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

[Patrick]

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.

[stevejgreen]

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

A slightly stronger grade of stainless compared with of 304, the commonest stainless, is 302. Same corrosion resistance but a slightly higher carbon content.

[copperleaves11]

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

Why stainless?

[wiggiesworld]

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

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.

[Patrick]

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

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

[copperleaves11]

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

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

[Patrick]

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

Thank you that’s really helpful info

[Patrick]

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

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.

[leadfoot]

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

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.

[David]

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

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!

[Tony Stott]

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

When I worked as a technician in a high school technology section we used to harden homemade silver steel tooling by heating to cherry red then dropping the piece into old/black engine oil, hardened the surface a treat

[meverett]

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

When I was at school (many years ago) I remember in metalwork making tools like a tap and die tool that we hardened by heating to cherry red then dipping in whales oil. I still have them in the garage 45 years later. Don’t think whales oil is available any more though.

[Tony Stott]

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

We ran out of caesenitt a particularly noxious powder used for hardening. an ex bmc apprentice, engineer eventually teacher came up with the engine oil solution, he'd previously used it in the engine development department at longbridge!

[Patrick]

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

Thanks for offer of making the parts, I was hoping to be done for the weekend to attend Stoneleigh with the Sportster.

I have the equipment to heat the metal up and old engine oil to harden the material, so I happy to give it ago.

Regarding the bushes, the powerflex purple ones Marlin started to supply/recommend for the Sportster around 2006/2007. I do wonder if the rally design ones are a bit harder which may have contributed to the issue. Originally I got some standard rubber bushes with the kit, but after an issue that required me to send wishbone parts back to them I didn’t get rubber bushes and was told the don’t supply them anymore.

[leadfoot]

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

Hi Patrick, no problem. Offer is still there if you need it.
Don't forget to temper the silver steel after heat treatment to add some toughness back in.
When quenching in oil, make sure you dip the part completely to minimise flames and vertically to maintain a good level of straightness in the parts. Swirl the heated parts in the oil to disperse the vapour jacket.
Good luck.