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6K views 29 replies 11 participants last post by  Dreamin 
#1 ·
All,

Stock F1 EMT's are at 11k miles, I might get a few more thousand out of them (although they are at the wear bars). I have rotated 3 times so far, and attribute this to the above average wear I have attained from these tires (this includes about 200 minutes of track time at VIR).

After reading the how to widen your stock wheels thread:
http://www.cadillacforums.com/forums/showthread.php?t=35522&

And then looking at the pics that Wildwhl, and Dreamin posted

http://www.cadillacforums.com/forums/attachment.php?attachmentid=10200
http://www.cadillacforums.com/forums/showpost.php?p=346308&postcount=64

I am seriously considering going with the Goodyear F1 GS-D3's, in a 245/45YR18 Front / 245/40YR18 Rear configuration. I love the way the 275's look, and would be willing to give up a little bit of rear turnin stiffness (based on using the stock rim @ 8.5" with a 275, let me know if I'm offbase here). I also love the very agressive tread pattern on the GS-D3's. It just looks so serious, for lack of a better word.

I know this will introduce some overstear into the car's neutral handling.

I found a tire calculator that put the front tires at 26.68" diameter vs. a 26.66 rear diameter, so it looks good from that perspective.

My main concerns comes from the change in hadnling, and the basic inability to rotate the tires in this config. The front to back is not compatible, due to size, and the right left would also not be compatible due to the tread direction.

Questions:

1) Does anyone have any advice or experience with this type of application (perhaps covertte owners can chime in, as this would be close to their config). Will I chew through tires on the V if I don't rotate them?

2) Should I consider a non direction tread tire, so I can swap right to left, or will this give me little to no added tire life benefit?

3) How much will this upset the car's handling? I can live with a bit of overstear, as long as it is predictable, and doesn't trash the car's overall handling

4) Will going to 275's in the rear help or hurt the wheel hop issue?

5) Is this a bad idea?

6) Would I need any alignment changes if I went this way?


I've never had a high-po car before so tire shopping for one is new to me (is it obvious ;) )

Thanks in advance,

Chris
 
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#2 ·
I too plan to do 245-255 front, 275-285 on the stock rims soon.

But I think I will go with the BF good something something, the one with the weird tread pattern, it looks mean.

I am wondering the same about handling...I know it wont be any WORSE as far as st8 line acceleration.
 
#3 ·
If one goes the 275/245 route, just replace either the fronts or rears when they wear out. Over the life of the vehicle, the cumulative tire life won't be that much different.

Let's say a set of four stock 245 size tires that have been rotated often will last 10,000 miles. Over the course of 50,000 miles that equates to 20 tires.

Alternatively with the 275/245 combo, imagine never rotating the tires and only replace front or rear sets when worn. Over the 50,000 miles, one would need ~14 rear tires (7 sets @ 7143 miles each). Front tires, seeing less wear, would require 8 tires (4 sets @ 12500 miles each).

In this rough analysis, one can see rotating 20 tires to 22 "non-rotation-able" tires isn't a big deal over 50,000 miles. The extra two tires at $400-$600, amortized over 50,000 miles, are worth the added looks alone. :)
 
#5 ·
Depends what ones needs are. Power wise, with all the mods on my V now, I fear 275s aren't enough to truly hook up well. For a "straight-line" kind of guy - shoe horn in the largest meats on the rear possible.

For me, it would be tough to give up the chassis balance of the same size tires all the way around. Been thinking 255s on all fours lately. Another option I'm considering is having my 3-piece wheels wided in the rear and go 275/285/295. Where did I put those 315s at? :hmm:

Before I personally would put 275s on stock width wheels, I would need to drive it and see what it's like. For me, it's all about owning the corners AND the straights. :lildevil:
 
#7 · (Edited)
dannystang said:
Stealth your an engineer, what do you think of 245-275 on stock rims?

Or better yet 255 fr / 285 rear?
I second that question.

Also DS, what aspect ratio would you go with in this setup?

245/45/18 = 26.68 " diameter (STOCK)
255/45/18 = 27.04 " diameter
255/40/18 = 26.03 " diameter
265/45/18 = 26.39 " diameter
265/40/18 = 26.35 " diameter
275/45/18 = 27.74 " diameter
275/40/18 = 26.66 " diameter
285/40/18 = 26.98 " diameter
285/35/18 = 25.85 " diameter

I don't see a 255 that would fit good, and I don't think a 265/40/18 would fit (up front that is.)

-Chris

I'm assuming these diameters are good. I used the tire calc at http://www.net-comber.com/tirecalc.html Everything you see on the Internet is true, right? :D
 
#8 ·
I would guess you wouldn't be getting oversteer with a 245F, 275R setup. Yes, if keeping the stock rim width, the rears will "float" on the rim a little more. But with all that extra contact, it should still be harder to break loose in turns. I would guess understeer is going to be the more likely trait.

As for the serious looking tread, tires like the F1 GS-D3 and Toyo T1-S and Yokohama AVS Sport, the continuous "Y" type tread pattern, in general, doesn't have the same inherent cornering stability that other tires with continuous ribs have. Tires like the Pilot Sport 2 or the Continental Conti Sport Contact 2 has continuous rows which add stability in turn-in and all out handling, as a general rule. Obviously, other factors are involved in making a great handling tire. The continuous Y does give great water evacuation. And there's no doubt that many here are happy with the GS-D3 and T1-S.

As for rotating from side-to-side, that helps minimally in evening wear. But it does help. I don't think it makes a great difference, though. Front to back is obviously the most important. But as long as you don't mind keeping with one brand twice as long as usual, you'll be fine.
 
#9 ·
thebigjimsho said:
But with all that extra contact, it should still be harder to break loose in turns. I would guess understeer is going to be the more likely trait.
Sounds right. Dunno what I was thinking. Reversed my terms.

Would upgrading the front tie rods to something stiffer help compensate for the understeer? Or would this just chew up the tires? I'm new to all this, so be gentle.

-Chris

P.S. I had to read your ...evening wear... phrase a few times. I kept thinking of you in a little black dress. Is this wrong?
 
#10 ·
StealthV said:
Depends what ones needs are. Power wise, with all the mods on my V now, I fear 275s aren't enough to truly hook up well. For a "straight-line" kind of guy - shoe horn in the largest meats on the rear possible.
the difference going from 245 to 275 assrubber is quite astounding...part of that may be how bad the F1s sucked, part is the uber-pricey PS2s, part is the 19" maybe.
(As you know I beat the sh!t outta my car) I'm shocked how well the rears hook up now....so sure I'm down a bit on power compared to you, but the 275s rock. Do I want 295? HELL YEAH...but 275 just rocks.
Oh yeah, it didn't upset the handling either. No adverse pushing, oversteering takes concerted effort now...she just ever so slightly 4-wheels drifts now :cheers:

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#11 ·
#12 ·
dannystang said:
Damn I want these...

http://www.tirerack.com/tires/Sizes.jsp?make=BFGoodrich&model=g-Force+T%2FA+KDW+2&vehicleSearch=true&fromCompare1=yes&partnum=445YR8GFTAKDW2

Doesn't look like those sizes will work though :(

Any ideas?

Edit, These fit in rear? closest to diam.

285/40 YR18
101Y SL



300 AA A
http://www.tirerack.com/tires/Spec.jsp?make=BFGoodrich&model=g-Force+T%2FA+KDW+2&vehicleSearch=true&fromCompare1=yes&partnum=445YR8GFTAKDW21819 lbs.
51 psi
10/32"
31 lbs.9.5-11"
10"
11.4"
NA
27"
771
Don't sweat it too much. There are better choices out there.
 
#14 ·
275's in the rear to feel a little squirmy on the stock rims. BigJim seems a little squirmy in that colorful bonet :D

285/40 might fit as well - but to be honest 275 is enough. It isn't really that expensive to try out...and I didn't drive mine enough miles to be totally sold that they WOULD NOT work on the stock 8.5" wheels...but alas...they're off for widening anyway.

Still...I like the hat Jim :sneaky:
 
#15 ·
Dreamin said:
Which one is Jim... I'll never tell :canttalk:

Wait, I think I know.
 

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#16 ·
I'm getting to really like my 245 / 275 setup...

1) Car understeers a *little* more... but it is completely correctable with throttle. If the understeer was a little worse... applying throttle would simply make the front plow more... NOT SO with this setup... understeer is totally manageable. It's not as bad as I thought it would be... I wouldn't touch the suspension.

Where applying throttle isn't wise... i.e. narrow freeway onramp... yes the fronts start to squeal... but you can jump on the throttle much earlier at the the end of the onramp...

2) And the car is SO MUCH more confidence inspiring now... i dont know if this is the tires and their feedback / predictability... or the 275s in the back... or if its all in my head... but much less pucker-factor powering around corners.

3) I haven't tracked the car yet... but i'm positive it's faster thru the corners with the 275s (better lap times) I have tested on remote streets... with 275s in the back... and then threw on 245s in back (extra wheels i have with F1s)... and there is no comparision... i am completely sideways, powering around the same corner, at the same speed with the 245s in the rear... the 245s really scare me now. The 275s help with power-oversteer more than i thought they would.

...a glowing review... let me contradict myself a little... the car is NOT as balanced as with 245s all the way around... in 7/10-8/10 driving... the fronts start squealling first and rears stay planted... which is irritating. But at 8/10-9/10 and a little more work... the car is faster and more fun with the 275s. Does this make sense?

At this point... i'm VERY happy with this setup. :thumbsup:
 
#18 ·
Unfortunately, bench racing is harder for handling than it is for acceleration. Adding lateral grip to the rear will of course create understeer (or less oversteer, however you want to discuss it)... the question if how much and whether it is noticeable to YOU. If you spend alot of time on road courses or auto-X, then my opinion is that you will notice. If you drive very hard through the twisties - you may notice, as the car is set up more neutral than some others (like my last M5, which had the sort of staggering you mention). I also believe that you will be running under the minimum reccommended wheel width... something where a quick call to the tire maker tech line may provide useful advice.
 
#19 · (Edited)
trukk said:
Sounds right. Dunno what I was thinking. Reversed my terms.
Would upgrading the front tie rods to something stiffer help compensate for the understeer? Or would this just chew up the tires? I'm new to all this, so be gentle.
Personally, I think if you're new to all this then the first thing you need to do is just drive the wheels off the car stone-stock.

Go do a couple track schools and once you've had a chance to work up some real speed and get a feel for how the car behaves at the limit you can decide whether you and the car will be happy with more rear grip.

I'll just note that one of the CTS-V's advantages over a stock M5 is its relatively neutral chassis balance. The M5 is a pretty devoted understeerer in stock form.

The following comments are general remarks, not based on specific experience with the CTS-V:

a) Typically, more rear tire needs to be balanced out with a little more rear anti-roll bar to get the same relative front-to-rear balance. This is where something like the Dinan stage-3 package comes in for the M5.

b) The problem with putting big-ass front tires on a car is that they numb the steering a lot and vastly increase the car's tendency to 'tramline' or 'nibble' - that is, try to follow every little groove or imperfection in the pavement. You then become part of the landscape at your favorite chassis shop as you try out different combinations of toe, camber, and tire pressure to minimize it.

c) The only way you're going to rotate tires with a staggered setup and directional tires is to pop the tires off the rim, flip them around, and mount the wheel on the other side of the car. Unless you've got a tire guy working for you, it's significant effort, expense, and the risk of having your rims scraped up.
 
#20 ·
Dreamin said:
P.S. Mallett has a setup which fits 275s all the way around... this requires his custom-made front spindles.

This would be an UNBELIEVABLE setup... but it costs $6000. :mad:
There is another option. When I was speaking to Chuck about this setup, he mentioned that if you go with 265's (19 inch rims) all around - the front suspension (knuckle/spindle) doesn't have to be replaced!
 
#21 ·
I'm in the process of burning off the 245/45 GSD3's now. I will skip the required rotation to ensure their early demise. Ready for 275's now.
 
#24 ·
That's correct.
 
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