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Discussion Starter #1
Took my 156 TS Sele to a local garage to have a new set of rear pads fitted. This they did, they also changed the oil and filter, rotated the wheels front to rear and straightened up the tracking. It is now set at 1Degree toe in as I always request (2 Degrees is the chart setting)

So rear wheels on front, front on rear, all directional, all correct. The garage checked the balance on the two going up front and one needed a single small weight to correct imbalance. All evenly worn treads

Now the car has developed a whir from the front, a kind of low pitched whirring low frequency vibration. This was not there before! There is no instability, car handles well, grips well, turns in well etc.

Most noticeable driving slowly, gets louder from about 5 mph, getting to a peak at about 60mph when wind noise and road roar take over.
There is a slight vibration through the steering wheel on sternish braking over about 75mph. The same brand of tyre used to be on the front, and didn't produce this much noise as normal road noise.

I was thinking possibly a knackered tyre casing or a buckled wheel which didn't notice while it was out back? Only other throught is that the tracking has been set up wrong!

I shall be going back to the garage asap, but any ideas before I go?


Ta

Andy
 

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Might be as you suspect. Try swapping that side wheels front to back and see if it makes any difference.
 

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The only other thing aside from a goosed tyre is a wheel bearing. The noise on just beginning to fail is not unlike a set of landy tyres with the volume all the way down.

Hope it's just a tyre, but if it's not that would be my suspect.
 
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Discussion Starter #4
Also check that the wheels are on properly and tight, just a thought but I once had a knocking noise when setting off in the van that turned into a loud vibating noise at speed. This was just after tyres fitted, so when I got home I checked the wheels and the drivers side was loose (just finger tight) it's a wonder it stayed on.
 

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AndyMac said:
So rear wheels on front, front on rear, all directional, all correct. The garage checked the balance on the two going up front and one needed a single small weight to correct imbalance. All evenly worn treads

Now the car has developed a whir from the front, a kind of low pitched whirring low frequency vibration. This was not there before! There is no instability, car handles well, grips well, turns in well etc.
Just along shot here, as it may not apply to 156s, but on 145s there's very little clearance between the front wheels & the calipers. If the balance weights aren't very carefully positioned they can foul on the caliper, setting up a low frequency vibration.
 
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Discussion Starter #6
I shall have a poke and see if the wheels are loose!

I think it may well be the tracking has been wrongly set as I noticed in a car park today that the noise is there at very low speeds, but disappears on full lock either way when the steering geometry changes!

Bum

Andy
 

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When mine was set to 2 I had this noise under braking. Just a slight touch on the pedal was enough to move the wheels to more toe out and the noise. Now I'm set to 1 the noise has gone.
My bet is that they have set you to 2+ in error. Swop the wheels back and prove the noise is still there.
 

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I still think it may just be the wear bias in the tyres producing the noise. It is quite possible you didn't notice it/ noise was better insulated whilst tyres were fitted to rear.:rolleyes:
 

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"It is now set at 1Degree toe in as I always request (2 Degrees is the chart setting)"
There seems to be some confusion here. It would be worth doing a search on tracking as this has been well discussed.
1 deg is about 5 times the maximum recommended setting. If the track is set to 1 deg toe in the tyres are being scrubbed on their outer edges and would certainly account for the noise.
From memory the latest recommended setting is zero+/-0.15deg.The best compromise seems to be zero to a touch(1mm max) toe OUT.
 
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Discussion Starter #10
The chart on the mechanics wall says set to 2 degrees. My last set of front tyres had suffered very minor scrubbing on the outside front tyres as in they had 3mm of tread on the outside edges and 4mm on the rest. The track was set at 2 degrees. I asked to bring it back to straight. The chap suggested half way between the two. It has been set at this by the same garage on any occasion when the front end has been in bits, or whenever I've had tyres changed, or puncture repaired. Always been fine up until now! If the chart measures in 0.s of adegree, that'll be the measure that my garage refer to as degrees!

Andy
 

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Looks like there is some confusion with the units. 2deg of toe in is 13mm of toe in which is obviously nonsense.I guess the wall chart is reading mm and refers to toe OUT rather than toe IN. There have been changes on recommended toe for the 156 for standard and sport suspension. The sport setting of 0 +/- 1mm(0 +/-0.15deg) is the one which gives a good compromise on handling and tyre wear.
Generally a bias of 0 to 1mm toe OUT is preferable to 0 to1mm toe IN.
 

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As the 156 generally has a tendancy to wear the inner shoulders of the front tyres, I would suggest that a parallel to 1 mm toe-in setting was preferable to toe-out. This also helps to sharpen the steering response slightly.

1mm=roughly 9 min=1/6 degree (60 minutes in a degree) for a 16" rim.
The conversion between toe distance (mm) varies slightly due to rim size whereas the angular value (degrees and minutes) is a constant.
 
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