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MG MGF Technical - Driving with broken ARB drop link?
My question is basically how far and how safe is it to drive with a broken ARB drop link? Details below.
Front right ARB drop link has broken in traditional place (above bottom bolt). Result is a circular scraping noise when the wheel is quarter to half and more to the right and more prone to that when going over a bump. Also seems to settle down after initial noise when degree of lock is maintained.
I've got to drive the car for short distances (5 miles each way with bends) tomorrow and Friday to get to and from the station and to work. I'm then booked into my repairer on Saturday morning but that is a much longer journey, including some motorway/A-road travel. I've tried taking the ARB off the car, but can't undo the bolts on the LH side drop link for love, money, elbow grease or penetrating oil.
The ARB is clearly rubbing on the inside of the wheel and not the tyre. Given that driven straight there is no contact between the wheel and the ARB and that moderate bends don't provoke the noise, I'm hoping that a few 10s of miles will not be a problem. Sleeping policemen have to be taken very slowly and the rough lane down which I live seems to cause some scraping even when the car is straight. Can anyone with a knowledge of what the ARB does when the suspension is under load help explain what to avoid and why? Any more general view on the advisability of driving like this would be welcome.
Thanks a lot
|Chaz, with the link rubbing against the wheel, I think that it is worth another go at removing the link, just to remove the chance of the stray metal causing more serious damage. Spray everying in penetrating oil now, and give it another go when you've got time this week/weekend.|
Driving short distances with the ARB disconnected won't do any harm; Hydragas has intrinsic anti-roll properties, and the ARBs fitted to Fs aren't that thick. But by disconnecting the front ARB and leaving the rear, you will be altering the handling balance of the car. I am sure you weren't planning on the limit driving on the way to the repairers, but be aware that the car will now be prone to much more oversteer than before as the rear is now relatively stiffer with the front ARB disconnected.
Hope that all will be fixed soon!
|Hi Rob, just the man I need. Thanks for the advice. I understand about the effect of driving with ARB removed though the AA man suggested understeer which didn't make sense.|
Judicious driving to the station this morning revealed no rubbing/grating sounds at straight ahead up to 50 mph on smooth roads. At low speeds on uneven car park surface or the unmade road to my house, the ARB must rub against the wheel even when going straight ahead. Does the ARB get pushed down when the suspension compresses - ie the wheel is pushed up by the road? Sorry for the daft attempt to describe suspension movements, but I would really like to understand this.
Similarly, low speed circles on relatively flat surfaces cause the rubbing depending on the degree of lock. The ARB does not rub when the car is up on stands whatever the lock, so this too must be a function of the vertical change in ARB position because of what the suspension is doing.
I'll have another go with the socket set and penetrating oil, but time is the real problem. Work kept me up until 2.30am this morning and may do so again for a few days. I'm off to the menders on Saturday morning and if I have to get there with the ARB still fixed to one side of the car, I want to know how best to drive it!
|Hi Chaz - the ARB moves in the same direction as wheel travel - i.e. when the wheel moves up, the link will move up too.|
When both links are connected, the link's movement is influenced by the wheel movement on the other side of the car - so if the wheel moves up on the opposite side, the ARB will try and move the wheel on the same side as the link in the same direction - even if the wheel is actually down (basically how the ARB works - clumsy description, sorry, but seeing it in action it's immediately obvious what's going on)
|Thanks Rob. I think I understand the straight line travel effect. In normal conditions (ie with the ARB connected) the ARB and the wheels move together and I can sort of sense how that tries to prevent roll. |
However, with one side's drop link broken, then the wheel on the broken side doesn't take the ARB up as it travels over a bump, hence the grating noise as the ARB end and broken link comnes into contact with the inside of the wheel. Movement up or down of the opposite wheel (still connected) will move the loose end of the ARB in the same direction, so if the left wheel drops down into a hole, the right side of the ARB could drop onto the wheel also, right?
What I still can't follow in my head is what happens when turning on smooth roads (no up/down wheel travel). Certainly a 90 degree RH turn causes the grating noise (and a something less than that, though more gentle sweepers don't) but with the car on stands (and therefore the suspension unloaded?) the ARB does not touch the wheel no matter the amount of lock in either direction. Can anyone explain (even just to satisfy my curiousity) how the suspension and in particular the ARB react to turning the steering wheel when the car is in motion?
|>> Movement up or down of the opposite wheel (still connected) will move the loose end of the ARB in the same direction, so if the left wheel drops down into a hole, the right side of the ARB could drop onto the wheel also, right? <<|
Yes, exactly :o)
>> What I still can't follow in my head is what happens when turning on smooth roads (no up/down wheel travel). Certainly a 90 degree RH turn causes the grating noise (and a something less than that, though more gentle sweepers don't) but with the car on stands (and therefore the suspension unloaded?) the ARB does not touch the wheel no matter the amount of lock in either direction. <<
The answer here is body roll: as the car turns into a corner, then in a speed related way, the car leans towards the outside of the corner, as dictated by the centre of gravity of the vehicle.
Therefore, as you turn right, the left hand suspension is compressed (outside of corner), whereas the inside right hand suspension is extended. Combined with full lock, this may be enough to result in components 'coming together'...
|OK, Rob, beginning to see what might be going on. Interestingly, the noises are worse at low speed rather than higher speeds (not been above 50mph) and I wonder if that is because the hydragas is working harder to keep things level.|
Took a look at the Carbibles' suspension pages, from which this is a quote:
"When you head into a corner, the car begins to roll out of the corner. For example, if you're cornering to the left, the car body rolls to the right. In doing this, it's compressing the suspension on the right hand side. With a good anti-roll bar, as the lower part of the suspension moves upward relative to the car chassis, it transfers some of that movement to the same component on the other side. In effect, it tries to lift the left suspension component by the same amount. Because this isn't physically possible, the left suspension effectively becomes a fixed point and the anti-roll bar twists along its length because the other end is effectively anchored in place. It's this twisting that provides the resistance to the suspension movement. "
In my case, with one end loose my ARB can't twist in resistance to the suspension movement and any movement in suspension above a certain amount must cause the dangling RH side to connect as Rob says. Observations from this morning suggest that low speed turns in both directions can cause the ARB to connect with the RH wheel, whereas high speed sweepers do not (less body roll with hydragas doing more?). Also the fact that the noise goes off once lock is applied and held, suggests to me that the initial movement of the suspension on the RH side doesn't "get out of the way" of the ARB to begin with as the LH side movement pushes the ARB inwards (which would usually cause a resistance to twist and limit the LH side movement) but once the angle of travel is set, may be the suspension takes the wheel out of the contact zone.
Also discovered that humps and bumps are more a case of controlling pitch than anything else. Braking gently at walking pace as I come downhill to my gate on an unmade road causes contact of ARB to wheel, but coming off a raised traffic calming area does not, so long as I go blow speeds at which the nose dives.
well, if I can't get the LH bolt undone on Saturday morning, it is off to the garage on a longer journey of exploration! Thanks for all your help Rob and I'll report back anything interesting. (PS: MS ali drop links are gorgeous, if probably unnecessary.)
Just to report that the MGF was fine on long journey to garage. No grinding noises as ARB contacted wheel even at motorway speeds or around roundabouts. The more I thought about this and drove around, the more it seemed that differential heights of the wheels was the main cause of the ARB contacting the inside of the wheel. In fact a relatively small bump can cause the contact - if you look at the usual position of the ARB relative to the bottom of the inner wheel rim you'll see that there is only an inch or so. Kept pretty level, there were no problems.
New ARB drop links fitted. The MS ali versions are drop-dead gorgeous, even if a gross over-indulgence.
Cheers and thanks for the help. I hope that this will be useful to someone else in the future, who doesn't have the time or kit to do the job themselves.
|Glad to hear that it's all sorted :o)|
This thread was discussed between 18/10/2006 and 23/10/2006
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