steering shake & bent track rod ???

[RESOLVIWOLF]

The latest in my front geometry saga:

 

Well after experiencing some inappropriate steering vibration and odd front tyre wear/behaviour (excessive and all on nearside of each front tyre, and lots of strange understeer at Cadwell) i got the car checked out.

 

Had new set of tyres balanced & fitted all round. Turns out the tracking was slightly out as well which was also fixed. But also the track rod is bent and this is visible if you turn it with a spanner (nearside). Didn't have time to fix this. Lord knows how it happened, i have never hit anything so maybe it was like it when i picked the car up but i find this hard to beleive (surely Caterham check all these things ?).

 

Drove the car home and the steering is still shaking. Its very strange becase it happens in waves, like a cycle. Basically above say 60mph on the Mway, the steering will be smooth (how you'd expect it to be) for about 2 seconds, then the shaking in the wheel starts to build and gets stronger and then after another 2 seconds has died down and the steering feels ok again. This endlessley repeats itself. The 2 second interval thing seems to remain the same regardless of speed.

 

The shaking is definitely abnormal & not a product of a bumpy road or my own paranoia. How do I now know this ? Well simple, during the 2 second phase when it feels smooth and "unshaky" its so obvious that this is how its supposed to be all the time.

 

My question is, could the bent track rod be causing this ? Or maybe something else is bent or not straight on the car ? Bear in mind that tracking and wheel balance are all now 100%.

 

 

hope you can help

 

 

Rich

[StewartG]

The fact that the nearside, left corner, of BOTH front tyres is scuffed suggests the front wheels are trying to turns the car right all the time and something else on the chassis is keeping it running straight. The chassis and the front wheels are fighting for directional control and the cyclic vibration could be some sort of resonance resulting from this conflict. I'm not too sure about that bit, perhaps someone more technically minded can elaborate. I don't think the bent track rod is too much of a problem by itself but the concern is how it got bent. The only thing that springs to mind is accident damage which rather ties in with the odd tyre wear. I'm sure Ratrace will sort you out for chassis distortion with a four wheel alignment check.

[Peter Carmichael]

Check the wheel bearings. No tracking changes will be accurate unless these are correctly adjusted. I'll have a think and compose a longer answer tomorrow...

 

Peterid=teal>

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[ashaughnessy]

Aren't the new steering racks (i.e the "quick racks" as they are known) supposed to be susceptible to causing shakes? I'm sure I have read references to this phenomenon on tech-talk in the past. Also, I noticed similar vibrations when I picked my car up after it had had a quick rack fitted to replace the old one. Didn't get a 2 second cycle, but it did come and go for no reason.

Anthony

[J.R.]

Check and adjust the steering rack damper

[TonyR]

Rich,

 

Did you have a small excursion onto the grass at Cadwell?

If the was steering ok when you drove up to Cadwell may be the rack got bent on the circuit.

 

As suggested check for play in the rack, wheel bearings etc.

 

 

 

 

[RESOLVIWOLF]

Tony,

 

the steering was shaking before cadwell

and the grass excursion was nothing too violent and was the last lap of the day way after the strange tyre wear had set it

[Simos]

Bearings sound like a good start, check the rears also.

 

A long shot but is de-dion tube bent ? Had lots of crabwise driving from mine when it went. I would expect you to have scrubbed rears as well of course. You said strange understeer, was it one sided i.e. different turn in through the hall bends or Coppice.Chris curve ?

 

Once adjusted the track rod won't make any difference to the tracking, it could do a figure eight on the way from rack to rim as long as it doesn't flex.