Costco - credit where it's due

[jaffacake]

Bought our Macan this time last year with 12k miles on the clock from new. It came with, what we can only assume, the original P-Zero N-rated tyres. At the time we picked it up, they looked in great condition with no concern about age/mileage.

I frequently wash the car by hand, which allows me to keep a good eye on the tyre tread. Over time I've clearly noticed as the tread on the fronts, especially the front left, has gone down. No surprise, most of our mileage is local, around time, a mix of t junction turns and roundabouts, 2 tonnes of car cornering at physics defying speed has to wear something somewhere.

I'm always torn with the tyre pressures. A fair amount of our mileage is driver-only to the gym or supermarket. But another fair chunk is two adults, two kids and a bike rack hanging off the tow bar. I can only assume the bikes will lift the nose a little, I can feel the steering may be a little light despite the air suspension. Ideally I guess I'd re-pressure each time we put the bike load on, in reality that isn't going to happen every time - especially if my wife is taking the kids out when i'm at work.

On a wash a couple of months ago I decided that the outer shoulder on both front tyres was becoming visibly worn. It's easy to compare to the rears to see how they used to be. They certainly looked like they were approaching their best before date, although the tyres looked ok across the middle.

I made a decision to apply full load to the tyres, keeping them at the higher pressure. Firstly it made sense with the bikes attached. Secondly, I'd expect that to apply more wear around the middle of the tyre and take less off the shoulders.

Another check last week and I decided this strategy was working well and that the tyres were now clearly visibly worn across the whole tyre. Are they legal? Are they below 3mm? How should I tell? How to resolve if they are?

Shared far too much background there but thought it made a good story in case anybody else wanted to share similar experiences...

Fast forward to Monday this week and I was going shopping at Costco. I remember they did a free tyre health check. I called to confirm and they said just to pull up outside a tyre bay any time before they closed at 8.30pm - so I did.

Was a little busy when I arrived, so I had to wait a while but without too much delay a friendly guy behind the counter asked if I could help. I explained I'd come to check the tyres on the car, specifically the fronts. OK, he said, I'll grab my gear and see you outside.

It was cold and raining but, armed with a bright spotlight and a depth probe he walked around the car one tyre at a time, starting with that front left.

Front left he said was 3.5mm across the middle but 4mm or more on the outer shoulders. Front right was 4-5mm all over and the rears 5-6mm. He explained no concerns today and asked out typical mileage. He concluded we'd be fine for now and to come back mid February for another free check to see how we were going.

I then asked about the Costco tyre fitting policy and what would happen if the fronts were dead but the rears were still good. No worries, he said, they're staggered sizes so no concern with replacing the fronts while leaving the existing rears on.

Not the biggest customer success ever, but just a nice free of charge service that I will happily use as needed to ensure my tyres get replaced at the optimum time. I thought it was well worth sharing for those who might be in a similar place.

Cheers,

Ben

[Connoisseur]

Another Costco fan here, agree with everything said. Competitive prices, usually a deal on offer, knowledgeable staff and nitrogen fill. Have used them for 12 years now across various stores

[SAC1]

I then asked about the Costco tyre fitting policy and what would happen if the fronts were dead but the rears were still good. No worries, he said, they're staggered sizes so no concern with replacing the fronts while leaving the existing rears on.

Ben - here is the recommendation from the BTMA:

"Due to their greater tread depth, new tyres will generally have better grip than the remaining tyres on the vehicle, especially in the wet. This grip differential can lead to vehicle instability under sudden manoeuvres, such as when swerving and braking to avoid a collision. Electronic stability programs reduce this risk but in general it is best to fit new tyres in pairs and to the rear axle. However, where the vehicle manufacturer gives different advice you should follow it."

https://btmauk.com/advice-about-tyres/m ... c803a-b661

Put simply, this is because you can steer the front axle, but if the rears are low on tread depth and so grip particularly in the wet is reduced, then its easy to loose control of the rear axle of the vehicle with the fronts bighting harder. Catching a near 2-ton Macan the more so!

As you are currently running on Pirellis, I suggest that you get a tyre check [all tyre distributors do free ones] at a Pirelli Performance centre. https://www.pirelli.com/tyres/en-gb/car ... ce-centres

My suggestion for the Macan is to replace all 4 tyres when the first one of them is under 3mm and certainly before the legal limit of 1.6mm across 3/4 of the tread area.

[jaffacake]

Ben - here is the recommendation from the BTMA:

"Due to their greater tread depth, new tyres will generally have better grip than the remaining tyres on the vehicle, especially in the wet. This grip differential can lead to vehicle instability under sudden manoeuvres, such as when swerving and braking to avoid a collision. Electronic stability programs reduce this risk but in general it is best to fit new tyres in pairs and to the rear axle. However, where the vehicle manufacturer gives different advice you should follow it."

https://btmauk.com/advice-about-tyres/m ... c803a-b661

Put simply, this is because you can steer the front axle, but if the rears are low on tread depth and so grip particularly in the wet is reduced, then its easy to loose control of the rear axle of the vehicle with the fronts bighting harder. Catching a near 2-ton Macan the more so!

As you are currently running on Pirellis, I suggest that you get a tyre check [all tyre distributors do free ones] at a Pirelli Performance centre. https://www.pirelli.com/tyres/en-gb/car ... ce-centres

My suggestion for the Macan is to replace all 4 tyres when the first one of them is under 3mm and certainly before the legal limit of 1.6mm across 3/4 of the tread area.

Totally agree with everything you said. I'm quite familiar with the recommendations, which I was I queried at Costco. I've always moved the old tyres to the front and fitted the used on the back, but never had staggered sizes before.

If the rear tread wasn't so close to new, I'd be doing all four - they'd make me. They wouldn't fit new on the front and then leave two on the rear with 3mm of tread.

The rears currently have about 6mm and a new summer tyre comes with a typical 8mm - 10-12mm for winters - so the new and used aren't going to be massively different in grip at all, even on a waterlogged road - the wider rears will clear more standing water than the fronts can.

It won't be long after the new fronts are fitted that they'll be even again due to excess front tyre wear. I actually wonder why they fit wider rears on a front engine AWD car when it would appear the rears do so little work.

[On-Track]

It won't be long after the new fronts are fitted that they'll be even again due to excess front tyre wear. I actually wonder why they fit wider rears on a front engine AWD car when it would appear the rears do so little work.

If you select the 4WD display on the MFD you'll see that most of the drive goes to the rear. Apart from that, wider rear tyres are a fixture on all Porsches.

If you spend a lot of time going around roundabouts quickly the left front will get more of its fair share of load. Otherwise, it might be worth getting your steering checked. Just a warning, a four wheel steering check at an OPC is not cheap.

[Nuclear Nick]

Ben - here is the recommendation from the BTMA:

"Due to their greater tread depth, new tyres will generally have better grip than the remaining tyres on the vehicle, especially in the wet. This grip differential can lead to vehicle instability under sudden manoeuvres, such as when swerving and braking to avoid a collision. Electronic stability programs reduce this risk but in general it is best to fit new tyres in pairs and to the rear axle. However, where the vehicle manufacturer gives different advice you should follow it."

https://btmauk.com/advice-about-tyres/m ... c803a-b661

Put simply, this is because you can steer the front axle, but if the rears are low on tread depth and so grip particularly in the wet is reduced, then its easy to loose control of the rear axle of the vehicle with the fronts bighting harder. Catching a near 2-ton Macan the more so!

As you are currently running on Pirellis, I suggest that you get a tyre check [all tyre distributors do free ones] at a Pirelli Performance centre. https://www.pirelli.com/tyres/en-gb/car ... ce-centres

My suggestion for the Macan is to replace all 4 tyres when the first one of them is under 3mm and certainly before the legal limit of 1.6mm across 3/4 of the tread area.

The rears currently have about 6mm and a new summer tyre comes with a typical 8mm - 10-12mm for winters - so the new and used aren't going to be massively different in grip at all, even on a waterlogged road - the wider rears will clear more standing water than the fronts can.

Slightly flawed logic here - the wider rear tyres will aquaplane more readily than the fronts because their increased footprint requires less hydraulic pressure to lift the tyre off the road and the rear of the car is also lighter. Conversely the fronts will resist aquaplaning longer thus promoting oversteer which is harder for most drivers to control.

[jaffacake]

If you select the 4WD display on the MFD you'll see that most of the drive goes to the rear. Apart from that, wider rear tyres are a fixture on all Porsches.

If you spend a lot of time going around roundabouts quickly the left front will get more of its fair share of load. Otherwise, it might be worth getting your steering checked. Just a warning, a four wheel steering check at an OPC is not cheap.

I've checked the display on the MFD but I think the Turbo PP is a little different. For sure, at low speeds, if pulling away gently then most of the power goes to the rear. But there is always power to the front and typically 50% of it most of the time. At 70mph, officer, on the motorway, it's a 50:50 split front to rear.

I'm quite familiar with roundabouts killing front left, most cars I've ever owned. Steering was all recalibrated at OPC recently, takes about 4 hours and certainly isn't cheap. Glad I wasn't paying!

[jaffacake]

Slightly flawed logic here - the wider rear tyres will aquaplane more readily than the fronts because their increased footprint requires less hydraulic pressure to lift the tyre off the road and the rear of the car is also lighter. Conversely the fronts will resist aquaplaning longer thus promoting oversteer which is harder for most drivers to control.

Totally understand your perspective and not going to say you're wrong at all.

My point is that any premium tyre with 6mm+ of tread is not at any significant risk of aquaplaning at all.

IF you have good front tyres not at risk of aquaplaning and rear tyres that are at risk, this isn't a good combination. Exactly the phenomenon you describe and also why you should never fit winter tyres only to the front, even on a FWD car.

However, given their tread depth, my rears won't have a significant risk of aquaplaning at the time the new fronts are fitted, if they were I'd happily replace the whole set.

[jkwade]

If you select the 4WD display on the MFD you'll see that most of the drive goes to the rear. Apart from that, wider rear tyres are a fixture on all Porsches.

If you spend a lot of time going around roundabouts quickly the left front will get more of its fair share of load. Otherwise, it might be worth getting your steering checked. Just a warning, a four wheel steering check at an OPC is not cheap.

I've checked the display on the MFD but I think the Turbo PP is a little different. For sure, at low speeds, if pulling away gently then most of the power goes to the rear. But there is always power to the front and typically 50% of it most of the time. At 70mph, officer, on the motorway, it's a 50:50 split front to rear.

Certainly different to mine. At cruise on the motorway I’d have only 1 or 2 front lines showing. It increases if you accelerate but its never 50/50 unless its in off road mode.

[jaffacake]

Certainly different to mine. At cruise on the motorway I’d have only 1 or 2 front lines showing. It increases if you accelerate but its never 50/50 unless its in off road mode.

Yes. It's a known characteristic on the PP that it's permanent AWD, just too much torque for a single axle.