Almost all speedometers are "off", but usually only by between 5 -10 mph and always such that they read higher than actual. At what speed are you measuring being off by 15 mph?
Probably. But here's an even more interesting factoid: You can't drive your car without the ignition switch on... so who cares whether the brake lights work then?
thanks for the reponse. I plan on checking the speedo out by using a pace car with a known good speedo. As to the brake lights, every car I have ever had or seen, the brake and other lights in general always worked without the ignition being on. The lights have always been an indepentant system from the ignition, at least on US cars. If someone is on the side of the road or the ignition fails and you hit the brakes, they should work as well as the brake lights. It is a safety issue. I havn't checked it out yet, but this could mean that the em flashers will not work if the ignition is off. David
As the emergency flashers are independent of the ignition on my Z4, I'll bet they function the same way on your 7 - as well as on most other cars. (Although I just checked and they don't work without the ignition on my motorcycle.)
I'd say there's just as much chance of the brake light circuit failing as the ignition - more on a BMW where the stop light switch isn't that reliable.
Flashers working with the ignition off would be a pain too - all to easy to leave the car with the indicator switch to one side and come back to a flat battery. The hazards work without the ignition on, though, for obvious reasons.
You'd be better off using a GPS if you want to know the actual speed. If you're just trying to acertain that your speedo is "normal" than you can compare it as you say.
As to the brake lights, every car I
I don't get it. Yes, I've noticed that the brake lights worked without the key on some US made cars , but I fail to see how this is a "safety issue". To begin with, the ignition failing is a very rare occurrance. And if/when it does, it would be when you attempt to start the car, not while it is running down the road. In the rare circumstance that the ignition switch did fail while underway, your main problem would be lack of power assist to the brakes and steering, not whether the brake lights were coming on...
You will find the emergency flashers (aka hazards) work just fine with the key removed.
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