19" alloys tyre size

J

joeac

Member
Hi I'm looking to get some csl reps from cm wheels in 19" my z4 is a 3.0 non m so I've found the correct wheels for it but I'm not sure what tyre sizes to get as I don't want the Speedo to read differently to what it currently reads on 17" wheels. Can anyone confirm what tyres will ensure the Speedo is correct?
 
http://ejelta.com/tiresize/index.html?ws18=1&ws17=1&tiresize=225/45-17&maxdelta=2&minwidth=&maxwidth=&minratio=&maxratio=&minwheel=&maxwheel=

Put your current tyre size in the box at the top of the page an then use the chart below
 
markplant said:
http://ejelta.com/tiresize/index.html?ws18=1&ws17=1&tiresize=225/45-17&maxdelta=2&minwidth=&maxwidth=&minratio=&maxratio=&minwheel=&maxwheel=

Put your current tyre size in the box at the top of the page an then use the chart below
Click to expand...

Thanks for this, very useful link:)
 
Russ59 said:
I'm running 235/35/19 and 265/30/19
Click to expand...

Thanks Russ this appears to be the standard CSL tyre size for the oem alloys, can you confirm if your speedo is accurate with these tyres?
 
joeac said:
Russ59 said:
I'm running 235/35/19 and 265/30/19
Click to expand...

Thanks Russ this appears to be the standard CSL tyre size for the oem alloys, can you confirm if your speedo is accurate with these tyres?
Click to expand...

This is the difference with my 19's

Front
Speedo reading Actual speed
20 mph (32.19 km/h) 20.4 mph (32.84 km/h)
25 mph (40.23 km/h) 25.5 mph (41.05 km/h)
30 mph (48.28 km/h) 30.61 mph (49.25 km/h)
35 mph (56.33 km/h) 35.71 mph (57.46 km/h)
40 mph (64.37 km/h) 40.81 mph (65.67 km/h)
45 mph (72.42 km/h) 45.91 mph (73.88 km/h)
50 mph (80.47 km/h) 51.01 mph (82.09 km/h)
55 mph (88.51 km/h) 56.11 mph (90.3 km/h)
60 mph (96.56 km/h) 61.21 mph (98.51 km/h)
65 mph (104.61 km/h) 66.31 mph (106.72 km/h)

Rear

Speedo Reading Actual Speed
20 mph (32.19 km/h) 20.23 mph (32.56 km/h)
25 mph (40.23 km/h) 25.29 mph (40.7 km/h)
30 mph (48.28 km/h) 30.35 mph (48.84 km/h)
35 mph (56.33 km/h) 35.4 mph (56.98 km/h)
40 mph (64.37 km/h) 40.46 mph (65.11 km/h)
45 mph (72.42 km/h) 45.52 mph (73.25 km/h)
50 mph (80.47 km/h) 50.58 mph (81.39 km/h)
55 mph (88.51 km/h) 55.63 mph (89.53 km/h)
60 mph (96.56 km/h) 60.69 mph (97.67 km/h)
65 mph (104.61 km/h) 65.75 mph (105.81 km/h)
 
To keep your rolling radius as close to oem as possible and therefore have minimal speedometer inaccuracy you need to run 225/35/19s front and 265/30/19s rear. :)
 
Thanks for the replies guys, I'm currently in two minds to go for the 18" or 19" CSL reps from cmwheels. It appears the 18's are more popular amoungst forum members ! There are two types of 18s on cm wheels and not sure which to go for.
 
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