Hi guys I have a 23 plate Tsi vrs after changing the current 19 inch alloys for anything more forgiving for commuting on.. What can I go for which is a straight swap for thicker tyres 

The below 7Jx17 ET46 alloy rim normally uses a 205/55R17 tyre size on the Octavia MK4, but as it is a 7J rim width 225/50R17 could be used. This is a non-standard tyre size on the Octavia MK4.

 

7Jx17 ET46 5/112 57.1 alloy rim (from Octavia MK4)

https://eshop.skoda-auto.cz/cs_CZ/alu-kolo-slagard-17-octavia-iv/p/5E3071497D+FL8

 

The below 7Jx17 ET45 alloy rims are normally used with 215/55R17 tyres on the Karoq. However, they could be used with 225/50R17 tyres on the Octavia MK4. It's a non-standard tyre and rim specification on the Octavia MK4. It's almost the same specification as the above 7Jx17 ET46 alloy rim, except that the offset is ET45. Using ET45 instead of ET46 moves the centre of the tyre 1mm further out in the wheelarch, so the front and rear track increases by 2mm. This is a very small difference which is unlikely to be noticed.

 

7Jx17 ET45 5/112 57.1 alloy rim (from Karoq)

https://eshop.skoda-auto.cz/cs_CZ/alu-kolo-ratikon-17-karoq/p/57A071497C+8Z8

 

7Jx17 ET45 5/112 57.1 alloy rim (from Karoq)

https://eshop.skoda-auto.cz/cs_CZ/alu-kolo-ratikon-17-karoq/p/57A071497D+FL8

 

The 225/50R17 would give much better ride comfort compared to 225/40R19 and protect the alloy rim much better from potholes and kerbs. The massive improvement in protection from kerbing damage is shown in the chart below, ie. the sidewalls on the 225/50R17 fitted to a 7J rim width bulge out each side by more than three times more compared to the 225/40R19 fitted to a 7.5J rim width. The rim protection provided by sidewalls that bulge out each side by about 5mm is very poor. The rim protection provided by sidewalls that bulge out each side by about 15mm is very good. It is a night and day difference in the amount of rim protection from kerbing damage. You only get this kind of rim protection from kerbing damage when you use 50 aspect ratio or higher tyres. 40 and 45 aspect ratio tyres just don't offer much protection from kerbing damage.

 

Tyre sidewalls bulge out from the alloy rim by about this much each side

225/40R19 fitted to 7.5J rim 4.75mm

225/50R17 fitted to 7J rim 15.6mm

 

As you can see in the chart below, 225/50R17 has a 0.9% smaller outside diameter compared to 225/40R19. Less than 1.5% difference is generally considered insignificant.

 

Outside diameter of tyres

225/40R19 662.6mm

225/50R17 656.8mm (0.9% smaller outside diameter compared to 225/40R19)

 

As you can see in the ETRTO chart below, 225/50R17 can be fitted to a 7J rim. In fact, Skoda fitted 225/50R17 to a 7J rim width on both the Yeti and the Octavia MK3 Scout 4x4.

 

ETRTO approved rim widths for passenger car tyres
225/50R17 6.0-7.0-8.0

 

As you can see in the two charts below, the 225/50R17 tyre size has a much higher load carrying capacity compared to the 225/40R19 tyre size. This means that lower tyre pressures can be used with the 225/50R17 tyre size compared to the 225/40R19 tyre size.

 

Standard Load index

225/40R19 89 (580kg)

225/50R17 94 (670kg) 15.5% higher standard load index compared to 225/40R19

 

eXtra Load index

225/40R19 93 (650kg)

225/50R17 98 (750kg) 15.4% higher eXtra Load index compared to 225/40R19

 

Another advantage of the 225/50R17 tyre size compared to the 225/40R19 tyre size is cost. It's a much cheaper tyre size.

 

Edited 10 September, 20241 yr by Carlston