Re-cutting/Boring out a stem! Is this possible ??

[originalshinkicker]

Yep, worked on lots of bikes over the years that have issues with these stems. You also have pro teams of the era that would rather use a Cinelli 1A stem (external clamp) rather than a 1R (internal clamp).

Anyway, the 2 points I made are important. The inside front of that stem is serrated for grip - removing that to enlarge the diameter will cause an issue. The wedge will also not fit against the bars correctly and cause pressure and lack of grip.

Really bad idea to try this.

 

[Ian Raleigh]

Wouldn't it be easier to just find a new set of bars?

The bars are worth in the region of £300 so I'm not ditching them.

If you enlarge the inner diameter with any kind of file/drill/reamer all you will end up doing is removing the serrated surface on the inside of the front of the stem that provides grip

Been advised to use needle files to put in new lines.

You will also still have an internal wedge that fits a 25.4 so the wedge will not have full surface contact with the bars. The edges of the wedge will contact the bars and not the middle. That will put stress on the bars at those 2 points.

The original stem is 26mm which I still have so can use the steel wedge out of that and fit into the new stem.

 

[originalshinkicker]

Must be a nice set of bars for £300?

I wouldn't risk it. I wouldn't like to be out the saddle, climbing, heaving on the tops of the lever hoods knowing that the fit between bars and stem has been "manufactured". I would value my smile and my bars too much ;-)

 

[curyam]

Just curious, what bars are worth £300. I'll have to go through the bars in my parts bin.

 

[Ian Raleigh]

The bars are Shimano Dura Ace AX, typical average selling price on fleabay is lets say very high.

http://www.ebay.com/itm/NOS-Shimano-Dur ... 4859648acc

I'll take the stems to a decent engineer first and see what they think.

 

[TGR]

Ian,

I had missed this!

You should point out that the ebay link bars have the end plugs too!! LOL Good price.

Oh, you know my views on this.

Richard

 

[Ian Raleigh]

Shimano bar end plugs sell from anything from £30 to £50!! I have a set on the bars too :?

Madness!!!

 

[HawkMA750]

http://www.ebay.com/itm/New-11-Piece-Ad ... 41732e54a4 this is insane cheap... at least usually u pay half for one of the near 1" reamers.

I widened already 3 or 4 stems that I ride daily. I have not one sliding in the clamp. Break the sharp edges after reaming (this is a file job). Filing by hand I fear will not be very precise.

 

[Ian Raleigh]

Lets see what the Engineers say this coming monday and I'll report back!

The company is excellent and does modding in the aircraft industry so they know their thing.

 

[torqueless]

HawkMA750, Reamers produce conical holes, not cylindrical ones. Maybe infinitesimaly conical in the case of those reamers you linked to, but conical nonetheless. That hardly matters in sheet-metal, but if you are reaming through over an inch of bar-clamp, do you not end up with a hole of slightly larger diameter at one end than the other?

A good file is probably less than a fiver- I don't know, I haven't needed to buy one for a long time. Of course, the file is only as accurate as the filer. I admit I am prejudiced against power tools, things can go wrong/too far- very quickly, everything screams and vibrates....

I'm unconvinced that those 'serrations' actually resist torque, more like built-in stress-risers, but I guess Shimano (unlike me) have done some scientific tests, or so they would like us to believe.

Anyway Ian, don't take my advice, I don't want the blame for anything that might happen to £300 worth of handlebar as a result of following it!