hamster

I'm looking for a new stem to improve fit. (I currently have a 100 mm stem and I want to try 80 mm.) My carbon bike is already north of 18 lbs with pedals so the last thing I want is to add even more weight. I found a decent deal on a "3T ARX Pro" stem in 80 mm size. According to the online description, the primary difference between Pro and Team is that "The ARX Pro uses a steel bolt package instead of the Team's titanium bolts. This results in a net weight difference of 30g, with the ARX Pro weighing in at 150g." I see Pro available for $35 and the best deal on 80 mm Team that I could find is $82.

My current stem weighs 100 g and it has 6 bolts (M5x17 mm, I think) weighing 22 g total.

* Do I have titanium bolts already?
* Is it really possible for steel bolts to weigh more than twice as much as titanium bolts?
* Are these bolts generally interchangeable - can I expect to reuse my bolts with the new stem?

Nagrom_

50 dollars for a 20 gram cut is about the worst you can do for $/g.

But to answer your questions:
1. How would we know? You haven't even said what stem it is.
2. Yes. Science.
3. Most are M5's.

rpenmanparker 

You can buy the titanium bolts for $10.00 or less from China with free shipping on ebay. I have done that recently and was completely satisfied. Often the set will include a top cap bolt for your head set. That makes the $/g calculus much more attractive.

merlinextraligh

First, putting your bike on a diet is a really expensive proposition.

Second, if your CF bike weighs over 18lbs, there have to be way better weight reduction targets than the stem.

Third, I doubt your current stem weighs 100 grams. That's friggin light for a stem, and would not be expected on an 18lb bike.

hamster

I am definitely not buying the Team version. It's Pro or I'll be looking at other manufacturers. I'm mainly just confused by the claim that using chromoly vs. titanium can account for this much of the difference.

I quoted the weight. Is 22 g for 6 M5x17 bolts more typical of steel or titanium? My stem came stock with the bike, all it says is "Cannondale C2".

Like I said, the goal is to improve fit, not to reduce weight. But I don't want to increase weight at the same time.

Stem body is 86 g, clamps are 16 g, and bolts are 22 g. The bike was originally around 16.5, but it got there after a 32T cassette, pedals and a powermeter hub with a basic alloy rim.

rpenmanparker 

I agree. The FSA OS-99 is about as light as you can get and is more that that (in reality).

merlinextraligh

The weight savings from the bolts is about 9 grams. But you can do better than $50

https://www.uberbikecomponents.com/vi...--Raw-Polished

Still about $2 /gram

merlinextraligh

that would be a typical weight for steel. Listed weights for Ti appear around 9-11 grams,and Ti is 50% lighter.

Angelo19

I just changed stems, from a bontrager 100mm to an 3t pro 90mm, saved all of 9 grams. IIRC, the 3t was 130, I may be wrong though.

rpenmanparker 

Steel weighs between 3.5 and 4.0 g, so 22 g for 6 is steel.

rpenmanparker 

I feel that 1 $/g is fair. If you pay $10 for the bolts (the Chinese source I quoted above) you are right there.

caloso

Of all the places to shave grams do you think that part that connects your bars to the bike is the best place to do it?

Nagrom_

Well a bit of math can help. These will be low estimates because they don't factor in the bolt heads. I bet the steel bolt heads weigh about a gram, and the Ti heads weigh about .56g. 5x17 cylinder would have a volume of about .334cm cubed. Density of Ti is about 4.5g/cm cubed, steel is 7.9g/cm cubed. One of the steel bolts would weigh ~2.64g, not counting the bolt head. A Ti bolt would be about, 1.5g head not included.

6 steel bolts would weigh 15.9g, 6 Ti bolts would weigh 9g.

Add in my guess for the heads, and you have 21.9g for 6 steel bolts and 12.4g for 6 Ti bolts.



You have steel bolts.

hamster

That's very reasonable.

I've just discovered that I can get a stem that's identical to mine but in 85mm on ebay for $40 including shipping, and that's the route I'm going to take.

merlinextraligh

I like Ti stem bolts, not because of the weight savings, but because they don't rust, like steel does in a coastal environment.

And with the torque needed at 5nm or less, there's not a strength issue.

thechemist

I will also add that I think 80mm stem will really effect the handling of the bike in a poor manner. I would adjust your fit elsewhere first if you can.

caloso

Oh, good point. Now that I think about it, I always have rust in my headset bolt, probably because it's perfectly situated to catch sweat.

rpenmanparker 

A good hardware store will have the necessary bolts in stainless steel for about a buck apiece if you like.

Elvo

If you need an 80 mm stem, your bike is probably too big. Buy the next smaller frame and enjoy the 25-50 gram weight savings.

hamster

I don't see why this would be the case. The bike is slightly larger than ideal for my size. I've been using it with the stock stem, I'm generally pleased with the fit (I put over 1000 miles on it just in the last 1.5 months) but I frequently find myself holding the hoods a bit too far back. Losing 20 mm off the stem would move the hoods to the spot where my hands are most of the time anyway.

Sure, as long as you give me $1000 to compensate for the difference in the resale value of my current bike and the market price of a new bike in the next smaller frame size.

thechemist

Is your stem flipped up and to what degree? With a 80mm stem you have a very short twitchy handlebar that will move quickly with the slightest pull. It will certainly affect your handling it will just be a matter of whether you notice it or not.

zvez

do you guys use anti-seize with ti bolt usage? Ti's popular on motorcycles and you absolutely have to use when ti will come in contact with other metals to prevent corrosion.

rpenmanparker 

To the best of my (chemical) knowledge Ti neither corrodes under normal conditions no induces sacrificial corrosion in other metals due to a very robust oxide film. Perhaps there is a galling and even seizing problem with Ti due to the interaction of this film with other metals, but I have never experienced it.