Mgb Knocking mystery, and what about Steel wheels?

[hardcastlephil]

Hi All,

This is my first post on here, although I do read through regularly. My current daily driver is a 1971 MGB GT. I've had it since April and spent a few months getting it up to a good standard (new interior, paint job, bushes etc) before August when it became my everyday car.

I absolutely love it, and everything which comes with driving a classic daily, apart from one thing: I have a loud knocking problem which i just cant find the source of. If you have any suggestions please please help as its becoming the bain of my life! so here goes:

The knocking only happens when going over bumps. Its a loud 'solid kind of knock', sometimes with a slight rumble coming from underneath the car. At high speeds it doesn't seem so bad (or you don't notice) but at about 20/30mph over a bumpy road it can be heard over the slightest of bumps.

Its hard to pinpoint where the sound comes from. I'm 80% sure its coming from the front drivers side, but i could be wrong as i understand that the sound can travel. I also think i can feel it through the floor sometimes, but what could be me just getting wound up with it!

Here's what i've checked and done so far:

1) Exhaust brackets moved and checked to make sure it wasnt this
2) New poly bushes in front suspension
3) New gearbox mounts

None of this has helped in the slightest. Can anyone help?

On a side note i've just put the Rostyles back on as 'winter' wheels and i really cant stand them. I've got some minilites for summer and wires aren't really practical for me. I really like the look of the steel wheels with hubacaps from the earlier cars. Does anyone know if i can fit these to my car without fitting the wire wheel axle set up? I don't even mind if they are from a different car.

Thanks in advance for any help!

Phil

[MG Mark]

If your wishbone arms, spring pans and bushes are in good order, then other sources of knocking nisoes obver bumps from the front end could be worn anti roll bar bushes and/or link arms, excessive play in the kingpins/trunnions, and (assuming you have lever arm shock absorbers) internal play in a shock absorber.

Not sure what you mean about fitting steels to a wire wheel axle - from memory, the two axle types are a different width to accommodate the different offsets of wires and non-wire wheels. So, if you have Rostyles/Minilites already, presumably you have a non-wire wheel axle, which would take the earlier MGB steel wheels if that was what you wanted to fit?

MG Mark

[wildoliver]

Wheel wise:

Wires - must use wire wheel rear axle and front hubs.

Steel wheels (inc alloys using bolt fixing) - all will fit all MGBs. IE early wheels on late cars and vice versa.


Re. Clonk.

Could be many things. Check your shocks are secure, if they are loose they could make that noise. 4 short 9/16ths headed bolts around the base of the shock.

Check the engine mounts haven't collapsed/excessively worn. Could be the sump/front of engine catching the crossmember. I had this on a Midget except it was catching the steering column.

Check the springs, if one is broken it would be hard to see unless the car was up off it's wheels but would cause this.

Check the drop links for the Antiroll bar. If a bush has totally collapsed it could cause this. Bushes are cheap.

Failing those come back. The engine mounts are easy to check. Is the gearlever moving on hard acceleration in gear? Does the engine rock when revving it? If you get a lever in to the mount can you move the engine around easily.

The others are just observation and the shock is another lever job.

[alfa pint]

As wildoliver says I'd be checking your engine mounts. I had this on mine and the rubber had perished. Might be kingpins, but the vibration at speed would be pretty obvious too.

Wheel wise - only wire wheels have the fancy hub endings on the axle, so you'll have no problems swapping steel wheels for your minilites for winter.

[hardcastlephil]

Hi Guys,

Thanks very much for this info. I've got the day off tomorrow and have planned to take the car to my parents where they have a decent garage and a pit.
I forgot to mention that i had replaced the ARB bushes too, so hopefully not that.
My first port of call will be the shocker fixings, the more i think about it the more likely it seems. I didnt think it could be the king pins, but this seems possible too - i will check for any excess play again tomorrow.

I really appreciate all the help - will keep you informed of what i find.

Phil

[MG Mark]

hardcastlephil said:

Hi Guys,

I forgot to mention that i had replaced the ARB bushes too, so hopefully not that.

I didnt think it could be the king pins, but this seems possible too - i will check for any excess play again tomorrow.

Phil

Don't forget that the rubber bushes in the actual ARB Link arms can be the culprits, just as much as the bushes in the mounts under the front apron of the bodywork.

Check the kingpins and trunnion play with the car jacked up, wheel off, and a lever under the bottom trunnion to work up and down, which will reveal any excess play in the top or bottom trunnion and/or kingpin bushes. Shock absorber/chassis mountings are easy to check, but because of the spring tension, internal shock absorber wear is more difficult to detect unless you remove the spring and top bolt, to be able to work the lever arm up and down independently of anything else - if there is wear there it will reveal itself - it's a possibility, but only one to check after you have ruled everything else out first!

Good luck,

MG Mark

Edited by MG Mark on Tuesday 19th October 22:12

[hardcastlephil]

Hello!

Great news. I've just been at the garage and gave the shocker bolts a tighten, and its done the trick. I'm over the moon so thank you all very much!

Its funny really as it didn't look like it had been moving and there wasnt much to tighten, but its changed everything about my regular drive.

Next step is to find a replacement petrol tank and then source some early steel wheels.

Thanks again

Phil