Noisy or creaking front suspension
Lowering the front suspension (In the modifications page)
Front camber angle on lowered Scimitars
This is another fault that has cropped up a couple of times recently. A local Scimitar owner came to see me with a strange creak coming from one side of the car when cornering or driving, and it could be heard by bouncing the wing on that side of the car. He was worried that a spring had broken.
With two of us, one could bounce and the other could listen, but I didn't see any sign of a broken spring. Nothing else seemed to be loose or broken. We used a different method to produce the noise which allowed us to look at the front suspension as the noise occurred.
The car was jacked up and supported on an axle stand, and the trolley jack placed under the spring pan and used to push the lower suspension upwards. The creaking noise was found to occur most readily when the trolley jack was lowered. Watching the suspension as it came back down showed that it was moving jerkily instead of smoothly, and the loud noises coincided with each small movement.
The trunnion bolt and sleeves were binding, making the noise as the forces on them overcame the resistance and they moved a little.
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If your front tyres are wearing too quickly on the inside edges, it is probably because someone has lowered the car, but not restored the correct camber angle. Before rushing out and checking the camber settings, just get the tracking tested, because too much toe-out will also tend to scrub the tyres on the inner edge, but to be honest, the snatch on the steering when you turn the wheel from the straight ahead position will normally tell you that the tracking is wrong long before the tyres start to wear.
The Scimitar does not need much negative camber. There is no need to make the car look like modern touring cars because the double wishbone geometry controls the wheel angle better than the Macpherson strut geometry on most modern cars.
When people lower the front of the scimitar by inverting and swapping the front wishbones from side to side, or putting spacers between the damper support plate and lower wishbone, or by fitting adjustable platform shock absorbers, they inadvertently introduce negative camber. The more the car is lowered, the greater the negative camber that is introduced. It is important to add shims behind the upper fulcrum to remove this negative camber.
The shims behind the upper fulcrum perform two purposes, controlling caster angle, and camber angle. Fit extra shims in equal numbers to the front and back of the upper fulcrum to reduce negative camber. If you put more shims behind the front bolts than behind the rear bolts the caster angle will increase, which will make the steering feel heavier.
It is probably better to have a little too much negative camber than to have positive camber.
After resetting the camber angle, you will need to reset the tracking.
As an alternative to adding shims to the upper fulcrum, you might consider raising the car back up a little, particularly if you often drive down bumpy roads or have to cross speed humps. Scimitar exhausts are particularly fragile and exposed
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For the third time this year (2001), someone has rung up and ordered parts from me to repair a Scimitar after the lower trunnion detached itself from the vertical link. Two of these happened at slow speed, one at "normal dual carriageway speed".
I had never heard of this type of failure until this year, and had asked Chris Lloyd, Mike Thompson, and Terry Cox what they thought was the reason. They all agreed that lack of grease was the primary cause. I grease the front suspension on my cars every 3000 miles, so I thought I was safe.
After the third call, I started thinking about why there should be a lack of grease in the first place. Two of the cars involved only did low mileage according to their owners, and one had been MoT'ed barely 2 months before, without any hint of pending trouble, and they hardly did any mileage with the car.
I had a look at my two working Scimitars, and as a result, I have confined AOX to barracks until the left trunnion has been replaced. "But it was MoT'ed in May, and I've only done 1500 miles since then"
Oh yes indeed. Read on
When I did this to AOX, I started on the right-hand side of the car instead. The steering felt a bit heavy when I was turning the wheel. When I came to grease the left-hand side, I found that grease was squirting from the metal disc pressed into the bottom of the trunnion. A closer inspection showed that this disc was no longer square in the recess, but was canting out. I tapped it back in and tried again, but found the grease pressure was popping it out again.
A further inspection of the trunnion showed movement in it that would not pass the MoT test. However, it had not had that movement a few months ago when it passed the test.
The trunnion itself is about 5 years old. It was the first thing I had to fix on AOX to get it through it's first MoT. It was a genuine bronze trunnion bought from Scimpart. As I have said, I greased the front suspension every 3000 miles. I checked it scrupulously before the MoT earlier this year, and know it was not worn then.
The lesson I have learned from this is that I will have to grease the front suspension on a monthly basis, (which on my regular SE5A will be 3000 miles anyway).
The other sobering thought is that the cost of replacing the front trunnion, bolt, and bushes, will be about £40. The cost of repairing the front suspension after a trunnion failure seems to vary between £250 for a low-speed incident, to over £700 for a high-speed one. And of course, there's the oncoming traffic which is not expecting you to suddenly swerve into their half of the road to consider as well.
I'll describe the tricks and pains of trunnion replacement in another FAQ post. (probably called Changing a front trunnion ).
In the case of AOX, both Charlie and I are scrupulous checkers. I went up to early MoT's three times with what I felt was a perfect car, only to have Charlie point out movement in a trunnion. It took me a while to learn how to find it. The problem is, when you're kneeling on the ground, you can't easily put leverage on the lower suspension and feel the trunnion. But I have now developed a method.
The key to this is gently . I was originally heaving the car up, which meant that although I could easily detect major wear, the effort of lifting the car from a kneeling position with only one hand meant that I was missing the very slight feel of a trunnion or trunnion bush that had just begun to wear. You only need to lever upwards enough to cause any slack to be taken up, any further leverage which starts to compress the springs is happening long after the slack movement has occurred.
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Slacken the wheel nuts, jack the car up and support on axle stands under each side of the chassis close to the engine mount positions, and remove the road wheel.
Undo and remove the brake pipe from the caliper to the flexible hose. ( Note, if you have braided Aeroquip hoses, do not use the clamping tools supposed to seal the brake hose to stop fluid running out, you cannot inspect the inner pipe afterwards to ensure that you didn't cause damage to it)
Remove the brake caliper, and the hub and disc complete. You can hang the dust shield complete with flexible hose carefully out of the way, or you can leave it dangling so that you break it later, your choice
Undo the steering lock-stop bolt. Remove the split pin and undo the slotted nut from the trunnion bolt. Try to get the bolt turning and see if you can persuade it to start moving out from the assembly. If you can, you've won the major battle, and everything else is easy. Go to step 6) below.
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