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Discussion Starter · #1 ·
I currently have an Active Autowerke SC Dinan Badged 325xi lowered on FK G77 Coils. The cars intended use will be autocross, and I was wondering whats the largest tire size you can fit underneath it.

I'm completely okay with rolling, pulling, cutting and putting over fenders on the car, as the interior of the car will most likely be stripped.

I would love to put a 17x8.5 with 255/40r17's on all 4 corners as the car will run in the SM class.

Does anyone have any experience with putting wide tires underneath the XI?

Thankyou!
 

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Welcome to E46F.

First, what are the Exact tire "Rules" for the SM class that you'll run ?

Realize this: It's not about how much meat you can stuff in there, it's about the quality of the meat you can stuff in there.

So depending on the grip level of the tire in question, sometimes a 235/40-17 or 245/40-17 is a better choice.



Rob43
 

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I checked a style 68 staggered setup. The goal for xi tire choice is equal circumference even if the transfer case will tolerate a 3% difference. On the front - 225 45R17 (circumference 1993mm) / On the back - 255 40R17 (circumference 1997mm).
 

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I checked a style 68 staggered setup. The goal for xi tire choice is equal circumference even if the transfer case will tolerate a 3% difference. On the front - 225 45R17 (circumference 1993mm) / On the back - 255 40R17 (circumference 1997mm).
Do you Auto-X this setup ?



Rob43
 

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Discussion Starter · #5 ·
I checked a style 68 staggered setup. The goal for xi tire choice is equal circumference even if the transfer case will tolerate a 3% difference. On the front - 225 45R17 (circumference 1993mm) / On the back - 255 40R17 (circumference 1997mm).
Is the front tire choice smaller because it's tough to fit a 255 up front or just because its staggered?

I would prefer to go to a square set up and not induce more understeer than I expect the car already has.
 

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Discussion Starter · #6 ·
Welcome to E46F.

First, what are the Exact tire "Rules" for the SM class that you'll run ?

Realize this: It's not about how much meat you can stuff in there, it's about the quality of the meat you can stuff in there.

So depending on the grip level of the tire in question, sometimes a 235/40-17 or 245/40-17 is a better choice.



Rob43
The tires will be the 200 tread wear Bridgestone RE71R, so the quality of the meat will be top notch. SM class is unlimited tire size I believe.
 

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The tires will be the 200 tread wear Bridgestone RE71R, so the quality of the meat will be top notch. SM class is unlimited tire size I believe.

OK, that's good that you've chosen the number one tire you can currently buy. If it were me:

I'd buy a square set of 245/40-17 because I believe that the weight difference of 1 pound & the better gearing of the 24.7" (245) tire will completely outweigh the .3" difference in tire width between the 255 to to 245.

If your budget allows, buy a set of D-Force LTW5 in 17 X 9" sizing, they weigh in at about 16.7 lbs. Here's a pic of mine with newly mounted 235/40-17 Toyo RA1's for DD use.


Rob43
 

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Discussion Starter · #8 ·
OK, that's good that you've chosen the number one tire you can currently buy. If it were me:

I'd buy a square set of 245/40-17 because I believe that the weight difference of 1 pound & the better gearing of the 24.7" (245) tire will completely outweigh the .3" difference in tire width between the 255 to to 245.

If your budget allows, buy a set of D-Force LTW5 in 17 X 9" sizing, they weigh in at about 16.7 lbs. Here's a pic of mine with newly mounted 235/40-17 Toyo RA1's for DD use.


Rob43
So do I need to modify the car in anyway to run 245/40s, also what offsets of wheels should I be looking for? I've autocrossed for years, just decided picking this supercharged XI would be worth a shot and fun.
 

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So do I need to modify the car in anyway to run 245/40s, also what offsets of wheels should I be looking for? I've autocrossed for years, just decided picking this supercharged XI would be worth a shot and fun.
You shouldn't have to mod anything as long as your wheel et's are correct, I believe the D-force LWT5 17 x 9" are 41 et.

http://www.willtheyfit.com/



Rob43
 

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Discussion Starter · #11 ·
OP I'm going to be putting Apex Arc-8's that are 18x9 et 42 with 255/35/18 on my car. That is for DD/Performance. If it was a track setup 17x9 is what I would go with.

Rob is spot on if this is pure performance go with the lightest wheel and quality rubber.
I want to do 17x9, but wheel options at that are just a little to pricey for me to reason with, mainly because I don't even know if I like this car for autocross. I've autocrossed a Subaru Legacy GT with a bit of mods and 235 direzzas, an Opel GT on slicks and fox body mustang on slicks.
 

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I want to do 17x9, but wheel options at that are just a little to pricey for me to reason with, mainly because I don't even know if I like this car for autocross. I've autocrossed a Subaru Legacy GT with a bit of mods and 235 direzzas, an Opel GT on slicks and fox body mustang on slicks.
Honestly I would rather have a 325i or 330i for autocross. My 330i out handles my 330xi. Its lighter and puts more power to the ground. The only advantage to the xi is in the wet. If you do like the e46 BMW as a platform the wheels you invest on the xi will swap over to a rear wheel variant.
 

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Discussion Starter · #13 ·
Honestly I would rather have a 325i or 330i for autocross. My 330i out handles my 330xi. Its lighter and puts more power to the ground. The only advantage to the xi is in the wet. If you do like the e46 BMW as a platform the wheels you invest on the xi will swap over to a rear wheel variant.
I know :( I would love to have a 330ci and that was considered for a long time, but the budget doesn't allow and I had got this 325xi for a steal at $2500, I do plan on owning a rear wheel drive bmw in the future whether its an E36 or E46, or hey maybe i'll get lucky and find the keys to a M4.
 
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