Books for the share sale were due to close at 1200 GMT.
At 6.5 euros per share, Pirelli, which is offering up to 40 percent of its shares, would be valued at 6.5 billion euros (5.72 billion pounds)- well below a maximum valuation of 8.3 billion euros initially targeted when the offer opened last week.
Established in 1872 and one of Italy's best-known corporate names, Pirelli is expected to return to the Milan stock exchange on Oct. 4 in one of the biggest IPOs in Europe this year.
The sale of shares in the maker of tyres for Formula One races and upmarket brands such as Mercedes, Audi and BMW will raise between 2.3 and 2.6 billion euros for the current owners depending on whether its bankers exercise an over-allotment option in the offer.
The world's fifth-largest tyremaker was de-listed in 2015 from the Milan bourse, where it had traded since 1922, following a takeover led by state-owned China National Chemical Corp (ChemChina).
The re-listing will test demand for a streamlined firm that focuses on high-end tyres for the consumer market after its less profitable truck and industrial tyre business was folded into a unit of ChemChina.
Bankers involved in the IPO had initially set a price range of 6.3 euros to 8.3 euros per share for the offer, already slightly lower than core investors had hoped for.
That range was narrowed to between 6.5-6.7 euros per share on Wednesday, reflecting investors' concerns over Pirelli's debt pile, complex governance structure and risk that one of the existing minority shareholders could sell out once a lock-up period expires.
ChemChina took over Pirelli two years ago by acquiring a 65 percent stake in Marco Polo, the holding company controlling the tyre maker. It will remain by far the biggest shareholder after the IPO with a stake of just under 50 percent.
Pirelli boss Marco Tronchetti Provera and banks UniCredit (>> UniCredit SpA) and Intesa Sanpaolo (>> Intesa Sanpaolo) hold around 22 percent of Marco Polo via their holding company Camfin and will see that stake cut to between 10 and 12 percent. The rest is held by investment fund LTI, linked to Russia's Rosneft (>> NK Rosneft' PAO), which will drop to 5 and 6.6 percent after the share sale.
Pirelli is more profitable than France's Michelin (>> Michelin) and Germany's Continental (>> Continental), but its core profit margin of around 20 percent lags that of high-end Finnish rival Nokian (>> Nokian Renkaat Oyj), which stands at nearly 30 percent.
Through its focus on premium tyres, which it expects to account for 63 percent of sales by 2020, Pirelli is less exposed to economic downturns than in the past because that segment has proven less cyclical.
But others, such as South Korea's Hankook (>> Hankook Tire Co Ltd), have followed suit, intensifying competition in that market.
Pirelli's targeted average revenue growth of at least 9 percent per year between 2016 and 2020 is doable but ambitious, according to analysts. Some have also raised concern about its heavy debt load as well as management succession, with long-standing CEO Tronchetti Provera set to retire after 2020.
A question mark also remains over the role the Chinese will play at the company after the IPO, although Pirelli has repeatedly said ChemChina has taken a passive approach to its management.
(Writing by Agnieszka Flak; Editing by Silvia Aloisi, Greg Mahlich)
By Elisa Anzolin