Friday 24 February 2012

MOT Pass but Click click click still there

The GT6 now has a full MOT again, unfortunately it had gone past the 10 working days now strictly enforced by the VOSA for re-tests and had to have a full test again. To their credit Moonface where I had it done did say they tried to buck the system and put it through as a re-test but now it's all computerised and locked down by VOSA  they were unable to get around a full test on the system.  Anyway all passed now that's the main thing. By the way has anyone else had one of the new style MOT certificates? They are just printed on normal paper now and are black and white, on the minus side dead easy to forge but then it's the VOSA database records that matter nowadays and you can check validity on line so less of an issue, on the plus side if you are a buyer, it lists advisories picked up in the test.

On the way to the MOT I was a bit peed off as the clicking from the rear axle was still there, I thought I had identified it as a wheel balance weight hitting the wishbone bush shroud but having removed the weight it was still there. It was however only really apparent on right hand bends...

Anyway I investigated again and sure enough it is related to the outer wishbone bush shroud but what it was actually fouling on is the inside of the wheel rim. I'm surprised just how much run out there is on the inside of the rim on my Cosmic alloys, I guess it doesn't matter as long as the outside of the rim is true which it is but the run out was causing the wheel to foul very slightly at one point per revolution but only when the suspension is compressed under load going around a bend. This seems a bit strange as I can't work out how the relationship between the wheel rim and the outer wishbone bush should change, I can only assume that there is a slight amount of flex under load. Under no load the wheel didn't foul however the gap was extremely small, probably less than 10 thou.

I decided to swap rear wheels in case this was the issue, both had been off the car last week and they may have swapped sides. To my surprise I found that the run out on the other wheel was worse and it fouled at the same point even under no load. Strange there is no issue the other side although having checked clearance is again minimal.

So I was faced with 2 choices, firstly to add a wheel spacer, something I'm reluctant to do without longer wheel studs, or secondly to dress back the wishbone bush shroud which is what I've done. I may well get some longer studs and spacers of about 10mm later but for the time being all is well again. Picture below shows where the issue was and if you look carefully you'll see that the wishbone bush shroud has been flattened slightly to avoid fouling the wheel rim.

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