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Quick question about tyre speed ratings.

Discussion in 'Bodywork, Tyres, Wheels & Trim' started by Tashman, Sep 13, 2017.

  1. Tashman

    Tashman Senior Member

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    Your Mercedes:
    W123-300D, W123-240D, 507D campervan, W210-E220CDI, W114-250
    Next week I am looking to buy 4 new tyres for my car.
    The tyre size that the car takes is available to buy in 2 different speed ratings.
    H rated (max 130mph) and V rated (max 149mph).
    The handbook says that both are permitted. The car's top speed is 120mph.

    I tend to drive the car in a relaxed way and I'm more interested in comfort than performance.

    Would I be right in thinking that the tyre with the lower speed rating would have a less 're-inforced' sidewall, and therefore offer better comfort? Or doesn't it work like that?
    Many thanks
     
  2. turbopete

    turbopete Senior Member

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    no it doesn't work like that. the speed ratings are relative to tyre performance. in your position, id buy whichever was most economical for you. the speed ratings are more compound related
     
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  3. oigle

    oigle Senior Member

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    Yep. Both are quite acceptable and the lower rated one will be cheaper normally. Look at tread design and stay away from mono-directional tyres.
     
  4. OP
    Tashman

    Tashman Senior Member

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    W123-300D, W123-240D, 507D campervan, W210-E220CDI, W114-250
    I'm looking at the Conti Premium Contact 5 in 205/65R15 but you can select whether you want the H rated version of it, or the V rated version.
    The price difference is only 30p.

    What I'm asking is: What have they physically done differently to the V rated tyre to make it safe up to 149mph?

    What has it got that the H rated hasn't got?

    Is it stiffer sidewalls?
    Turbopete says no it is a different rubber compound. So is that a softer one or a harder one?

    I'm curious about these things. Thank you
     
  5. OP
    Tashman

    Tashman Senior Member

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    Ok curiosity got the better of me so I've been googling this!

    The change in the tyre's construction that affects the speed rating is something I'd never heard of called the Cap-Ply or Overlay.

    It's not in the sidewall or rubber compound but actually sits underneath the tread layer and it's like a strong layer that tightly holds it all together.

    upload_2017-9-14_15-20-3.jpeg

    Apparently in the days when 70mph was considered very high speed, tyres didn't have this 'Cap-Ply' layer and the extreme centrifugal forces meant that they were more prone to 'grow' or balloon out, often leading to tyre failure.
    The addition of this Cap-Ply has therefore increased the allowable speeds.

    Adding further overlay layers results in higher speed capability. That is, you achieve higher speed capability with just changes in construction.

    And so to answer my own original question.... Both the H rated Conti and the V rated Conti I was considering would feel exactly the same to drive on - both having the same softness of rubber compound and sidewalls. The 'V' just happens to have more Overlay built into it.
     
  6. Arzaam

    Arzaam Senior Member

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    if the price is difference is as little as you say and both types are of equally fresh manufacturing date I would get the V version, I would assume since its rated for higher speed it'll perform better under high temp and consistent high speeds or just be overall better built even though I don't think they'll have any different in ride comfort or even in driving characteristic but it just peace of mind in the back of the head.
     
  7. OP
    Tashman

    Tashman Senior Member

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    Completely agree with you, so just ordered the V rated one.
     
  8. JBell

    JBell Senior Member

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