With wider and heavier lift-slide doors you often see: the door runs heavier, feels less stable, or loads the rail at one point. In those situations, the tandem GU 934 is the right extension.
This set is applied for doors from approx. 2 meters wide, and always in combination with the basic carriage package GU 934.
When do you use a tandem GU 934?
The tandem solution is used for:
✅ Doors from ± 2000 mm wide
✅ Heavy glass fillings (HR++, triple glass)
✅ Doors that run stiff despite adjustment
✅ Situations where extra weight distribution is needed
✅ Preventive upgrade against wear
For wide doors, the weight simply becomes too great to rely optimally on one standard carriage setup. By a tandem construction, you distribute the load over multiple wheels.
How does the tandem solution work technically?
The tandem GU 934 is not used separately, but connected to the basic carriage package GU 934.
🔧 Connection with connecting rods
The tandem set is mechanically connected to the basic carriage package with connecting rods.
This results in:
✅ Equal pressure distribution
✅ Synchronous movement of the carriages
✅ Stable support across the width of the door leaf
✅ Less point load on the running rail
The connecting rods ensure that both carriage units function as one whole. This is crucial for wide doors — otherwise one set would still bear most of the load.
Why from 2 meters wide?
For doors under 2 meters, the weight is usually still manageable with one standard GU 934 carriage set (if correctly adjusted and rail in good condition).
From 2 meters wide, the following increases:
✔the glass surface
✔the total weight
✔the lifting load
That is why we almost always recommend a tandem setup from this width.
What should you pay attention to before installation?
Always check:
✅ Rebate height 57 mm (characteristic for GU 934)
✅ The size of the undergroove for correct carriage selection
✅ Condition of the running rail (replace if deeply worn)
✅ Free movement of the corner transmissions
Note: new carriages on a damaged rail never give the optimal result.
🔧 Practical assembly order – Tandem GU 934
With a tandem GU 934, the assembly order is crucial. If this is not done correctly, the lifting will not work properly and the system can block or run unevenly.
1️⃣ First assemble the complete set outside the door
First assemble the complete system outside the rebate:
1. Basic trolley package GU 934
2. Tandem set
3. Connect the connecting rods
Make sure everything is mechanically correctly connected and can move freely.
⚠️ So do not first mount the base in the door and then the tandem. The whole must be assembled as one system.
2️⃣ Place the entire tandem system in the rebate
When the complete system is assembled, place the whole in the existing rebate of the door leaf.
Note:
✔Check if the opening is clean
✔No burrs or deformations
✔Everything must fit without tension
3️⃣ First set everything "at the same time" (very important)
Before you fasten even one screw definitively, you must:
✅ Both trolley units are in the same position simultaneously
✅ The lifting system moves synchronously
✅ The connecting rods do not build up tension
If one side lifts earlier than the other, then:
❌ The system blocks
❌ The lifting movement becomes uneven
❌ Extra load occurs on the corner transmission
This is a common mistake in tandem assembly.
So really take your time here.
4️⃣ Then fasten definitively
When everything is synchronized and moves correctly:
✔Tighten screws definitively
✔Check the lifting movement again
✔Then hang the door and adjust the height
5️⃣ Final check
Check:
✔ Full lifting movement
✔ Equal pressure distribution
✔ Smooth sliding over the entire rail
✔ No binding or scraping noise
Why this order is so important
The tandem GU 934 is used for doors from 2 meters wide. The weight is considerable, and when the system is not perfectly synchronized, the force is unevenly distributed.
By:
✔first assemble completely
✔only then place in the rebate
✔set everything simultaneously on time
✔and then fasten
prevents malfunctions in the lifting mechanism.
Summary
The tandem GU 934:
✅ Is used for doors from 2 meters wide
✅ Is connected to the basic trolley package GU 934
✅ Is assembled as one system with connecting rods
✅ Must be fully assembled before placement in the rebate
✅ Must be synchronized "on time" before final fastening
This is essential for a properly functioning lift-slide door.
