Jump to content
SAU Community

Recommended Posts

  • Replies 49
  • Created
  • Last Reply

Top Posters In This Topic

I've used the tyre calculators before to check rolling diameter, trouble is there is no allowance for wheel size and therefore potential stretch. That one did have the info on recommended size though which was useful, looks like I should be going for 255s.

Any other thoughts or experiences are useful though!

I'd agree that 245 is way too narrow for a 9.5" rim.

I am somewhat biased though as I do not like the stretched look at all.

Try this rim/tyre calculator.

http://www.rimsntires.com/specs.jsp

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5961140
Share on other sites

i know im goin to get flamed to death for saying it, but IMHO the federal 595 is highly over rated on a daily drive car. they are great for a weekend warrior or if u do ALOT of hard cornering. but for the daily commute i'd suggest something thats a little better in the wet and maybe wears better. i also agree with the other guys a 245 is pretty narrow on a 9.5 inch rim. id be goin a 265 to protect the rim a little better.

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5962498
Share on other sites

I like a slight stretched look and to help fit in the guards a little better. On my 180sx the rear runs a 9.5 with a 235-45. On the M35 the new rims are 9" so I will run a 245-45-18 but would really prefer a 235 but the diameter isnt as nice as the 245. I would never run a 265 on a 9.5" rim.

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5963391
Share on other sites

i'd beg to differ

pythagorus yo!

also, www.willtheyfit.com is one of the best tire size calculator i've found

it cant affect the rolling diameter. all youre doing is changing the angle of the sidewall. isnt pythagorus' theorum for triangles?? :P

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5964167
Share on other sites

it cant affect the rolling diameter. all youre doing is changing the angle of the sidewall. isnt pythagorus' theorum for triangles?? :P

But wouldn't changing the angle of the sidewall change how the tread sits and therefore the rolling diameter? Or is that a really dumb question?

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5964264
Share on other sites

It would change the dia by a small amount only, didn't you guys do geometry at school, think of a tree that is 10 mtrs high, standing upright it is 10 but when on a lean it is slightly less high, the length though doesn't change but the height does, the ground is the fixed point as in the rim being the fixed point.

Dia may be changed by a mil or two maybe, post up the height of the side wall and the size of the gap from vertical.

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5964377
Share on other sites

it cant affect the rolling diameter. all youre doing is changing the angle of the sidewall. isnt pythagorus' theorum for triangles?? :P

changing the angle of the sidewall would change the height from the bead to the tread

immagine house, the wall height is 2m, the length of the roof could be 2 meters too but the height of the wall is 2m because its vertical but because the roof is on an angle the heigh of the roof may only be 1m

i think what would happen in real life would be that the circumference of the tyre would be under a little bit of compression and the sidewall would be put in tension (otherwise the tyre would wrinkle like you said, this is also neglecting the internal pressure of the air and the load from the car's weight)

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5964491
Share on other sites

well, using this website is the perfect example. the circumference cant be changed.

www.willtheyfit.com

put in the EXACT same tyre size into the boxes, just change the rim width and tell me what you get with rolling diameters for both sets of values.

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5967116
Share on other sites

195 185

Diameter 559.1mm 570.1mm

Circumference 1756.5mm 1791mm

Poke 81.6mm 81.6mm

Inset 121.6mm 121.6mm

Speedo error 0% -1.93%

Reading at 30mph 30mph 29.42mph

Reading at 60mph 60mph 58.84mph

Ride height gain 0mm 5.5mm

Arch gap loss 0mm 5.5mm

diameter changed? not by much but it did. everything else is the same except width

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5967128
Share on other sites

something still isnt right about it.

if you were to measure the side wall between the two (stretched/not so stretched) the wall length would HAVE to be different for the rolling circumference to change. you can see that in the image. which means that instead of being 195/45, it may be 195/47(for argument sake) im pretty sure the rubber wont physically stretch to meet the exact circumference.

you may be very right. just doesnt make sense to me.

lol not strange that your right. strange by the law of physics. it simply doesnt agree with the pythagoras theorem which actually can be used. the hypotenuse would actually be larger with the larger width wheel, for the circumference to be exactly the same.

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5967158
Share on other sites

how can you use pythagorus when youre talking about a circumference?

i know you mean the cross section of the wheel/tyre, but you have to remember you cant make a circle smaller or larger unless you add or subtract to it, thus affecting the tyre size, then it would change the size of the sidewall to accomodate the larger/smaller rolling diameter

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5967173
Share on other sites

i think i know what your trying to get at with the amount of rubber being the same around the circumference. and it does make sense.

but unfortunately rubber works differently. you are actually subracting from the circle(circumference) by adding a wider wheel, back to hypotenuse, for a wider wheel to = the same rolling circumference as thinner wheel, there has to be a larger hypotenuse(wall). the only way that can happen with the same spec tires, is by physically stretching the rubber material in the wall, which would make it go from a 45 -> 47 theoretically.

I think mythbusters is needed lol

Link to comment
https://www.sau.com.au/forums/topic/373541-tyres/page/2/#findComment-5967195
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I'm on the AD09, strictly on the street. They are a very nice tyre, have done ~16k km and are near the end, might make it to 20. They are, in my opinion, very much just a street tyre. I wouldn't expect them to be equivalent to some of the others in your list on the track. Although I'd be pleasantly willing to be surprised. My memory of the AD08Rs is vague enough, due to the passage of time, that I shouldn't try to compare them, but I feel as if the AD09 is not quite as "sporty" as the AD08R was.
    • There's a difference between "selling" a product to someone (which, if you walked into a workshop or bricks and mortar store and bought and walked out with it, is just the act of buying and selling) and rolling your buggy into a workshop and having them fit non-roadworthy stuff to the car. And for the latter, let's ignore any potential legal loophole arguments that the armchair lawyer might want to make to differentiate between supplying your own parts to be fit by the workshop or getting the shop to supply and fit. The workshops that have been dealt with in the US for this are in the latter category. It would be near impossible to try to charge/attack/criminalise a shop for selling "for off road use only" parts to someone unless those things were intrinsically illegal in their own right, or had other legislation wrapped around them, such as there is for guns, pharmaceuticals, etc. Well, no. And you knew your argument was silly when you made it. And there is. it might be somewhat harder in Vic, but then that's the price you pay for electing the long list of (unts that you have to run the whole shit hole**. But otherwise, you can put an aftermarket or otherwise tunable ECU into a car and get it run through the whole shebang of emissions testing as part of an engineering cert and, so long as the tune is "locked" afterwards, then that modification is on the list that is approved on the cert. But....it is an expensive process. ** Of course, the (unts who make up a large proportion of the population that eternally try to get around the rules are also a part of the problem and the reason that you end up with draconian rules in the first place. By contrast, SA was founded and the government and civil service set up and run by very sensible types (largely German) who set up good structures that enabled a lighter touch of government on the somewhat better behaved population. it is only more recently that we have followed the rest of Australia down the criminal drainhole of penal colony behaviour and now we have to catch up with mobile phone cameras and so on.  
    • Not specifically the revamp Toyos. In the past I've used Nitto NT01s, which were essentially the same compound as R888 with a different pattern (that's what the internetz said, so just be facts). I did like the NT01, progressive fade, didn't go from grip to 0 grip in a split second. If you look at the serious street/track guys, most are either on Cup 2, A052, A050, AD09, CR-S or AR-1.  
    • I have one of these! It is absolutely useless. It provides not nearly enough force on the bolt, it just slips over anything that is not finger tight. And if it's finger tight, you can use your fingers.
    • You have to take photos of the car in Victoria with a timestamp. So if you have big aftermarket turbo in your engine bay, your car is simply not getting a RWC and you'll be doing a lot of returning to stock, and re-modding after about 90 days (because cars that have had a RWC can be audited after the fact). The law I'm kinda ambivalent about. I can see the logic and the writing on the wall, Cobb etc would be well known for selling to 'wink wink off the street usage' but in the real world everyone knows what they do and where they end up. It'd be like someone selling guns in Australia but "only to people who have a proper licence" but selling them outside of Bunnings instead of sausages to anybody. Like RWC's, and VASS's and EPA, this is enforcement of the actual existing rules. I haven't looked into it but there (should) be a way for people to legally pass their tuned car to be within the rules if they can prove they pass emissions laws that are applicable. If there's not then that's another story.
×
×
  • Create New...