Technical Replacing tyres with a different brand - do in pairs or fours?

[mj2k]

This one would be a no-brainer on a Subaru since it's permanent 4x4 - you need to replace all 4 tyres at once to avoid centre diff wear, but on an Abarth, should you replace tyres in pairs or replace all four at once if you're changing to a different brand?

I've got some new lightweight 7jx17 wheels coming very soon (which means the tyre size will remain unchanged) and in this situation normally I'd just swap the tyres over to the new rims if the sizing remained unchanged.

But one of the front P Zero Neros is a bit worn (back ones are perfect) and the other one has been impacted in a crash so I wouldn't trust it any more. Since Goodyear Eagles look like a no-brainer as a replacement (cheaper, better grip, better wet braking, etc) it'll be getting those to replace the two fronts, but not sure what to do about the rears.

They're 'as new' (presumably the tyres weren't rotated) but since the handling characteristics are very different to the Eagles, I'm wondering if I should replace them too, or if, because the back end's so light, the rears do little but stop the backside from rubbing along the ground?

If they do have a significant effect I'd be best changing them since the more grippy fronts and less grippy rears could result in unpredictable oversteer, but if they pretty much carry no load it's going to make little difference what I do at the backside, so might as well leave the P Zeros on there.

 

[chris3234]

Depends on the type of 4x4 system some can handle the differences in tyres some can't


But I'd replace the two worn ones and out the older on the front as it's best practice to put new tyres on the rear
Certainly no need to replace all the tyres on a 2wd road car unless you use it for track driving or something else

 

[RedAbarthMTA]

Personally, and this is a very "your choice" sort of question, I would put the Pirellis on the back. Lets face it, unless you are really pressing on or on a track day, all the back tyres do is stop the back end rubbing on the floor. Simplistic, I know and I know someone will jump in with the "but it provides 40% of the brake force" which whilst accurate, in normal day to day driving should not make very much difference. Only at the ragged edge of performance will it become important.As you say, on a permanent 4x4 such as our S4 Quattro then yes fit all 4 corners with the same and ideally the same wear state, but this is not the case for the Abarth.Just my opinion.

 

[jrkitching]

in normal day to day driving should not make very much difference

Normal day to day driving isn't the reason for putting the tyres with the most grip on the rear. It's the abnormal situation (usually either aquaplaning on a flooded road, or skidding on snow/ice) where you don't want the rear giving way before the front. That's when it makes the difference between a controllable understeer and a dangerous oversteer.

Some tyre fitting places (Costco is cetainly one) won't give you the choice; if you're just replacing a pair, they'll put them on the back, swapping the existing rears to the front if it's the fronts that have worn out.

 

[RedAbarthMTA]

Seems Uniroyal agree with you so I shall bow to more relevant knowledge :worship:

( and will from now on fit new to the back )

 

[mj2k]

Thanks all, must admit I do like 'pressing on' a bit - the roads round where I live are perfect for it

https://www.youtube.com/watch?v=k_mE2V9kWFU

Must admit I'm not a fan of excessive understeer so I wouldn't be wanting to put the older, less grippy tyres on the front, but equally wet handling / braking is an issue - they conflict as far as the rear tyres go.

Having grippier rears definitely helps when it comes to aquaplaning, etc and having less grippy rears has an interesting effect under heavy braking (as does putting overly powerful brakes on the rear) - since even more load is transferred to the front in heavy braking, the rears lock up more easily and the last thing you want is rear-end oversteer during an emergency stop, that's real 'change of underpants' territory

So I might end up swapping all four (the cost of switching the Pirellis over is about 1/3 the cost of new Eagle Asymmetrics using the right offers at the mo, so 'man math' says getting new ones all round makes perfect financial sense) and I might as well save the 2 good Pirellis as 'emergency tyres'

 

[Ralf S.]

The theory is correct.. but in practice I've never had any problems with mis-matched tyres, even different brands on the same axle, although that's tended to be "what it came with" rather than what I fitted. I think you'd probably have to be on a perfect surface at 95% of the best tyre's capability to notice that one or more of the other tyres aren't in the same league.

But if you have new rims, you might as well put the same tyres on all of them and leave the Pirelli's on their rims. If you ever decide to sell the rims, having good tyres on them will make them worth more.

Ralf S.

 

[mj2k]

The theory is correct.. but in practice I've never had any problems with mis-matched tyres, even different brands on the same axle, although that's tended to be "what it came with" rather than what I fitted. I think you'd probably have to be on a perfect surface at 95% of the best tyre's capability to notice that one or more of the other tyres aren't in the same league.

But if you have new rims, you might as well put the same tyres on all of them and leave the Pirelli's on their rims. If you ever decide to sell the rims, having good tyres on them will make them worth more.

Ralf S.

Weirdly I often find the opposite - for a standard rim which would be used as a 'fix' a very good tyre is a definite plus and the buyer's usually willing to pay the extra for postage or come and pick it up.

But if the rims are an 'upgrade' for sale on Ebay (I suspect some 17" Abarth Turismo rims would be a nice upgrade for someone with a 500 pop) people usually want to fit their own choice of tyre, and baulk at the cost of paying extra postage for tyres they'll be paying to remove / dispose of at the other end, so 'bare' wheels are easier to sell in that case.

 

[RichardH13]

Pairs is OK

I always have the new ones on the front, they say new on the back is better, but I've never noticed a difference.

If you can afford to replace all 4, then go for it

 

[portland_bill]

Pairs is fine. With higher performance cars, like the Abarth, a pair of the same tyre is best on each axle. On lesser cars, often only one tyre is replaced due to damage, and in most cases this makes little difference, although some cheaper brands can have a greater effect.

Many people will advise always sticking to the same brand, but each manufacturer constantly updates their tyres, with differences in construction, compound and tread design. Finding exact replacements is usually difficult, so go with whatever you like, in pairs.

 

[mj2k]

Pairs is OK

I always have the new ones on the front, they say new on the back is better, but I've never noticed a difference.

If you can afford to replace all 4, then go for it

I think it more relates to potential issues in the rain or under heavy braking if your fronts are nice new PS4s for instance, and your backs are a pair of balding Funken Orfuls (or equivalent ) - if the grip at the rear gives up the back end will try to overtake the front, which is not a good thing unless you're driving a Capri...

But then, if the bald Funken Orfuls were on the front, the car would most likely handle like a pig in a shopping trolley on corners in the rain, so you win some, you lose some.

 

[AndyRKett]

In this particular case when by the sounds of things only a pair of tyres need replacing and the others are fine then I’d just replace the pair and have no concern.

If this is the black abarth with front end damage I’ve seen on another thread (as you mention one tyre being accident damaged) then it will allow you to get the rest of the damage sorted and then later if you feel strongly inclined you can replace the other two for peace of mind.

As for 4x4 cars, a sensible person might replace all 4 every time but in all honesty even having a couple of psi difference in one back tyre compared to the front is going to have more effect on centre diff wear than having a tyre with a couple of mm tread difference. As long as you’re not running two completely worn tyres on one axle and two brand new ones on the other. The diff should be designed to take it, that’s the point in it.

 

[portland_bill]

General concensus is that understeer (front letting go) is easier to handle than oversteer (rear letting go). Even RWD cars are mostly set up to understeer these days, and FWD has that tendency anyway. As we moved to FWD, numbers in ditches has reduced. A rear slide can be fun, but requires some skill, and lots of space, best kept for old airfields.

Sometime, I wish to change mine to all-seasons, which can be done in pairs, but is best as a set. It hurts to throw away good tyres, so I'll be swapping them around to attempt even wear, and all worn nicely before the change. Hopefully new tyres before parking in a ditch.

 

[vexorg]

The only time I've had issue with the back end breaking away in a fwd car is when it still has cheap tyres on from when I bought it.

Cheap tyres should be banned outright, I always go for the more expensive end of the scale. And even down close to the wear limit, good quality tyres have no issue on the rear when cornering.

Given the choice, I'd have the better tyres on the front since it far easier to get the front end to understeer in the wet. In general I just replace them in pairs when they get to around 3mm.


I think those that have issue with the rear end stepping out have either cheap types or driving beyond the car's limit.

 

[A3jeroen]

My Abarth has Pirelli's on the rear axle and Vredestein Ultracs on the front. Personally I think yhe Ultracs are better than the P zero nero's. Since the reartires will follow the fronts I think aquaplaning of the rears, before the fronts do, is very unlikely. And having incorrect pressures has way more effect than a mm of profile difference front to back.

gr J

 

[jrkitching]

Given the choice, I'd have the better tyres on the front since it far easier to get the front end to understeer in the wet.

That's your choice, but it goes directly against what the tyre industry considers to be good practice.

And even down close to the wear limit, good quality tyres have no issue on the rear when cornering

That's only true on dry roads. As tyres wear, the aquaplaning risk becomes progressively greater, and at the legal limit, the aquaplaning resistance is only about 60% of what it would be at 3mm.

In general I just replace them in pairs when they get to around 3mm.

That's good practice, and also the limit recommended by most tyre manufacturers (though they do have a vested interest in selling tyres).

I always go for the more expensive end of the scale.

Me too; cheap tyres are generally false economy and are cheap for a reason. Also, a significant part of a tyre's price is taken up by distribution and fitting; you have to pay this regardless of tyre quality. All of the extra cost of a more expensive tyre goes into the quality of the product.

 

[mj2k]

The only time I've had issue with the back end breaking away in a fwd car is when it still has cheap tyres on from when I bought it.

Cheap tyres should be banned outright, I always go for the more expensive end of the scale. And even down close to the wear limit, good quality tyres have no issue on the rear when cornering.

Given the choice, I'd have the better tyres on the front since it far easier to get the front end to understeer in the wet. In general I just replace them in pairs when they get to around 3mm.


I think those that have issue with the rear end stepping out have either cheap types or driving beyond the car's limit.

Not sure if they were Funken Orfuls, Gon Wongs or Ditchfinder Generals, but the only time I've had the rear end break away was on v cheap tyres.

I had a diesel Xsara estate (it was the companion and potential donor for my Xsara VTS) and I was driving it at about 50 on a wet motorway, when everything came to a sudden stop in front of me. The tyres were so bad they defeated the ABS and it began to slide, rear end first, when I braked hard. I just about managed to control the fishtailing and bring it to a halt on the hard shoulder, but the wheels / tyres went straight in the skip after I'd checked the ABS and made sure the issue didn't lie there.

Interestingly when it was running Pug 306 alloys with decent Pilot Sports, it also sorted the handling and it went from being a wooly, floppy thing into being almost as sharp round the corners as it's far more sporty companion.

 

[vexorg]

That's your choice, but it goes directly against what the tyre industry considers to be good practice.

I think that's misunderstood, yes the results of losing the backend are far more extreme, but the chance of that happening is also very small compared to the front end losing grip due to too much power on a corner or bend..

 

[mj2k]

In this particular case when by the sounds of things only a pair of tyres need replacing and the others are fine then I’d just replace the pair and have no concern.

If this is the black abarth with front end damage I’ve seen on another thread (as you mention one tyre being accident damaged) then it will allow you to get the rest of the damage sorted and then later if you feel strongly inclined you can replace the other two for peace of mind.

As for 4x4 cars, a sensible person might replace all 4 every time but in all honesty even having a couple of psi difference in one back tyre compared to the front is going to have more effect on centre diff wear than having a tyre with a couple of mm tread difference. As long as you’re not running two completely worn tyres on one axle and two brand new ones on the other. The diff should be designed to take it, that’s the point in it.

It is indeed, but since I'm now a very low mileage driver (I work from home) I do tend to make full use of the car's performance when I'm actually using my car; the roads round here demand it! :slayer: So I like / need to make sure the car is top of it's game handling-wise; the comparatively poor handling on my Alfa 156 GTA was one of the main reasons I got rid of that breathtakingly-pretty-but-hopeless beast.

Because of the design of the Subaru 4x4 (on manuals it's a viscous diff in the centre and often a viscous LSD at the rear), though it does have 'best of both worlds' for a 4x4 in that it works like a performance system but can happily drag the car up a steep hill covered in 2 inches of snow (been there, done that, sniggered at the stuck Discoveries ), it is quite prone to the diffs overheating on the 6 speed manual, which degrades the viscous fluid. £350+ in parts per time plus a very messy, oily, time-consuming job soon convinces you replacing all 4 tyres at once is a sensible preventative step. I suspect the MK1 Freelander suffered from this issue as well judging by the huge number of failed centre diffs they suffered from, probably others with viscous centre diffs too, though I haven't checked into that.

The older style wet plate LSD (as used in Subaru autos and older performance cars) doesn't suffer from this issue, but with viscous diffs, every slip generates a tiny bit of heat and if they're constantly slipping a tiny bit when you're e.g. travelling the length of the M1 with differently worn tyres front and back, this heat soon builds up. It may only make e.g. 30k difference to the lifetime of the centre diff, but if you're a high mileage motorway driver that 30k can matter a lot.

 

[Piccolo Nero e Bella]

I've been following this thread with interest as I think my car's about due for new rubber. The Potenza's still have a bit of 'meat' on them but are the OEM tyres and are over eight years old now. There's a distinct feel that they're not at their best in the wet.

With the kind of pottering around I do these days I don't need anything flash (i.e. expensive) but perhaps a mid-range tyre price-wise. Is Continental considered of adequate quality?