i just put new tires on my sedan. the old tires were Bridgestone Turenza 215 x 55 x R17. i put on Michelin Pilot Sport A/S 225 x 55 x R17 can someone tell me why the sidewall looks so much bigger, and is this gonna affect my speedo.

 

It will be higher.... because 55% of 225 is more than 55% of 215.
The speedo is affected by rolling diameter (circumference) which will be different with a higher walled tire.

If you increase width, the general rule is you have to decrease the aspect ratio in order to maintain the same diameter.

Your error will be about 1.6%. From what I've read, the acceptable limit is about 3%.



2003.5 Sedan 6MT, Brilliant Silver

 

You can check sizes HERE

<font color=blue>04 Silverstone G35, 5AT, Prem, Aero
ES100 225/45-18 front 245/40-18 rear
HKS & Y-pipe, Z-tube, Eibach, 35%Tints</font color=blue>

 

The only other size (plus 0 I think) that fits on our stock Infiniti wheels is 235/50x17 and this size only comes from a few mfgr's like Michelin, Bridgestone, Pirelli, and a couple more. This plus 0 size however, should give you a wider looking tire on your stock rims and shouldn't affect your speedo. This is the size I will be going for when it's time to replace my stock GY GSD's on my Infiniti sport wheels. I hope this helps.



2004.5 G35-S 5AT Black/Willow - Prem, R. Spoiler, Navi, Sport Wheels, Alum. Pedals, Tint, Z Tube, K&N, Coupe Midpipe

 

The next best thing after 235/50/17 in terms of keeping it close as possible is 255/45/17. This will require at least an 8" wheel though and up to a 9". I know at least lead_foot uses this combination of an 8" with the 255 tire and uses this for autox with great results. After my stock GSD's run out I will definitely be going with 17x8" lightweight wheels and 255/45/17 tires. The less unsprung weight and wider contact patch should give noticable benefits.

04' G35S 6MT Ivory Pearl, Willow, Premium
Z-Tube / NFC Y-Pipe / Custom Mid-Pipe / 350 EVO Rear Sway/ '03 350Z Shocks and Springs

 

225/55/17 has a slightly taller sidewall, and is fine. The1.6% error in the speedo translates to travelling 61mph when the speedo is indicating 60mph. It also translates to the odometer indicating 1.6% less miles than is actually driven (a plus IMO).


<font color=red>chinee</font color=red>
03.5 G35s

 

So Besides Looking Stupid Everything Should Be Fine?