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NG900 & OG9-3 Performance, Mods & Tuning Covers Tuning & Performance modifications for the NG900 (1994 to 1998) & OG9-3 (1999-2002) & '03 Convertible

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  #1  
Old 19th July 2006
Silver Metallic's Avatar
Silver Metallic Silver Metallic is offline
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Default Hello, and Tire Size Question

Hello All-

I have been a lurker for a little while, but felt it was time to introduce myself now that I have taken the plunge. I just got a 2002 SAAB 9-3 2.0T SE HOT 5DR.



It's been wonderful so far. The previous owner took excellent care of it... but had cheap mis-matched tires on that were wearing on the insides. I decided I would have to fix that, so I upgraded to some Goodyear Eagle F1 GS-D3's. I had them on a previous car I owned, and loved the performance wet and dry, plus how they looked.



But here's where the story takes a twist, and I need your help.

I looked on-line for a Goodyear recommended place near me that sold these tires and found: http://www.americastire.com/dtcs/fin...Veh&vid=007043

Clicking that link shows that they state the "Original Equipment Tire Size" for a "2002 SAAB 9/3 2.0T SE HOT 5DR/CONV" is 205/50ZR16. That is what I bought and had installed.

A day later I find out that Goodyear and the door sticker of my car state the tire size as 205/55ZR16.

How bad of a mess-up did I make? The website states: "This number refers to the height of the sidewall, or the Aspect Ratio. It is a percentage of the section width. In this example, you would take 50 percent of 205 millimeters and this would give you the sidewall height." What will changing the profile from 55 to 50 do to the car?

Thanks for your help in advance, and nice to meet you all!

Last edited by Silver Metallic; 19th July 2006 at 04:50 AM.
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  #2  
Old 19th July 2006
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pete with a 9-3 pete with a 9-3 is offline
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welcome silver, nice motor.

the overall diameter of your standad wheel/tyre set would be 631.9mm.

the set you've fitted is now 611.4mm. my 9-3 standad was 615mm and is now on 17" rims with an o/d of 603.79mm.

so you're close to the standad height of a 98 - 2000 9-3. i would'nt worry you won't damage nowt. of course none of these calculations allow for tyre pressures which will change the height again.

ps. i've got the eagles on my rims also - one mean tyre
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  #3  
Old 19th July 2006
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StormCrow StormCrow is offline
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Basically it means that your speedo will be out slightly...

LINK HERE
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  #4  
Old 19th July 2006
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Thanks for the responces!

I also found this information on the Dunlop Care and Maintence page:

Quote:
ASPECT RATIO
Aspect ratio is the relationship of a tire's height to width when mounted and inflated on a rim of the correct size. Aspect ratios are expressed in section height as a percentage of section width in two-digit numbers (80, 70, 60) and are often referred to as a tire's series. For example, if section height/section width is 60, the tire is a 60 series.

This height to width relationship determines the shape of the tire on the rim, and, more importantly, determines the performance characteristics of the tire. If the sidewall height of a tire is reduced slightly, the sidewall stiffness is increased greatly.


Higher aspect ratios deliver:
- Greater deflection under load
- Softer ride

Lower aspect ratios deliver:
- Wider footprint
- Quicker response
- Less tire deviation or slip angle
- Lower flex rate
- Less deflection under load
- Harsher ride


A tire with a lower aspect ratio and stiffer sidewalls will transmit more force from bumps and irregularities in the road surface. A tire with a higher aspect ratio, with its more flexible sidewalls will provide a smoother ride because sidewall flexibility allows it to deform over the impact area, dissipating the energy.

Changing tires on a vehicle from one aspect ratio to another also influences section width, which relates directly to the load carrying capacity of the tire. The load carrying capacity of the original equipment tire must always be maintained or increased.

Anything that changes the tire's outside diameter also influences the vehicle's overall gear ratio, as well as the accuracy of the speedometer and odometer.

Another factor affected by change in aspect ratio and overall diameter is the tire footprint. Typically, a high aspect ratio tire will have a long, narrow footprint, while a low aspect ratio will have a short, wide footprint.

Finally, tire diameter/aspect ratio affects the input to the engine computers on some new cars, since vehicle speed is an input to these computers.

In other words, tire changes involving changes in aspect ratios should be made in consultation with your Dunlop dealer and reference to the vehicle's Owner's Manual.
I'm still slightly worried.
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  #5  
Old 19th July 2006
mike saunders's Avatar
mike saunders mike saunders is offline
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You're fine....

Don't worry about it.

With the slightly shorter sidewall, you'll feel a smidgen more bumps on the road, but you'll have better steering response.

The roads are generally good out where you are, so no worries there.
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  #6  
Old 19th July 2006
koniq koniq is offline
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yep would not worry about it I have the exact tire size you have described! and yes the bumps in the road are more apparent but should not be something to worry about, if anything you will have a more sporty looking tire (I run Dunlop Sport 01's)... and welcome to the forum!
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  #7  
Old 19th July 2006
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I'm surprised no one's mentioned it yet, but Saab did use 205/50R16 tires on some 9-3s. That was the stock size for all NG900s with 16" wheels, and stayed for a year or two on the 9-3 until they went to a slightly higher sidewall.
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Old 19th July 2006
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nilaszewski nilaszewski is offline
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Quote:
Originally Posted by Jeremy R.
I'm surprised no one's mentioned it yet, but Saab did use 205/50R16 tires on some 9-3s. That was the stock size for all NG900s with 16" wheels, and stayed for a year or two on the 9-3 until they went to a slightly higher sidewall.
Right you are, i had 205/55's fitted on my 97 900s with 9-3ss wheels, ones that stuck out futher because of the offset, and had no issuses with rubbing. I was suposed to be running 205/50's however.

Seriously, dont worry about it at all. I have a set of the F1's in my garage awaiting for the wheels i have ordered which should be here tomarrow.
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  #9  
Old 19th July 2006
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Silver Metallic Silver Metallic is offline
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Thanks for all the info!

I think I'm good to go. I even called Goodyear Headquarters customer service, and they said the latest info they got (directly from Saab they added) was that the car should be fitted with 205/50-16's. I find this really interesting in light of the fact their website says 205/55-16, and so does the door sticker. But who am I to argue with Goodyear themselves!

I'm glad it worked out this way!


Now to put the ZR rating to good use!
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