Powerflex Caster Bushing Bolt Won't Stay Tight
03-29-2018, 12:13 AM
#1
Burning Brakes
Thread Starter
Powerflex Caster Bushing Bolt Won't Stay Tight
Hi, 86 951 with Powerflex caster A arm bushings and the bolt on the rear won't stay tight. It comes loose immediately from any drive. Apparently the movement of the A arm simply loosens the nut. I've torqued it to the specified 63 ft. lbs. I'm not sure if the bushing is supposed to pivot against the inner metal race or if it's supposed to actually supposed to twist the bushing. Anyone using these bushings or a similar poly bushing with an internal metal sleeve?
https://powerflexusa.com/porsche944s...f57-203-1.aspx
https://powerflexusa.com/porsche944s...f57-203-1.aspx
03-29-2018, 02:08 AM
#2
Nordschleife Master
The picture of the caster block bushing in that link is not the correct bushing for your arms. I know it’s labelled for a 951 but it’s a totally different shape, it’s supposed to be “U” shaped not “O” shaped and would certainly rotate and loosen if fitted instead of the correct one. Btw, poly bushings don’t twist like rubber, they rotate in the metal sleeve, that’s why they need to be lubricated at all times and it’s also the reason they squeak sometimes.
03-29-2018, 03:02 AM
#3
Burning Brakes
Thread Starter
The picture of the caster block bushing in that link is not the correct bushing for your arms. I know it’s labelled for a 951 but it’s a totally different shape, it’s supposed to be “U” shaped not “O” shaped and would certainly rotate and loosen if fitted instead of the correct one. Btw, poly bushings don’t twist like rubber, they rotate in the metal sleeve, that’s why they need to be lubricated at all times and it’s also the reason they squeak sometimes.
03-29-2018, 10:50 AM
#5
Nordschleife Master
968 caster mounts ok, I wasn’t aware you could swap those rubber bushings out or that you could even buy them separately from the mount. I’m also uncertain which bolts you are referring to, there is only one bolt which I am aware of and it’s a special eccentric type used for adjustment. Is it the nuts on the eccentric bolt which are loosening?
As for lubrication and poly bushes, I’ve heard of ones that last a long time without the owner ever reapplying lube and I’ve also heard of ones that squeak as soon as it rains and the lube washes out. Personally I prefer the characteristics and lack of maintenance of rubber. You mention Elephant Racing, were you aware that their 968 caster mounts are available with a harder rubber compound they call “sport hardness”, that may be a good solution if poly isn’t working and spherical is just too harsh.
As for lubrication and poly bushes, I’ve heard of ones that last a long time without the owner ever reapplying lube and I’ve also heard of ones that squeak as soon as it rains and the lube washes out. Personally I prefer the characteristics and lack of maintenance of rubber. You mention Elephant Racing, were you aware that their 968 caster mounts are available with a harder rubber compound they call “sport hardness”, that may be a good solution if poly isn’t working and spherical is just too harsh.
03-29-2018, 04:52 PM
#6
Burning Brakes
Thread Starter
There are actually two bolts on the eccentric, one towards the front that is against the control arm and one towards the back against the bushing, both 19mm. The one I'm having trouble with is the rear against the bushing which makes sense as it's right where the arm pivots against the bushing.
I'm aware of the raging arguments surrounding poly vs. rubber but I have never been unhappy when losing a rubber mount for a poly, this on all four of my cars. And Powerflex is a much higher quality than other suppliers and they have an amazing selection for older cars which is what I have. And they even have different hardnesses too.
I honestly don't think any rubber should ever be used on a suspension but spherical is just crazy expensive. However, until a cheap set of spherical joints come up, poly is the next best thing.
Time to relube....
I'm aware of the raging arguments surrounding poly vs. rubber but I have never been unhappy when losing a rubber mount for a poly, this on all four of my cars. And Powerflex is a much higher quality than other suppliers and they have an amazing selection for older cars which is what I have. And they even have different hardnesses too.
I honestly don't think any rubber should ever be used on a suspension but spherical is just crazy expensive. However, until a cheap set of spherical joints come up, poly is the next best thing.
Time to relube....
03-29-2018, 09:26 PM
#7
Nordschleife Master
Im still totally confused about which “bolts” you are referring to. I thought I was losing my memory so went out to my garage and picked up a spare control arm to check. There is only one bolt and it’s an eccentric type with two nuts on either end. One end attaches to the rear of the control arm and the other to the caster bush. You are either writing “bolt” when you mean “nut” or you have some weird set-up back there. Here’s a picture of my reference 951 control arm with original caster bush, the only difference should be yours will have a 968 caster block instead, everything else should be the same including the two “nuts” (in yellow) at the ends of the single eccentric bolt.
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03-30-2018, 03:45 AM
#9
Drifting
Did you tighten the nut(s) with a load on the control arm or was the car in the air? Because the stock unit gets torqued while the car is on the ground and the control arms are loaded with the cars wieght. If you torque the lower control arm down while it's in the air you will have the problem your running into. Could you show a photo? I have many stock control arms and one elephant racing spherical rear mount setup on my turbo. Now with the spherical mounts they don't need to be torqued down with a load on the control arms like the factory units because they are designed to move with as little resistance as possible so the springs and struts respond better to the road. If you try to move a factory rear mount on a factory lower control arm it doesn't move. Hence why it needs to be torqued with a load on the lower control arm.
03-30-2018, 02:44 PM
#10
Burning Brakes
Thread Starter
Hmmmm, tightened them with the wheel in the air but I don't have a lift so not sure I have any options. I have noticed that the right side comes loose sooner as when the wheel goes up, it naturally loosens the nut so I think you are on to something. However, I also think that either way, the nut will loosen. And in theory, the bushing should move freely enough that the nut isn't subjected to enough torque to come loose.
I'm going to take the caster mount off, inspect them for damage and lubricate them.
Oh, I used the copper grease that came with the bushings when I initially installed them but copper grease doesn't seem to last very long. I also have some silicone grease which I've heard lasts much longer; does anyone have experience with this grease?
I'm going to take the caster mount off, inspect them for damage and lubricate them.
Oh, I used the copper grease that came with the bushings when I initially installed them but copper grease doesn't seem to last very long. I also have some silicone grease which I've heard lasts much longer; does anyone have experience with this grease?
04-01-2018, 01:04 PM
#11
Instructor
In place of a lift, you could also try raising the car and putting some blocks under the mounted tire assemblies and lowering down on them to replicate normal position. This would leave you with sufficient room to access the bolts from underneath. As always, use jack stands for safety while under the car.
04-03-2018, 01:26 AM
#12
Burning Brakes
Thread Starter
Did you tighten the nut(s) with a load on the control arm or was the car in the air? Because the stock unit gets torqued while the car is on the ground and the control arms are loaded with the cars wieght. If you torque the lower control arm down while it's in the air you will have the problem your running into. Could you show a photo? I have many stock control arms and one elephant racing spherical rear mount setup on my turbo. Now with the spherical mounts they don't need to be torqued down with a load on the control arms like the factory units because they are designed to move with as little resistance as possible so the springs and struts respond better to the road. If you try to move a factory rear mount on a factory lower control arm it doesn't move. Hence why it needs to be torqued with a load on the lower control arm.
First, I disassembled and inspected the bushings which were in fine condition but completely dry with no lube. So I relubed them with silicone grease and reinstalled. However, I had read that with poly or spherical mounts, you should tighten and torque the nuts to the eccentric bolt before bolting to the car body. And once the bushing is lubed, it will pivot freely with the nuts torqued as a poly mount does not twist the bushing as rubber does but instead slides/spins against the inner metal sleeve. As a result, these mounts are sensitive to proper lubrication as once the lube disappears, the mount seizes up and twists the nut loose.
Anyway, it seems all good now with the nuts staying tight and the car feels much better now that I've got that mount secure and also that I set my alignment closer to proper settings. I say 'proper' as I do my own alignment with a Fastrax camber/caster gauge and a different gauge for toe. I've found toe is the more sensitive setting to gain proper feel, with a slightly more toe out for much nicer turn in and sensitivity. I found that I preferred a very slight toe out but in actuality basically zero toe. Slight toe in, which is factory correct, felt a bit vague and delayed to me. I should also say that I have manual steering and 225/45 17 front tires so car is not stock. And I have camber a bit more negative than OE at about -1.5 to -2.0. Camber is the hardest setting to gauge accurately as I have to compensate for the unlevel surface where camber is measured. Furthermore, this is nearly impossible even on smooth concrete; nothing is ever level in life!
I might back off the camber a bit, more towards positive or around -1.0. What do you guys prefer for street camber or should I say how far negative can I have it before tire wear becomes a problem?
Oh, and caster is +3.5 to 4. Might go a little less here too and see what happens as I think in theory it should make the steering lighter and more direct.
And thanks to all for the help in getting this figured out. I like the poly here but it's obviously very important to keep them lubed which may require once or twice a year taking them off and relubing them. Hopefully this silicone grease lasts a little longer; it's very sticky and supposed to resist water and heat but we'll see.