Member Since: 23 Feb 2024
Location: Wrexham
Posts: 2
Steering wobble
Now then here's something that will challenge, I have a Discovery 3 among it's regular maintenance and repairs,I've been having an issue with wheel wobble under braking from Monday speeds ,so far I've changed the calipers discs tyres on the front had the suspension arms checked they have minimal wear my mechanic who is a land rover nurd doesn't think the bushes are worn enough to cause any issue ,the steering is solid no wandering but we can't seem to get to the bottom of the wobble under braking from speed , he's also checked out the ABS out of ideas now any thoughts ???? As it's driving me nuts and costing a fortune!!!!
29th Feb 2024 9:06 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5068
This can "sometimes" be a devil to solve of D3 & 4 cars, and so this is going to be a slightly long response, sorry .
Generally wobble under braking is a result of one or both overheating brake discs which then become warped when heat is generated by braking. The warping is then transferred from the disc through the pads and up the hydraulic system until it is felt at the pedal. The factors/causes involved are not always straight forward though.
If it's an overheat problem it can usually be down to a caliper fault such as sticking caliper sliders or piston. However, it can also be attributed to the disc not being seated correctly on the hub, usually due to rust or other detritus being present on the hub face behind the disc. It will also be caused if the wheel boss is damaged, or corroded sufficiently to prevent the wheel from seating evenly onto the disc. The other possibility I have come across is the tyre on that wheel, if it's damaged or has a "flat spot" this too can present with similar issues. Worn track rod ends or steering rack components can present similar symptoms too.
So although you have replaced the brakes on the front, it's possible that the disc on the offending side (or both) has again become warped under heat of braking due to a fault. A dead giveaway for this is if the wobble disappeared immediately after you changed the discs and calipers, but returned soon after!!
The solution, (you're not going to like this ) is to strip off the entire front brakes again and start with cleaning thoroughly the hub where the disc is seated. A wire wheel on a mini grinder will do this eminently, just be careful not to overdo it. Next move on to the caliper sliders, you could replace the carriers if they have been on there a long time, but at least replace the sliders and boots and lube with silicon grease. Do not use copper or ceramic grease here, as they tend to become "sticky" after repeated heating causing the pads to remain in "touching contact" with the disc and the inevitable result. Check that the sliders lie evenly in the bores and are not being pulled in due to vacuum (in the boots) or pushed out due to the presence of air. Either can cause the caliper to rest with a slight pressure bias on the inner or outer pad, and a contributory factor to overheating.
Renew the discs and pads with reasonable quality replacements such as Britpart XS, and coat the hub to disc face with a very thin coat of copper grease to mitigate against future rust. Then onto the wheel boss, if it's dirty or corroded you have to be careful not to damage the boss with too aggressive cleaning. I clean with brake cleaner and then very gently and carefully (low speed) clean further the entire surface with a 6" rotary air sander (very fine grit). A rotary sander is ideal as it can be made to sit evenly onto the boss thus reducing the risk of uneven removal of material! Even so, I can't stress enough the importance of being very gentle and totally even with this procedure! Seal the surface again with a very thin smear of copper or ceramic grease to mitigate against salt corrosion.
You may only need some of the above (sliders & cleaning etc) to rectify the issue. But, if you have wobble it's likely the discs are already warping when heated. You will know this as when driving from cold there may initially be little or no perceptible wobble felt, and it only becomes more pronounced with braking as the discs heat up. In any case, it can be frustrating to eliminate this problem, and given the cost and time considerations, I just go for the "Full Monty". As this has always worked first time for me when faced with this problem. Sorry for the long post, but I thought it best to offer my experiences given your mechanic's comments and your ongoing woe's. yµ (idµ - eAµ) ψ=mψ
29th Feb 2024 2:34 pm
L319
Member Since: 14 Dec 2013
Location: Herefordshire
Posts: 2083
I used to work for Land Rover and I know we also had issues with Disc Thickness variation that would give the symptoms you describe . Its when the discs have any run out, or indeed the hub& its bearing, and the vehicle is used a lot for long distance motorway work and slightly sticking sliders or pistons. The brake pad would end up just kissing the disc in one place as it rotates and reduces its thickness in one or two spots . This would result a pulsing in the pedal & variation in the braking resulting in a feeling of wobble . It was not so evident in city or B road type driving as frequent braking would lessen the likelihood of the disc wearing in one place. You could of course have discs manufactured like this as well, if the faces are not parallel
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