Bikes Ranked
Two bikes, both "medium": choosing a size from stack and reach
After this page you will be able to take two bikes whose manufacturers publish a stack row and a reach row — most road and mountain brands now do, though not all — find those rows on each geometry chart, and state in millimeters how far apart they are. You will also be able to say whether that gap is large, by measuring it against the step between two sizes on the same chart. It will not tell you your size; nothing written down can. It will tell you whether a bike is comparable to one you have already ridden.
The short answer
Open the geometry chart for the exact bike and the exact model year you are considering, reached through that model's own product page. Read two rows: Stack and Reach. Do the same for a bike you have already ridden and know the feel of. Compare the numbers in millimeters. The letter next to them is a label the manufacturer chose for its own chart, and no standard this page could open defines it.
- Stack, per Canyon, is the vertical height from the bottom bracket to the top of the head tube. It governs how high the bars end up before you add or remove spacers.
- Reach, per Canyon, is the horizontal distance between those same two points. It governs how far forward you are stretched. Trek, on its mountain bike sizing page, measures reach to the center of the head tube rather than the top. Neither manufacturer states the two definitions are equivalent, and this page has not verified that they are — comparing across brands, check each manufacturer's stated reference points.
- Seat tube length, standover and the size letter are constraints or labels. Trek says outright that reach and effective top tube matter more than standover height or seat tube length when comparing sizes, while noting the older measurements still count for something.
Why "medium" is not a specification
Canyon publishes a geometry chart for the Endurace CF 7 and another for the Ultimate CF 7. Same manufacturer, same size letters, same 2027 model-year identifiers on both product pages, same 28in wheels in every size on both charts, both road bikes. Size M on the Endurace is stack 584mm, reach 392mm. Size M on the Ultimate is stack 560mm, reach 393mm. That is 24mm of stack between two frames one company calls the same size — and one millimeter of reach. Nothing was tested to find that out. It is subtraction on two published tables, both read on 2026-09-22.
The pair of numbers matters more than either one. Had you compared only reach, you would have concluded these two bikes put you in the same place. Had you compared only stack, you would have concluded they are a size apart. Both conclusions are wrong, and the size letter gave you neither.
Look across the letters and it sharpens. The Endurace in size S is stack 563mm, reach 390mm. The Ultimate in size M is stack 560mm, reach 393mm — three millimeters apart on both rows. Two different letters, and for these two rows, the same position. Now go the other way. The Endurace in size L is stack 605mm and the Ultimate in size XL is stack 606mm, one millimeter apart — but their reach figures are 401mm and 419mm, eighteen millimeters apart. Matching on one row alone is how people order the wrong frame.
| Size | Endurace stack | Endurace reach | Ultimate stack | Ultimate reach | Stack gap | Reach gap |
|---|---|---|---|---|---|---|
| 2XS | 525 | 382 | 490 | 372 | +35 | +10 |
| XS | 545 | 386 | 520 | 378 | +25 | +8 |
| S | 563 | 390 | 539 | 390 | +24 | 0 |
| M | 584 | 392 | 560 | 393 | +24 | −1 |
| L | 605 | 401 | 580 | 401 | +25 | 0 |
| XL | 629 | 409 | 606 | 419 | +23 | −10 |
| 2XL | 649 | 427 | 624 | 429 | +25 | −2 |
Read down the gap columns. The Endurace is taller than the Ultimate at every shared size, by 23 to 35mm. The reach column does not behave that way at all: the Endurace is longer at the two smallest sizes, level at S and L, and 10mm shorter at XL. There is no consistent direction. That is worth saying plainly, because it is tempting to assume an endurance frame is always taller and shorter than a race frame. On these two charts the stack half of that is true and the reach half is not — and two charts could not establish a rule about frame categories in any case.
How much is a lot?
A gap in millimeters means nothing until you know the step between sizes on the same chart. Both charts answer that for you. On the Endurace CF 7, consecutive sizes are 18 to 24mm of stack apart and 2 to 18mm of reach apart. On the Ultimate CF 7, 18 to 30mm of stack and 3 to 18mm of reach. Note how uneven the reach steps are: on the Endurace, 2XS to XS is 4mm while XL to 2XL is 18mm.
So the 24mm of stack between the two bikes at size M is roughly one whole size step on either chart — a real difference, of the same order as moving a letter. The one millimeter of reach is far below any step on either chart, and below anything the letter could have expressed. That is the only calibration this page can give you, and it comes from the charts themselves. None of the sources opened here publishes a threshold for how many millimeters a given rider will notice, and this page does not invent one.
There is no standard behind the letter
ISO 4210-2:2023 is the international safety and test standard for city and trekking, young adult, mountain and racing bicycles. Its scope is safety and performance requirements for the design, assembly and testing of bicycles and sub-assemblies, plus guidelines for manufacturer's instructions. It defines nothing itself. Its clause 3 reads, in full: "For the purposes of this document, the terms and definitions given in ISO 4210-1 apply." Its requirements run through brakes, steering, frames, forks, wheels, pedals, saddles, lighting and marking, with one informative annex on steering geometry. Nothing in it concerns sizing.
The vocabulary lives in ISO 4210-1:2023, which is not free to read. Its contents list includes a section 3.6 headed "Frame and fork". The publicly posted preview truncates partway through section 3.5, so this page has not read 3.6 and makes no claim about what is or is not in it. What can be said from the charts alone is the part that matters to a buyer: two Canyon models of the same model year assign the letter M to frames 24mm apart in stack. Whatever ISO 4210-1 defines, it is not constraining that letter. Some compatibility questions do have standardized numbers behind them — which tires fit your rims is one, covered at /tire-rim-compatibility/. Frame sizing, on the evidence here, is not one of them.
The gap between the label and the number is a common complaint. On an mtbr thread proposing a universal sizing standard, a poster reported that his last three bikes, all sold as mediums, showed reach figures of 445mm, 454mm and 465mm. Treat that as evidence the question gets asked, not as verified figures — the poster read them off the third-party 99spokes database rather than manufacturer charts, and this page has not checked them against Giant, Salsa or Rocky Mountain.
Two ways the chart will trip you up
First, which document you landed on. Canyon's current Endurace CF 7 product page is marked 2027, carries a "Geometry & dimensions" section, and its Download PDF link resolves to productpdf/geometry/?pid=4627. That PDF is titled "Endurace CF 7", lists seven sizes, and gives M as stack 584mm, reach 392mm — identical to the table on the page above it. Page and PDF agree. But Canyon also still serves a geometry PDF at pid=2855 titled "Endurace CF 7 Disc": a discontinued product, eight sizes, M at stack 590mm and reach 378mm, and 27.5in wheels on its two smallest sizes where the current bike uses 28in throughout. Both files print only a download date, with no model year anywhere on the document.
At size M the two Endurace charts are 6mm of stack and 14mm of reach apart; at 2XS the reach gap is 28mm. Reach the PDF through the product page for the bike you are actually buying. A PDF found by search, or by editing a number in a URL, can describe a generation nobody sells any more, and nothing printed on the file will tell you which.
| Size | CF 7 stack | CF 7 reach | CF 7 Disc stack | CF 7 Disc reach | Stack diff | Reach diff |
|---|---|---|---|---|---|---|
| 3XS | — | — | 510 | 350 | — | — |
| 2XS | 525 | 382 | 529 | 354 | −4 | +28 |
| XS | 545 | 386 | 548 | 370 | −3 | +16 |
| S | 563 | 390 | 568 | 375 | −5 | +15 |
| M | 584 | 392 | 590 | 378 | −6 | +14 |
| L | 605 | 401 | 611 | 387 | −6 | +14 |
| XL | 629 | 409 | 637 | 405 | −8 | +4 |
| 2XL | 649 | 427 | 656 | 414 | −7 | +13 |
Second, row labels — and this is the one that costs real money. Canyon's current charts publish Stack and Reach and, separately, Effective Stack and Effective Reach, which Canyon defines as measured to your hand position on the hoods rather than to the top of the head tube. Older Canyon PDFs carry two further rows labeled Stack+ and Reach+. These are not the same measurement under another name. On the Endurace CF 7 Disc PDF at size M, Reach+ is 455mm against a reach of 378mm — 77mm more. On the current Endurace CF 7 at size M, effective reach is 544mm against a reach of 392mm — 152mm more, twice as much. The Ultimate CF SL 8.0 PDF shows the same split: Reach+ 471mm against reach 391mm, 80mm.
None of the Canyon documents opened here defines Stack+ or Reach+, so do not treat the two labels as interchangeable. Compare an old PDF's Reach+ against a current page's effective reach at size M and you will be about 89mm out — enough to buy the wrong frame over. Compare stack against stack and reach against reach, and leave every other row alone.
| Chart (size M) | Stack | Extra stack row | Stack delta | Reach | Extra reach row | Reach delta |
|---|---|---|---|---|---|---|
| Endurace CF 7 (pid=4627, current) | 584 | 677 (Effective Stack) | +93 | 392 | 544 (Effective Reach) | +152 |
| Ultimate CF 7 (pid=4612, current) | 560 | 629 (Effective Stack) | +69 | 393 | 553 (Effective Reach) | +160 |
| Endurace CF 7 Disc (pid=2855, discontinued) | 590 | 686 (Stack+) | +96 | 378 | 455 (Reach+) | +77 |
| Ultimate CF SL 8.0 (pid=2151, discontinued) | 567 | 659 (Stack+) | +92 | 391 | 471 (Reach+) | +80 |
The procedure
- Find the geometry chart for the bike you already ride — exact model, exact model year, reached through that model's own product page rather than by searching for a PDF. Write down its stack and reach.
- Find the same two rows for every candidate bike, in every size you are weighing, from that manufacturer's own page for that model year.
- Subtract. You now have each candidate expressed as "X mm taller or lower, Y mm longer or shorter" than a bike whose feel you actually know.
- Measure each gap against the step between adjacent sizes on the same chart. A gap smaller than one size step is smaller than anything the letter could have told you; a gap of one step or more is a real move.
- Decide which direction you want to go, and by how much. Canyon gives the same advice in its own size guide: note your current bike's stack and reach before ordering and use them as a baseline, and compare the geometry of both sizes when you are on the cusp of two.
This is a comparison method. It tells you how two frames differ. It does not tell you which one is right for you, and it cannot.
What stack and reach do not settle
Stack and reach are two points on a frame. They say nothing about where your saddle needs to sit fore and aft, how long your cranks should be, how wide your bars should be, or anything that depends on your leg length, torso, arm length, flexibility or injuries. Two riders of identical height can want different frames. A chart cannot see any of that.
There is also a build layer sitting on top of the frame. Canyon's charts include a component geometry section, but less of it varies by size than you might expect. On the Endurace CF 7 Disc chart, stem length, handlebar width, crank length and wheel size vary across the eight sizes; the spacer stack does not — it is 35.0mm in every size — and neither do chainring size, seat post diameter, seat post length, the insertion depths or disc size. On the current Endurace CF 7 chart the spacer is 18mm in every size. The published stack and reach are still frame numbers, measured to the head tube, with the fitted stem and the spacer stack sitting on top of them.
It follows that a stem change trades against reach and a spacer change trades against stack, within whatever range the manufacturer permits for that frame and fork. That much is inferred from the charts and from Canyon's own definitions, not stated by either. None of the sources opened here publishes a conversion figure, so this page does not give one — and steerer, spacer and stem limits are safety-critical and belong to the frame and fork manufacturer's own instructions.
Standover is a floor, not a target
Surly measures standover from the top tube to the ground at a stated tire size, and recommends that your inseam clear the frame's standover by at least 2–3cm on a road bike and a bit more on a mountain bike. That is Surly's guidance for Surly frames, not a universal rule, and it is a minimum to clear rather than a number to optimise. Surly also notes that frame size normally refers to seat tube length, and that getting the frame's length right will get you closer to a good fit than seat tube length or the nominal frame size will.
Surly's first recommendation to anyone trying to pick a size is to talk to a bike shop. That is the honest end of this page too. A fitting or a test ride is the only thing that can tell you your size. Everything above tells you how two bikes differ, which is a different and much more checkable question.
Check yours
- Go to the manufacturer's product page for your exact model and model year. On Canyon, look for the "Geometry & dimensions" section, which also carries a Download PDF link — follow that link rather than guessing or editing a PDF URL. On Trek, Trek states that geometry is found by scrolling to the geometry chart on each bike's detail page.
- Read the rows labeled Stack and Reach. Not Stack+, not Reach+, not effective stack, not effective reach, not standover, not seat tube.
- Confirm the model year on the page matches the bike you are comparing, and that the PDF you opened came from that page. The two Endurace charts above are a worked example of what happens when it does not.
- Check that your manufacturer publishes both rows. Most road and mountain brands now do, but not all: Trek's mountain bike sizing page defines reach and never defines stack, and Surly's fit page defines neither. Where stack is missing you can still compare reach and effective top tube, which is what Trek tells its own buyers to do.
- If you cannot find a geometry chart for your current bike because it is old or the page is gone, you have no baseline and the comparison above cannot be run. A shop with a fit jig can measure the bike you own instead.
The component rows on the same chart — seat post diameter, wheel size, disc size — answer a different class of question, about what parts will physically attach. Two of those are covered separately: tires against rims at /tire-rim-compatibility/, and cassettes against freehub bodies at the cassette and freehub guide.
Every number above was read off a manufacturer's published chart or a standards document on 2026-09-22 and is cited below. Geometry charts are revised without notice; check the figures against the live page before you order anything.
Check it on your own equipment
These take you to the manufacturers and standards bodies the page draws on, so you can look up your exact model.
- Manufacturer specification
Canyon Endurace CF 7 — Geometry & dimensions section (opens in a new tab)Scroll to "Geometry & dimensions". You get a basic geometry table with lettered rows — (i) Stack, (j) Reach, (o) Effective Stack, (p) Effective Reach — for sizes 2XS to 2XL, a component geometry table, and a Download PDF link that resolves to productpdf/geometry/?pid=4627. The PDF matches the on-page table. This is the pattern to follow on any Canyon product page: reach the PDF through the product page, and the model year shown on the page is the year the table belongs to. — www.canyon.com - Manufacturer specification
Canyon Ultimate CF 7 — Geometry & dimensions section (opens in a new tab)The other bike in the comparison above, on the current 2027 product page. The same Geometry & dimensions layout, seven sizes 2XS to 2XL, stack 490–624mm and reach 372–429mm, and a Download PDF link to productpdf/geometry/?pid=4612. Open it alongside the Endurace page and subtract the M column from the M column yourself — 584 against 560 in stack, 392 against 393 in reach. — www.canyon.com - Official support page
Trek — Understanding Trek mountain bike sizing (opens in a new tab)Trek's own definitions of reach and effective top tube, its statement that these matter more than standover height or seat tube length when comparing sizes, its note that being between sizes is normal, and its instruction to find geometry on each bike's detail page. Useful as a second manufacturer telling buyers to compare published numbers rather than size letters — though note it is a mountain bike page, it measures reach to the center of the head tube rather than the top, and it does not define stack at all. — www.trekbikes.com - Official support page
Surly — Bike Fit (opens in a new tab)Definitions of effective top tube, standover height and seat tube length in plain language, Surly's 2–3cm road-bike standover clearance guidance, its point that frame length matters more than seat tube length, and its recommendation to start by talking to a bike shop. Read this before you convince yourself a chart can replace a fitting. — surlybikes.com
What this page does not tell you
- Every figure is transcribed from a manufacturer's published chart or a standards document, not from any measurement made here.
- The Canyon, Trek and Surly material is used because those manufacturers publish the numbers and the guidance openly, not because their products are better than any other.
- Geometry charts are revised between model years and sometimes within them, and manufacturers change URLs. All figures were read on 2026-09-22 and should be checked against the live page before ordering.
- The Endurace CF 7 and Ultimate CF 7 tables describe those two specific Canyon models in their 2027 model year. The stack and reach relationship between them tells you nothing about any other brand's sizing, and nothing general about endurance frames versus race frames — two charts cannot establish that. The method transfers; the numbers do not.
- This page cannot tell you how many millimeters of difference a rider will notice. No source opened here publishes such a threshold. The only calibration offered is the step between adjacent sizes on the same chart, which is arithmetic on the published tables.
- The Endurace CF 7 Disc (pid=2855) and Ultimate CF SL 8.0 (pid=2151) charts are cited only as examples of superseded documents that Canyon still serves, and of the Stack+/Reach+ row labels. Neither product appears in Canyon's current range, and their figures should not be used to size a bike you are buying now.
- Canyon does not define Stack+ or Reach+ on any document opened for this page. The statement that they differ from effective stack and effective reach is based on comparing the published values, not on any definition — the underlying measurements are not known here, only that they are not the same.
- The 445mm / 454mm / 465mm reach figures are as reported by one poster on a public forum, citing the third-party 99spokes database. They were not verified against Giant, Salsa or Rocky Mountain charts and are presented only as evidence that the complaint is common.
- This is not bike fit advice and not a fit prescription. It is a method for comparing two published geometry charts. Surly's own page tells readers to consult a bike shop, and this page repeats that.
- The note about trading stem length against reach and spacers against stack is inferred from the component-geometry rows on Canyon's charts. No opened source publishes a conversion figure, and steerer, spacer and stem limits are safety-critical and set by the frame and fork manufacturer.
- ISO 4210-2:2023 was read from a publicly posted preview PDF, not a purchased copy; the scope, contents and full clause 3 are present in that preview. ISO 4210-1:2023, the vocabulary part, was also read only as a preview, which truncates inside section 3.5 — so this page has not read its section 3.6 "Frame and fork" and makes no claim about whether it defines stack, reach or a frame size designation.
Sources
Manufacturers revise specifications. Every source below is dated — open it before you buy.
- Canyon defines stack as the vertical height from the bottom bracket to the top of the head tube.
- Canyon defines reach as the horizontal distance between the same two points used for stack — bottom bracket and top of the head tube.
- Canyon defines effective stack as the vertical distance from the bottom bracket to the rider's hood position, and effective reach as the horizontal distance to that same hand position.
- Canyon's road bike geometry explainer does not define, mention or explain any term written as "Stack+" or "Reach+".
- Canyon defines standover height as measured from the midpoint of the top tube to the ground.
- Trek defines reach as the horizontal distance from the center of the head tube to a vertical line running through the center of the bottom bracket shell.
- Trek does not define stack anywhere on its "Understanding Trek mountain bike sizing" page, and that page is specifically about mountain bike sizing.
- Trek defines effective top tube as the horizontal distance from the center of the head tube to the center of the seat post.
- Trek advises that riders comparing sizes should prioritise reach and effective top tube over standover height and seat tube length, while noting the older measurements are still worth considering.
- Trek states that many riders find themselves between sizes, and that going up or down depends on riding style and body proportions.
- Trek states that geometry measurements are found by scrolling to the geometry chart on each bike's own detail page.
- Surly defines effective top tube length as measured from the center of the head tube where the top tube joins it, horizontally back to the center of the seat post.
- Surly defines standover height as the measurement from the top tube to the ground, assuming a stated tire size.
- Surly states that frame size generally refers to frame height — the seat tube length from the bottom bracket to the top tube.
- Surly states that getting the frame's length right gets a rider closer to a good fit than seat tube length or nominal frame size does.
- Surly recommends inseam clearance over the frame's standover of at least 2–3cm for a road bike and somewhat more for a mountain bike. This is Surly's guidance for Surly frames, not a universal standard.
- Surly's first recommendation to anyone trying to find the right size is to consult a bike shop.
- Canyon advises buyers to note the stack and reach of their current bike before ordering and use those figures as a baseline, and says that when between two sizes, comparing the geometry of both — against the current bike's stack and reach — helps decide whether to take the larger or smaller frame.
- Canyon's geometry PDF for the Endurace CF 7 (pid=4627) is titled "Endurace CF 7", covers seven sizes 2XS to 2XL, and gives Stack: 525, 545, 563, 584, 605, 629, 649 mm and Reach: 382, 386, 390, 392, 401, 409, 427 mm. Its rows are labeled "Effective Stack" (619, 639, 656, 677, 699, 724, 744 mm) and "Effective Reach" (501, 516, 531, 544, 563, 582, 599 mm) — not Stack+/Reach+. Wheel size is 28in in every size and the spacer is 18mm in every size. The document prints a download date and no model year.
- Canyon's geometry PDF for the Ultimate CF 7 (pid=4612) is titled "Ultimate CF 7", covers seven sizes 2XS to 2XL, and gives Stack: 490, 520, 539, 560, 580, 606, 624 mm and Reach: 372, 378, 390, 393, 401, 419, 429 mm, with rows labeled "Effective Stack" (565, 592, 608, 629, 651, 676, 694 mm) and "Effective Reach" (522, 516, 539, 553, 570, 599, 610 mm). Wheel size is 28in in every size and the spacer is 18mm in every size. The document prints a download date and no model year.
- Canyon's Endurace CF 7 product page carries 2027 model-year identifiers, contains a section headed "Geometry & dimensions" with a Download PDF link, and that link resolves to productpdf/geometry/?pid=4627. The stack, reach, effective stack and effective reach values in the on-page table match the pid=4627 PDF exactly.
- Canyon's Ultimate CF 7 product page carries 2027 model-year identifiers and its only geometry PDF link resolves to productpdf/geometry/?pid=4612.
- Canyon still serves a geometry PDF at pid=2855 titled "Endurace CF 7 Disc", covering eight sizes 3XS to 2XL, with Stack: 510, 529, 548, 568, 590, 611, 637, 656 mm and Reach: 350, 354, 370, 375, 378, 387, 405, 414 mm. Its extra rows are labeled Stack+ (605, 624, 644, 664, 686, 709, 734, 754 mm) and Reach+ (394, 410, 425, 441, 455, 474, 493, 512 mm); no "Effective Stack" or "Effective Reach" row appears. Wheel size is 27.5in for 3XS and 2XS and 28in for XS and above. The document prints a download date and no model year.
- On the Endurace CF 7 Disc chart (pid=2855) the component geometry rows that vary by size are stem length (80–120mm), handlebar width (380–440mm), crank length (165–175mm) and wheel size (27.5in/28in). The spacer is 35.0mm in every one of the eight sizes, and chainring size (50/34), seat post diameter (27.2mm), seat post length (350mm), maximum insertion depth (207mm), minimum insertion depth (107mm) and disc size (160/160) are also constant across all sizes.
- Canyon's geometry PDF for the Ultimate CF SL 8.0 (pid=2151) covers seven sizes 2XS to 2XL with Stack: 500, 522, 546, 567, 592, 613, 631 mm and Reach: 368, 378, 385, 391, 399, 418, 428 mm, and carries rows labeled Stack+ (592, 613, 638, 659, 686, 707, 726 mm) and Reach+ (423, 435, 454, 471, 489, 508, 528 mm). No "Effective Stack" or "Effective Reach" row appears.
- "Ultimate CF SL 8.0" does not appear in Canyon's current Ultimate range, which is presented as CFR, CF SLX and CF tiers (for example Ultimate CF 7, Ultimate CF SLX 8 Di2, Ultimate CFR Di2).
- At size M the Canyon Endurace CF 7 is 584mm stack / 392mm reach and the Canyon Ultimate CF 7 is 560mm stack / 393mm reach — 24mm of stack apart and 1mm of reach apart, from the same manufacturer at the same size letter and model year.
- Across the seven sizes they share, the Canyon Endurace CF 7 has 23–35mm more stack than the Canyon Ultimate CF 7, but its reach does not differ in a consistent direction: +10, +8, 0, −1, 0, −10 and −2 mm from 2XS to 2XL.
- The Canyon Endurace CF 7 in size S (563mm stack, 390mm reach) is within 3mm on both rows of the Canyon Ultimate CF 7 in size M (560mm stack, 393mm reach), despite the two-letter difference. Conversely the Endurace in size L (605mm stack) and the Ultimate in size XL (606mm stack) are 1mm apart in stack but 18mm apart in reach (401mm against 419mm).
- On the Canyon Endurace CF 7 chart the step between adjacent sizes is 18–24mm of stack and 2–18mm of reach. On the Canyon Ultimate CF 7 chart it is 18–30mm of stack and 3–18mm of reach.
- At size M the Canyon Endurace CF 7 chart and the Endurace CF 7 Disc chart differ by 6mm of stack (584 against 590) and 14mm of reach (392 against 378); at size 2XS the reach difference is 28mm (382 against 354).
- Stack+ and Reach+ on older Canyon PDFs are not the same measurements as Effective Stack and Effective Reach on current Canyon charts. At size M, Reach+ exceeds reach by 77mm on the Endurace CF 7 Disc and by 80mm on the Ultimate CF SL 8.0, while Effective Reach exceeds reach by 152mm on the Endurace CF 7 and 160mm on the Ultimate CF 7 — roughly double. Stack+ exceeds stack by 96mm and 92mm respectively, against Effective Stack margins of 93mm and 69mm.
- Comparing the Endurace CF 7 Disc PDF's Reach+ at size M (455mm) against the current Endurace CF 7's effective reach at size M (544mm) produces an error of 89mm.
- None of the Canyon documents opened for this page — the geometry PDFs pid=4627, pid=4612, pid=2855 and pid=2151, or Canyon's road bike geometry explainer — defines the terms Stack+ or Reach+.
- The scope of ISO 4210-2:2023 is safety and performance requirements for the design, assembly and testing of bicycles and sub-assemblies, plus guidelines for manufacturer's instructions. It applies to city and trekking, mountain and racing bicycles with a maximum saddle height of 635mm or more, and to young adult bicycles with a maximum saddle height of 635mm or more and less than 750mm.
- Clause 3 of ISO 4210-2:2023 defines no terms of its own. It reads: "For the purposes of this document, the terms and definitions given in ISO 4210-1 apply." The standard's normative references list ISO 4210-1 as the Vocabulary part of the series.
- The contents and requirements of ISO 4210-2:2023 contain no clause on frame size, stack or reach. Its clauses cover toxicity, sharp edges, fasteners, crack detection, protrusions, brakes, steering, frames, front fork, wheels and tire assembly, mudguard, pedals and drive system, chain and belt, chain guard, saddles and seat posts, spoke protector, luggage carriers, road test, lighting and reflectors, warning device, manufacturer's instructions and marking, with one informative annex, Annex A, on steering geometry.
- ISO 4210-1:2023 is the vocabulary part of the series. Its contents list includes a section 3.6 headed "Frame and fork" on page 5, alongside 3.1 Bicycle type, 3.2 General terms, 3.3 Driving environment, 3.4 Brake, 3.5 Head assembly, 3.7 Wheel and rim, 3.8 Pedal and drive system and 3.9 Saddle and seat-post. The publicly posted preview truncates partway through section 3.5, so the content of section 3.6 was not readable and is not claimed here.
- Because ISO 4210-2 delegates all terminology to ISO 4210-1, and because two Canyon models of the same model year label frames of different stack with the same letter, the size letter on a frame is a manufacturer's own label rather than a value fixed by any standard this page could read.
- Because a frame's published stack and reach are measured to the head tube while the fitted stem and spacer stack are separate components listed elsewhere on the chart, stem length trades partly against reach and spacer height partly against stack, within whatever range the frame and fork manufacturer permits. No source opened for this page publishes a conversion figure.
- On an mtbr forum thread proposing a universal frame sizing standard, a poster reported that his last three bikes, all sold as mediums, showed reach figures of 445mm (Giant), 454mm (Salsa) and 465mm (Rocky Mountain), citing the third-party 99spokes database.