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.

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    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.

    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?

  2. #2
    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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    dvr
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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 likes 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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