Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: pauls on 29 January 2017, 19:42:09
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Dont know how else to explain it. When its wet the backend always feels a lot less planted. It feels like it wants to let go also seems to be a bit more jumpy. Any ideas please.
car history 3.2 auto back end has police springs with b4 shocks also doughnuts are poly,ed tyres are dunlop maxx rts 235/40/18. Fronts are police springs standard shocks poly wishbones and 235/40/18 dunlop maxx rt2
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Possibly failed diffmounts or the poly donuts need refitting... both easy enough to check, weather permitting :y
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Omegas are twitchy, end of.
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Dont know how else to explain it. When its wet the backend always feels a lot less planted. It feels like it wants to let go also seems to be a bit more jumpy. Any ideas please.
car history 3.2 auto back end has police springs with b4 shocks also doughnuts are poly,ed tyres are dunlop maxx rts 235/40/18. Fronts are police springs standard shocks poly wishbones and 235/40/18 dunlop maxx rt2
It's RWD... the springs are over stiff unless you carry 250kg of clobber all the time, the bilstiens are stiff as a wedding prick, the polybushes have no give, dunlop aren't the stickiest of tyres and you have a limited slip diff presumably... Little wonder really.
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Dont know how else to explain it. When its wet the backend always feels a lot less planted. It feels like it wants to let go also seems to be a bit more jumpy. Any ideas please.
car history 3.2 auto back end has police springs with b4 shocks also doughnuts are poly,ed tyres are dunlop maxx rts 235/40/18. Fronts are police springs standard shocks poly wishbones and 235/40/18 dunlop maxx rt2
It's RWD... the springs are over stiff unless you carry 250kg of clobber all the time, the bilstiens are stiff as a wedding prick, the polybushes have no give, dunlop aren't the stickiest of tyres and you have a limited slip diff presumably... Little wonder really.
Car is otherwise standard Elite. Springs were fitted to replace overly soft Elite ones and to lift the back end slightly, as its arse was on the floor. Shocks were replaced as were leaking. No lsd either.
Car drove fine with the above set up, and from my experience with plod springs/polybushes/rigid diff mounts on my old estate is anything to go by, twitchy isn't a word I would associate with the handling...
Suspect failed diff mount...
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What's more surprising is that the useless soup heater mushbox ar35 is able to transfer enough torque to the rear wheels to achieve twichty-ness. :P
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I can't say the rear end of mine has ever been anything other than completely planted so yes, I'd say something's amiss. Probably one or other of the bushes as the rest has been eliminated.
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http://www.omegaowners.com/forum/index.php?topic=136126.msg1746023#msg1746023
^That's how I solved my rear subframe rear busing issue. No wobbling after those also changed to polys :y
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Seeing as the car is IRS then I fail to see how the diff mount would add to any rigidity in the back end. My first look (especially if the car was running low for any length of time would be the subframe mounts or the trailing arm bushes, both add (or not) locational strength to the rear end.
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How worn are the rear tyres? Dunlop RT's grip levels fall off a cliff when worn (about 3mm)
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Seeing as the car is IRS then I fail to see how the diff mount would add to any rigidity in the back end. My first look (especially if the car was running low for any length of time would be the subframe mounts or the trailing arm bushes, both add (or not) locational strength to the rear end.
Unbolt one, either will do, take the car for a spirited drive with some roundabouts thrown in for good measure and report back...
... I'll say "I told you so" now, just to.get it out of the way ;)
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How worn are the rear tyres? Dunlop RT's grip levels fall off a cliff when worn (about 3mm)
Not sure but i can spin them up very easy in the damp. Will have to check
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Stupid question I know but I take it your TC is working.
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Stupid question I know but I take it your TC is working.
Yes it works fine
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How worn are the rear tyres? Dunlop RT's grip levels fall off a cliff when worn (about 3mm)
Not sure but i can spin them up very easy in the damp. Will have to check
My experience of RT2's is that they lack the grip of RT's in the wet. Appreciate you have RT's on the back. As TB asks, how many MM on them? If they're less than 4mm they become a totally different tyre....
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Seeing as the car is IRS then I fail to see how the diff mount would add to any rigidity in the back end. My first look (especially if the car was running low for any length of time would be the subframe mounts or the trailing arm bushes, both add (or not) locational strength to the rear end.
The diff bushes locate the subframe too.
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Seeing as the car is IRS then I fail to see how the diff mount would add to any rigidity in the back end. My first look (especially if the car was running low for any length of time would be the subframe mounts or the trailing arm bushes, both add (or not) locational strength to the rear end.
The diff bushes locate the subframe too.
Technically, the diff is mounted to the subframe, the rear of which is supported by the 'diff' mounts...
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Seeing as the car is IRS then I fail to see how the diff mount would add to any rigidity in the back end. My first look (especially if the car was running low for any length of time would be the subframe mounts or the trailing arm bushes, both add (or not) locational strength to the rear end.
The diff bushes locate the subframe too.
Technically, the diff is mounted to the subframe, the rear of which is supported by the 'diff' mounts...
Yes, basically what I was trying to say, so the consequence of failure is more than just a diff floating around a bit more than normal.
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The amount of play at the wheels that an inch of movement just off the centreline can generate is quite impressive...
... providing you're not actually in the car when it manifests itself :o
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I have mentioned before that of all the Omegas I have owned and driven - I currently have six - just one has displayed a twitchy back end. I have jacked the back up, removed the wheels, heaved it this way and that, and could find nothing amiss. It is a 2000 2.5 petrol manual estate, 160000 miles, running well. What should I look for to explain its misbehaviour?
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With it overf the pit... remove each diff mount in turn, ie undo one unit, refit, repeat on other...
For the purposes of the exercise, the two bolts that hold the mount to the chassis are all that need undoing. If the bracket drops away, there be your problem :y
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i had the traction control kick in twice on sunday whilst driving in a straight line, no braking, on a dual carriageway about 60mph. it was through large amounts of fallen rain and i had to hold the steering wheel. i don't remember it before though, maybe it is my new tyres.
i once had a rover P6 also rear wheel drive. back end used to kick out if you floored it on slippery roads, you had to turn into the skid to keep straight.
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Rear shock absorbers are also worth a check if the back end is a bit wayward. :y
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With it overf the pit... remove each diff mount in turn, ie undo one unit, refit, repeat on other...
For the purposes of the exercise, the two bolts that hold the mount to the chassis are all that need undoing. If the bracket drops away, there be your problem :y
Which is exactly what happened to mine.
I've two more holes to drill and tap, and my repair jig is complete. That just leaves the rubber to remove from the bracket, and the polyurethane to arrive and I'll be able to make the repair.
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With it overf the pit... remove each diff mount in turn, ie undo one unit, refit, repeat on other...
For the purposes of the exercise, the two bolts that hold the mount to the chassis are all that need undoing. If the bracket drops away, there be your problem :y
Thanks DG. I think these are the mounts you refer to, I removed them one at a time, but was dismayed to find them quite firm. I can see that had they been loose when unbolted that would cause my fault.Strictly speaking these are rear sub frame rear mountings, the front two are just ahead of the rear wheel arches. The diff is mounted entirely on the rear sub frame. I'm sure you all know this, but I did not. Pics follow.
https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1 (https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1)
https://www.dropbox.com/s/b6fqvz585ekuqde/DIFF%20MOUNTING%20LOOSE25%25.jpg?dl=1 (https://www.dropbox.com/s/b6fqvz585ekuqde/DIFF%20MOUNTING%20LOOSE25%25.jpg?dl=1)
https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1 (https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1)
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Apologies, no pics, will try again.
(https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1)
(https://www.dropbox.com/s/b6fqvz585ekuqde/DIFF%20MOUNTING%20LOOSE25%25.jpg?dl=1)
(https://www.dropbox.com/s/qgg4sxr6cf40mpt/REAR%20SUB%20FRAME%20SHOWING%20MOUNTS.jpg?dl=1)
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Woops. Top pic shows rear sub frame right hand side, with front mount bottom centre and rear mounting top right
Second pic shows LH rear sub frame mount unbolted from body and bolt supporting diff just ahead of it
Third pic is same as first; should have shown diff rear mounting, again to rear sub frame. Here it is.
(https://www.dropbox.com/s/5ic5ftmff6zx2bg/DIFF%20FRONT%20MOUNT.jpg?dl=1)
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Further correction. Last pic shows diff FRONT mounting, via a bracket, to a single bolt on the rear sub frame.
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i don't remember it before though, maybe it is my new tyres.
Are they shit tyres?
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i don't remember it before though, maybe it is my new tyres.
Are they shit tyres?
http://www.mytyres.co.uk/rshop/Tyres/tristar/Ecopower-4S/235-45-R17-97W-XL/R-279995 c rated in the wet
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i don't remember it before though, maybe it is my new tyres.
Are they shit tyres?
Yes, Budget tyres, Viking Windforce 205/65R15s on steel rims, about 5mm tread depth left. All my cars are on cheap tyres and always have been.
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Possibly failed diffmounts or the poly donuts need refitting... both easy enough to check, weather permitting :y
Reading through this thread again it is clear that Doctor Gollum and others have long known the problems of Omega rea r suspension, while I, Magwheels and others did not. I understand from earlier posts and Mandula's and Nick W's endeavours that 'diff' mounts are no longer available from Vauxhall. Luckily mine are OK.
I presume 'poly donuts' means rear sub frame front mounts. Are these prone to failure and worthy of replacement?
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Possibly failed diffmounts or the poly donuts need refitting... both easy enough to check, weather permitting :y
Reading through this thread again it is clear that Doctor Gollum and others have long known the problems of Omega rea r suspension, while I, Magwheels and others did not. I understand from earlier posts and Mandula's and Nick W's endeavours that 'diff' mounts are no longer available from Vauxhall. Luckily mine are OK.
I presume 'poly donuts' means rear sub frame front mounts. Are these prone to failure and worthy of replacement?
I replaced a pair at the weekend, which were well on the way to becoming two-piece parts. Standard ones are readily available for sensible money and will outlive the car, so no ingenuity is required.
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Possibly failed diffmounts or the poly donuts need refitting... both easy enough to check, weather permitting :y
Reading through this thread again it is clear that Doctor Gollum and others have long known the problems of Omega rea r suspension, while I, Magwheels and others did not. I understand from earlier posts and Mandula's and Nick W's endeavours that 'diff' mounts are no longer available from Vauxhall. Luckily mine are OK.
I presume 'poly donuts' means rear sub frame front mounts. Are these prone to failure and worthy of replacement?
I replaced a pair at the weekend, which were well on the way to becoming two-piece parts. Standard ones are readily available for sensible money and will outlive the car, so no ingenuity is required.
Thanks. I must check mine. I presume visual inspection and levering things about will tell me if they are shot.
I'm glad you did a couple at the weekend. Hayes gives the job just 2 spanners, trivial. Feeutso, in the Forum guide, made rather heavier weather of it. Haynes, of course, did it on a brand new car, whereas Feeutso did it on an old one, without the special Vauxhall tool.
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I replaced a pair at the weekend, which were well on the way to becoming two-piece parts. Standard ones are readily available for sensible money and will outlive the car, so no ingenuity is required.
Thanks. I must check mine. I presume visual inspection and levering things about will tell me if they are shot.
I'm glad you did a couple at the weekend. Hayes gives the job just 2 spanners, trivial. Feeutso, in the Forum guide, made rather heavier weather of it. Haynes, of course, did it on a brand new car, whereas Feeutso did it on an old one, without the special Vauxhall tool.
It all revolves around prying the old ones out; the rubber coating the outside of the metal sleeve makes getting them started slow work. The four I've done all pried out using a large cold chisel, then small pry-bars on opposite sides at the same time(the real key to it), and finally a large claw hammer to remove them. With the car on a ramp, or over your pit, you'll be able to apply a lot leverage than with it on axle stands in the street
Fit the new ones by pressing them back in with the jack. A generous squirt of silicone lubricant makes this much easier.
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i don't remember it before though, maybe it is my new tyres.
Are they shit tyres?
http://www.mytyres.co.uk/rshop/Tyres/tristar/Ecopower-4S/235-45-R17-97W-XL/R-279995 c rated in the wet
Ah, well, yes. Properly shit tyres ;D
Did you honestly expect then to be good - it even says on the labels they will be lethal in the wet.
The properly translated tyre labelling:
A - Covers a huge range of somewhere between adequate for miss daisy to a good tyre.
B - Pretty shit, and unsuitable for a medium powered car. Wear 2 pairs of pants when driving.
C - Really shit. Unbelievably shit. Keep the life insurance policies up to date.
If you want an adequate tyre, A is your only choice.
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Thanks for the advice Nick. I got my car over the pit this afternoon, jacked up both sides near the rear, and levered the rear sub frame mounts about. They really did not move much, not at all sideways, not much up and down. I have seen them move further in MOT tests, but not on this car.
Haynes jacks up and supports the entire rear of the car, removes wheels and front mount support plates, then lowers the sub frame a bit, pops the bolt in the top of the mount, and pulls it down with the puller. You and Feeutso do them one at a time, prying the mounting out from below. I cannot see how I could use my pit with the Haynes method, but I could with yours. From the way you describe it, it can be done. But you're the man who can change rear wheel bearings, which also sounds daunting!
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Thanks for the advice Nick. I got my car over the pit this afternoon, jacked up both sides near the rear, and levered the rear sub frame mounts about. They really did not move much, not at all sideways, not much up and down. I have seen them move further in MOT tests, but not on this car.
Haynes jacks up and supports the entire rear of the car, removes wheels and front mount support plates, then lowers the sub frame a bit, pops the bolt in the top of the mount, and pulls it down with the puller. You and Feeutso do them one at a time, prying the mounting out from below. I cannot see how I could use my pit with the Haynes method, but I could with yours. From the way you describe it, it can be done. But you're the man who can change rear wheel bearings, which also sounds daunting!
Front subframe bushes are a simple brute force job. Having some extra room to apply it would make the job much easier!
Considering how long the bolt is, you'd have to almost remove the subframe to 'pop it in the top of the mount' :o
Doing one side at a time means that there's no need to jiggle the subframe around to refit the bolt, as it just goes straight back in.
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i don't remember it before though, maybe it is my new tyres.
Are they shit tyres?
http://www.mytyres.co.uk/rshop/Tyres/tristar/Ecopower-4S/235-45-R17-97W-XL/R-279995 c rated in the wet
Ah, well, yes. Properly shit tyres ;D
Did you honestly expect then to be good - it even says on the labels they will be lethal in the wet.
The properly translated tyre labelling:
A - Covers a huge range of somewhere between adequate for miss daisy to a good tyre.
B - Pretty shit, and unsuitable for a medium powered car. Wear 2 pairs of pants when driving.
C - Really shit. Unbelievably shit. Keep the life insurance policies up to date.
If you want an adequate tyre, A is your only choice.
Accepted. However, all my cars are on shite tyres, and X168 is my only twitcher. I suppose I could switch tyres between X168 and V828, my other 2.5 manual petrol estate, currently shod, like X168, with 4 steel wheels, and on shite tyres, but not twitching.
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Thanks for the advice Nick. I got my car over the pit this afternoon, jacked up both sides near the rear, and levered the rear sub frame mounts about. They really did not move much, not at all sideways, not much up and down. I have seen them move further in MOT tests, but not on this car.
Haynes jacks up and supports the entire rear of the car, removes wheels and front mount support plates, then lowers the sub frame a bit, pops the bolt in the top of the mount, and pulls it down with the puller. You and Feeutso do them one at a time, prying the mounting out from below. I cannot see how I could use my pit with the Haynes method, but I could with yours. From the way you describe it, it can be done. But you're the man who can change rear wheel bearings, which also sounds daunting!
Front subframe bushes are a simple brute force job. Having some extra room to apply it would make the job much easier!
Considering how long the bolt is, you'd have to almost remove the subframe to 'pop it in the top of the mount' :o
Doing one side at a time means that there's no need to jiggle the subframe around to refit the bolt, as it just goes straight back in.
Did it first time outside, 0.5 meters of snow and -20 C degrees around me. One side at a time using only car jack, crow bar and wrenches. Took like three hours :)
Second time was about 1,5 years later (summer time), because donuts were already defected. Changed them to polys, took only one hour with same method :D
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There has been a lot of discussion on OOF about front wishbone bushes, steering idlers, rear doughnut bushes and diff mounts. I have also seen discussions about freeing up the adjusters in the rear track rods.
I don't recall anyone reporting wear or failure of the semi-trailing arm bushes or the rear track rod bushes. Logically we should be seeing failures as they are just as old as all the other bushes. :-\
Knackered semi trailing arm bushes could give the symptoms as described. Thoughts anyone?
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There has been a lot of discussion on OOF about front wishbone bushes, steering idlers, rear doughnut bushes and diff mounts. I have also seen discussions about freeing up the adjusters in the rear track rods.
I don't recall anyone reporting wear or failure of the semi-trailing arm bushes or the rear track rod bushes. Logically we should be seeing failures as they are just as old as all the other bushes. :-\
Knackered semi trailing arm bushes could give the symptoms as described. Thoughts anyone?
I think that it's a design/installation problem: somebody forgot GM policy, and designed them with the correct geometry! Semi-trailing arm bushes aren't a problem on Ford's IRS either.
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There has been a lot of discussion on OOF about front wishbone bushes, steering idlers, rear doughnut bushes and diff mounts. I have also seen discussions about freeing up the adjusters in the rear track rods.
I don't recall anyone reporting wear or failure of the semi-trailing arm bushes or the rear track rod bushes. Logically we should be seeing failures as they are just as old as all the other bushes. :-\
Knackered semi trailing arm bushes could give the symptoms as described. Thoughts anyone?
I watch all my car MOT examinations, 6 Omegas a year. I have not seen the MOT testers handbook, but they always check - insert crowbar and attempt to move - the semi trailing arm bushes and the rear track rod bushes, as well as the rear sub frame bushes. Very occasionally I get an advisory note concerning play in the rear track rod bushes, never an MOT failure. My impression is that the rear suspension doesn't move much, doesn't steer, and gives little trouble. However, I have one twitcher, and don't know why.
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I had a front wishbone rear bush fail once, and it felt for all the world like the back end was stepping out whenever I reversed a turn at "spirited" pace.
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Ah, well, yes. Properly shit tyres ;D
Did you honestly expect then to be good - it even says on the labels they will be lethal in the wet.
The properly translated tyre labelling:
A - Covers a huge range of somewhere between adequate for miss daisy to a good tyre.
B - Pretty shit, and unsuitable for a medium powered car. Wear 2 pairs of pants when driving.
C - Really shit. Unbelievably shit. Keep the life insurance policies up to date.
If you want an adequate tyre, A is your only choice.
wow G must be terrifying then. and D, E and F. :o
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I had a front wishbone rear bush fail once, and it felt for all the world like the back end was stepping out whenever I reversed a turn at "spirited" pace.
There's a thought. I fitted new ATEC wishbones in March 2014 when I bought the car. They have done 20,000 miles. I will check them out.
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I had a front wishbone rear bush fail once, and it felt for all the world like the back end was stepping out whenever I reversed a turn at "spirited" pace.
There's a thought. I fitted new ATEC wishbones in March 2014 when I bought the car. They have done 20,000 miles. I will check them out.
It was a strange feeling. Used to get it coming off roundabouts particularly. A bit of steering lock and put a bit of power on and it felt like the back end had gone, yet you could actually proceed to lean on the steering quite hard without it actually letting go, just something "shifted" as you applied steering input. It really felt like it was at the back end but, as said, it was the front wishbone bushes in the end.
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Ah, well, yes. Properly shit tyres ;D
Did you honestly expect then to be good - it even says on the labels they will be lethal in the wet.
The properly translated tyre labelling:
A - Covers a huge range of somewhere between adequate for miss daisy to a good tyre.
B - Pretty shit, and unsuitable for a medium powered car. Wear 2 pairs of pants when driving.
C - Really shit. Unbelievably shit. Keep the life insurance policies up to date.
If you want an adequate tyre, A is your only choice.
wow G must be terrifying then. and D, E and F. :o
turns out the difference between A and C is 7% more total stopping distance approx, from 50mph in the wet.
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Ah, well, yes. Properly shit tyres ;D
Did you honestly expect then to be good - it even says on the labels they will be lethal in the wet.
The properly translated tyre labelling:
A - Covers a huge range of somewhere between adequate for miss daisy to a good tyre.
B - Pretty shit, and unsuitable for a medium powered car. Wear 2 pairs of pants when driving.
C - Really shit. Unbelievably shit. Keep the life insurance policies up to date.
If you want an adequate tyre, A is your only choice.
wow G must be terrifying then. and D, E and F. :o
turns out the difference between A and C is 7% more total stopping distance approx, from 50mph in the wet.
Probably from the best wet gripping C to the absolute bottom end of A. A is the minimum you should be looking at. Anything else is shit.
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As Al seems very confident re the diff bushes and tb about the tyres they're probably right. However would the rear toe cause such an issue?
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If the tyres are that low, which they are reading into Pauls other thread, then that has to be first port of call :y
If new tyres don't cure the problem then it will need revisiting...
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I had a front wishbone rear bush fail once, and it felt for all the world like the back end was stepping out whenever I reversed a turn at "spirited" pace.
There's a thought. I fitted new ATEC wishbones in March 2014 when I bought the car. They have done 20,000 miles. I will check them out.
Today I jacked front of car up, heaved the hub about, could not detect any slack. Removed wheels, inspected lower joints, look fine. Pity, was hopeful there. MOT is due next month, I'll see how the tester heaves it about, he may find some slack there.i