Tyre Sizes For My New Lexus Alloys

Apologies for the long thread

Ive been using http://www.miata.net/garage/tirecalc.html to calculate which tyres sizes would be best for my new Lexus alloys.

Looking at previous threads regarding tyres for these alloys the following sizes have been quoted as the best ones -:

Front - 245/40/18

Rear - 275/35/18

The thing is my '93 J-Spec would have had 16" alloys when it was new and according to the sticker on my drivers door the stock sizes were -:

Front - 225/50/16

Rear - 245/50/16

I was suprised the front and rear were the same tyre wall profile as i think stock 17" were different by 5mm.

So using the tyre calculator with the stock 16" sizes it says i should use -:

Front - 225/40/18

Rear - 275/35/18

So the rears match with what others say are correct so thats good however the fronts are nothing like, in fact 20mm different.

So should i stick with what the calculator says to keep the speedometer reading as acurate as possible or go with what others have said are the correct sizes. According to the calculator the 245 width tyres would overstate the speedometer by 2.1mph.

Help!!

Personally, I'd say balls to any speedo error, as they're inacurate anyway.

Stick with the sizes recommended by Toyota for those rims.

Originally posted by Matt Harwood

Personally, I'd say balls to any speedo error, as they're inacurate anyway.

 

Stick with the sizes recommended by Toyota for those rims.

Cheers Matt, wise words mate, I guess the expected speedo error isnt all that much anyway.

Ive got my Snooper S6-Neo to tell me my real speed and i know when im going fast

Regards

Chris

Because all Supe's are rear wheel drive and your speedo reading is directly proportional to how quickly your rear wheels turn.

So if you keep the same tyre diameter as the originals on the back then your speedo will be accurate.

You could put front tyres on of any size at all and it wouldn't make any difference to your speedo.

I've got 255/35/18 all round- just a nice size

I would agree with Matt, balls to the speedo reading.

As long as you don't go for a tyre size which is too exteme and they fit you'll be okay.

Looks are more important than the speedo

Originally posted by ChrisR

Front - 225/50/16

Rear - 245/50/16

 

I was suprised the front and rear were the same tyre wall profile as i think stock 17" were different by 5mm.

The middle number of a tyre's size is the Aspect Ratio, it's a percentage of the tyre's width. A much wider tyre on the rear means a lower aspect ratio is needed to keep the sidewall height the same (or as near as poss)

Originally posted by Jake

5mm? You mean 5%.

The middle number of a tyre's size is the Aspect Ratio, it's a percentage of the tyre's width. A much wider tyre on the rear means a lower aspect ratio is needed to keep the sidewall height the same (or as near as poss)

The standard sizes as on the uk 17" wheels are, 235/45 17 and the rears are 255/40 17.

I assume the new tyre sizes will probably increase the rolling circumference of the wheels and therefore your speedo will most likely become more accurate.

Hope this helps!!!!!!!!