People often ask if Thule roof bars or roof boxes are universal. Roof bars are not universal. Roof boxes are widely compatible once you have the right bars. This guide shows you how to identify your roof type, choose the correct bar and box, size everything for real journeys, and travel safely.
Jump to section
- Are Thule roof bars universal?
- Which roof type do I have?
- Are Thule roof boxes universal?
- Do they fit hatchbacks, estates, SUVs and vans?
- What size roof box do I need?
- Weight limits and safety
- Common questions answered
- How to choose the right setup
- Why buy from GT Towing
Are Thule roof bars universal?
No. Cars use different roof designs and approved fixing points, so a one size bar will not fit. Thule solves this with a modular system that you match to your exact car. You select the bars, the foot pack, and a vehicle specific fitting kit. Get those three right and you have a secure, quiet and paint safe installation for daily use and long trips.
Tell GT Towing your make, model and year and we will specify the correct combination and supply everything as a single package.
Which roof type do I have?
Your roof type determines the foot pack and fitting kit you need. Check it in seconds on the driveway using the guide above.
Roof rails. Raised rails run along each side of the roof with a visible gap underneath. Common on estates and SUVs. Bars clamp around the rail.
Normal or bare roof. No rails and no visible fixing points. Bars use a door frame clamp kit designed for your exact car. Safe fit with no drilling.
Fixed points. Small covered anchor points built into the roof. Feet bolt into these points for a factory style installation that is very secure.
Flush rails. Integrated rails that sit flush with the roof. No gap underneath. You need a specific foot pack and fitting kit that locates on set points.
T track. A channel in the roof or rails that accepts sliding bolts. Neat finish and common on some premium models.
Rain gutter. A raised gutter along the roof edge. Seen on some vans, older cars and 4x4s. Brackets clamp to the gutter to hold the bars.
Not sure which you have. Send GT Towing your make, model and year and we will confirm your roof type and the exact kit you need.
Are Thule roof boxes universal?
Roof boxes are widely compatible once you have the right roof bars. Work through the checks below to get a perfect match and a quiet drive.
Bar type and attachment. Thule roof boxes are designed to work with modern aero bars and with square bars when used with the correct clamps or adapters. If you prefer a T track channel, many boxes include or accept T track fittings. If in doubt, we will confirm the best pairing for your car and bars.
Bar spacing. Every box lists a minimum and maximum bar spread. Your bars must sit within that range so the load is supported correctly. If the bars are too close together, the box can feel bouncy. If they are too far apart, the mounting points may not align. On hatchbacks and many estates, measure hatch clearance so an open tailgate does not touch the back of the box.
Bar width and depth. If you are not using a T track, check that the box clamps open wide enough for your bars. This is rarely an issue with modern Thule bars, but it is worth a quick check before you buy.
Real world clearance and height. Before tightening everything down, mock up the box position with your tailgate fully open. Check total height for car parks and garages.
Do they fit hatchbacks, estates, SUVs and vans?
Hatchbacks. Often use bare roof kits or flush rails. A medium box balances space and everyday practicality. Choose a position that clears the tailgate and keeps the load central between the bars.
Estates. Commonly have raised rails and a wider bar spread. This supports longer boxes and bulkier loads for holidays and sports kit. Avoid pushing a long box too far forward or wind noise can increase.
SUVs. May have raised or flush rails. The extra height suits larger boxes, but watch overall height for car parks and garages. A slightly shorter box can be easier to load at shoulder height.
Vans. Often require van specific bars and careful load management. If you carry ladders or long loads, ask us for a safe setup that respects roof load limits and handling.
What size roof box do I need?
Choose a capacity that suits what you actually carry and the space on your roof. Use this as a guide, then check bar spacing and tailgate clearance.
- Small 300 to 360 litres. Weekend trips, light loads and city cars. Easy to store and park.
- Medium 400 to 480 litres. Best all rounder for families. Takes buggies, soft bags and sports kit without making parking a chore.
- Large 500 litres plus. Camping and long holidays. Ideal for estates and SUVs with generous bar spread. Check height limits for multi storey car parks.
Practical tip. Lay your typical luggage on the driveway and measure the footprint. Compare with the internal size of the box so you know it fits in practice, not only on paper.
Weight limits and safety
Stay within the lowest limit of three figures. Your vehicle roof load rating, your roof bar rating, and your roof box rating. The vehicle figure is in your handbook. Add the weight of the bars, the weight of the box, and the weight of your luggage. Keep the total at or below that lowest number.
Example calculation. Vehicle roof load 75 kg. Bars 5 kg. Box 15 kg. Luggage allowance is 55 kg. 75 minus 5 minus 15 equals 55. Pack within that figure.
Packing advice. Place heavier items in the centre of the box and keep weight balanced left to right. Use the internal straps for every trip. Recheck fixings after 30 to 50 miles and at fuel stops on long drives.
On the road. Reduce speed in crosswinds and wet conditions. Avoid sudden manoeuvres. Be mindful of extra height when entering car parks and drive throughs.
Common questions answered
Is there a universal fitment?
No. There is no single bar or kit that fits every car. Thule covers most vehicles with model specific fitting kits that pair with the correct bars and foot pack. The result is a safer, quieter setup that protects your paint and your gear.
Do roof bars damage paint?
Not when the correct kit and positions are used and contact areas are clean. Follow the fitting guide and retighten as instructed.
Are roof boxes waterproof?
Quality boxes are highly water resistant for typical British weather. For very heavy rain, pack soft items in dry bags or bin liners as a backup.
Are aero bars quieter?
Yes. Aero profiles reduce wind noise compared with square bars. Correct spacing and position also help.
Can I use a panoramic roof?
Often yes, but do not open the roof with bars or a box fitted unless the car maker explicitly allows it.
Will a roof box affect fuel use?
Any roof load increases drag. Keep speeds sensible, remove the box when not in use, and consider an aero shaped box to minimise impact.
How to choose the right setup
Follow this process and you will get it right first time.
1. Identify your roof type.
Roof rails, flush rails, fixed points, bare roof, T track or rain gutter.
2. Check your roof load rating.
The handbook figure is the hard limit.
3. Pick your bar style.
Aero bars are quiet and efficient for daily use.
4. Confirm the correct foot pack and fitting kit.
Match to your exact make, model and year.
5. Select the box size.
Base it on real luggage and available bar spacing. Double check boot clearance.
Why buy from GT Towing
We stock Thule roof racks and roof boxes, provide clear advice, and can fit your system for you. Tell us your car details and we will recommend a safe, compliant setup with straightforward options.
Shop Roof Racks Shop Roof Boxes Ask us for the right kit