69mach1377

Well I checked both this morning and the right front was a little loose. So I tightened it up a few degrees and went for a ride.
Vibes were gone in the 60-70 mph range where they were the worst before. Slight vibes above 70 and gone above 80. At ~120, spidy senses for cops overtook my ability to sense wheel vibes.
Thanks for tips. Not sure if where I'm at now is good enough for the future.

Chris Kennedy

That's great! Remember that with these racks we are dealing with re-engineering, so there are going to be issues like this. I think what it shows is that we have to pay a lot more attention to basic front end balance items (tires etc), and that all looseness has to be adjusted out of the bearings without over tightening. The 60 to 70 range was the worst on my car as well. The manufacturers of these racks should put out more information on these sorts of problems, as I'm sure we are not the first to have experienced them. I have written TCP on this, we'll see if they respond.
I have probably put about 200 miles on the car since this was done, and all is well---there's a slight bit at just under 60 on especially bad stretches of road, but it's only a bit and not worth fussing over. I know what you mean about good enough---I call things like this "being in an o.k. range": not perfect, but not so bad to be concerned about.

/s/ Chris

Old Mustanger

If the problems reoccur, you should check/verify your steering geometry. When sitting on level ground with your weight in the front seat, your tie rods should be level to ground. If they are not, you will get really odd geometry changes at odd speeds and surfaces.

Bump steer kits are usually used to correct these issues.

kenash

Hi,
File this in your "possibility folders"..... For years, I had a slight vibration in the front end. A couple of years ago, I added the TCP manual rack along with their complete front suspension system (regular not coil over). I had a "hot rod" garage due the front alignment so they were experienced with our archaic adjustments. Well, I still had that vibration/ shimmy thing going on. So, I talked the alignment guy and he suggested I have what's called a "road force balance" performed on the wheels and tires. (Google for details). Well, low and behold, my vibration I had lived with for 15 years was gone!
It seems, when I added the rally style wheels, one of them was out of balance, although it was compensated with adding weights, the regular balancing system didn't really rule out the imbalance. With "RFB", the tire is rotated on the rim, to further balance the assy, then, weights are added for fine tuning. When doing the "RFB", a value is given relative to the degree of out-of-balance. The lower the value to the better the balance. They shoot for under 15-20, as I recall. My one offending tire wheel was mid 30s. I had a brand new tire whose value was way over the specs. That's a factory tolerance gone bad. I found not all shops have the equipment for doing a "RFB", so call ahead. I found a near by "Goodyear" dealer who did mine, after calling several others.
Anyway, wanted to offer this.

Chris Kennedy

Thanks, everyone---It's been awhile since I posted this topic and I have some new developments. To make a long story short, I think what I was experiencing was something called "road vibration" (actually, "vibration" is a bad word, as it implies something that is steady, which this isn't/wasn't). It's not wheel or tire related at all, but when you have an extremely simple and precise rack and pinion, especially a manual unit, you can get feedback through the steering wheel on certain surfaces--little "kickpack" pushes, not imbalance shimmying. Something which amplifies this in the TCP unit is that it uses a straight cut rack. While that contributes strength, it means that you don't get a little of the slippage that cuts down on the vibration. Think of manual transmissions which use straighter cut gears as opposed to those cut at angles---straighter cuts give strength but are rougher. Same basic thing here. If you have a power rack and pinion, this probably would cut down on some of the road vibration. Interestingly, I read a little about this in Autoweek magazine. Apparently, Porsche recently redesigned its steering in the 911-933 series to cut down on road vibration. Many of the testers said this made the steering wheel more settled, but you lose precision. Anyhow, the unit my car has many more miles now, and with just a little bit of wear and work on adjusting tire pressures slightly, it's a whole lot less than it once was. Still, I think TCP should do a little more development work here. Anyhow, that's what I am now sure was going on----perhaps there was a little imbalance, but I took care of that awhile ago. Again, my experience indicates that you have to DRIVE these cars. Not just restore things and add hot shot updates. You'll never get everything dialed in unless you drive the car in the real world!

Cheers,

/s/ Chris