COMPARISON OF FRAME GEOMETRY
To calculatorsDrive in the numbers of two or three frames from the manufacturer's tables — you will get a table with deltas, STR, trail, front center and human output: how many spacers, what kind of takeaway and what will change in the behavior of the steering wheel.
How to compare geometry before buying
In A and B there are numbers-examples, so that the page opens alive — replace them with your own. There is no base of frames here and there will not be: you drive in the numbers from the official table of the manufacturer. Lying with numbers out of your head is the worst thing such a calculator can do.
The link to the page stores everything you entered — you can throw it into the chat and argue about geometry in a substantive way.
The frame we're comparing to: your current one or the one you already like.
Fill in at least stack and reach — let's count STR, trail, and front center.
Candidate for purchase. All deltas in the table are considered relative to frame A.
Fill in at least stack and reach — let's count STR, trail, and front center.
The third frame is optional. You can leave it empty.
Fill in at least stack and reach — let's count STR, trail, and front center.
Rows are parameters, columns are frames. In columns B and C, there is a Δ value relative to frame A.
| Parameter | Frame A | Frame B | Frame C |
|---|---|---|---|
| Stack | — | — | — |
| Reach | — | — | — |
| STR (stack/reach) | — | — | — |
| Upper Tube (ETT) | — | — | — |
| Steering Angle (HTA) | — | — | — |
| Seatpost Angle (STA) | — | — | — |
| Steering tube | — | — | — |
| Fork departure (rake) | — | — | — |
| Trail (trail removal) | — | — | — |
| Feathers (chainstay) | — | — | — |
| Wheelbase | — | — | — |
| Front center | — | — | — |
| The share of the front center in the base | — | — | — |
| Carriage drop | — | — | — |
Lengths in scale: stack, reach, Wheelbase, Feathers. The longest frame occupies the entire strip.
Fill in two frames — and a verbal analysis will appear here: spacers, take-out, steering behavior.
STR = stack / reach — the main indicator of the genre. Below 1.40 — racing frame, 1.40–1.50 — endurance, 1.50–1.60 — gravel and comfort, above 1.60 — very high fit for touring and luggage.
Trail (trail removal) = (wheel radius × cos HTA − fork reach) - sin HTA. We take the radius according to ETRTO: π × (rim + two tire widths) ÷ 2π. More trail — the steering wheel is calmer and keeps a straight line itself, less — sharper in turns. The difference of more than 8 mm is felt immediately.
Front center ≈ wheelbase − the length of the feathers. Its share in the base shows the weight distribution: the larger it is, the more the weight is shifted back and the less the front wheel is loaded.
We translate the glass into spacers by 7mm: 10 mm stack ≈ 1.5 spacers. Reach — in take-out: 10 mm reach ≈ take-out is 10 mm shorter or longer. One degree of the seatpost at a saddle height of about 700 mm is 8-10 mm of horizontal displacement of the saddle, played out by rails or a seatpost with another offset.
Everything is calculated by the numbers from the tables: if the manufacturer measures stack and reach from another point, the comparison will go. Make sure you take the numbers for the same size and the same fork.