Tire Stretch Question?
02-10-10, 05:47 PM
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Tire Stretch Question?
I searched & didnt find what I was lookin for. Ive got a 98 es300. What width tire will provide a moderate stretch on my 7.5" wide rims? Currently running 225/40zr18...... gonna drop down to ???/35zr18.
Last edited by 86'ed; 02-10-10 at 08:20 PM.
02-10-10, 06:08 PM
#2
Lexus Champion
the usual thing is 80% range wheel width to tire tread spec for high performance lowpro tires
all you gotta do is the math
IF :
85% > [7.5inches/215mm] > 75%
THEN you should be in great shape for response and handling.
Stock is around 6.0inches/205mm, beccause the the tires are not low pro, the tendency is to be near 70%.
"For example: For tires with aspect ratios from 80 to 50, the measuring rim, also called the design rim, is specified to be 70% of the section width. For tires with an aspect ratio less than 50, the measuring rim is 85% of the section width." *Dunlop Tire company
so, if you have 7.5 rim width, 215m tires, and 1 inch = 25.4 millimeter , then what you get is 8.47inches.
7.5inch/8.47 = .88 = 88%
so, in conclusion, you can use those tires on the those wheels but only if the aspect ratio is like 50 or 45. Since your car is normally going to require bout 60 on a 15" with 215 width to keep the speedo reasonable, your 215/60R15 will be a **** poor choice. if you have 215/55/R16 you still shouldn't, if you have P215/50R17, then you're good, even P215/45R18 would be good if not better. Since you didn't any info other than 215, I had to say all the stuff just now. Plus, it helps you and others to get it.
Don't forget to adjust tire pressure, no it won't be very easy, and that's the first scientific part, then you gotta track it or test it out and see if a little higher or lower is better. Maybe you can find a car with similar weight and tire specs and just copy that [cars tire PSI spec] for starters.
Generally, you just take the max load rating and the psi [listed on the websites out there for that specific tire you buy, tirerack lists it on their site for instance] at that load rating. Then, figure out how much weight is on the front tires and rear tires. This is done by finding the curb weight [not the GVWR , that is something else]. You take the front/rear weight [sometimes in owners manual or spec sheet or elsewhere, or measure it yourself with the device. Even though the front will be higher than what the rear would need, set the rear to the same as the front. You can then adjust from here for any changes in traits -- also, you need a minimum of about 22PSI anyway, just a heads up, not that this weird scenario is probably going to happen when you do the calculations - and you obviously never go above the max inflation pressure. rule of thumb is that 95% of cars fall in the range of 25 to 35 PSI. This is also why you need to keep the load rating [and the speed rating the same or higher than/as OEM spec]
JUST an example for a fictional unicycle tire: max load of tire is 100 lbs @ 15psi. the weight of the unicycle [lol] is 50 lbs. the minimum spec the tire must be inflated [llcoolpass or other tirepert told you when you bought the unicycle] is 7psi. You would inflate to 7.5 PSI by calculation, and since more than 7 psi, that's safe by advice from tirepert.
Also, if your tires in question are like really old [more than five years old] and/or have little crack lines all over them, do not use them. sorry, they're garbage = take to tire recycler [like autoshops take them].
*dunlop tire company tire info http://www.dunloptires.com/care/widthRatio.html
all you gotta do is the math
IF :
85% > [7.5inches/215mm] > 75%
THEN you should be in great shape for response and handling.
Stock is around 6.0inches/205mm, beccause the the tires are not low pro, the tendency is to be near 70%.
"For example: For tires with aspect ratios from 80 to 50, the measuring rim, also called the design rim, is specified to be 70% of the section width. For tires with an aspect ratio less than 50, the measuring rim is 85% of the section width." *Dunlop Tire company
so, if you have 7.5 rim width, 215m tires, and 1 inch = 25.4 millimeter , then what you get is 8.47inches.
7.5inch/8.47 = .88 = 88%
so, in conclusion, you can use those tires on the those wheels but only if the aspect ratio is like 50 or 45. Since your car is normally going to require bout 60 on a 15" with 215 width to keep the speedo reasonable, your 215/60R15 will be a **** poor choice. if you have 215/55/R16 you still shouldn't, if you have P215/50R17, then you're good, even P215/45R18 would be good if not better. Since you didn't any info other than 215, I had to say all the stuff just now. Plus, it helps you and others to get it.
Don't forget to adjust tire pressure, no it won't be very easy, and that's the first scientific part, then you gotta track it or test it out and see if a little higher or lower is better. Maybe you can find a car with similar weight and tire specs and just copy that [cars tire PSI spec] for starters.
Generally, you just take the max load rating and the psi [listed on the websites out there for that specific tire you buy, tirerack lists it on their site for instance] at that load rating. Then, figure out how much weight is on the front tires and rear tires. This is done by finding the curb weight [not the GVWR , that is something else]. You take the front/rear weight [sometimes in owners manual or spec sheet or elsewhere, or measure it yourself with the device. Even though the front will be higher than what the rear would need, set the rear to the same as the front. You can then adjust from here for any changes in traits -- also, you need a minimum of about 22PSI anyway, just a heads up, not that this weird scenario is probably going to happen when you do the calculations - and you obviously never go above the max inflation pressure. rule of thumb is that 95% of cars fall in the range of 25 to 35 PSI. This is also why you need to keep the load rating [and the speed rating the same or higher than/as OEM spec]
JUST an example for a fictional unicycle tire: max load of tire is 100 lbs @ 15psi. the weight of the unicycle [lol] is 50 lbs. the minimum spec the tire must be inflated [llcoolpass or other tirepert told you when you bought the unicycle] is 7psi. You would inflate to 7.5 PSI by calculation, and since more than 7 psi, that's safe by advice from tirepert.
Also, if your tires in question are like really old [more than five years old] and/or have little crack lines all over them, do not use them. sorry, they're garbage = take to tire recycler [like autoshops take them].
*dunlop tire company tire info http://www.dunloptires.com/care/widthRatio.html
Last edited by llcoolpass; 02-10-10 at 06:27 PM.
02-10-10, 06:24 PM
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Im on Ksport coilovers currently running 225/40zr18 and cant go much lower unless I drop down a tire size and run a stretched tire.
Last edited by 86'ed; 02-10-10 at 08:21 PM.
02-10-10, 06:29 PM
#4
Lexus Champion
I recommend you use closer to P215/45R18 because of the stock speedo/trans/abs being calibrated for P215/60R15. width of the tire to the rim is 'ok' based on the math [you did do the math right?] whcih gets 88%, but that's getting really high like corvette or higher, perhaps a bit too extreme of low profile [ie low aspect ratio: 35] and extreme risk for damage and blowout from road imperfections. so I dont recommend it overall for those three reasons, no. I would rather see your car's rims in P215/45R18 or P215/50R17 shoes.
Last edited by llcoolpass; 02-10-10 at 06:36 PM.
02-10-10, 06:36 PM
#5
Lexus Champion
wait I assumed what your car was since you left it out. so you have 1998 lexus es 300 with 16" rims, that came with p205/60R16?
if so, go with your preferred brand of [mine are dunlop and kumho] P215/50R17 with speed rating V or higher, and load index 91 or 92.
these would do it[highperformance rain and summer and some snow] for you: http://www.tirerack.com/tires/tires....0&autoModClar=
if you gotta use thos 18" rims, then you have ought to use P225/40R18 but man you drive where I drive and I imagine they and the tires would be fried in no time from road problems. http://www.tirerack.com/tires/tires....omCompare1=yes
notice the higher load index. in this case, you probably end up in the 26-29 psi range my guess is. I'm cringing imaging the potholes and your tires meeting each other at 40 mph. hehehe
if so, go with your preferred brand of [mine are dunlop and kumho] P215/50R17 with speed rating V or higher, and load index 91 or 92.
these would do it[highperformance rain and summer and some snow] for you: http://www.tirerack.com/tires/tires....0&autoModClar=
if you gotta use thos 18" rims, then you have ought to use P225/40R18 but man you drive where I drive and I imagine they and the tires would be fried in no time from road problems. http://www.tirerack.com/tires/tires....omCompare1=yes
notice the higher load index. in this case, you probably end up in the 26-29 psi range my guess is. I'm cringing imaging the potholes and your tires meeting each other at 40 mph. hehehe
Last edited by llcoolpass; 02-10-10 at 06:45 PM.
02-10-10, 07:27 PM
#7
Hardly stretched on there.
I was running a 225/40/18 on an 8" and it was flush with the lips of the rim.
I am running a 225/45R17 on the 17x7 and it bulges slightly
So in your case the 215 will do nothing really...
------
Go with a 205/40/18 or
205/45R18 to be closer to OEM rolling diameter, otherwise the other tires won't do much for you as i stated.
Edit; just to put it into perspective.
Rims pictured are 18x8.5" with 215/35/18 rubber... Barely any stretch on them.
I was running a 225/40/18 on an 8" and it was flush with the lips of the rim.
I am running a 225/45R17 on the 17x7 and it bulges slightly
So in your case the 215 will do nothing really...
------
Go with a 205/40/18 or
205/45R18 to be closer to OEM rolling diameter, otherwise the other tires won't do much for you as i stated.
Edit; just to put it into perspective.
Rims pictured are 18x8.5" with 215/35/18 rubber... Barely any stretch on them.
Last edited by 01LEXPL; 02-10-10 at 07:32 PM.
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02-10-10, 08:15 PM
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Your a wealth of info llcoolpass & I understand what your saying (for the most part 
) but thats not the direction Im headed with my ride. In order to dump this biotch to the ground I gotta run a low pro tire with stretch. I appreciate your input though! 
01LEXPL, So 205 would provide a moderate stretch? Are some brands better for stretching than others?
I appreciate everyones input!
) but thats not the direction Im headed with my ride. In order to dump this biotch to the ground I gotta run a low pro tire with stretch. I appreciate your input though! 01LEXPL, So 205 would provide a moderate stretch? Are some brands better for stretching than others?
I appreciate everyones input!
02-10-10, 08:42 PM
#10
Your a wealth of info llcoolpass & I understand what your saying (for the most part ) but thats not the direction Im headed with my ride. In order to dump this biotch to the ground I gotta run a low pro tire with stretch. I appreciate your input though!
01LEXPL, So 205 would provide a moderate stretch? Are some brands better for stretching than others?
I appreciate everyones input!
) but thats not the direction Im headed with my ride. In order to dump this biotch to the ground I gotta run a low pro tire with stretch. I appreciate your input though! 01LEXPL, So 205 would provide a moderate stretch? Are some brands better for stretching than others?
I appreciate everyones input!
toyo t1-s
dunlop sp9000
dunlop sp8080e
falken fk451
& A cheap but decent tire is the Nankang NS-2's.
The dunlop's being 'more' popular in the drifting crowds, so they tend to be more durable.
02-10-10, 09:58 PM
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Last edited by 86'ed; 02-10-10 at 11:55 PM. Reason: Cause I can!
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