Questions for the mechanically minded

[Wivvix]

Get Someone to have a closer look at the wheel bearings.
They need to be pulled out and cleaned and physically inspected

A roller that is starting to collapse can (Catch on the cage). If it is well greased there won't be any noise.
The failure wil only show when it has a load placed on it....eg-: the weight of the car.

I had VW super beetle that i threw a motza of money at but it came back the same shimmie....Till i did the bearings..

Just something else to have a look at...

Cheers mate, I've replaced the rear right but perhaps the rear left is worth looking at. They're only a hundred bucks or so for the whole kit. Probably worth doing when the rotors are off.

Well after another 6 hours at Veem with the commercial manager, aka "the engineer" John referred to (?!?), and a somewhat lighter wallet, I can safely say the car is driving better than ever. The shudder barely presents between 50 and 60kph, and isn't quite as harsh at high speed. It's definitely still there, absolutely no denying that, but nowhere near as bad pre or immediately-post driveshaft replacement.

There was however a balance issue with one of the universal joints, there was about 30 grams too much at one end of the driveshaft, which evidently was enough to really mess with things, which was picked up today upon re-checking balance done by the commerical manager. Go figure

The "commercial manager" seems to know a fair bit about cars, vibrations and mechanics. Exactly how much I really don't know, only that he rebuilt his holden commo engine due to a factory vibration issue, but yeh he seems to be experienced...? Irrespective, he's offered to take the car down to Veem when he gets back from holiday, and basically go over everything with a fine-toothed comb to see if he can pinpoint the source of vibration. At this point, driveshaft/tailshaft, half-shafts, diff flange and angles are apparently fine.

What felt like an "out-of-roundness" vibration before now feels more like something shaking, something loose which is clattering and reverberating through the whole body of the car. Possibly an engine mount, who knows.

What do you guys think? Should I hand the car over to this chap for a day or is it a waste of his and my time?

[Okibi]

I guess it depends on how much.

Perhaps if a hub or stub axel was damaged then your tyres would have worn out of round so the "problem" may be fixed but the damaged they caused still evident

[Wivvix]

I guess it depends on how much.

Perhaps if a hub or stub axel was damaged then your tyres would have worn out of round so the "problem" may be fixed but the damaged they caused still evident

Can you explain what a stub axel is?

Hub faces were checked for runout. 3 had less than 1thou runout, 1 had 4thou runout.

Veem checked basically everything bar the hubs and wheels. They put a dial gauge on everything else.

There's not going to be any cost involved for this work the commercial manager has offered to do. They're essentially offering to do it out of good faith and sympathy.

[Okibi]

If they're offering to do it out of good faith than I think you should go for it.

[Wivvix]

If they're offering to do it out of good faith than I think you should go for it.

They have offered to do it out of good faith, and I have gladly taken them up on the opportunity.


Having had more opportunity to drive the car, going for a nice trip from stirling to roleystone, I have refined my understanding of the vibration.

I believe the new driveshaft has removed itself as a reverberating/transmitting component in the system. As a result, I think it has clarified the type of vibration.

Think of the vibration like you do a sound wave. Naturally everything negative of 0 is sheer comfort and delight, however brief.

The vibration seems to come at almost regular intervals when cruising between 100-110kph, the vibration starting off shallow, increasing in harshness until a shake, and then dying off again. I refer to the vibration experienced at 100-110 because it is more pronounced than it is at 50-60kph, and therefore easier to analyse.

Gear, RPM and drive do not appear to affect it's presence. Coarsely finished roads have the effect of amplifying the severity of the vibration.

[Wivvix]

What you are describing is almost definitely out of round tyres, If your wheels are REALLY balanced and hub-centric its almost definitely an out of round tyre or wheel. Borrow your mates 91 wheels for an hour. If the vibration goes away tell them to change the tyres. No ifs no buts change them. You did say the vibration was coming from the rear & definitely not from the front

The other things that might cause REAR vibration is an out of balance propeller shaft, damaged drive shafts, wheel bearings or out of alignment hub carrier. I wont say chassis as this is not really likely at all.
Eliminate the wheels then tackle the bearings AFTER checking both hubs as Mokster said are running true. You said you changed the main shaft and UV joints yeah?

I still think its your tyres though as what you are describing with the wave analogy is a tyre problem, the reason i say this is because you are getting a harmonic vibration at speed and this is normally always caused by tyres

I'm thinking I may have to convince him to let me at least swap the rear wheels to check. Uni's were replaced yes.

Veem engineering had the MX5 yesterday all day. They foam-filled the driveshaft, and I can very comfortably say, there isn't the slightest vibration between 0 and 110kph. Between 110 and 125kph there is a fairly violent vibration, enough that it shook the car on the stands.

Veem put the car up on stands, and with the rear wheels ON, vibration 110-125kph. Rear wheels OFF, no vibration.
Veem also identified runout on the wheels. They said it's "probably within manufacturers specifications, but with possible tyre issues it could be enough to cause problems".

So what should I do now? Do I pursue tyres or wheels, or do I look at hubs etc? The wheels are supposedly brand new Enkei RPF-1's bought off the forums. If the wheels are only ever going to exacerbate a tyre problem, and the runout is unreasonable, then should I be talking to Enkei?

One of the rear hubs was found to have 4 thou runout, whereas the others had 1 thou runout. What does the hub bolt onto, and could that be the problem?
It's so nice to finally be making some headway on this issue, and to be able to drive it at normal speeds in relative comfort.

[greenMachine]

It sounds like a tyre or wheel problem, although a hub/bearing related problem will probably only show up with a wheel mounted.

Try putting the rear wheels on another MX, preferably a similar car that is known to be in good nick. Drive it before, in circumstances where you have found the problem. Then drive it again, in the same fashion on the same piece of road, with your rear wheels/tyres. No problem? - then the problem is somewhere in your drive train.

If the problem stays with your rears, then all you have to do is repeat with a set of tyres known to be problem free (because you tested them as per the previous para), mounted on your rims, dríven the same way on the same car (not yours). Problem remains - must be wheels. No problem, must be the tyres that are the problem.

You have now isolated the problem. Hopefully. maybe....

It might also be worth checking with the local distributors as to what the manufacturing tolerances are, regardless of the outcome.

I presume the wheel balance has been checked a zillion times...

As the vendor of the wheels in question, I have some interest in the outcome.

[Okibi]

I'd go have a chat to Bob and unkey John at Wheelsworld.

They balance wheels within a poofteeth when required.

It would be good if you could chuck your tyres on another set of rims to decide which is the issue, problem is if the tyres have worn unevenly to compensate (if the problem is the wheels).

ALSO .. check your wheel nuts, make sure they're cone shaped on the end that screws onto the stud, you need these to make sure your wheels locate properly.

[Wivvix]

I'd go have a chat to Bob and unkey John at Wheelsworld.

They balance wheels within a poofteeth when required.

It would be good if you could chuck your tyres on another set of rims to decide which is the issue, problem is if the tyres have worn unevenly to compensate (if the problem is the wheels).

ALSO .. check your wheel nuts, make sure they're cone shaped on the end that screws onto the stud, you need these to make sure your wheels locate properly.

The Enkei RPF-1 use a centre-bore locator ring (which each wheel has).

The pirelli dragon's were bought from and fitted at Wheelsworld. John knows me by first name now lol.
John's pretty adamant it's not the tyres, and whilst i'd like to say that's good enough for me, this wheel/tyre related caper has simply gone too far.

Ideally i'd like to swap on a friends wheels/tyres onto the rear. He's got brand new avanti rims wrapped in 195/50/15 RE001's. This will have to be something for next week, permitting he agrees.
I was going to get RE001's originally but John doesn't do Bridgies........ you just can't win.

[greenMachine]

... The Enkei RPF-1 use a centre-bore locator ring (which each wheel has).

...

News to me! Were these in the boxes? If they were, I never saw them... Certainly, the RP-F1s on my car do not have them.

A new test - take these things off, and just use the natural centering action of the wheel nuts to locate the wheels - making sure (as Okibi says) your nuts have a tapered mating surface that matches the taper of the wheel nut recess.

Good luck!

[Wivvix]

... The Enkei RPF-1 use a centre-bore locator ring (which each wheel has).

...

News to me! Were these in the boxes? If they were, I never saw them... Certainly, the RP-F1s on my car do not have them.

A new test - take these things off, and just use the natural centering action of the wheel nuts to locate the wheels - making sure (as Okibi says) your nuts have a tapered mating surface that matches the taper of the wheel nut recess.

Good luck!

They were not in the boxes.

Bob and John from Wheelsworld told me when they went to install the wheels they require centre-bore locator rings on RPF-1's, lots of aftermarket alloys in fact. Bob explained in detail why they required a centre-bore locating ring, but I don't recall now as it was some 2-3 months ago, but basically it was because the lugs don't centre the wheel perfectly on the hub.

I'm using stock wheel nuts (as far as i know), but i'll be changing them over to a narrow type asap. Don't need any more paint damage done to them than there has been already.

According to Goodwin racing;

Takes a standard 73/54 hubcentric ring sold elsewhere on this website. We strongly recommend you do NOT use your factory lugs, a narrow lug will fit better and not scratch your new wheels!

Here
I didn't read the second part, to use non-factory lugs...... sigh.

[Okibi]

Yup I had narrower ones on my zigens, just make sure you remember to place something in your car's tool kit that fits them.

[Wivvix]

Well today was an interesting day.

Went for a drive to a mates place, put his new 15" Advanti rims wrapped in Bridgestone Adrenalins on the rear. Made no difference to the vibration.

This makes me think it's not the actual wheels and tyres, but something which perhaps wheels and tyres interact with. Something which, by affixing the wheels and tyres to the car, makes something else orbit or bend, etc.

It can't be the driveshaft, and it's highly unlikely to be the half-shafts as they spin at very low rpm.

I'm thinking it's probably a wheel bearing, hub, or something else which is affected down the line from having wheels mounted to the hub face.

An explosion diagram or something would really help in trying to visualise all the components from the wheel back to the half shafts

Any thoughts?

[greenMachine]

Well today was an interesting day.

... It can't be the driveshaft, and it's highly unlikely to be the half-shafts as they spin at very low rpm.

Same RPM as your wheels, which you thought were the problem. However, I agree with the conclusion that a straight driveshaft would not be the problem - have you checked the straightness of your driveshafts? Or perhaps slop in the UJs? The more I think about this, the more likely it sounds.

I'm thinking it's probably a wheel bearing, hub, or something else which is affected down the line from having wheels mounted to the hub face.

Could be, if its not the driveshaft. Bite the bullet, get a couple of new (secondhand) uprights complete with hubs. It will be cheaper than replacing bits one by one.

An explosion diagram or something would really help in trying to visualise all the components from the wheel back to the half shafts

Any thoughts?

Good luck, seems like you are on the cusp of resolving the problem.

My apologies, I should have mentioned the narrow nuts.

[Wivvix]

Hello everyone. Just a minor update.

Took the car to wheels world today so that the rear wheels/tyres could be sent off to tyrepower in osborne park for road force variation testing. This is not what I knew it to be called, I believed it was road-force balancing, but whatever. Maybe this is just semantics?

Anyway, apparently they managed to get one rear tyre down to 3.5kg and the other to 5kg.

Now going by what the fellas in the USA reckon, 8lb is desireable, 10lb is acceptable. 5kg is reasonably close to 10lb (11lb).
Does anyone have any comments to make on this?