Tag Archives: bicycle

Bicycle frame jigs (2/4)


The election of a frame fixture is not just a matter of budget. It is obvious that if you are going to produce few amateur frames a flat surface or a beam design jig will suit you. If you circulate large amounts of kind of the same type you should ponder over switching to something that ease the assembly and welding at the expense of less versatility.

Potential frame builders have the mistaken idea that the jig must be extremely accurate, built like a precision timepiece and yet possess immense strength for bending and holding the tubing sections in position for welding but in fact the base structure of the jig, sometimes called the backbone, bed, table, base table, face table or frame face can be almost any relative rigid structure. As long as the backbone is level in all directions the real precision and accuracy will come about through the fabrication of the fixtures that attach to this substructure (backbone) and then will be adjusted and secured to position and hold the tubing and parts in place during the fabrication of the frame.

A modified flat plate is enough for welding a bicycle frame

A modified flat plate is enough for welding a bicycle frame

For around 300$ you can start to think about it. In old Europe, for less than 400€ I’m struggling to find the right materials to accomplish my project. I guess this continent is not that cool anymore, isn´t it?

Don´t forget that choosing a frame jig is closely related to the welding technique. For example, brazed lugged construction requires the most from a jig. Full access to each joint is critical. When using lugs, most builders prefer to braze the complete frame in the jig unlike lugsless construction where jigs are used only to tack at 2 to 4 spots on each joint.

Silver brazing a lugged frame

Silver brazing a lugged frame

Consider most jigs offer limited access to one side of the frame. On top of that, if you are gas welding just forget about tackling the job on a cheap parallel beam jig for example. The heat coming from the torch will deform beam materials affecting our setup.

Nowadays TIG welding has become the superstar for joining the tubes of a frame. Both bicycle factories and custom workshops uses it on a daily basis. SMAW, GMAW, FCAW SAW are others common types of arc welding procedures but useless because of the thin-walled bicycles tubes.

Automated robot welder at Merida - Taiwan tacking a full suspension frame.

Automated TIG robot welder at Merida – Taiwan tacking a full suspension aluminium frame. Hand-welded frames are still far superior.

Besides TIG (that uses electricity), gas welding (oxyacetylene for example) is also possible, been the standard for 70 years. As good as it is, gas welding cannot compete with TIG. Anyway, oxy-fuel is still required for brazing, either fillet brazing (bronze weld) or brazing lugs (silver weld). These realiable and old-fashioned methods are still popular between cycle enthusiasts, that’s why you have to keep them in mind for your future jig plans.

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Checking the chain stays

So far: budget, quantity and welding procedures have been taken into account. The quality of a frame depends more on your miters, the time you spend fine tuning the geometry and your welds rather on an expensive jig, that can offer good accuracy of course. Amazing frames can be produced with simple tooling and great skills.

But there are also few considerations about the bicycles you are going to build and how you want to work in order to select the right jig:

  • What are the limitations in the seat tube area? Does the top of the seat tube have to be square cut? If it does, you can’t pre-shape the seat tube top, or use a seat lug with an internal ledge for a cut to length seat tube.

  • Does the seat tube holder arrangement pivot about the center of the BB shell? If so, you can’t build with the seat tube offset from the axis of the shell.

  • Can you easily build interrupted seat tube designs? These are common and unavoidable with rear suspension frames.

  • Are you in the mood of ISP? If you are, size the jig up accordingly or fabricate an extension.

  • How versatile is the rear axle arrangement? Most jigs come with one axle for only one spacing. You have to pay extra for any other spacings. 130mm road frames and 135mm mountain frames eclipse other preferences. How do they do 120 mm track spacing, or 126 mm old road spacing (for restoration, repairs, or using classic parts), or 145 mm if the jig also builds tandems, or the new MTB standard142xM12, or 165-170mm for fat bikes?

  • How do they handle the inevitable pull-in of the rear dropouts?

  • Do you want to build the frame from the BB up?

  • How do you build forks? A fork building feature could be integrated in a design. The rear dropout holder doubles as the front dropout holder in the Henry James Universal frame jig for example. A separate professional fork jig usually costs about $500. You don’t usually build forks? That is all the more reason to have one built in for when you do need one!

  • Can you build the occasional tandem on the jig? An attachment of some sort must be used, and you should not expect the adapted jig to be good for a tandem specialist.

  • How do you mount it? Because of the jig weight and bulk, most jigs require an expensive and complex mounting system that can increase your costs.

  • How portable is it? How much storage space does it need? TIG welding is not a straightforward skill. You might want to set up a frame in the jig, then single-handedly put it in your vehicle and take it to a full-time professional welding shop (an easy way to get perfect welds) for tacking while you wait. Even on a moveable stand, most jigs take up a lot of space.

A case of study: 29er inner tubes


Not long ago bike shops struggled to source specific 29er tubes (700x54mm). A widespread practise was to overinflate the classic 26″ size or 700x35c inners with the risk of sudden blow ups, decreased rolling eficiency and more punctures. Only some beefy tubes behaved well with no surprises for this purpose.

Foto 1 Nikki Gudex tubes

Tubes are within the most iconic bicycle components

Now the market is full of 29 inches tubes. For around £4-5, 6-7€ or 7-8$ you can afford good quality spares. Maxxis (Taiwan) and Schwalbe (Germany) are remarkable brands that produce tubes in many different sizes.

After damaging the original “unlabelled” tubes that came with my bike (probably made by CST, Vee or any other asian bulk manufacturer), I picked the Maxxis Welterweight (4,24€) and Schwalbe Extra Light (6,60€), both in online stores, to give them a go.

A thousand kilometers after testing the tubes with new tyres, the Maxxis tube has result in an amazing and absolute quality product. A bargain for the price (now over 5€).

Maxxis tubes are always true to the word of the company. Since the moment you open the box they meet the announced weight in the worst scenario, and sometimes a lot less.

The Welterweight is not a weight weenie product unlike the intended use of the Schwalbe Extra Light. Officially 205g. versus 140g. Note that the thickness of the butyl wall and tube dimensions will determine its final weight. The valve type, porosity and overall rubber quality have a negligible impact on it.

Foto 2

Maxxis tubes are made in Taiwan while Schwalbe units come from Indonesia

The good thing of the Maxxis is the fact that it is a real 29er inner tube. The Extra Light tube width doesn´t meet the requirements to fit securely a 2.4 tyre despite it is recommended for this size. It is clear when you put them close together that something is wrong in the Extra Light product. It looks like a 700x35c spare.

But what is even more shocking is reading the compatibility printed in the cardbox. It suits also 650b/584mm/27.5 wheels! Wouldn´t have been any wiser to make a compatible 650c/26″/559mm and 584mm tube while producing separately the specific 29er size? The discrepancy of the 29er size (622mm) with the 584mm standard is more than the 559mm measure has instead.

Foto 3

A nonsense of tyre matching specifications that even claims 700b compatibility (635mm)

The result is that the Schwalbe model is not a proper 29er tube and nor a 650b one. You have to slightly overinflate them on 2.2 Continental Mountain King tyres for example. It’s tricky to slide equally the tube inside the tyre bulging it on many ocassions unless you use an air compressor.

What’s more I got quite a few flats. None with the Maxxis. I reckon even the rolling eficiency is compromised with such a tight fitting. A hassle.

The final blow came when checking the weights. The taiwaneses are only 40 grams on average heavier than the germans, instead of the expected 65g.

Average weights

Average weights. Less than 40 grams average discrepancy between models

Cheaper, easier installation, more reliable and keeping the pressure for longer my vote is on the Welterweights. It’s great that Maxxis produces almost each single size of bicycle inner tubes. Meanwhile the design of the Extra Light tube is all messed up.

The mysterious rubber block


I’m surprised that not many users know what is the small piece shown below for.

Well, if you’ve got big hands or you’re not a roaddie you might have never missed them.

On the subject of Shimano’s STIs they will bring closer the lever making shifting and braking more comfortable. Consider that short riders and girls mainly, have difficulties to reach the lever causing long term fatigue.

With this rubber shim inserted on top of the shifter unit the angle will be modified some degrees. Depending on its thickness you can setup the reach of the lever 4º or 8º degrees less with the original Shimano spares.

Unfortunately, they are not universal and will vary on each Shimano shifter generation.

While all ranges use rubber inserts, top notch Dura-Ace 7900 levers can be tuned with a concealed screw hidden behind the plastic decorative cover. Remove it by unscrewing the small retaining screw, then gently pry back as pictured the cover from the top. This will expose the brake cable anchor and adjuster. Turn the nylon adjuster clockwise until the desired lever position is reached.

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As for the DA 9000, just pull back the shifter hood making visible the flathead screw that will allow lever reach adjustment.

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