Weird tyre sizes

[aaron_2000]

Found a set of BBS split reps to do a refurb on for my mates old Ford which will be coming out of hibernation in spring. They're 16x8.0 and 16x9.0 but have found it impossible to find tyres as tyre calculators show only 255/30/35/40 will fit the 16x9.0. The 16x8.0 shows as having a much bigger range from 225-275 and 30-70, can someone who knows far more about calculating tyre size from the rim size please help me out.

[Scrump]

What overall diameter does the car need/ what are the standard tyre sizes?

[stevieturbo]

aaron_2000 said:

Found a set of BBS split reps to do a refurb on for my mates old Ford which will be coming out of hibernation in spring. They're 16x8.0 and 16x9.0 but have found it impossible to find tyres as tyre calculators show only 255/30/35/40 will fit the 16x9.0. The 16x8.0 shows as having a much bigger range from 225-275 and 30-70, can someone who knows far more about calculating tyre size from the rim size please help me out.

Just because a tyre will fit a rim...and rims can carry a wide range of sizes..does not mean it is the ideal size for that rim, nor indeed whether it will fit whatever car you do not say it is for.

and what tyres were already on them ?

[aaron_2000]

It's a MK5 Cortina, original wheels were 155/80 R13. Seen plenty on 16" BBS splits but can't seem to find the specific tyre sizes for 16x8.0 and 16x9.0

[Scrump]

215/40 and 245/35 are almost identical diameter to the orginal tyres and will fit the rims.
Not sure if those tyre sizes are actually available though!

[aaron_2000]

Scrump said:

Something like 205/40 and 235/35 would fit the rims and give similar diameter (both those are slightly smaller diameter than the original tyres but only by a few %.

205/40 on the 8.0's and 235/35 on the 9.0's you think would do? Smaller diameter isn't really an issue as it's lowered anyway. Current wheels are 195/50 R15 and 195/55 R15

[Scrump]

Use an app such as ‘tire calculator’. You can put in your current tyres sizes and compare to other sizes.

Look here : https://www.tyres-pneus-online.co.uk/tyre-equivale...
for a guide to what tyre widths will fit the 8 and the 9 inch rims.
(8 inch rim is 225 or 235 but could be 215 and 245; 9 inch rim is 245 or 255 but could be 235 or 265)
Then use the tire calculator app to see what profile would match the diameter you want.

[Scrump]

aaron_2000 said:

205/40 on the 8.0's and 235/35 on the 9.0's you think would do? Smaller diameter isn't really an issue as it's lowered anyway. Current wheels are 195/50 R15 and 195/55 R15

The 195/50 r15 tyres give almost identical diameter to the original 13 inch tyres. The 195/55 tyres have a larger diameter.

[aaron_2000]

Appreciate all the help. Gonna go pick the wheels up tomorrow then take them to the tyre shop see if they have anything that fits without massively changing the diameter. Will update the thread tomorrow, cheers all

[DavidY]

Just a small word of warning, these 'new' wheels and tyres have the potential to generate a lot of grip, which the original tyres would not have had - its a big upgrade! If it is driven enthusiastically you will put a lot of strain on the suspension components (and driveshafts and UJs/CV joints) - if these have not been 'upgraded' to suit then you will start breaking things, and potentially cracking suspension arms etc - please check them regularly.

[RobXjcoupe]

235 on a 9j rim will have a side wall just slightly leaning inwards. A 215 on the 8j will look similar. Offsets are a big factor though, as you get wider the clearance between inner and outer wheel arch is more critical so having a tyre with a slight stretch will aid any close clearance issues