XM Carbon Speed Race Frame - The wish list

[Requiem84]

431 / 544 in 56… that will make it a bike rideable for a very limited audience.

[Pistonbroke]

Tricky isn't it.
Probably the path to commercial success is to make what is effectively an SL8 sworks clone with a few bells and whistles. It's going to be light, strong and relatively fast. Light weight sells as we know, and there's quite a few of us over here from Weightweenies so we understand that siren call.
Then there's the cutting edge of things like the Ridley/Dare(Simplon maybe) that will probably be faster if it works for you, but won't appeal to so many people... Although I suspect lots of riders could adapt and feel comfortable with this type of frame and it's only fear of the unknown (and £££) that's stopping them trying.
It really wouldn't surprise me if the SL9 ( Venge Evolution, whatever) runs along these lines.

[Sakizashi]

431 / 544 in 56… that will make it a bike rideable for a very limited audience.

Is the Ridley Noah Fast 3.0 also considered a bike only rideable for a limited audience? That design could have been a little longer, given the number of pro riders on 140mm, 150mm, and 160mm stems. This is about 1cm longer in the 56 than that bike.

IMO, riders who want this kind of bike need to get used to a different riding position with a sub-30-degree back angle and open hips. From experience, this kind of geo should be rideable by folks who are decently fit in the 3 w/kg range and are relatively flexible. Even if the market is limited, this is supposed to be a breakaway-style road race bike, so the number of people actually riding it in a way that aligns with this design goal would be low. I don't plan to own the business case for this kind of bike design, so that's someone else's problem 

Like the Noah Fast 3.0, my geo ran into trouble with the larger sizes. I wanted to make a 61 for the size chart, but it was impossible to pursue the design theory without running afoul of UCI rules or compressing the front end with a very steep HTA and compromising the handling. So like the Noah, my geo tops out at a 58.

[patliean1]

Why the recessed head tube similar to a TT bike?

Not that I'm for or against it. Especially if the frame stack isn't crazy low, or if the frame included a positive rising handlebar like on the Cervelo S5.

[Requiem84]

Is the Ridley Noah Fast 3.0 also considered a bike only rideable for a limited audience? That design could have been a little longer, given the number of pro riders on 140mm, 150mm, and 160mm stems. This is about 1cm longer in the 56 than that bike.

IMO, riders who want this kind of bike need to get used to a different riding position with a sub-30-degree back angle and open hips. From experience, this kind of geo should be rideable by folks who are decently fit in the 3 w/kg range and are relatively flexible. Even if the market is limited, this is supposed to be a breakaway-style road race bike, so the number of people actually riding it in a way that aligns with this design goal would be low. I don't plan to own the business case for this kind of bike design, so that's someone else's problem 

Like the Noah Fast 3.0, my geo ran into trouble with the larger sizes. I wanted to make a 61 for the size chart, but it was impossible to pursue the design theory without running afoul of UCI rules or compressing the front end with a very steep HTA and compromising the handling. So like the Noah, my geo tops out at a 58.

Noah Fast 3.0 M (56) is 412 reach, 570 stack.

You are proposing 20mm longer, 24mm lower. In geo world that’s huge. If you want a bike suitable for commercialization ánd the more serious amateurs copying the Noah is much more sensible.

Your suggested geo is wild. Nice for a personal project tho.

[toxin]

Why the recessed head tube similar to a TT bike?

Not that I'm for or against it. Especially if the frame stack isn't crazy low, or if the frame included a positive rising handlebar like on the Cervelo S5.

In essence it simply makes the top tube a continuation of the head tube because I don't like the aesthetics of of a concave transition from the head tube to top tube. The idea is that the negative space would be filled by a custom headset cover, similar to the VB-368. It and the Van Rysel RCR-F were the main inspirations behind this section of design. It's not deep enough to fit a non-custom stem in there regardless.

This happened mostly because I wanted a curved top tube. With a straight top tube, at maybe even higher slope angle, this effect could be reduced or even entirely eliminated. I also think that this makes a tall spacer stack less disruptive to the aesthetics of a bike. Look at some pics of the Noah Fast 3.0 with spacers for examples, although that one suffers a bit cause of the stem design.

[Sakizashi]

Noah Fast 3.0 M (56) is 412 reach, 570 stack.

You are proposing 20mm longer, 24mm lower. In geo world that’s huge. If you want a bike suitable for commercialization ánd the more serious amateurs copying the Noah is much more sensible.

Your suggested geo is wild. Nice for a personal project tho.

You are looking at the Noah 3.0, not the Noah Fast 3.0.

The Noah Fast 3.0 M is 420mm Reach, 541mm Stack.

I am proposing 431mm reach and 544mm stack. My target at the M size was the removal of a 5mm spacer and running a one size shorter stem; I didn't quite get there, given the desire to keep numbers round elsewhere, but it's close enough for a rough draft.

[toxin]

Here's the geometry I based this on. Note that this fork crown design requires a significantly longer than normal effective fork length to get any tyre clearance.

[Sakizashi]

In essence it simply makes the top tube a continuation of the head tube because I don't like the aesthetics of of a concave transition from the head tube to top tube. The idea is that the negative space would be filled by a custom headset cover, similar to the VB-368. It and the Van Rysel RCR-F were the main inspirations behind this section of design. It's not deep enough to fit a non-custom stem in there regardless.

I really like this design because it can allow you to achieve the slammed look while hiding a 5mm spacer. Attached is a photo of a prototype headset cover for the Haro Rivette that does just that, its hiding a 5mm ACR spacer which I think is the same as the XMCS "Revenger" bar. That design might need some tweaks to fit an aero bike like this one, but it would mean that you could easily get to 25mm of spacers + the 5mm headset cover and still have the look be very normal.

Here's the geometry I based this on. Note that this fork crown design requires a significantly longer than normal effective fork length to get any tyre clearance.

Yeah, this geo (and the Dare VA) is more likely to align with the next-gen aero bike frames from the big brands, based on what I have seen. Where it gets weird is that the UnoX Ridleys from 2025 were set up extremely long, and many had 5-15mm spacers. So the question for the commercialization of a race bike is: do you swing for the fences based on what you see the pros and high-level racers are doing? Or do you go to where you think the other brands are going, knowing full well they are crawling, not walking, towards these more aero fits?

Luckily, I don't have to make that call. Just doing it for a handlebar was stressful enough.

[toxin]

Yeah, with my design you could get away with a good 20mm of spacers without significantly compromising the silhuette of a bike. I guess another avenue where this could take you is multiple headset covers of varying height. You can have a standard low stack cover for those who can handle those positions and a second high stack cover for the more common rider that still makes it look like a normal bike, without the stigma of spacers. On my design that would net you a 24 mm stack increase and 7.5 mm reach decrease.

[Requiem84]

You are looking at the Noah 3.0, not the Noah Fast 3.0.

The Noah Fast 3.0 M is 420mm Reach, 541mm Stack.

I am proposing 431mm reach and 544mm stack. My target at the M size was the removal of a 5mm spacer and running a one size shorter stem; I didn't quite get there, given the desire to keep numbers round elsewhere, but it's close enough for a rough draft.

Oh boy did I get that wrong - thanks for setting me straight.

But still; it’s a very very aggressive / on the edge geo and you are going a step further. Why not keep the reach, or reduce a bit, and increase the stack?

[aeroskiii]

IMO make the tubes that hit the wind (headtube, upper downtube, seatube, fork blades etc) very thin and pretty deep (50mm+) and try to get frameweight around 850g in a 54. It would be nice to have the frame optimized around the trek style aero bottle/cage system but its not a necessity. The bayonet fork, wide fork blades, 32mm+ tire clearance, and unorthodox geometry should be ignored imo, its a race bike.

[Sakizashi]

Oh boy did I get that wrong - thanks for setting me straight.

But still; it’s a very very aggressive / on the edge geo and you are going a step further. Why not keep the reach, or reduce a bit, and increase the stack?

Ultimately, it's a product strategy question for a company trying to break into competitive racing bikes. While some big factories can fast-follow and copy anything, I am not sure XMCS does. A small company with big ambitions needs to decide whether to play it safe, follow the market leaders (e.g., something more like the Dare or New Factor), or push the envelope with something like this, essentially trying to release a next-gen Noah Fast 3.0. Glad I don't need to make this call, but I think of the design I proposed as the third track.

The rationale for this design is simple. A design like the one I shared allows for two things. First, it seeks to balance the handling with longer and forward fit by moving the front wheel forward and the BB down and back. This should help keep the handling more neutral when descending for riders currently using a fit like this. Second, if this really is a bike for pros; based on what we saw from UnoX this is probably needed for the long and longer classics race fits we saw in 2025. You can see in some of their videos that, even with 160mm stems, some of their riders struggled because the bikes weren't quite long enough for the breakaway position. We did not see any really short stems, so there is no indication that this design needs less reach, and quite a bit suggests more is needed. The stack is also adjusted based on the spacers seen on those riders' stacks and how we see the Ridley being built up in the real world.

Obviously, this use case is a niche market and isn't for the average amateur or fondo racer. It's not optimized for grand tour-style riders either, but instead literally is trying to reflect UnoX's setups. It's likely also very relevant to the niche market that does crit/kermesse and one-day road races. That doesn't mean it couldn't work for grand-tour all-rounders.

For example:

• Pogacar's Y1RS is a medium (sized up from his previous bikes) had a 145mm stem on it at the Tour and WCs this year. On the geo I put together, a rider looking to replicate that position would be on a 100mm stem or a 110mm stem on a size M.
• Remco is on a 115mm custom Roval Bar stem (for stem angle) on his Tarmac SL8. A rider replicating that position should be able to do it on the proposed Size XS with a 100mm stem and like 10mm-15mm of spacers

Those two top world tour pros already have solutions that are heavily optimized for them. I don't think a bike like this would offer them a significant advantage over their current setups, so they probably wouldn't take full advantage of what a frame like this could offer. However, they would still fit well on this kind of geometry with some added flexibility to go longer in Pogacar's case or lower in Remco's case.

This is all theoretical, so why not dream big?

Edit: I should also add that the geo chart I made accounted for trying to keep costs down with one fork mold AND reusing the "Revenger" bar stem, as I think that bar stem was also built around a 72.5deg HTA (though I am not sure).

[toxin]

IMO make the tubes that hit the wind (headtube, upper downtube, seatube, fork blades etc) very thin and pretty deep (50mm+) and try to get frameweight around 850g in a 54.

That's not really realistic. You can go sorta deep in the front and really shallow in the back to min/max weight and aero. In the same vein, thinner tube profiles need more material to maintain stiffness. My goal was to make something that could be made under 1000g in medium sizes. I don't really think I succeeded on that front. I'm guessing my design would need more than that. There's also the problem of choosing which yaw angles you want to design for. Tube profiles with a sharper taper and narrower trailing edges will perform better at low yaw, while blunter tapers with wider trailing edges will be better at high yaw. It's all a game of trade-offs.

It would be nice to have the frame optimized around the trek style aero bottle/cage system but its not a necessity.

I had round bottles in mind, but looking at the specs for Trek's bottles, I was pretty surprised that their listed dimensions don't really put them any narrower than standard round bottles, In which case there's not really much sense designing especially around them, unless you made your own or targeted a narrower system (I think Incolor's bottles are a bit narrower). In the end, as long as you have a wide enough down-tube, it would mostly come down to positioning the mounting bolts to place the bottles closely together.

The bayonet fork, wide fork blades, 32mm+ tire clearance, and unorthodox geometry should be ignored imo, its a race bike.

Bayonet fork just wouldn't be commercially viable, yes. Tyre clearance was overdone on the face of it, yes, but the actual gain of big clearance at the front is less interaction between the fork and wheels. At the rear, having a shallower seat tube will help with reducing in-plane stiffness and improving comfort. That's where the wide clearance originally came from, but because of the extremely steep seat angle, I didn't really end up where I originally intended. Reducing clearance would definitely help with chain stay design, which would help drop some weight. In a final version, I would increase "clearance" on the seat tube and reduce it on the chain stays. Absolutely don't agree with you on geometry. The whole point of a proper race bike is that it shouldn't have conventional geometry. IMO most "race" bikes these days aren't fit for purpose in that aspect.
 

[toxin]

Hand drawn rendition of some changes I'd make. Mostly focused on dropping weight by giving the rear some Incolor SSR and Scott Foil treatment.