Tires: Tires, Changing from 215s to 225s on same rims, michelin pilot xgt h4, dunlop sp sport

Question
Barry,  How can I determine if changing from 215's to 225's will physically fit the G35 car?  My issues is wet grip not hydroplaning.  Many thanks, Brian-------------------------
Followup To
Question -
Sir, I have a 2004 infiniti G35 sedan with Goodyear RSA 215/55VR17 tires.  They need replacement at 31,000 miles.  They have performed poorly in wet weather.  I live in Chattanooga which gets 52" rain per year.  Problem is what to replace them with.  Infiniti says keep the RSA's.  I prefer better tires.  Can I safely upgrade size to 225's on the same rims?  Many more choices in that size.  Any particular tire you would recommend - I have read that Bridgestone RE950's, Michelin Pilot XGT H4's and Dunlop SP Sport A2's all perform better in the wet.  I am a marketing guy lost in the weeds.  Many thanks for your advice.  Brian King  706-260-2614
Answer -
Brain,

Wet traction's a problem?  There are 2 kinds of wet traction.  Hydroplaning (a problem at freeway speeds) and wet grip (slow speeds)  

And there are different fixes for these problems.

Hydroplaning should be addressed by skid depth (meaning new tires are better than worn tires), inflation pressure (more is better), and the width (less is better).  So if hydroplaning is the problem, you're going the wrong direction in tire size.

However, if the wet grip is the problem, then high inflation pressure helps, as does a change in rubber compound.  Typically original equipment tires are compounded with rolling resistance in mind and one of the areas that gets sacrificed is wet grip.  (Wear is the other area).

So simply changing to a non-OE tires should help.  But you will lose some fuel economy in doing so.

BTW, the reason they recommended the RSA's is that they can't get themselves in legal trouble if they recommend what's already there.  

As far as recommendations?  Since I work for a major manufacturer you would not be able to tell if I was promoting my company's products or not, so I don't do that.

Try looking at Tire Rack, but better yet, ask around about what works in your area.  Wet grip is highly dependent on the road surface and different rubber compounds will react to the road surface differently and there will be some reversals.

Hope this helps.  

Answer
Brian,

I checked to see if the rim was wide enough, and it is.

However, I don't have a nice chart that shows me the size of the fenderwell of your vehicle (or anyone else's vehicle), so I can only take an educated guess.  Since there is usually some accommodation made for chains (at least for the smaller cable type "chains"), then 10 mm shouldn't be a problem.  But this is something you may need to look at yourself.  Just remember the worst case is fully turned / fully compressed.

Hope this helps.