RX450H 20 inch upsized tyres?

YvesD · 2024-09-25T20:48:47Z

Hi, apologies in advance, I saw a post from someone a good while back about fitting wider tyres on the RX but try as i might, cant find it again.

I would like to fit either 255/50/20 or 255/55/20 to my car to improve the overall grip on the tarmac and also to improve the aesthetics. For the size and weight of this car it

always seems a bit 'under tyred' to me. Adequate, but could be better.

Anyone with experience of doing this on the RX please?

Thanks

Bob450 · 2024-09-26T07:15:12Z

Hi, I have a NX450h+ with 20" wheels and I spent a lot of time researching tyres because of persistent noise problems. The two tyre sizes you mention are different diameters/circumferences and (since one of them is the original diameter) there is more than a 3% difference. This meant that the speedo reading netween the two will be different, with the possibility of speeding charges for the bigger tyre. Edit https://tire-calc.com/comparison/255-50-r20-and-255-55-r20/

As you mention, these are "wider" tyres. What size is the wheel? I would imagine that the RX450 would have as original 235/55 R20 on 7-1/2" J rims or just possibly 8" J. The wider tyres might possibly not make a proper seal on the 7-1/2" rim. I don't know if this is correct in your case, but there is a lot of information on the net regarding tyre size calculations which might be helpful. Good luck with your search!

Edited 14 hours ago by Bob450
Added tyre size calculator address

YvesD · 2024-09-26T15:10:25Z

Thanks for your thoughts Bob, appreciated.

I did check the speedo error calc with an online tool and in my case it would pretty much erase the +3mph over my speedo reads compared to road side monitoring signs and independent GPS readout.

The OEM rims are 20 inch 8J.

I've actually bought an old RX wheel and a used 255/50/20 off eBay and had them mounted. No fitting issues and the extra width looks right and affords extra rim protection.

For reference, the 255/50 tyre is very close to the original 235/55 in overall size, near as makes no difference.

Not got round to mounting the wheel on the car on each corner to check for clearance but not expecting any problems.

Cheers