Ford's Explorer SUV has posted big sales numbers in the U.S. recently. But U.S. sales growth could be peaking, and that's one factor that could hurt Ford's share price. Source: Ford Motor Co.

Is Ford (NYSE:F) stock headed for a fall?

Ford's stock has had a terrific run since the dark days of early 2009, when it was trading for less than $2 a share. 

But every run comes to an end, sooner or later. Or put another way, every company faces risks that could knock its business off course. 

To be clear, I'm not saying that it's time to sell your Ford shares right now. (I own Ford stock and I have no plans to sell. If and when that changes, I'll tell you.) 

But if you're a Ford investor, or someone whose business depends on the company, it's worth keeping a close eye on the things that are most likely to hurt the company's bottom line -- and its share price. Here are three big ones.

Risk one: Are we reaching Peak Auto?

Rising U.S. auto sales have helped drive big gains for Ford's profits (and its stock price) over the last few years. In fact, Ford's strong profits in the U.S. have helped carry the company while it restructures in Europe and invests in an aggressive expansion in Asia.

But how much more growth is there to be had? Consider this chart, which shows U.S. sales of "light vehicles" -- cars, pickups, and SUVs -- over the last decade.

Source: Automotive News (historical figures), Edmunds (2014 estimate).

As you can see, the economic crisis clobbered new-vehicle sales. We've since had a nice recovery, and the growth is continuing. Edmunds estimates that U.S. light-vehicle sales will total about 16.4 million this year. 

But that's not far from the peak of 16.99 million that we saw in 2005. How much growth is left? 

It's not (yet) clear that the U.S. market is peaking. But recently we've seen some signs that it might be. After growing over 13% in 2012, and another 8% in 2013, the U.S. light-vehicle market is up just 5% this year through July. 

Meanwhile, automakers' incentives are rising, and analysts have expressed concern about the increasing average length of new-vehicle loans (72 months has become very common).

If history is any guide, slowing growth in the U.S. vehicle market will lead automakers to boost incentives -- using discounts to get the biggest possible share of customers who are willing to buy. If and when that happens, Ford will have a tough choice: increase incentives or risk losing sales.

Either way, its bottom line -- and its share price -- will take a hit.

Risk two: The all-new 2015 F-150

Here's a chart that shows just how much of Ford's profits came from its North America business unit last quarter.

Source: Ford Motor Company.

The details differ from quarter to quarter, but the proportions have been pretty much the same for a few years now: Most of Ford's profits are coming from North America.

I don't have a chart that shows how much profit each of Ford's products is generating, because Ford keeps that information secret. But it's no secret that a big chunk of Ford's profits in North America come from the F-Series pickup line, the hot-selling F-150 and its Super Duty siblings.

The F-Series is America's best-selling vehicle, and it's Ford's most profitable product. That makes the all-new 2015 F-150 a very important new product for the Ford Motor Company. 

But Ford is making a big gamble: The new F-150 features aluminum body panels, a first for a full-size American pickup. The new F-150 will weigh much less than the current trucks; the weight savings is expected to bring significant gains in fuel economy.

The all-new 2015 Ford F-150, shown in top-of-the-line Platinum trim. The 2015 F-150 Platinum will start at $50,960. Source: Ford Motor Company.

That raises two concerns for Ford investors: Will buyers accept the new aluminum F-150? And will Ford be able to build it as profitably as its current trucks?

The first concern is probably not something to worry much about. Some buyers might wait a bit to see how the new trucks are received, but Ford has clearly done its homework around this product. I've talked to several senior Ford executives about the new F-150, including CEO Mark Fields and North America chief Joe Hinrichs, and I can tell you that they are all very confident that customers will like the new F-150.

They think they've got a winning product -- and given Ford's longtime success in the pickup market, I think they deserve the benefit of the doubt.

But will the new trucks be as profitable as the outgoing models? Pound for pound, aluminum is a lot more expensive than steel, and making aluminum-bodied vehicles requires Ford's two truck factories to adopt different processes and tooling. 

There's a good chance, in other words, that these new trucks will cost more to make. But -- at least on the lower trim lines that account for the majority of F-150 sales -- Ford's price increases have been very modest. Will Ford make less money per truck on the new F-150?

We'll see. It's possible that Ford will make up the difference with greater sales of higher-profit premium models, like the Platinum edition shown in the photo above. It's also possible that Ford will boost prices across the board once the new truck is established in the market. 

But it's also possible that Ford's profit margins in North America will get squeezed a bit, at least for a while, and that could hurt the stock price. 

Risk three: Disruption overseas

A big part of the bullish case for Ford stock rests on its overseas efforts -- specifically, on its aggressive restructuring in money-losing Europe, and its ambitious expansion in Asia.

Ford Europe lost $1.75 billion in 2012 and another $1.6 billion in 2013. Ford has warned that it will post another loss in Europe in 2014. But that loss is expected to be smaller than last year's, and Ford expects to turn a profit in Europe in 2015.

Here's the story in a nutshell: Deep recessions in many parts of Europe have clobbered new-car sales. But Ford launched a major restructuring effort in the fall of 2012, one that is very closely modeled on the "One Ford" strategy that has been so successful in North America.

If it works -- and right now, signs are that it's working well -- that will mean a significant gain for Ford's bottom line. (If Europe had broken even last year, it would have increased Ford's global pretax profit by almost 19%.)

Meanwhile, Ford's Asia-Pacific region isn't generating huge profits right now, but that's because a lot of its earnings are being reinvested in an aggressive growth plan. Right now, Ford has five factories under construction in China and India, the last phase of an expansion that is expected to cost nearly $5 billion when all is said and done.

Ford launched the Mondeo in China last year. The Mondeo is a locally made version of the midsize Fusion sedan. Sales have been brisk. Source: Ford Motor Company.

Ford's sales in China have been booming: They rose 35% in the first half of 2014, far outpacing the overall market's growth. Chinese consumers clearly like Ford's current product formula, and all signs are that Ford will be able to keep those new factories very busy for some time.

So what's the risk here? The risk is this: that one (or both) of these efforts doesn't generate the profits we expect.

To some extent, success in Europe and Asia is already baked into Ford's stock price. That's because Ford's management has shown that they can execute well and because all signs so far have suggested that both efforts are solidly on track.

But both face external risks, starting with political and economic risks in both China and Europe. If either effort goes off course, Ford's stock price will suffer.