Handle bars compromised ?

[brucelee]

Hi,
I have just snapped (another) stem (KF angle adjustable two bolt clamp) and
during my research realised I was using 26mm bars (Deda Piega, aluminium)
with what is probably a 25.4mm clamp. My question is, will the bars now be
compromised by having been crushed by the incorrectly sized clamp ? The bars
are about 4 yrs old, stem about 3.

Also just sent this email to St John ST cycles, anybody got any additional comments - I know the quill to ahead issue comes up quite alot but I need I need alot of height and reach :

Hi,
I recently snapped the stem on my Dalesman. It was a KF adjustable stem 1” threaded steerer, height 110mm (top of headset to centre of angle adjuster) reach 110mm (centre angle adjuster to centre handlebars) with and angle of 5 or 10 degrees up. I think the KF is a MTB stem designed for 25.4mm bars but 26mm deda bars were fitted. The KF stem was of a two bolt clamp design. I am assuming this mismatch will have compromised the safety of the bars and in light of that I was considering the following products to replace bars and stem and have some questions about them :

http://www.sjscycles.co.uk/ram-1-1-8-ah ... prod24376/ stem
I can’t find any references to these on the web, other than Cinelli, do you have info on material / manufacturer ?
The intention of selecting this size is to place my handlebars in the same position as they were with the previous stem
http://www.sjscycles.co.uk/shimano-pro- ... prod16585/ handlebars

Profile Design Stem Convertor 1 inch Quill to 1 1/8 inch Threadless
http://www.sjscycles.co.uk/profile-desi ... prod20442/
Genetic Quill Stem Adaptor - 1 Inch Quill to 1 1/8 Inch Threadless Adaptor
http://www.sjscycles.co.uk/genetic-quil ... prod22444/

I have broken a number of stems, all in the same place (where they leave the headset) which of the above three is likely to be the strongest ?

Is converting to the ahead system a sensible approach or am I better off looking for a large quill stem (these seem a little thin on the ground).

Help appreciated.
Bruce.

[stewartpratt]

How come you're breaking stems? That's a very rare thing to do. Have you only broken adjustable ones, or normal types as well? When you say they've broken where they leave the headset, are they breaking on the shaft near the headset, or at the point where the shaft meets the extension?

If you're putting enough load through stems to break them then personally I'd not use a bar that's been subjected to the same loads when in an undersized clamp.

That stem looks fine - it appears to be forged, which is the strongest way (for a given amount of material) to make a stem. But then with that length I guess it makes a fair lever, and if you're breaking stuff...

Conversion is the way to go for sure, for various reasons. Re the two converters, you will want to make sure that there is sufficient height on the clamping section for the stack height of the stem clamp (which isn't listed) - it's not critical that it's at least equal, but with that style stem it should be no more than a couple of millimetres shorter (being longer is fine).

[brucelee]

photo is easier - the one on the right is the one that's just gone, the one on the left went a few years back.

[Edwards]

The one on the right does not look to have been inserted far enough into the steerer tube?
Were they both inserted to at least the minimum mark?
If they were you must be a strong person and I would not argue with you.

[Ayesha]

Wow thats a lot of exposed stem above the headset nut.

Yes there is a 'minimum insertion' mark on the stem, but stems are happier being completely inserted.

When the 'minimum insertion' mark is right on the point of being visible, its a stress point due to sudden reduction in cross section area. It will fail there.

Another thing to consider is the amount of your upper body weight that is on the bars when you ride.
On a touring bike, you shouldn't be able to crush a table-tennis ball between your palms and the bars if your weight is distributed correctly.

[andrew_s]

The wrong size bars will have had no relevance to those breakages.
A 26.0 bar in a 25.4 stem can result in the stem faceplate cracking, but that's all.

The bars should probably be OK provided you can't see any denting, crease etc at what would have been the edge of the clamp or the gap between the stem and faceplate.
Having said that, failed handlebars can be nasty, and it's a good idea to replace them every few years regardless.

[stewartpratt]

The wrong size bars will have had no relevance to those breakages.

Quite true, but then no-one was suggesting they did.

One point for the OP... Check the inner edge of the top of your steerer tube. If you have any burrs around the edge then it's possible they're creating stress risers on the stem shafts. It's unlikely, to be honest, but worth checking.

It's probably more the case that you simply have too much stem sticking out. If you want the truly most robust option, your best bet is a new set of forks with a long threadless steerer, a new headset, a bunch of spacers and a moderately-angled stem.

[Goosey]

Perhaps there's a clue in his user name?

[531colin]

I may have a monster steel (cro-mo) 1" quill stem kicking about....but I'm on the point of going away, PM me in a week or so if you're still stuck.
2 other things;
Rose Versand do some ahed stems slightly smaller than those monsters at SJSC.
"stumpneck" 1" quill stems with a steel shaft exist....if you make one of those into a quill/ahed converter, (even) you won't break it. I may have one kicking around! (shim with sections of 1" and 1 1/8 " steerer to make up the diameter)

[brucelee]

The one on the right does not look to have been inserted far enough into the steerer tube?
Were they both inserted to at least the minimum mark?

They're both right on the min mark, now I look at the KF again, I can see the hole down the middle is tapered right up to the top where the metal is much thicker.

On a touring bike, you shouldn't be able to crush a table-tennis ball between your palms and the bars if your weight is distributed correctly.

Do you mean when riding with hands near the stem or on the hoods ? I seem to put a fair bit of pressure on when riding on the hoods (which is often)

Check the inner edge of the top of your steerer tube

Looks fine, a clean factory cut

Looks like I've pushed the stems just beyond their limits, but still leaves me with the question of what to replace it with. There doesn't seem to be a quill stem that will do the job (http://www.rosebikes.co.uk/article/xtre ... /aid:27724 This is a monster, does anyone have a steerer this deep ? are you supposed to cut them down ?) So in order to get the bars in the same position, I'm stuck with a very long ahead stem and the only ones that seem to be available are the RAM ones from St John St.

[stewartpratt]

Have a rummage around for Onza trials stems...

http://www.rocknrollbikes.com/trials/st ... 165mm.html
http://www.ebay.co.uk/itm/ONZA-20-HANDL ... 0610085512
http://www.ebay.co.uk/itm/ONZA-FORGED-T ... 0655703132
etc

[hubgearfreak]

My question is, will the bars now be compromised by having been crushed by the incorrectly sized clamp ?

probably not. but i suspect that the price of new handlebars and the associated peace of mind is well worth it compared to having them snap at 30mph during being overtaken too closely by a bully in a 7.5t truck

as for quill stems, nitto have a nice range of odd sizes and they're beautifully made. sadly, they're not cheap. but then cheap ones snap...and if having the handlebars in a comfortable position comes at a cost, i've happily paid that cost

http://www.hubjub.co.uk/nitto/nittotnomzm.htm

[brucelee]

Thanks for the input, everyone - I ended up with
http://www.sjscycles.co.uk/shimano-pro- ... prod16585/
http://www.sjscycles.co.uk/genetic-quil ... prod22444/
and,
http://www.ebay.co.uk/itm/ONZA-RIP-TRIA ... 870d8c7fe0
I guessing the above is a generic badged stem with fancy graphics, hope it works with the colour scheme....
Thanks again
Bruce.

[Malaconotus]

Thanks for the input, everyone - I ended up with
http://www.sjscycles.co.uk/shimano-pro- ... prod16585/
http://www.sjscycles.co.uk/genetic-quil ... prod22444/
and,
http://www.ebay.co.uk/itm/ONZA-RIP-TRIA ... 870d8c7fe0
I guessing the above is a generic badged stem with fancy graphics, hope it works with the colour scheme....
Thanks again
Bruce.

Bruce,

Would be interested in your feedback in how much flex there was with this set-up. I'm a big chap too and the degree of flex in my 1" quill and 25.4mm alloy drops is disconcerting. I also need the bars raised quite a bit to get them anywhere near saddle height, even on my 25" frame.

Thanks,
Graham

[mattsccm]

look for older MTB stems
Many of them pointed upwards which gives more height than the normal 7 shape.
To be honest riding with that much stem showing especially if it is close to or past the minimum insertion mark is just using it wrongly. If you need to do this to bring your bars up then the bike is wrong.
Harsh I know but technically reasonably correct. Apart from using a new frame it means looking for something thats not common. As I said MTB stems ideally in steel.