Long Teng / Mondince aero frame FM126

[bigApple]

Latest update i have is:
We will have size 54cm in 20 days. The mold is almost finished.
And as for the handlebar, we will have 380-90/100, 400-100/110; 420-110/120mm

Unfortunately, no Aero sizes. I need 380/120 mm.
The handlebar they offer is too wide or too short.

[casper.f]

GEOMETRY WARNING: Mondince FM126 (Sizes 56+)

While the new Mondince FM126 looks like a standard open-mold aero racer, if you are a taller rider looking at sizes 56, 58, or 61, there is a critical detail in the geometry chart that will drastically affect the ride.

On paper, the geometry looks very similar to the Specialized Tarmac SL8. However, due to a specific choice with the fork offset, the handling on the larger sizes will be significantly different (and likely much twitchier) than you might expect.

The Issue: Fork Rake vs. Head Angle Most manufacturers shorten the fork rake (offset) on large frames to keep the bike stable as the head angle gets steeper.

Specialized: Uses 47mm rake for sizes <54, but switches to 44mm for sizes 54+.
Mondince: Uses a 47mm rake fork across ALL sizes (I suspect saving on mould costs).

When you combine that relatively long 47mm rake with the steep 74° head angle of the Size 61, the "Trail" figure drops to dangerous lows (sub-50mm), essentially giving you track-bike steering on a large road frame.

Bike Model (Size)	Head Angle	Fork Rake	Trail (Approx)	Handling Character
Mondince FM126 (61)	74.0°	47mm	~49mm	Extremely Twitchy / Unstable
Specialized Tarmac SL8 (61)	74.0°	44mm	~52mm	Very Agile / Reactive
Trek Madone Gen 8 (XL)	73.9°	41mm	~57mm	Neutral Race Stability
Factor Ostro VAM (61)	73.3°	43mm	~58mm	Neutral Race Stability
Canyon Aeroad CFR (XL)	73.25°	38mm	~64mm	Very Stable / Planted

Why Specialized is also an outlier (but Mondince is worse) You'll notice the Tarmac SL8 is also quite low trail (~52mm) compared to the "safe" 57mm+ of Trek or Canyon. I suspect Specialized does this intentionally to make their large bikes feel agile, counteracting the high center of gravity of a tall rider. But even Specialized knows when to stop. They invest in a specific 44mm offset fork to keep the trail above 50mm. Mondince seemingly skipped this step to save on a second fork mold, pushing the handling from "agile" to "unstable."

Can they fix it? Since this frame is reportedly in a "Soft Launch", Mondince actually has a chance to fix this for the larger molds before they are final.

The Fix: They don't even need a new fork. If they simply slackened the Head Tube Angle to ~73° on sizes 56+, the existing 47mm fork would yield a perfect ~56mm of trail.

The Result: This would transform the bike from a nervous outlier into a stable, neutral racer comparable to the Trek Madone or Factor Ostro.

Conclusion So don't think you will get "one bike to do it all" just yet.
-Stack/Reach: Seems good
-Aero: Seems aero enough
-Weight: Seems light enough
-Handling: Major Red Flag for sizes 56+

[casper.f]

Notes:
-I know geometry personal preference for a large part, I am sorry if my opinion comes across as factual (altough almost all of it is factual)

-I know different use-cases require different geometries, but this is completly different bike in different sizes (from a balanced road bike to a hyper-twitchy crit machine only for the extremely experienced)

-I have contacted Mondince about my concerns via Whatsapp and will keep you updated

[casper.f]

Although this isn’t the response I was hoping for: I really wanted to love this bike, but it’s a no for me.

[jfcb]

I think I already brought it up earlier in this thread that I don't understand why they go that steep in the larger sizes. It's all ok for a flat solo time trial, but in scenarios like cornering, bike handling in groups and descending it would be a no go for me since the bike very likely will feel to twitchy and nervous.
So yes, I share your thoughts and concerns. Keeping it at 73.3deg for sizes L and XL would make more sense. Geometry is something where those chinese brands lack experience. Compared to western brands, there are not many engineers or designers in those companies who are pasionate cyclists themselves and understand how bike geometry affects bike handling.

[casper.f]

I think I already brought it up earlier in this thread that I don't understand why they go that steep in the larger sizes. It's all ok for a flat solo time trial, but in scenarios like cornering, bike handling in groups and descending it would be a no go for me since the bike very likely will feel to twitchy and nervous.
So yes, I share your thoughts and concerns. Keeping it at 73.3deg for sizes L and XL would make more sense. Geometry is something where those chinese brands lack experience. Compared to western brands, there are not many engineers or designers in those companies who are pasionate cyclists themselves and understand how bike geometry affects bike handling.

The only way to make the 74° HT work is with a different fork but they probably dont want to invest money in a new fork mould.
If they are willing to change the HT to something slacker, they can make the fork work but then they dont have 1:1 SL8 geometry (change one thing, open a can of worms, what they already did with the fork offset lol)

If i was an engineer i would do the following for the size 61 (my size but concepts can transfer to all larger size):
-74° -> 73° HT (pushes front axle +-10mm, balances trail, makes bike more stable)
-410mm ->415-420mm chainstay lenght (corrects weight distribution from making HT slacker, makes the bike more "sluggish")

This results in a bike with +-17mm wheelbase and more trail (from 49 to +-57 mm) making it way more predictable
This wont make the bike too sluggish tough! wheelbase would be comparable to XL Aeroad (1029mm) compared to 1032mm proposal

I know this is all armchair-engineer but it seems like they also hire them at Mondince, doing a copy-past job half-ass.

[Sakizashi]

GEOMETRY WARNING: Mondince FM126 (Sizes 56+)

While the new Mondince FM126 looks like a standard open-mold aero racer, if you are a taller rider looking at sizes 56, 58, or 61, there is a critical detail in the geometry chart that will drastically affect the ride.

On paper, the geometry looks very similar to the Specialized Tarmac SL8. However, due to a specific choice with the fork offset, the handling on the larger sizes will be significantly different (and likely much twitchier) than you might expect.

The Issue: Fork Rake vs. Head Angle Most manufacturers shorten the fork rake (offset) on large frames to keep the bike stable as the head angle gets steeper.

Specialized: Uses 47mm rake for sizes <54, but switches to 44mm for sizes 54+.
Mondince: Uses a 47mm rake fork across ALL sizes (I suspect saving on mould costs).

When you combine that relatively long 47mm rake with the steep 74° head angle of the Size 61, the "Trail" figure drops to dangerous lows (sub-50mm), essentially giving you track-bike steering on a large road frame.

Bike Model (Size)	Head Angle	Fork Rake	Trail (Approx)	Handling Character
Mondince FM126 (61)	74.0°	47mm	~49mm	Extremely Twitchy / Unstable
Specialized Tarmac SL8 (61)	74.0°	44mm	~52mm	Very Agile / Reactive
Trek Madone Gen 8 (XL)	73.9°	41mm	~57mm	Neutral Race Stability
Factor Ostro VAM (61)	73.3°	43mm	~58mm	Neutral Race Stability
Canyon Aeroad CFR (XL)	73.25°	38mm	~64mm	Very Stable / Planted

Why Specialized is also an outlier (but Mondince is worse) You'll notice the Tarmac SL8 is also quite low trail (~52mm) compared to the "safe" 57mm+ of Trek or Canyon. I suspect Specialized does this intentionally to make their large bikes feel agile, counteracting the high center of gravity of a tall rider. But even Specialized knows when to stop. They invest in a specific 44mm offset fork to keep the trail above 50mm. Mondince seemingly skipped this step to save on a second fork mold, pushing the handling from "agile" to "unstable."

Can they fix it? Since this frame is reportedly in a "Soft Launch", Mondince actually has a chance to fix this for the larger molds before they are final.

The Fix: They don't even need a new fork. If they simply slackened the Head Tube Angle to ~73° on sizes 56+, the existing 47mm fork would yield a perfect ~56mm of trail.

The Result: This would transform the bike from a nervous outlier into a stable, neutral racer comparable to the Trek Madone or Factor Ostro.

Conclusion So don't think you will get "one bike to do it all" just yet.
-Stack/Reach: Seems good
-Aero: Seems aero enough
-Weight: Seems light enough
-Handling: Major Red Flag for sizes 56+

Hey, I think it's worth taking a step back here and understanding what trail is or isn't.

Trail is not a primary driver when modeling the handling limits or characteristics of a 2-wheeled system. Trail governs how a bike feels to control, particularly during turn-in when you initiate a countersteer. There are people like me who prefer the feel of a lower-trail bike geometry, particularly with lower-pressure tires we use on the road now, as those increase what is known as pneumatic trail and have a similar feeling effect to mechanical trail. Another way to balance lower trail in terms of feel is to lower the system's center of mass, which Mondinice is also not doing, likely because they want to preserve crank clearance.

HTA, Wheelbase, and F/R weight distribution are primary drivers with regards to the handling limits of a 2-wheeled system, and it's clear to me that for large road bikes, designers consistently balance those three similarly. Those are not being done differently than other designs for this bike. Of course, ideally, you have 2-3 fork rake settings so you can get both the feel and handling you want, but a 52mm or even 49mm trail isn't the end of the world, particularly if you use larger tires at lower pressure. Even better would be to offer multiple chainstay lengths while keeping the HTA relatively consistent, but that isn't common on carbon bikes for cost reasons.

I do not think this bike design is a sign of amateur hour or a half assed job at Mondinice, just a reflection of their budget constraints.

[casper.f]

Hey, I think it's worth taking a step back here and understanding what trail is or isn't.

Trail is not a primary driver when modeling the handling limits or characteristics of a 2-wheeled system. Trail governs how a bike feels to control, particularly during turn-in when you initiate a countersteer.

I think you are significantly understating the role of trail here.

While you are correct that wheelbase and weight distribution define the ultimate grip limits (physics), Trail is the primary driver of directional stability (dynamics).

My warning isn't about the bike sliding out at the limit. It's about the caster effect: the self-centering force that keeps a bike stable at speed. A trail of ~49mm provides very little of this self-correcting force. This doesn't mean the bike will crash, but it means it requires constant, active micro-corrections to stay on line.

There are people like me who prefer the feel of a lower-trail bike geometry, particularly with lower-pressure tires we use on the road now, as those increase what is known as pneumatic trail and have a similar feeling effect to mechanical trail. Another way to balance lower trail in terms of feel is to lower the system's center of mass, which Mondinice is also not doing, likely because they want to preserve crank clearance.

HTA, Wheelbase, and F/R weight distribution are primary drivers with regards to the handling limits of a 2-wheeled system, and it's clear to me that for large road bikes, designers consistently balance those three similarly. Those are not being done differently than other designs for this bike. Of course, ideally, you have 2-3 fork rake settings so you can get both the feel and handling you want, but a 52mm or even 49mm trail isn't the end of the world, particularly if you use larger tires at lower pressure. Even better would be to offer multiple chainstay lengths while keeping the HTA relatively consistent, but that isn't common on carbon bikes for cost reasons.

Fair points on pneumatic trail; modern tires definitely help add stability back into the system.

However, the FM126 remains a massive outlier. Sub-50mm mechanical trail on a size 61 is significantly sharper than any major western road bike. My post serves as a warning for buyers expecting the neutral, "all-round" handling of a Tarmac SL8 will be disappointed by the nervousness of the steering.

I do not think this bike design is a sign of amateur hour or a half assed job at Mondinice, just a reflection of their budget constraints.

There is also a fine line between cost-saving and incompetent engineering. Using a single fork mold to save money is understandable, but they could have simply slackened the Head Tube Angle to ~73° to compensate. That adjustment costs nothing in production. Retaining a steep 74° HTA with that specific fork offset isn't a budget constraint; it’s a failure to check the math.

[Sakizashi]

I think you are significantly understating the role of trail here.

While you are correct that wheelbase and weight distribution define the ultimate grip limits (physics), Trail is the primary driver of directional stability (dynamics).

Have you actually tried to build a model of this? Trail ends up being a secondary variable in your capsize model. The primary one most related to trail is HTA, which makes sense when you realize that trail is actually a calculated property that relates HTA to front center (as well as COM height to some extent)

This does not entirely excuse this design as its still less than ideal. 74 deg is a compromise, not something that is dangerous, and neither is 50mm of mechanical trail. You can't just slacken the HTA without lengthening the chainstay, as you are changing the bike's weight distribution. IMO, this is usually a worse outcome than an HTA that is not the ideal number. Balancing tradeoffs is the challenge here.

For bike frames made in single-piece molds, I do hope we start to see more size-specific rear triangle designs.

[casper.f]

Have you actually tried to build a model of this? Trail ends up being a secondary variable in your capsize model...

Fair points on the physics modeling.
* You are right that in a pure physics 'capsize model,' trail is just one variable among many.
* Yes, Trail is mathematically a derivative of HTA and Offset.
* We agree this is a compromise design, not necessarily a 'broken' one.

You can't just slacken the HTA without lengthening the chainstay, as you are changing the bike's weight distribution. IMO, this is usually a worse outcome than an HTA that is not the ideal number. Balancing tradeoffs is the challenge here.

Here is where I disagree. Your concern that slackening the HTA without lengthening the chainstays leads to a "worse outcome" is theoretically sound, but it is practically disproven by the market.

I compiled the geometry for the Size 61/XL equivalents of current aero-bikes. The industry consensus is actually to do exactly what you described as a negative trade-off: combine a slacker HTA (~73-73.5°) with short chainstays (~410mm).

Bike Model (Size 61/XL)	HTA	Fork Offset	Chainstay	Trail (Approx)
Factor Ostro VAM	73.3°	43 mm	410 mm	57 mm
Canyon Aeroad CFR	73.5°	44 mm	415 mm	56 mm
Scott Foil RC	73.3°	45 mm	412 mm	55 mm
Pinarello Dogma F	73.4°	43 mm	411 mm	58 mm
Specialized Tarmac SL8	74.0°	44 mm	410 mm	52 mm
Trek Madone Gen 8	73.9°	40 mm	412 mm	57 mm
Cervélo S5	73.5°	43.5 mm	405 mm	56 mm
Cannondale SuperSix	73.0°	45 mm	410 mm	57 mm
Bianchi Oltre RC	73.0°	43 mm	412 mm	59 mm
Colnago V4Rs	73.1°	43 mm	408 mm	58 mm
MARKET AVERAGE	73.4°	43.4 mm	410.5 mm	~56.5 mm

(I did not cherry-pick these; these are the current flagships. If I made any mistakes, please let me know and I will edit, some figures like offset have conflicting/hard to find data).

Virtually no one (except Specialized) is running a 74° HTA on a size 61, and even Specialized pays for a custom 44mm offset fork to make it work. Everyone else slacks the head angle to ~73.4° and keeps the chainstays tight at ~410mm.

This highlights why the current FM126 is such an outlier. It tries to hold the steep HTA of the Tarmac but lacks the correct fork offset to support it. At first I didn't believe it myself. I assumed there was a compromise somewhere I was missing, but the FM126 really is the extreme outlier here.

Scenario	HTA	Offset	Trail	Notes
Current FM126 (61)	74°	47 mm	~49 mm	Current Setup (Unstable outlier)
Ideal FM126 (Change HTA)	73.3°	47 mm	~53 mm	Uses existing fork mold
Ideal FM126 (Change Fork)	74°	44 mm	~52 mm	Requires new fork mold

If Mondince simply slackened the HTA to 73.3 (Option 1), the bike would land almost exactly on the market averages. The resulting trail would be ~53mm—still fast and agile (similar to Factor/Pinarello), but far safer than the sub-50mm geometry they have now.

That wouldn't be a "worse outcome" for weight distribution; it would just be a normal, modern road bike.

@Sakizashi I don't want to argue for the sake of it, or have a useless discussion about choice of words. I just want to share my findings and opinions so people don't buy a cat in a bag!

[Sakizashi]

I know you just made a high effort post, and I promise I am not trying to move the goalposts on you, but what you care about with regards to chainstay length is how it affects the location of the wheels' contact points with the ground, with relation to the rider's center of mass. You just did the wrong analysis.

When doing the right analysis, you need to take into account the wheelbase relative to the BB, and the saddle position dictated by the STA. On a single design, I can tell you that the front-center contribution to the wheel base goes up if you slacken the HT and make no other changes, but I can't look at just an HTA and assume that a slacker one has a longer front center.

Here is where I disagree. Your concern that slackening the HTA without lengthening the chainstays leads to a "worse outcome" is theoretically sound, but it is practically disproven by the market.

I compiled the geometry for the Size 61/XL equivalents of current aero-bikes. The industry consensus is actually to do exactly what you described as a negative trade-off: combine a slacker HTA (~73-73.5°) with short chainstays (~410mm).

Fit data is antithetical to the physics behind bikes at the extremes of the size ranges, both small and large. This is explicitly done to cut costs. I am not here to defend Mondinice and their design, far from it. However, the bikes in your chart are making more than just HTA and fork rake, etc, to make their designs work. You will see very different curves applied to the Stack to Reach ratio across these brands, too, if you try to map those; it's just part of how different engineers accept slightly different compromises.

I guess since we agree that the 61 size likely should sink low on someone's purchasing list, my objection was simply to using the wrong analysis to accuse the engineers at Mondinice of being bad at their jobs. I just see them as being held to a really tight budget.

[Rolle2k]

I will probably order this frame now, in size 54. Just have a few questions regarding paint to them. Trail wont be a problem in sz 54. It will probably be around 54mm with 32c tires if i calculated correctly.
The only problem is that i dont even know if i will have money/parts to finish it for the summer 😅😅 so expensive if one wants wireless 2x12 sram or upcoming Shimano ultegra.

Mondince are waiting for finalizing size 54 prototype, then after that i will put in an order. Will probably mimic the 3T RaceMax in its yellow/black coloring scheme.

[Serge_K]

Videos from Jack of the prototype.
this frame obviously isn't monocoque.   <--- Turns out, it should say ONE PIECE MONOCOQUE. The original frame was supposed to come from one mould. This is coming from 2 moulds. How much that matters to the end customer is beyond my pay grade.
the fork looks fast
i like the BB area, looks stiff
I like that the downtube looks fast.
it looks like my LT268, but meaner, i like it.

[Sakizashi]

Videos from Jack of the prototype.
this frame obviously isn't monocoque.
the fork looks fast
i like the BB area, looks stiff
I like that the downtube looks fast.
it looks like my LT268, but meaner, i like it.

The frame literally is monocoque.

https://en.wikipedia.org/wiki/Monocoque

Stop misusing the term, I am sure there are people very confused about this. Particularly those who actually make stuff.

[Serge_K]

The frame literally is monocoque.

https://en.wikipedia.org/wiki/Monocoque

Stop misusing the term, I am sure there are people very confused about this. Particularly those who actually make stuff.

For bikes, isn't monocoque when the 2 triangles aren't glued together, but the whole frames comes from 1 mold? In the video, isn't it clear that the triangles are glued together?

I'd bet that people on here have on average the same understanding as me on that point, so if that's wrong, please come off your high horse and enlighten us peasants instead of smugly pointing to old ass plane pictures on wikipedia.