The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Todd from Black Cat Bicycles knows a thing or two about mountain bikes. Living in Santa Cruz provides a more than ideal testing ground for everything related to dirt. Over the years, he’s dialed in the geometry on his hardtails and recently, this process culminated in what he’s dubbed the Thunder Monkey.

A few months back, Todd emailed me asking if I wanted to review a production bike he was making. His description was right up my alley “slack and low 29r with a tight rear end.” Some time passed and this incredible frame showed up at Mellow Johnny’s to be built up with various SRAM and RockShox products.

Since then, I’ve been putting this bike through the hell that is Central Texas limestone. How does a bike designed to conquer Santa Cruz bide in Texas? Damn well. Check out more below.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

We’ll break this down in an easy-to digest format. While a few “media sources” received Thunder Monkeys to review, I’d like to think we all built them a bit differently. I chose SRAM and RockShox for the parts, so let’s look at those individually, beginning with the front suspension.


The RockShox RS-1 may appear to be just another one of the industry’s gimmicks to get your money. While it is an expensive system, especially considering that you’ve got to use their proprietary hub, the ride quality of this fork is unmatched. It’s incredibly light and nimble, yet delivers the right damping with ease. My take-away note here is that with the RS-1 fork, a lightweight steel hardtail suddenly rides more balanced. Versus, say the Pike on my Rosko, which tends to be a bit heavy on the front. Expect a more in-depth review to come.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Next up, the drivetrain. Tried and true XX1 with a direct mount ring that looks clean and saves you the hassle of checking chainring bolts. Because, you know, that is such a pain. It saves weight and looks so damn clean.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Braking on the Thunder Monkey is provided by my new favorite brakes, SRAM’s Guide RSC. Without going too far down the tech rabbit hole, I’ll just address the one question that’s on everyone’s mind “are they comparable to XTR?” In short, yes, the long-term review is on the way, but I’ll quickly add that these brakes are better than XTR’s new brakes, by far. According to my opinion anyway.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Wheels are the tried and true Roam 60’s, which I’ve expressed my love for in the past, although on the maiden voyage of the Thunder Monkey I did break a spoke which was an easy enough fix.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Droppin’ the post is the Reverb Stealth. I have a love/hate relationship with droppers. I love them when they’re working. Hate them when they’re not. It’s a simple fact that droppers are an ever-developing technology and kinks are always being worked out. Since RockShox moved production of the Reverbs to a “clean room” in their factory, there have been less problems. Also, I would note that this is the first Reverb I haven’t had issues with and it was from the new batch of posts.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

All of these components will be addressed in the future on an individual basis. What I will say is this is one of the most dialed hardtails I’ve ever ridden. Everything flows and works together like a charm. Especially on such an insane frame.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Todd’s concept with the Thunder Monkey was simple: make a hardtail that descends with confidence and climbs with agility, all while looking god damn gorgeous. Wait. Can a mountain bike be gorgeous? You tell me.


This is a fillet brazed frame and utilizes some of Todd’s sneaky signature details. The head tube gusset and sleeved, curved seat tube are the two pronounced details and his custom dropouts always get a lot of attention. I wish Todd built this bike with a thru-axle rear, because the 2.4 Ardent does rub on the stays during out-of-the-saddle “efforts.” Still, a 2.25 Ardent would fix this problem.

One of the benefits for a QR rear is the ability to pop and pump the frame, due to the “lack of stiffness.”

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

Other nifty little moments include the internal dropper routing and third bottle cage mount, in case you wanna go a bit longer with the Thunder Monkey.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

My favorite detail on this frame is the fillet bullmoose stem that fits a 31.8 MTB bar.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

The paint was done in house by Todd, after dipping into the “special honey.” An olive base coat is accented by swooping lines that collide around each other on the 44mm head tube.

So, how’s this thing ride? Well, for starters, it’s a little shorter than what my “fit” is to be on a hardtail. Since Todd made a few of these in production sizing, it’s far from a custom fit. Yet, the intent of the Thundermonkey is uninhibited by this slightly shorter reach.

The Black Cat Bicycles Operation Thunder Monkey 29r MTB

When a bike has a shorter reach with a slack (69º dude!) head tube, it enables you to drop back further over the rear hub, making it easy to get buck wild. Then, on the short and punchy climbs we have here in town, it makes it easier to get over the front hub, which is ever-so-slightly more proud than a steeper head tube would provide. The 14mm of reach deficit is a non-issue in both of these cases.

The only moment where it really sucks is the pedal out to the trail and any kind of flowy meandering singletrack. It also rules out me using the stem if I were to do any kind of bikepacking on the Thundermonkey. Again, not a custom geometry, just a by-product of a production frame. If and when the Thundermonkey goes to full on production, I’d ride the XL, versus the L.

Thunderous Monkeys belong in the woods. They belong blasting down everything from peaty, loamy redwoods to craggy and loose limestone. This is hands down one of the funnest bikes I’ve ever ridden. It’s also the most beautiful mountain bike I’ve ever had in my possession. If you wanted to go really over the top, murdering out all of the components would make it even slicker.

Todd’s work is some of the most unique in the industry and his story is something else. Hopefully I’ll get to visit him in Santa Cruz and ride the trail by his house where the Thunder Monkey was born.

If you’d like to buy this frame, holler at Todd, because it’s for sale. OR if you’d like him to build you a custom bike, send him a note at Black Cat Bicycles.

Now, I need to get a few more rides in on this beast before I send it back!

  • Kyle Campbell

    I’ve never been this turned on by a mountain bike. That thing is stupid hot.

  • STW

    Looks like the bar tapers down too quickly given the width of the stem clamp. Is it being evenly clamped?

    • It’s rock solid.

      • STW

        I’m sure it’s solid feeling, but is there a radial point load on the bars because the stem’s clamping surface isn’t fully contacting?

        • I don’t think about things like that.

          • boomforeal

            doesn’t it bug your architect brain?

          • My architect brain focuses on the details that work incredibly well and sees things like an experimental stem that still functions with a mere aesthetic error as it is: something made by hand.

          • boomforeal

            you are lucky. my lawyer brain sees only graiting flaws. everywhere :-(
            i am generally able to turn it off for bike reviews, though ;-)

          • That must suck! ;-)

          • STW

            I was approaching it from a safety standpoint, btw. Not aesthetics. But Black Cat Man answered my question with some actual numbers.

    • black cat bicycles

      the bar and stem in question are well mated. the stem width on this stem is shy of 3″. the bulge on an enve sweep is 3.25″ in width. i built a stem on my bike 3.25″ wide and and i haven’t had a problem with it in the two years i’ve been running it. the radial load is something i think about, particularly with a carbon bar. as such, i build the stems using tubing with thicker walls, only boring the clamping tubes out after everything is welded, pinch bolts included. by doing that extra step (or two) i can keep the clamps very round and to .005″-.007″ over the diameter of the bar (1.255″-1.257″). by doing it this way, the stem’s handlebar clamp is very close to the final shape when everything is tight and radial irregularities are minimized or negated altogether. the gap you see may be a trick of light, or it could be a gap on the edges of the stem where the clamp texture on the bar has stopped. the surface area of the bar clamp is (at least) ten fold of what one would find on a thomson (for example), so i reckon it’s ok.
      are everyone’s eyes glazed over yet?

      • STW

        No, I like it when you talk decimals to me. Keep going. I’m almost there.

  • Kerry Nordstrom

    Ride dampening indeed. I’d be wet too if I had that bike to shred!

  • boomforeal

    the geometry is great for descending, and climbing, just not for transfers to and from the trail… and yet you’d size up? why not get a longer stem for bike packing and call it good

    • boomforeal

      also: one (non-copy related) correction: dropper posts have been around for
      over a decade (the gravity dropper [which btw is ridiculously reliable]
      was launched in 2003), or three decades if you count the
      remote-controlled hiterite
      you should do your research beyond offering up simple facts

    • My Rosko is the same geo, just longer and excels at everything without swapping a stem. I can move my body 14mm pretty easily.

      • boomforeal

        “When a bike has a shorter reach with a slack (69º dude!) head tube, it enables you to drop back further over the rear hub, making it easy to get buck wild. Then, on the short and punchy climbs we have here in town, it makes it easier to get over the front hub, which is ever-so-slightly more proud than a steeper head tube would provide.” personally i’d take the frame that makes it _easier_ to get loose and climb grunters, but that’s just me

        • We have different fit philosophies. Agree to disagree.

          • boomforeal


        • black cat bicycles

          me too, but i live in a place where there is so little flat trail that it makes sense to ride a bike that’s built for a lot of body english. when building a custom bike, there are questions such as, “what are the trails like where you live?”, “how do you like the top tube length of your current bike?”, “how does it effect your riding?”, etc, etc, etc.
          the “stock sized” bike in question was all but finished when john came into the picture. when designing this bike, had i known it was going to someone who prefers a longer top tube, and who lives in a place where descents and climbs are short and there’s a lot more flat trail, things would have ended up differently. when it comes to mountain bikes, rules of thumb for fitting are somewhat
          marginalized and a lot of personal preference must be taken into

          if john were to take me up on showing him the trails from where the thunder monkey’s design cues are born, he might be singing a different tune than the one he sings so well from texas. maybe…

          • When I return this bike, I wanna do so in person in Santa Cruz and ride those trails. I think that’s a perfect tie-in to this story.

            Thanks for everything Todd!

  • D0rk

    If someone were to want to replicate that fabric chainstay protector, any suggestions on material and installation techniques? I’ve got a steel dirt tourer/commuter coming and I think that would look great on it.

    • Newbaums bar tape and it comes in just about any color you would want.

      • Yep! That’s what I used.

        • D0rk

          Can I ask how it’s attached? In Pic #20 I don’t see anything on the end holding it down.

          • I wrapped it and used a 3″ piece of the tape to hold it down.

  • hans

    “Can a mountain bike be gorgeous?” Yes.

  • Angus Kilpatrick

    Impressions on the bar? I had been holding out from a carbon bar for my Stumpjumper EVO 29 because they didn’t make 31.8 compatible bars long enough. But 760mm would work for me…

    • I’d like them to be wider. I’m using the Ritchey Trail on my Rosko and I love them. Although ENVE did make all their bars wider recently…

  • colavitos_ghost

    maybe it’s just me, but a broken spoke on a first ride seems to warrant more than a perfunctory mention.

    • Andy Brown

      It was the first ride for the complete bike, he cherry picked the wheels from his wheel quiver…

    • I’ve had these wheels for two years…

      • colavitos_ghost

        thanks for the response. i wasn’t clear on that from the original post.

        • Sorry! I linked to the article where I reviewed them a while back.

  • Do you really think it’s the lack of a thru-axle that’s causing rub on the stays? Seems like rim and spoke stiffness, bearing preload, not to mention tire stiffness, would have a much larger effect than any play between the hub and dropout or lack of stiffness in the dropout or rear triangle itself.

    • I have run a similar setup with similar tubing but with a thur-axle and yes, I’d say I’m confident in that lack of a “locked in” stiffness is a factor. I’m confident but I could be wrong.

      • naisemaj

        you could always try a 9 mil thru axle as well, I use one on my hardtail and I really liked the way it stiffened that interface up. Not sure if those hubs have a conversion to that though

    • black cat bicycles

      by itself, a qr axle is much less laterally stiff than a thru-axle, for sure. the problem being is there really isn’t a way to isolate the flex one might feel when pedaling hard, from the spring you feel that propels you out of a corner, and gives that decidedly steel ride: it’s the same “flex.” i can make a bike with zero flex when pedaling, even with a qr axle. easy peasy; it will ride like a ton of bricks though. on a sus bike, a laterally rigid swingarm is very important, whereas on a hardtail, that flex, or spring, is what keeps the wheels planted and the rider somewhat isolated from the shock of the road/trail.
      the perfect amount of flex is what separates the wheat from the chaff, and is what steel frame builders are searching for with every bike we make.
      personally, i’d put up with a touch of rubbing now and then while pedaling really hard to have a bike that descends like magic.

  • Isaac Jarrett

    Fuuuuuuuuuuuuuck that bike is PERFECT!!!! Email sent to Black Cat!

  • lov2bikenrock

    Where are those tires available? I’m loving the sidewalls.

  • poiuytman

    Ack, past the max line on those carbon rails!

    • I got a handwritten note allowing me to do that.

  • Luke Doney


  • Eric Spinney

    I think we all need to be honest with ourselves here and agree that any sort of downfalls this frame could possibly have to any individuals riding style, is heavily overshadowed by how pretty the bike is.

  • Andre

    To each his own, but to me, that RS-1 looks (as far as aesthetics go) way out of place on that bike.

    • I agree. I also think the gumwalls are too much and draw attention away from the frame. I think A RS SID and regular Ardent’s would enhance the bike

  • KT

    WOW this thing is amazing! Very nice rig. I love that stem as well. Would there be a frame option that comes with a matching rigid fork for the purists out there?

  • Tyler Morin

    Definitely interested to hear your thoughts on the brakes and what makes them better than the XTR’s!

  • tracyjwilbanks

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  • Jordan Mackinnon

    Choice build. I love the super subtle gusset on the head tube cluster. Those brakes, that fork… *fans self*

  • Adam Miller

    @blackcatbicycles:disqus This is completely sick all around but I think my favorite detail is the Viking ship rear dropouts:

  • Rudy Luthi

    @johnprolly:disqus Is this the bike? I think I saw you on Saturday with your ‘Cruiser and Santa Cruz on your way up the 110.

    • Yep. I saw you. Waved from the 110 as you were exiting into South Pas.