Buying a Renault Duster. - Page 4





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  1. #61
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    Default Re: Buying a Renault Duster.


  2. #62
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by XJ Junky View Post
    If you lift a Duster then you bought the wrong car.
    I missed you Now convince Alex to come back
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  4. #63
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by Butch Dassie View Post
    My concern with going 10% wider is the decrease in fuel consumption from the increase in road friction.
    Iím not sure I 100% understand this. Are you saying wider tyres increase rolling resistance. This then gives worse fuel consumption?

    If so do you have any literature on this?

  5. #64
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    Default Re: Buying a Renault Duster.

    Yes. A larger contact patch gives beter grip for the same reason.

    So a 255 tyre has 8% or so more contact than a 235, so the rolling friction will increase by that.

    This does not mean your fuel consumption goes up by the same amount.

    There is a reasoning that wider tyres do worse in loose sand, as you have to push more sand in front of it. Rather go for higher profile to increase the diameter and lengthen the footprint when you deflate.

    I'm not convinced it makes much of a difference if you only go wider by one size. You then have more flotation without deflation.
    If my post insulted you, wonder where the smiley went .

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  6. #65
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by BruceB View Post
    I

    If so do you have any literature on this?
    Just Google this topic and you will find factual tests on this matter. Ask any rally driver and they will confirm this.

  7. #66
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by XJ Junky View Post
    But itís not even close to stock.
    Strange - bodywork looks standard.
    If you make a noise or need music in the bush or on the beach, youíre missing the point.

  8. #67
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    Default Re: Buying a Renault Duster.

    Space frame with fully removable body most likely

  9. #68
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    Default Re: Buying a Renault Duster.

    See here, some footage of yesterday's Bronkhorstspruit 400 rally.

    https://m.facebook.com/teamelfrenaultduster/
    Last edited by JJJ; 2020/08/16 at 10:07 AM.
    If my post insulted you, wonder where the smiley went .

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  10. #69
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    Default Re: Buying a Renault Duster.

    My Nephew used to be a Techie for that team. Nissan VK 5.6 engine. Space frame Rally Car. Started out with Nissan Navara shell on that frame..



    Attachment 584497
    Last edited by grips; 2020/08/16 at 10:15 AM.
    It is not what you buy its what you build.

  11. #70
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by ekkekan View Post
    Just Google this topic and you will find factual tests on this matter. Ask any rally driver and they will confirm this.
    Well I donít know any rally drivers and I doubt any rally driver would care about rolling resistance. In a field where you do care and itís very noticeable, road cycling itís become obvious that rolling resistance goes down the wider the tyre, all other factors kept the same.

    Thatís why Iím asking.

  12. #71
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    Default Re: Buying a Renault Duster.

    Bruce - there was a proportionate increase in fuel consumption when I fitted wider tyres.

    AT tyres tend to be heavier that HT tyres but the increased rotational mass doesnít really affect consumption much.

  13. #72
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by PRA View Post
    Strange - bodywork looks standard.
    The panel are fairly standard.....sort of. The rear door is just a big fuel cap

  14. #73
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by JJJ View Post

    There is a reasoning that wider tyres do worse in loose sand, as you have to push more sand in front of it. Rather go for higher profile to increase the diameter and lengthen the footprint when you deflate.

    I'm not convinced it makes much of a difference if you only go wider by one size. You then have more flotation without deflation.
    If youíre pushing sand then youíre doing it all wrong.

    Larger diameter tyres have a negative affect on torque.

  15. #74
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by BruceB View Post
    Well I donít know any rally drivers and I doubt any rally driver would care about rolling resistance. In a field where you do care and itís very noticeable, road cycling itís become obvious that rolling resistance goes down the wider the tyre, all other factors kept the same.

    Thatís why Iím asking.
    If one were holding all other factors constant (tyre mass, tread pattern and thickness, tyre compound (sidewall flex and hardness of contact patch), aerodynamic drag, air pressure, deformation, road surface, load, hysteresis, rim size and tyre diameter), wider (with same length) contact patch / footprint (tyre touches the road) provides more rolling resistance / drag.

    You mention road cycling and one has to add a caution that wider bicycle and motorcycle tyres have different contours between manufacturers and tyre sizes. You have to compare contact patch with contact patch. Contours are not really a factor on vehicle tyres.
    Renault Duster 4WD Gen1: No Meow, GC = 254mm

  16. #75
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by XJ Junky View Post
    Bruce - there was a proportionate increase in fuel consumption when I fitted wider tyres.

    AT tyres tend to be heavier that HT tyres but the increased rotational mass doesnít really affect consumption much.
    [QUOTE = Butch Dassie;4454514]If one were holding all other factors constant (tyre mass, tread pattern and thickness, tyre compound (sidewall flex and hardness of contact patch), aerodynamic drag, air pressure, deformation, road surface, load, hysteresis, rim size and tyre diameter), wider (with same length) contact patch / footprint (tyre touches the road) provides more rolling resistance / drag.

    You mention road cycling and one has to add a caution that wider bicycle and motorcycle tyres have different contours between manufacturers and tyre sizes. You have to compare contact patch with contact patch. Contours are not really a factor on vehicle tyres.[/QUOTE]

    Changing from HT to AT I can see having a massive difference due to the construction of the carcass. A robust carcass will have far higher hysteresis losses.

    Were your wider tyres the same construction? Iím genuinely interested, not picking a fight.

    When considering the same construction of tyre where one is wider than the other I would be very surprised if the wider tyre had a higher rolling resistance. I canít believe there would be any measurable difference. Rolling resistance is such a small component of drag in a car in any event.

    [QUOTE = Butch Dassie;4454514]
    ...wider (with same length) contact patch / footprint (tyre touches the road) provides more rolling resistance / drag...[/QUOTE]

    You need to keep all things constant. A wider tyre with the same contact length is running at a lower pressure. Pressure is THE driving variable for rolling resistance. A wider tyre at the same pressure will have a lower contact length, less overall distortion of the carcass, lower hysteresis losses and hence lower rolling resistance.

    Some of this stuff is counterintuitive. Itís taken the cycling industry almost a decade to start listening to Jan Heine (who seems to be the early proponent) that the wider the tyre the lower itís rolling resistance. Ten years ago all road cycling was on 23mm tyres (or less), now Conti have a 32mm road tyre out, and the pro peloton is on 28mm tyres.

    Iím wondering if there is any ďscienceĒ to car tyres, thatís all. So far itís all anecdotal from what I can see.

    Hereís some science on bicycle tyres, which is a good test bench. A top end racing road tyre is under 10W loss per tyre!
    https://www.bicyclerollingresistance...000-comparison

    Obviously this is for hardpack surfaces only. But even on sand the environmental conditions / driving style would flood any effect from a slightly wider tyre.

    What Iím saying is a canít see the width of the tyre having any effect on the fuel consumption.

  17. #76
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    Default Re: Buying a Renault Duster.

    On bicycles and motorcycles, you have a very round tyre. A wider rim will allow the roundness to remain better than on a narrow rim where the tyre tends to roll off the side. On motorcycles, the manufacturers had to change the contour so that in hard leans, the length of the contact patch lengthened to compensate and provide sufficient grip. On some manufacturers, you can feel the bike flop to the side when you lean hard. On these tyres, the chicken strip disappears as you're riding on the edge of low siding. That is, your margin of error is literally non-existent.

    Car tyres are more monolithic. As you are dealing with four contact patches instead of two, the weight is already distributed. Thus, the length of the contact patch doesn't vary significantly when going wider like on a bicycle. You are adding resistance as the contact patch is increasing (due to the additional width).

    Car tyre manufacturers keep their ideas close to their chests. They'd rather talk about road noise and comfort.
    Renault Duster 4WD Gen1: No Meow, GC = 254mm

  18. #77
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    Default Re: Buying a Renault Duster.

    Butch - when I put wider tyres on there was an immediate & noticeable increase in consumption. But like I said, I doubt that the increase in rotational mass had much impact. It was probably more to do with the friction

  19. #78
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    Default Re: Buying a Renault Duster.

    Quote Originally Posted by XJ Junky View Post
    Butch - when I put wider tyres on there was an immediate & noticeable increase in consumption. But like I said, I doubt that the increase in rotational mass had much impact. It was probably more to do with the friction
    Can only agree. When I went from 215 to 245 I noticed same
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  20. #79
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    Default Buying a Renault Duster.

    Quote Originally Posted by Butch Dassie View Post
    On bicycles and motorcycles, you have a very round tyre. A wider rim will allow the roundness to remain better than on a narrow rim where the tyre tends to roll off the side. On motorcycles, the manufacturers had to change the contour so that in hard leans, the length of the contact patch lengthened to compensate and provide sufficient grip. On some manufacturers, you can feel the bike flop to the side when you lean hard. On these tyres, the chicken strip disappears as you're riding on the edge of low siding. That is, your margin of error is literally non-existent.

    Car tyres are more monolithic. As you are dealing with four contact patches instead of two, the weight is already distributed. Thus, the length of the contact patch doesn't vary significantly when going wider like on a bicycle. You are adding resistance as the contact patch is increasing (due to the additional width).

    Car tyre manufacturers keep their ideas close to their chests. They'd rather talk about road noise and comfort.
    Ok so the contact patch has stayed the same length and got wider, so has more area. The pressure and the load have remained the same. No wonder they keep those physics close to the chest.
    Last edited by BruceB; 2020/08/17 at 12:48 PM.

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