Replacing tyres - and Fuel Economy

Paul, it’s a 2002 Peugeot 307 diesel. Runs perfectly despite high mileage.

In which case €133 is not too bad price-wise for two tyres, so that’s something anyway.

Thanks for that, Paul. I can sleep easier now.

Not if the tyres are compatible, as they would have to be if they both comply with the vehicle manufacturer’s specification.

That includes making sure that they are both summer/winter spec.

Well…can anyone advise me on this point…

My car has just failed it’s C.T due to,the fact that my four new tyres (michelin energy) are a Q which means they are under the potential ,speed of my Citroen Picasso. I need a T or V.

This is now law in france that your tyres have to meet the potential speed of your car even if doing that potential speed means you break the law. Bizarre! And expensive as these tyres are not worn very much. So the moral of my tale…make sure when replacing your tyres ( especially if buying on the internet like I did) they are correct for both the weight and speed.

The vehicle handbook is the guide to correct tyres. I have to admit to never having understood the high speed rating especially on my Renault which could only achieve the speed of launched off Beachy Head.

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Q is pretty low though - only 160kph and I wouldn’t think was fitted as original equipment on many vehicles (even those which would only attain that speed if pushed off a cliff as John suggests).

Are they anything special - winter tyres for instance?

Just checked - they’re a general summer tyre, supposedly with good fuel economy.

I’m a bit puzzled though - looking at the Michelin web site the only speed ratings the Michelin Energy seems to be offered in are H(230kph), T(190kph), V(240kph) and W(270kph) - not sure how you ended up with a “Q”?

Who advised you they were suitable for the vehicle - probably your first port of call for recompense.

Ah, right - must have been the Energy E-V which, as the name suggests are designed for EV’s

https://www.michelin.co.uk/auto/tyres/michelin-energy-e-v

They weren’t suitable for your car - as you bought online it might be difficult to make a claim but whoever fitted then should have advised they weren’t appropriate for the vehicle.

Thanks Paul,

I bought them on line through pneusonline and put in my car details etc, these came up amongst others and I thought they seemed pretty good as I know the make, they were a mid range price (75€) not the cheapest and certainly not the most expensive so I thought they would be okay.

Since found out they are for electric cars lol! So, will just put them to one side and if and when we are forced to buy and electric vehicle, at least I have a spare set. -)))). Thank you both for your replies,

Yup, spot on Paul…electric car!

(https://www.honestjohn.co.uk/forum/post/index.htm?t=43529

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Hmm, maybe a call to the manufacturer? EV’s as they have instant max torque, can destroy the std ICE vehicle tyre structure hence a stronger tyre is needed. The manufacturer maybe able to confirm in writing that these exceed the requirements for your vehicle.
CT persons are just robotically going through the motions without applying any actual sense or knowledge potentially.

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I think John is right in stating there is probably no safety issue but there could possibly be a problem with insurance if you have to make a substantial claim. Insurance assessors love to find a get out.

Having said that, you could always try another CT testing station.

Was a class IV MOT tester from 1967 to 2000 in my previous life and was called a number of things in that time… but never a robot!

But you are not French :grinning:

Possibly but this does not sound like an area where one CT station will give one answer and another CT station will offer a different opinion - the regulations appear to be clear (equal to or higher to rating on manufacturer’s original fitment) and Q is definitely not higher than T in this case.

If Elaine put the car details into pneusonline correctly (and car, rather than manually ordering a rim/profile size) then I’d argue they are liable, though I also think that whoever fitted them shares some responsibility for not checking they were suitable.

Of course it could be pretty hard to prove - the best chance would be that the chosen car was detailed on the invoice but I suspect that it won’t be and that it will just have the size.

Failing that I’d put the details into pneus-online again and see if the EV tyre comes up - if so take lots of screenshots and contact the customer services department.

Keeping the tyres in the hope that one acquires a vehicle to match seems a long shot to me, I’d probably just try to get a decent price on eBay.

:+1: I agree.

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My initial reaction too was that differential issues due to mixing new and worn tyres was twaddle. However, I just saw this quote on Pistonheads (the journal of record for… eh Petrolheads) “With some all-wheel drive cars you’re in dangerous tranny wind-up water if you don’t change all four tyres at once, but the Haldex system used by Volvo since 2000 gives you more latitude”.
My wife had a new Discovery for three years in the mid ninties (dreadful reliability) cars and we on our second new 4X4 Tiguan here in France with no problems but maybe there is an issue. Torsen vs Haldex?
https://www.pistonheads.com/gassing/topic.asp?t=1833197&utm_campaign=enews%20forum&utm_source=Sailthru&utm_medium=email&utm_term=Forums%20Recent%20Engagement%20Smart%20List

I must admit this issue has been at the back of my mind as well and I did a little reading on the basics of limited slip diffs.

I’m pretty certain that there is no issue with a standard diff - they should be able to cope with different RPMs on the output shafts all day every day - it’s why they were designed.

But standard diffs have a weakness - they can only “send” the same torque to each wheel - which means if one wheel loses traction it will spin at high RPM but very low torque - this means that too little torque can be transferred to the remaining wheel (the one with  traction) to actually turn it. So a lot of modern cars have limited slip differentials.

Furthermore the Pistonheads article was describing an all-wheel drive system - these have three diffs (between the wheels on the same axle and between axles), often with electronic control and the ability to tune the diff to alter the balance between front and rear wheels.

If I have it right (Mark could perhaps let us know if not) a limited slip differential does not have independent axles to each wheel but links the two halves into a single axle with friction material which allows some slippage between the wheels (hence limited slip) - this allows full torque from the engine to be applied to one wheel even if the other has lost traction. However in this scenario, or even when cornering one axle’s friction drive has to “loosen up” to allow each wheel to turn independently - so I think that even limited slip diffs across one axle should be OK with a bit of persistent difference in the rolling diameters of the tyres on each side.

That just leave all-wheel systems with complex electro-mechanical diffs - I guess they could struggle with a permanent RPM difference between front and back axles and benefit from all four tyres being changed at the same time - but even those can’t guarantee that a set of tyres installed at the same time will all wear at the same rate so I’m inclined to think “change all tyres together at the end of their lifetime” is probably OK advice but “change all the tyres when one suffers irreparable damage after 2000km” as expensive overkill.

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The bad news is that pneus-online does not offer search by vehicle make/model or registration number - unlike many of the UK online tyre retailers.

You can search by tread width, profile height and rim diameter, then add things like general vehicle class, speed and load rating but, essentially, you have to know the tyre size that you want.

Sorry Elaine, I think a new set of tyres and eBay for the old ones is your only way out.

Yes, there’s no issue with two wheel drive LSDs, They were de rigueur on performance cars until using the ABS and traction control sensors and selective braking overtook them on most road going cars. My Plus 4 has a LSD because it has no ABS or traction control. Even with the LSD it can fishtail on a damp surface. The issue seems to be that a 4x4 haldex set up can cope but Torsen less so. Seems VAG use both systems So Maxime’s tyre man may not have been talking total cobblers.

Here’s a video of how selecting the dif locks on both affect traction.

My 2017 Tiguan also has a front wheel bias in “normal” mode that my 2013 Tiguan did not. It’s slightly annoying because on slippery surfaces there’s a discernible lag in transferring power to rear wheels.