Geosammy

Hi all,

It's been a while since my last post and a lot has happened to me over that time.
I did purchase myself a new ride a few years ago and had my second Thomson stem added to this bike. I like there products, but this is the 2nd time I've had a Thomson stem failure. This stem as well as the last one both developed a crack. I'm very disappointed and will be calling them to let them know and hopefully get the cracked part replaced. My warranty offered by Thomson has unfortunately expired, so I afraid I'll have to buy the part and or new steam outright.
Here's 2 photos of what and where this stem has failed.


Should I just replace the entire stem, or do you think if I replace the part that I'll be okay?
Also, could anyone recommend/suggest a decent stem I might use as a replacement?

BTW... sorry for the crappy photos, it's the only camera I own at the moment.

Andrew R Stewart 

I sure hope Thomson takes care of you. The only reason I can think they would balk is if you didn't tighten to torque spec. This type of failure is fairly uncommon although I have seen it on a variety of brands over the years. Andy.

Geosammy

I hope so too Andrew.
I did follow the instructions to the letter, but that was more then 3 years ago, ie. Handlebar Clamp Bolts: 48 in-lb.
Only after my monthly cleaning and checks did I notice this crack. So I've been riding with it for at least 3 weeks or more.

Could the mounting bolts on the handlebar clap worked there way lose after more then 3 years of moderate use to cause this failure?

FBinNY 

I assume the crack is in the top plate, and if so, Thomson has a long history of honoring guaranties based on the physical facts and not hiding behind the terms. Call or email them and odds are they'll send a new plate at no charge, though they may insist you send the broken one back first.

As for the cause. IMO many of these are from mismatched bar ODs which is a tolerance issue and can create intense local stress on the ends of the plate. That may be coupled with over tightening to prevent slippage, especially on CF bars that don't have a traction coating in the clamp area.

Also, regardless of any other factor, consider the problems involved in tightening any 4 bolt stem clamp. There's a big difference between torque and position, so even if using proper torque, it's easy to introduce twisting or local stess on the clamp plate. The issue is analogous to a table with for uneven leg. Simply using a torque spec doesn't prevent the issue. You need good methodology. One technique is to tighten each of the bolts "touch tight" by hand feel, so the plate is making even contact top/bottom and side/side (especially diagonally). Then torque can be added by degrees, working each bolt in sequence. Unlike tightening a car wheel, you don't do a diagonal since that's how youn twist the plate.

One way is to tighten top, then bottom on the same side, then top/bottom on the other. My prefered technique is a bit different, and designed to eliminate any twisting. I tighten both top bolts touch tight to establish the length, then back each off a counted number of turns to get an even gap at the top. I then leave those alone and do the tightening at the bottom, to preserve the uniform gaps at the top and bottom. I also reduce the needed clamping force by using a traction compound on the clamping surfaces so I get good hold without stressing the parts.

BoJaffa

I had the same issue on my Thompson stem.. The face plate cracked. I ordered another one and it's been fine since. I haven't had this happen on any other stem I've owned. It's certainly disappointing.

Geosammy

That's good advice, thanks FB.

Geosammy

Yes I agree BoJaffa, very disappointing indeed.

FBinNY 

BTW- I have a few face plates left over from my days as a Thomson distributor. I'm not sure which diameters and colors are left, but if Thomson doesn't come through for you, send me a PM saying which you need and I'll check my stock.

Geosammy

Is that so!?
Thanks for the offer FB.
I'll take you up on that. I'm going to give them a call tomorrow, so I'll know what's up soon enough.

jimc101

Having a cracked face plate is all part of the experience of owning a Thomson stem, it's almost a consumable item, the good thing about it, is that although they crack, you still have 3 bolts holding the face plate on, and they are very cheap to replace, with OEM replacements.

Given you have a 25.4mm stem, that's going to be several years old now, as they haven't been made for a few years in that size, but faceplates are still available on the Thomson site at $9.95

lopek77

The problem may be not with out of warranty item, but with an unsafe item, which may be factory defected/bad design.
I wouldn't choose same stem again, even if someone was paying me to take it.

Cracked Thomson Stem- Mtbr.com
https://forums.thepaceline.net/printt...?t=47780&pp=40

and also this, but as far as we know, there are very few truly counterfeit goods on the market...Many of the past counterfeit goods made in USA for example, was copied and made in Asia. Now we mostly deal with grey market goods, goods made by the same factory which makes original item, but it's not authorized/guarantee/warranted by the company which gave that order. Who knows....but it's always a possibility.
https://www.bikerumor.com/2012/03/13/...terfeit-parts/

Seconds and thirds are also a real issue, and they sometimes make to the distribution channels. Many of them end up on Ebay and other not authorized online dealers.

Geosammy

No doubt... and yes it is a 25.4mm stem. It's an SM-E111-BK, 5°x90x25.4mm, Elite Stem Black.

Geosammy

Wow, that's pretty interesting and disheartening at the same time.
This is the second time I've had a a failure with the same stem, but the former stem became cracked at the stem body.
Any suggestions on a replacement stem?

jimc101

Personally, would just get a replacement faceplate.

The biggest issue you have, is the 25.4mm handlebars, as very few high end stems are made in this size anymore (if any), your be looking for NOS/2nd hand options if you want to keep the bars.

I have 3 Thomson Elite X4 stems, 2 were bought 2nd hand, and one came with a cracked face place, I was aware of this, and replaced with a dress up kit, it it fails again, will look at the carbon fiber face place one Thomson start shipping out of the US.

lopek77

Different brand for sure. The failure may be because of Thomson deffects, or because of your riding style, or possibly even something else. Choose something based on strength instead of weight. I never broke stem, and I ride a lot, abuse my bikes - aka having fun, and I'm a pretty big guy. Broke frames, wheels, cranks, seatposts, chains, pedals, but never stem, and stem carry a lot of weight and forces, especially in mtb applications...

lopek77

Yes, this size is not a common anymore, but there are still a plenty of stems to choose from, and many for dirty cheap. The issue would be the color/brand/angle/length.
Upgrading handlebar and stem to 31.8 may be another option.

Geosammy

I'm going to give Thomsom one last try. If I can get the correct face plate to replace the cracked one, that would be great. If not... then I have to abandon Thomson for another brand of stem.
I don't do hard riding. I only use my bike to run errands and get myself from point A to point B. I also don't ride for fun and recreation.

FBinNY 

One of the interesting things about the reports of face plate failures of Thomson stems is that many report multiple failures, while the vast bulk of users report no failures. If the issue were poor design or other product defect, one would expect more even distribution, with few, if any seeing multiple failures.

I see similar patterns of some suffering multiple failures while most suffer none on many products. Of course this doesn't prove anything, but if 1 out of 1,000 parts are bad, the odds of a single individual seeing 2 are fairly slim and 3 even slimmer yet.

Most failure analysts look at this kind of uneven distribution as a reason to look for other common denominators. It doesn't have to be the individual or user error, it could be the type or brand of handlebar or rider weight, or whatever that would cause a deviation from the normal random distribution.

If stem failure were cancer, a cluster in a community would have experts looking for common denominators like the water supply, air quality, demographics, etc. Same applies to mechanical failures. One is a fluke, 2 of the same rare failure calls for a closer look.

BTW- what's a rare or common failure can be hard to determine from reports because we only hear about the failures, and don't know the base number of units in service, but the manufacturer does.

IMO- the Thomson stems are fine, as compared to other lightweight stems. That doesn't mean that there aren't stronger albeit heavier stems to choose from, but you have to compare apples to apples and oranges to oranges.

Geosammy

Thanks for this advice and I'll defiantly conciser all that you've mentioned.

Geosammy

All good point FB. I'll give Thomson a call and see where it takes me from there.
Thanks.

79pmooney

If you choose to go with an new stem and you like your present 25.4 bars, be aware that you can get a 31.8 stem and use a shim with the smaller bars. The framebuilder who has made me a number of stems will only do 31.8 for threadless. (TiCycles) I am using his shim with an old style Nitto bar. And it makes changing to the new standard really easy.

Ben

Geosammy

If I do go with a larger handlebar, I'll need to shim everything else to fit. I wouldn't mind going a bit larger, but I really don't want to have to shim everything to fit.
Hopefully Thomson will come through for me and I'll be able to get the face plate I need.
We shall see...

FBinNY 

No, changing the bars and stem wouldn't be cause for changing anything else (except maybe for an accessory you clamp very close to the stem.

The only thing that changes on mtn or road bars is the clamp diameter, the rest of the bar remains standard, ie. 7/8" for mtn and most upright bars, and 15/16" for drop road bars, and some specialty bars made to fit road brake levers.

So, you could buy a modern 31.8" stem, and shim for your 1" bar, or you could replace both without changing anything else.

Geosammy

That's good to know. My knowledge isn't as great as I would like it to be and things seem to be changing all the time. Which makes it difficult to keep up with. Although some things have never changed.
From the sound of what I was reading, I was afraid I would need to shim everything that's attached to the bar.

lopek77

Many young mechanics often complain that there is no such a thing like standard when it comes to bikes. I guess it's the common pain of every fast growing industry, full of new , never ending designs and ideas.
It would be so much easier and cheaper if we all were riding Flying Pigeons