eschlwc

a sweet old retiree gave me three bikes yesterday (all small framed, lower-mid-level unfortunately) and some miscellaneous parts, including a specialized riser stem with an aluminum wedge. i've never seen an aluminum wedge or expander before in a quill stem. it's so light, i thought i'd try to repace it in my davidson (it too has a specialized stem), but the davidson's is an expander, not a wedge.

anyway, i was wondering why these aren't more common and if the normal wedges/expanders are made of iron due to potential sticking issues.

ever seen an aluminum expander? is that just asking for trouble?

3speedslow

That's an interesting question. First guess it might be race related. Something kin to the use of alloy freewheels on race day then changed back for road work.

more knowledgable ones will correct me, still is learning.

OldsCOOL

Isnt the Cinelli 1R an expander? Sheeesh, it's only been 2 weeks since it was out for restoration.

miamijim

Lots of expanders out there....a majority of Cinelli stems have expanders. The grammo has an aluminum wedge.

In regards to a stem getting stuck...the wedge/expander material is never an issue, its always the stem body.

OldsCOOL

Right. In my recent case the stem was fine but the seatpost was stuck tight. Cinelli stems rock.

Chombi

Weight weenie component and parts makers like OMAS most likely made aluminum stem wedges and bolts to use on Cinelli and alike stems......
Not the best parts to go weight weenie on , IMO......

eschlwc

two recent acquisitions have stuck stems. with one, i can't turn the bolt at all. they're both still soaking. fingers crossed. they're both really nice bikes.

but maybe i should keep this aluminum wedge from this (ugly) riser stem. seems kinda rare.

and if it's never the wedge that sticks, that's a really nice weight savings...

uncle uncle

I don't know if there is cross over knowledge that will be beneficial here, but in the aircraft industry, where lots of aluminum gets used, we shy away from aluminum threaded parts. Bolts never seem to glide through the threads as well as say steel; usually the weight reduction gain isn't offset by the hassle.

Chombi

Problem usually comes from the threads galling, then seizing because of it, then you have to also factor in how the bolt could stretch and reach maximum elongation towards it breaking....

Lascauxcaveman 

But I would worry about over-torquing and stripping the wedge's threads. I really like to know my stem is nice and tight, having erred on the side of caution once...

eschlwc

with all the concern, it's odd i found this aluminum wedge attached to a riser stem.

we don't usually associate riser stems with "weight weenie."

Fidbloke

I think you're right, and it is likely to be something to do with the way that Aluminium holds a thread. I've worked on aircraft and they always use anchor nuts and steel treaded inserts instead of just bunging a thread through a big thick bit of 'Ally' plate.
Steel will be harder and less likely to strip. It's possible that dissimilar metal corrosion could grip the bolt into the Aluminium wedge and never let go.

J T CUNNINGHAM

Fastener (bolt) tension and galling are the bugaboo of all threaded assembly and with aluminium even more-so. May I suggest that while using a S/S anti-seize

on the threaded area, the use of thread-locker on the under-side of the bolt/washer combo will also aid with friction reduction, especially if the bolt is AL.

I really hate to mention torque, because it has little to do with how tight a made-up really fitting is; (really!) what is truly paramount is bolt stretch.

Now for The Secret! When using an anti-seize, reduce the torque value by 40% for steel. This reduction is due to the now lubrication that has reduced the

turning effect (friction) that are required within the Torque Tables for Threaded Fasteners.

A Premier Fastener Co education, along with automotive and industrial experience have shown to be a "Problem Solver" for stripped threads and broken bolts.

Do bear in mind however, none of the above relates to a threaded assembly that cannot be threaded to "hand tight" to begin with.


Regards,
J T

canopus 

If it was aluminum it was probably from a race bike in the 80's. The only reason to use them was weight. DK stems on 1980's BMX bike came with aluminum expander bolts for the race bikes back then. I loved the stems but had to drill and tap the expander bolt for a threaded axle (3/8X24tpi) from a Bendix coaster hub and place a bolt under it to keep it from stripping. The ones we got on geared bikes were high end geared bike usually.

mtnbke

I bought a Precision Instruments dial-torue wrench just for working on bikes. It turns out that "click style" torque wrenches are just completely no precision instruments, and aren't accurate across their range. The Dial style that Precision Instruments invented, they actually invented the torque wrench, is accurate to within 2% across the entire range of the wrench. I couldn't believe how inaccurate my Craftsman "clicks style" torque wrench was. All the "click style" torque wrenches I've seen (Pedros, Park, etc.) are just as bad. It just not an effectively precise way to build a torque wrench.

I use Zinn/High Sierra cranks. When I installed my Zinn crank the hilarious thing was that the torque rating that Zinn gives as the required torque rating actually started to strip the threads of the crank. Zinn must have been basing his numbers off of using an inaccurate "click style" torque wrench not something actually accurate like a dial-torque wrench.

My next big purchase will be a Precision Instruments split-beam click torque wrench. Its not as accurate as the Dial which is 2% accurate across the entirety of the range, as the split beam click torque wrenches are only 4% accurate, but I like that I can drop it and not affect its calibration. The thing people don't know about a Craftsman, Pedros, or Park "click style" torque wrench is that just leaving them set at a particular setting ruins the calibration of an already imprecise tool. They are essentially socket wrenches and shouldn't be used as torque wrenches at all. If it matters get a Dial style.

Precision Instruments torque wrenches aren't cheap, but if having the right torque matters, there really isn't a substitute precision tool. You can sometimes find them really cheap for the ones they make for other labels like Snap-On on eBay. The weird ranges that are perfect for bicycles have no market amongst mechanics.

Precision Instruments: The Finest Torque Wrenches

You can send in a Park or Pedros or Craftsman "click style" torque wrench to a lab for calibration and you'll get a report showing you that it was essentially useless. The more I learned about Precision Instruments and their 2% accurate Dial wrenches the more ripped off I felt when I bought my $100 Craftsman. I didn't pay that much more when I replaced the new Craftsman with a functioning "real" torque wrench, my Precision Instruments Dial type.

Grand Bois

Every stem I've ever owned that uses a wedge has had an aluminum wedge. They're not exactly uncommon. Can you buy a Nitto stem that does not have an aluminum wedge? Not that I know of.

Where have you been since May? I've missed you posts.

Reynolds 

Dura-Ace quill stems had aluminum expanders IIRC.

eschlwc

woo hoo!

yeah!

hurray!

ok, make that "one has a stuck stem." the '78 fuji's came loose today! only took five weeks of soaking.

yeah!

still batting 1000.

OldsCOOL

Good job. And a collective sigh of relief goes out from the crowd.

What did you soak it in?

Chombi

For some reason, I never owned a stem with either an aluminum wedge or wedge bolt. And I have owned many of different brands.
The weight weenie God's have been very nice to you GB!

Cross Creek

Six of the seven quill stems I own have aluminum wedges. Three of those are Nitto Technomics, one is a Nitto Dirt Drop, one is a VO, and the other is no name. Not a wide sampling, I realize, but apparently aluminum wedges aren't rare or racing-specialty parts.

eschlwc

^ huh. that's interesting. and reassuring as far as putting into use, this, my first, aluminum wedge. of the 25+ stems i've owned, i can think of only one as a nitto. it didn't have an aluminum wedge. can't remember if it was an expander or not.

i know! i gave it another two weeks after checking it the last time. i was about to give up yet again (and give it another two-week soak), when i gave the loose bolt another big rap. joy of joys!

equal parts atf and acetone in the upside down steerer. i'm three for three with one to go -- an '81 mondia with full 531, full campy record, and a fully stuck stem. fingers still crossed...

OldsCOOL

Hope for the best. Sounds like an effective concoction. My Colnago had a stuck seat post so I tipped it on the stand and filled the seat tube through the Club cutout (oh gee that's what those are for) using PB Blaster. Let it sit for two days with a full tube. Later, I put the seat on it and whacked the nose of the seat with a rubber mallet. Did the trick.

uncle uncle

I did a quick look see on the web.. it does appear that nitto uses an aluminum alloy wedge, as do others. Some of the wedges may have a threaded insert (so that might remedy the problematic threading issue). I wasn't able to find a wedge porn site or post. Aluminum and steel aren't the best of buddies, so there is still a metal mismatch issue that would lead to galvanic corrosion, given the appropriate environment (I'd use an ample coating of water proof grease between the bolt and wedge). I would suspect that the threads in an alloy aluminum wedge could more easily be damaged, but then an alloy wedge might also deform better, thus providing better "bite" to the head tube. Like in a lot of designs, every possible solution usually has a list of good, okay, and not-so-okay details. Given that there appears to be an ample amount of real world data to support the use of aluminum alloy wedges, I wouldn't hesitate to go ahead and use it.

eschlwc

what it feels like when it finally gives