TYRE QUESTION

[TOV!E]

Hi all, I have 255/35/18s all round and will need to replace very soon. (25,000 miles) i cant find Goodyears in this size but on ebay you can buy 225/40/18s, IS this 5mm going to make a lot of problems. Gordon..........

[Barry Ashcroft]

It's not 5mm

The difference is 35% of 255 compared to 40% of 255 so next to nothing.

I changed my rears from 235/35 to 255/40

Edited by Barry Ashcroft on Friday 24th April 17:58

[Mad Mitch]

Just get someone or yourself with a gps to verify the speed reading as the tyres will be giving a false one. If the speedo reads high its no prob, but if its reading low, and with the increase in zero tolerance with scameras etc you could end up in one heap of trouble. If you google " Miata" it has a tyre comparison prog that allows you to enter the cars "Original tyres". ie factory fit, and then your choice. It gives the speed reading differences.

Steve.

[TOV!E]

Mad Mitch said:

Just get someone or yourself with a gps to verify the speed reading as the tyres will be giving a false one. If the speedo reads high its no prob, but if its reading low, and with the increase in zero tolerance with scameras etc you could end up in one heap of trouble. If you google " Miata" it has a tyre comparison prog that allows you to enter the cars "Original tyres". ie factory fit, and then your choice. It gives the speed reading differences.

Steve.

Thanks Mitch,did not think off that..........

[Pete500]

255 by 0,35 is 89,25. 225 by 0,40 is 90,00 18" by 25,4 is 457,2. 255 diameter is 89,25+89,25+457,2 = 635,7mm. 225 diameter is 90+90+457,2 = 637,2mm. 637,2 divided by 635,7 is 1,002. This 0,2% increase in diameter is no problem. But rim width might be a problem for that narrow tire.

[NCE 61]

225/40/18 would be OK for the front, but a bit narrow for for the rear.

Tyre size calculator.

http://www.miata.net/garage/tirecalc.html

[glow worm]

A Mk2 Tuscan was designed for 225/40's on the front. I guess it's your rears that need replacing...So swap your fronts to the rears and put the 225s on the front and you'll get far less tramlining.