Roadies_Rok

I have encountered a problem with my Litespeed Arenberg road bike that if I can't find a fix may have me swapping out some parts which while not the end of the world and will in the final analysis make my bike better I would rather not spend the money right now if I don't have to.

I bought my Arenberg used from a guy off of OfferUp and am very happy with it but the parts are pretty much a hodge podge and I think a lot has been swapped out or replaced over the years. The stem is an ITM with a 25.8mm single bolt handlebar clamp and a 1 1/8" stem 2 bolt stem clamp. My bike did find last year and I got some good mileage in on it but when I took it out today for a 30 minute ride I noticed something felt off. When I got back to my Condo I was looking my bike over and I noticed that the handlebar has rotated down in the stem clamp which is what made my bike feel "off" to me. I grabbed my Park "Y" Allen tool and went to tighten the stem clamp bolt and it was seriously loose which it was not last year. The next thing I did was to get out my Newton-Meter torque wrench to see just how loose that bolt was.

I know with the newer stems with 4 bolts for the handlebar clamp the bolts are generally tightened to 4 NM each. With my 1 bolt stem I do not know the proper torque value so I had to guess. I started at 5 NM and when I put my weight on the brake hoods the bar rotated down. I then went to 6 NM and same thing. 7 NM the same thing. 8 NM the same thing. When I tightened the clamp bolt to 9 NM it held and the handlebar did not rotate downward but I am concerned that this may be too much. I really don't want to have a stem that doesn't hold he handlebar and it rotates downward while I am riding and I have to fight it all the way back not heaven forbid do I want the clamp to fail completely and I crash or have to call someone to come get me. Is 9 NM too much for that 1 bolt stem? Am I dancing in a mine field with this and do I need to think about replacing the bar and stem before a failure occurs? Thoughts and opinions are appreciated. Thanks.

Litespud

5nm might be appropriate for those little M4 or M5 screws in a modern stem. The single bolt takes way more than that. My old single bolt stems (Cinelli and 3T) used a 6mm Allen key, cranked about as hard as I could. I used such stems for decades before I ever owned a torque wrench, but based on what I know 5nm to be, I estimate that I used way more than 9nm to crank down a single-bolt stem

Geepig

I no longer own a torque wrench, so I have not paid attention to what torque is required. What I can say is that if you increased the torque in 1 NM increments until the bars stopped moving the chances are good that the bars will move out on the road as we can put a lot of force on the bars while riding.

The torque will depend on how clean the threads are, and for a used bike with a rotating handlebar the first thing I would do is take apart the stem, clean up the handlebars, stem, bolt and wedge of any corrosion and that greasy build up that often occurs around aluminium parts.

dsbrantjr

Also check that the gap on your bar clamp is not closing fully; if there is no gap you will just be clamping the clamp against itself rather than against the bar. If there is no gap the clamp is too large for the bar and will need to be replaced or shimmed.

imakecircles

You can search for 'carbon assembly paste' which is like grease, except that it will have a very fine grit in it, that is meant to hold parts that could slip in place. It can be used on parts that aren't carbon. I've had good luck with the Park Tools version of this product.

ARider2

I prefer a handlebar clamp with at least 2 bolts and 4 is even better. If I had a 1 bolt handlebar clamp and I was unsure whether the stem or handlebars had been replaced I would replace the stem with one with a 2 bolt design. If I found the existing stem and handlebars of good quality and in good condition I might proceed as you did but not knowing the correct torque specs or history of the items would push me towards replacement.

Andrew R Stewart 

Small fasteners want low torque values. Bigger fasteners want more. How big is the stem/bars clamp's bolt?

Clamping bolt torque is about a couple of aspects. One is that the fastener/bolt will more easily strip out the threads when the threads are of a fine pitch (and thus also shallow depth), smaller hardware usually have finer threads. The other big reason is to control the max clamping pressure that the part places on the trapped part (the stem's clamp bearing down of the bars). Parts that are made from materials and designs that don't handle high compression forces (think carbon parts) need some reinforcement (as in a compression plug in the steerer), more surface area within the clamp (bigger bar diameters) or application of an assembly compound (carbon paste).

Not knowing more details means we don't really yet know all the issues at play and thus can't give the best advice first (unless we get lucky at our conjectures).

The last bit I'll mention is that the stated bolt torques that so many feel are the WORD are the max torque the parts are designed to handle. The working torques can be less then the max if the parts stay in place at a lower then stated torque then the lower torque is a correct tightness level (note that I didn't say "the" correct one). Andy

oldbobcat

I presume by one-bolt you mean two bolts, one on the top of the face plate and one on the bottom. 4 Nm isn't going to cut it. if you're using this stem you are presumably using an alloy bar. Use firm hand tightness, and be sure the gap between the plate and the stem is even from top to bottom. As you tighten, maintain even gap by alternately tightening top and bottom bolts.

Roadies_Rok

oldbobcat No, actually I mean 1 bolt on the handlebar clamp. This stem and probably the handlebars are old. The stem is a single bolt (it has 2 bolts that secure the stem to the steerer tube) and it is an ITM Eclipse stem. The stem was made before ITM went bankrupt and their name was bought out by another company. I have the handlebar clamp bolt set to 8Nm and I have ridden my bike twice and it is not slipping so I think I am good for now.

Iride01 

When the bolt is tightened up on the bar clamp, is the gap fully closed? If so, that will definitely be a problem.

Also, if the bolt is a shoulder bolt or has a shank with no threads on it, then you might be bottoming the threads out even if there is a gap.