ᐅ Is the driveway to the garage too steep?

Created on: 19 Oct 2012 19:12
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VanTide
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VanTide
19 Oct 2012 19:12
Hello everyone, we received the plans from the architect today, and the driveway to the garage is supposed to have a 12-degree slope. Do you think my cars (new 5-series and 3-series BMW) will bottom out on it? Up to what slope angle can you comfortably drive over? Are there ways to reduce the steepness? The driveway is about 5m (16 feet) long and 70cm (28 inches) at its highest point. Thanks in advance.
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Häuslebauer40
20 Oct 2012 01:04
You’d probably be better off asking that question in a car forum.
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TomTom1
23 Oct 2012 15:39
Hello!

I'm not a technician, but:

The height difference will be about 5 meters (16 feet) 60 cm (24 inches), otherwise the slope would be 14%. With a consistent gradient, it is 12 cm (5 inches) per meter. Assuming an axle distance of at least 2.50 meters (8 feet 2 inches), the height difference would already be 30 cm (12 inches). Unless I’m making a calculation error here, only a Jeep could manage that.

Best regards,
TomTom1
Musketier23 Oct 2012 16:26
@Tomtom

You are talking about slope in %, while VanTide refers to degrees.

However, VanTide’s degrees are not correct. Depending on whether the 5 m (16 feet) represent the inclined driveway or the length shown on the plan, you would apply either sine or tangent, resulting in just above or below 8 degrees.

There is also a mistake in your calculation. The 30 cm (12 inches) or 35 cm (14 inches) between the wheels should be halved, as the greatest height difference occurs exactly 1.25 m (4 feet) behind the front wheels and 1.25 m (4 feet) in front of the rear wheels. But the issue can occur not only at the top but also at the bottom of the driveway. With a long front overhang and a low front spoiler, the car can scrape there as well.

When braking downhill, the vehicle also tilts forward slightly. You should not only consider the car’s “empty state” but also keep in mind that it might be fully loaded, for example, after returning from a holiday.
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VanTide
23 Oct 2012 17:06
The question is how do I get this issue under control? Do you have any ideas? Are there any tips or tricks for the driveway?
Musketier23 Oct 2012 17:25
1. First, determine the actual slope or angle of the driveway. Your information is contradictory. Only then can you calculate properly.

2. Fully load the car, including passengers, and take measurements of the clearances.

3. Bring a tape measure and visit several underground garages in the near future. If you find one with a slope similar to yours, you can test it with your car.

4. If the driveway doesn’t have a sharp angle at the top and bottom but rather smooth transitions with a steeper middle section, this might provide a few centimeters of extra clearance. Whether this is possible over a length of 5 meters (16 feet) is hard to say.