Attn: CapriRacer- specific question

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quote:
Stock tire size is 215-50-17 Z rated 0+ application is 225-45-17
Rim width issues aside, the correct Plus Zero upgrade is actually 235/45/17 in this case. 225/45/17 results in a diameter that is 2% too small.
 
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wantin150, There are several tire standardizing bodies in the world. In the US, it's The Tire and Rim Association (TRA), in Europe, it's The European Tyre and Rim Technical Organization (ETRTO), in Japan, it's The Japanese Autombile Tire Manufacturers Association (JATMA). These organizations set the tire dimensions, the load carrying capacities vs inflation pressure, AND the allowable rim widths. (There's a whole bunch of other stuff they do, too!) All these groups publish standards in the form of a book issued yearly. A tire manufacturer does not have to follow what's in the book, but it would be foolish not to, since these guys have done all the hard work. Every tire size has what we engineers call a design rim - a specific rim width - sometimes also called the measuring rim. This is what the dimensions are based on. But every tire size also has an allowable width range. All the engineers that sit on the technical commitees of the standardizing organizations have agreed that this range does not SIGNIFCANTLY affect the tire - except obviously for the physical dimensions. Having said that, tires are designed and tested on the design rim and it is ASSUMED that tires mounted on rims within the allowable range will not have SIGNIFCANTLY different results. Since it is impossible to test ALL tire sizes (TRA lists over 250 P metric sizes) in ALL possible rim widths (3 or 4 per size) for All tests (probably 10 common tests), a few sizes selected and tested to confirm the design - always on the design rim. Occasionally a vehicle manufacturer will specify a rim width that is not "design" (but within the allowable range) and require that all testing be performed on this width rim. Historically, these results confirm the validity of the assumption. Now to answer your specific question: A 235/45R17 has an allowable rim width of 7 1/2" to 9" Using a 7" rim tends to "arch" the tread and results in more wear in the center and some tracking problems - usually related to grooves or ruts in the road. However, both of these are affected to a large degree by the vehicle involved - some vehicles being more critical than others. Needless to say I don't recommend charting new territory when there are acceptable alternatives.
 

Quattro Pete

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Capri, are there also increasing risks of tire slipping from the rim during hard cornering when using a non-approved rim width, or is this a non-issue?
 
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quote:
Originally posted by Quattro Pete:
quote:
Stock tire size is 215-50-17 Z rated 0+ application is 225-45-17
Rim width issues aside, the correct Plus Zero upgrade is actually 235/45/17 in this case. 225/45/17 results in a diameter that is 2% too small.

True, but if the rim width is not "allowed" then the 235 is not even an option. The speed diff of a 245-45-17 is approx .46 mph which is a lot closer than the 225-45 at a 1.25 mph diff. The 235 is .33. All "comparisons" at 60 mph on OEM size. My whole point is that just because you "can", doesn't mean you "should". [Smile]
 
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quote:
Originally posted by Quattro Pete: Capri, are there also increasing risks of tire slipping from the rim during hard cornering when using a non-approved rim width, or is this a non-issue?
Also a very good point and is an issue of concern to me as well. And thank you both for your responses. Every day should be a learning experience.
 

Quattro Pete

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quote:
True, but if the rim width is not "allowed" then the 235 is not even an option.
Sure it is. It just means that you also have to get wider rims. [Smile]
 
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quote:
Originally posted by Quattro Pete:
quote:
True, but if the rim width is not "allowed" then the 235 is not even an option.
Sure it is. It just means that you also have to get wider rims. [Smile]

Uh yeah...duh. [Smile] I'm stuck on stock right now! I didn't even want to touch the offset issue. [Cheers!]
 
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wantin150, "Capri, are there also increasing risks of tire slipping from the rim during hard cornering when using a non-approved rim width, or is this a non-issue?" Only if the rim width is too width and then I think the problem will be the tire popping off the rim, not slipping. But normally it takes quite a bit of force get a bead to unseat when the tire is fully inflated.
 
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If you don't mind Sir, will you please settle a debate. As an Engineer, you design products to perform a certain way in a specific application with a little variancve allowed. Right? My question is this and I will try to be brief: Stock rim width is 7.0" Stock tire size is 215-50-17 Z rated 0+ application is 225-45-17 Some people want to run a 235-45-17. The min recommended rim width for this 235-45 is 7.5". What, if any, are the hazards for running this size tire on a rim .5" too narrow? I specifically ask you because of your past posts. Thank you in advance.
 
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quote:
Originally posted by Quattro Pete: What about sidewall flex? Does it increase (and hence negatively affects steering response) as you move away from the measuring rim?
Yes, sidewall stiffness increases when you move away from the measuring rim, but within the acceptable range of width, I think you'd have to be highly trained (experienced) to detect the difference. However, I think increased sidewall stiffness positively affects steering response in that the steering becomes crisper (occurs more rapidly). One other thought: Inflation pressure has more affect on sidewall stiffness (and therefore cornering response) that the tire itself does, so normal folks won't be able to set the pressure precisely enough to feel the difference in tires.
 
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CapriRacer - This is great info. I appreciate it. I have always wondered the same. A year after I purchased my 02 Camry SE, I found out that the "Dealer Installed Accessory" alloy rims I have on my car, actually came off an 02 Solara SLE, which uses 205/65(?)R16 tires, the rim width is 6 inches. The Camry on the other hand, uses 215/60R16 tires, which calls for Measured Rim Width of 6.5 inches. I was unhappy about it and did my research, it turned out every 215/60R16 tire allows 6.0 rim. So I didn't make a fuzz about it. I am assuming that using narrower rims in this car will decrease the over dimensions of the tires, and hence reduces the possiblity of rubbing the inside of the wheel well??? It also seems to reduce the chance of curbing the rims??? The manual calls for 29PSI normal and 35PSI for 100mph+ driving. I like the handling and MPG better at 35PSI better so I leave it there. Should the PSI be altered from factory spec because of the changed rim width?
 
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quote:
Originally posted by Jonny Z: ...actually came off an 02 Solara SLE, which uses 205/65(?)R16 tires, the rim width is 6 inches. The Camry on the other hand, uses 215/60R16 tires, which calls for Measured Rim Width of 6.5 inches. I was unhappy about it and did my research, it turned out every 215/60R16 tire allows 6.0 rim....
According to my book, an 02 Camry came with P205/65R15 T rated inflated to 29 psi front and rear, except for SE version that came with P215/60R16 V rated tires also inflated to 29 psi front and rear. An 02 Solara - which my book lists as a sub model of the Camry - came with P205/65R15 H rated inflated to 29 psi front and rear, except there was an alternative - P205/60R16 H rated inflated to 33 psi front and rear.
quote:
....It also seems to reduce the chance of curbing the rims???....
I wouldn't think that is enough of a change to really reduce the risk.
quote:
....The manual calls for 29PSI normal and 35PSI for 100mph+ driving. I like the handling and MPG better at 35PSI better so I leave it there. Should the PSI be altered from factory spec because of the changed rim width?
Not because of the rim width, but the P205/60R16 has a lower load carrying capacity than the P205/65R15, so the 16" needs more inflation pressure for the same load carrying capacity - and as you can see above, Toyota used 33 psi, so that would be a good starting point. I would recommend +3 to +5 over the placard, except that the placard ought to read 33 psi. Hope this helps.
 
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quote:
Not because of the rim width, but the P205/60R16 has a lower load carrying capacity than the P205/65R15, so the 16" needs more inflation pressure for the same load carrying capacity - and as you can see above, Toyota used 33 psi, so that would be a good starting point. I would recommend +3 to +5 over the placard, except that the placard ought to read 33 psi.
Capri, sorry I wasn't 100% clear. My car came with 215/60R16 mounted on 16x6.0 rims meant for 205/60R16 Solara tires. Does rim width itself change carrying capacity? Or is the above comment only valid for if I am actually driving with 205/60R16 tires.
 
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quote:
Originally posted by Jonny Z: ....Capri, sorry I wasn't 100% clear. My car came with 215/60R16 mounted on 16x6.0 rims meant for 205/60R16 Solara tires. Does rim width itself change carrying capacity? Or is the above comment only valid for if I am actually driving with 205/60R16 tires.
No, rim width doesn't affect the load carrying capacity (OK, maybe in theory!), but certainly the change in tire size does!
 
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