Should I use tyres narrower than the factory size ?
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  1. #1
    Fellow Frogger!
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    Default Should I use tyres narrower than the factory size ?

    My 2009 308sw 2.0 HDi came with 225/45/17 new

    In the interests of fuel efficiency I was considering 205s [on the 17" rim]

    Questions:

    1. Will it make a difference to fuel efficiency ?
    2. Why does Peugeot spec 225s on 17" rims, is it just looks ?
    Note I see the inside door has 215s for 16" rims but doesn't say anthing about 17" tyre size

    My tyre guy said the 225 will handle better but the 205s may have a small 1%? advantage in fuel efficiency

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  2. #2
    1000+ Posts Fordman's Avatar
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    If the car was here in Aus, I am pretty sure that "legally" you could not go LESS than the placarded width, in your case 215.

    However, be aware that you will have to go up in aspect ratio, ie, you may need a 215/50 or 215/55 to maintain the same or slightly larger outside tyre diameter. If you went to a 215/45 it would have a smaller diameter, and this would have the effect of higher engine revs, and probably cause more loss of economy than you would gain from the narrower tyre. Not that I am recommending it, just pointing out the diameter change may have a greater effect than the width.

    Cheers.
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  3. #3
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    Hi xlink_nz
    Of course it is just for the looks and the impression it gives. That's what selling cars is all about now !

    IMHO I would say fitting a tire that has a load and speed rating suitable for your car will be satisfactory. Indeed I would consider changing the wheels also to get tires on which suit ME. Those fat low profile tires ride like steel wheels and are most uncomfortable to my arse !! A slimmer higher profile tire is probably specified on the base models back in Europe and is OK for the thousands sold there.

    However the fuel savings will not be noticeable most likely. There are some tires which specify that as a feature, but again not a magic bullet for fuel savings.
    Jaahn

  4. #4
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    Identical to a 225/45-17 in circumference is a 205/50-17. So that would be the size to choose if you are set on a change as it would preserve gearing.

    Mind you, I am not persuaded of the merits of a change. One could simply increase tyre pressures by, say, 10% & achieve much the some contact area reduction as a smaller tyre would. With a 45 profile tyre that might lead to comfort concerns but why not try it on your present tyres & see see what you think?

    Personally, I don't care about comfort or about fuel economy. This in became comfort is a trade off against handling crispness & fuel economy is a trade off against wet grip.

    But that's me, not you. If fuel economy is your primary operative criterion in tyre choice, then I'd do three things:

    First, shift to 205/50-17. The contact patch is slightly smaller & a slight economy increase is consequential from this. And, being smaller in area but longer in shape, wet grip is likely to be improved (other things being equal).

    Second, increase pressures on the new tyres by 10%. This will further reduce the contact patch. It will also tauten the structure a bit, increase load carrying capacity & crispen handling response.

    Third, choose an "eco" tyre (an easier task in the smaller size). This will certainly improve fuel economy but there is a wet grip reduction trade off. In 205/50-17 I'd choose the XL variant (load rating 93, not 89) of the Continental EcoContact 5.

    cheers! Peter

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    1000+ Posts bigkev414's Avatar
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    no.
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    care to clarify? (no to what bit?)

  7. #7
    1000+ Posts driven's Avatar
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    Improve economy by increasing tyre pressure, less rolling resistance, but harsher ride

  8. #8
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    Thank you all for your replies

    I went again with 225/45/17 [Toyo NanoEnergy 3 XL]. The main reason being is that I only required 2 tyres and wasn't sure about the rears being smaller than the front for >6 months maybe longer

    I may go smaller when I get the chance to do 4 tyres at once

  9. #9
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    Quote Originally Posted by xlink_nz View Post
    Thank you all for your replies

    I went again with 225/45/17 [Toyo NanoEnergy 3 XL]. The main reason being is that I only required 2 tyres and wasn't sure about the rears being smaller than the front for >6 months maybe longer

    I may go smaller when I get the chance to do 4 tyres at once
    Hmm. I've responded to you in the other thread. Good luck.

    cheers! Peter

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    1000+ Posts bigkev414's Avatar
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    Quote Originally Posted by 4cvg View Post
    care to clarify? (no to what bit?)
    No to 'should I use narrower tyres' to save fuel. In my experience and opinion for what it's worth narrower tyres usually have a detrimental affect on handling. Fuel saving would be negligible unless you did a real lot of kms, and then you have to consider the cost of buying the tyres in the first place. Better to pump them up as you suggested. Nothing scientific to support my opinion, just 45 years of driving experience and just as many cars owned over that time.
    I might act like an idiot, and I might look like an idiot, but don't let that fool you: I really AM an idiot!

  11. #11
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    Thanks. In this case, the main merit of going to the smaller size would be access to an "eco" tyre that didn't trade off too much by way of wet grip. The EC5 would fit that bill but the larger NE3 fitted may be a bit of a worry.

    At the moment Michelin lead the fuel saving pack with the (not widely available in Australasia) Energy Saver + but Conti's EC5 is not far behind & is less wet compromised. These tyres would be notably more fuel efficient than most.

    cheers! Peter

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