Eliminating Car Shake

[AirmanPika]

OK so I know my car still shakes a bit at speeds above 45mph. I've replaced the suspension, steering rack, bushings, ball joints, and all tires are new and balanced. What else could cause the car to shake? Right now I'm thinking wheel bearings are the likely culprit and need replaced but is there anything else that could do it? Its not severe shaking but its something I want gone. I guess it could also be that the car just sits a lot so the tires could be slightly out of balance from shape and settling. My BMW did that for a few days when I first started driving it again.

[Ron]

Shakes around 45 mph are usually a tire out of balance.
Maybe, take it somewhere local that can spin balance tires on the car (covers weight problems with tire, wheel, and rotor...)

Does it shake the steering wheel? If so, do the brakes affect the shake (rotor problem).

Not likely the wheel bearing...(Jack it up and see if there is slop vertically or horizontally)

If it has been sitting a long time, give it a few miles...

[knightjp]

You only need to worry about the tires if the car has been idling for more than two weeks. If this is a weekend driver, then I don't think it's ur tires.
Wheel bearings should give you a rough sound when the wheels are turning if they are worn. Usually no shaking unless the bearings are really bad.
You might want to consider that the axles might be slightly bent or something.


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[Ron]

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[Rich]

Ron has the right answers on this. Be sure the wheels are really balanced. Go back to your shop and tell them they need to do better. Or get it done again, and better, elsewhere.

If that doesn't solve the problem then consider going up a notch. This is about any car, not only D's:


In the last decade or so a next-level system has come on the market, one that addresses the issue of tire uniformity. A "balanced" wheel-tire can still be a problem, especially with some cheap tires.


....Road Force Measurement System to help detect potential tire uniformity causes of vibration that are not balance-related. This system utilizes a "road roller" which applies up to 1,400 pounds (635 kg) of force against the wheel and tire assembly to measure their combined uniformity. This simulated road force test helps verify if the assembly is "round" when rolling under load....

Link to RFM description here:
Tire Rack RFM page (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=40)

[DMCMW Dave]

Make sure the wheels are not bent. You can balance a bent wheel but it will still shake.

[AirmanPika]

Acually the car does sit sometimes for weeks at a time (well in this case months since its been in storage) so I'm curious how it will feel by the time I get back to VA. I want to say they did road force balancing when they installed the new tires at firestone, but I'll have to look again. Once I get the car back to VA, if its still shaky I'll get them rechecked. I also plan to do the axles at some point so this might be as good a time as any.

[stevedmc]

Shakes around 45 mph are usually a tire out of balance.
Maybe, take it somewhere local that can spin balance tires on the car (covers weight problems with tire, wheel, and rotor...)

Do you have a place up there that can balance tires while they are on the car? I spent a few days calling around Baton Rouge and couldn't find anyone to do the work. If there is a place in your area that does on vehicle balancing I'd love to get it done next time I'm at your house.

[Ron]

Acually the car does sit sometimes for weeks at a time (well in this case months since its been in storage) so I'm curious how it will feel by the time I get back to VA. Ah...I didn't know that was the case... sounds like you'll have an answer to that part shortly ;-)


Do you have a place up there that can balance tires while they are on the car? I spent a few days calling around Baton Rouge and couldn't find anyone to do the work. If there is a place in your area that does on vehicle balancing I'd love to get it done next time I'm at your house. There is one in Murphy, about an hour away...the owner is um...,...and old fart who hates mags and foreign cars. lol I think he would do it for us if we call in advance. I'll call him tomorrow.
Meanwhile you might ask around for a place that does on vehicle rotor turning, and dealerships...They are more likely to have the equipment. If all else fails, there is one ont the way up in Atlanta that the racers use...

(I know someone is going to ask, so- Removing rotors on some vehicles is A LOT easier than pulling them even if the vehicle is already in the shop, especially 4x4s.)

[AirmanPika]

Well most of the shake is gone now that the car made it to VA. There is still a slight shudder at 60+ tho that seems to be coming from the front. I can feel it in the steering wheel but not so much the rest of the car if I let go of the wheel (safely). Since the entire front suspension and steering has been replaced, I'd better have those wheels checked to make sure they aren't bent. A few years ago I hit a curb at a rather high speed with the left front wheel which could be the trouble maker. You tend to feel the shake more going downhill and turning right (especially doing both at the same time).

On a side note...my battery was fried. Yesterday I noticed it would die rather fast (within a day or so) and on the way to VA I had to get jumped on my last stop. When I got home I pulled the battery and it was piping hot and had even partially melted the cover. Its an Optima Yellow Top battery that I got before deploying in late 2010 and my family didn't do a great job driving the car around so the battery died quite a few times while I was gone. I had it swapped out under warranty and all is good again. Anyone else had issues with the Yellow Tops in a delorean or do you think it was just a symptom of bad battery maintenance? I am aware that yellow tops don't seem to be the same quality as they used to be. Hopefully they've fixed those issues in the last year and a half.

[Bitsyncmaster]

Better check your voltage with the engine running. It may be overcharging but most likely you got a shorted cell inside the battery. My Yellow top is going strong after 6 years.

[AirmanPika]

Better check your voltage with the engine running. It may be overcharging but most likely you got a shorted cell inside the battery. My Yellow top is going strong after 6 years.

OK I think it was just a bad battery. The car shows 14.35V at idle which as far as I know is fine.

[David T]

Have the battery load-tested and the alternator checked. Road Force Balancing is really only necessary on very low profile tires, not the ones we use on a Delorean. If you let the car it for long periods of time you will notice a vibration till you drive the "flat spot" out of the tires. On modern radial tires it should happen rather quickly especially if it is hot. If the car still shakes check the tire pressures, check for a bent rim or maybe there is something (dirt) between the wheel assembly and the hub making the wheel wobble, an out of balance tire or a defective tire. Separating belts can cause this. Run your hands over the sidewalls and feel for waves, ripples, bumps, etc.
David Teitelbaum