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The M35 Tyre Dilemma.


Paramour
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Hello Stagosauruses,

Time is upon me to replace my tyres on my M35 AXIS. . not an overly difficult process I would assume except it has 225/45/18 Tyres on it. I found out they are far from common as they are one of the skinniest 18" tyre. Also the camber of the rear has worn the insides of the rear tyres terribly.

Been told the best option is to get one of the most common performance (Holden/Ford) tyre being the 235/40/18 as it has a very similar "Rolling Diameter", yes the tyres are easy to get and somewhat cheaper. Me doing the usual due diligence checked the tyre card on the door (Post compliance one) and it suggested:

235/50/R18

7 1/2 JJ 18

Load Index - 97

Speed Cat "H" or 210k/h

So my questions for my learned friends are:

1. Can/should I use the suggested 235/40/18

2. Can you change the camber on the rear, I am thinking NO

3. The 235/50/18 appears to be going too high a profile for my liking. . .

4. Any other suggestions would be most welcome

Jules

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I found this just then. . .Assuming current tyre is correct

Stock Tire - 225/45R18 >Search Tires

Section Width: 8.85 in 225 mm

Rim Diameter: 18 in 457.2 mm

Rim Width Range: 7 - 8.5 in

Overall Diameter: 25.97 in 659.63 mm

Sidewall Height: 3.98 in 101.09 mm

Radius: 12.98 in 329.69 mm

Circumference: 81.58 in 2072.1 mm

Revs per Mile: 800.9

Proposed Tire - 235/40R18 >Search Tires

Section Width: 9.25 in 235 mm

Rim Diameter: 18 in 457.2 mm

Rim Width Range: 8 - 9.5 in

Overall Diameter: 25.40 in 645.16 mm

Sidewall Height: 3.70 in 93.98 mm

Radius: 12.70 in 322.58 mm

Circumference: 79.79 in 2026.6 mm

Revs per Mile: 818.8

Says speedo will be 2.234% fast

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Ok I may of sorted it out but only if I know what was normal for the car...how do I find out what was meant to be on the car. . . .

Someone please tell me how I can find out what it was meant to be....please... :)

Base Tyre V's Proposed tyre, with Speedo at 100k/h

235/50/18 V's 235/40/18 = 107k/h 7.2% too fast 6.79% difference

235/50/18 V's 225/45/18 = 104k/h 4.9% fast, 4.7 % difference

225/45/18 V's 235/40/18 = 102k/h, 2.2% fast

225/45/18 V's 235/50/18 = 95.3k/h, 4.7% too slow

The web I got the calculator from was

http://www.1010tires.com/TireSizeCalculato...t&reset=yes

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Can't offer advice, but a warning.

My car has a +9% speedo error and it is really irritating.

Sit on the indicated speed and you are blocking traffic, and to do the rough calculation in your head and drive at a higher indicated speed means that you are constantly thinking about "how fast am I really going".

It's a trivial thing, but if you see a cop and the speedo says 120, you can't help but react.

Looking forward to getting new tyres in due course and will reap the benefits of your research.

m

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235/50/18 sounds quite large.

I don't have an Axis but the stockies on the RS are 225/45/17 and my Nismo's came with 235/40/18's.

I would assume that the Nismo rims would be roughly the same as Axis stock 18's, with both being 8" wide.

The calculator says that my speedo should be reading 1.4% slow, but I have found that if I sit on the speed limit, I am holding everyone up.

As an aside, steer clear of Nankan and Kenda tyres.

I currently have Kenda's and although they are A M A Z I N G in the wet, when the temp reaches 35 degrees, they become very soft and squishy (not fun).

I would be looking at 235/45/18 or 235/40/18.

The 40's will have a harder ride though.

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235/50/18 sounds quite large.

I don't have an Axis but the stockies on the RS are 225/45/17 and my Nismo's came with 235/40/18's.

I would assume that the Nismo rims would be roughly the same as Axis stock 18's, with both being 8" wide.

The calculator says that my speedo should be reading 1.4% slow, but I have found that if I sit on the speed limit, I am holding everyone up.

As an aside, steer clear of Nankan and Kenda tyres.

I currently have Kenda's and although they are A M A Z I N G in the wet, when the temp reaches 35 degrees, they become very soft and squishy (not fun).

I would be looking at 235/45/18 or 235/40/18.

The 40's will have a harder ride though.

Hello,

Thanks guys....sorted out stock size on the AXIS it is 225/45/18, the 235/50/18 is the recommended size for ARX's.

So now that I know correct size it appears that the following are the best option in order of least diameter difference in from stock

1. 245/40/18 - 1%

2. 235/45/18 - 1.3%

3. 235/40/18 - 2.2%

4. 245/45/18 - 2.6%

Now lets see if I can get some nice 245/40/18 's . . .Happy that all sizes come in under the recommended 3% variance

Jules

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get a wheel alignment too. that wear on the inner tread is from bad toe adjustment not from camber wear.

i also had problems getting tyres for the ARX rims to be a similar size to the RS/RX rims. so im down 5% in size because i went for a readily available 235x45x18 because of cost

maybe factor that in to your purchase. sometimes rare sizes are prohibitively expensive

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Jules, join SAU-NSW and you can get access to cheap Federal 595-SS's. I've got them on my C34 and my confidence in the car has grown immensely!

There's a link to the forms in my signature. The cost of signing up to the club makes up for the discount you should receive for the tyres if you choose to go with the Federals.

Oh, and I went from 225/50R16s to 245/40R18s and now my speedo is almost dead accurate according to two different GPS units I've tested it against.

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Jules, join SAU-NSW and you can get access to cheap Federal 595-SS's. I've got them on my C34 and my confidence in the car has grown immensely!

There's a link to the forms in my signature. The cost of signing up to the club makes up for the discount you should receive for the tyres if you choose to go with the Federals.

Oh, and I went from 225/50R16s to 245/40R18s and now my speedo is almost dead accurate according to two different GPS units I've tested it against.

Cool will look at Federals...

Yeah my speedo is currently 5-8 k's slow by GPS. . so the new tyres wont be too bad then if they are a bit faster. . .

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