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Understeer Problem


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#16 FOCA

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Posted 27 January 2013 - 05:47 PM

in winter normal tyres the rubber goes hard and the tyres take a long time to soften up while the tyres are hard the grip is very poor so you will understeer easily i think its just that and once the weather warms up the problem hopefully will have stopped


Exactly what i was going to say -

the type of rubber in modern "summer" tyres does not grip well under 7 degrees centigrade, - under 4 degrees,c they are worse, in my experience

,

winter (tarmac) tyres have a special rubber compound that stays pliabie/ grippy at low temps- i run vredstiens - you would not believe the differece they make

it is difficuly to get heat into the tyres at these temps, they start off with 8mm tread, once you have rounded off the front "shoulders" of the tyre, or worn the tyres down, the blocks of rubber can't move around so much to generate heat

im sliding around a bit more now - i think its the salt on the road (as well as the low temps)(no ice/ snow where i live now)

roundabouts are notorious for spilt diesel and can be very slippery with the slightest hint of moisture or low temprature, bumps, the state of the roads, camber (usually running to the left) all compound the lack of available grip (with the low temps/ tyres that are not good at low temps)

The pressures are critical, don't just stick the recommended pressures in - try different pressures (within reason)
the "for high speed/ heavily laden" pressures may be more appropriate for you

the diesel has a heavier engine, probably stiffer springs, more torque, (the torque and the weight helps to put heat into the front tyres) most of the steering, braking etc is all about the front end on these cars
I think you drive / corner faster than most drivers on the road, and have a "feel" for your car that, many drivers, do not have, most drivers do not find/ explore the limits of their cars handling, you owe it to yourself to invest in decent rubber, (the Michelin is an "eco" tyre, ive never heard of the other ones )

As others have said - a decent set of tyres would transform your car, 4 is best, but at least 2

Ive tried Pirelli, Michelin, Dunlop, Avon etc , i run Goodyears (my favorites) in the spring/ autumn, i have a couple of "no brands" i am trying to wear out (i stick them on the nsf in the warm summer) they seem to last forever, (3 years+) but very little grip


There is a possibility that something else has been knocked/ twisted - subframe bushes, wishbones etc etc - tracking cannot pick up everything, i have personally have trouble with tracking that was supposed to be "ok" - remember, you are expected to drive it like a tea trolley like everyone else :) if you know what i mean

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#17 Philip Male

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Posted 28 January 2013 - 06:28 PM

some great answers there and you've all got a piece of what i think is the answer.

at the weekend i broke out the trolly jack to swap tyres around, but i thought before that i'd just double check the pressures again.
reason thinking, it was fairly cold when i did them, and i put a little much in then
now it was 14c outside the fronts were 32.5 and the rear 35.5
so that explains alot!
whats weird, in my experience of other cars pressures, is the lower pressure has made the steering lighter and more responsive, pretty much how i remember it being the first few drives, it's lacking a little feel, but thats probably cold winter driving as mentioned above lowering grip.

2nd, the scary roundabout was only 1.5 miles from work, again it was cold, and there's no heavy braking really to get the temps up, by the time i got home it was better, but i had that me as me treating it like crystal glass.

tyre depths were taken from a service end of last year, i checked them with a borrowed, and somewhat crusty depth gauge at the weekend, actual depth was 4mm, not accurate enough to tell if it was different across the tyre because it was too stiff.
a new gauge and pen style pressure reader are in the post.

i've only ever heard your best rubber should be on the back in a FWD car, you'll loose traction at the front first and know to back out before the rear tries to overtake, and as a side, it wears out the old rubber first.
my intention is to wear out the budgets first, but i could try swapping again, see if the michelins are better now the tracking's sorted, as said, i hated the feeling before.
these tyres were nearly new when i got the car, and they needed replacing after about 7k on the front, so these i have now should be ready to swap over in the summer so long as i leave them on the front, they have too much tread and my wallet too little money to just bin them for a new set right now.
and i'd rather not have the grip difference the other way around, esp when it's cold and the rears would be slippy

to be honest when reading about correct pressures, primacys were mentioned as the ford test drivers choice, but that was on a diesel and they were comparing what tyre makes need what pressures.

so, the next issue i need to sort is this knock.
i don't know if i had it before the kerbing
but every time you turn right from any position you get a click/knock, it's not very serious but it's there, it's passed an MOT with no notification. it's been checked and was told it's maybe the pinion rounded off?? you can feel it on the track rods as a vibration, left side more than right.
with the car jacked up and someone holding the wheel you can't feel it rocking the right wheel, but can just about feel it if pushing with arms and knees on the left.
couldn't get my head up far enough with the wheels on the floor to see if the rod ends were moving at the power steering unit.
don't think it'd be enough to change the steering angles during driving but you never know.

any ideas??

#18 Philip Male

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Posted 28 January 2013 - 07:17 PM

I think you drive / corner faster than most drivers on the road, and have a "feel" for your car that, many drivers, do not have, most drivers do not find/ explore the limits of their cars handling, you owe it to yourself to invest in decent rubber, (the Michelin is an "eco" tyre, ive never heard of the other ones )

you're probably right, i'd say i'm a very average driver, i have no extra level of car control or skill ( unless i can translate what my right thumb can do with a RC car to full size on a track ), but i can sense what a cars doing i guess more so than other normal people i know, they think i'm mad when i talk about how it feels, and there they are with 19psi in the tyres and the only comment when i put it right is, umm the steering's lighter.
you mention over/understeer, cornering balance, turn in ect they think you're talking BS, or drive like a t**t, which i guess as they pootle along ( admiring the end of their bonnet ) i must seem.
even a garage can't take handling comments seriously to find a cracked antiroll bar link.

don't know where the primacy sits in the range, after reading reviews for focus/tyre combos i wanted eagle f1's? which were only about 15 quid each dearer, but they didn't have on stock, and give the normal, they know best, bs that these are fine unless you want to do trackdays.
http://www.tyrerevie.../Ford/Focus.htm

front or rear?? from the fat bloke himself
http://www.michelinm...elin_042009.pdf

The AA also agree:

New tyres to the front or rear?

Check the handbook first as some give vehicle specific advice.

Generally it's good practice to fit the best/newest tyres on the rear – in wet conditions, this favours understeer rather than oversteer.

So if you have the front tyres renewed it's best to have the rear ones moved to the front and the new tyres fitted to the rear.

Tyres with deep tread are less likely to puncture and it's more difficult to control a car with a damaged rear tyre.

#19 Philip Male

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Posted 28 January 2013 - 07:35 PM

ha, ok, it's a woman ;) , and her trousers are all kinds of wrong, but shes got a point


#20 artscot79

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Posted 28 January 2013 - 07:44 PM

She would if they werent all rear drive cars

#21 Andy H Dibley

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Posted 28 January 2013 - 08:00 PM

She would if they werent all rear drive cars


...and they weren't two different types of car.

I've never heard this before, and to be honest, I'm finding it hard to believe at all. If you keep the tyres at the recommended pressures for the weight of the car, and at the tread depths which the manufacturers specify, you'll find you won't suddenly spin out.

#22 Philip Male

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Posted 28 January 2013 - 08:07 PM

it's having a difference of tread thats the problem, and given my difference in tyre, the quality of the compound, so the cheapies will stay on the front till their more like 2.5-3mm

see if Vicki can sway you in a FWD


i've only ever know this advice, and i don't know why, given a large difference in grip levels, you'd want the worse at the back
rotating to keep them the same is different

#23 Andy H Dibley

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Posted 28 January 2013 - 08:16 PM

Alright... I'll go along with that.

Still, I buy 4 at a time and try and get a better discount :P

#24 Stoney871

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Posted 29 January 2013 - 02:04 AM

I brought this very point up with a Traffic Officer last year concerning positioning new tyres on the rear of a front wheel drive car and his response was "Cobblers".


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