MG4 X Power Vibe/Hum 65 to 75mph

[Bricktop X PWR]

A quick search confirms use of CV joints is very common in cars, particularly FWD ones. So if that’s what MG have done I see no problem in principle.

No ones complaining about the CVJoints per se,
(Although, until we find the actual answer, who knows?)
but the alignment does seems odd to me.
Never seen that before.

 

[PristDean]

No ones complaining about the CVJoints per se,
(Although, until we find the actual answer, who knows?)
but the alignment seems odd to me.
Never seen that before.

The alignment to appear misaligned for those joints is normal. They are designed to deliver power at a constant despite angle, bumps, turns and steering through full arc.

It may possibly be poor lubrication of a joint causing vibration / hum through unintended friction which may become more audible at a certain speed & frequency. It's a difficult one to check, unless you can put the car on a rolling road ramp. But worth checking, given my Air Con contained zero oil in the gas from factory ! lubrication may not be their strong point ... certainly not with lubricating the wheels of great customer service !

 

[Deleted member 14300]

Well, my SE had a brrrrrr vibration at 80 last week. At first I thought it was the road surface, but it did it on the A42 and A50. Common denominator the car. It disappeared eventually, but looking how the tyres scrub, is it something like this what's causing it? I did identify the car's too light on the front end at high speed.

 

[JustAnotherMidlifeCrisis]

No ones complaining about the CVJoints per se,
(Although, until we find the actual answer, who knows?)
but the alignment seems odd to me.
Never seen that before.

I think the whole point of CV joints is that they allow power transfer at an angle. You wouldn't expect to find the power unit and drive shaft aligned where a CV joint is used.

What interests me is that, according to the reports on this forum, the vibration/hum is limited to a fairly narrow range of speeds. If the entire CV joint set-up were faulty you'd expect noise at all speeds, surely.

So to my mind the issue isn't lubrication and isn't the use of a CV joint as such. Could still be resonance.

 

[Ian Key]

Well, my SE had a brrrrrr vibration at 80 last week. At first I thought it was the road surface, but it did it on the A42 and A50. Common denominator the car. It disappeared eventually, but looking how the tyres scrub, is it something like this what's causing it? I did identify the car's too light on the front end at high speed.

It might be worth having your tracking checked.

 

[Fogey]

I think the whole point of CV joints is that they allow power transfer at an angle. You wouldn't expect to find the power unit and drive shaft aligned where a CV joint is used.

What interests me is that, according to the reports on this forum, the vibration/hum is limited to a fairly narrow range of speeds. If the entire CV joint set-up were faulty you'd expect noise at all speeds, surely.

So to my mind the issue isn't lubrication and isn't the use of a CV joint as such. Could still be resonance.

Thing is, (suspension?) resonances need to be excited in order to be apparent. Maybe the excitation source is "cogging"? Or associated with the front axle alignment?

 

[JustAnotherMidlifeCrisis]

It's possible. Or it could just be that the vibrations that naturally occur when the car goes at 65-75mph happen to be at the resonance frequency of the FWD apparatus.

There's no way the MG engineers would have missed this. And given the warranty cover, my guess is they took the view it won't shake the car to bits and customers should put it down to getting what you pay for.

Will SAIC/MG respond to people raising this? Absent a clear case of it being shown to cause hazard, I doubt it. But then I'm cynical.

Not directly pertinent perhaps but SAIC is state-owned. So it's you v PRC, ultimately.

 

[Ian Key]

Will SAIC/MG respond to people raising this? Absent a clear case of it being shown to cause hazard, I doubt it. But then I'm cynical.

Good question but if it's not reported to the dealers so they can report back to MG by everyone who owns an XPower they will ignore it.

 

[JustAnotherMidlifeCrisis]

Good question but if it's not reported to the dealers so they can report back to MG by everyone who owns an XPower they will ignore it.

Agreed. Be nice as well if SAIC can, like, re-engineer the entire front end before my Xpower arrives next month.

 

[Ian Key]

Agreed. Be nice as well if SAIC can, like, re-engineer the entire front end before my Xpower arrives next month.

It must be nice to live in your world with flying pigs and blue moons ?

 

[Macadoodle]

Even if the extreme driveshaft angle is not the cause of the vibration it still seems like a really odd thing to sign off.
There will be constant parasitic losses in all 4 joints because the balls slide fore and aft as the joint rotates at an angle.
Maybe it wont amount to much but it will be there.

Vibration dampers are often fitted to these type of driveshafts, I've noticed them on cars I've owned in the past, maybe the solution is as simple as that ?

 

[JustAnotherMidlifeCrisis]

You say it's an odd thing to sign off. But if that's true when is a CV joint ever acceptable?

 

[Macadoodle]

You say it's an odd thing to sign off. But if that's true when is a CV joint ever acceptable?

As bricktop mentioned, manufacturers always tend to design their powertrains so driveshafts end up as straight as possible.
Yes, a constant velocity joint is designed to transmit rotational power through an angle but there's still losses and wear associated with that.
Makes much more sense designing your system to allow the shafts to spend 90% of their life just rotating ,with minimal bearing slide.

MG have managed it at the rear, one of the first things I noticed when crawling around under my SE, I'm odd that way

 

[Bricktop X PWR]

MG have managed it at the rear, one of the first things I noticed when crawling around under my SE, I'm odd that way

You Sir, are most certainly not odd.
At least I know there's two of us now! ?

 

[Bricktop X PWR]

So here's something I've not noticed before.......
Today on the way to Haverfordwest I gave the car a good hard dose of accelerator and went straight through the 65-75 zone
still on full power (in Sport) right up to 76.
(M'Laud) and when I dropped back into the zone, I swear the vibes were gone.

They did return later, but because I am now super sensitive to it, I am sure they were absent.
Might all be in the mind.

Looking forward to some of you guys commenting later as I know a couple of you are out and about "testing"

The long and the short of it though, for me, the kind of driving I do, and in my personal situation, I love this car and everything it can do.
It's not going back to the dealer anytime soon.
Hell! I'm even thinking about cleaning it!!!?

 

[Quidgebo]

Very glad it wasn’t my imagination.
Have a Trophy yet took the X-Power out for a test recently and had this exact hum/vinration/reverb experience at 60+mph. Completely put me off switching.

My trophy had some reverb and vibration at delivery yet a tyre change due to flat spots and rebalance seemed to help that. Yet the XPower was waaaay worse and noticeable.

 

[Deleted member 11291]

Hell! I'm even thinking about cleaning it!!!?

About time ?

 

[Bricktop X PWR]

Very glad it wasn’t my imagination.
Have a Trophy yet took the X-Power out for a test recently and had this exact hum/vinration/reverb experience at 60+mph. Completely put me off switching.

My trophy had some reverb and vibration at delivery yet a tyre change due to flat spots and rebalance seemed to help that. Yet the XPower was waaaay worse and noticeable.

Funny you should say that m8,
I've completely discounted wheel balance and tyre issues because of what's been said and done with the Chinese version of Xpower (wheels balanced, tyres changed etc etc)
But today on my way home I very nearly went into a tyre place to get all four wheels rebalanced just to rule it out.

I'm booking into a tyre place next week just to discount any imbalance on my particular vehicle.

 

[Bricktop X PWR]

About time ?

Dirty.

Clean.

But not for long cos I'm 1 mile from the main road ?

 

[PristDean]

@Bricktop1967 As usual on forums such as this, there is a whole load of pure speculation from people making educated guesses at best, I include myself in that.

If this is a problem you still want resolved (after you have tried wheel balancing), I'd advise seeking out an independent specialist (as I did for my air-con) to obtain an engineers report on the issue. You can then present that to your dealer's 'Technician' so you are going in fully armed to claim under warranty and not just with your 'suspicions' of a fault, which is when many dealers will try to fob you off.
Anyway, good luck with the issue.