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Thread: Check you upper wishbone mount rods now and again, plus new bushes

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  1. #1 Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member Patrick's Avatar
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    I changed the upper bushes today. They were rally design ones, which I’ve now replaced with Powerflex. I thought the bushes had worn as things didn’t look straight anymore. Turns out it was actually the rod which was bent and the bushes are OK. I’m going to use two of them on the diff mount (still original rubber mounts) and keep the other two as spares so it wasn't a waste getting the new ones:



    It’s pretty clear this is not so good, both sides were bent, this one was worse:



    As I don’t have replacement materials to hand as a temporary measure I’ve straightend out the rods. Here are some sizes for reference:







    Installation of new bushes:







    These are powerflex product number PFF19-10 – also available in the black series which is a higher shore hardness: PFF19-102BLK

    As for the mount rod, I need to figure out what grade of metal to get. I'm assuming stainless, 304/316 I don't know if those are suitable for this application. I've read there are much stronger grades of stainless that have double the strength of 304, no idea if thats needed.

    Can anybody recommend something suitable?

    I'll need to be able to cut an M10 thread into either end of whatever I get.
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  2. #2 Re: Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member stevejgreen's Avatar
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    A slightly stronger grade of stainless compared with of 304, the commonest stainless, is 302. Same corrosion resistance but a slightly higher carbon content.
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  3. #3 Re: Check you upper wishbone mount rods now and again, plus new bushes 
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    Why stainless?
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  4. #4 Re: Check you upper wishbone mount rods now and again, plus new bushes 
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    Hmmm, given the task this rod performs I wouldn't have contemplated straightening the rods and putting them back unless, of course, this is just to check the new bush alignment? Any rod that has been bent and then straightened will lose some of its strength and also be more susceptible to breaking.
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  5. #5 Re: Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member Patrick's Avatar
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    I don’t know what material i should use. I need consult with someone who knows metal. If different metal is better for the application I will use that.

    Looking at bolts / metal strength tables stainless probably isn’t the right stuff.

    Reassembly was only for fitment testing and so I don’t need to leave the car on axle stand. Won’t be driving until I replace them
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  6. #6 Re: Check you upper wishbone mount rods now and again, plus new bushes 
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    Hi Patrick. After experiencing a minor shunt with mine (and I know that no two prangs are identical) a couple of years ago, resulting in both bars being bent S shaped, I figured that the original bars had done their job perfectly. They had deformed, the upper and lower wishbones had buckled, a steering rack mounting needed straightening and the rack replacing. The chassis however was unmarked, so I replaced the bent items and with some cosmetic work was back to square 1.The bars were made out of silver steel which I'm fairly sure was the original spec.IMHO the tensile strength is not as important as the shear strength in this application but I'm no metallurgist
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  7. #7 Re: Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member Patrick's Avatar
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    Thank you that’s really helpful info
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  8. #8 Re: Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member Patrick's Avatar
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    Decided to order some silver steel to make new parts and get it back on the road. Better than the fatigued metal in there now. I’ll investigate further into other metals later. I’ve not got 100% faith in the OE stuff given that they bent under normal driving conditions (I have less than 7000 mile on it). Or maybe that’s just because Hampshire has terrible roads. On the plus side it’s not a very expensive repair.
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  9. #9 Re: Check you upper wishbone mount rods now and again, plus new bushes 
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    Quote Originally Posted by Patrick View Post
    Decided to order some silver steel to make new parts and get it back on the road. Better than the fatigued metal in there now. I’ll investigate further into other metals later. I’ve not got 100% faith in the OE stuff given that they bent under normal driving conditions (I have less than 7000 mile on it). Or maybe that’s just because Hampshire has terrible roads. On the plus side it’s not a very expensive repair.
    Hello Patrick,
    I believe that silver steel is relatively soft in the as supplied condition (circa 270HB/27HRC). It will harden up with heat-treatment but I assume you won't be doing this.
    I could probably sort you out some quench & tempered 45SiCr or 51CrV4 material around 10mm dia. This will be 78Tons/Sq. Inch VS 61T (37HRC/27HRC).
    I'm busy getting the finishing touches done on my Marlin 5exi in readiness for the Stoneleigh Show on Sunday but I could bring a couple of pieces with me if that'll help?
    If you can confirm the dimensions, I may even have time to make them for you.
    11.5" long with 1" long M10 thread?
    Let me know.
    Last edited by leadfoot; 30-04-2019 at 02:29 PM.
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  10. #10 Re: Check you upper wishbone mount rods now and again, plus new bushes 
    frequent forum contributor Club Member David's Avatar
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    I'm sure I recall from my rallying days that you should take care putting uprated bushing in place as it increases load on the parts you are bushing, so if they are marginal already you will make a worse problem than loose handling on corners!
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