I believe the stock 17" rims are a 7" width. So the question isn't how wide can you go without modifying the fenders, but rather how wide you can go on a 7" wide wheel. 215s are ideal on a 7" width. You can run a 225, but any higher than that and you're going to be fighting for traction. If you want to go wider, you're going to need a wider wheel.

Find many great new & used options and get the best deals for 2013-2018 Ford C-max Compact Spare Tire With Jack Kit at the best online prices at eBay! Free shipping for many products!

When it’s time to shop 2014 Ford C-Max tires, we’d suggest premium all-season tires like the Dunlop SP Sport 5000 DSST, Goodyear Eagle LS-2 ROF, Michelin Primacy 4 or Continental ProContact RX - SSR. These are all tires that will deliver the performance and value you need for your 2014 Ford C-Max! Need MPG information on the 2013 Ford C-Max Hybrid? Visit Cars.com and get the latest information, as well as detailed specs and features. Rear Tire Size: P225/50R17: Front Tire Size: P225 I would speak with Ford to see how they handle that discrepancy. If they allow you to use chains then you could use either # PW1034, and rubber adjuster # PW99, that you have referenced if the tire size is 225|50-17. If you have a different tire size, let me know and I can make other recommendations.
List to date: Stock size: 235/65/16, no modifications needed, fits in spare tire mount. 245/75r16, no modifications needed, no info on spare tire mount. 255/70R16, no modifications needed, does not fit spare tire mount. 245/70R17, modifications needed, using 2.5" lift, fits in spare tire mount.
. 33 168 246 79 7 312 109 186 329

ford c max tire size 2013