rocket mk 1 front hubs

[moz]

Hi has anyone had issues with rocket front hubs having realy bad movement in them like poss stub axle fault just had my car recovered to a gge and they reported that the front ns wheel looked like it could fall off, i did notice the wheel seemed to pull out from the top when the wheel straps were tightend up on the recovery truck

[martinw]

Hi Moz

Really need to establish where the movement is coming from. There are a number of different front upright / stub axle assemblies that can be fitted - from Cortina to fabricated steel, or alloy - but what they all have in common is that the front wheel bearings are taper rollers. These need to be tightened up, but then slackened off to allow them to rotate properly, without excessive movement. That is of course putting it very simplistically. It could well be that your bearings need to have the wheel stub nut tightened.

Other than that movement could be arriving from the top bearing (usually a Transit drag link) or the bottom bearing (usually a Maxi ball joint) if either of them are worn. The last possible source is the inner wishbone bushes if they are worn significantly.

My guess is the wheel bearings are either worn or insufficiently tightened.

Martin

[carlyd]

I would check that the bolt that runs through the centre of the stub axle is tight. 
I noticed on my Rocket that it can unscrew itself, it did this twice on mine even though I used threadlock.
It only happened of the nearside (left side when you are sat in the car) though as the other side is self tightening.
I always thought that near side should be a left hand thread to stop that from happening.

[moz]

yes thanks thats what i thought it might be, i didnt know how the set up was done but having seen an exploded view of the hub it seems the stub is a seperate part and actualy bolts in.I cant see it myself now because ive sent the car back to scotland to get the engine retuned and get it through an mot. Hopeing that the hub will tighten up if not could be looking at replacing them, and this could be the reason ive got very spongy brakes the hub flexing and pushing the pads off the discs hope so because it was looking like maybe having to fit different master cylinders . hey ho the fun of owning a kit car

[moz]

Forgot to say it is the n/s thats come loose

[carlyd]

May 14, 2018 9:53:31 GMT moz said:

Forgot to say it is the n/s thats come loose

Yes that's the side that unsrews itself.
I also had the bolt snap while trying to remove it.
Poor design IMHO, I had to buy a replacement twice from Rally design, I think were about £25 each. I don't know what the fix is unless you can find one with a left hand thread.

[Stiggy]

That is worrying, if the stub axle has come loose it can move about and stretch the hole, this would mean a replacement stub axle or just tightening it up is not sufficient. The stub needs to be an interference fit. You also need to torque it up to manufacturers spec and use a spring washer. Also ensure the thread is long enough especially if wing stays and a sleeve are added to the centre bolt. Wings mounts will cause vibration and will ensure the centre (all important bolt ) will come loose!
Using thread loc is a real issue, check the spec, most of them are for use on items that require disassembly. Others are for studs or bearings. Others only work on certain metals such as brass. Check this stuff;
Truloc Superfit 268 is a high strength and moderate temperature retainer, ideal for assembly of parts that do not readily require disassembly.

[kiwicanfly]

When I bought my torque wrench I experimented by trying to undo bolts with allen keys that had been tightened to the corect torque with the wrench and found it impossible on anything bigger than m8.

Thus tightening to the correct torque is equally impossible without a torque wrench or decent extension at least.

Correctly torqued with a locking washer (I favour Nordlock washers) behind the head negates the need for a locking compound.

For what it's worth NZ prohibits the use of locking compound as a sole means of locking bolts as it is impossible to do a visual inspection at certification, whilst actually using is not an issue it is not a substitute to correct torque and a mechanical locking device.

[Stiggy]

Rally Design do not specify the correct torque for these stub axles, we are left in the dark, they should be outlawed, drawn a cross hot coals shot and left to die, survivors that sell such items should be shot again!
Using compound, a spring washer, a guess at the correct torque and a decent bolt may alleviate the problem of your wheel falling off.
NZ may prohibit compound for reasons unknown to me, I prefer belt and braces.

[kiwicanfly]

Torque requirement is easy, it is whatever the bolt rating is not the axle itself.

NZ doesn't prohibit the compound, it prohibits it's use as the sole means of locking as an inspector cannot establish whether any compound has been used by visual inspection whereas the presence of a locking washer can be observed.

In order of importance would be correct torque, lock washer, compound.

I would not be the least suprised to find that list reversed in many many builds.

Also a point to consider is that in order to torque correctly the coefficient of friction between the bolt and "nut" needs to be accounted for and a lubricant is often required which compromises many compounds.

[Stiggy]

A 12.9 bolt of 12mm dia should be tightened to 125Nm.
We don't know if the axle will stand that, it might, it might not.
Compound used on threads is different to that used on the axle, I use bearing/stud compound on axles NOT THREAD LOCK.

What compound have builders used and where?

What torque have builders used?

Anyone else had an issue with them coming loose?

[kiwicanfly]

I used Bumax bolts, true high tensile stainless, which require to be torqued to 115Nm, with Nordlock washers under them.

I would be interested to know how many builders torque up bolts correctly across the board. A decent torque wrench is not cheap and I would not be surprised if many did not buy one.

[carlyd]

I didn't use a torque wrench but I did have to remove the axle for some reason and managed to sheer the bolt off whilst trying to remove it, so it must have been tight. It's all documented in my build diary. I then switched the bolts for 12.9 allen bolts with threadlock but the passenger side still unsrewed itself. In fact when a potential buyer came to test drive it I noticed the bolt was about 2 - 3 inched out (unscrewed itself) and when I tried to tighten it sheered off again. I had to buy another new one. Very poor design IMHO.

[moz]

yes i agree about the poor quality the garage said he had never seen a worst case as on mine both hubs were very loose he was surprised the wheels hadnt fallen off luckily i havent been more than 1/4 mile in it since buying it because it wouldnt pass an mot on emissions and the play was noted, i thought it was just wheel bearings needing adjustment.

[Stiggy]

I wonder if this addition would help.