Questioning the Recommended Tyre Widths based on Offset

[Energiser]

I've been researching for a new set of wheels, currently looking at Enkei SC24s, and have been heavily referencing the Official Wheel and Tyre Guide (http://www.yarisworld.com/forums/showthread.php?t=5021).

My current wheels/tyres are 205/50/16 on 16x7 +42. According to the guide, +42 is the lowest offset for which 205mm wide tyres are recommended. When I lowered my car on TRD springs, a tiny amount of rubbing developed on the front inside edge of the tyre, but only when the wheel is turned in at full lock. When the wheels are pointed straight ahead, the tyres are almost perfectly in-line with the outside edge of the fenders.

The Enkei's only come in +40 offset (-2 relative to my old wheels), otherwise I intend to keep everything identical. According to the guide I should reduce the tyre width to 195 for this offset, but I'm struggling to understand why. If anything, this reduction in offset should reduce rubbing on the inside edge... the only downside I can see is that the tyre would stick slightly outside the fenders.

Does anyone know why the guide recommends the lower widths at these offsets? My best guess is that it's based on when the tyre will protrude from the fenders, rather than rubbing.

[grelise]

I replied to your PM.

I have 205 on mine on +40, at full lock I hear no rubbing on the insde splash guard and nothing straight on.

[Energiser]

Thanks Grelise, that makes me more comfortable about my planned setup.

The question still stands though: If I'm rubbing on the inside edge at 205 on +42, wouldn't 205 on +40 be 2mm better on clearance on the inside edge? Why would the guide say to also reduce the width?

[Viperoni]

If I'm rubbing on the inside edge at 205 on +42, wouldn't 205 on +40 be 2mm better on clearance on the inside edge?

This is true.

[kimona]

Yes, 205's on 16x7, ET42's may rub very slightly inside edge (depending on the tyre) at full lock... which is an extremely rare maneuver only used at very low speeds. It is not a concern with this fitment.

205's on 16x7, ET40 probably won't rub full lock (depending on the tyre), but may poke a tad up front (which doesn't bother some folks), and often rubs if you are lowered more than a mild drop.