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vinniman said:
go and measure the tyre height on your ride
We all know that the overall height is shortened due to the contact patch flattening the bottom of the tire. When any overall diameter is quoted, say 32" MAX , for instance, the only area that matters is the upper half of the tire, which largely remains the same. Similary for width, we quote these knowing they are close and/or have rubbed on other member's vehicles - factoring in +/-%, it's best to stay away from these so the average user doesn't have any issues.
 

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Discussion Starter · #22 ·
FYI - installed the 20's with 285/50's and there is no issues. Checked the gaps and I've got about 4mm of space between the tire and suspension components.

The tire sits just under 30 5/8" high and at the top, measured at its widest point, still looks 285 (28.5cm). Will need to check the width better - but over all seems fine

Thanks to all for your comments and help.
 

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2006-2009 Range Rover Sport
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Frisco_TX_RRS said:
Will do - need to wash it. Real dirty with the rain ......
Congrats Frisco! Dirty pictures are fine!

4mm though...phew
 

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Sweet as Brother.

Glad my estimate of 30.72" versus your actual of 30.625" was dam near spot on ! GooseyLoosey - is that close enough for You ?

Cheerio,


Vinniman
'88 Highline
Perth, W.A.
 

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Terrific Vinni...with 4mm to spare too :thumb:

Btw, either my comprehension is improving, or your post above was more coherent than usual, because I actually understood it. :D
 

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Discussion Starter · #28 ·
So do you guys think approx 4mm is ok? The tires were not balanced right by discount tire - so they did a road force and seems to be ok. Dallas has lot of concrete roads which are not as smooth and slights bumps as the black top roads so at 70 there is a shimmy at some locations. I think this tire does pick up more than your sporty road tire.

So here are the final dimensions with some pics of the tire installed.

Height - 30 5/8 " (30.625)
Width measured at its widest point using a caliper at Discount Tire: 11.5" (292.1 mm)
Approx 4mm of space between the tire and suspension mechanisms

[attachment=4:mn3qih5o]newwheels 005.jpg[/attachment:mn3qih5o]

[attachment=3:mn3qih5o]newwheels 004.jpg[/attachment:mn3qih5o]

[attachment=2:mn3qih5o]newwheels 009.jpg[/attachment:mn3qih5o]

[attachment=1:mn3qih5o]newwheels 010.jpg[/attachment:mn3qih5o]

[attachment=0:mn3qih5o]newwheels 011.jpg[/attachment:mn3qih5o]
 

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Puurfect FTR !

"If you can't doubt him - crown him" [Quote 50 Cent-P.I.M.M.P.] Look forward to the aural upgrade as we say in Oz - Full Noise ?

Cheerio,


Vinniman
'88 Highline
Perth, W.A.
 

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Nice, nice!
Frisco_TX_RRS said:
Thank you umbertob. Who wants to take be off roading now .....
Man, I want to get out there so bad. :p
 

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Wow, this thread had a little of everything. Now I know where all those PM's from Frisco were coming from. :)
Sorry I was late to the party... but sounds like it's over anyways. For the record: Drevs now has 20" OE stormers with 285/50's, no spacers, and also has comprehensional difficulties with our friend from another hemisphere. That tire/tyre setup is great and I run it year round.
 

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Discussion Starter · #35 ·
Drev's - do you have any vibration \ steering wheel shimmy at higher speeds ...
 

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gooseyloosey said:
vinniman said:
By going to a 285mm broader section of tyre will not be an issue for the overall running clearance around the front fenderwells, since the wider wheels allow a flatter footprint and slightly reduced diameter of 30.72" in rolling diameter which is cool as Bro' ?
Good luck on your trip Vinni.

Maybe on the flight over you can check my calculations on something because I don't understand how moving the rim width 0.5 in one way or the other makes such a drastic change in tire diameter. Based on the 9 in rim the 285 tire per the previous posts is 31.2 in dia. You say moving this tire to a 9.5 in rim reduces the diameter by almost 0.5"?

Since you're a civil engineer, just for fun, calculate the difference in sidewall angle assuming the sidewall on the tire mounted on the 9" rim is vertical. Then recalculate the apparent sidewall height by moving the bead out 0.25" on either side. I assumed a 3" sidewall height (the angle changes about 5 degrees), and I can't get close to a 0.5 in change in overall diameter. What don't I understand?
Rim width does not effect tyre diameter, at least not significantly. From whatt I've read most tyres have 'steel belts' running around the circumference of the tyre. I.E under the tread. These steel belts won't get smaller because of a wider rim. The accepted industry norm is that for every +/-0.5" in rim width compared to the industry 'norm' rim width the sectional width changes by +/- 0.2", but, no change in diameter.

So, if the tyre manufacturer says the sectional width of a tyre is 11.20" on a 9" wide rim, if you're using a 10" wide rim the sectional width would approximately be 11.2 + 2x0.2"= 11.60", static tyre diameter stays the same. This is the tyre diameter when inflated but not under load(eg with the weight of the car on it).

Check here to get it explained properly, I'm only a quantity surveyor, more affectionatley known as a 'Brick Counter.' ;)

http://www.tirerack.com/tires/tiretech/tirespecskey.jsp

I'm currently trying to squeeze 275.55R20s under my SC wheel arches, but, I'm using 25-30mm wheel spacers. The rims are OEM Supercharged 20x9.5" with a 53mm offset.

So based ion the manufacturers info the sectional width of the 275.55R20 on a 8" wide rim is 11.22". So on my 9.5" the sectional width should be approximately 11.82" but an unloaded(static) diameter of 31.9" so approximately 0.6" taller than the 285.50R20 FTR hased used. Therefore the radius will be approx 15.95" or 0.3" taller than FTR's radius...

Based on this I reckon the 275.55R20s will fit with the spacers, however, before making this, as FTR said, US$1,000 leap of faith my local tyre dealer is going to mount a 275.55R20 on a rim and check for any rubbing/ contact points etc. He'll do this both with and without the spacers and under articulation to ensure everything is ok. If not back to the drawing board...

Will let you peeps know how it works out...

FTR forgot to mention the tyres look great :thumb: :thumb: Have you had any issues yet?

Cheers


Guy
 

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Discussion Starter · #38 ·
Guyzer73 said:
Will let you peeps know how it works out...

FTR forgot to mention the tyres look great :thumb: :thumb: Have you had any issues yet?

Guy
Thanks Guy, No issues with the tires. I love the ride, Did some pretty fast driving last week and it handled well.

With your 275/55 - I think you may get some rubbing on the wheel wells - but not sure - hope it works out.

I was told to stay away from spacers for 2 reason - safety, that the lugs now don't go in as deep and less thread holding the tire, 2nd it could cause wheel bearing issues.

BTW - I just had my whole interior taken out except the hoodliner and had soundkill (sound dampening) put on where ever there was metal - the whole floor and 4 doors. The car is quiet now !!! The resonance is pretty much gone and I can take conference calls again. In addition all the little rattles and squeaks, they are gone - sounds better than my mercedes with everything fitting nice and tight. My sub and speakers sound better. I would have gone with dynamat but was told that it is filled with silicone an of everything ripped out and soundkill applied - will post them along with the vehicle detailed with the new shoes on.
 
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