MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Shaking B

I'm posting this for a friend. He has already spent a lot of money trying to solve it, but still the problem remains...

'Can anyone help me?
When I’m braking with my B, the front part of my car is shaking. I have renewed the following parts of the front suspension: 4 wishbones, 2 brake callipers brake pads, 4 wheels, tires, all the bushes, the bearings, nuts and bolts. I’ve largely used my grease gun.

But…
It’s still shaking.
Are there other mechanical parts to change?

Thank you in advance for your advice.'

Anyone got a clue?

Alexander
Alexander M

bolt on or knock off wheels ?
.

sorry, forgot to mention: 15" C wires (were 14" 'standard' wires, problem was the same)
Alexander M

All I can think of is worn hub, or a warped rotor. You mentioned new pads, were the rotors turned ?
.

The hubs were replaced too.
I'll ask about the rotors.
(another thing I forgot to mention: king pins were changed too)

Regards,

A
Alexander M

Just a thought:

When the tires were mounted on the wire wheels, did the person know how to balance wire wheels. Moss catalog shows how the wire wheels should be dynamically (not statically balanced-wire wheels can not be statiscally balanced).

If the wire wheels were balanced at a large tire chain, most likely they were not balanced properly (the balancing cone has to be properly set on the hub), since the kids at the shop have never seen a wire wheel before.

A back up balancing service place would be a motorcycle shop were they deal with wire wheels all the time.

Also give us an idea what occurs when the shaking starts:

I.e. Does it begin right away at 10-15 mph or start around 45mph (sorry do not know KPH conversions), Where are you feeling the vibration, through the entire car or just the steering wheel?
Are you hearing any usual noise from the car when the vibration occurs, if so where?




John Long

J Long

John,

Thanks for the reply!!!

The balancing of the wheels was done at the same company where the wire wheels of my friend's other B were done, and that one brakes just fine, so I think the balancing can be ruled out.

I believe (I'll check later on this day) the vibration is only felt at the steering wheel, I'll check on speeds too.

Your help is very much appreciated!!

Alexander
Alexander M

Nobody here mentioned checking the shocks.

Look for leaks. Check the oil level in them.

Unbolt the upper A-arm on both shocks and push them
through their travel manually. You should feel good, even
resistance throughout.
Daniel Wong

OK, I just visited my friend and here are some answers to a few question:

- the shaking starts at +- 50 kmh so around 30 mph

- it's mainly the steering wheel that's shaking

- the shocks and everything related to them were ALL changed.

- I don't think there's a noise

Hope this helps in finding the solution!

Regards and thanks for the info,

Alexander
Alexander M

Kind of confused here. Does the vibration start when braking from 30mph or accelerating at over 30mph? If it's braking the most obvious fault would be warped rotors. If it's acceleration it would most likely be wheel balancing. Just because others have had success at one shop does not mean they are done correctly. If your friends wheels are older or more out of true they could be harder to balance. A good shop will do a high speed balance after the wheels are balanced and on the car. This involves spinning the wheels at 50mph on the car, with it jacked up.
Tell your friend to switch the wheels from to back to see if this helps. If the front wheels are unbalanced maybe the rear are better.
J Arthurs

Something else to check, although slim, is the front crossmember loose, or the pads worn out?

Jayme
77 MGB
Jayme

When you installed the new shocks - did you work the arm(s) up and down fully
a few times in order to purge out any trapped air in the chambers and valves
inside the shock body?

You have to do this with lever shocks.
Daniel Wong

Daniel and Jayme,

Thanks for the tips, I'll go and tell him today.

J,

As I mentioned in my first posting on this subject (top of this page) it only occurs when braking.

Regards and thanks,

Alexander
Alexander M

Ive been trying to reply to this all weekend but my computer wouldnt let me post the reply, am at work now so ok...

NO one has mentioned the brake discs...!

If it only occurs when braking surely this is the most logical explanation, ive just gone through a similar vein trying to stop my front end vibrating at speed (caused by damaged nearside hub and worn shocks) and also during braking - remedied by changing worn shoes and warped (and very thin) discs.

The more worn the discs become the worse the vibration will be. Trying to stop from 70mph caused the whole front end of my own car including steering column to shake wildly and v uncomfortable.

~PHIL

PS if you guys across the pond call brake discs rotors i stand corrected as it is mentioned above. If not i would seriously recommend changing the discs - the MGOC club slotted with EBC greenstuff pads are very good and before someone slags me off, no im not working on commission, i have just fitted them to my own car and they are spot on! Regards...
Phil

Phil,
Over here across the pond we do call the front discs rotors. LOL.

John
J Arthurs

I'm affraid the disc have been changed too...
Nearly all (if not every) parts near the front wheels were changed for new one, even the steering column.

After installing all those new parts, the shaking was not as hard as before but it still was there!
My friend is really getting sick of it... He's bought all these new parts, but it's still there.

Anyone have another clue???

Thanks for all the replies!!!

Alexander
Alexander M

When you fit new brake discs they should be checked for run out at the rim.

If you put a dial guage on the outside face of the disk near the edge, there should be no more than 2 or 3 thou runout (ie the dial should read no more than 2 or 3 thou from max to min)

More than this and the disk and hub face where they fit together must be examined for burrs or dirt and reassembled - if this doesn't cure the excess runout then try rotating the position of the disk to the hub by 180 degrees.
Chris Betson

Alexander - is it possible the pistons in the cylinders are not moving smoothly and to the same extent - does the car move off to one side when you brake? Were the old pairs of pads evenly worn? Just a thought.

Chris - when you mention putting a dial gauge on the disc are you checking to see if two points (one at the inner edge and one at the outer edge of the disk along the same radius) are in the same plane? And if not by how much do they differ?
Richard Atkinson

Cheers John - suddenly had a thought when i wrote that! ;->

The only other thing i can think of as you've effectively removed every other part of the braking system, is the steering geometry.

Certainly when you've changed a good deal of the suspension items it is good if not standard practise to have a four wheel alignment check. The shake may just be something out of alignment and you are going around in circles chasing rather small in comparison.

whats the play like in the steering and all the linkages? When braking the weight shifts to the front and could cause squirming where theres loose play elsewhere, which is not neccesarily linked to the brakes themselves. Do you feel the wheel trying to squirm in your hands, when under harsh braking?

Last one i can think of is - would knackered engine mounts cause a similar phenomenon?? Long shot that one but it breezed its way into my head from somewhere...

~PHIL

Phil

OK, here another off hand theory.

Bad tie rod ends? ...or a loose tie rod pre-set adjustment at either end of the steering rack itself?

As you're braking, any looseness in this area with cause the wheels to toe-out in an uncontrolled manner, causing the tires to scuff and vibrate against the roadway.

The same thing will happen at speed. As forward motion of the car and road friction combine to cause
the wheels to push rearward - again, the wheels will toe-out and scuff about.

By the way...with all of those new parts installed, was the toe-in checked?
Daniel Wong

Richard, No you are checking that the outer edge of the disc is running true - ie that it is not wobbling in and out more than the 2 or 3 thou. If excessive the run out will shake the caliper from side to side under braking.

You do not want it absolutely true though because the brakes rely on some runout to push the brake pads clear of the disc after braking.
Chris Betson

Alaxander,
First off it souds like the rotors. Vibration from braking from speeds of 30mph is the exact symptom of this. At higher speeds it is not noticable and the car generally vibrates more the closer you come to a stop, so ask your friend if he got new rotors and where he got them from. I would check these first.
After that I think you need to start back to basics. Jack up the front of the car and tighten EVERY nut and bolt on the suspension and steering. After doing this pull/push on every piece to test for play. I'd then check the wheels. Put your hands at the 12 and 6 o'clock positions and push/pull to check for any slack. If any is present, bearings worn. Do the same at 3 and 9 o'clock. Any play here would mean worn tie rod ends. After this set a micrometer up on the brake rotors, the mirometer should be the kind you can sit down and is used to check for run out, and spin the hub. You should see very little change. A few thousands sounds right. Then check the wheels. If they are wires inspect them for broken spokes. Take a spanner and run it across the spokes in a circular motion. If any sound different, normaly a dull sound instead of a clunk, the spoke is broken or out of true. Also, with wire wheels take a mircometer, different one that measures total distance and check the splines on the hub and in the wheel. The wheels should be tight in the splines when you remove/install them, there should be very little slack.
Next, take the car to a GOOD tire shop and have the wheels balanced. Explain your dilema and ask the manager to do a thorough job and to tell you how it turned out. Some places will do the best they can if the wheels are bent and not tell you they are not very balancable. Have the car aligned(front and rear) and ask them to check for a bent chassis, ect.. and see how all the measurements check to factory specs. I think the rear should be 0 degrees vert and horizontal and the front has negative caster and 0 camber. A good tire shop will have all the factory specs.
All of these procedures are explained in detail in the archives if you have questions. If the car still vibrates under braking I cannot think of anything else.

Hope this helps,
John
J Arthurs

Sorry for bothering you guys again,
but I got an idea today:

after we've installed an anti-sway bar on my MGB today, I noticed that when I'd brake at rather high speed, my car would 'tremble' a bit too...

Now I know that the friend I mentioned has the same one (3/4", from the MGOC), so I'm wondering if this could be the cause?

Regards,

Alexander
Alexander M

This thread was discussed between 13/07/2002 and 17/07/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.