No worries... My MINI does this too and I haven't even lowered it yet...

 

Dortoh; did you ever get the coilovers installed?

 

I am not sure if it weird or expected that it happens at a specific RPM range not car speed.

It would seem that if it is a normal vibration issue then it would be caused by an out of balance rotating part and the vibration would be related to the speed of rotation for the piece that is out of balance. If it is the CV that is causing the vibraion and it is out of balance then the vibration would be speed related...However, you say this is not the case...courious.

The RPM range that you give is roughly the range of peak torque for the engine. Plus you say that it is easier to make it happen going uphill than down - again, a relationship to torque. I assume that when you say "I can easily reproduce the issue under any load, any gear, at almost any speed provided I get the RPM range..." that you mean that you can reproduce it at WOT or something close to that, not just a light application of throttle. But if it is related to torque on the piece causing vibration and that piece is downstream of the transmission, then it should be more pronounced in 1st gear then 5th. But you have not said that it worse in first than fifth - again I assume the absence of that clarification means that is not the case.

All of the above would say that it is not the CV as that would either be speed or gear realated. This would also indicate that it is something happening up stream of the transmission.

The problem is that I don't know where this leads to because you also say that you didn't notice anything before you lowered the car. Could it be something like a broken or damaged engine mount? or dampener? That, when there is a load on the engine it causes the engine to contact something? That would be something that would be purely engine speed or torque related. However, I am not sure how that would be affected by lowering the car. At this point I am really guessing. But from what you have said it seem that you may want to expand the range of your search.

 

TEST: Large parking lot. From a stop, accelerate in a big circle just as you would when the vibration happens. Never let your steering wheel be straight.
report on the findings.

TEST: Accelerate in a straight line, get it vibrating, enter a turn. Does it continue while you are turning? Or stop while in the turn and begin again as you reach center steering again.

TEST: Stick in some old fashion spring rubbers to jack it temporarily back to stock height.

 

I have to agree with Rally Stance and look at the installation.

I posted on a different tread last year of the exact same problem when everyone started bashing Adam at Alta for selling bad H&R springs to them.
Alta hadn't had any issues with cars they installed them on.

I still believe that it comes down to the tech doing the install.
What I think's happening is this.
Once the strut assembly is removed and the tech is left with the heavy wheel carrier with is's rotor, caliper and axle still attached and its pivoting on the lower ball joint, he just lets the whole assembly "fall over" since he didn't have some bungy cords or something to tie it in it's normal position. So with that "falling over" you are now trying to pull the inner and outer CVJ apart. It has all the weight of the assembly and leverage with it pivoting on the balljoint.
The CVJs are designed to move up and down and turn with the wheels. What they are not made to do is let a lot of weight pull on the whole axle from the side which is what happens when the tech just lets the assembly hang while he gets the new strut ready. Something in the CVJ is getting pulled "out of it's groove" or just pulling it past it's intended bearing race.

I know some are going to say that they had their car worked on at a good shop but I can tell you first hand, I work for a LARGE Porsche dealership and with 18 techs, you get 18 different ways of doing something. Some take their time and follow the manual to a T and some just use hammers to fix everything if you know what I mean.

I did my own springs last year and was very careful on supporting my wheel carrier when it was loose as well as making sure I never pulled on it when trying to get the new strut put back in.

I then installed my Bilstein HD's a few months ago and took the same care with the axles. I have never had any vibration at all.

I just don't believe the axle angle being the problem with just a 1-3" lowering. Think about it, if you loading the car with 2 LARGE adults in the front seat and then loaded the car down to its weight limit, do you not think the car would be sitting 1-2" lower then. We aren't hearing any complaints about a vibration on loaded down cars now are we.

 

This is an interesting thought that pushing or letting the front end drop after releasing the shock from the steering knuckle could damage the CV. I recently changed my camber plates following some NAM DIY instructions. For the R56 they said the knuckle would just come off without compressing the spring. This didn't happen for me and I compressed the spring. I looked at forcing the knuckle down but did like the way it felt. I found out afterwards that is the way some people do it. Maybe this really isn't such a good idea and I am glad I didn't. While I would believe that isn't a problem for the wheel end as that needs to go through the full range of steering motion, it could very well be a problem for the transmission end which could be much more limited range of motion than the other end. Could it be that some race or retainer has been damaged?

 

Eddie 07s

Not sure how the CVJ is set up in a Mini, but I know first hand from my Honda Prelude back in the 90's that when I pushed down to hard on the lower control are to get enough room to pull the strut out that I did stretch the axle to far. We got the car back together and went and drove it and i made bad cruntching noises. I worked next to a Midias at the time and the guys said on that car you have to take the axle nut off the hub so that the axle would slide in the hub and not streatch it like I did. Needless to say I had to buy a new axle to fix what i screwed up. Just makes me think about this whole problem people are having with their Minis and makes me be very careful with axle joints like these.

 

Without some testing on some cars with the symptom, we are all stabbing in the dark.

I verified at stock height, the axle is at a small angle down. As my big fat head won't fit under the car, I am guessing about 3/4 of an inch or more. I would have to build some blocks to sit on to measure for real.

Running any CV or U-joint too close to dead straight will allow natural resonances to be excited because they are not forced into non-constant velocity that prevents building a resonance. Yes Virginia, CV joints are NOT constant velocity. This has been well understood for probably 100 years. Many axles have big rubber harmonic dampers on them because of this.

I sure as heck let my spindles drop. Actually had to stomp on them to get the shock out even with the spring compressed a bit. No vibration, but stock height.

No one seems willing to do a few simple tests. We are not going to get very far folks! I tried to get some stats together on drop and camber. Again only a few folks replied. I don't have the symptom so I can't do any tests. No one will either confirm or eliminate any of these theories without doing some tests and offering some stats to try and frame the problem. "must be the installer" is not applying any rational analysis. It may be correct, but this is not how we get there.

Can't say on a Prelude, but on the DC5 chassis the axle will just pop out of the inner spline. You just pop it back in. No damage. Just like a new install. It is the inner spline that has the travel. It does not "stretch" it slides in and out. That is how it works. I have a hard time believing you actually damaged the axle. They are really tough devices.

 

Mine shakes in 1st gear from a slow acceleration. Yes I've had it aligned. Seems to be getting better... or I'm just getting used to it 15k miles later. *shrugs*

 

Lil
OK
How much is it dropped, what is your camber setting?
Have you tried the tests I mentioned above.

 

What I can tell you right now is I don't have a clue how much it's dropped. It's been to long since I've had it stock. I do have a buddy with an R56 I can see how much it is compared to him. I am on a 40 series tires as opposed to a 45, so I'll have to calculate that difference.

I had a paper somewhere around here with exactly what they set the alignment at down to the thousandth of a degree, but I know it was a .5_ on both fronts, and a .75 in rear. Though I've questioned that cause the front looks almost straight up and down, and the rear has some noticeable camber to it. Either way, they told me it was set "within factory specs".

I'll take some pics, and see what I can do about getting it on the lift today or tomorrow for more pics and measurements.

 

I got the car back from the dealer yesterday and yeah I would have posted earlier but I have parental duties so sorry. The dealer agreed to look into my vibration issues despite having aftermarket parts on the car, and after researching said that the "CV axle angles are offset and are causing vibration. Must return to tolerances." I asked them to track down the lowering tolerances of my Mini (R56) because their JCW kit drops a car and figured I could still get good looks and be within specs.

The tolerances FROM THE DEALER on an R56 in terms of lowering are as follows (in cm):
Front: 587.99 +/- 9.98
Rear: 571.98 +/- 9.98

My drop on the front is 558.8cm which means I'm out of tolerance by 29.19 which is over 1.149 inches (for us not on the metric system)! So my installer dropped it too far causing the issue, and even though they did raise it they didn't raise it enough. This definitely gives my installer more accurate specs to work with in terms of getting the car to perform within factory specs, so now it's a trip back to them to put the car back in tolerances and see if it eliminates the issue.

FYI I'm attaching a pic that I got from the dealer regarding specs and how to measure.
http://picasaweb.google.com/lh/photo...eat=directlink

 

I'm apparently 5.4" out of "spec"....

I'm at 448.81 up front

 

Odd they would give a spec to a trim piece on the body whose position is not well fixed, and not specify an exact tire and inflation. So, their spec is not reliable.

I do not buy the dealer saying the CV is at too great of an angle. Not enough if anything. But to just say "out of spec" is exactly what I would expect the dealer to say. We are modifying the car. They are not responsible, or likely to be knowledgeable.

Again. I have asked for everyone to pony up with their specs and do a few simple tests. All that seems to go on is more complaining. Can't crack it that way. Best of luck. I have offered what advice I have using a rational method for problem identification. Listed as many possibility as we can think of, considered what I know about sympathetic harmonic in transmission systems, and offered some suggestions for testing. I am done.

 

Inflation of the tire would have zero effect on this measurement. Look at the picture again. They are measuring from the bottom of the wheel and have purposely done so rather than measuring from the arch to the ground to avoid issues with tire circumference and inflation discrepancies.

And MINI has taken into account wheel diameter differences and you'll find that when they list tolerances they do so for 15-18" wheels with different values for each since the wheel diameter has an obvious effect on this measurement.

 

I'm with ya man, but things like this are just subject to the requirements of the military for me for at least another month. I plan on doing this as soon as I get next to my car again!

 

I have been on vacation and just got caught up on this thread. I did install the front coilovers but had some clearance issues, so I had to put the factory units back on for now. While doing the install I learned a few things.

1. I removed one of the nuts that hold the CV shaft in the hub to check the end play. There is a ton of free play so I seriously doubt that the shaft could ever be "too long" to cause an issue on a MINI that has not been crashed.
2. I checked the shaft angle and as tvrgeek mentioned, at stock height the shafts do have a slight down angle. So some cars when lowered could be getting the shafts very close to straight.
3. My car does have a vibration dampers on the shafts. Could some installers be arbitrarily removing them?

I won't be able to add any more info until the final install which will be a few weeks.

As for the install damage theory this is a remote possibility. As mentioned they are really tough devices, but if mis-handled the few delicate internal parts could be damaged. Just like a ball bearing, if installed properly it's very durable but if installed improperly they can be damaged. Again I think this is an unlikely theory.

Some data that may be easy to compile and may yield some info would be:

• How many miles were on your car when the car was lowered.
• Do you or do you not suffer from the vibration issue?
• Approximately how much did you lower your car? (optional)

Devices such as CV shafts get 'accustomed' to operating in their usual range. If after the device has become accustomed to operating in said range it is asked to operate in a different range (which we ask it to do when we lower our cars) The device will many times complain (the vibration). If we compile enough data it may show that the cars that vibrate had several miles on them when the change occurred. One way to disprove this theory would be if someone with the problem would install new CV shafts. (Any Guinea pigs out there?)


No Remorse,
FWIW, the dealer told you exactly what I expected they would, can't say I buy it.

 

Quite right on the wheel bottom, but still to a trim piece whose position I would not trust.

 

I talked to a couple friends today about power transmission. They both jumped right on the "straight shaft" issue. One used to teach automotive technology, the other a aircraft mechanic. Did you know in an old Buick they actually bent the drive shaft to keep it from vibrating? As I thought I had remembered, this is not a new or mysterious problem.

Now on to a solution. The only thing I can think of is to work with a dampening doughnut, position, mass, etc. Something to lower the Q and or shift the frequency out of range.

 

If that's the problem, the solution is simple. Lower your car more.

Cures the aesthetic issues of wheelgap and SUV ground clearance too

 

If it were that easy. I prefer to actually use the expensive shocks I put in, rather than the bump stops! I have to clear my driveway apron, speed bumps, and the security hardware where I work. Stock is fine, lower by an inch would be cool. More than that, even if I redesigned the travel just would not work. I have driven cars too low. STOCK 74 Pinto was only 3 1/2 inches off the ground. My TVR only had about 4 under the exhaust. No thanks. Street use needs a clean clear 6 at least. Now, if someone would produce some replacement wheel arches that covered 8 inch rims and reduced the gap, THAT would spark my interest. Then only the tail end would look jacked up, and if that is all you see, then you are eating my dust already. Function, then form. I am way too old for the other way around. But you are technically correct if we have analyzed the problem correctly.

 

Sounds like your expensive shocks are built too long and without enough stroke.

I'll still never understand why koni and bilstein decided to keep the stock travel specs and strut length even though they recommend their use with lowering springs

So another easy option would be engine mount spacers to raise the engine and tranny a bit. That's the common solution for VW's that have axle angle issues due to lowering. I plan to have some made to correct my axle angles a bit and get my oil pan up off the ground.

 

Doesn't that defeat the purpose of lowering the car? Lower the car is intended mostly to lower the CG. Raising the engine, being the heaviest part in the car, will take a good part of that way. So are there other advantages to lowering a car other than changing the CG?

Also, while the straight-line shaft issue seems to make sense, it doesn't answer some questions. In particular - why do some cars have a problem and not others? Also, why is it just a problem with a lot of throttle and not coasting?

If it is an engine load related issue then it seems that a way to test this out is to take the car to a dyno and run it at the lowered height and then run it with it jacked up to factory height. It just costs a little bit of money

 

"I'll still never understand why koni and bilstein decided to keep the stock travel specs and strut length even though they recommend their use with lowering springs "

So they can charge more for lowered ones? Actually, the HD and FSD are sold specifically as OEM replacement. Koni yellow's are sold specifically for lowered cars. Both companies are trying to lead you to their coilover. Believe it or not, not every one wants their car lowered.

Raising the engine to add angle may work, but it could throw off all sorts of other things. Lower CG is only one reason to lower a car. The change in roll axis with the change in geometry is just as important.

Anyone with the vibration, coilovers and a quiet back road could do the height comparison. No dyno needed.

With the assumption straight shaft is the problem:
Why under load? Something has to excite the resonance. This is a sympathetic harmonic problem. When the engine/tranny is under load, it provides enough vibration to get it going.

Why some cars? A few guesses. Amount of tolerance in the joints, sensitivity of the driver, and possibly the amount of camber.

 

There are numerous reasons one would lower a car. Yes, this would raise the CG a little bit.

Other Advantages of lowering car:

Aesthetics
Better roll center (assuming other geometry changes are made)
Aerodynamics