As Lyft and Uber prepare for multibillion-dollar Wall Street debuts, the ride-hailing companies face rising tensions with their drivers, the independent contractors who are the backbone of both services. Some drivers are joining forces, both online and in person, to voice grievances about their pay and other working conditions.

Driver protests, though small, expose a critical weakness of ride-hailing companies’ business models. They depend on an independent contractor workforce of drivers, but their best paths to making money are to cut those drivers’ pay, which could cause drivers to flee; or to raise riders’ rates, which could decrease demand.

On Monday, waving homemade signs and banners and chanting about their desire for a living wage, about 60 drivers staged a protest outside San Francisco’s Omni Hotel, where Lyft was reportedly holding meetings to pitch investors on its initial public offering, expected this Friday.

“Drivers are not getting a fair deal,” said Emmanuel Oditah of Vallejo, who’s driven for three years for both Uber and Lyft. “Pay has gone down.”

Oditah, who has three children and whose wife works as a caregiver, said he used to earn about $1,700 to $2,000 before gas and other expenses for a 40-hour week of driving. “Now for 50 to 60 hours, I barely make $1,200 to $1,300,” he said.

Also on Monday, some drivers for Lyft and Uber in Los Angeles and San Diego staged temporary strikes over pay issues. The three actions were coordinated by labor-backed groups — Gig Workers Rising in San Francisco and Rideshare Drivers United in Southern California — that are helping drivers organize.

Monday’s activities resemble some other recent gig-worker crusades that wrung concessions, such as Instacart drivers’ successful quest for the grocery-delivery company to backtrack on how it apportioned tips. Uber and Lyft drivers in New York won a law guaranteeing them at least $17.22 an hour after expenses ($26.51 before expenses) after two years of protests with the Independent Drivers Guild, a union-affiliated group.

Several analysts have pointed to the ride-hailing companies’ conundrum. The issue is especially stark now with Lyft’s initial public offering coming Friday, and Uber expected to follow suit to the public next month. Although neither company has ever turned a penny of profit, both seek sky-high valuations on Wall Street. Lyft last week said it expects to be worth up to $23 billion, with shares going for $62 to $68 each as it seeks to raise about $2 billion. Uber could be worth as much as $120 billion.

“Lyft faces an all-but-insurmountable barrier to positive earnings,” wrote CTW Investment Group, a union pension-fund adviser, in a letter to potential investors last week. “Absent a price increase, Lyft can only become profitable by reducing the drivers’ share of revenue.”

CTW said that Uber has the same challenge. “Uber’s financial data indicates that the market-dominant company cannot sustainably push driver pay low enough to ensure profitability,” it said.

Lyft said its Driver Advisory Councils provide a forum for drivers to communicate with it, and noted that most drivers work for it only temporarily and part time.

“Lyft has a strong track record of helping drivers increase their earnings, and has led the industry in initiatives like in-app tipping, same-day payments, access to affordable rental vehicles, and more,” Lyft said.

Uber said it was changing its per-minute, per-mile and minimum fare rates to make rates comparable to what they were in September “while giving drivers more control over how they earn by allowing them to build a model that fits their schedule best.”

In acknowledgment of drivers’ critical role, both Lyft and Uber say they want to give them a share of their IPO riches. But Lyft’s plan to give $1,000 bonuses to drivers who have given at least 10,000 rides and $10,000 to those with 20,000 rides will help only a small fraction of drivers. Those drivers can choose to spend that money on Lyft shares at the IPO opening price. Uber has not said how it might structure drivers’ participation.

Adding to the financial pressure on Uber and Lyft, regulatory changes could dramatically increase their expenses.

California is now wrestling with how to move forward after a groundbreaking state Supreme Court decision made it harder for companies to claim that workers are independent contractors.

If that Dynamex decision gets codified with a potential bill now pending in Sacramento, Lyft and Uber drivers could become employees entitled to minimum wage, overtime and benefits like workers’ comp. The companies, which say they value the flexibility of independent contractors, are negotiating to provide some benefits but keep the drivers’ gig-worker status. That route would also cost them more money, however.

Many drivers at the protest said they didn’t care if they were employees or not. What’s important to them, they said, are four things: earning decent wages, having transparency about how rates are calculated, having protections like workers’ compensation and having a voice in corporate policies that affect them.

“Lyft is deceptive for drivers; we have no employee rights,” said Lauren Swiger of Oakland, who was wearing a skirt and top in Lyft’s signature hot-pink color. “The algorithm is so complicated, it’s impossible to figure out what we’re earning.”

That black box of code that determines both driver pay and working conditions, such as how many rides they get, is a sore point for many drivers.

Valentina Tulau of San Francisco said she’d visited the Lyft driver support hub with her earnings statements to try to understand the fluctuating pay rates. “Nobody there could tell me how they calculate it,” she said.

Since she lacks workers’ compensation, she’s stopped helping riders with their luggage, in fear that she’d throw out her back, she said.

Another issue: “Lyft doesn’t cap drivers,” she said. “There are too many, so drivers barely get enough riders and can’t reach the bonus” threshold. Both Lyft and Uber pay extra for reaching a certain quota of rides at specified times.

That concern, too, was shared by some analysts. The ride-hailing companies provide “far more capacity than could be economically justified,” wrote Hubert Horan, a transportation industry expert and consultant.

Carolyn Said is a San Francisco Chronicle staff writer. Email: csaid@sfchronicle.com Twitter: @csaid