Member Since: 22 Aug 2013
Location: Dublin
Posts: 145
cracked lower arm
Hi all, I had trouble tracking my disco 3 after I changed the tracking arm a few weeks ago. After two attempts I brought it back again for them to look at it as I was sure there was something wrong (knocking sound when accelerating/breaking). Anyway up on the ramp the guy was shocked to find that my lower right arm was cracked where it meets the rearmost bushing (its now oval not round). So I bought a replacement arm and have found a garage to replace it tomorrow.
Is this a job I can trust with a non LR specialist (I have air suspension)? Also the new arm comes with standard bushings but mine has polybushes, should I ask him to replace the bushings at the same time? Or is it OK to mix them?
Thanks Ian
27th Mar 2014 3:29 pm
waterbuoy
Member Since: 26 Oct 2013
Location: Argyll
Posts: 2887
I would have thought NO to mixing the bushings.
I may be off the mark here, but might the fact that you have polybush bushes be part of the problem? Whilst harder wearing, they can transfer the shock loadings to other components of the vehicle. What type/colour of polybush are they?Currently 2009 Disco 3 SE, 2013 MY D4 HSE and 2016 D4 SE
Previously:
TD5 Defender 110 CSW (230k miles)
300TDi Disco 1 (289k)
4 RR Classics (300-350k each, 2 manual, 2 auto)
110 V8 CSW (220k)
S3 109 hi cap pickup (ex RN)
S2A 88 Safari SW with lpg conversion (bloody lethal)
But, this is the component that is getting the shock loading the poly bushes would transfer more of that to the chassis than the OEM bushes, due to them being firmer
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D4 & RRS style D3 grilles made to order
27th Mar 2014 3:39 pm
IanMellor
Member Since: 22 Aug 2013
Location: Dublin
Posts: 145
waterbuoy wrote:
I would have thought NO to mixing the bushings.
I may be off the mark here, but might the fact that you have polybush bushes be part of the problem? Whilst harder wearing, they can transfer the shock loadings to other components of the vehicle. What type/colour of polybush are they?
Mine are red in colour
27th Mar 2014 3:44 pm
waterbuoy
Member Since: 26 Oct 2013
Location: Argyll
Posts: 2887
If I'm wrong then happy to admit it, but surely the stiffness of the bushes can increase loadings on both the chassis and the arm if there is less 'give'?
As an analogy, if I am driving in a fence post I prefer to use a wooden handled sledge hammer as it is kinder to both my arms/hands and the post. I have tried a more ridgid fencing maul but this results in (a) knack d hands, and (b) bugg d fence posts! (and the inability tohold a pint for too many hours!)Currently 2009 Disco 3 SE, 2013 MY D4 HSE and 2016 D4 SE
Previously:
TD5 Defender 110 CSW (230k miles)
300TDi Disco 1 (289k)
4 RR Classics (300-350k each, 2 manual, 2 auto)
110 V8 CSW (220k)
S3 109 hi cap pickup (ex RN)
S2A 88 Safari SW with lpg conversion (bloody lethal)
Seriously though, the bush is stiffer agreed, but the bolt is just as free to rotate in the metal sleeve of a poly as it is an OEM, so the torsional force should be the same and not cause the steel to fail or tear?
A seized bolt as they do or weak arm could exacerbate the issue and increase the forces at play though?
Not sure the bush alone is at fault if in deed there is any other than a well used part, metal fatigue does happen after all Altox GSM FBH controller thread
IID Pro MV License - D3, D4 & RRS - Enabling, Updates, D4 & RRS Timed / Remote Climate, D4 Bluetooth fitting
PM me for details
Owner of the original "Beanie" grille
D4 & RRS style D3 grilles made to order
27th Mar 2014 5:02 pm
Biffysun
Member Since: 09 Jul 2011
Location: Central
Posts: 1788
Seem to recall a post in the last couple of years someone who had a similar problem, whether it was due to the fitting of the bushes or whatever I can't recall .... heading for shelter now!
27th Mar 2014 5:22 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26750
^ as above. There has definitely been an instance of this before. I think the conclusion was that the pressing out of the original bush over stressed the wishbone and it then cracked.
One to watch I think.
27th Mar 2014 6:49 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26750
Member Since: 22 Aug 2013
Location: Dublin
Posts: 145
This looks similar to what is happening to me.
I am always very concerned about heat being used excessively to loosen nuts etc.
When they did my tracking the first time the guy heated up a nut until it glowed red hot.
Surely i little heat is all that is needed to break a ceased nut and bolt! Loctite do a freezer for a similar purpose.
Anyway I digress...I will have a right upper wishbone with standard bushes and a left with the red polybush ones. Is that OK or will I get the guy to remove the standard ones?
27th Mar 2014 9:52 pm
L319
Member Since: 14 Dec 2013
Location: Herefordshire
Posts: 2081
Any steel parts such a bolts heated to red heat need to be scrapped as the strength characteristics of the metal could have been seriously impaired. The same goes for steering joints etc. Car now have lots of high strength steels in there construction which are less tolerant to heating/cooling. It is possible that anything above about 300 Celsius could change the properties.
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d hands, and (b) bugg 
