Hi All, I’m new to this so be gentle with me

 

I have just had 2 new Goodyear Eagle F1 tyres put on vRS and 3 of the wheels re-aligned. Since having them fitted the car seems to be under steering (only every now and again) only on wet roads. I had the wife and kids in the car each time its happened so I wouldn’t have been going any faster that 20mph max round these corners/roundabouts.

 

My first thought it may be the tyres so took it back to the shop and they put it back on the ramps – Turns out the wheel alignment needed doing again. I thought this might be the cause but it is still under steering since being done again.The tyres are top of the rage and have one of the best ratings I can find for wet grip so the shop are adamant its not an issue with the tyres.

 

Can anyone please help with what the issue might be?

 

Thanks

 

Hi, and welcome!

I am a bit puzzled by the statement that you had "three of the wheels" re-aligned.

Proper four-wheel alignment is just that - what matters is the alignment of all four wheels relative to each other.  I'm not sure that you can have just three wheels aligned!  What kind of alignment did you have done exactly?

However I suspect that tyres, and more particularly, a possible mis-match front-to-rear, are more likely the cause of your problem.

You say you had two new tyres fitted.

- to the front or to the rear?
- what make / type are the other tyres?
- how worn are these other tyres?
- are they the same size / section / profile as your two new tyres?
- what pressures are you running at, front / rear?
- have you tried swapping the front wheels to the back (and adjusting all the pressures accordingly) and then seeing whether the problem is worse, better or no different?

If you haven't, try it, and please let us know how you get on.


 

How many miles have you done on the new tyres?

 

You will need to run them in until the releasing agent etc. has been removed.

 

I am a bit puzzled by the statement that you had "three of the wheels" re-aligned.

Proper four-wheel alignment is just that - what matters is the alignment of all four wheels relative to each other.  I'm not sure that you can have just three wheels aligned!  What kind of alignment did you have done exactly?

However I suspect that tyres, and more particularly, a possible mis-match front-to-rear, are more likely the cause of your problem.

You say you had two new tyres fitted.

- to the front or to the rear?

- what make / type are the other tyres?

- how worn are these other tyres?

- are they the same size / section / profile as your two new tyres?

- what pressures are you running at, front / rear?

- have you tried swapping the front wheels to the back (and adjusting all the pressures accordingly) and then seeing whether the problem is worse, better or no different?

If you haven't, try it, and please let us know how you get on.

 

Hi and thanks for the quick responses,

 

Sorry I meant 3 wheels adjusted when the 4 wheel laser alignment was done.

 

• The new tyres went on the front and I had the previous front tyres moved to the back
• The older tyres are Federal (595 Evo)
• The Federal's are in great condition as they were pretty much new when I bought it in December - still about 5mm on them.
• There the same size/selection and profile as the F1’s (225 40 (z)R 18 92y - as it reads on the tyre)
• The pressures I use are F: 35 and B:32 (I thought this was a little high but I used a forum on Briskoda to confirm and looks as though some of the other vRS guys are running on the same) when the new ones were fitted they had put the F: 32 and B: 29 - i thought lower pressure might have been a factor so topped them up as above.
• I haven’t tried swapping them over but I will defo try this now and see what happens – and let you guys know how I get on

 

How many miles have you done on the new tyres?

 

You will need to run them in until the releasing agent etc. has been removed.

 

I have done nearly 300 Miles since the new tyres have been fitted so i would have thought they'd have worn in by now?

 

 

Thanks again for your feedback guys – I’m still getting used to having a car of this performance so all feedback is welcomed with open arms

I've just looked inside the fuel flap on my Blackline and tyre pressures are 2.0/2.1 bar front/back for normal loading which is circa 30psi

 

HTH

 

Ade

I'll have to have a look see what mine says in the fuel cap. Perhaps the garage and I were both wrong and could be the cause.

Thanks for the info

Try 35 psi in the back too.

If your car is more than a few years old then it might be a problem with worn bushes. You only complain of understeer at low speed i.e. more extreme steering angles. I am guessing that at higher speeds worn bushes might only produce a general vagueness in the steering but have a more pronounced effect nearer full lock? Someone good at steering geometry can probably inform you better but I don't think it is tyres or inflation pressure from your description.

It won't be the tyres unless it is a pressure issue as I have just put 2 Goodyear eagle F1's on the front of mine and put the Continentals on the back axle and after having my winters on the thing rides on rails now. The F1's just have so much grip and really accurate positioning with hardly any if at all understeer.

Generally, a tyre with more air in it will understeer less.

Understeer or oversteer depends on the 'slip angles' of the tyres.  The phrase 'slip angle' is somewhat misleading - although it is the conventional technical term, the tyres aren't normally slipping, they are flexing.  That's what tyres are for!

This means that, except when travelling in a straight line, there is always a difference between the direction a tyre is pointing and the direction it is actually going.  If the slip angles are greater at the rear, the car will oversteer; if the slip angles are greater at the front, it will understeer.

The amount the tyre flexes and thus its slip angle depends on, among other things, the stiffness of the carcase, the air pressure in it, its size and profile and the load on it.  This is why, for instance,  a stiffer rear anti-roll bar (which transfers more weight to the outside rear wheel) tends to increase oversteer, and why higher pressure in the rear tyres tends to reduce oversteer.

A quick and simple way of fine-tuning over- and under-steer is by small changes to the difference beween front and rear tyre presures.  But don't overdo it - you dont want to end up with uneven tyre wear.  Too much pressure = centre of tread wears out.  Too little pressure = edges of tread wear out, and more important, extra rolling resistance and  risk of overheating / tyre damage. 


 

Edited 28 April, 201412 yr by Stuarted

I run mine 31 psi all round, i've found it the best compromise between ride and grip.

 

FWIW i found the assymetric 2's seem to take a long time to "bed in" when they are new.  Give them some time and i'm sure you'll find them pretty grippy - i'd not expect them to be fully up to spec until you've done around 500 miles.

Thanks Guys, Some really good feedback here and I really appreciate it.

 

I think I will have a play about with the pressures over the weekend see if it helps then if not I will try swapping the front and backs over and see how that fairs.

 

Obviously if anyone has any more ideas, I’ll try anything to get her back on the road and handling like the dream she is again.

 

Thanks again

 

It won't be the tyres unless it is a pressure issue as I have just put 2 Goodyear eagle F1's on the front of mine and put the Continentals on the back axle and after having my winters on the thing rides on rails now. The F1's just have so much grip and really accurate positioning with hardly any if at all understeer.

Can you tell me what pressures your running your Fronts and backs on please bud?

I am running 35psi all round on my tyres, and pumped them up to that as I thought they looked a little under inflated and they drive fine.

I run the goodyears and find them particularly good, run with about 32/33 psi as I usually have 4 in the car. Never had any issues with understeer unless I'm pushing it more than usual.

One thing though is it's been recommended to put the new tyres to the back. I think the last time I saw something about it was on Fifth Gear, showed better overall grip.

Hope you get sorted.

Yup - tyres with best tread / grip on the back.

Plenty of comments here in various threads explaining that it is far more dangerous if the back end suddenly and unexpectedly lets go (car spins) than if the front end does (car just goes straight on - not good, but much better than spinning).

Same advice, consistently, from tyre manufacturers and tyre fitting companies, regardless of whether car is front-wheel or rear-wheel drive.

 

Agreed,  good/new tires should always be in the back, not front

well so far so good, i put 29PSI in all round and hasnt slipped yet (touch wood). If it does happen again i will be changing the fronts for the backs but fingers crossed it was just a pressure issue. Thanks again for all your feed back guys.

Well I put my new tyres on the front and kept my Continentals on the back as they were still over 6mm and were wearing evenly with no sawtoothing etc. I couldn't care less what magazines etc say, I want the quieter tyres on the front, obviously if my rears were 'worn' I would just replace them at the same time !

Well I put my new tyres on the front and kept my Continentals on the back as they were still over 6mm and were wearing evenly with no sawtoothing etc. I couldn't care less what magazines etc say, I want the quieter tyres on the front, obviously if my rears were 'worn' I would just replace them at the same time !

You will be fine. I think the grounds for the 'new tyres on the back' argument assumes a massive difference between the general state of the tyre. Having more mm of tread depth is not necessarily synonymous with less grip anyway as the latter depends on so many other qualities of the tyre as well as the road conditions.

Generally, a tyre with more air in it will understeer less.

Understeer or oversteer depends on the 'slip angles' of the tyres.  The phrase 'slip angle' is somewhat misleading - although it is the conventional technical term, the tyres aren't normally slipping, they are flexing.  That's what tyres are for!

This means that, except when travelling in a straight line, there is always a difference between the direction a tyre is pointing and the direction it is actually going.  If the slip angles are greater at the rear, the car will oversteer; if the slip angles are greater at the front, it will understeer.

The amount the tyre flexes and thus its slip angle depends on, among other things, the stiffness of the carcase, the air pressure in it, its size and profile and the load on it.  This is why, for instance,  a stiffer rear anti-roll bar (which transfers more weight to the outside rear wheel) tends to increase oversteer, and why higher pressure in the rear tyres tends to reduce oversteer.

A quick and simple way of fine-tuning over- and under-steer is by small changes to the difference beween front and rear tyre presures.  But don't overdo it - you dont want to end up with uneven tyre wear.  Too much pressure = centre of tread wears out.  Too little pressure = edges of tread wear out, and more important, extra rolling resistance and  risk of overheating / tyre damage. 

 

 

In a staighdst line, any slip angle is due to alignment: toe in or out. Most cars have toe in to improve straight line stability and feel. The tyre is slipping (i.e. scrubbing material off the surface) because the rolling direction is slightly different to the direction of travel. It's analogous to flying a plane in a cross wind: the heading of the plane is different to the direction it is flying, you have to yaw it into the wind.

Most cars front suspension are design to reduce the amount of toe in under roll to generate understeer, some rear designs the opposite for the same reason (remember the trend for small amount of rear wheel steer designs particularly from the likes of Honda back in the 80s and 90s). This is why fitting a stiffer RARB to the Octavia works, preventing roll prevents the toe out condition under hard cornering (plus some likely camber changes too) all of which maintain the grip of the front tyres better. Downside is that the designed-in inherent safety of natural progressive understeer has gone, and if driven too fast and clumsily could end up in an altercation with a hedgerow, or worse..

 

Ultimately, understeer v oversteer is about controlling the relative changes in grip between front and rear tyres in dynamic roll conditions. Tyre pressure can influence grip levels, along with the geometric changes under roll, though have a much smaller effect (on a road car). Slip angle is not the same as a soft tyre rolling onto its sidewall.

Edited 1 May, 201412 yr by stever750

Just thought I would let you guys know…

 

I tried the tyres at 29PSI all round but still had issues.

 

I have now swapped the fronts for the backs and all seems to be going well. With any luck the problems sorted but will post it up if I have any more issues.

 

Thanks again for all your help.