What are "ground straps" for?

[Ed_Flecko]

Ever since I was a kid, I've always wondered why some cars have "ground straps" and what their purpose is?

I also see people who do electrical upgrades and/or modifications to their vehicles that use ground straps.

Is adding a ground strap to the average vehicle a simple, cheap "upgrade" that's helpful (in some way)? If so, should it really be a strap or a cable (of some sort)?

Thank you,
Ed

 

[ragtoplvr]

First you need to clarify. There are ground straps that drag the ground to "bleed off charge" or "prevent radar from getting a lock".

These are as useful as Homeopathic medicine.

Then there are ground straps that keep all the parts of the car connected. These are essential, but a normal car will not need any more of them, as they are put in by the MFG. Occasionally they fail or get removed, and sometimes not enough are put in. There is a benefit to these. Electricity needs a low resistance return or it finds one. If that is in the radiator, then galvanic corrosion can occur. If it goes thru a bearing, then the bearing will fail.

Rod

Rod

 

[Kira]

Hello, Ground straps are frequently woven copper for flexibility in service as well as application (specific vehicle) coverage. Common wire can do the same job.

They're used to provide a circuit to ground from parts (engine, for example) which are rubber mounted. The rubber in an engine mount will not conduct electricity.
Engineers found that such a circuit (engine) could continue through the transmission to a solid ground is iffy at best.

Better to ground the engine directly.
You'll see straps on the heads to the firewall because the metal of the heads are where the spark current grounds and various sensors need a ground from the block to the firewall.
Head gaskets can and do insulate the heads from the block.

The exact same phenomenon (pipe dope or teflon tape at plumber's joints) is why system grounds go to a cold water inlet pipe. That pipe is directly in contact with the earth. Kira

 

[HerrStig]

Much of the exhaust on many cars floats above ground on rubber hangers and can act as an antenna for ignition and other noise. A strap from the tailpipe to the body can do wonders. Fuel trucks used to drag a length of chain to "bleed off static". Since it never really worked you don't see than practive any more. The net is loaded with info on radio noise reduction in vehicles. The fibreglass hoods on COrvetts used to (and may still) have a metal screen embedded in them connected to what ground there is an a fibreglass car. An aftermarket hood and "high oputput" ignition made even the FM radio worthless.

 

[Vern_in_IL]

Originally Posted By: ragtoplvr
First you need to clarify. There are ground straps that drag the ground to "bleed off charge" or "prevent radar from getting a lock".



On ambulances they have pneumatically operated tire chains that appear to be ground straps.

 

[Kestas]

Quite often, lack of a grounding strap from the engine will result in current flowing through the wheel bearing. This has been reported in many vehicles. Most famously, there was a recall on the first Omni/Horizons built in the late 70s. The grounding strap failed by corrosion, resulting in wheel bearings that failed with electrical damage. The fix was to place a triple grounding strap from the engine.

 

[HerrStig]

Bad ground connections on the engine have resulted in current flow through the speedo cable metal cover to the dash. Now most cars get their speed info from a wheel sensor rather than a fitting on the transmission. The cable cover could get so hot it locked the speedo drive shaft inside.

 

[HerrStig]

I remember when toll booths often had a flexible wire protruding from the pavement before the booth to drain off static from cars so the toll taker didn't get zapped on dry days. Tires with a lot of silica in them tend not to conduct static charge to the pavement the way tires with plenty of carbon black can. I one saw a wheeled crane contact a high voltage line at a construction site. The operator carefully jumped to the ground when he saw the tires begin to smoke.

 

[Chris142]

Originally Posted By: HerrStig
Much of the exhaust on many cars floats above ground on rubber hangers and can act as an antenna for ignition and other noise. A strap from the tailpipe to the body can do wonders. Fuel trucks used to drag a length of chain to "bleed off static". Since it never really worked you don't see than practive any more. The net is loaded with info on radio noise reduction in vehicles. The fibreglass hoods on COrvetts used to (and may still) have a metal screen embedded in them connected to what ground there is an a fibreglass car. An aftermarket hood and "high oputput" ignition made even the FM radio worthless.
funny how you brought up fuel trucks.saw a chain dangling from a fuel truck on chips recently. The truck in duel had one visible in a few scenes.

 

[splinter]

Yup, ground straps and curb feelers.