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Discussion Starter #1
Hello,

Last Friday I bought my first set of four replacement tires. I got Pirelli P400 tires to replace the original Goodyear Integrity tires which lasted 37,500 miles.

Since Friday, my Prius has seemed very sluggish, even on the highways where I usually get a very smooth ride. I often feel like my Prius is in low gear, but the dash indicator and the shifter are both in the D position. It also seems as if the electric motor is engaging more.

Do tires need a break in period, and is this behavior typical for tires that are not broken in?

I know from reading messages here that tires do affect MPG, but can new tires make a car drive noticably more sluggish? I have to press on the gas pedal more than I used to. It takes a real effort to get up over 55 miles per hour unless going downhill. This is not how my Prius used to drive.

Thanks for your advice.

Maurice Frank
 

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Tires do need a break in. You probably forgot about the early driving on the OEMs, since the whole car was new, but you had a break in for a few thousand miles, and then another few after the first time you rotated the tires.

Whether that accounts for all of what you are experiencing, I'm not qualified to say (although that rarely stops me, in most cases). ;)
 

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Pirelli's are noted for being about the best tire you can get for wet pavement. They use a must softer grade of rubber compound. But of course with the added "stickiness" you have to pay the piper with much higher tire wear. Haven't heard that they lower milage but I can see where they could.
Pretty hard to beat Toyota"s choice of OEM's for simply milage.
 

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Assuming you got the same size tires, the only thing I can imagine this points to is proper inflation, or a significant difference in inflation from your Integritys. Although, as hyperion states, softer rubber could also make a difference.
 

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didja remember to put air in them? 4 flat tires can cause a hefty drag :wink:
 

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Hi Maurice!

New tires need several hundred kilometers to break and get a "rough" surface to build enough grip you used to have with your previous tires.

Your Goodyear tires probably had only 1 or 2 mm of "rubber" left. This made them rather "hard" and "sporty". Your new tires should have 8 to 9 mm - you are riding higher and the "rubber" is moving more. The same effect happenes when you swith from summer to winter tires, which are rather soft.

Tire pressure is important - especially on new tires - put in as much as you can stand.

I just switched from summer tires (Michelin Primacy) to winter tires (Dunlop M3). It feels like driving a much bigger car, the power steering is much easier but also it feels like the Prius puts more "momentum" on the road. It feels more aggresive.

Walter
 

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Sure... new tires have a break-in period. They adjust themselves to the suspension set of the car..BUT... a Prius that strains to go over 55 on level ground..? That doesn't sound like a new tire problem....
What air pressure are you carrying..? ~JD~
 

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Tire Pressure is 35/33 (max)

Hello,

Thanks for all of your replies.

The tire pressure is 35/33. According to the tech who installed them, this is the maximum rated pressure for this tire. I tried checking the Pirelli site but have not yet found any specs to verify this.

Also the tires were filled with Nitorgen, not regular air. The tire store said Nitrogen does not expand and contract with air/tire temp as does regular air, and it leaks less. Not sure if this is a factor or not.

I drove with 42/40 on my OEM Goodyear Integritys.

Maurice Frank
 

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max pressure rating should be on the sidewall. Running at that much lower than you were on the Integrities will make you feel draggy.

The draggy feel will improve with break-in...give it at least 1000 miles. I experienced much the same when I put on my hydroedge. I still can't glide as far as I did on the Integrity LRRs, but it isn't bad and the handling improvement is well worth it.
 

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Tires & Mileage

Before you get too many miles on the new tires, suggest that you go back to dealer to see if he has an equivalent tire rated at higher psi (e.g., 44 psi). That will allow you to pump up tires to higher pressure. Most tire dealers will exchange new tires with only a few miles on them at no cost, if you buy another tire from them.

I specifically got tires to replace the OEM's that were rated at 44 psi so I could pump them up. 35 psi max will probably never match the mileage you were getting on the OEM tires.
 

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Maurice Frank said:
Hello,
It takes a real effort to get up over 55 miles per hour unless going downhill. This is not how my Prius used to drive.
An effect as large as you claim cannot be explained by new, but properly functioning tires - unless you put on really tall swamp buggy tires, and 55mph indicated is really 90mph now.

Have you noticed a drop in MPG? When you coast, does the car not coast as far as it used to?

If the effect is really as large as you claim it is, I'd suspect something done by the mechanics who changed your tires. For instance, maybe they accidentally damaged a front brake caliper while putting your wheels back on, and now it's sticking and causing drag.

Also check the temperature of your wheels after a drive. If something is soaking up all the energy, it's probably being turned into heat. Maybe your parking brake is stuck on after the tire change. You'd be able to tell because your rear wheels would be hot after every drive.
 

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Re: Tire Pressure is 35/33 (max)

Maurice Frank said:
Also the tires were filled with Nitorgen, not regular air. The tire store said Nitrogen does not expand and contract with air/tire temp as does regular air,
Of course it does.

Anyone who's taken high school chemistry knows the ideal gas law, and the equation PV = nRT.

Fer chrissakes, air is 78% nitrogen.
 

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Also, check your parking brake, sometimes that can be partially depressed enough to cause drag but not fully engaged.
 

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Assuming you put factory size 185/65-15 on, the Pirelli P400 Touring tires are 2 pounds heavier than the factory-supplied Goodyear Integrity tires (19 pounds vs 17). This is a 6% increase in total wheel+tire weight. Any increased unsprung weight will cause the suspension to feel more sluggish, and more energy is required in order to get the extra weight spinning. Some tires come with softer sidewalls for a better ride, which results in slightly less responsiveness when steering. This could be the cause. It's all I can think of so far.
 

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I guess Toyota engineers designed this little "gem" as a package including the tires.
But the guy on the street will always think "he can make it perform better."
Thats the reason for an aftermarket.
It's always fun attempting to out design the experts.
Usually you can get by without doing any damage to performance, (but then again)
 

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It's got to be an option that will cost you a few more bucks. They are excellent rain tires. Just not so good with the MPG.
Are the standard furnished with the car "Goodyear Integrities?"
I've got to believe that Toyota went with the Goodyear and the tire size and air pressures for performance. (I'm sure higher pressures are better for milage but at the cost of traction and ride comfort no matter what you imagine.) I believe the larger size wheels were chosen for the European models for brake cooling for the rear wheel discs. Just a guess.
 
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