02-16-16, 01:39 AM
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Originally Posted by jsk
Cervelo actually uses an aluminum inner sleeve glued inside the carbon steerer tube, with a star nut. Seemed a little strange to me, and made cutting the steerer tube a little more work, but I guess it works fine. Their manual also states no spacer needed above the stem.
those sleeves are often found on pro bikes--you epoxy it to a (cut) steerer, and it stiffens up the front end.

i've done that with a few bikes and it is a noticeable change.

star nuts aren't generally used on a carbon steerer (unless you have a metal insert); expander plugs can be used on steerers of any material.

did you cut the stem with the sleeve in place? ugh. it's not really different than cutting a steerer as normal, but it's unfortunate if that was glued into place before you chose the steerer length.
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Old 02-16-16, 06:09 AM
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FYI if you overtighten a stem it doesn't crush the steerer right away, but it will leave indents in the steerer after a while. At that point it becomes a bit tricky to adjust a different stem, like if your original stem was a bit cockeyed or something.

Hm. This may have been a seatpost. But I don't think so.
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Old 02-16-16, 06:48 AM
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Sort of OT: I'm on a Cdale Evo which I had the stem slammed. Then I switched to a different stem which was a little taller where it clamps to the steering tube. I was in a very gentle crash, basically laid the bike over and when it was checked out, the steering tube was cracked. I am not sure if the crash caused the damage or if it was caused by tightening the stem onto a steering tube that was essentially a few mm too short.
@tetonrider: I have never heard of those sleeves; is that a diy type of thing or can they be purchased?
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Old 02-16-16, 08:28 AM
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Originally Posted by tetonrider
those sleeves are often found on pro bikes--you epoxy it to a (cut) steerer, and it stiffens up the front end.

i've done that with a few bikes and it is a noticeable change.

star nuts aren't generally used on a carbon steerer (unless you have a metal insert); expander plugs can be used on steerers of any material.

did you cut the stem with the sleeve in place? ugh. it's not really different than cutting a steerer as normal, but it's unfortunate if that was glued into place before you chose the steerer length.
Yeah my fit has changed since getting the frameset, and I would have had about 40mm of spacers above the stem if I didn't cut it.
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