The number that matters on the Nicolai R20 MGU AON Edition is 462, and it appears three times. Medium, large, x-large: one chainstay length, no size-specific rear triangle, no flip chips, no adjustment. Reach goes 460, 480, 500 in clean 20mm steps and the wheelbase follows it exactly, 1294 to 1314 to 1334. Every millimetre of growth happens in front of the bottom bracket. Nothing happens behind it.
That is the precise inverse of where the industry has been heading, and it is worth sitting with, because we have run two pieces in the last few months on bikes doing the opposite. The Yeti MT grows its chainstays 16mm across the range. The Cube Fritzz holds 435mm on every size but uses a high pivot that lengthens the rear centre through the stroke, which is a different kind of answer to the same question. Nicolai, building a 29.5kg gearbox-motor downhill bike at €14,999, looked at the same question and declined to answer it.
The full chart
These are Nicolai’s own numbers, taken from the technical data sheet linked off the R20 MGU AON Edition product page. Front centre is arithmetic (wheelbase minus rear centre), not a Nicolai-published figure, and is marked as such.
| Measurement | M | L | XL |
|---|---|---|---|
| Recommended rider height | 168-180 cm | 178-190 cm | 188-200 cm |
| Reach | 460 mm | 480 mm | 500 mm |
| Stack | 648 mm | 648 mm | 648 mm |
| Top tube length | 598 mm | 618 mm | 638 mm |
| Seat tube length | 420 mm | 420 mm | 420 mm |
| Head tube length | 130 mm | 130 mm | 130 mm |
| Wheelbase | 1294 mm | 1314 mm | 1334 mm |
| Standover | 665 mm | 665 mm | 665 mm |
| Seat tube offset | 140 mm | 140 mm | 140 mm |
| Effective seat angle | 78° | 78° | 78° |
| Head angle | 63.3° | 63.3° | 63.3° |
| Chainstay (rear centre) | 462 mm | 462 mm | 462 mm |
| Bottom bracket drop | -3 mm | -3 mm | -3 mm |
| Fork offset | 47 mm | 47 mm | 47 mm |
| Fork reference length | 602 mm | 602 mm | 602 mm |
| Headset stack | 3 mm | 3 mm | 3 mm |
| Rear travel | 200 mm | 200 mm | 200 mm |
| Shock | 250 x 75 mm | 250 x 75 mm | 250 x 75 mm |
| Rear hub | 157 x 12 mm | 157 x 12 mm | 157 x 12 mm |
| Front tyre diameter | 745 mm (29 x 2.5) | 745 mm | 745 mm |
| Rear tyre diameter | 715 mm (27.5 x 2.5) | 715 mm | 715 mm |
| Front centre (calculated) | 832 mm | 852 mm | 872 mm |
| Front:rear ratio (calculated) | 1.80 | 1.84 | 1.89 |
Two published figures deserve a flag. The bottom bracket drop is listed as -3 mm, meaning the bottom bracket sits 3mm above the line between the axles, which on a 200mm-travel downhill bike is remarkably high and only makes sense in the context of a Pinion MGU housing that already hangs a long way below the down tube and a rear wheel that is an inch smaller than the front. Second, the same sheet lists “matching fork travel: 160-170 mm” in its interface section, which is plainly a template artefact carried over from another model, since the bike ships with a 203mm inverted Manitou Dorado Pro LTD. Nicolai’s own maximum approved fork length of 605mm and the 602mm fork reference measurement are the numbers that actually govern the front end.
Where sources conflict, Nicolai’s chart wins. Pinkbike’s launch coverage lists the battery upgrade at +€120 and the fork at 200mm; Nicolai’s shop lists +€200 for the 1060Wh pack, and BikeRadar puts the Dorado at 203mm. Motor torque is quoted as 85Nm at the crank by BikeRadar and as 160Nm by Pinkbike; both can be true, since the second figure is what the gearbox reduction produces in the low gears rather than what the motor itself makes.
What a fixed 462mm rear actually does
Start with what does not change. The bottom bracket is 462mm forward of the rear axle on every size. Your feet sit in exactly the same place relative to the rear tyre whether you are 170cm or 200cm. That is a genuinely useful constant: the way the bike loads its rear tyre when you drop your heels and push is identical across the range, and anyone moving between sizes at a race team or a demo fleet gets the same rear-wheel feel.
What changes is everything in front. The bars move 40mm further away from the rear axle between M and XL. Expressed as a share of the wheelbase, the rear centre goes from 35.7% on M, to 35.2% on L, to 34.6% on XL. That is not a dramatic slide, but it points in a specific direction: the taller you are, the less of this bike is behind you.
In practice, on the XL, that reads as a front end that bites early and a rear that will rotate out from under you sooner than the 1334mm wheelbase suggests. Weighting the front to load a 63.3° head angle into an off-camber is easy, because a long front centre plus a fixed rear means your hands have leverage over a rear wheel that has not grown to resist it. The flip side is that when you get backseat on a steep, chundery track, the XL will spit its rear wheel sideways before the medium does. Riders who came off a 450mm-chainstay enduro bike will find it familiar. Riders coming off a size-proportional bike with a 455mm rear will notice the rear stepping out and will blame the tyre.
There is a second, less obvious consequence, and it is the one that makes the medium the odd size out. At a 1.80 front-to-rear ratio the M is the most rearward-biased bike in the range, which on a 29.5kg machine with a motor slung low and forward means a bike that wants to loop out of steep compressions and that takes deliberate input to get the front tyre to hook up. The 648mm stack is generous on a medium frame, and that height works against a shorter rider trying to get over the front.
The counterargument in Nicolai’s favour is the axle path. This is a high-pivot layout with the idler mounted above and behind the main pivot, which means the rear axle travels rearward as the bike compresses, and the effective rear centre at sag and deep in the stroke is longer than the 462mm static figure. Nicolai’s tech sheet has a LINKAGE tab, but it is empty, and no published axle path data exists that I can find, so I am not going to put a number on how much longer. What can be said is that the static number understates the bike in the only situation where it matters, which is under load.
The MGU, the idler and the belt
The Pinion E1.12 Motor.Gearbox.Unit puts twelve sealed gears and the motor in one housing at the bottom bracket, driving a Gates carbon belt. There is no derailleur, no cassette, no rear mech hanging off the dropout, and the rear hub is a plain 157×12 with a single sprocket.
This matters more on a high pivot than on any other layout. A conventional high pivot has to route the chain over an idler because the rearward axle path would otherwise pull the chain hard enough to cause chain growth and pedal kickback. The idler solves the kinematics but adds drag, noise and a wear item. Here, the idler is still doing its job (it sits above and behind the main pivot per Pinkbike’s description), but the thing running over it is a belt with no articulating links, and the thing at the other end is a gearbox with a fixed input sprocket rather than a derailleur trying to maintain tension across twelve cogs.
The unsprung weight effect is the other half. Moving the entire gear cluster from the rear hub to the bottom bracket takes rotating mass off the rear wheel and puts it at the centre of the bike, low and between the axles. On a 200mm bike where the rear wheel has to track over repeated square edges, that is real, and it partially offsets a 29.5kg total weight that would otherwise be indefensible.
Suspension is an inverted rocker link driving a 250x75mm Manitou Mara Pro, producing what Pinkbike describes as a mild S-shaped leverage curve: slightly progressive off the top, flattening through the middle, ramping at the end. That is the right shape for a bike with this much mass. A linear curve on a 29.5kg bike would blow through travel on the first big hit; a heavily progressive one would make the small-bump performance harsh at the sag point where a downhill bike does most of its work. There is also an adjustable forward shock mount for geometry tweaks, which is the closest thing this bike has to an adjustment for the rear end problem, and it does not change the chainstay.
Where it sits
There is nothing else quite like it for sale. The Manitou Dorado Pro LTD in silver is exclusive to this bike, the Hayes Dominion A4s run 220mm rotors, and the whole thing exists because Gamux and AON Racing wanted a shuttle-free World Cup practice tool. €14,999 with the 800Wh pack, €15,199 with 1060Wh, Europe only, no North American distribution. BikeRadar’s headline quote from Nicolai is “it’s not meant to be rational,” and that is an honest description of the product rather than a marketing line.
Against a conventional DH bike it is 12kg heavier and self-shuttling. Against an e-enduro it has 200mm of rear travel, a 63.3° head angle and a 665mm standover that make it hopeless as a trail bike. It occupies a category with roughly one other occupant.
Sizing, and a note for tall riders
I am 6’4″, or 193cm, which puts me squarely in Nicolai’s 188-200cm XL band. The XL is the right call, but not for the reason the chart suggests.
The reach is fine. 500mm on a downhill bike with a 63.3° head angle is normal in 2026, not long. The number that constrains a tall rider here is stack, at 648mm on every size, built from a 130mm head tube that also does not change. On the XL that stack is proportionally the lowest in the range, and a 193cm rider will be reaching further down to the bars than a 175cm rider on the medium. Budget for a 40mm or 50mm rise bar and do not be surprised if you want spacers on top of that, keeping in mind Nicolai’s 3mm headset stack figure means there is not much built-in height to start with.
The good news for tall riders is the 420mm seat tube. On a downhill bike the saddle mostly exists to be out of the way, but this one has to be pedalled back up, and a 420mm tube with a 30.9mm post gives a 193cm rider room for a long dropper at full extension. That is a genuine advantage over DH frames with size-scaled seat tubes.
The honest caveat: the XL is where the fixed rear centre costs you the most. You are the rider with the longest front centre, the most mass, the highest centre of gravity, and the same 462mm behind you as everyone else. Expect a bike that steers beautifully and that will let go at the back if you get lazy about staying centred. On a 29.5kg machine at speed, that is not a small thing.
If you fall between sizes, size down. The 20mm reach steps are large, the stack does not compensate, and on a bike this heavy the shorter front centre is easier to muscle than the longer one is to weight.