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Help For New Rims & Tires

Discussion in 'Modifications' started by Redders, Jul 3, 2012.

  1. Redders

    Redders Copenworld Newbie

    Joined:
    Sep 19, 2010
    I've been driving my copen for about two years now and am still absolutely loving it. Besides a new grill, I haven't yet done any modifications to it so it's fully stock, though I've been waiting for my tires to wear out so I have an excuse to change to new ones, with new rims to go along with them. I've always thought the copen looks way better with a set of wheels that stick out at the sides a little and have been itching to get some.

    My question is, what will be the effect on the performance of the car, specifically the pick-up, if I change my rims to a set of light weight ones (say 4-5kg) and a wider set of tires, either 185 or 195 width? Will acceleration from standstill require more effort or will it be the other way around?

    And how heavy are the stock rims? I've heard that they are pretty heavy but can't seem to find any hard facts on this.
     
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  2. hue-vashon

    hue-vashon Copenworld Newbie

    Joined:
    Mar 27, 2012
    rims & tyres

    Hi Redders

    I have been planning on doing the very same. I think the Copen would look much better with slightly wider wheels. I was toying with the idea of gloss black rims on my black 0.7 Copen.

    To answer you question about acceleration, there are a few things to consider, the mass/weight of the rims and tyres and the added grip. If you usually spin your wheels when you pull away then the wider tyres will allow you to accelerate more quickly owing to the added grip they will offer. The mass of the wheels will have some effect on the acceleration as they will require less energy/torque from the engine to get them turning. The final consideration the the overall circumference of the wheel, if you increase the diameter, and therefor the circumference, you will increase the top speed for a given RPM, if you decrease the diameter/circumference you will decrease the top speed but increase the torque. Any big changes will therefore show different from actual speeds and distances on your ODM, sometimes up to 3.5%

    Keep us posted
     
  3. Redders

    Redders Copenworld Newbie

    Joined:
    Sep 19, 2010
    Thanks for the reply hue, really got me thinking.

    I'm driving a 0.7 copen myself. I'm probably getting 15 inch rims if I do change them, so it won't affect the overall diameter of the wheel. I'm considering the SSR Type-C now, they should be much lighter than the stock ones so I expect the wheels to be much lighter. Grip is not an issue for me because I don't push the car too hard, never managed to get any wheel spin.

    I'm worried that the broader tires will mean more contact with the ground and will make accelerating from start draggy, or will the reduced weight overcome this?
     
  4. hue-vashon

    hue-vashon Copenworld Newbie

    Joined:
    Mar 27, 2012
    new wheels

    The only increase in drag from broader tyres will be when you put the brakes on, which is a good thing. The majority of frictional resistance will come from the main bearing on your rear wheels although there will be some additional drag caused when turning but we are talking almost unperceivable amounts. these are all considerations for F1 teams as they will be pushing far higher speeds where aerodynamics has a much greater effect. one thing to note is that tyre diameters are subtly different even on 15" rims, a 4.5J compared to a 5.5J rim will give a different circumference depending on the aspect ratio of the chosen tyre. The Copen will allow for 4.5J (factory fitted) to 6.0J although spacers may be required.

    Some useful links below.

    http://www.alloywheels.com/Tyre_Calculator

    http://www.willtheyfit.com/
     
  5. Binz

    Binz Copenworld Regular

    Joined:
    Apr 27, 2012
    Location:
    North Hampshire
    Car(s):
    Copen (plus Suzuki VanVan and Honda CRV)
    re the change in speedo reading. It's worth checking how accurate it is now. I checked mine against gps and found that to do 70 mph i was seeing about 75 on the speedo. So a slightly different tyre circumference may actually make your speedo more accurate.
     
  6. Redders

    Redders Copenworld Newbie

    Joined:
    Sep 19, 2010
    Thanks again for abating my fears, I should be swapping rims once I'm done with a mandatory (by the government) inspection. Using the alloywheels link, 185/45/15 wheels have more or less the same diameter as the stock ones so those are the ones that I'll be hunting for!
     
  7. cmwb

    cmwb Copenworld Newbie

    Joined:
    Jul 24, 2012
    Location:
    Cumbria
    Car(s):
    Copen
    Hi,
    We fitted larger tyres 165/65 16 to the stock alloys.
    Acording to my GPS the speedo now reads correctly with the larger diameter, and there is a little less road noise.
    There is just enough clearance, slight rubbing on full lock.

    Regards
    cmwb
     
  8. trustafox

    trustafox Copenworld Guru

    Joined:
    Nov 19, 2012
    Location:
    East Mids
    Car(s):
    Yes
    how did you get 16 inch tyres on 15 inch rims?? I thought they would be a big baggy!
     
  9. Adam K

    Adam K Copenworld Guru

    Joined:
    Oct 27, 2010
    Location:
    Worcester, UK
    Car(s):
    Nissan Cube Kaizen
    :D Let's hope it's a typo!
     
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