Grinding Away Part Of A Stem?
 

I have a question. Before asking it, I must prepare myself for the torrent of abuse and mockery that I anticipate. Deep breath. Okay. I'm ready.

Question: I want to slam this stem all the way down. I mean, with the horizontal part of the stem riding on the headset lock nut. But the larger radius where the vertical and horizontal parts meet prevents that. I am contemplating taking a grinder and cutting away that radius, then smoothing and repolishing the affected area. My theory is that the stem has enough material - they are solid, aren't they? - to not asplode.

Thoughts? Abuse? Mockery?



http://i800.photobucket.com/albums/y...psttfzup1q.jpg

Google "stress riser".

i sure as hell wouldnt do that. may i ask why?
maybe getting a steeper angle stem if your objective is lowering the handlebars...

I predict it will break on your very first ride.

I have had a stem break while riding. It happens when you are stressing the bars - the worst possible time. It might be when accelerating in traffic, or in a tight turn or whenever you least expect it. With aluminum, it happens fast, too, without warning, not like steel that tends to give before breaking.

There are very few cycling experiences which can match the excitement of being on your bike, riding hard and have the handlebars detach from the frame.

Get a proper set of bars to give you the ergonomics you want. If you can't afford that, wait and save your money.

All my stems back in the day had real nicks from riding them slammed. None broke. (Nitto, TTT and Cinelli) I raced at <150 pounds and am a slow twitch, no sprint guy who loves to climb out of the saddle.


Not saying this is a good idea. But if you are like me and you know that stem's history and miles (and you grind and polish professionally) you are probably safe. The re-polished area will look different since you have removed the anodizing.

Finding a track stem that fits your needs would be a better and safer approach. But in answer to multivac, I completely get "why". Some of us never feel we have enough reach. Smaller frame for more drop? Bars too close. Larger frame for more reach? Bars too high. More stem, more slam, please.

There are 135 Cinelli traditional stems. I have one on one of my bikes. There is also the Nitto Pearle. The "13" is a real 140. I have one of those also (and it is a nicer stem than the Cinelli - better machined and more accurate).

Ben

http://bikeforums.net/attachment.php...hmentid=457249 +1

Back in the 70's I had 2 stems break while riding... Both were at the bottom, at the expander split:

http://bikeforums.net/attachment.php...hmentid=457250 http://bikeforums.net/attachment.php...hmentid=457251

The stems that broke were cast aluminum while Cinelli stems are forged aluminum. I was fortunate that I was able to bring both the bikes to safe stops. :eek:

Cinelli introduced the 1A forged aluminum stems in 1963 so, theoretically the OP's stem can be up to 50 years old. Most likely it's at least 35 years old! What's the history of the stem? A stem that long is going to have more stress at the bend than a shorter stem!

Aluminum can fatigue at a much faster rate than steel. Frequently when an aluminum component fails, there's no warning - it goes catastrophically!

I used this Cinelli 1A stem for almost 35 years.

http://bikeforums.net/attachment.php...hmentid=457252

Here's a brand new premium quality stem. I saw what looked like a scratch and examined it with a 15x magnifier. I discovered cracks under the bend - where the OP want's to remove metal!

http://bikeforums.net/attachment.php...hmentid=457253 http://bikeforums.net/attachment.php...hmentid=457254 http://bikeforums.net/attachment.php...hmentid=457255

Most people wouldn't have noticed the cracks!

Lastly, WHY? For comfort? Looks? ????

http://bikeforums.net/attachment.php...hmentid=457256

verktyg :50:

Chas.

In your last sentence, you ask if the stem is solid. It isn't. That's why your stem will break if you go ahead with your plan.

Well, a couple points...

To answer one question, the horizontal part of the stem is solid, but the (approx.) vertical part is hollow, having the bolt go through it.

Ignoring all the good advice already given, if you do decide to modify your stem, do not grind it. Any kind of grindstone is just going to get full of aluminum particles that are pretty impossible to remove. The correct tools are files, and you need to keep them clean, because files also get full of aluminum particles that are hard (but not impossible) to remove. Start with a good mill file, then move to a fine-tooth b@st@rd file, round the curve with a rat tail file, and finish with fine sandpaper.

Finally, there are stems that you can slam all the way down, or that get the handlebar lower by various other means. Given that modifying your existing stem will take a lot of time and will certainly cause safety concerns, you're probably better off just getting another stem.

Followed by "stress fracture"

This seems like a REALLY bad idea! Stems (along with other parts) are designed to certain tolerances and to withstand certain pressures, etc. When you start modifying, you often, as in this case, weaken the part. A weak stem, to me, seems like...as I said...a REALLY bad idea!

Did I mention that, to me, this is a REALLY bad idea?

Followed by "hospital"

+1

How much are teeth worth to people?

I personally wouldn't mess with this folks.

Which is not to say they're always up to the task.

https://lh5.googleusercontent.com/xH...M=w655-h873-no

Not to digress, but that's a very nice kitchen to be a bike kitchen. :D

There's a reason that there is a bit of 'extra' material at the bend (it's not really extra, but what is needed to prevent catastrophic failures. That area sees a lot of torsion and bending stress, and the length magnifies). Steeper angle stem and some bars with a deeper drop will be better for your longevity and health. Nice bike.

It's the dining room. My wife has stopped objecting to bikes in the house, so long as they aren't dirty or there aren't guests coming. So that bike lives in the house, usually the living room, and my son often parks his bike in the dining room.

Back to the stem. I'm thinking that quill stems get milled and pantographed, without much fuss, despite the removal of material and sharp corners created. Converting that large radius curve to a smaller but still smooth radius might remove 1/8" of material. That is a pretty small portion of the total dimension (front to back) of the stem. I need to check but I think the stem at that location is almost entirely solid, penetrated just by the small diameter bolt hole instead of the larger diameter expander hole.

Of course, I could find a headset with a lower stack.

Or a different stem, but a month or so of searching for an attractive, light, affordable, 140 mm "track" stem hasn't turned up anything nice.

Or deeper drop bars. The 3ttt bars on there now are, I'd say, about medium drop.

Material removal is like real estate - location, location, location.

I strongly advise against removing material at the bend. If you haven't found a stem yet, search for some bars as well. The bars won't help get your position lower anywhere other than in the drops, but you'll get to keep your teeth and your pretty bike. :)

Pantograhs are (should be) flesh wounds in low-stress areas of the stem surface. Removing material from the junction between quill and length (extension?) is removing material from the 'bones' of the stem. 'Tis not only a flesh wound.

-MSEng

I am sure the designers of the stem took every effort to remove as much material as possible without jeopardizing the liability issues of use. I wouldn't mess with that. Is there a safety margin in the design you could reduce? Sure, at your own risk.

If you know a practicing mechanical engineer who does stress analysis and has extra time, ask him to do a FEA on the design. he will ask about fixed locations and forces. That would be the hard part but even if they are in a reasonable range, you will get an idea of where the weak and strong areas of the stem are.

There is a reason that 1" Headsets have moved to 1 1/8 or larger and that stems have been designed with larger diameters and more contact area. I just would not second guess the designers of any of them without accepting the risk of the consequences entirely (no insurance for backup should be considered).

Two other thoughts:

-It might not help much, but if you get a replacement stem with a significantly steeper angle (track vs road), you may need a bit less stem length to keep the saddle-to-bars dimension the same. If you can find a workable 135mm cheap enough it may be worth trying. Sell it if too short.
-Removing ~1/8" of material at the bend should be compared against the bend radius, not the stem length. ~1/8" removed from a ~1/2" radius = ~25%. That's a lot.

Yes, you might luck out and be okay, but...

Find a stem with a different angle.

+1. Why risk it when track stems are readily available?

http://www.businesscycles.com/graphics/tstem-all.JPG

This reads like a job for a Cinelli 2a stem.

Think Trek at the Paris-Roubaix. ( I know different style of assembly, but I am conservative. )

Find a headset with a shorter stack height.

I was riding with my neighbor a couple weeks ago. He is more than 10 years younger than me and has that common hamster-on-a-wheel excess energy you find in young adult males. I think he was trying to make a point by dropping me, then he could be magnamonious and slow down to let me catch up. He is most definitely a stronger rider than me, but I have more experience hanging in the draft of a faster rider so he wasn't able to drop me. He would accelerate up to ~45 or 50 km/h and maintain that for a few seconds, before easing off, sitting up and looking back with a self-satisfied smirk, assuming he had lost me. But I was right on his wheel every time.
About a quarter way through our planned ride, he attacks again. My strava indicates that we were up to 39 km/h, he was leaned way out over the bars trying to stay aero when his stem snapped, I slammed on my brakes and narrowly avoided riding over him as he slid face first off the road and into the ditch.
Then another older cyclist we know who was trying to chase us down caught up with us, a lady from a nearby farm was driving by and stopped her truck and drove my young friend to the hospital, and I continued my (now much more relaxed pace) ride with the fellow who had caught up with us.

This experience taught me two things -
1. Experience counts for a lot. My friend can ride a lot faster and longer than I can, but I was still the better cyclist. He couldn't drop me, and he couldn't finish the ride.
2. Don't mess around with a stem of questionable condition. The stakes are high and there is no chance to recover once failure occurs.

It looks like turning your bars down parallel to the top tube would drop the hooks and hoods as much as bringing the stem down a half inch.

Or you could bend your elbows when you need to get flat.

Or as others have if use a track stem, or chome-moly stem that can be inserted further.

[MENTION=63590]jyl[/MENTION] - I will plan to attend your funeral.

Seriously. Don't do it.