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Bill, as usual a thoughtful and thorough reply! It makes it obvious that choosing a tire is not that simple, with such a huge range of allowable widths.

Obviously Euromeisters come in a limited range of widths. I considered an 8" euromeister wheel on the front of the red car (with a 9" rear and a wider rear tire) but don't think there is room with the available wheel and it's "rear" offset.

Another way to make the point in favor of 7" front, 8" rear (over a 9" rear) is why would you stagger wheels front/rear by 50mm (2") and then stagger the tires by only 20mm by putting 225 front and 245 rear? In relative terms, that 225 is too wide for the 7" and the 245 is relatively narrow but it's a setup i see recommended once in a while.
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Old 05-16-2018, 05:10 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #81 (permalink)
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Quote:
Originally Posted by Marc Bixen View Post
This is a Red Line archive from Pete Zimmermann's "Used 911 Story". We've seen it all.
Not appropriate to this thread at all.

I had some japanese sandcast Fuch replicas on my car when I bought it; low pressure castings and I could see voids in the back of them. JLI was stamped on the back, I tried getting them balanced 2x and both times they had a pretty bad shake. Those wheels were garbage.

Euromeisters seem amazing by comparison, and I don't have the slightest fear they will break.
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Old 05-16-2018, 05:27 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #82 (permalink)
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Quote:
Originally Posted by Jonny042 View Post
Bill, as usual a thoughtful and thorough reply! It makes it obvious that choosing a tire is not that simple, with such a huge range of allowable widths.
correct

Quote:
Originally Posted by Jonny042 View Post
Obviously Euromeisters come in a limited range of widths. I considered an 8" euromeister wheel on the front of the red car (with a 9" rear and a wider rear tire) but don't think there is room with the available wheel and it's "rear" offset.
correct again, for front fitment an 8 needs to have an ET from 25 to 30

Quote:
Originally Posted by Jonny042 View Post
Another way to make the point in favor of 7" front, 8" rear (over a 9" rear) is why would you stagger wheels front/rear by 50mm (2") and then stagger the tires by only 20mm by putting 225 front and 245 rear? In relative terms, that 225 is too wide for the 7" and the 245 is relatively narrow but it's a setup i see recommended once in a while.
not really, the wheel stagger is only important in it's effect on tire stiffness and thus grip(or comfort) and this effect while noticeable when comparing the extremes of spec width are much less so w/ smaller increments.

The tire stagger is the more significant of the two, though the stretch factor is also present.

225/45 x17 spec is 7 to 8.5
245/40 x17 spec is 8 to 9.5
both are at the extreme narrow end when using 7 & 8 respectively

215/45 x17 spec is 7 to 8
255/40 x17 spec is 8.5 to 10

both are at or near the narrow end when using 7 & 9 respectively

215/45 & 245/40 on 7 & 8 are a good match but so is 7 & 9, maxed would be 8 & 9.5. The 7 & 9 incrementally improves rear grip, the 8 & 9.5 incrementally improve both ends. which way you bias depends on whether you want more or less over/under steer. Same goes for t-bar & sway bar selection. There are multiple ways to go each providing a slightly different influence on handling and ride quality

Tire OD will also affect handling and setup, It's far easier to fit shorter tires and far easier to setup the car when the tire ODs are equal
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Old 05-16-2018, 05:43 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #83 (permalink)
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Pinching / stretching tires also changes the timing in how the tire reacts. A 225 or 235 is pretty pinched on a 7", so the sidewalls cant outwards from wheel to tread. Under load, the sidewall will flip over as the tread is pulled towards the center of the wheel. This takes time and an astute driver will note the slight delay. You can use this as a tuning aid as well. As a driver I tend to have slightly too quick of inputs on the steering wheel. When I run my 225 on 7" up front, I notice it dampens my inputs more than my 245s on 9" front setup, which is a desirable effect in this case.



That's a 225 on a 7" and 245 (or maybe 255? I can't remember) on a 9". The fronts are actually pinched more, but there's a lot less load on them.

A slightly stretched tire (say, a 225 on an 8) is better supported by the wheel. It already has the sidewalls slightly like this \_/ if viewed from the front so the response is slightly quicker.
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Old 05-16-2018, 06:15 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #84 (permalink)
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Quote:
Originally Posted by Driven97 View Post
Pinching / stretching tires also changes the timing in how the tire reacts. A 225 or 235 is pretty pinched on a 7", so the sidewalls cant outwards from wheel to tread. Under load, the sidewall will flip over as the tread is pulled towards the center of the wheel. This takes time and an astute driver will note the slight delay. You can use this as a tuning aid as well. As a driver I tend to have slightly too quick of inputs on the steering wheel. When I run my 225 on 7" up front, I notice it dampens my inputs more than my 245s on 9" front setup, which is a desirable effect in this case.



That's a 225 on a 7" and 245 (or maybe 255? I can't remember) on a 9". The fronts are actually pinched more, but there's a lot less load on them.

A slightly stretched tire (say, a 225 on an 8) is better supported by the wheel. It already has the sidewalls slightly like this \_/ if viewed from the front so the response is slightly quicker.
My notes from back when this was current say you had 9ET33 w/ 245/40 x17 RS71(probably supposed to be RE-71)

but yes that is part of the 'foundation stiffness elements" lead to reduced slip angles which in turn lean to more grip and lower tire temperatures because the tire carcass is stiffer and flexes less.

The dual set point is subtle most drivers will never notice it. Cars w/ coilovers often have dual springs which cause the same sort of dual set point. It's best to avoid or minimize that.

People don't realize how much flex the tires exhibit

I love this pic of your car, and how much the tires are distorted, the tires look like they will pop off the outer beads, it shows why one shouldn't go much beyond spec,
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Old 05-16-2018, 01:55 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #85 (permalink)
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Quote:
Originally Posted by Driven97 View Post
Pinching / stretching tires also changes the timing in how the tire reacts. A 225 or 235 is pretty pinched on a 7", so the sidewalls cant outwards from wheel to tread. Under load, the sidewall will flip over as the tread is pulled towards the center of the wheel. This takes time and an astute driver will note the slight delay. You can use this as a tuning aid as well. As a driver I tend to have slightly too quick of inputs on the steering wheel. When I run my 225 on 7" up front, I notice it dampens my inputs more than my 245s on 9" front setup, which is a desirable effect in this case.



That's a 225 on a 7" and 245 (or maybe 255? I can't remember) on a 9". The fronts are actually pinched more, but there's a lot less load on them.

A slightly stretched tire (say, a 225 on an 8) is better supported by the wheel. It already has the sidewalls slightly like this \_/ if viewed from the front so the response is slightly quicker.
This is a good explanation, Matt. I prefer to run the 7&8 x 16s on my car with 205 on the fronts and 225s on the rear. In addition to sitting better on the wheel--stretched, as you say--they also weigh a lot less than wider tires, which aids in response a bit to at least offset the heavier wider wheels. At least they feel that way to me.
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Old 05-16-2018, 03:54 PM
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Thanks to Bill, I partly understand the implications of my choices. I had settled on 17 x 7 & 9 Euromeisters with 215 and 245 tires, and then I heard back from the Maxilite guy. He can offer 16 x 7 & 9 wheels at close to the Euromeister price.

Advantages of Maxilite 7-9/16:

They'd probably be lighter
I'd be back to 205/225 tires - lighter and less rolling resistance (more torque)

Advantages of Euromesiter 7-9/17:
More tire selection
Slightly better look (my taste)
Minimal torque loss
Perhaps more cornering grip (wider)

Hmmmm....

I'll come back here and scour the thread for a 7-9/16 versus 7-9/17 comparison, which Bill may already have posted.
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Last edited by Superman; 05-20-2018 at 04:15 PM..
Old 05-20-2018, 04:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #87 (permalink)
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Quote:
Originally Posted by Superman View Post
Thanks to Bill, I partly understand the implications of my choices. I had settled on 17 x 7 & 9 Euromeisters with 215 and 245 tires, and then I heard back from the Maxilite guy. He can offer 16 x 7 & 9 wheels at close to the Euromeister price.

Advantages of Maxilite 7-9/16:

They'd probably be lighter
I'd be back to 205/225 tires - lighter and less rolling resistance (more torque)

Advantages of Euromesiter 7-9/17:
More tire selection
Slightly better look (my taste)
Minimal torque loss
Perhaps more cornering grip (wider)

Hmmmm....

I'll come back here and scour the thread for a 7-9/16 versus 7-9/17 comparison, which Bill may already have posted.
Not quite
first 225/50 doesn't plat nice w/ a 9, max is 8

you need a 245/45 x16 for the 9. When I had 16s , 7 & 9 205/55 & 245/45 was a great choice, but these days 245/45 is rare;y found outside R rubber's ranks. Be sure that you can get the tires you want in that size,

Otherwise stick w/ 7 & 8 x16 and 205/55 & 225/50 or 205/50 & 225/45 x16
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Old 05-20-2018, 04:55 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #88 (permalink)
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Bill, I'm still thinking the 7 & 9 / 17 is the ticket. I just got my speedometer done and I don't want to send it back again due to a 225/45 rear wheel decision. Plus...that's a rare tire, as you say. Those Euromeisters look nice.
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Old 05-20-2018, 08:10 PM
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Quote:
Originally Posted by Superman View Post
Bill, I'm still thinking the 7 & 9 / 17 is the ticket. I just got my speedometer done and I don't want to send it back again due to a 225/45 rear wheel decision. Plus...that's a rare tire, as you say. Those Euromeisters look nice.
On an SC/Carrera the speedometer reading is correlated to the rear tire OD
OD for a 225/50 x16 is ~24.9"
OD for a 245/40 x17 is ~24.7"
less than 1% difference
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Old 05-21-2018, 04:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #90 (permalink)
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