Whole car shakes at 100mph, Ideas?

[oaklandm]

Hi.. I have a 1999 c class with 68000 on the clock, coming home from work earlier in a bit of a rush I took the car upto 100mph by mistake but at this point the whole car started shaking quite badly. Anyone else ever had this or have any idea what it could be? Everything is fine and smooth upto this speed and I have no intention of taking it upto 100mph on a regular basis but it does have me quite worried.

Many thanks for any feedback....

 

[Dieselman]

Check the obvious like loose wheels or out of balance wheels or buckled rims, then move onto things like the prop shaft bolts and bearings.

Is the shake through the stering wheel or the floor of the car?


Welcome aboard the forum...and stick to 99mph from now on..

 

[oaklandm]

Think I'll stick to alot less than 99mph from now on : )

The steering wheel does shake at this point which I would have put down to wheel balancing but I've never had that make the whole car shake. Just came as a bit of a shock, thought the whole car was going to fall apart around me. I'm hoping it can't be anything too major otherwise it would happen at alot lower speed but will check thw wheel nuts in the morning and try and get the balancing checked this week.

 

[Dieselman]

Another thought is the steering damper may be shot. Does the steering feel wandery and vauge?

 

[oaklandm]

Steering feels ok, I've not long had the car, know it had a new one about 18months ago and has only done 6000 miles since then. It sat around for a long time and I don't use it every day since I got it

 

[television]

I will go for center bearing on the propshaft or one of the spiders

 

[oaklandm]

Do you know if that is likely to be expensive? Gonna have a look at the cheap stuff first

 

[television]

Put the car in park, jack one side of the car and turn the rear wheel backwards and for wards while looking at the propshaft,any movement up or down should show any faults.

 

[c240yaz]

I will go for center bearing on the propshaft or one of the spiders

I would agree with Television on this. Most likely propshaft balance or hardy splicer UJ.

 

[oaklandm]

Ok, many thanks.. Looks like I'll have a few things to check this week if we ever get any decent weather : )

 

[c240yaz]

but may I add, if it does not vibrate above 70-80, leave it as it is. Why drive above 80 ?

 

[oaklandm]

That is true and I have no intention of going faster than 80 but I just want to check everything now to make sure nothing is gonna fall off : )

 

[DieselE]

If it only happens in a specific speed range then something is either at or approaching a resonant frequency. MB will have designed the car in a way that ensures this does not normally happen within the operating range of the car. The problem is trying to find out what has changed.

Apart from checking round to make sure that nothing is loose and that none of your dampers show any signs of leaking oil, I'd agree with the suggestion that you drive below this speed range. You could well lose your licence before you find the fault.

 

[GRAV888]

I'd agree with the suggestion that you drive below this speed range. You could well lose your licence before you find the fault.

Or one of our members might give you a free ride in THIS

 

[Glenn Smith]

but may I add, if it does not vibrate above 70-80, leave it as it is. Why drive above 80 ?

Very poor idea, something is not right with this car and it should be fixed, C class is very sensitive to out of balance wheels and as the car has stood for a while the tyres may well have taken a set, sometimes this will dissappear with use, personaly, from experience i woulkd be looking at tyres before propshafts, although the rubber couplings are easy enough to check. Why drive above 80? because it's fun and you get there quicker, obviously i only do it when it's safe and legal to do so (auto bahn)!

 

[NW_Merc]

My car used to do that between 90 and 100, but when I got new 17 inch rather than the 15 inch wheels that were on the car the vibration stopped.

 

[c240yaz]

Very poor idea, something is not right with this car and it should be fixed, C class is very sensitive to out of balance wheels and as the car has stood for a while the tyres may well have taken a set, sometimes this will dissappear with use, personaly, from experience i woulkd be looking at tyres before propshafts, although the rubber couplings are easy enough to check. Why drive above 80? because it's fun and you get there quicker, obviously i only do it when it's safe and legal to do so (auto bahn)!

Very poor idea ? Yes I agree that there is something not right with the car and if it was wheel balance, vibration would have commenced in the 50 - 60 range, not 100mph. (They taught me this when I was studying for my City and Guilds 3, HNC, RTITB and HGV test accessor as a motor vehicle technician, although not on MB cars, so I tend to disagree with you. MB C class is no different from any other vehicle in the physics of centrifugal wheel / tyre balance. Of couse, wheel balance could be a contributory factor, but for the whole car to shake, I would think that there may be some other cause, as a few of us suggested earlier.

I would still never drive at 100mph unless I was on a race track.

 

[kth286]

oaklandm

It will likely be the geometry.

If you check the wear on all tyres, particularly the inside edges which you cannot normally see, you will find them starting to wear unevenly.

The car probably needs a full geometry check and adjust.

Experienced this myself at 100 mph in France and it WAS the geometry.

 

[Glenn Smith]

Very poor idea ? Yes I agree that there is something not right with the car and if it was wheel balance, vibration would have commenced in the 50 - 60 range, not 100mph. (They taught me this when I was studying for my City and Guilds 3, HNC, RTITB and HGV test accessor as a motor vehicle technician, although not on MB cars, so I tend to disagree with you. MB C class is no different from any other vehicle in the physics of centrifugal wheel / tyre balance. Of couse, wheel balance could be a contributory factor, but for the whole car to shake, I would think that there may be some other cause, as a few of us suggested earlier.

I would still never drive at 100mph unless I was on a race track.

Old school i think? agree cars used to show wheel imbalance at 50-60, but things have changed and many factors affect this, inlcuding castor angle, wheel size and mass etc. etc. so every vehicle is different in respect of the physics, of course suspension needs checking also, but with the car being stood the tyres will have taken a set, this may right itself when tyres are warm but return next day when tyres are cold, i suggest checkin each thing indivisualy, followed by a 100mph test drive, after checking and testing all day, get some new tyres and it will be cured.(plus you'll have some fun)
I don't think i'll get into a discussion about speed as we all have our own views, but a quick, good driver is safer that a poor, slow one!

 

[c240yaz]

Old school i think? agree cars used to show wheel imbalance at 50-60, but things have changed and many factors affect this, inlcuding castor angle, wheel size and mass etc. etc. so every vehicle is different in respect of the physics, of course suspension needs checking also, but with the car being stood the tyres will have taken a set, this may right itself when tyres are warm but return next day when tyres are cold, i suggest checkin each thing indivisualy, followed by a 100mph test drive, after checking and testing all day, get some new tyres and it will be cured.(plus you'll have some fun)
I don't think i'll get into a discussion about speed as we all have our own views, but a quick, good driver is safer that a poor, slow one!

Point taken, old school, probably. Maybe I have been behind a desk too long also ? Anway, I hope the problem gets rectified but if it only begins at 100 mph, it may be difficult too diagnose, unless the whole car gets checked. I am sure it will !