Tyre and wheel advice

PG68 · Dec 29, 2016

Please be gentle with me, silly question to some.

The standard car comes with 9.0 front and 9.5 rear 255 & 275 - 40's

What is the popular 20" upgrade size front and rear for staggered wheels. And what tyre size there after. I like the Michelin PSS which come in 35 aspect.

What do have fitted on your car?

Or can you point me in the right direction so I can find out more information / thanks in advance.

Unkle Ed · Dec 29, 2016

I ended up with 20x9.5 +25 Front and 20x10.5 +45 Rear

20x10 +30 Front, 20x11 +50 and 20x10 +40 Rear are also other common fitments. It will all depend on which wheel you decide to go with and what sizes they provide.

295/35 20 Rear and 275/35 20 Front seems to be a popular combination that is easy to find and 305/30 20 rear works aswell but harder to find.

I ended up running Pirelli Pzero in 295/30 20 Rear and 265/35 20 Front on my tyre shops recommendation and also what he could get on short notice before christmas. He was very hung up on keeping things as close to standard as possible and the actual tyres are only 1-2.5% bigger than the original tyres and the circumferences are near identical to each other with only 4mm difference in diameter.
The 295/30 20 is also supposedly the standard issue on some Porsche's and apparently have a different stickier compound to the standard Pzero.

SteamPlane · Dec 29, 2016

I've found this website quite handy for figuring out what might fit:

http://www.willtheyfit.com/index.php?

Myke · Dec 29, 2016

Unkle Ed said:
I ended up with 20x9.5 +25 Front and 20x10.5 +45 Rear

20x10 +30 Front, 20x11 +50 and 20x10 +40 Rear are also other common fitments. It will all depend on which wheel you decide to go with and what sizes they provide.

295/35 20 Rear and 275/35 20 Front seems to be a popular combination that is easy to find and 305/30 20 rear works aswell but harder to find.

I ended up running Pirelli Pzero in 295/30 20 Rear and 265/35 20 Front on my tyre shops recommendation and also what he could get on short notice before christmas. He was very hung up on keeping things as close to standard as possible and the actual tyres are only 1-2.5% bigger than the original tyres and the circumferences are near identical to each other with only 4mm difference in diameter.
The 295/30 20 is also supposedly the standard issue on some Porsche's and apparently have a different stickier compound to the standard Pzero.

Hey Ed, what does the "+xx" you mention refer to?

stasik-a4 · Dec 30, 2016

Myke said:
Hey Ed, what does the "+xx" you mention refer to?

It Means positive 50mm ofset from cetre line :thumbsup:

PG68 · Dec 30, 2016

Thanks guys for the input, thanks Ed for the detailed advice and thanks Ross for web site link.

I googled the standard 19" rims and it tells me that the standard off set is-
Front- 45
Rear- 52.5

Now Ed in your post you mention you run 35 aspect front and 30 rear. This may sound dumb but my question is- The distance between rim and outer rubber, are they the same front and rear?

I thought if you had a 20" rim with 35 aspect front and rear then it would be the same distance between rim and outer rubber diameter regardless of tyre width. But I think it must be a percentage thing compared to tyre width??? Thus your similar outer diameters front and rear. Please correct me if I have no idea.

Is the offset the distance from centre line of the wheel + or - ?
Your rear wheel has a +45 offset compared to the standard wheel at 52.5. So this means your new 10.5" wheel protrudes further towards the outer wheel guard /panel because the distance between standard 52.2 (9.5" wheel) compared to 45 on the new wheel (10.5" wheel) is 7.5 shorter. Taking in account the wider wheel of an extra 25mm (1") width the distance increases by another 20mm (7.5 offset & 1/2 25mm=12.5) totalling all up 27.5mm close to the outer guard and 5mm closer to the inside strut.

Then the next thing to take into account is tyre bulge distance protruding from the wheel

Am I right in my thinking here or totally off the bloody planet??????? :headbonk:

Sorry for the maths lesson, I am just trying to get head around all this

Burkey · Dec 30, 2016

PG68 said:
Thanks guys for the input, thanks Ed for the detailed advice and thanks Ross for web site link.

I googled the standard 19" rims and it tells me that the standard off set is-
Front- 45
Rear- 52.5

Now Ed in your post you mention you run 35 aspect front and 30 rear. This may sound dumb but my question is- The distance between rim and outer rubber, are they the same front and rear?

I thought if you had a 20" rim with 35 aspect front and rear then it would be the same distance between rim and outer rubber diameter regardless of tyre width. But I think it must be a percentage thing compared to tyre width??? Thus your similar outer diameters front and rear. Please correct me if I have no idea.

Is the offset the distance from centre line of the wheel + or - ?
Your rear wheel has a +45 offset compared to the standard wheel at 52.5. So this means your new 10.5" wheel protrudes further towards the outer wheel guard /panel because the distance between standard 52.2 (9.5" wheel) compared to 45 on the new wheel (10.5" wheel) is 7.5 shorter. Taking in account the wider wheel of an extra 25mm (1") width the distance increases by another 20mm (7.5 offset & 1/2 25mm=12.5) totalling all up 27.5mm close to the outer guard and 5mm closer to the inside strut.

Then the next thing to take into account is tyre bulge distance protruding from the wheel

Am I right in my thinking here or totally off the bloody planet??????? :headbonk:

Sorry for the maths lesson, I am just trying to get head around all this

Aspect ratio is exactly that, a ratio. So, as your tyre gets wider, the sidewall gets taller for a given aspect ratio. Eg. Need to reduce aspect ratio as tyre gets wider in order to retain same O.D.

10.5" +45 will sit 7.5mm closer to guard courtesy of offset plus another 12.5mm courtesy of width = 19.5 mm

PG68 · Dec 30, 2016

Burkey said:
Aspect ratio is exactly that, a ratio. So, as your tyre gets wider, the sidewall gets taller for a given aspect ratio. Eg. Need to reduce aspect ratio as tyre gets wider in order to retain same O.D.

10.5" +45 will sit 7.5mm closer to guard courtesy of offset plus another 12.5mm courtesy of width = 19.5 mm

Hey Burkey,
Thanks for the simple explanation, it is starting to sink into this grey matter now.

I was still taking into account the extra 7.5mm due to offset caused by wider wheels, but I don't need to do that.
The aspect ratio now makes sense also.

Thanks mate

GT Nick · Dec 30, 2016

I went with Velgens in 20" . They are made with offsets to suit the Pony and ,fill the wheel arches beautifully! Rear offset is 45, about as concave as you can get!
As per rubber, I went with the Nito invos 275 35 20 fronts and 295 35 20 rears.
Luv the look and performance, especially so with my 35mm lowering springs from Voitgland.
Happy to post a picture if I can figure out how to do it!!,

Cheers

Nick

05STNG · Dec 30, 2016

also check out the Koya thread as it has a lot of info that will assist you

http://www.mustang6g.com/forums/showthread.php?t=55198&highlight=koya&page=13

Unkle Ed · Dec 31, 2016

PG68 said:
Now Ed in your post you mention you run 35 aspect front and 30 rear. This may sound dumb but my question is- The distance between rim and outer rubber, are they the same front and rear?

You're well and truely on the right track with your thinking and Burkey has you sorted.

Doing the 35/30 ratio with the widths I went with gives the tyres an overall diameter that is only 4mm different. The sidewall is only 2mm taller on the back wheels than the front so visually to look at them the profiles look identical.

Also running the sizes I did keeps the overall circumference damn close to the original tyre sizes so the speedo isn't out of whack and staying within legal requirements isn't an issue.

It makes it alot easier to use a tyre calculator when you get to deciding on what tyre size you want to run to compare what the difference will be between stock and modified . I often use this one https://tiresize.com/tyre-size-calculator/

Nong · Dec 31, 2016

I am thinking of doing Project 6GR wheels, 19" by 10" in a square setup. I believe the offset is +35mm. Can anyone see a problem with this.

Burkey · Dec 31, 2016

Nong said:
I am thinking of doing Project 6GR wheels, 19" by 10" in a square setup. I believe the offset is +35mm. Can anyone see a problem with this.

It's a common fitment in the US.
Fronts will sit 10mm closer to the guard via offset, plus another 12.5mm for width, totalling 22.5mm nearer the guard.
Rears get an extra 17.5mm from offset and 6.25mm from width, 23.75mm in total.
The 11" +50 rear wheel sits slightly further inboard (2.5mm) than a 10" +35 square set-up rear.

Nong · Dec 31, 2016

Wow, thanks Burkey, great information. I assume they would fit inside the guard and be legal.

Burkey · Dec 31, 2016

Nong said:
Wow, thanks Burkey, great information. I assume they would fit inside the guard and be legal.

Just about anything can be made to fit with enough negative camber.
Not sure if this is gonna help anyone but if you're trying to get an idea of fit, try this:
Grab a plumb-bob on a string. Hang string over guard so it is in the centre of the wheel. Measure from string to wheel and string to the most bulging part of the tyre.
This will tell you how much room you have, on factory camber settings, before the tyre starts to poke.

Tyre and wheel advice

PG68

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Unkle Ed

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SteamPlane

Car, beer & whisky nerd

Myke

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stasik-a4

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PG68

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Burkey

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PG68

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GT Nick

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05STNG

05 STNG

Unkle Ed

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Nong

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Burkey

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Nong

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Burkey

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