Stack and reach
How high and how far forward the top of the head tube is, from the bottom bracket. They are the two numbers that decide whether a frame can be set up like yours.
BB, or bottom bracket
The axle your cranks turn on, in the middle of the frame. Every number on this site is measured from it, because it is the one point that sits in the same place on every bike.
Headset cover
The little cap on top of the head tube, under your spacers. Most makers do not publish it, so I assume 15 mm and add 6 mm to the band, which on its own is enough to hold an answer at "probably" rather than "fits".
Stem clamp, and its centre
The collar on the steerer that your stem bolts to. I need the middle of it. Where a maker gives only the height, I assume halfway up and say so on the answer.
Steerer
The tube coming up out of the fork. The cover, the spacers and the stem all sit on it, and it is the thing a mechanic cuts to length.
Bar reach
How far forward the hoods sit from the middle of the bar. Two bars on the same stem can put your hands 20 mm apart, which is why I ask.
Setback
How far your saddle sits behind the bottom bracket.
Drop
How much lower your hands sit than your saddle. On a riser bar I count the bar's rise, so the drop is that much less than it is to the clamp.
Rails, and the rail centre
The two rods under your saddle, and the middle of the straight part of them. That midpoint is the point I use, because it is the one you can find with a tape.
The band
How far out I could be, in millimetres, and why. It is a straight sum of everything I had to assume rather than a clever average, so it errs wide on purpose.
wb, stand, trail
Wheelbase, standover and trail: how long the bike is, how high the top tube is where you straddle it, and how steady the steering feels. I show them against your bike, and I leave them out when the maker does not publish them.
est.
Estimated: a number I worked out rather than read off the maker's table. Anything marked this way can move if the maker publishes the real one.
Close Escape closes it. The measuring guide has the pictures. Open the measuring guide
Genesis Datum
Gravel · 5 sizes
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This is the bike I ride
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- Bike
- Genesis Datum · Gravel · 5 sizes
- Geometry
- bikeinsights.com, fetched 20 Oct 2026
These numbers are second-hand, from Bike Insights. I have not checked them against the maker's own table. Bike Insights cites genesisbikes.co.uk. - Cockpit
- Generic stem and bar, assumed
- Solved with
- cover 15 mm (assumed), max spacers 40 mm (assumed), stem clamp centre 20 mm (assumed), so every verdict carries ±10 mm at the bar
- Sheet
- 22 October 2026 · 686 bikes, 74 makes, 3,984 sizes in the catalogue
Geometry, every size, from Bike Insights
The tinted row is the size drawn beside it. Press a size to draw it.The table runs on to the right: 6 more columns after Reach. Scroll it sideways to read them.
The M drawn to scale from the table, with no build on it. Stack and reach run from the bottom bracket to the top of the head tube; every size is solved from those two. One square is 100 mm.
The maker's cockpit
No stock cockpit I can name, so every size is solved on a generic stem and bar unless you choose one on the sheet.Generic stem and barAssumedNo bar is listed for this frame.
Stock stem and bar per sizeXS 90 x 400, S 100 x 420, M 100 x 420, L 110 x 440, XL 110 x 440 (stem length x bar width, mm)
Frame facts
not read off the maker's page yet: genesisbikes.co.uk- Tyre clearance
- not recorded yet
- Bottom bracket
- not recorded yet
- Axles and brakes
- not recorded yet
- UDH
- not recorded yet
- Seatpost
- not recorded yet
- Frame weight
- not recorded yet
Notes on the cockpit
Kept whole, as I read it off bikeinsights.com.Not recorded by Bike Insights beyond the base build's stem length and bar width per size; no bar is named.
Cockpit and seatpost · 20 words
Not recorded by Bike Insights beyond the base build's stem length and bar width per size; no bar is named.
SECOND-HAND NUMBERS, NOT CHECKED AGAINST THE MAKER: Bike Insights' record of the Genesis Datum, version "2020", build "Base" (disc, carbon frame, drop bar on Bike Insights), 5 sizes XS, S, M, L, XL. Source: aggregator (Bike Insights): version "2020", build "Base", numbers read from the page's __NEXT_DATA__ data script; the maker serves its site only through scripts and Bike Insights has nothing newer than 2020
How I read Bike Insights' table
Genesis serves its own site only through scripts (every page, the sitemap included, returns the same empty shell with the data fetched by script), so the maker's table cannot be read; Tredz and Sigma Sports list no Genesis bikes. Bike Insights' newest version of this model is 2020, so the table is treated as no longer published by the maker and Bike Insights is the source of last resort (D4 second amendment). Bike Insights cites as its source: https://www.genesisbikes.co.uk/bike/datum. Field mapping from Bike Insights: stack, reach, head_tube_angle, seat_tube_angle (from its seat_tube_angle field), head_tube_length, top_tube_effective (from effective_top_tube_length_center_ht_top), seat_tube_length (from seat_tube_length_center_st_top, the first of centre-to-top, centre-to-top-tube, centre-to-centre that it holds), chainstay_length, wheelbase, bottom_bracket_drop, fork offset, front_center, and from its base build the standover height, stem length and handlebar width (a width recorded in cm is converted to mm). Bike Insights stores no published trail (only its own computed one), so trail is null. Its base build lists a 622 mm rim and a 32 mm tyre. Bike Insights cites the maker's page: https://www.genesisbikes.co.uk/bike/datum.