205/55R16 to 225/50R16

[be989]

Hi guys, didn't want to hijack the tyre size thread so I created a new one for my specific question.

The stock tyres on my Mk2 Focus is 205/55R16 running on 16x7 stock wheels. Will I run to any rubbing problems with a 225/50R16 tyres? Both tyres have the same outer diameter, it's the width I'm worried about.

 

[HDi fun]

The 225 will have a larger outer diameter than a 205. The sidewall height is 55% of the width.

 

[obi_waynne]

I wouldn't chance it, the new tyres are quite a bit wider and on a narrow rim it doesn't work that well usually the handling gets a bit flappy if you know what I mean.

You're best bet if you want wider tyres is to get a set of wheels from an ST or similar at a breakers yard. The diesel ride height is higher so you won't have any issues with rubbing.

 

[HDi fun]

Sorry chaps - I'll correct my post. I didn't spot that the 225 was a 50 profile not a 55 so therefore the overall diameter will be pretty much indentical to the 205/55.

I suspect they probably will fit quite happily. Go and have a look around and see what else is fitted to MkII Focus models.

 

[obi_waynne]

I should also qualify my post. If you have 7inch rims you should be fine, if they are 6 inches then I would stick with 205's or run on some 7 inch rims.

I know a few have got away with the 225's on 6 inch rims but if I were your tyre fitter I'd caution against it.

 

[HDi fun]

I should also qualify my post. If you have 7inch rims you should be fine, if they are 6 inches then I would stick with 205's or run on some 7 inch rims.

I know a few have got away with the 225's on 6 inch rims but if I were your tyre fitter I'd caution against it.

Extremely good point. This can cause sidewall flex and heating problems.

 

[be989]

Yup, here's a link to the wheel-tire size comparer:

http://www.rimsntires.com/specs.jsp...t2=50&text1=Stock 2010 Ford Focus TDCI&text2=

And these are the wheels that came with my Focus:

http://www.accessoryplus.co.uk/product/Ford_16"_5_Spoke_Y_Design_Alloy_Wheels_FO1483642

pretty much the 16" version of the ST wheels. It's 16x7 et50. I've checked around and found out that the "measured rim width" for a 225/50R16 tyre is 7" while for a 205/55R16 is 6.5" so the 225's would fit perfectly on the 16x7 wheels.

Question is if it'll rub on full steering lock on the Focus.

Reason for going to wider tyres is more for aesthetics though the increase in lateral grip would be most welcomed. But if it's just going to rub on full steering lock then I would just stick to the 205's.

Anyone?

 

[obi_waynne]

Have you lowered the car? If not you should be fine IMO. Diesels are pretty high up and there is lots of space inside the wheel arch. You always have the option of spacers if there was a problem though.

 

[be989]

Nope, haven't lowered it yet. I'll keep you guys updated when I make the switch.

Thanks guys.

 

[Prince]

I would roll the arches just as a precaution. Surely fitting much wider tyres will cause tramlining though.

 

[HDi fun]

20mm isn't likely to upset it much. Plenty of Focus size cars are on 225s now

 

[jarrus]

Personally I would go for a wider rim as well, using a wider tyre on a narrow rim tends to make the side wall a little softer and therefore could accentuate roll in the corners.

Also if going lower go for shocks as well as springs as lower spring on there own is a bit of a half arse job really...

 

[ninjasta]

225 width tyres will can be fitted onto rims between 6 and 7.5 inches the ideal is
(225*.7)/25.4 = 6.2 inchs or 6 or 6.5 inch rims.
The edge of the new tyre will be 10mm closer to the inside of the wheel well and suspension components, and 10mm further out from the edge of the bodywork if keep the std offset.

 

[Prince]

225 width tyres will can be fitted onto rims between 6 and 7.5 inches the ideal is
(225*.7)/25.4 = 6.2 inchs or 6 or 6.5 inch rims.
The edge of the new tyre will be 10mm closer to the inside of the wheel well and suspension components, and 10mm further out from the edge of the bodywork if keep the std offset.

Why is it times by 0.7 and divided by 25.4?

 

[ninjasta]

Why is it times by 0.7 and divided by 25.4?

There are 25.4 mm to an inch so to convert a tyre width in mm to inches
divide by 25.4.

.7 or 70% is a factor to account for the laterally loaded (sideways squish) that keeps the radial's contact patch flat relative to the road. It relative to the sidewall stiffness.
Car Bibles has a tyre page that explains this a little. You need a weight transfer sheet and lateral G-meter to observe the effect which it isn't linear.

 

[Prince]

Thanks for that mate. Interesting stuff.