LT50 and LT60 are not two model names. They are two mechanical platforms, and the number is the motor body diameter in millimetres. Everything that matters downstream — the tube you can use, the crown and drive set, the bracket, the torque you can reach — follows from that one dimension. Get the platform wrong and no accessory in the catalog will rescue the order.
The two numbers that decide it
LT50 motors need a tube with at least a 1.85 in inside diameter. LT60 motors need at least 2.37 in.
That is the whole decision in one line. If the tube is already cut and installed, measure the inside diameter and the platform is chosen for you. If the tube is not yet ordered, size the load first, find the torque you need, and let that pick the platform — then order the tube to suit.
Where each platform runs out
Every figure below is from Somfy's published record for that exact part number.
| Motor | Part | Platform | Torque | Speed | Min tube ID | Head |
|---|---|---|---|---|---|---|
| Altus RTS 525A2 | 1043423 | LT50 | 25 Nm | 20 rpm | 1.85 in | Star |
| Altus RTS 550R2 | 1038170 | LT50 | 50 Nm | 14 rpm | 1.85 in | Star |
| Altus RTS 660R2 | 1162271 | LT60 | 60 Nm | 14 rpm | 2.37 in | Star |
| Altus RTS 680R2 | 1164261 | LT60 | 80 Nm | 14 rpm | 2.37 in | Star |
| Altus RTS 6100R2 | 1166289 | LT60 | 100 Nm | 14 rpm | 2.37 in | Star |
Sources: Somfy's product records for 1043423, 1038170, 1162271, 1164261 and 1166289. All five are rated IP 44.
The overlap is narrower than people expect
LT50 tops out at 50 Nm. LT60 starts at 60 Nm. There is no overlap at all in the Altus RTS range: the platforms meet at a gap, not a shared band.
That matters when a load sizes out at, say, 55 Nm. There is no LT50 motor that covers it. The job moves to LT60, and with it the tube, the crown, the drive and the bracket. Budget the whole platform change, not just the motor.
Both platforms turn at 14 rpm at the top of their range, so stepping from a 550R2 to a 680R2 buys you 60 percent more pulling power at identical speed. That is unusually clean — within most Somfy families, more torque costs rpm. Here it does not, because the bigger body absorbs it.
What does and does not cross over
Does not cross over. The motor body, obviously. Also the crown, which seats against the tube's inside wall and is cut for one body diameter. An LT50 2.5 in crown (9707026) and a 70mm octagonal LT60 crown (9705340) are not substitutes for each other in either direction. Brackets follow the body too: an LT50 universal motor bracket (9410665) will not carry an LT60 motor.
Sometimes crosses over. A handful of drives are built for both, and Somfy names them accordingly — the LT50/60 octagonal 70mm drive (9761002) and the 60mm round LT50/60 aluminum drive wheel (9012950) both carry the shared designation. If the part number does not say LT50/60, assume it does not cross.
Always crosses over. The controls. Both platforms in the Altus RTS range run 433.420 MHz rolling-code RTS, so the same Situo and Telis remotes, the same DecoFlex switches and the same TaHoma hub drive either one. Nothing about the control side changes when you step up.
Our crowns, drives and brackets guide works through how the three parts fit together.
Head type: check it separately
All five motors in the table carry a star head, which is the common case on the exterior platforms. That is convenient, but do not generalise it. Head type is a per-part specification, not a platform one — elsewhere in the Somfy range the Sonesse ULTRA 50 DC motors use a square head, and a star bracket will not hold one. Confirm the head on the listing before ordering the bracket, every time.
Which platform for which job
LT50 covers most residential exterior work: cassette awnings, standard rolling shutters, zip screens and folding-arm awnings on normal residential spans. The range runs from 6 Nm through 50 Nm, so there is a lot of room inside it, and the 1.85 in tube requirement suits the tubes most residential systems already use.
LT60 is for the heavy end: large rolling shutters, wide commercial awnings, oversized security shutters and anything where the sized load has already passed 50 Nm. It is not the default choice and does not need to be — oversizing to LT60 means a bigger tube and a bigger headbox for no benefit.
The rule of thumb: size the load honestly, add your safety margin, then pick the smallest motor that covers it. If that number is above 50 Nm, you are on LT60 and the tube spec changes with it.
Common questions
Can an LT60 motor fit in a tube sized for LT50?
No. LT60 needs a minimum 2.37 in inside diameter against LT50's 1.85 in. A tube cut for LT50 will not accept an LT60 motor, and no adapter changes that.
Is there an LT50 motor above 50 Nm?
Not in the Altus RTS range. 50 Nm (part 1038170) is the top of the platform. Above that the job moves to LT60.
Do LT50 and LT60 use the same crowns and drives?
Crowns, no. A few drives are built for both and say so in the part name, such as the LT50/60 octagonal 70mm drive (9761002). If the name does not say LT50/60, treat it as platform-specific.
Does stepping up to LT60 make the shade slower?
No. The Altus RTS 550R2, 660R2, 680R2 and 6100R2 all run 14 rpm. You gain torque at the same speed.
Can I use the same remote on both?
Yes. Both run RTS at 433.420 MHz, so every Somfy RTS remote, wall switch and TaHoma hub works with either.
Every figure above is taken from Somfy's published record for the specific part number, linked in the sources line. Browse exterior motors in Awning & Exterior Motors, and the fitment parts in Motor Accessories.
