The Age Old Tyre Debate

Well, its test time next week for my S1, and I think the two back tyres could do with replacing.

Does anyone have any particular preference with these? Its currently on Mich Energy (or is it Primacy?), but I'm not overly impressed with the ride / noise, and grip. I'd be interested to know what boots everyone else prefers to put on theirs?

My S2 is on 4 BF Goodrich jobs, and I find the grip in those quite good (though the rear can go slightly in the wet sometimes), SWMBO mainly drives it these days, so it rarely leaves the city roads, and hardly ever gets near being pushed, to be honest. That aside, they were a good hard wearing tyre when I drove it daily for a year, and I don't tend to hang about by any means.
I've only had to replace one, which was the front passenger side, it became unevenly worn due to a bad balljoint on that side, but its the only one I've had to touch in two years.

Really I'm after something with good grip and not a harsh ride, any preferences?

Ciarán

Ciaran,

I USED to fit premium Michelins, Pirellis, Dunlops, whatever, then when money got a bit tighter I started using "economy "Fulda" tyres for years without problems.
205x 55 front and 225 x 55 rear.

Excellent grip wet or dry, very good mileage - road noise is no more nor less than "premium" tyres.

The bonus is that I can have a set of four fitted and balanced for under £200.

I've had them on various cars over the years - and currently on Celica GT, Scooby Estate and of course the XM. My Volvo T5 estate in Germany is fitted with "Winter pattern" Fulda's to comply with German regulations regarding "Winter driving" which insists on Winter tyres or snow chains - otherwise insurance is invalid!

I wondered why I was seeing so many prestige cars in Germany with scabby steel wheels in the Winter months!

As with any "peformance" rating connected with XM's - we're not talking about an ultimate performance / roadholding machine - just a good all round compromise.

Having said that, the Fuldas perform extremely well on the Celica GT - no complaints.

beachcomber

Hi Ciaran
I have Goodyear NCT Eagle 5's on mine.All fitted and balanced for £211 pounds.They are the correct size 205/55's(?)and have lasted around 37K so far with maybe another 6-8K left in them.I swop the fronts to rear every 10K.
When I bought the car they it was fitted with Economy tyres and they lasted around 15K including 2 punctures so they weren't very economical!
Personally I can't really see the point of saving £20 per tyre when you can get a decent set for a little more money.
I get mine from College Tyres in Perivale just off the A40 in North West London.I have been going there on and off since the mid 1980's.I had outsize tyres on my Mk1 Golf GTI(205's) and the tyres were Goodyear NCT Eagles(when they 1st came out)...cost £50 a tyre!!!Mind you they only used to last me 10K!!
Regards Rob

Hi Ciaran

You seem to be using your tyres the wrong way round. The worn out ones should be on the front on an XM. A new pair goes on the back of an XM and when the fronts are worn out the backs go onto the front and the next new pair onto the back. This gives optimun road holding and tyre tread depth throughout the working life.
As to tyre type I too favor Fulda but owing to my regular XM buying have not needed to buy new tyres in the last 5 years. I am satisfied that tyre type makes virtually no difference to the ride of an XM but tyre pressure variations can make major ride differences.
Then there is the write off cost risk to factor in. A puncture can happen at any time and I relegate it to emergency spare or write it off. There is a risk that it could happen the day after you fit a premium branded tyre and if so it will cost a lot more than writing off an elcheapo tyre.

Regards

XMexc

I'd steer away from mich energy's as I was seriously unimpressed by the lack of grip compared to P6k's that I was running previously.

Currently my V6 has Mich pilot primacy's fitted and they are reasonably good for wet/dry handling. But the P6K's were cheaper and handled just as well IMHO.

Not tried Fulda, but a couple of the guys at work recommend them too.

As mentionned already, new tyres should go on the rear, the tyre bay will likely insist even if you want them on the front, if they are any good, so they don't have any come-back when you spin it on a corner (like I did a few years back when k**P-F*k just lobbed 2 new ones on the front). It's up to you if you then chose to rotate them, but remember the rear is lighter and needs the extra grip when you're testing the handling

rgds
Dave

This post has been edited by aengus-xmv6 on January 29, 2008 01:20 am

Hi beachcomber,

I will have to disagree with that. Indeed this is most people's perception about Citroen's. And it is true for all Cits that don't have an hydractive suspension: unbelievable comfort combined with good handling characteristcs, although in reality the max lateral grip they can achieve in the "circle" test (hope u know what I mean) is just average -even if driver feels he's going very fast- (although this was also because they had very thin tyres).

But Citroens with Hydractive are another story -and I'm not speaking about the comfort-. I'm sure you wil have seen this video:

http://www.youtube.com/watch?v=gVPXgvOl0xc

Do you realise what it means that a 1.5 tonne family car equals a Lotus Elan in the slalom? Personally the thought that this *is* possible doesn't stop amazing me. I'm not sure how the best of modern cars would perform in such a test. Because, yes, they are tight, they have huuuge, low profile tyres, but that is by no means all the story when it comes to seriously put a car's balance into test. That is where hydropneumatics (as opposed to springs) are unbeatable: you just can't disbalance the car, no matter how much you try. That's all due to the properties of gas as opposed to coils (own-frequency of the medium). Additionally, under such favorable dynamics, tyres perform in an optimum way. Not to speak of trying to follow a hydropneumatic Cit on a road with not-prefectly smooth tarmac...

For another demonstration of hydropneumatics efficiency, check out this video after minute 2.38":

http://www.youtube.com/watch?v=BkBjKtC-3Hg

What happens to the poor "conventionally" sprung car, although extreme, is in its roots the same phenomenon that you will observe in any coil-sprung car in any strenuous circumstance: "pumping" occurs, and finally tyres loose contact with the tarmac, for smaller or larger periods of time.

So, yes the XM (or the Xant, or the C6) do not -and will never- give the feeling of an "ultimum driving machine" as fads means it -an Alfa, a BMW, an Impreza-, but, speaking of EFFICIENCY measured with numbers, they really are ultimum driving machines. And, if u asked my personal opinion, I'd say that although their steering is indeed "dead" of "feedback" as they say, they are very accurate in handling -you can turn in with the accuracy of a trigonometric compass-.

Now, Beachcomber, I'm sure you knew all that as you have delved deeply into engineering, but I had to note those facts because many people -Citroen owners even- tend to feed into the common perception that Cits are "the most comfortable cars", which is to take away half of the achievement of this firm in terms of advancement of vehicle behaviour.

BTW, the C6 beats a latest 5-weries 4x4 (!) (iX they r called?) in the slalom (have the online reference for anyone that wants it). From memory, a C6 would mark an avergare speed of 78km/h when the other vehicles of thest (Lexus etc) would be aroudn the 73-74km/h mark. Those in the know *will* understand what a difference of 4-5km/h in this test means in terms of relative ability...

Hmmm, at some point of time I *will* bring together all the sources of info I have on the function and performance of the hydropneumatic suspension and put it online, such a documentation is missing from the net at the mo.

cheers
George

Ciaran
I take it you know this shop?
http://www.mytyres.co.uk/start.html

Some saving could perhaps be achieved depending on what u will buy. Bought there my Kumhos KH15 (which have very good grip in both dry and wet, but are noisier than I'd like in a limo -but not sure that's a characteristic of the hydropneumatic suspension?-).

cheers
G

ps. sorry it's the KH11s I have.

Nice find with the BX 16V video.

We have roads like that in Sheffield!

A good test of a cars handling near me is the Peak District or the Snake Pass. My white XM was very impressive, so much so that on the first time I drove it the Lexus in front just couldn't get away from me.

Steve.

Hi George,

as you might imagine having spent the last 40+ years as an automotive design engineering consultant, I am well aware of the gist of your mail - although of course it helps to explain to others.

I've never doubted the handling of the XM and even on a "seat of the pants" comparison without the aid of instruments - it will run rings [ sorry about that] round my Volvo T5 estate, but my Wife's Scooby Estate would rival it - unfair comparison as it has 4 wheel drive, "active traction" etc.,etc.

These cars [ Volvo ] as I think I previously posted were eventually outlawed in British Touring Car Championships as they were giving the saloons a hard time [ ie won the championship]. Never seen an XM Estate racing?

The point I was making, is that the XM doesn't have the ultimate performance to outrun it's agreed handling capabilities - unless you are an absolute wally of a driver.

And I agree - that it will compare favourably with an Elan. But surely that kind of driving isn't the reason most people buy an XM, or is it? You'll find MOST posts discussing better MPG, not blasting round the Nurburgring.

On another tack - the cd figure of 3.00 has been long and widely touted [ including the Elan ] as being the "Holy Grail" - the CX Estate acheived that back in 19 hundred and omigosh.

On reflection, I would say that my CX Estates handled better than the XM Estate [ longer wheelbase? ]
Beachcomber

The advice to always put new tyres on the rear wheels has been circulated for a long time, but I'm not sure I agree with it. It seems to me that it's based on the fear of the back end breaking away.

The recommendation makes sense for rear wheel drive cars where the sideways forces on the back wheels have to withstand both driving and cornering loads and where injudicious use of power can cause breakaway, but on our front wheel drive cars the front tyres have to withstand higher cornering forces (because of the greater weight), driving loads and steering loads. Conversely, the lightly loaded rear tyres have an easy time withstanding relatively low cornering forces. The majority of the braking force is also on the front tyres.

As is now widely known, slick tyres give greater grip than treaded ones. The only purpose of the treads is to shift water off the contact patch in wet conditions and insufficient tread depth may lead to aquaplaning. If one end of my car is going to aquaplane I'd rather it be an easily controlled back ender rather than lose both steering and braking.

So there you are, you do what you like - at least until this nanny government passes a law against it - but my new tyres go on the front.

There is one proviso to this. New tyres don't give full grip straight away, they have to be "cured" over a few hundred miles. It could be argued that this curing process should be done more gently on the rear wheels and then changed over.

Derek

Hi Derek

The "new on the rear" advice I got from the Perelli web-site and was XM specific.

Regards

XMexc

Costco who sell/fit Mich also insist the same - from the manufacturer I think.

And I'd possibly argue the rears have an easier time, the front has power applied and front-wheel methodology says apply more power in a slide, opposite for RWD.

I have experienced the back end overtaking the front unexpectedly, and also sliding out when pushing it in roundabouts when the fronts were less worn.

as to aquaplaning, depends how low you let the tread get as to levels of risk - I change them at or just before 2mm and not had a problem even hitting big overflows in the outside lane at high speed, and having to brake hard.

rgds
Dave

Hi John,

I understand that, it has just never sat right to me for the reasons I stated.

Perhaps the answer lies in my final paragraph. Imagine a new XM with new boots all round, all of them needing curing before they give out full grip (and cure them too quickly and it lowers their performance). The rears are going to have an easy time of it and will cure slowly, the fronts would normally have a fairly hard time of it, but the car is restricted by the running in limitations and that will enable them to cure without too much stress over the next 1,000 miles.

When those front tyres eventually wear out, the rears will only be about 25% worn and, fully cured, will go on the front whilst the new ones on the rear will go through the slow curing process. And so on ad infinitum.

How does that sound? I must explain that my preference for putting new on front is because I usually finish up with well worn tyres all round. I also take it easy for the next 500 miles or so to allow them to cure.

Hi Dave,

Yes, essentially you shouldn't get aquaplaning as long as the tread depth is greater than the depth of standing water. Even with smooth tyres, aquaplaning shouldn't occur below a speed of nine times the square root of the tyre pressure - or so we were taught in the aviation world.

Derek

I think the 'newest tyres on the rear' idea is that it makes the car more stable in the event of a skid. I, am afraid, dont subscribe to it because new tyres give a better ride, and as I go in for comfort more than speed, are more benificially employed on the front.

I usually only use budget tyres as recomended by my local friendly tyre supplier, there doesn't seem to be much difference in the ride between of various makes, as xmexc says, the tyre pressures make for more difference. Running them 2 or 3 lbs below recommended pressure maks a considerable difference to the ride, I wouldn't recommend that you do this of course!

My 'cheap' tyres will usually do at least 30k on the front and seem to last almost indefinitly on the back.

Peter.N.