Stretching tires and staggered setups

[unknowna4]

I know it's safe to run staggered setups as long as the rolling diameters are close enough. My question is will stretching the same size tires across wheels that are 1 in wider cause such a change in rolling diameter that it will cause a problem? Say like a 215 on a 8.5" up front and a 215 on a 9.5" the rear? Thanks

[unknowna4]

No one?

[fixn2xlr8]

I woudnt do it, you have IIRC about 4% worth of diff from font to back to mess with, but I would highly recomend rinning the same size on all 4 corners. Its an AWD car, no need for a staggered setup besides the bling factor.

[Klum00]

215 on a 9.5 wheel is definitely gonna be STRETCHED...

why not run 235 on all of them, or 235 up front and 245 in the back?

[unknowna4]

215 on a 9.5 wheel is definitely gonna be STRETCHED...

why not run 235 on all of them, or 235 up front and 245 in the back?

Please refer to original question.

[unknowna4]

No one knows if this will create a larger than 4% difference?

[Klum00]

Please refer to original question.

please use a calculator and high school math to figure it out yourself.

[JDM EJ1 95]

please use a calculator and high school math to figure it out yourself.

how you gonna calculate the difference in diameters according to stretch without actually measuring the physical height in person.especially with the difference in tire construction from company to company and model to model.. please tell me?


im running 9.5s in the rear and 9s in the front with 235s all around.. ran them all summer like that and have had no issues.


EDIT... hold on i have my wheels and tires right next to me.. ill measure the actual height difference. itll give you somewhat of an idea

[Quattrocket]

I found a calculator on a miata site a while ago, not sure where it was exactly.

[jakecro]

I found a calculator on a miata site a while ago, not sure where it was exactly.

Calculators:

http://www.rims-n-tires.com/rt_specs.jsp

http://www.miata.net/garage/tirecalc.html

[JDM EJ1 95]

just measured my setup as listed above..albiet on carpet... and not the most exact form of measuring.. they came out to less than a quarter inch of difference.


so to be safe.. id assume that my 1/2 inch of stretch difference is comming out to about a 1/4 inch or 1/8 inch of actual diameter difference.

[unknowna4]

just measured my setup as listed above..albiet on carpet... and not the most exact form of measuring.. they came out to less than a quarter inch of difference.


so to be safe.. id assume that my 1/2 inch of stretch difference is comming out to about a 1/4 inch or 1/8 inch of actual diameter difference.

Thanks for actually helping man.


Everyone else, fail. You can't calculate the stretch of a tire with highschool math so please don't be a jackass. Those calculators don't take into effect the width of the wheel and hence the stretch of the tire which is what my original question pertains to.

[Klum00]

how you gonna calculate the difference in diameters according to stretch without actually measuring the physical height in person.especially with the difference in tire construction from company to company and model to model.. please tell me?

seriously? i could have figured this out in 9th grade.

http://www.csgnetwork.com/righttricalc.html

tire construction shouldn't come into play since he should be comparing the same brand/model of tire just various widths.

feel free to PM me for if you need further explaination of basic trig and/or geometry.

[unknowna4]

seriously? i could have figured this out in 9th grade.

http://www.csgnetwork.com/righttricalc.html

tire construction shouldn't come into play since he should be comparing the same brand/model of tire just various widths.

feel free to PM me for if you need further explaination of basic trig and/or geometry.

Dude use common sense man, side walls aren't triangles and can lay more flat(because rubber isn't steel or something and deforms under very little pressure.) depending on tire pressure, width of wheel, the caracterisics of the rubber ect. Don't talk to me about math I've most likely done way more than you (I'm a mechanical engineering student.)

[road race s4]

Why do you guys run wider rims in the back? Don't these cars under steer from the factory? Putting wider rims/tires in the back would make the matters worse.

And that's not even taking into consideration different rolling diameters between front and back if you go with different size tires.

[unknowna4]

For looks, I won't run these wheels at the track and don't race around town so I don't care what my street setup handles like really.

[JDM EJ1 95]

Why do you guys run wider rims in the back? Don't these cars under steer from the factory? Putting wider rims/tires in the back would make the matters worse.

And that's not even taking into consideration different rolling diameters between front and back if you go with different size tires.

and have you read the post really.. its diff width wheels.. but same size tire.. = same contact patch.. the only thing you have to take into consideration is the offset and track width..

[JDM EJ1 95]

an idea what my setup looks like.. i have more pics if your interested.


Shot with Canon EOS DIGITAL REBEL XT at 2008-10-24

[Klum00]

it only took me 15 mins to make this diagram to explain everything. anyone with half a brain could have figured this out in 5 minutes.

[JDM EJ1 95]

it only took me 15 mins to make this diagram to explain everything. anyone with half a brain could have figured this out in 5 minutes.

you really still havent compensated for stretch at all... X gets smaller as you stretch farther... its really not that hard to understand...


like i said.. WITHOUT actually having the tire/wheel in front of you.. there is NO way to know exactly what X will be in a stretched scenario.. especially like i said with the difference in tire construction from model to model.


so dont act like a bigshot mathematician or an asshole.. because u just posted a diagram of what every standard tire size calc will do for you...


until you can tell me how you in fact do an accurate equation for a stretch scenario.. then dont come off as condecending to people that are looking for the exact info i just stated.

[unknowna4]

I don't think you really understand the complexities of a tire mounted on a wheel, many variables change when the tire is extreamly stretched that effect the rolling diameter of the setup.
But it doesn't matter anyway, I got the answer from a helpful member and everything will continue as normal on AZ and people will make post claiming to have knowledge and answers to subjects that are beyond their comprehension. Thanks anyway.

[road race s4]

and have you read the post really.. its diff width wheels.. but same size tire.. = same contact patch

they came out to less than a quarter inch of difference.

so to be safe.. id assume that my 1/2 inch of stretch difference is comming out to about a 1/4 inch or 1/8 inch of actual diameter difference.

Yea I read the post but how is it = same contact patch when you measured it and got a 1/4 to 1/8th difference?

[JDM EJ1 95]

Yea I read the post but how is it = same contact patch when you measured it and got a 1/4 to 1/8th difference?

in rolling diameter? ohh come on are you telling me youre going to notice a 1/8 inch difference which doesnt even come close to a 1/8 difference in the actual contact patch.


if you notice a difference in hard data or even in the drivers seat... then by all means you should run a race team considering you can feel such miniscule changes..


and btw.. i just measured my rolling diameters on hard flooring and it pretty much is only 1/16th of an inch off front to rear.. and that oculd be anything... tire wear maybe.


i guess were only oging to see any noticeable differences in rolling diameters when you start getting into big stretch differences... like maybe 11 inch with a 235 compared to a 9 inch with a 235.

[code7rpd]

JDM EJ 1 95: what is your ride height?

[JDM EJ1 95]

i dont exactly know a number... its decently low.. but the pics are all with my winter height.. itll be about an inch lower come summer.


Shot with Canon EOS DIGITAL REBEL XT at 2008-10-24

stockers


Shot with Canon EOS DIGITAL REBEL XT at 2008-09-23

[Klum00]

you really still havent compensated for stretch at all... X gets smaller as you stretch farther... its really not that hard to understand...


like i said.. WITHOUT actually having the tire/wheel in front of you.. there is NO way to know exactly what X will be in a stretched scenario.. especially like i said with the difference in tire construction from model to model.


so dont act like a bigshot mathematician or an asshole.. because u just posted a diagram of what every standard tire size calc will do for you...


until you can tell me how you in fact do an accurate equation for a stretch scenario.. then dont come off as condecending to people that are looking for the exact info i just stated.

jesus, the ENTIRE diagram shows you how to calculate X as the tire is stretched! obviously X changes, its a VARIABLE. just plug everything else in and you figure out how much the tire area of the rolling diameter changes. if you still can't understand what's going on you're beyond help.

i'm not trying to come across as a math expert here. as i stated from the beginning, this is basic high school math.

and yes, i realize that rubber bends. but you're talking about milimeters here, not going to make a noticable difference. and i'll say it again, stretching a 215 on a 9.5 is just ridiculous. 245's are stretched to fit 9.5 wheels.

[Klum00]

I don't think you really understand the complexities of a tire mounted on a wheel, many variables change when the tire is extreamly stretched that effect the rolling diameter of the setup.
But it doesn't matter anyway, I got the answer from a helpful member and everything will continue as normal on AZ and people will make post claiming to have knowledge and answers to subjects that are beyond their comprehension. Thanks anyway.

way beyond my comprehension, WAY BEYOND. do the tires go on the wheels? what is the inner tube made of? can i fill my tires with my bike pump?

i was trying to be helpful in telling you that the stretch you are suggesting is absurd, but you wanted to be a dick about it.

oh and i'm fairly certain i've mounted more tires than you have.

[unknowna4]

way beyond my comprehension, WAY BEYOND. do the tires go on the wheels? what is the inner tube made of? can i fill my tires with my bike pump?

i was trying to be helpful in telling you that the stretch you are suggesting is absurd, but you wanted to be a dick about it.

oh and i'm fairly certain i've mounted more tires than you have.

Thanks anyway

[JDM EJ1 95]

either way what it comes down to.. is a half inch difference in stretch.. at least in my case is pretty much a 0 inch difference in rolling diameter. and i dont think youll actually start noticing problems until you get to the point of say like a 10 inch wheel compared to an 8 inch wheel.

[haus4]

way beyond my comprehension, WAY BEYOND. do the tires go on the wheels? what is the inner tube made of? can i fill my tires with my bike pump?

i was trying to be helpful in telling you that the stretch you are suggesting is absurd, but you wanted to be a dick about it.

oh and i'm fairly certain i've mounted more tires than you have.

LOL, just reading this is pretty funny. But Klum you are correct with your way and JDM is correct with just measuring.

I personally would never run a staggered set up on an AWD car. Maybe you can get the overall rolling diameter to be < 4% but did you take into consideration of the added stresses of turning, more horsepower, and the differentials locking up under certain situations. Mainly that is more a worry if its during the winter, but still. Just a consideration. I dont know if you have another center diff or rear diff laying around, but I know it cant be cheap.

OP - if your an Engineering student, whats the problem here? This is simple compared to some of the work/math you do everyday.

[unknowna4]

Haha way too much work everyday I don't want to do anymore