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30% under mpg rating, any tips?

Discussion in 'Gen 2 Prius Fuel Economy' started by R-P, Jan 27, 2012.

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  1. Britprius

    Britprius Senior Member

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    I have been checking on your Primacy tyres and the only one's I can find are run flat tyres and have terrible economy ratings (F).

    John (Britprius)
     
    #41 Britprius, Jan 28, 2013
  2. R-P

    R-P Active Member

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    They are the ones that were just today the cause for the MOT failure (cracks due to dryness thus (with quite some effort) you can see the canvas).
    205 Energy saver + tires coming soon to replace them.
     
    #42 R-P, Jan 28, 2013
  3. Britprius

    Britprius Senior Member

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    As pointed out to you in another post you must fit all four tyres at that size together or you may have problems with the abs/vsc systems at speed.

    John (Britprius)
     
    #43 Britprius, Jan 28, 2013
  4. R-P

    R-P Active Member

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    Makes sense. Just ordered 2 seconds before reading this post, will put two more on at the first sign of trouble.
    Difference is only 1.78% according to the generic tire-size calculator the Toyota dealer used to answer my question if 205's would fit :) (In short: they didn't know...)

    I know my motorcycle only starts interfering (tractioncontrol) with 30% wheelslip. Undoubtedly the Prius (15 years younger design) will not be that course, but maybe the 2% difference will be OK.
     
    #44 R-P, Jan 28, 2013
  5. Britprius

    Britprius Senior Member

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    If you strike trouble try running the 205s a little softer this may help.

    With the skinny spare on I believe problems start at around 60mph have not tried this myself.

    I did make it clear in my posts that four should be fitted together, but again I have not tried this and the difference is probably less than two new and two worn out tyres on the same car.

    You will not believe the difference going to this size makes to the overall stability and handling of the car. Let us know how things work out.

    John (Britprius)
     
    #45 Britprius, Jan 28, 2013
  6. Steelydev

    Steelydev Junior Member

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    Can anyone tell me how Jim got that cool summary screen on his Multi Function Display? (watch the first video)
     
    #46 Steelydev, Feb 4, 2013
  7. R-P

    R-P Active Member

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    Ran several runs with the new combination of 195's front and 205 rears without issues, including 70mph speeds.
    Yesterday I accelerated onto the motorway and had the stability/traction light come on several times (~60mph). Stopped, kicked all tires, 'switched off' the engine and 'rebooted' my Prius. Haven't seen it since.

    Must have been the different tires, but since it only happened once, I'm trying to convince myself it also could have been the road...
    Few years ago I slid my entire motorcycle sideways a couple of inches making me think my tire was punctured and deflated. I had already called the tireshop for a new tire when I heard news about a truck leaving a 20 mile oil-trail of about a foot wide on the road I had had this 'problem' on!!! And on another occasion a truck lost frying-pan-oil :cry: So it is far from impossible that we get crap on our roads...

    Bottom line I guess will be I buy two more tires as soon as funds allow.
     
    #47 R-P, Feb 10, 2013
  8. Britprius

    Britprius Senior Member

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    This is almost certain to be caused by the tyres. If you accelerate quickly the front wheels will try to spin and since they are already going slightly faster than the rears any slip could cause the traction light to flash.

    John (Britprius)
     
    #48 Britprius, Feb 10, 2013
  9. R-P

    R-P Active Member

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    I know, but I haven't been able to recreate it. And I tried... :)

    So far I think the car has become more unstable. I'm constantly making small steeringadjustments. There has been a lot of wind, but I think it is more than that. So that's another reason for getting 2 more 205's followed by a wheel alignment. Did wonders for the stability of my camper/RV :)
     
    #49 R-P, Feb 10, 2013
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