The vehicle selector on a tent maker's own site carries a line most buyers scroll past: the tool does not consider the bar spread of your vehicle, and you are told to go measure your rack yourself. Read that as a sourcing person and the green compatible tick you were about to paste into an RFQ attachment starts to look thin. It is missing exactly the measurement that decides whether the tent's rails land on both crossbars.
For a US buyer sourcing a custom rooftop tent, that one admission reshuffles the shortlist. The load figure printed on the tent is not fitment evidence. What separates a real candidate from a fast one is whether the supplier refuses to issue a fitment statement until the vehicle maker has confirmed the roof can carry the tent and until you have measured bar spread. The guidance behind these questions comes from a single manufacturer's instructions for its own tents and racks, so read it as the source of the questions to ask rather than a rule for every vehicle and every tent. Which raises the question that runs through everything below: if the tool cannot settle fitment, who can?
Your Fitment Tool Skips the Bar Spread
Start with what that tool actually does. It maps a vehicle to a product family. It never measures the distance between your two crossbars, and the same installation guide that sends you to the selector tells you to measure your rack's bar spread to confirm compatibility. A selector result is a filter, not a fitment conclusion.
Why does that omission outweigh the load number on the tent? Because bar spread is the dimension that decides whether the mounting rails land on both crossbars with the overhang the design was drawn around. Rails that meet one bar cleanly and reach the second at the wrong point change how the load travels into the rack. A tent can be rated perfectly and still sit on your vehicle in a way nobody has checked.
So bar spread becomes a numbered line in your RFQ that you fill in, not a value the supplier hands you. You measure, you record it with the date and the rack model it belongs to, and you attach it. A candidate that offers to skip that line is telling you what its fitment statement is worth.
Which leaves a sharper question: if the measurement is yours to take, whose word does the roof itself need first?
Glass Roofs Need the Vehicle Maker's Word
The answer depends on what the roof is made of, and for some vehicles the question stops the project outright: is the roof glass or a large panoramic panel? For those roofs the instruction is blunt. Always check with your vehicle manufacturer to confirm the roof can support the weight of a rooftop tent.
That sentence is doing more work than it looks like. A tent maker's load figure describes the tent and its own hardware; it says nothing about the panel bonded into your car's roof, and the tent maker is not the party who validated that panel. The question belongs to the vehicle, so the answer has to come from the vehicle's maker.
Practically, this turns into an RFQ item that tests the supplier rather than the tent: which vehicle-side document do you require before you will state fitment for this model? A candidate that names the vehicle maker's roof-load confirmation is answering the question you asked. A candidate that says none is needed has just told you it will write a fitment statement about a roof it has never assessed.
On a panoramic roof, that reply can end the evaluation before samples are ever discussed. Which pushes the next question: if the roof question belongs to the car maker, who owns the question of the bars?
When the Rack Manual Outranks the Tent Spec
The bars come with their own paperwork. For other roof rack brands, or factory-installed racks from your car manufacturer, compatibility is determined by checking that rack's manual.
There is an ordering buried in those three instructions, and it is the most useful thing a procurement team can lift from them. Vehicle-side roof load comes first, because a glass roof can stop the project outright. The rack's own manual comes second, because compatibility is a property of the rack, not of the tent. The tent specification comes last. Buyers routinely read that order backwards, starting with the tent's spec sheet because it is the document the supplier sent them.
The ordering has an immediate consequence for how you write the RFQ: you cannot ask a supplier a compatibility question about an unnamed rack. Will your tent fit my vehicle is unanswerable. Will this tent, on this rack, on this roof, at this measured bar spread is a question with a document trail behind every clause. So what does that ordering do to how you shortlist?
The Three Questions That Order an RFQ
Write the questions in the order the documents sit, and gate each one: no fitment statement without an answer.
First, roof type and vehicle-side roof load. Ask it first because of the ceiling it sets on everything downstream. If the vehicle maker will not confirm the roof, no tent specification rescues the project. Second, rack identity and the rack manual. Ask for the exact rack, aftermarket or factory, and ask the supplier to state compatibility against that manual rather than against a vehicle name. Third, measured bar spread, which is your own input and cannot be delegated to anyone in the supply chain.
The sequence matters more than the wording because of what it prevents. A supplier that answers the third question while skipping the first has produced a compatibility statement for a roof nobody cleared. A supplier that answers the second with a vehicle name instead of a rack identity has answered a different question than the one asked. Ordering the RFQ this way makes each skip visible in the reply, before you spend a dollar on samples.
That is the framework: three gates, fixed sequence, each with a named document behind it. Which leaves the practical question every sourcing lead asks next — what do real replies to those gates look like, and which ones survive?
What a Supplier's Answer Reveals Before Samples
Suppose three candidates answer the same RFQ. None of what follows is a real company; treat these as reply patterns you will recognize.
Pattern one asks for vehicle make, model and roof type. It states plainly that it needs the vehicle maker's roof-load confirmation and a measured bar spread before it will put a fitment statement in writing, and it offers its tent-side specification in the meantime. It is the slower reply, and it tells you the supplier knows which document owns which question.
Pattern one goes to sampling.
Because when that supplier finally signs a fitment statement, the statement rests on a vehicle-side confirmation and a buyer-measured dimension that your own QC file can point to years later, which is precisely what a warranty claim or a liability conversation requires and what a friendly verbal yes from a sales inbox will never supply.
Pattern two quotes fitment in the first reply, adds a line about fitting most roofs, and produces no vehicle-side document because none was asked for. Its tent-side specification may be the most complete of the three.
Pattern two is struck on the reply alone.
The tent may well be fine; the answer is to a question about a product family while yours was about one roof, one rack and one measured span, and a supplier that closes that distance with an adjective hands your QC team a clause it cannot enforce when the first unit lands and the rails sit wrong.
Pattern three stays in a holding pen. It sends tent-side specs, declines to discuss the vehicle roof at all, and offers to support whatever the customer decides. That is a legitimate tent-only candidate — canvas, frame, hinge, packaging — but it is not yet a fitment candidate and should not be scored as one.
Which of the survivors actually gets the order, and what does choosing it cost?
Recommend One, Exclude Another, Count the Cost
Award to pattern one. Strike pattern two regardless of how polished its tent-side paperwork is, and keep pattern three open only for the components it can genuinely answer for. The reasoning is not that pattern one is friendlier to work with; it is that pattern two is answering a question about tents while the risk sits up on a roof.
Now the tradeoff, said plainly. Choosing this way costs you speed and the comfort of one SKU marketed across every roof in the catalog. Your RFQ cycle stretches by however long the vehicle-side answer takes, plus the short trip up a ladder with a tape measure. You give up the tidy quote that arrives fast with a fitment line already filled in.
What you get in exchange is a specification your quality team can defend: a fitment statement that traces to a vehicle maker's confirmation and to a measurement you took yourself, dated, on a named rack. When a unit comes back with a complaint, you are arguing from documents instead of from a brochure.
Several things stay open and belong in the RFQ as questions rather than assumptions: the supplier's actual custom capability, minimum order quantity, price, lead time, available tooling, and any certification it claims. Nothing here establishes those for any specific supplier. Sample test conditions, tolerances and acceptance thresholds also have to come from model-specific documentation and from what both sides agree in writing, not from a general statement about the category.
So the last question is the one you carry into the next supplier call. What does this supplier need from my vehicle, from my rack and from my tape measure before it will sign off on fitment in writing? If the answer is nothing, you already have your exclusion.