Deda zero 100, bolt torque?

joe.90

Right, so I bought a new tool today: a torque wrench. For obvious reasons.

On the zero 100 stem, it states that 8nm is max torque, (to steerer tube) so I calibrate the wrench to 7.5nm, go to tighten them up and the first bolt my new spangly toy touches it snaps!

The other bolts were all fine, only now I'm left with the task of having to drill and pick out a snapped titanium bolt from the thread my brand new stem :-(

Surely this can't be right? On reflection 8nm seems an awful lot for a stem. Considering the under saddle adjuster is the same torque...did I do something drastically wrong?

Mildly annoyed. :-)

rgliniany

probably just a dodgy bolt...

napoleond

I've had the same with titanium bolts, even with my torque wrench set to 4nm. Lost 2 stems that way. It's bloody hard drilling out Ti bolts!! Even with the torque wrench you need to caress the handle. Fitting a titanium bolt is a bit like making love to a beautiful woman, first grease her up, then line up with the hole, then gently screw away.

joe.90

what a great analogy napoleon! i will remember that!

keef66

I've read so many tales of woe featuring sheared Ti bolts that I'm determined to stick with steel. I'm not convinced the tiny weight saving is worth the potential hassle.

joe.90

im gonna agree with you there keef. these ti bolts came with the stem, im going to replace them with steel ones.

the weight saved is probably less than a sip of water taken out of your bottle!

also i will add, you can pick up a zero 100 stem with steel bolts for about £35, with ti bolts its about double the price! is it just the bolts that they are charging for?!

racingcondor

I wouldn't use more than 5 nm for anything on the stem. I'd also recommend keeping all bolts at a reasonable even torque i.e. tighten them both to a little past finger tight and then add a 1/2 turn to each bolt alternating between them.

The problem with putting the full force into a single bolt first is that you'll add a lot of pressure to one end of the clamp which will compress it into a V shape and put all the force on one side of the bolt head.

andyrr

I don't own a torque wrench but also don't recall in the recent'ish past (ie 10+ years) where I've snapped a bolt when tightening it. I'm absolutely sure I've done it at some point though with cycle/m'bike or car components.
For something like a stem bolt, especially where it is the smaller size (think they are generally 4 or 5mms ?) then I would go with only tightening it to the minimum required and instead of holding the end of a long 'L' shaped allen key to apply big leverage I try to maybe twirl up to initial tightness then hold nearer the bend as I apply the final tightening - might then hold the end to feel for any little extra to be applied but for smaller fasteners I do try to consciously not tighten, tighten, tighten and once at initial tightness I proceed more gently.
One reason to NOT have really tight bar and stem bolts I think is that in a crash it is better for these to allow a little slip as opposed to the bars/steerer being held so darn tight that more serious damage occurs. Obviously don't want them slipping in normal use but mega tight isn't the way to go for these items.

I remember reading a good few years ago that because various factors can influence the accurate tightening of a fastener (clean or greased threads etc) the ideal was to torque to an initial value then finalise with a degree tool - maybe a bit extreme but I think it helps explain why waiting for a wrench to 'click', even if it's set under the prescribed max value might not always give a safe end result and cycle parts could be relatively prone to snapping as they are often smaller than auto fasteners and you don't have to be very far wrong to go past what it can take.

http://www.extremetoolshack.com/2010/08/torquetoangle/

g00se

racingcondor wrote:

I wouldn't use more than 5 nm for anything on the stem. I

I was the same - old stem was 5 NM onto a carbon steerer. I replaced the stem with a Deda Zero 1 which said it was 9NM. I didn't want to do this so kept it to 5NM with loads of carbon paste but the headset would always work loose over a few rides.

Looking into it, the torque on the stem bolts is not directly related to the pressure on the steerer. It's the force needed to close the gap on the stem clamp. The Deda ones seem to need more torque to exert the same force as other stems on the steerer.

So if the manual says 8, go with 8.

napoleond

That's the problem! You go past 4-5 and the bolts snap...

giant_man

someone on this forum used stainless steel bolts instead of ti on deda stems I seem to recall, for this very reason ......

g00se

Yup - but I was referring to the OP's concern that 8nm could be too high for a steerer clamp.

giant_man

indeed, 8nm does sound high regardless, isn't this what the richey torque key is for? That limits you to 5nm, but you said you had problems with tightening a Zero 100 stem at 5nm.

This gets even stranger when you consider that with the new Zero 2 stem, Deda recommends a 6nm torque.

napoleond

I'm sure one of mine went at 4. Anyhoo, I complained a lot and got my money back...

Best just getting the normal Zero 100

g00se

These are the general Deda instructions.

http://www.dedaelementi.com/download/EN ... ooklet.pdf

If you go to their website, the stem in question should link to the specific instructions that come with the stem. The doc above seems to be the generic instructions for most of the alloy stems:

• Threadless stems (i.e. clamp on the exterior of the fork steerer tube) with M6 steel bolts: tightening torque 10 N/m.
• M5 steel bolts: tightening torque 8 N/m.
• M5 titanium bolts: tightening torque 8 N/m.

So I guess the lesson is get some stainless steel bolts