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Warning about the use of aftermarket bushes in the front suspension
After the euphoria of (nearly) passing the SVA I gave the car a once over last night and was a little horrified as to what I found.
On one side, the front nut holding the rod thru' the top wishbone had started to pull through the bush (complete with washer). Closer examination revealed why. The standard M10 washer is not much bigger than the metal sleeve in the bush. The force of doing the lock-up brake test had put sufficient load on the front wishbone arm that it temporarily moved forward (distorted) taking the polythene bush with it drawing the nut into the bush. The problem is that the polythene bushes are an easy fit (unlike the rubber Fiesta ones) and offer little lateral resistance.
As a temporary solution I am going to fit some large machine washers (front and back) which should stop it happening again. As a long term solution I am going back to the Fiesta bushes (assuming I can locate some). I suggest anyone else running these bushes checks them carefully.
Robin
PS - It's not a problem on the lower wishbones because the bushes are gripped on both sides by the mounting brackets.
Now that's something useful the SVA man could have spotted instead of worrying about inconsequential semi-sharp edges!
I dug out a picture of a Marlin built car taken at Donnington 2006.
You can just see a washer but it's not very large? I guess you need something the same diameter of the bush? I've used those large 'repair' washers on my exhaust mounting but they seem to be quite soft and deform easily, so maybe a couple of washers each end?
I had intended changing my rubber bushes as they are very soft, leading to an alarming amount of movement when braking.
It's never a dull moment with these cars and you've only done 50 miles!!
P.S. notice the shock absorber mounted the wrong way up.........one side effect of this is that the spring seat adjuster ring is shielded by the top suspension wishbone.
Now that's something useful the SVA man could have spotted instead of worrying about inconsequential semi-sharp edges!
I dug out a picture of a Marlin built car taken at Donnington 2006.
You can just see a washer but it's not very large? I guess you need something the same diameter of the bush? I've used those large 'repair' washers on my exhaust mounting but they seem to be quite soft and deform easily, so maybe a couple of washers each end?
I had intended changing my rubber bushes as they are very soft, leading to an alarming amount of movement when braking.
It's never a dull moment with these cars and you've only done 50 miles!!
P.S. notice the shock absorber mounted the wrong way up.........one side effect of this is that the spring seat adjuster ring is shielded by the top suspension wishbone.
Interesting....
So that accounts for why Marlin mount their shox the wrong way up. I think I would rather have mine the right way up and with a cover over the lower plate...
I recon that that car will/would have had the same problem with the bushes. With a washer that size there is nothing to stop the upper arm moving forward the same as mine. What it needs is a thick washer the same diameter as the bush. I can't actually do that....
Why?
Cause one of the failure points was the sharp edge of the bush! They asked me to put a radius on it of 2.5mm! They checked the "stiffness" with some sort of fancy meter and reckoned it must be radiused!!!!!
I recon that that car will/would have had the same problem with the bushes. With a washer that size there is nothing to stop the upper arm moving forward the same as mine. What it needs is a thick washer the same diameter as the bush. I can't actually do that....
Why?
Cause one of the failure points was the sharp edge of the bush! They asked me to put a radius on it of 2.5mm! They checked the "stiffness" with some sort of fancy meter and reckoned it must be radiused!!!!!
How about cutting your own washer, the same diameter as the bush from heavy (thick) plate and then put a radius on that? The bush will be completely behind the radiused 'washer'
Not entirely sure how you'd do it though - A lathe? Bar stock the same diameter as the bush, radius the front and then part it from the bar so it's about 4mm thick?
Use a hole cutter to get the approx size, then put a bolt in the disk you've through the centre hole. Mount this in a drill then use either a file, or maybe even an angle grinder to trim down the piece to the right size and put a radius on it - uses the same principals as you would on a lathe only a bit cruder
How about cutting your own washer, the same diameter as the bush from heavy (thick) plate and then put a radius on that? The bush will be completely behind the radiused 'washer'
I'd thought about that. Seemed to be a good idea.
But the problem is that the bar that is threaded at both ends isn't long enough. There has to be at least two turns of the thread protruding through the nylock nut to satisfy the SVA. (They checked ALL mine pulling of every nut cover).
I think I will have to put a radius on the bush as they suggested - and then look for a better solution after.
Keep up the good idea's though guys! As I fix each problem I will post up a picture of before and after.
The only other thing I can come up with is a "super size" nut cover - something that covers the nut and the offending edge of the bush. Dunno what would suit though... Google ahoy!
I can buy 40mm diameter stainless steel repair washers with an M8 centre hole from my local stainless supplier, would they not be big enough to solve the problem, they are the thickness of a conventional washer, around 1mm.
The only other thing I can come up with is a "super size" nut cover - something that covers the nut and the offending edge of the bush. Dunno what would suit though... Google ahoy!
If anybody has access to a vac form machine it would be no problem to make something like that.
But the problem is that the bar that is threaded at both ends isn't long enough. There has to be at least two turns of the thread protruding through the nylock nut to satisfy the SVA.
Buy a longer bolt from your local fasteners shop? just measure the one you have and add the thickness of the two thicker washers (say 6mm each - 12mm total extention) so if they are 75mm get 90mm Grade 8.8 or higher bolts
The only other thing I can come up with is a "super size" nut cover - something that covers the nut and the offending edge of the bush. Dunno what would suit though... Google ahoy!
That would probably be the easiest solution!
cabrioman wrote:
I can buy 40mm diameter stainless steel repair washers with an M8 centre hole from my local stainless supplier, would they not be big enough to solve the problem, they are the thickness of a conventional washer, around 1mm. John
I have some like that that I am using as a temporary fix. The problem is that 1mm is probably not thick enough when you consider the sort of forces you get from an emergency stop. I shall probably end up making some myself out of some 2mm steel.
chrislandy wrote:
Buy a longer bolt from your local fasteners shop? just measure the one you have and add the thickness of the two thicker washers (say 6mm each - 12mm total extention) so if they are 75mm get 90mm Grade 8.8 or higher bolts
Unfortunately it is a special made by Marlin. About 200mm long and threaded both ends. I could possibly get a couple made up by a local machine shop. Hmmm....
Unfortunately it is a special made by Marlin. About 200mm long and threaded both ends. I could possibly get a couple made up by a local machine shop. Hmmm....
Thanks for all your replies guys
Robin
I had one of mine re-made as one had awfully badly cut threads. (It was a favour and made in a military suppliers workshop so I can't really ask for anymore) I've searched for long bolts at shows but haven't found any yet!
I saw some on ebay but they were stainless so not sure if strong enough?
A ball joint dust cover - leave the nut cover on, and then stretch it over the bush / washer / nut. You may have to enlarge the hole in the middle though.
I've invested in some new bushes for my top front suspension wishbones. These are Superflex polyrethane and seem to be really well made and came with some lubricant and stainless steel thick tubes. They look blue in the picture but they are actually a dark purpley colour.
They seem much harder plastic than the Polysport yellow ones I bought for the lower wishbones.
It's a case of you get what you pay for. I can see that the part that fits in the eye is tapered and fluted. They look vastly superior to the ones I bought and I guess they will work as intended with the bush flexing to absorb the suspension movement rather than the sleeve rotating.
Let us know how you get on! If they work well I think I will also change to these. (Well I haven't spent any money on the car for at least two weeks....)
It's a case of you get what you pay for. I can see that the part that fits in the eye is tapered and fluted. They look vastly superior to the ones I bought and I guess they will work as intended with the bush flexing to absorb the suspension movement rather than the sleeve rotating.
Let us know how you get on! If they work well I think I will also change to these. (Well I haven't spent any money on the car for at least two weeks....)
Robin
I think they will still rotate around the spindle as they are quite hard and hence the lubricant but definately better quality than the Polysport ones I bought from Rally Design. I got them from a place called JD Motorsport and they cost £44 for 4 bushes inc vat and delivery, so not too expensive.
Just need to find the time to fit them now........
