Knock when braking

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James k
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Knock when braking

Post by James k »

Hi,

I have a knock from the front right when I brake. It doesn't happen every time, usually only the first time I brake in forwards or reverse. I.e. when I pull out of my drive and brake, it knocks, then if I reverse and brake, it knocks again, then again in forwards, but it doesn't usually knock again until you switch direction. I hope that makes sense! It also knocks when I start reversing on full lock.

The kingpin and trunnions have been replaced along with the damper and track rod end. The tie bar bushes were replaced in 2015 and are rubber. The knock was present before the suspension components were replaced and has not gone away. I should point out that these parts were changed for other reasons, not as part of a wild goose chase to find the knock!

Where should I be looking for the source of the noise? The tie bar bushes still appear to be in good condition and are not cracked. What else should I be checking?

Thank you in advance for your replies!

James
simmitc
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Re: Knock when braking

Post by simmitc »

Do you have standard drum brakes or a disc conversion?
James k
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Re: Knock when braking

Post by James k »

Hi,

I have standard 8" drums. I replaced the shoes, cylinders and flexi hoses last week and also checked that the backplates were secure.
serowman
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Re: Knock when braking

Post by serowman »

could be loose backplate
philthehill
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Re: Knock when braking

Post by philthehill »

I suspect the tie bar/tie bar bushes.
The bushes may look good but they may be allowing the tie bar to knock against the tie bar front mount bracket.
The bushes are not like they used to be in that the latest bushes do not have the projection that fits into the tie bar front mount bracket and which kept the metal of the tie bar away from the metal of the mount bracket. The tie bar rubber bushes are not very good at the best of times. A mixture of rubber and poly is best. Rubber behind the mount bracket for articulation and poly in front of the bracket for braking resistance. Bushes with the projection are best.
Check the tie bar rear bolt and bracket for security.

pgp001
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Re: Knock when braking

Post by pgp001 »

I had exactly the same problem, it took a while to identify it as well.

As Phil stated above...........
Check the nut is tight that holds the tie bar fork end onto the lower suspension arm, mine was just a couple of flats from being fully tight and allowed it to move a few thou and cause the knocking noise.

Phil P
simmitc
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Re: Knock when braking

Post by simmitc »

Also check that the body of the bolt is not worn. It should be s snug fit through both the end of the tie rod and the fork.
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geoberni
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Re: Knock when braking

Post by geoberni »

There was a similar problem being asked about on the facebook group recently.
Last couple days when I brake my steering wheel shakes. Today it is so bad it shakes and rattles like mad.
Any thoughts?
https://www.facebook.com/groups/morrism ... 712180884/

After numerous suggestions, some plausible, others not so much, he found that his Tie Bars were fitted with Lock Nuts instead of Castellated Nut and split pin. One side had lost the Nut completely!
Basil the 1955 series II

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philthehill
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Re: Knock when braking

Post by philthehill »

The fitment of a self locking nut to the front end of the tie bar is perfectly acceptable. I have had self locking nuts fitted to my tie bars for many years without problem. I would suggest that having the nut going missing shows a lack of inspection and maintenance. The fitment of the castellated nuts goes way back to the origins of the Minor. For example the eye bolt nut was originally a castellated item but was changed to a spring washer and plain nut.
As regards the tie bar yoke - the tie bar yoke fitted to the Morris Marina is a much better item and does not require the fitment of the roughly made spacer that goes between the yoke and the suspension arm. The spacer was introduced when the top trunnion was changed to allow the fitment of rubber top trunnion bushes. The Marina tie bar yoke incorporates the spacer in its design so fitting the Marina tie bar yoke does not compromise the Minor suspension settings. A self locking nut can be used and was used when fitted to the Marina.
The Marina tie bar which is basically the same as the Minor tie bar was fitted with a self locking nut and a 'R' clip further forward. I have yet to find a Marina tie bar self locking nut up against the 'R' clip.
The bolt that goes through the yoke and tie bar should be a snug fit and there should be no threaded section of the bolt in the yoke or tie bar. Some after market bolts do not have sufficient plain shank and therefore the threads rattle around in the yoke. I use longer high tensile bolts and cut the thread to suit.

James k
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Re: Knock when braking

Post by James k »

Hi,

Thanks for the replies. I've checked the suggested points and I was able to tighten the nut securing the yoke to the suspension arm slightly more, hopefully this was the problem. I also checked the backplate again and the screws are all tight.

I removed the bolt through the yoke and tie bar to inspect for wear and, although the tie bar and yoke do not appear to be worn, the threads on the bolt are badly stripped to the point that they will not tighten again. I have ordered a new nut and bolt to reassemble tomorrow.
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Re: Knock when braking

Post by kevin s »

As Phil says nylock nuts are a suitable replacement for a castelated one, I one has come undone it had probably been re-used. They should always be replaced, at a push they can be re-fitted with Loctite.
philthehill
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Re: Knock when braking

Post by philthehill »

As above - locking nuts of what ever type should only be used once and then discarded.
I agree with kevin s - at a pinch and in desperation use Loctite Loc & Seal if no other option.

James k
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Re: Knock when braking

Post by James k »

Hi,

Are you saying that the nut securing the yoke to the suspension arm should be a nyloc? It's just a normal nut and a lock washer on mine.
philthehill
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Re: Knock when braking

Post by philthehill »

No
The Minor tie bar yoke securing nut is a normal nut with a spring washer between it and the thick suspension arm.

James k
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Re: Knock when braking

Post by James k »

Thanks,

I'll disassemble the front of the tie bar if tightening the yoke hasn't cured the problem. I don't want to change more than one thing at a time.
James k
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Re: Knock when braking

Post by James k »

Hi,

I fitted the new bolt today, reassembled everything and it still knocks. The knock is high pitched and seems to come from quite far back, around under the driver's seat. I can't be certain though, since I can't drive the car and listen around at the same time.

Now, I was just driving home and had to brake quite hard at a mini roundabout with a car whizzing up on the right and there was not only a knock but a loud bang from the same position. It almost sounded like a tapered joint splitting. Luckily it was only a few yards from my house so I could just drive it back onto the drive. It drove absolutely fine. Any ideas?

I'm thinking, firstly, I need to jack it up again tomorrow and check the tightness of every bolt associated with the suspension.
kevin s
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Re: Knock when braking

Post by kevin s »

If it's under the seat I'd take a close look at the torsion bar reaction attachment to the crossmember and check it's not catching on master cyl bolts which have been put in the wrong way round.
philthehill
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Re: Knock when braking

Post by philthehill »

As you have eliminated the tie bar, its bushes and bolt have a look at the chassis leg especially around the eye bolt. The chassis leg is prone to failure around the eye bolt with the first signs of failure being shown as cracks radiating from the eye bolt hole.

James k
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Re: Knock when braking

Post by James k »

Hi, Thanks for the suggestions. I've just checked the chassis leg and I can't see any cracks or other apparent damage around the eyebolt or anywhere else.

I started trying some more involved diagnostics. My driveway is very slightly sloping so you can roll the car forwards and then brake to generate the noise. I asked my wife to do this while listening outside the car for where the knock was coming from. It's a rather frustrating procedure, though, as the car has to be reversed each time to 'reset' the knock.

I only got to try a couple of times before we decided it was too hot and to carry on this evening but I got a slightly better idea of the source. It's not coming from under the driver's seat. It sounds like that in the car but it must just be the sound being transmitted along. It's coming from somewhere behind the wheel. I also tried with the bonnet up to check if it was coming from the damper but it isn't, it's definitely lower down.

Like I said, I'll have another attempt this evening when it's cooled down and hopefully make some progress. It would be a whole lot easier if it made the knock every time and didn't have to be shuffled back and forth!
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