wheel locknut

[dafix]

Hello,

I have finished the job on the front brakes of my DAF46. The M24 nut that maintains the bearing and the drum on each half-axle had been dented with a hammer (?) to be forced into a groove along the axle, in order to be locked. I ordered new nuts from Dafhobby and they are "Nylstop": they have a nylon ring inside to keep them locked under vibrations. I installed them but I am a bit skeptical regarding the safety. Does anyone have experience with these locknuts ? Should extra locking measure (loctite, pin ?) be taken ? From what I have read, nylon locknuts are efficient but are "disposable" and must be replaced if they have been removed.

[andrew]

I've never carried out any work on a Daf 46's brakes, but I recognise the "denting" to which you refer; in English garages this is called "peening" and secures the nut, by "nipping" it in place. A castellated nut together with a split pin serves the same purpose.

Back in the late 1970s the V.W. garage which I worked used "Nylock" nuts to secure brake components and axle bearings. "Nylock" was a brand name and I suspect "Nystop" is a similar product. We NEVER had any problems with these nuts unwinding themselves after fitting, but I remember being told to tighten them up in one go and not to loosen them, even a little, once they were done up. They were a "throwaway" item and "Nylock" nuts, once removed, were NOT to be reused.

If Danny as DafHobby has supplied them he's clearly "done his homework" as to their safety, so I wouldn't have any concerns on that score.

I hope this reassures you!

[dafix]

Hello Andrew,

Thank you for your reply. These nuts are called "Nylstop" in France, perhaps it's a brand there, I don't know... Yes, I guessed it would be bad to loosen them, even a bit, so I tightened them slowly, shaking the drum after each small spanner move clockwise, until no lateral play of the drum was noticed when shaking it (There is no torque indicated in my workshop manual). Now, I have to adjust the carburettor to reduce the CO level: it is too high and I got rejected for that at the "Contrôle Technique" (equivalent of the MOT on this side of the Channel). Another reason for rejection was the problems with the front brakes (which, after a short test drive, seem now fine). Hoping my DAF46 will be ready for the next spring (anyway I am not so eager to drive it now because of the weather).

[andrew]

If it helps, I spent ages fiddling with my 33 before the emissions were right, so I've had some experience of it! The good news is that, at the last test, my M.O.T. tester was very impressed with my Daf's exhaust readings. In the United Kingdom a car of my Daf's age (it's a 1972 car) is exempt the M.O.T. test anyway, but I always test it every year, just to be sure.

The problem with a Daf is that the tick-over speed not only controls the idle speed, but also the clutch engagement, so it has to be low enough to prevent the clutch engaging but high enough to keep the engine running when the brakes or low hold switch are activated. Both of these actions weaken the mixture and it is here that the adjustment becomes critical. If your tester says the CO is too high it means the mixture's too rich, so find the mixture screw (it's the one at the back of the carburettor, low down-it's NOT the idle speed screw) and turn it clockwise about half a turn. Turning it clockwise will wind the screw INTO the carburettor & weaken the mixture. Now take the car for a run and confirm the car doesn't stall when the brakes are applied or when the car comes to a halt with the brakes on. Ideally ask your C.T. (controle technique) garage to adjust this while it's under test, if they will, and they'll be able to screw the jet in while monitoring the CO level. It is a fine adjustment, so ask the garage to do it s-l-o-w-l-y and wait a little between adjustments.

You say it was too high. The required setting for a Daf 46 is 3.5-4.5% CO; what was you car reading?

Happy to help more if needed! 

[bobdisk]

What Andrew says about nylon locknuts is exactly correct. I use them in my work, the Nylock nuts come in all sizes form 3mm upwards. I must admit I have not heard of them used in this application. I remember "stake nuts" being used on the hubs of my father's Talbot Samba. There a is ring around the outside of the nut (where the nylon ring is) that is knocked into the slot on the stub axle to lock it.

[dafix]

Hi,

The measured CO level is 9.49% (the allowed upper limit is 4.5%), so it's quite high.

[andrew]

That's FAR too high! I would screw in the mixture screw a couple of turns and ask your C.T. garage to assist. Their machinery will be able to adjust the mixture to give you a correct reading. As I said, the reading should be 3-5-4.5% CO.

Good luck.......