Still vibration in steering after front end mostly new (video)

[Redsquall]

This has been a problem since I got the car almost 2 years ago. Around 65 mph, the steering wheel and column as a rhythmic vibration like a fast Ratatat tat. I've got new tires all the way around, new steering column, the new aluminum arms, new eibach suspension, tie rod ends are not new but have no play in them. The only play seems to be inside of the steering rack. The last steering rack was exactly the same. I replaced it to get rid of this problem. I did replace the steering column and ujoints with a borgesen setup- that got rid of a tiny amount of play. Here is a video so you can hear the sound. The steering wheel is knocking with the sound. Rotors are new, brakes of been upgraded to the European power break it. The only thing I can think of is the rims– they have some scrapes around the edges. Could that be putting it out of balance enough to cause this? Or could the front tires be out of round? I suppose I could try to swap tires next time I have it in at DMC. By the way, DMC also took a look at the Front end and found nothing loose or needing replacement. Thanks

http://youtu.be/VgeLfCrrMls

[Jonathan]

I had what I would have referred to as a bit of a speed wobble around that same 65 mph or so up until this season. It didn't have quite the same rhythmic quality to it as yours though. I couldn't find anything with the suspension or brakes or steering that was obviously out of sorts. Over the winter (last year), I took all four wheels off the car and into a tire shop and had them rebalance them. It made a huge difference for me and the speed wobble was all but gone. I don't recall the amounts needed to get them balanced again, but a couple of the wheels were a ways off according to the shop. I mention this as a suggestion because it could be this simple for you and it is not very expensive to get this done. As a set of four, I think it was not even $50. Just an idea if you continue to be miffed by what's causing it.

[mark w]

My old car had play in the column that drove me nuts. I drilled and tapped the inner shaft and put a bolt thru it and the outer part to lock them together. solved.

[DMCMW Dave]

Get the tires balanced, and also check for out-of-round by lifting each tire slightly off the ground and spinning it. Also look for bends in the wheel rim edge. Out of round is pretty common on cheap (Cooper Cobra, Chinese tires etc.). I find that out of balance shows up at higher speeds, where out of round shows up at lower speeds.

If you have some time and a close DeLorean friend, trade tires for a short drive. I've done this on shop cars to prove out such problems.

There is an interesting issue you see on DeLoreans that is unusual on other cars. Since the front and rear tires are different diameter, they rotate at different speeds. So if you get more than one tire out of balance, they will alternate being in-phase and out-of-phase with each other. When in in phase the out of balance vibration adds up, when out of phase they can actually cancel each other out. This can cause a rhythmic vibration that you feel in the car as you drive. For some reason it's most notable at 60 MPH or so as a vibration that comes and goes about once per second.

I'm sure there is an engineer out there (hi Jonathan) with some time on his hands who can calculate the difference in rotational speed between front and rear tires at various speeds, and therefore the resultant frequency of the tire balance going in and out of phase. I feel too lazy tonight.

[Redsquall]

My old car had play in the column that drove me nuts. I drilled and tapped the inner shaft and put a bolt thru it and the outer part to lock them together. solved.

Mark, would you mind taking a photo for me? I'd love to solve that. I suppose this means you cannot adjust your steering wheel distance after? Thank you

[NckT]

Time to do some diagnostics and stop randomly swapping parts.

As noted in others posts, it'd be worthwhile getting the tyres rebalanced at a tyre shop, but ask them to measure the aluminium rim's runout both side to side and laterally. You can effectively balance an 'egg' shaped wheel bit you'll still have a harmonic oscillation at speed etc.
I'll assume that the tyres are decent brand, don't have radial force variation, that the tyre balancer is calibrated and the mounting method produced consistent repeatable results and not just the weights banged on and then just fitted to the car without a remount check spin. You could negate all this by finding a tyre entre that has a hunter road force balancer system, but this would be no good if someone had added that awful slime stuff that's supposed to automatically fill in punctures or slow leaks. .

One thing you haven't mentioned is that when you installed the new brakes and disks, did you measure the wheel hub bearing for play and for run out? Did you clean the wheel hub prior to fitting the disks (rotors???), bolt the disc in place and check for max disk runout? Depending on the breaking miles done, you may not exhibit disk thickness variation "DTV" (aka warping of the disk) as yet.

If you put a balanced straight wheel on an out of true hub you will still get an imbalance due to the precession of the wheel.

I'll assume that the geometry (tracking) of the car is correct and set to the service recall of frame height to floor set etc

Good luck, I hope it's something simple like tyre pressures being incorrect, play in the steering rack firewall bush, loose column bolts.

[Andrew]

How old are your front tires and has the car sat for any extended periods? You also may want to consider installing a vibration reducing U-joint. I have made the upgrade on both of my DeLoreans and I can certainly say that it totally changes the driving experience for the better

[dmruschell]

I have tires I know to be out of round on some of my classic cars (poorly made wide white wall radials) and the sidewalks are wide enough that it didn't matter and the car(s) drive smoothly.

I had a similar vibration on my DeLoreans, both with good, balanced tires, rebuilt front suspensions, and tight steering racks. Both cars were properly aligned.

I installed DPI's LCA supports and the vibration in my car is virtually gone (I haven't test driven my wife'sat highway speeds yet).

[DMC-Ron]

How old are your front tires and has the car sat for any extended periods? You also may want to consider installing a vibration reducing U-joint. I have made the upgrade on both of my DeLoreans and I can certainly say that it totally changes the driving experience for the better

Andrew,
Could you elaborate on the vibration reducing U-joint? Was this thru a vendor?

Thanks,
Ron

[BABIS]

Andrew,
Could you elaborate on the vibration reducing U-joint? Was this thru a vendor?

Thanks,
Ron

https://www.pjgrady.com/product/stee...pper-u-joints/