The two-day test is the latest step in Pirelli’s programme of no-blanket slick running, although it is set to be compromised by rain.

Pirelli’s hope was to introduce the new tyres in 2024, but at last Friday’s F1 Commission it was agreed to postpone the move to remove blankets, and then have another look for 2025.

The decision came too late for Pirelli to change its run plan for Spa, and thus the focus of the test will remain on the no-blanket tyres, with a view to gathering more data for possible introduction in 2025.

However, the catch is that Pirelli doesn’t know if it will still be the official F1 tyre supplier for that season, as it faces a challenge from Bridgestone for the contract that runs from 2025 to 2028.

A decision on the tender is expected during the summer break. If Bridgestone gets the nod then Pirelli’s no-blanket programme will instantly become obsolete as the company won’t be in F1 in 2025.

The Spa test will in effect be rendered worthless, at least in terms of any slick running.

Pirelli will then be able to focus its efforts in any remaining tests this season - including a session at Monza after the Italian GP - on preparing the best possible standard tyre for 2024.

Given that the focus of its testing this year has been on running with no blankets Pirelli has dedicated less resource than usual to developing tyres with blankets for 2024, and dealing with the annual increase in downforce levels and general performance that the teams achieve.

It has now to produce a tyre that will be able to cope with the load levels predicted for the final race of the 2024 season.

“Because now we know that the no-blanket tyres have been postponed to 2025 we have also to understand if we need to make any modifications to the current product for next year,” said Pirelli F1 boss Mario Isola when asked by about the test programme.

Mario Isola, Racing Manager, Pirelli Motorsport at Miami GP 2023

“So we have to review all the plan, and we have obviously to consider tyres for 2024, as in any case we are here, so if we need to make any modification to the current product for next year, to improve compounds or to fine tune the delta lap time or whatever.

“If we are confirmed for 2025, we have to develop also the no-blankets, and we have to understand what to do for the wet weather tyres.”

Asked if Pirelli still has time to turn next month’s Monza session into a test of standard tyres for 2024 he said: “That's a good question. I have to check. I don't know yet! But we are not in summer shutdown, so we can make some prototypes.”

If it does rain consistently through the two days of Spa testing this week Pirelli will at least have a chance to test its latest development wet and intermediate tyres.

“We are hoping that we have some rain during Tuesday and Wednesday,” said Isola. “So that we have the possibility also to compare the current intermediate with the one that we want to homologate for next year. That is a good opportunity."

The downside of having only two cars running is that they won’t clear the water, but on the other hand spray is less of an issue, especially if the cars are deliberately kept well apart on the track.

In theory that means the drivers could do some more extensive track running on full wets than was possible last weekend, when visibility with a full field on track was a key factor.

"We also consider that for example Tuesday and Wednesday that we have two cars running, you can send out the two cars at a certain distance,” said Isola.

“So you have a condition on the track that is comparable. And you can test two different types of tyres.

“Then you have to consider that you have two cars that are not the same, and different drivers so that that's another variable that you should when you analyse the result."

Pirelli tyres at Hungarian GP 2023

It remains to be seen how relevant this week’s running is for the two teams involved.

Usually any track mileage gained in-season is useful, and Aston Martin is taking the opportunity to give Wednesday to test and reserve driver Stoffel Vandoorne, which will help the Belgian with sim correlation as well as making him better prepared to step in if required.

However, the testing is run by Pirelli and there are strict rules on what car configuration can be used.

For example having been stuck with an unfavourable high downforce level for the Belgian GP race weekend McLaren can’t use the test to gather data with a lower drag spec.

“In terms of the drag level, actually, that's not very relevant, because it's not like we have another configuration that we can run,” said McLaren’s Andreas Stella when asked by about the value of the test.

“Otherwise, we will have run it here in Spa during the race weekend. Anyhow, you have to run configurations that have run before at race events during a tyre test.

“In terms of the relevance of the test, I was actually discussing [on Sunday] morning with our director of engineering like we were hoping to have some good weather so that we can do some work that can be useful for Pirelli in the future. We will be I think a bit at the mercy of the weather again.”

Aston performance director Tom McCullough said the test could still be useful, especially if Pirelli does win the tender and its no-blanket tyres are required in 2025.

"Obviously with Pirelli we're always looking to support and develop the tyres,” he said. “We are always interested to see what Pirelli bring, they're always bringing tyres.

“The [blanket] decision was always going to be on Friday. But who says in a year's time, we will not go to those?

“For them going to lots of different duty cycle tracks, with all the different tyres getting that input, it's just useful for Pirelli to keep learning and keep improving."