EC37 Vs EC38 Trial: 1.125 to 1.25 tapered headtubes

General Discussion
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The jury has convened today to put two headset standards on trial: EC37 and EC38, in order to determine which one makes the most sense moving forwards. As you will see by the evidence provided, both have their strengths and weaknesses.

To put this discussion in context, it revolves mostly revolves road and gravel bikes.

Why bother with a 1.25 tapered standard?

1.5 tapered headtubes began appearing on road and mountain bikes in the early 2010’s. The main motivation was to create a larger headtube to land big 60mm+ carbon fiber downtubes. Builders reacted by adopting the 44mm headtube as a lowcost, easy-to-use option.

Now bike companies have scaled back their massive “aero is everything downtube” and bikes are starting to come with sleeker forks and narrower 1.25 or 1.375 headtubes (well, until fully internal cable routing stepped on the scene).

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Even though there are plenty of 1.25 tapered forks available to frame builders, we are still stuck with the 44mm headtube that we inherited 10 years ago.

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EC37 left, ZS/EC44 right

1.25 Advantages:

  • Better aesthetic for road and gravel tube diameters
  • Increase the diversity of custom frame designs
  • Switch between straight steerer steel and tapered carbon forks without compromising aesthetics
  • Save ~80g of headtube weight compared to 44mm headtube (140mm length)
  • Straight EC37/EC38 headtubes will be cheaper than IS41/47 and EC34/44 tapered headtubes

Pieces of the puzzle:

In order for this standard to work well, we need all the pieces of the puzzle. Some pieces already exist and others can be made easily. This means that this standard can be phased in gradually.

Headtubes:

Right now there are is only one headtube designed specifically for 1.25 forks, the paragon IS41/47. Everything else uses a crown race adapter with a 1.5 headset. With the adapter, you don’t get the weight and aesthetic benefit of the 1.25 fork.

With an EC37 or EC38 standard, we would be able to use slim, straight headtubes to match the aesthetics of a 1.25 fork.

Forks: (list from @PineCycles)

Road RIm

Road Disc

Allroad/Light Gravel

Gravel/Cross

Headsets:

White Industries EC37: EC37/EC37 – White Industries
Chris King D11 (EC38): Chris King D11 Headset - Dario Pegoretti

Hole Saws:

  • 1.625 (41.3mm) hole saw
  • 40mm hole saw
  • 39mm hole saw does not exist!

Reamers:

  • need to figure this out!

EC37 vs EC38

There are two ways to make a straight steerer tube:

Arguments for EC37:

  • Historical Precedent from 90’s mountain bikes
  • Currently supported by White Industries

Arguments against EC37:

  • There is no lightweight 39x1.1mm swaged tube option because there is no 39mm holesaw!
    • we would probably need to use a 40x1.6mm tube which is much heavier
  • There is no titanium headtube solution:

Arguments for EC38:

  • Titanium headtubes can be made from tube stock 1.625x.07
    • We are talking about a $30 headtube vs a $100 machined headtube!
  • A swaged 40x1.1mm tube works just like the tradtional 36mm tubes for EC34

Arguments against EC38:

  • The standard does not have a historical precedent (only used by Pegoretti)
  • The whole purpose of the 1.25 headset is to make the headtube smaller
    • EC38 makes the headtube ~1mm larger diameter

Conclusions:

I think an EC37 or EC38 standard can make custom road and gravel bikes look better, open up more diverse designs, decrease their cost, and decrease their weight. The forks already exist, we just don’t take full advantage of them.

From a technical perspective, I think EC38 is the more versatile option. EC37 has a historical precedent.

Bigger picture, I think we need to redesign road and gravel forks to modernize our metal bike frame aesthetics. But it’s a chicken and egg problem: The headtubes don’t look bulky because the forks are bulkier. This is an example of what I consider a “modern-looking fork”:

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Discussion Points:

  • Are you totally happy with EC44?
  • Are you totally happy with EC34?
  • Does the history and precedent of EC37 mean anything to you?
  • Would you use EC38 for titanium bikes?
  • If you had to pick: EC37 or EC38?
  • Is all this discussion useless because road and gravel bikes will be fully internally routed?
6 Likes
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I would love to hear the opinions of professional builders. Sorry if I missed anyone, there are too many here for me to keep track!

@PineCycles @DEVLINCC @manzanitacycles @adamsklar @Meriwether @wzrd @Swood @La_Marche @Neuhaus_Metalworks @liberationfab @Jackalope @Carl_Snarl @mark_pmw @Calvin_pmw @BikeFabSupply

I don’t really have a stake in this game, so I won’t be offended if people don’t buy in. I just want to see more things:

  • More diverse custom frame designs
    • 44mm headtubes make frames look the same. Bring back the weird forks and machined rings!
  • Viable alternatives to compete against the fully internal cable crowd
  • More low-cost options
  • Better looking custom frames
  • Successful collaboration among framebuilders and suppliers

Regarding EC37 vs EC38:
I went into my analysis assuming EC37 was the obvious choice. Having done the engineering, I think EC38 might be the better due to 39mm hole saw availability and titanium tube sizing. Both those problems are really expensive to solve.

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I truly love the concept.

44mm head tubes are heavy and look so damn big on skinny tubed gravel and road bikes.

I think if there was brand support through a reamer and affordable-ish head sets (cane creek 40 / wolftooth performance), that a lot of builders would start to use it.

Weirdly, my Park reamer set came with a 1.125 guide, but they don’t seem to make a ec37 reamer.

To throw a wrench in this, I believe English is squeezing 1.125 forks into EC34 head tubes with a custom lower headset cup. If a cup like this came available to the public, I’d run with it.

My only fear with the English set up is that it might have the same issue as BSA30 - such tight clearance between the moving and non-moving parts that it doesn’t leave much room for potential gunk and grime build up. But I haven’t actually drawn it up.

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For headsets, I’m pretty sure I can get good low-cost options through my Taiwanese suppliers. Probably a MOQ or 200-300 though, so it would need some buy-in. Luckily there are already headset options, so a cheaper headset can be phased in.

The reamer is going to be harder and not really my area of expertise. We might need to custom-grind an existing tool or look outside bike reamers:
https://www.gavantools.com/products/37-9mm-hss-straight-shank-reamer-h7?variant=29936735158371

That is a cool solution. I think we could easily custom-manufacture a cup for that. I have two concerns:

  • As you point out, the space is tight, and forks have different tapers that might interfere with the cup
  • Totally subjective: I think the headtube looks great, but now the fork and headset look really big!

At that point, maybe the solution is that we need more 1.125 straight steerer carbon forks?

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Most of my customers want either a steel or carbon fork. If steel, then I can use a slim HT and EC34 or EC30 cups. If carbon, I’ll use a tapered head tube for lower EC44. I like the look of tapered tubes even though they take more work to build with.

As a custom builder, I don’t see the value in offering the option for customers to run both types of forks. You end up making too many compromises. But I’m not in the market to make a quiver killer.

For companies like Pine and maybe even Neuhaus that focus on model-based production, the added flexibility seems like a nice selling point. Then customers can use whatever fork they might already own as long as the length is in the ballpark.

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I think the EC37/38 can solve some technical challenges with straight 1.125 steerers as well.

For example, there is the case of an XL frame or heavy-duty offroad bike that needs a 38mm downtube. You would need to ovalize the downtube to get it to fit the smaller 36mm OD headtube. The 38mm downtube would be better matched to a 41mm headtube.

Also, I imagine the 41mm headtube gives a bit more margin for fillet brazing with a 35mm downtube (compared to a 36mm headtube).

This discussion made me realize there are a few straight 1.125 gravel forks out there:

Also a few low cost, straight EC37 1.125 headsets:

We’re not really big fan of swapping forks either. We don’t even want customers to change the travel on their forks :rofl:

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Most of this is over my head but appreciate you talking through the logic of it all Dan. Crust do a straight 1-⅛" steerer carbon fork too so it seems there’s a small amount of support for this. Personally I don’t think these look that great on a steel frame but then again I don’t love the look of carbon forks generally. Ad for that kinda money I’d rather have a nice custom steel fork.

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For a really heavy rider or a huge frame, I’d probably use the 1-1/2" tapered steerer PMW makes and use a tapered HT with EC44 lower cup. On a big frame like that the tapered head tube wouldn’t look out of proportion with a 38mm DT.

I guess for me it’s like the popular seat post sizes. There’s 27.2, 30.9, and 31.6. I only build for 27.2 and 31.6. I don’t want to have more cutters and reamers and other expensive tooling for a third option.

Haha. Agreed. Sometimes you have to talk customers off the Iwantalltheoptions cliff.

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@Carl_Snarl informed me that the Serottas he built used EC38 headsets. It looks like a custom headset:

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The proportions on this frame look great, what a beautiful road bike! I almost didn’t notice the chain in the small ring :rofl:

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Another photo of the headtube and headset:

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I will send out a few feelers to see what the MOQ and lead times are on custom EC38 headsets.

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I see this as a solution for the all road/light gravel market since a true road bike will likely just use the tapered is41/47 option.

My vote is for EC37 because it’s a little smaller and I support my neighbors at White Industries. I also will just buy the expensive machined headtube in titanium.

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I’m already in the EC34/EC44 camp with my road and gravel frames. I use the Columbus tapered head tube, Cane Creek head sets, or I machine my own cups.

I use the Columbus Futura SLX Disc forks for my road bikes…

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and their Gravel fork for that option…

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I’ve done a couple frames where I’ve used the Columbus 34/44 head tube with a 1 1/2 steerer with a custom bottom cup. It was ok but I’d prefer to only use the 1 1/4 steerers.

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So a buy in for me into what other builders would use is a hard one. I guess I look at it is if we are all using the same frame parts to build our frames it makes it even harder to differentiate what we do. I can see from a production point of view having a set list of materials that you get better pricing for bulk orders and there is some consistency across the production runs. Also for the guys without lathes and big machines being able to just buy what they need is an attractive solution. I am trying to settle on my recipe so Im not having to do so much custom fabrication everytime I build a frame and have settled pretty much on the road gravel frames. Currently am putting in place the same for the mtb farmes where I an reducing the time to make parts and it’s more just sticking stuff together.

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I don’t get the “swaged” vs “machined” comparison. A straight tube doesn’t need to be swaged, just reamed to finish diameter and depth. The non machined version would just be a straight tube with no processing necessary.

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By swaged, I mean the process to turn a 1.625in tube into a straight 40x1.1mm tube. There is no combination of off-the-shelf tube diameters and wall thicknesses that get close enough for a EC37 or EC38 bore (except for the weird titanium 1.625x.07in tube).

The swaged tube is the traditional method where you braze on reinforcement rings (or not) onto a straight tube. It’s marginally lower cost and more customizable.

I think that if you are machining a 1.625x.188in tube down to 40x1.1mm, you might as well machine rings and internal relief.

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1.625 x .095 would work fine. You would have an unfinished ID of 36.45mm and once reamed to 36.95 a wall thickness at the cups of 2.03mm, definitely less than ideal but really not that different than what gets done currently with straight tube for 34 and 44mm headtubes.

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I think your EC34/44 solution looks really good, especially with the custom headset. I played around a bit with a custom EC44 1.25in headset design to match a 52mm crown. I think it’s a viable option (although, probably nitpicking the aesthetics at that point).

Out of curiosity, when do you use reinforcement rings vs leaving it just a tube? I feel like ovalized headtubes are a mountain bike issue. I have never heard of an ovalized gravel headtube, but then again, gravel bikes have not been around that long.

I think most of the benefits of a EC37/38 headtube are cost and time savings:

For the full custom builder, cost and time probably do not matter as much because the customer can pay for it. I think this EC37/38 headtube would be more impactful for lesser-known builders, hobbyists, and fixed-model custom builders.

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For ovalising I kind of get away with in fabrication by using silver for tehfillets. Much less heat. I’ve flipped between putting rings on and not but my main rule of thimb is road no rings and gravel has rings. I could be wrong with that over time but so far I’ve not had any issues show up. The caveat with that is those frames haven’t gone past about 4 years old yet and no reported issues so far.

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Small correction, tapered became a thing in the early 2010s, not early 2000s. Early 2000s was still v-brake days for a lot of bikes!

-W

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I think ovalised Headtubes are also a thing of the past in mountain bikes. I’ve owned an Intense M1 in the past which had an aluminium 1 1/8" headtube with EC34 classic “Ahedset” but a 200mm beefy double crown fork and slack-ish head angle (at least for the time being) That one ovalized. But totally different loading situation here.
(I “fixed” it by fitting a CK Steelset with extra long sleeve, before I ripped the HT off in a crash a few weeks later…)

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I have used those old Chris King steel sets a few times to “fix” an ovalized headtube back in the day, mostly on aluminum frames. Almost every time the frame would crack shortly after. Those things were so burly.

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From a machining perspective, we would prefer EC37. EC38 is unique to Pegoretti, and 37 mm cups do have a historical precedent. The available material, 1-5/8" x .095"w, is just about the perfect size off the rack. We can make a headtube that is internally and externally relieved, has a 2 mm wall at the cups, which is plenty stout, and a 1 mm wall at the center section. OD at the center section will be 1-9/16", a readily available hole saw. We haven’t figured out a price yet, but it will certainly be less than our EC44 headtubes, with a significant weight reduction.

We also have a large stock of 1-5/8" titanium tubing, so ti is no problem.

Here’s the graphic, dashed line represents the finished 37 mm ID:

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For a budget headtube, any builder can get some 1-9/16" x .065w" tube (may only be available in DOM) and add some rings. The ID of this tube is 36.37 mm, a bit much to ream, but not impossible. If there’s demand, we could supply a headtube kit of a section of tubing and the matching rings.

@Neuhaus_Metalworks had a great comment about supporting his neighbor White Industries, and we agree. Component manufacturers like White are key to bringing some sensible evolution to frame building. White’s contribution to T47 has made it a success.

Let’s not get into the old complaint about, “No, I can’t handle another new standard!” Evolutionary changes like this have almost always resulted in a better product.

Let’s ignore internal routing for the moment, as an EC44 headtube will do the job. The goal here is to move away from heavier, esthetically large headtubes, and come up with a practical solution for steel framebuilders.

We have 20’ of material on order to make some prototypes. We’ll give out samples to anyone who asks, as long as they’ll provide feedback. Please comment if you want one, and also what lengths you prefer.

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