Unusual Tyre Wear C5 X7

[RichardW]

A lot of modern cars with ESP intervene gently before you realise they are doing it - it's very possible that the car is 'helping' you by applying rear brake force to get it around corners and this is contributing to higher tyre wear. Given your past driving experience, my guess is that you carry a lot of speed through corners just the sort of behaviour that the car is likely to intervene against. I understand that many Q5/7 owners are surprised that they get through a set of (very expensive!) discs and pads every 20k miles or so still, how else do they think a 2 tonne SUV handles like a sports car????

[osx]

Told you so

Lol, out of interest as you have a similar car have noticed a similar trait?

Not to the degree you describe but certainly much different compared to the other family cars where I always had to replace front tyres first.

[Peter.N.]

The extra rear brake application sounds OK in theory except that the rear brakes only normally apply about a third of the braking effort and even if they have increased it on this car it can't be by much otherwise the rear wheels would lock up as most of the weight is thrown on to the front ones in braking, also if you only brake gently as I do, you are still doing most of the braking with the front wheels and they also apply the power and steer!

Interesting one, maybe some input from others who run the same car would be helpful.

Are you sure you haven't changed them round and forgotten about it - its the sort of thing I would do.

Peter

[vborovic]

I haven't experienced anything like that so far on my car, did a total of 13000 miles after I bought it, and the tyre wear (winter ones and summer ones) seems constant ... as for the rear wheel brake dust build up DickieG was talking about, in my case that's not true, the front alloys are darker than the rear ones, by 30-50% on average ... I don't have the electric brake and the car is not hydractive, but I don't think that should make much impact to the braking system and the wheels ... DickieG's car should be a tiny bit heavier than mine, due to having a 2.2 opposite mine 2.0, but that's a small difference compared to the overall heavier car ... I'm known for heaving a lead foot, and the curves aren't slowing me down by much (when I feel like it), but even with all that, I never noticed that my driving style is having negative side effects (disregarding slightly higher fuel consumption) ...

[DickieG]

A lot of modern cars with ESP intervene gently before you realise they are doing it - it's very possible that the car is 'helping' you by applying rear brake force to get it around corners and this is contributing to higher tyre wear. Given your past driving experience, my guess is that you carry a lot of speed through corners just the sort of behaviour that the car is likely to intervene against.

I don't know what you mean a good point to raise though as you are correct about how ESP works although having said that on most cars when ESP is activated the orange light in the instrument panel flashes which I haven't observed happening on my car to date. Most of my driving with this car is basically cruising (average consumption on the dash shows 47.8mpg) but with your suggestion in mind I'll turn off the ESP and see if the brake dust situation changes in any way.

Are you sure you haven't changed them round and forgotten about it - its the sort of thing I would do.

Possible but no I haven't

If you where braking hard at the back you WOULD go light on the front and it would feel strange, I don't see that one.

I find the X7 exactly the same as other cars in brake bias. X7 has Bloody good brakes when fitted with Mintex pads

The brakes feel perfectly normal when compared with other cars and I drive quite a wide variety of cars, vans, HGV's PCV's on a daily basis.


I don't know if it makes any difference but my car is fitted with the optional factory fitted Carlos Fandango wheels with 245/40 R 19" tyres, the design of the wheels is very "open" as in you can put your hand right inside the wheel when cleaning them so it'll be very easy for brake dust to escape onto the face of the wheel.

[vborovic]

You can turn off the ESP on the dash button, but it will forcibly kick in after you reach 30 MPH or more (maybe even on lower speeds, can't remember exactly) ... unless you want to disable it with Lexia (if it is possible to do so) ... the opening of the alloys could be a factor that lets more dust on the front side of the wheels, but if all 4 alloys are the same, there isn't any reason why the rear wheels would be dustier than the front ones ...

[DickieG]

You can turn off the ESP on the dash button, but it will forcibly kick in after you reach 30 MPH or more (maybe even on lower speeds, can't remember exactly) ... unless you want to disable it with Lexia (if it is possible to do so) ...

I didn't believe the 30 mph thing you mentioned until I tested it for myself last night, crikey how nanny state is that?

opening of the alloys could be a factor that lets more dust on the front, but if all 4 alloys are the same, there isn't any reason why the rear wheels would be dustier than the front ones ...

Unless some of the dust from the front is being picked up by the rear wheels,,

[Stickyfinger]

Unless some of the dust from the front is being picked up by the rear wheels,,

Sounds like a Citroen dealer explanation to me

I would still suspect something with the wheels/brakes/alinement

[vborovic]

You can turn off the ESP on the dash button, but it will forcibly kick in after you reach 30 MPH or more (maybe even on lower speeds, can't remember exactly) ... unless you want to disable it with Lexia (if it is possible to do so) ...

I didn't believe the 30 mph thing you mentioned until I tested it for myself last night, crikey how nanny state is that?

Imagine the fun I had with that when I tested the car on the snow covered airstrip (there is a topic about that somewhere, half a year or more ago) ... ... without the ESP, the car was all over the place (forced steering and handbrake combo), but once the ESP kicked in, it was like putting the car on the rail tracks ...

[DickieG]

In an effort to add a further development/conclusion to this thread, as I was fitting new rear pads and discs to my C5 on Saturday a neighbour started fitting new pads to the rear of a friends Ford C Max and rather surprisingly the calipers and pads for the C Max and the C5 were exactly the same.

The interesting similarity was that the C Max had only done 20k miles and the rear pads had worn out quicker than the front and likewise the rear tyres were wearing out faster than the front which may lend further substance to the theory that maybe on newer cars the rear brakes do a greater degree of braking than used to be the case.

[Stickyfinger]

I still cannot see it, the optimal settings for Cars has been the same (+/-) for years....the physics of front/back brake bias has not changed neither has the need for 4 small bits of rubber to grip, if Ford and Citroen have changed it best call Old Prof Hawkins ASAP !.....it would be a very big change to alter the effects that much.

Whilst cleaning mine the other week I had all the wheels off. The pads were changed at the last service, the pads are normal, front more than rear, the same is true for the set of Pilots, changed as a set some 6 months ago, more front than rear.

??

[DickieG]

I still cannot see it, the optimal settings for Cars has been the same (+/-) for years....the physics of front/back brake bias has not changed neither has the need for 4 small bits of rubber to grip, if Ford and Citroen have changed it best call Old Prof Hawkins ASAP !.....it would be a very big change to alter the effects that much.

I'm left wondering whether the brake balance has been varied on light brake application, after all this would reduce the amount of front end diving and with electronics doing all manner of clever things with braking and stability systems it offers engineers opportunities to shall I say play! Obviously at anything more than light brake application the balance would need to favour the front end as that's where the vehicles weight is transferred towards.

One big factor in the question I'm posing is driving style, I very rarely use even moderate braking as I slow the car using acceleration sense and only use brakes for the last few yards to actually stop the car.

Other than being able to put the car on a four wheel brake testing roller or speak to a braking design engineer it'll be difficult to get the definitive answer.

[vborovic]

I've tried looking in the braking system in the service documentation, hoping to find a clue of brake/weight distribution, but didn't have any luck so far ...

[Stickyfinger]

any MOT / TUV testers out there ?

[Bob L'eponge]

For what it is worth, I have a 2009 1.6 Hdi 'X7' C5 and the tyre wear on my car is also very even, front to rear. I am also a very steady driver who rarely brakes hard. I have just put on my winter tyres and can't really see any difference in the amount of tyre wear that my summer tyres have developed. I have had cars in the past that ate front tyres at twice the rate of the rears, or more.

With regards the front / rear braking balance. I think that older brake pressure regulation systems were pretty crude and overly-paranoid, reducing the rear braking effect rapidly and more than was really necessary, so as to be certain to avoid skidding. I would think that modern ABS and ESP systems are much more able to use all of the rear tyres braking potential. Maybe!