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Thomson stem with Carbon Fiber Steerer a No-No?(14 posts)

Thomson stem with Carbon Fiber Steerer a No-No?Me Dot Org
Sep 20, 2001 3:29 PM
A few days ago I got a (mail order) bike with a Reynolds Ouzo Pro fork and a Thomson road stem. I'm still in the shakedown phase, and I went to LBS to get the wheels trued.

While I was there the shop owner noticed the Reynolds fork and Thomson Stem combo and said that Reynolds literature said that the Thomson-type stem(internal clamp) could be very dangerous with a carbon fiber steerer.

Since I don't have the Reynolds literature, and they don't seem to have literature on line, can anybody suggest whether I should get another type of stem? If so, what type?
Not sure...Cliff Oates
Sep 20, 2001 4:22 PM
According to the Thomson stem FAQ, the stem is OK with CF steerers. You might want to send email to Reynolds Composites or call them at 760-798-8008 and et them to verify this. If they say no, and you're attached to your bar choice which, like the Thomson stem, should use a 26.0mm bar diameter, then you probably ought to be looking at Deda for a stem.
Thanks for the feedbackMe Dot Org
Sep 20, 2001 6:45 PM
Read the Thomson FAQ - I'll email Reynolds....
re: Thomson stem with Carbon Fiber Steerer a No-No?Birddog
Sep 20, 2001 6:48 PM
I don't know about the Thompson, but I can vouch for the Ritchey WCS that I just put on my new Ouzo last week.
There's only one solution...Leisure
Sep 21, 2001 2:04 AM
...get another stem, and then mail me the Thomson. :-) More seriously, I would be careful about using the Thomson. The clamp is off-center from the steerer tube, and the edge of it pinches into the tube. According to Thomson, it could clamp more than adequately if you left one of the two bolts out. And then you tighten each bolt one at a time putting tremendous clamping force on the thing. Ingenious really, but it would be very easy to overwhelm a carbon fiber tube.
Take your stem off the steerer right now and inspect the carbon fiber for strain and scuffing, noting how tightly the stem bolts were installed in the first place. Strain in carbon fiber is usually visible as a yellow discoloration. If the thing looks just plain nasty around its whole diameter, a new stem won't matter because you're fork's already ruined.
My figuring (speculation, postulation, blatantly irresponsible off-hand guess) is that even if it looks okay and the companies say it's fine (or they say it's not but you keep it anyway because heck those Thomsons are gorgeous-handsome chunks of metal after all), then apply very little torque on the bolts when putting the thing on. I'm talking one finger's full force or two fingers' firm force about one inch apart from the thumb on the tool back and forth on each bolt until the stem is just secure to the tube. The stem in this situation can still be turned off-center from the fork with some force, but it will be solid enough for most non-abusive road riding. Do you notice the same torque applied to most other stems will not clamp nearly as well? I'm not sure about carbon, but that's what I've observed with the aluminum 1-1/8" steerer tube on my mtb.
But you know, my road bike would look really swank next to my mtb if it had a matching Thomson. And I know you're really just looking for some excuse to get one of those mega-swell-gootchie $200 Italian stems, aren't you? Please post what you find out, I'm interested.
Not Sogrzy
Sep 21, 2001 9:58 AM
I had the same question. Actaully addressed this question to the Thomson guy at the Sea Otter. He said that it's actually approved by Reynolds b/c the mechanism is two shaped halfrounds that grab the carbon steerer, not the wedge type that the instructions that come with the fork caution you against. If you want to hear it from the horses mouth why don't you drop the Reynolds folks an email? They will confirm.
UPDATEMe Dot Org
Sep 21, 2001 4:23 PM
Dropped an email to Carl Strong (My framemaker) and also to Reynolds.

Carl said that he spoke with Reynolds today and they said that the Thomson is fine.

I haven't received an answer to my email yet.
do not use the Thompson with carbon steerersB1
Sep 22, 2001 10:17 AM
The Thompson has a internal clamp which puts pressure at a localized area of the steerer.
I dont know why anyone would want to use a Thompson stem on a road bike anyway, that has to be the ugliest road stem ever!
Ah, Contraire!grzy
Sep 24, 2001 3:14 PM
Mutant is THE ugliest road stem ever.

Clamp on the Thomson is actaully designed with a carbon fork in mind. The key is that it distrubutes the load over a wide enough area. Don't take my word for it - there's also what the folks at Reynolds say - it's OK.
Thomson sez Reynolds sez it's OkayMe Dot Org
Sep 24, 2001 4:01 PM
Received the following email from Thomson after inquiring as to whether or not it wasy okay to use their stem with a Reynolds fork"

Me Dot Org,

We personally spoke to Mike Lopez at Reynolds and he told us it was fine to
use the Thomson stem with Reynolds products. Our clamping system actually
surrounds your steerer tube more than 180 degrees so that it does not crimp
the steerer. There were some other stems on the market that did not cover
as much surface area that conflicted with carbon steerers, but the Thomson
stem should be OK. Please let me know if you have any questions.

Thanks,

Alexis

At 09:11 AM 9/21/01 -0700, you wrote:
>First of all, this stem is absolutely gorgeous and appears to be rock solid.
>
>Yes, yes, I've read the FAQ. "The Thomson stem has been approved by carbon
>fiber fork manufacturers for use on their carbon fiber steerer tubes."
>
>However, my Reynolds Ouzo Pro says that you shouldn't use stems with
>"internal clamping devices".
>
>Has your stem been approved for use specifically with Reynolds carbon
>steerers?
>
>Thanks,
>

-----------------------------------
Alexis A. Smith
L. H. Thomson Co., Inc.
7800 NE Industrial Blvd.
Macon, GA 31297
phone: 478-788-5052
fax: 478-788-1956
email: asmith@lhthomson.com
url: http://www.lhthomson.com
Echogrzy
Sep 25, 2001 9:21 AM
Ahhh, isn't that what I said a couple days ago?
Echo EchoMe Dot Org
Sep 25, 2001 9:17 PM
Yes it is, grzy, and I didn't doubt you for a moment. I just wanted to post a direct quote from Thomson.

By the way I got an email from Steve Santel at Reynolds, stating "the Thomson stem is the only compression style stem that is carbon compatible."

I guess this issue is dead and buried.
Dead and buried!Leisure
Sep 26, 2001 3:28 AM
Darn, I guess I can't have your stem after all.
Yeah, if even Reynolds is okay with it you can be pretty confident; if you like to be neurotically careful like me make sure the thing doesn't have ridiculous torque on the bolts anyway, just to be extra sure. Otherwise, I'd say I'm glad I was wrong.
Payoffgrzy
Sep 26, 2001 1:04 PM
It *pays* to be safe.

I was wigging out about the Thomson stem until I too asked questions. They must get aksed this frequently, just based on the responses here and their own FAQ