Tyre Castellation/scalloping
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Thread: Tyre Castellation/scalloping

  1. #1
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    Default Tyre Castellation/scalloping

    I have 3 Y.O. Continental Conti Comforts on the rear of the 2010 C5. After 48,000kms there is still plenty of tread left. Over the last 12 -18 months however a very annoying sort of "wirring" sound has developed and emanates from the rear of the car. I took it to my local Tyrepower centre, and they removed and inspected the tyres and showed me that the tread blocks on either the inside of the tyre or the outside (can't remember which) were castellated. Tyrepower suggested that "my shock absorbers were worn out/ faulty", but as the C5 doesn't have any in the normal sense, and rides and handles perfectly, I said I doubted that that was the case.

    Is this normal? I know the rear tyres have lasted a considerable mileage (the front ones were replaced with Michelin Pilot Primacy about 12 months ago after 35,000kms), and I never had them moved periodically front to rear because I never wanted to face the prospect of buying all 4 new tyres at $280 each at the same time.

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    So my question is: Is castellation/scalloping on the rear tyres of C5's after a large mileage normal, or do I have a suspension problem?

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    Fellow Frogger! citroenthusiast's Avatar
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    Did you check the balance on the tyres? A badly out of balance tyre may show signs of cupped wear which you might not feel on the rear because of the superior Citroen suspension.
    Cheers,
    John T.

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    Have you had your rear wheel alignment checked. Unlike earlier C5s your car has an adjustable rear end.

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    I ran Bridgestone RE01 (?) after the original Michelins wore out. They rode and handled well but they also developed scalloping as you describe. They became an annoying drone. Once they wore out I moved to Kumho Primacy KE27s (?) and have never had a problem with scalloping.

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    It can also be caused by the steel belt not being quite wide enough for the tread. A condition that may be further accentuated by the rim not being the optimum width for the tyre.

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    Hi
    Back in the dark ages when I worked for a tire company the standard answer for that type of problem on a truck trailer tire was to put it on the drive axle and that will "drive out the problem"!!:0
    So swap them to the front wheels and see if that helps until they need replacing.
    Jaahn

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    COL
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    Quote Originally Posted by jaahn View Post
    Hi
    Back in the dark ages when I worked for a tire company the standard answer for that type of problem on a truck trailer tire was to put it on the drive axle and that will "drive out the problem"!!:0
    So swap them to the front wheels and see if that helps until they need replacing.
    Jaahn
    If it doesn't fix it, it will certainly help to wear them out quicker.
    jaahn and CXVingtCinq like this.
    Regards Col

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    Thanks to everyone for the replies. Yes, I guess the tyres should have been swapped around more often. Tyrepower checked the balance on all 4 wheels and they were ok. They wouldn't put the rears on the front because they reckoned the castellation would now cause vibration, so although the rears are not nearly worn out, I'll just get a couple of new ones, probably go for Michelin Primacy 3 ST, although I might investigate the Kumho Primacy. The Michelins I have on the front are wearing very well and are very quiet. Rear suspension should be in alignment. I recently paid out some huge amount to Allpike Citroen for major service in which all that sort of thing was checked. A friend visiting from the UK a month ago has a Lexus, and said it was suffering from the same problem. He picked the noise in the C5 within a few hundred metres!

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    It's not entirely clear to me what tread deformities you are reporting.
    One can get "cupping" - uneven & irregular tread depths - from weak dampers. One can also get chamfering of tread elements from toe problems. One can further get outside edge chamfering from leading edge wear on cornering. Reverse the rotation direction (which I recommend - reason on request) & one will then chamfer the other edge & this gives a domed effect to these tread blocks in time. That is actually the closest I can get to "castellation" & it is only manifest on the outside edges but it relies on you having had the ComfortContacts left/right swapped. I also can't see it as a source of the noise you report.

    Anyway, the CC5s are to be discarded & the question is: what next?

    I don't much favour the Primacy 3 ST (& certainly recommend against the CC5) but you already have a pair & I very much suggest that you get the same tyre type as the front, & put the newest tyres on the front (reasons available upon request).

    Ordinarily, with mismatched tyre ages, I suggest leaving the older ones on the front. One reason is to wear them out as soon as possible in order to get to a better matched 4 as soon as possible. But your fronts aren't that different in age to what you'll fit. There is also your irregular rear wear issue to even out. So, rotate.

    I recommend a rotation at least every oil change. A good sequence is an X rotation alternating with an H rotation.

    I think that you should reconsider your "replace only 2 at a time" practice. This gives you a permanent sub-optimum situation of front & rear tyres of different age & possibly different characteristics (as you now have). Better is to budget such that all four are changed at once & rotated until the next "all four" change.

    cheers! Peter
    Last edited by 4cvg; 23rd April 2017 at 10:16 PM.

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    Thanks for that detail, Peter. The inside and outside blocks on each of the rear tyres are slightly chamfered so that the leading edge on each tread block is slightly higher than its trailing edge. This, I am told, is what is causing the noise problem. I can't simply swap the tyres left to right because as I understand it they are asymmetric, and would have to be taken off each wheel and turned around. This may make no difference to the noise anyway. But it's annoying because there is quite a lot of tread left. The service manager at Allpike Citroen in Perth (to whom I have spoken by phone) suggests (reasonably enough) that I bring the car in for a check. Well, I guess I'll have to but it's a 600km round trip, so I'll wait until I have a few more things to do. He felt it was more likely to be faulty damping --- don't know whether you can call it "faulty shock absorbers" on a C5 --- than misalignment, as the castellation is the same on both rear wheels. A major service about 6 months ago did not show up any faults. When I do get around to buying 2 new tyres (which may be pretty soon) Allpike suggest I try some Pirelli Cinturato P7s, but I have a suspicion that they may not be as quiet and comfortable as the ride the Michelin Pilot Primacy 3ST's give me on the front, although I think there that model has now been replaced with something else. Maybe I should try swapping the rear wheels with the fronts and see whether I get vibration as the tyre bloke said I would. That may finally wear the Continentals out and the irritating "wow-wow-wow" sound they give on smooth roads at the moment may not be as obvious.

    Allen

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    I meant to ask why you don't favour the Primacy 3ST. They certainly sharpened up the steering after the Conti's, and I gather that Michelin and Contis are the 2 brands Citroen recommends. There may be commercial reasons for this of course. Michelin did own Citroen once, I seem to recall. What do you suggest? I suppose I should match the fronts with the rears until I wear all 4 out at the same time. It's the cost of replacing all together at around $1,200 which puts me off.

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    X and H patterns are fine but you do it in particular pattern

    Rotating Tyre: What You Need To Know | Blackcircles.com

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    C5 booked in for 85k service and rear suspension check on 22/5/17. Will post results, which should reveal whether castellation was caused by shock absorbers (?)/spheres, alignment or simply tyre wear, the latter possibly caused by my not rotating the tyres front to back over 47,000kms/3 years.

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    Quote Originally Posted by Allen View Post
    I meant to ask why you don't favour the Primacy 3ST. They certainly sharpened up the steering after the Conti's, and I gather that Michelin and Contis are the 2 brands Citroen recommends. There may be commercial reasons for this of course. Michelin did own Citroen once, I seem to recall. What do you suggest? I suppose I should match the fronts with the rears until I wear all 4 out at the same time. It's the cost of replacing all together at around $1,200 which puts me off.
    reason? - mediocre wet braking (better than the disgusting CC5 though - it would be some other Conti which Citroen would be recommending - the CC5 is not a European line); they are a good tyre but one can do better.
    Apart from poor wet grip, the CC5 is notoriously soggy handling & the ST is rather crisp & having crisp at the front & soggy at the rear is a tyre type imbalance which would give crisper turn in & a more dramatic tuck in upon lift off.

    despite judging that better tyres are available in the class than the ST, my recommendation is still to fit two STs and make sure you rotate (I still recommend X followed by H but the blackcircles' chart for fwd will do exactly the same job in two rotations and you might find it easier to remember)

    It's not as if the ST is some sort of Chinese DeathDealer SlipQuick GT rubbish that you should quickly dump. Next tyre purchase should be for 4 (save up now!) & best to wait & see what is available then.

    cheers! Peter
    Last edited by 4cvg; 6th May 2017 at 01:09 AM.

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    First, nothing wrong with swapping an asymmetric tyre from left to right; directional ones are not suitable for lateral swapping but one can reverse direction of rotation on any asymmetric ones like the CC5 - I'd try that.

    Second, I'd raise pressures at the rear by 4 psi. Two reasons: one is that the chamfering on both inner & outer blocks sounds like an under inflation problem. The other reason is that, given the tyre structure imbalance with the front, it ought to make the vehicle more stable on lift off.

    All tyres wear in a way that chamfers the blocks - especially on the outside. The leading edge as the block hits the road is ground down & the trailing edge feathered. The effect is exacerbated by low pressure. Either you misreport your tyres (reporting the appearance at the tyres top?) or they have been laterally rotated recently (reversing the order of rotation).

    cheers! Peter

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