Hello I'm new to this forum and no longer much of DIY mechanic.

Would somebody kindly advise if I can change my existing 205/40/ R17 tyres to 205/45s or even 205/50s without messing up the ABS and speedo readings.

Thanks for your attention

Regards

Peter

Welcome to the forum.

Provided you do not mix tyre sizes, ABS won't be affected - but a change in tyre rolling circumference will affect the speedometer reading to some extent - check a tyre site like 'Will they fit' and enter old and new tyre data.

Manufacturers are usually mandated to set speedo to read high - so up to a 5% tyre circumference increase might actually make the speed reading more accurate.

Edited 3 hours ago3 hr by Warrior193
correction

If you want more sidewall height, changing to smaller diameter rims such as 14" or 15" would be a better choice than oversize 17" such as 205/45R17.

14" rims clear the 256x22mm front brake discs, whereas 15" rims clear the 288x25mm front brake discs.

288x25mm front brake discs are the biggest fitted to the Fabia MK2 as standard, so 15" rims can be fitted to all models...but for 14" rims you need to make sure that the front brake discs aren't bigger than 256x22mm, otherwise the 14" rims won't clear the front brake calipers.

You might find that the Fabia MK2 has the 288x25mm front brake discs only with engines that have at least 105HP, but check the car's build codes to be sure in case there are exceptions.

Outside diameter of tyre

185/65R14 596.1mm (non-standard tyre size on Fabia MK2, but fitted to some Roomsters)

195/55R15 595.5mm

205/45R16 590.9mm

205/40R17 595.8mm

Edited 3 hours ago3 hr by Carlston

I use https://tiresize.com/comparison/

if you go for 205/45 at 60mph its actually 62mph and 205/50 its actually 64mph according to their site. As previously said as long as all tyres are the same size ABS etc wont be affected. Had 225/40/18 on a people carrier but the weight rating was too low so went for 225/45/18 and didnt really notice. On it the larger size just cleared the bottom of front strut. Make sure you have enough room.

Alasdair

Edited 2 hours ago2 hr by Alasdair1

If you're going away from OEM sizes you probably need to clear it with your insurers.