Bufort
New Member
- Mar 26, 2026
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What stem doesn't spin if you don't tighten it up?!
Weird Reversed Stem Geo / Chat
- Thread starter Rob Rides EMTB
- Start date
DH onesWhat stem doesn't spin if you don't tighten it up?!
Agree to disagree,
My riser bar has a vertical rise of 70mm on a -50mm stem on 63deg headtube angle.
Center of grips is -40..-50mm behind center of steerer tube.
Bufort
New Member
- Mar 26, 2026
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You have your bars unusually rolled forwards then. The point of the short 15-18mm stems is that bars are usually angled rearwards slightly, putting the grip 15-18mm behind the clamp, inline with the steerer.
With your bars like this, when you had a normal forward facing 50mm stem, your grips would have been at ~55mm, whereas most other people's grips would have been at ~35mm.
Bars have printed on indicator marks of rotation, with 0 deg aligned with horizontal on my bike, if anythig 0-deg-mark is pointing a few deg upwards from horizontal.
The angle you have on the bars in your printout, where does it origine from ?
Bufort
New Member
- Mar 26, 2026
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The 0 mark on bars isn't the 'correct' setting, it's simply the angle bars have their rise measured from. But more importantly, they can't be used to compare two different bars, as the sweep on bars isn't just 2 dimensional, it's 3D, so the angle that the bars 'go up' from the clamp doesn't necessarily have any relevance to the final angle of the grips.
This image shows two bars (A: 45mm rise, little backsweep, more upsweep, B: 35mm rise, more backsweep, little upsweep) (top) but both bars can be positioned so the grips are at exactly the same position with the same angle and rise (bottom), but the angle at the clamp is completely different. So the point I'm trying to make is that I only pay attention to the end position of the grip, and I would never pay any attention to the angle marks, unless you're simply trying to get bars back to the same position when taking your bars/stem off. And with that in mind, most grips are 10-20mm behind the bar clamp.
I got my angles from looking at all mine and my friends bikes, and various images of bikes online, and coupled with people like Rulezman who said they made their 15mm & 18mm stems to put the grips inline with the steerer, these numbers check out.
DirkWisely
Well-known member
Just took this stem out for a very long ride. Pushing 40 miles I think. Unsure as my phone died relatively early and I got lost. I'm definitely used to it now. It felt good and confidence inspiring sending it through lots of technical chunk.
BeMoreBikes
New Member
- Mar 4, 2026
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Awesome! I’m glad it’s coming along nicely! It will only keep getting better as you spend more time getting you and the bike dialed into it.
stepping-razor
New Member
- Mar 17, 2026
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but shouldn't the f/r ratio be between front-center (bb to front hub) and rear-center (bb to rear hub)? and not reach-chainstay?
sjturner2112
Member
What am I missing here? My 455 reach Wild would need a 250 chain stay??? 455/250 =1.82
"Critical F/R ratio: Reach ÷ chainstay ≈ 1.8 identified as the threshold. ntm95 running a Dreadnaught v2 with 471mm reach confirmed this as the tipping point — below 1.8, the front end stays under-loaded regardless of bar height."
"Critical F/R ratio: Reach ÷ chainstay ≈ 1.8 identified as the threshold. ntm95 running a Dreadnaught v2 with 471mm reach confirmed this as the tipping point — below 1.8, the front end stays under-loaded regardless of bar height."
sjturner2112
Member
I’m running an Intend +25mm stem and am enjoying the reduction but I want more bar rise and am limited to 20mm because of the clamp.
I’m considering a zero length stem and 50mm bars.
I’m 5’8” / 173cm tall (all in proportion!) and ride a medium Whyte Kado S with 460mm reach, 634mm stack, 1243 wheelbase and 450mm rear.
Thinking about a Null-Vorbau - Nullvorbau Vorbau Zero Stem Mountainbike Enduro stem and 50mm rise bars. Any thoughts on this set-up with my bike stats? @BeMoreBikes
Cheers!
I’m considering a zero length stem and 50mm bars.
I’m 5’8” / 173cm tall (all in proportion!) and ride a medium Whyte Kado S with 460mm reach, 634mm stack, 1243 wheelbase and 450mm rear.
Thinking about a Null-Vorbau - Nullvorbau Vorbau Zero Stem Mountainbike Enduro stem and 50mm rise bars. Any thoughts on this set-up with my bike stats? @BeMoreBikes
Cheers!
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Sorry answered a bit too quick.
(Wheelbase - chainstays) / chainstays
sjturner2112
Member
reach impacts the wheelbase length from the BB (with the fork angle, offset & stack).
Bike comparison: Orbea Wild (full 29") 2025 vs Orbea Wild (full 29") 2025
Use this app to compare bike geometries of different manufacturers with each other, in order to determine the most suitable bike for your personal requirements.
If this indeed is this Wild, your ratio can be calculated as weel from the RTF value in the above page, i.e 64.22%/35.78% = 1.794.
A L one is 65.05%/34.95%=1.861. The chainstays don't move between the two sizes so a longer reach then gives a higher ratio.
Reach has an effect on body position.
It does not alter the f/r ratio of the bike.
Longer reach is used to compensate for a higher f/r ratio. The ibis hd6 is a pretty good example of this.
Loamranger
Active member
https://theradavist.com/zero-offset-and-reduced-offset-mountain-bike-stemsbrands negative and zero offset stems.
BeMoreBikes
New Member
- Mar 4, 2026
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I’d say go for the Gen 2 90mm RR stem full -15mm offset, and likely even plus some spacers. I’m also 5’8”, and I would probably run that bike with the Gen 2 90mm RR stem and 60mm rise bars maybe even plus a few spacers for my preferences. You are within the range for sizing on that frame that I would want you to be on as I typically go for about 460mm - 480mm as a workable range at my height for the Gen 2 90mm and I would ride that quite happily for a fun and playful bike.
Also of note, the RR stem is the only stem in this length range that is approved for running with a Reversed offset and/or a short forward offset and allows room for about 30mm worth of spacers to fine tune height instead of just mounting directly on top of the steerer tube and needing to cut it or get taller bars for adjusting height. It’s also compatible with both 35mm bars and 31.8mm bars with the included bar shims.
If you get one and find that we can’t get you to a setup working together that is better for you, you can return it for a refund minus shipping.I got ChatGPT to make me a spreadsheet of alternatives to the BMB stem (because those are out of stock and expensive to import to the UK). That's a fuzzy category but it seems to include anything 'over the steerer', i.e. too short to fit in front of (or behind) the steerer tube. Feel free to add more to this list and correct any errors. (E.g. it didn't originally include the Nullvorbau one, so I added it manually.)
...I'm trying to share it here but the forum doesn't seem to allow it? @Rob Rides EMTB
I ordered the Aerozine as it was the cheapest, but yesterday a used Rulezman came up on ebay for a similar price so I've got that arriving tomorrow as well. Edit: As Bronson says, the disadvantage of these is that there is no way to adjust the height without cutting the steerer, so I would much rather have the BMB stem, but I do have a selection of bars of different rises, so I'll use those to figure out what sort of setup would suit me.
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sjturner2112
Member
where di you get the formula, is what I am asking, and can you point me to the original source.
ChatGPT list of over-the-steerer MTB stems
Short version
Short version
- The BeMoreBikes Gen 2 90mm RR is still the only clearly current, production, true raised-reverse / negative-offset option in this list.
- The Creature Cycles De-Reacher is probably the closest current UK-market alternative in spirit, but it is not actually reverse / negative offset.
- The Rulezman HC-V3hd and Intend Grace DD are probably the most relevant premium alternatives if you want a short / high / steering-axis-ish setup without going all the way to the BMB geometry.
- The Aerozine XNC-10 is the cheapest purpose-made option here, but also the most experimental.
- The ONOFF and Fifty Fifty setups are really DIY hacks rather than true one-piece competitors.
- The nullvorbau Zero Stem is interesting because it is effectively 0mm reach, but again it is not actually reversed.
- Type: steerer-clamp stem
- Offset / reach: -15 mm
- Rise / height: 90 mm
- Bar clamp: 35 mm native, 31.8 mm with included shim
- Price: about $400
- UK availability: yes, official site says worldwide shipping
- Current ordering: March batch sold out; next batch due in May when I checked
- Steerer cut needed?: maybe, but this is the most height-adjustable option here; official adjust window allows a decent amount of spacer play above/below the clamp
- Main pros: only clearly current true reverse / negative-offset option; huge rise; 35 mm native with shim for 31.8
- Main cons: expensive; unusual geometry; may need broader setup changes
- Verdict: baseline / reference option
- Type: steerer-clamp stem
- Offset / reach: 10 mm
- Rise: 60 mm
- Bar clamp: 31.8 mm only
- Price: about £229.50
- UK availability: very good; UK maker/store
- Current ordering: official product page live; shop page suggested limited / variable stock
- Steerer cut needed?: very likely yes; Creature says you will almost certainly need to cut the fork steerer
- Main pros: UK-made; cheaper than BMB and Rulezman; EFBE Cat 5; probably the strongest "short + tall + gravity" mainstream option in the UK
- Main cons: 31.8 only; still not cheap; not reverse / negative offset
- Verdict: closest current UK alternative in spirit, but not a true BMB substitute geometrically
- Type: steerer-clamp stem
- Offset / reach: 15 mm forward
- Rise: 38 mm
- Bar clamp: 31.8 mm only
- Price: about 274-286 EUR + shipping
- UK availability: I did not find a UK stockist; looks like direct order from Italy
- Current ordering: Rulezman page said "email to order"; limited-series vibe
- Steerer cut needed?: not explicitly a must-cut, but it is fit-sensitive; 40 mm clamp height and a narrow head-tube-length requirement
- Main pros: very short; very light; highly engineered; EFBE certified; integrated top cap
- Main cons: 31.8 only; expensive; lower rise than BMB / Creature; direct-order boutique product
- Verdict: excellent premium short/high alternative if you want something steering-axis-ish without the full BMB amount of rise
- Type: direct-mount DH stem
- Offset / reach: 18 mm
- Rise: 38 mm
- Bar clamp: 31.8 mm only
- Price: about 224-236 EUR + shipping
- UK availability: I did not find a UK stockist; looks like direct order from Italy
- Current ordering: Rulezman page said "email to order"
- Steerer cut needed?: not really applicable in the normal sense because it is direct-mount
- Main pros: very short and light; EFBE certified; relevant if you are on a dual-crown / DH setup
- Main cons: not for normal single-crown use; 31.8 only; expensive
- Verdict: DH-only adjacent option rather than a normal BMB alternative
- Type: over-the-steerer stem with integrated top cap
- Reach: 25 mm
- Stack: 38 mm
- Bar clamp: 31.8 mm only
- Price: about 139 EUR incl. VAT
- UK availability: no UK stockist surfaced in my search; available direct from Intend / EU shops
- Current ordering: official page live; some versions / finishes out of stock, others still available
- Steerer cut needed?: yes; Intend explicitly says the bar sits above the steerer, so you have to cut the steerer accordingly
- Main pros: light; clean integrated design; cheaper than BMB / Rulezman; probably the neatest-looking premium alternative
- Main cons: 31.8 only; max 20 mm handlebar rise; steerer cut required
- Verdict: one of the most relevant premium alternatives if 25 mm reach and 31.8 suit you
- Type: short steerer-clamp stem
- Offset / reach: effectively a 10 mm-class stem from what I could piece together
- Rise: +15°
- Bar clamp: 31.8 or 35 mm
- Price: about $98
- UK availability: I did not find a UK stockist; official sales seem to be direct from Taiwan
- Current ordering: add-to-cart on the Aerozine site when I checked
- Steerer cut needed?: no explicit must-cut warning found; bundle includes spacers and top cap
- Main pros: by far the cheapest purpose-made option here; often mentioned by riders experimenting with this concept; 31.8 and 35 compatibility
- Main cons: not actually reverse; official geometry info is vague; one Pinkbike commenter reported twisting due to short clamp area, so I would treat it as more experimental than the others
- Verdict: cheap test-bed, but not something I would automatically trust as a hard-gravity BMB replacement
- Type: user-reversed DH / direct-mount-style stem
- Reach: nominally 10 mm, with negative-reach effect when reversed
- Rise: depends on spacer stack / setup
- Bar clamp: 31.8 mm
- Price: one forum post mentioned about 14.90 EUR
- UK availability: likely easier to source than the boutique stems, but I did not systematically check this
- Steerer cut needed?: setup-dependent
- Main pros: very cheap experiment; one user reported positive results in steeps
- Main cons: definitely a hack rather than a designed product; jumping reportedly felt odd; safety / fit depends heavily on hardware, spacer stack and your own judgement
- Verdict: useful as a test mule, not a true one-piece competitor to the BMB
- Type: DIY parts-stack solution
- Offset / reach: one forum user reported about -18 mm in the final setup
- Rise: one post mentioned a 28 mm rise stem; final setup reportedly ended up around 40 mm rise
- Bar clamp: 31.8 mm
- Price: one user reported about CAD 216 shipped for the whole setup
- UK availability: not systematically checked
- Steerer cut needed?: setup-dependent
- Main pros: potentially much cheaper than the boutique one-piece stems; one of the more concrete DIY recipes in the thread
- Main cons: fiddly; parts-stack rather than clean integrated product; fit depends on exact bars / spacers / hardware
- Verdict: probably the most convincing DIY alternative in the thread, but still not equivalent to a purpose-made one-piece stem
- Type: over-the-steerer stem with integrated top cap
- Reach: 0 mm
- Stack / height: 30 mm clamping area, 28 mm overhang
- Bar clamp: 31.8 or 35 mm
- Price: about 160 EUR
- UK availability: ships from Germany
- Current ordering: German web shop
- Steerer cut needed?: maybe; not much height adjustability, so a cut may be needed depending on setup
- Main pros: cheaper than BMB; looks well made; true 0 mm reach is interesting
- Main cons: still not cheap; not actually reverse
- Verdict: interesting 0 mm-reach option, but not a true reverse stem
Not sure, it's pretty much common knowledge like 2+2=4.
It's simply the foundational metric upon which to apply things like stack/reach/kinematics to get an idea for how a bike will perform.
Typically a bike with a ratio closer to 1.9 will have a more forward rider position, low and stretched out. A bike closer to 1.8 tends to have a more upright centralized riding position. That's painting in broad strokes though, there are always outliers.
Personally, I've found that bikes closer to 1.8 with a wheelbase around 1280-1290mm are my happy spot, but available terrain dictates desires for most people.
Bufort
New Member
- Mar 26, 2026
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I understand the ratio, but I don't think it affects the riders position, only the front centre does; the chainstay (which forms part of the equation) doesn't affect your stance, it affects handling. Two bikes with identical front-centre lengths, reach, which have the same stance, but can have different F/R ratios.
sjturner2112
Member
formula for determining whether you can run a reverse, high-rise stem is common knowledge like 2+2? Lol. Ok. Thanks. That immediately tells me the efficacy of this formula.
That's correct.
But reach is a number that isn't just an anatomical fit type of thing.
Reach is specifically used to shift the rider's mass upon the bike.
You will see a shorter reach and higher stack on bikes with more balanced f/r ratios. You will see a longer reach and shorter stack on bikes with a higher ratio.
F/r ratio is the foundation that all the other geo numbers are built upon.
The reason there is a trend towards lower ratios, shorter reach, and more stack is that it allows for a bike that doesn't require as much shifting of body weight fore and aft. It's exactly the effect many enduro racers were after by sizing down on bikes, but without sacrificing high speed stability.
A bike configured thusly can also run a longer wheelbase for high speed stability without feeling clumsy in tighter corners.
I think only you can decide that, with Bronson's help perhaps.
I'd assume a bike with a ratio that's closer to 1.8 and is slightly oversized for you would be optimal for the rrs, but I don't believe there's a formula as such to make that decision for you.
Who’s There
Member
Reversed stem is giving me about 22mm offset to the rear.
Unable to test right now due to persistent back issue.
If good I will make risers for the direct mount stem and lower the ENDH on the CSU for a better appearance , When I make the spacers I can add in additional mounting positions to tune the for-aft location.