Having switched from stock run-flats (195/55/16 to 205/45/16) to Yoko AVS ES100 yesterday for my daily drive, I wondered if the speedo would be off. So I went to the very cool tire calculator at 1010. Low and behold it says the speedo now reads 5% faster, okay, no biggie, but then I get a POP-UP WARNING that I am now "risking brake failure." Did I make a big boo-boo :impatient ? I haven't noticed other tire size threads mention this. Are all you big shots out there who changed to smaller diameter tires while keeping the same rims doing anything with your brakes?

I get the feeling from other threads that a 4.8% loss in diameter is still nothing to get excited about, but I'm the cautious (ok, neurotic) type when it comes to brakes.

 

Presuming that you have not done anything to the brakes that came from the factory, you should be fine. Think about it - the factory sells 205/45-17 tires as part of the package options. I would imagine that if you put in the 205/45-17 tires, the calculator would give you the same warning....

 

Ah, this is what I am learning about... you see, the change in overall diameter from a stock 195/55/16 to a 205/45/17 in your example, 24.4" to 24.3"... is only .74% (vs a decrease to 23.2", 4.8% change in my case yesterday!). The rim diameter in your example got bigger making up the difference. I put your numbers in the computer (1010tires.com) and that's what I got - and that is such a measley difference that the speedo/odo would barely notice it, let alone the brakes.

 

You’ve decreased the outer diameter of the tire and the length of the lever arm that the pavement gets to use to apply torque during stopping. Your brakes will not have to apply as much pressure to reach threshold braking. Of course the disk surface will be moving 5% faster under the pads (not significant). IMO the pop-up was bogus.

 

I’ve thrown different tire and wheel sizes on my 02 MCS for 3 years now for both street and track and have never given a thought to it screwing with the brakes or causing a failure with them.

Drive you car, be happy, you’re safe.

 

.

 

Good ol' SNDWAVE, thanks dude .

 

Do not worry about it, I had wider tires on another vehicle, my 2003 GTI, it has not messed the brakes, plus a frined of mine did the same application on his 03 MCS, like yours, no problemos...

BEING A "HOT-SHOT" IS PRICELESS