Tubeless-Compatible 650B x 42 mm

The updated Compass Babyshoe Pass TC 650B x 42 mm tires are now in stock in all models. What’s new? We took our most popular 650B tire, and made it tubeless compatible. When you are riding fast on rough gravel, tubeless really makes sense – as I found out when I had dual pinch flats on a Bicycle Quarterly test bike on the original Babyshoe Pass tires (below).

You may wonder how I pinch-flatted on what looks like a smooth gravel road. It was smooth, and so we let the bikes fly on a fast downhill section. Right after a bend in the road, the gravel turned very rough. It was only a short section, but it was enough to pinch-flat both tubes. By the time I had stopped the wobbling bike from a speed of 65 km/h (40 mph), the road was smooth again, as if it all had been a bad dream. At least it was a scenic spot to change the tubes…

While we were making a new tire mold, we also increased the width of the new Babyshoe Pass by 1.5 mm. Now the tires measure a true 42 mm wide on most rims. That makes them the perfect tires not just for randonneur bikes, but also for a whole generation of gravel bikes like the Litespeed T5G and the Cannondale’s Slate.

What about the name? Babyshoe Pass is a 1330 m (4350 ft) high passage between the great volcanoes of Mount St. Helens and Mount Adams in the Cascade Range (above during the recent Volcano High Pass Challenge). The origins of the name are shrouded in mystery, but that doesn’t keep passers-by from hanging baby shoes from the sign (top photo). It’s a great way to travel from Seattle to Portland while avoiding the crowded Puget Lowland.

During challenging rides like this, you will enjoy the Babyshoe Pass TC tires, which roll as fast as racing tires on the paved lower sections of the climb, yet float across the gravel as you cross the actual pass. No matter from which side you ride it, the descent is so steep that speed builds quickly. As you fly across the gravel, you’ll appreciate the possibility to run your tires tubeless. When you don’t have to worry about pinch flats, you can even look up from the road and see glimpses of Mount Adams snow-covered cone. Of course, like all our tubeless-compatible “TC” tires, you can also run the new Babyshoe Pass TC with tubes.

The original Babyshoe Pass (without the “TC” in the name) remains available as long as supplies last. It’s a little lighter, a little narrower and a little cheaper than the new model.

Click here for more information about Compass tires and the new Babyshoe Pass TC.

 

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into high-performance components for real-world riders.
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16 Responses to Tubeless-Compatible 650B x 42 mm

  1. Nice! Will look closely once I worn my Schwalbes G-One.

  2. Bob C says:

    In making the other changes, did you end up changing the rubber tread to accommodate tubeless?

    The features of the new version are great, but if you suspect they might wear more easily, I might stock up on the old version (which are long-wearing champs in my view).

  3. Mint Zebra says:

    What’s the ideal inner rim width to achieve the true 42c size?

    • With supple tires, rim width isn’t so important. The tire sidewalls don’t really hold up the bike, which is why you need a little more pressure than with stiff tires. To visualize this, think of tubular tires, which touch the tire only at the bottom, yet they work fine even for mountain bike professionals.

      The 42 mm Babyshoe Pass are happiest on rims between 23 and 28 mm wide (outer width). You can run wider rims, but don’t use rims that are more as wide or wider than the tire…

      • Andrew Squirrel says:

        Don’t most manufacturers prefer to share inner rim width since the outside does not contact the tire at all and therefore irrelevant to the final tire measurement?
        Now that Disc brakes are starting to become popular I’ve noticed the wall thickness of the rim varies quite a bit whereas older machined brake walls for rim brakes were a little more predictable.
        Is there a benefit to measuring the outer width of a rim that i’m not aware of?

      • The reason to list the outside dimensions is simple: Customers can measure this on their bike with simple calipers, without having to remove the tire or the wheel. We get the question: “Can I mount your tires once mine wear out?” quite frequently, and asking the customers to remove the tire and wheel to measure the inside width is not necessary, since the rim width isn’t crucial.

  4. Michael Kennedy says:

    Jan, do the thinner sidewalls of the extralight casing allow more air to leach out over time than the standard sidewalls, or is air seepage on tubeless just from the bead seat? I’m new to tubeless and am still trying to figure out what works best…

  5. wayne Sulak says:

    I know you cannot please everyone but I want to let you know that this unexpected change in width is disappointing. I am sure others must have written think the old ones too narrow. Maybe those who thought they were too narrow needed wider rims? I have been very happy with the old 42mm (on my velocity a23 rims) tires and now I have a frame I will may have to drop to 38s on.

    I tried to buy a large supply of the older tires today, the same day you announced the new wider tires, and you are all out. I guess others had the same idea. If any become available I would gladly puchase 8 or 10.

    • Sorry to hear about your disappointment. If your bike barely accepts a 40 mm-wide tires, then the new ones may indeed be too wide. (Most users probably won’t notice the size difference, unless they break out their calipers.) Fortunately, the Loup Loup Pass is only about 2-3 mm narrower than old Babyshoe Pass tires. For us, it made little sense to have two tires that were so close in size, and then have a huge gap in the program to the 48 mm Switchback Hill. Making the Babyshoe Pass a true 42 mm makes it more useful for most riders.

      As to the availability of the old ones, the Standard casing is indeed sold out – we had very few left – but we still have the Extralight casing in both black and tan. You can order them here.

    • Jacob Musha says:

      Since you already have a mold for the original Babyshoe Pass, would it be too much stocking hassle to offer both? I’m sure some people who prefer tubes would still buy them.

      The advantages are very minor, but I find your original non-tubeless Barlow Pass a bit easier to seat than the tubeless-compatible Rat Trap Pass (different wheel sizes and rims though, making the comparison difficult). Tires not designed for tubeless can also be lighter, correct?

      For me, using a tubeless tire with a tube feels like designing a stiffer and heavier fork around a disc brake, but then using a rim brake. It would be a little nicer to just have the rim brake fork.

      • The mold has already been scrapped. Those molds are huge, and storing them costs money. Furthermore, Panaracer was concerned that there could be confusion with two molds that are so similar. For us, the cost of keeping three additional tires (Standard plus Extralight in tan and black) in stock also would increase the cost, and we’d have to make all our tires more expensive. It makes little sense to go through all that trouble just to offer a tire that is 1.5 mm narrower than the new model!

        For me, using a tubeless tire with a tube feels like designing a stiffer and heavier fork around a disc brake, but then using a rim brake.

        That isn’t a good analogy. There isn’t any disadvantage to the tubeless-compatible version. It’s more like having a frame that is prepared for STI and running bar-ends instead. You use the same cable housing stops, but run the cables to a different spot on the bars. Same with the tires: Either stick a tube inside or put in a liquid sealant. The bead shape is new, but a good interlock between tire and rim is a good idea even if you use tubes.

  6. SteveP says:

    My patience is rewarded…a tubeless slightly-wider Babyshoe Pass. The only two ways to make this tire better.

    I’ve been using tubeless (Orange Seal, Enve M50) extralight Switchback Hills this year with great success but look forward to using this new Babyshoe as a more perfect everyday tire.

  7. Do you plan to make a tubeless version of the Loup Loup Pass 650B x 38 mm? I’d like to try such a tire. 38 mm will be wide enough for many of us- particularly on a wide rim. Going forward we will likely see more 650B bikes on long events, with mostly paved roads, like the Transcontinental Race. A 38 mm and slightly lighter 650B tubeless tire might be perfect for this kind of race.

    • We may offer the 650B x 38 mm tubeless in the future, but we also realize that tire sizes are continuing to increase. Just a year or two ago, most riders thought that 32 mm was wide. Now 38 mm seems right, and soon, it’ll probably be 42 mm. Much wider than 42, you start running into compromises with fenders and cranks (tread/Q factor), so I suspect we’ll stop there.

      Give the 42s a try, you won’t be disappointed. I’ve ridden some of my fastest (all-paved) brevets on 42s…

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