Trek T100 Tandem
T100 Notes
Hi all,
I've been reading a number of different forums here for some time now, and I've
gotten a huge amount of useful information from everyone. In fact, I found my
first tandem through this very forum. It arrived last week, and my brother and I
have built it up (we're fairly knowledgeable and handy; brother worked in a bike
shop for a while as well). We've got all the standard tools and were able to get
everything going well with one exception: the eccentric BB. The tandem is a Trek
T100 (I know it doesn't hold a candle to the higher-end tandems out there, but
it's in our price range and we're big enough to make it roll at around 190 each
and pretty strong).
First off, I want to make sure that I understand the proper adjustment for this
eccentric. On the side away from the timing chain and rings, it has a large hole
for a long bolt that extends essentially through the entire width of the
eccentric. There are four smaller holes (only about big enough to fit a 2.5 mm
hex wrench into); they are called rotator holes according to my Google research.
They are only about 1/2 to 3/4 inch deep. Two of these are before the large hole
and two beyond it, following an arc around perhaps 1/3 of the circumference of
the eccentric's face. According to repair procedures I found via Google, the
recommended procedure for adjusting this type of eccentric is to unscrew the
large bolt a few turns, insert a hex key into one of the rotator holes, and
rotate the eccentric to the desired position. Sounds quite easy, but...
Having attempted the above, it will not be as simple as that. I believe the
eccentric is frozen into position. It's aluminum, and of course it's in a steel
frame; so I'm guessing that I have an aluminum/steel freeze on my hands. I tried
a Liquid Wrench application to the seam between shell and eccentric, but that
didn't do me any good. I also applied moderate force via a rounded-off
screwdriver and a hammer, but the eccentric still wouldn't budge.
My questions then are:
Is there anything I don't know about how to adjust this type of eccentric (i.e.,
I'm not loosening something that I need to loosen before doing it)?
What suggestions might you experienced tandem riders/wrenches have for this
problem? I've heard of the ammonia bath and am willing to try it but would like
to exhaust any other possibilities prior to resorting to it.
Apologies in advance for cross-posting; I'll lay this out in the mechanics forum
as well, but thought it likely that someone out there in the tandem world would
have some ideas I might not get from that forum.
Thanks for all the knowledge I've gained while reading the forums, and thanks in
advance for any light you can shed on this dilemma. Hopefully I haven't made any
unforgivable newbie mistakes!
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TandemGeek
Trek used a wedge type eccentric for its tandems and it often times takes a
little brute force to get the things apart.
The textbook service procedure is to back out the eccentric bolt to expose the
head and then to tap it with a mallet to release the tension between the
eccentric and the wedge. However, the most often cited removal methods from
those who've owned the older Trek's include:
1. Remove the eccentric bolt and temporarily replace it with another, longer
bolt that has the same thread pitch and diameter and thread it as deeply as
possible into the wedge before hitting the bolt head with a hammer to drive out
the wedge. Note: the tandem frame must be braced by a helper otherwise the bike
will move with each hit, lessening the driving force.
2. The less brutal method involves placing a lever between the bolt head and the
crank arm and using the crank arm's rotation to drive the lever against the bolt
head and forcing it in. You only need to have about 1/2 of the eccentric bolt
head extending from the eccentric for this method to work. Cresent wrenches (aka,
spanners or adjustable wrenches), hammer heads, and other solid objects have
been listed as "levers" in previous descriptions that we've come across.
As for those "rotator holes", you can usually rotate the eccentric with your
fingers once they're loose. However, if you need to have added leverage you'll
want to pick up a Park SP-1 pin spanner (Green Handle).
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truckin
Thanks very much, TandemGeek. I'll have my brother give it a try as soon as he
can, and I'll report back on our progress (he has the bike in VA; I'm in NC for
the next few weeks).
--------------------------------------------------------------------------------
Joe
Check out www.SierraTradingPost.com, you can save 30 - 70%! :-)
truckin
TandemGeek-
I had my brother try the "whack it with a big hammer method," and it broke the
wedge free very quickly. He's pulled it out now and will reassemble it with
anti-seize and the proper amount of tension for the chain we put on it. Thanks
again for the information; I think we just needed to know it was OK to beat on
it a bit!
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LV2TNDM
If the bolt hole in the wedge extends all the way through the barrel nut to the
other side of the eccentric like on Cannondales, then a another method works
well. I recommend this as I've heard of the (rather long) eccentric bolts being
bent by the forces of hammering on them.
Unscrew the eccentric bolt to the point where it's just about to unthread from
the barrel nut. Screw in a shorter bolt from the other side - once it threads,
remove the long eccentric bolt. (this prevents the barrel nut from moving, which
would make things rather bad - you may not get the hole in the nut to line up
with the bolt again!) The screw from the other side should be threaded through a
backing plate (the hole in a headset wrench or cone wrench works great). With a
few washers and lube, screwing the bolt into the wedge from the other end will
pull it free as the backing plate bottoms out on the BB shell and/or eccentric.
I carry an extra long water bottle bolt & cone wrench on trips so I can adjust
timing chain tension anywhere. No need for a hammer and brute force!
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Maury Cohen
Our method for eccentric adjustment is to place the end of a screwdriver or long
allen tool into the adjustment hole and using the leverage of the crank arm to
spin the eccentric shell into proper tension.
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RJ_Mettlehorst
Great suggestion on pulling the wedge out from the left side instead of whacking
it out from the right! I'll definitely try that.
That leads me to two questions: First, do people prefer slathering things with
grease, or a coating of automotive-type anti seize compound? (I use 3M High-Temp
brake & engine compound - copper colored) My personal first instinct is to use
anti-seize, but I have to be a bit more careful with the torque - it is a far
better lubricant at high pressures than ordinary grease.
Second, what is an appropriate eccentric BB wedge bolt torque? How tight is
required? I'm thinking the forces really aren't tremendous, but it has to be
tight enough to keep the chain tension and not creak under heavy pedaling. Does
anybody have a numeric value?
