Scott said:Qui si parla Campagnolo said:Scott said:Qui si parla Campagnolo wrote:
>Scott wrote:
>
>>Qui si parla Campagnolo wrote:
>>
>>>Lee Hurd wrote:
>>>
>>>>I need to find a 140, -17 stem that won't damage a Reynolds carbon steerer,
>>>>and I couldn't find any info at the Reynolds composites site even though
>>>>they say there is a list somewhere. Can anyone tell me if the newer Ritchey
>>>>stems will work? That's the only road stem in that size that I've found so
>>>>far, and it's got the diagonal slot Reynolds doesn't like.
>>>>
>>>>Thanks for any help.
>>>
>>>Ritchey stems work well with Reynolds forks. leave 5mm spoacer above
>>>the stem to prevent crushing of the very end of the steerer.
>>
>>How can you crush the end of the steerer tube, if you have the
>>compression plug installed?
>
>Easy. The guts inside the steerer are not at the very end of the
>steerer. If the stem overlaps the end of the steerer and you really
>gorilla it tight, you pinch/crush it. We put 5mm on top of all the
>stems for any carbon steerer.
Actually, the compression cap is EXACTLY at the very end of the
steerer, unless you've cut the steerer many, many mm too short. If
that's the case, then the compression cap won't work as it won't reach
the steerer tube. It's either at the end of the steerer or not at all.
Won't work any other way.
I guess on your but the part that expands to hold it into the steerer
is not at the end, and the part that is threaded 'should' be a wee bit
below the end of the steerer, or the cap will hit that before the HS is
tightened.
Quoted message said:The compression cap (that hard plastic thingy that inserts in the end
of the tube) certainly does NOT go completely past the end of the
steerer tube, as it also has to reach beyond the top of the stem.
The expansion plug for Ouzo Pro forks is NOT plastic, but all metal.
Not sure what you are referring to.
If
Quoted message said:you've cut the steerer so that it reaches within a couple of mm of the
top of the stem, taking into account the spacers you will use, the
compression cap will extend into the steerer well past the top bolt on
the stem and thus prevent that bolt from crushing the steerer. Unless,
of course, you tighten the stem so tight as to crush the steerer AND
the compression cap simultaneously.
Now, I'm sure there's at least one person out there who'll say they've
done it, but I'll have to see it to believe it.
If it's so important to have the steerer tube extend beyond the stem,
what's so magical about 5mm? Why not 10, or 20??? How did this
mystical 5mm come to be? Is it really reasonable to expect that a stem
tightened at the end of the tube will crush it, but if you just move it
down 5mm it won't?
WE, at the shop, do not overlap the stem clamp portion on any carbon
steerer. WE at this bike shop ensure that the steerer is completely
thru the stem to prevent crushing. Not sure why you are being so pissy
about it->If it's so important to have the steerer tube extend beyond
the stem,
Quoted message said:what's so magical about 5mm? Why not 10, or 20??? How did this
mystical 5mm come to be? Is it really reasonable to expect that a stem
tightened at the end of the tube will crush it, but if you just move it
down 5mm it won't?
If the carbon steerer doesn't go past the clamp portion of the stem,
but is partially below the end of the stem, it can be crushed...with
the top bolt being overtightened. If you can't visualize this-ohh
well....We are not keen about paying for a carbon fork we goon up.
I'm not being pissy. Just questioning your declaration that there's
something to be gained, besides adjustability, by extending the steerer
tube above the stem.
I can visualize it quite well. There's a portion of the compression
cap that extends into the steerer tube. I thought it was plastic, you
say it's metal. Not important, except that if it's metal it's probably
even MORE resistant to crushing.
So, please visualize this: the steerer tube is cut so that it comes to
within 2mm from the top of the stem. You insert the compression cap
into the steerer tube. This cap extends well over an 1" into the
steerer tube and serves to reinforce the steerer tube well past the top
bolt on the stem.
How much force do you think it would take to crush the steerer tube
PLUS the compression cap simultaneously? I suppose that if you
installed a stem on the end of the steerer with the top bolt a cm or
more above the end of the steerer and you did not put the compression
cap in, you could damage the steerer tube by overtightening the stem.
With the end of the steerer tube cut just below the top of the stem and
the compression cap installed I just don't see crushing the steerer
tube with only the force you could exert by tightening the stem bolts.
I don't expect that you'd care to demonstrate this on a fork, but if
you want to prove your point, I've got an idea. Next time you cut a
carbon steerer tube, put the part you just cut off into a stem and try
to crush it, with or without a compression cap installed. I'd be
curious to see just how far above the end of the steerer tube you'd
have to put the top bolt of the stem to damage the tube.
I've got a new frameset coming next week. After cutting the steerer to
length, I'll try it myself. I'll let you know how it works out.
I seem to understand your description, but let's get the terms right.
The expander is a two-piece aluminum bit through which travels a steel
bolt. The lower portion of the expander is partially split into four
sections, all but save the lower bit, which is threaded for the steel
bolt. It also has a conical sink into which the upper portion
correspondingly fits. In a groove around the lower portion is a rubber
o-ring. The upper bit is threaded at the top to receive the aluminum plug.
When tightening the steel bolt (5mm), the split lower bit expands inside
the steerer, anchoring it there. Afterwards, turning the plug clockwise
(6mm) pulls it down towards the anchor, dragging the stem and spacers
with it, resulting in preload of the hs bearing.
Now, as for tightening/over tightening/crushing the carbon steerer,
that's what the plug portion is designed to minimize/alleviate. It is a
reinforcing plug for gorilla types who insist on over tightening things
without a torque wrench, and it is designed (from my interpretation)to
protect the upper end of the steerer, not the entire stem zone. True
Temper has a similar concept going with their glue-in reinforcement
plug, but that covers the entire stem clamp zone of the steerer.
The best way to avoid crushing problems (admittedly difficult for a
thoughtful person) is to tighten the stem "just enough". That is, so it
doesn't move in normal use, or loosen. In lieu of that, use the torque
wrench. Leave as little room above the steerer/below the top cap as
possible to maximize strength, usually no more than 5mm.
As for your 14cm stem, I don't know of any limitations from Reynolds.
Nonetheless, I'd follow the instructions (in your literature and above),
and not worry about it. Now, where you can find this stem, I don't
know. Several makers make a 140mm stem, but no-one I could find in 73^
(aka -17^). Why not go for a 80^ and lower it a bit?
Robin Hubert