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 Most makers do not publish it, so I assume 10 mm and add 6 mm to the band beside every answer.
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
LightCarbon LCTT25
Time trial · 4 sizes
Sign in and add the bike you ride, and this table will say what each size needs for your position.
Sign in
This is the bike I ride
No account is needed to read the table. Report a wrong number · Correct this bike
- Bike
- LightCarbon LCTT25 · Time trial · 4 sizes · integrated cockpit
- Geometry
- lightcarbon.com, fetched 20 Oct 2026, read off the maker's chart, re-checked, no differences
- Cockpit
- Generic stem and bar, assumed
- Solved with
- cover 10 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 · 879 bikes, 79 makes, 4,979 sizes in the catalogue
Geometry, every size, from the maker's table
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 54 / 540 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.
Frame facts
read from the maker's words, not a table: lightcarbon.com- Tyre clearance
- not recorded yet
- Bottom bracket
- T47
- Axles and brakes
- 12x100 / 12x142, flat mount
- UDH
- yes
- Seatpost
- proprietary
- Frame weight
- 1600 g
In the maker's words
Kept whole, as I read it off lightcarbon.com.The page's own specification table, verbatim: Frame: LightCarbon 700C Ultra Aero Triathlon Disc Brake Carbon Frame Set; Material: High modulus T700 + T800 grade carbon fiber; Size: 49/52/54/56cm; Fork: LightCarbon specific aero carbon fork; Headtube: Integrated headtube 42/42mm (FSA NO.8B standard headset); Weight (±4%): frame 1600g/54cm; fork 700g; Seatpost: LightCarbon specific aero seat post; Bottom bracket: Threaded T47 * P1.0 (86.5mm width); Max tire clearance: 700*28C (Width As Measured); Handlebar width: 400mm / 420mm; Stem length: 100mm; Brake type: Disc Brake: Flat Mount, rear 140mm / front 160mm rotor; Dropout: Front 12*100mm TA, Rear 12*142mm TA, UDH hanger; Groupset: Mechanical and Di2 compatible; Test Standard: ISO4210; Warranty: 2 years.
Cockpit and seatpost, in the maker's words · 109 words
The page's own specification table, verbatim: Frame: LightCarbon 700C Ultra Aero Triathlon Disc Brake Carbon Frame Set; Material: High modulus T700 + T800 grade carbon fiber; Size: 49/52/54/56cm; Fork: LightCarbon specific aero carbon fork; Headtube: Integrated headtube 42/42mm (FSA NO.8B standard headset); Weight (±4%): frame 1600g/54cm; fork 700g; Seatpost: LightCarbon specific aero seat post; Bottom bracket: Threaded T47 * P1.0 (86.5mm width); Max tire clearance: 700*28C (Width As Measured); Handlebar width: 400mm / 420mm; Stem length: 100mm; Brake type: Disc Brake: Flat Mount, rear 140mm / front 160mm rotor; Dropout: Front 12*100mm TA, Rear 12*142mm TA, UDH hanger; Groupset: Mechanical and Di2 compatible; Test Standard: ISO4210; Warranty: 2 years.
SOURCE: www.lightcarbon.com is LightCarbon's own site (Xiamen LightCarbon Technology Co., Ltd). Source: html table (maker's own product page, a real HTML geometry table with named rows; parsed from the raw HTML, no image used)
How I read the maker's table
the product page "LightCarbon Ultra Aero Triathlon Carbon Frame Disc Brake 700C Carbon Fiber TT Bike Frameset" (item no. LCTT25) publishes the geometry as a real HTML table with named rows, parsed from the raw HTML. ROW MAPPING: REACH, STACK, WHEELBASE, CHAINSTAY LENGTH, FRONT CENTER, BB DROP, SEAT TUBE ANGLE, HEAD TUBE ANGLE, SEAT TUBE LENGTH, HEAD TUBE LENGTH, FORK RAKE/OFFSET and TRAIL map one to one; "TOP TUBE LENGTH, HORIZONTAL" is top_tube_effective; "BIKE STANDOVER HEIGHT(700C*28C)" is standover (the tyre the maker measured it with is in the row name). Rows not in the schema, kept here: Seatpost Insert Length 200mm / 230mm / 245mm / 260mm; Bb Height 270mm / 270mm / 270mm / 270mm; Fork Length, Full 372mm / 372mm / 372mm / 372mm. Body-height bands are printed per size "for reference only". STACK DATUM: not stated; recorded as the usual head tube top. SIZE LABELS: the geometry table heads its columns 490 / 520 / 540 / 560 and the spec table lists "49/52/54/56cm"; size_label carries both as "cm / mm". Triathlon frameset with an integrated 42/42 mm head tube and LightCarbon aero bar (handlebar width 400 or 420 mm, stem 100 mm, per the spec table); the base bar and extension geometry are not published, so no cockpit geometry is recorded. A geometry drawing (alt "LightCarbon Disc Brake Triathlon Carbon Frameset LCTT25 Geometry") sits above the HTML table; the HTML table was used. The maker prints trail 73.8 / 58 / 64.8 / 64.8 mm with head angles 70.5 / 71 / 72.5 / 72.5 deg and one 43 mm offset: 490, 540 and 560 follow the head angle (a steeper head angle gives less trail) but 520 at 71 deg prints 58, less than the 72.5 deg sizes, which looks like a maker slip (about 71 would fit); kept as printed. TOP TUBE: the printed horizontal top tube (507 / 513 / 541 / 570) is 6-17 mm shorter than reach + stack / tan(76) on every size, so the 76 deg seat angle and the top tube are not drawn to the same seat tube line (a triathlon frame often prints an effective angle to a forward saddle position); the seat angle check will flag it and nothing was changed. MODEL YEAR: not printed; model_year null. No Panda Podium, Geometry Geeks or 99 Spokes request was made.