Tyre sizes? Advice needed please.

[Gavstar]

I appreciate this topic has been done to death, but I think my situation is slightly different. My 400 (with PAS) has wider tyres all round than the handbook suggests, as I have always replaced like for like. Now that it has been highlighted to me, I am wondering if I should change.

I have:
Front - 225/50/ZR15 (Dunlop Sp9000)
Rear - 245/45/ZR16 (Bridgestone SO2)

The handbook says for a 4L:
Front - 205/60/ZR15
Rear- 225/50/ZR16

The handbook says for a 5L:
Front - 205/55/ZR15 or 215/50/ZR15 for PAS
Rear - 235/50/ZR16

I need new rears, so should I match what I already have on the rear, or go with what the book says, which means the fronts are going to be as wide as the rear? Will this affect handling? Would it be more sensible to stick to the current size rears, then change the fronts to narrower when they are due (not for a while as were new a few thousand miles ago).

[Gavstar]

Have just looked up in the Bible and it seems that my fronts are exactly right for the year, and it's my rears that are wider than recommended. So looks like I'll be fine with 225/50/ZR16 on the rear. Easy! (Also, it seems nigh on impossible to get 245s to fit the rear anyway).

[V8 Devil]

I run 205 50 15 and 245 45 16. I have run 205 55 15 and 225 50 16 but like the extra width on the rear.
I did have some 225 50 15 fronts with the 245 45 16's and liked the way they felt, although they rubbed on the battery box. I therefore went down to 205 50 15 as I wanted to keep a low profile tyre to match the rears. At the moment the front feels a little light compared to the 225 50 15's but could be the new dampers and increased tyre pressures.
If you're happy with the sizes you have i'd stick with them. Toyo do the 245 45 16, £82.50 from camskill.

Edited by V8 Devil on Monday 29th October 17:04

[Gavstar]

Cheers V8 Devil. Those Toyos are W rated though aren't they. The Bible insists on nothing less than Z - not just for max speed but also acceleration....I know it's a topic that's been discussed loads on here too, but my gut feeling would be to follow the advice of the author....

[daz the plumber]

front 205/55/15 rear 225/50/16

[Sound Chaser]

Gavstar said:

Cheers V8 Devil. Those Toyos are W rated though aren't they. The Bible insists on nothing less than Z - not just for max speed but also acceleration....I know it's a topic that's been discussed loads on here too, but my gut feeling would be to follow the advice of the author....

W rating is up to 168mph. Shouldn't be a problem then.

[GreenV8S]

The tread width should be similar to the rim width. What makes it slightly tricky is that the nominal tyre width quoted for road tyres isn't the tread width it's usually the width at the sidewall. There is some variation between brands, but as a rough guide the tread width will probably be roughly an inch less than the nominal width. Hence the ideal width for the 7 1/2" rear rims is going to be around 215 -225 and the ideal width for the 7" fronts is around 205. You can go plus or minus half an inch without any trouble, but 245 is really a bit too wide for the standard rear rims and 225 is similarly a bit too wide at the front.