: What needs to be done to fit 20x12 & 335 30 20 on a Coupe?



LV_V
04-11-12, 02:42 PM
Anyone have any experience trying to fit a large rear wheel and tire setup on the V Coupe? I'm not opposed to having some minor metal fabrication work done to the inside of the wheel well to accommodate...

I'm thinking Forgestar CF5 20x12 rear wheel with a +50 offset (extend an extra 15mm outward and 35mm inward compared to stock 10"), coupled with a Michelin Super Sport 335 30 20 tire.

I plan on modding to 600-625rwhp immediately and ~750-800rwhp within a year or so. I want as much grip as possible. Don't plan on lowering it, so the additional 1" in OD shouldn't be a huge issue. If this rear setup will fly, the front will be a 20x10 with +54 offset (extend an extra 10mm outward and 16mm inward compared to stock 9") and a 275 35 20 or 285 35 20 Super Sport tire.

This is going to be strictly a street monster. No drag strip. Potentially some casual road course sessions, but not planning for that. I know someone who can hook up a near cost deal on the Michelin tires, thank god.

Thoughts?

LV_V
04-11-12, 09:48 PM
Not a V and not the CF5, but here are pics of the same widths and tires on a GTR: http://www.forgestar.com/blog/?p=1797

LV_V
04-12-12, 04:08 PM
Well I'm going to take the plunge and order these in the next few days and it takes 4-6 weeks to manufacture these wheels. I hope to be buying my V this coming week, so just write off any sleep for the next few weeks while the mod fever has a tight grasp on me.

LV_V
04-12-12, 06:56 PM
Vendor says the 20x10 deep-concave won't clear the brake caliper (I kind of suspected this would be the case), so I'm dropping to the semi-concave 20x9 +35 in the front and will go either 265 35 20 or 275 35 20 Super Sport (I'll order the tires when the wheels ship in 4-6 weeks). Still planning on the 20x12 in the rear with the 335 30 20 Super Sport. Vendor pushed the offset on the rear to +45 and claims it will be flush with the fender, so now its a waiting game! I pray it all fits...

LV_V
04-13-12, 04:09 PM
Ordered the Forgestars from Howey Industries and got a smokin deal. They went back and forth with the Forgestar techs and guarantee that these will fit the V Coupe. The tire situation, on the other hand, they can not guarantee. I want to run the Michelin Super Sport 335 30 20, but it MAY be too wide; this will be a trial and error situation unfortunately. Not sure what tire I'm going to switch to if this 335 30 ends up being too wide. This rear offset is pretty aggressive so I have my doubts.

Ended up with the Forgestar CF10's in textured black 20x9 +35 & 20x12 +45 and black Forgestar lugnuts shipped for $1885.

Similar wheel setups:
CTS-V Sedan (smaller widths/different color): http://www.forgestar.com/blog/?p=1718
GTR (similar rear width/same color): http://www.forgestar.com/blog/?p=1708
GTR (similar rear width/same color): http://www.forgestar.com/blog/?p=1692
Camaro (similar rear/same front/different color): http://www.forgestar.com/blog/?p=1649

And some info from Forgestar: http://www.forgestar.com/blog/?p=1616

Super light, only 24.6lbs for a 20x10. If you can't tell, I'm pretty pumped for these to arrive.

Darnell
04-15-12, 05:11 PM
Glad you got something you like. I really like the idea of doing a F14 on the front and an F14F on the rear.

CoppeR
04-15-12, 06:56 PM
Thats one tall tire thats gonna throw off the speedo.

http://www.discounttire.com/dtcs/infoTireMath.dos

LV_V
04-15-12, 07:03 PM
The speedo displaying 2.5mph higher at 65mph is the least of my worries :)

----------

And I'm considering going with an Invo 345-25-20 which is actually a little thinner than the Super Sport 335-30-20. I'll keep this updated as I order tires and receive the wheels.

obd2
04-16-12, 11:30 PM
Ordered the Forgestars from Howey Industries and got a smokin deal. They went back and forth with the Forgestar techs and guarantee that these will fit the V Coupe. The tire situation, on the other hand, they can not guarantee. I want to run the Michelin Super Sport 335 30 20, but it MAY be too wide; this will be a trial and error situation unfortunately. Not sure what tire I'm going to switch to if this 335 30 ends up being too wide. This rear offset is pretty aggressive so I have my doubts.
Ended up with the Forgestar CF10's in textured black 20x9 +35 & 20x12 +45 and black Forgestar lugnuts shipped for $1885.

Similar wheel setups:
CTS-V Sedan (smaller widths/different color): http://www.forgestar.com/blog/?p=1718
GTR (similar rear width/same color): http://www.forgestar.com/blog/?p=1708
GTR (similar rear width/same color): http://www.forgestar.com/blog/?p=1692
Camaro (similar rear/same front/different color): http://www.forgestar.com/blog/?p=1649

And some info from Forgestar: http://www.forgestar.com/blog/?p=1616

Super light, only 24.6lbs for a 20x10. If you can't tell, I'm pretty pumped for these to arrive.




I have a 2011 coupe and tonight i decided to do some measuring concerning the 20x12 with 45mm offset. The stock rear coupe wheel is 19x10 with a offset of 40mm, and the sedan is 19x9.5 with a offset of 56mm, i found the coupe and sedan offsets via google search (someone please correct me if these are wrong) The wheel 20x12 with the 45 offset will have extra 30mm wider toward the side of the strut housing and 20mm wider toward the outside edge of the wheel (wheel face).

Armed with a calliper gauge and tape measure i decided to check for clearance because i am very interest in getting 12 inch wheels also.
My verdict is as follows
- I would not extend my wheel further that 10mm over the stock 19x10. By extending 10mm MAX to the outside edge (Wheel face) will make the wheel flush with the coupe rear fender. I am sure of this.

-i measure the inward clearance (side of the strut housing) and looks like i have 40mm clearance for a 20 inch wheel only; not the same for 19 (the bigger the wheel the more clearance you will have on a coupe) The tight spot is the control arm at the front of the wheel nearest the door. My inner measurement is very close but not exact so please check it yourself.

I think the best offset would be 20x12 with a 55 offset might work (it will be tight). I do agree with the vendor 335 30 20 are to wide. I think a 13in section width tire is the widest you can go with a 12in wheel and if the tire has the protected rim lip i think it will stick out too much.

The 20x12 55offset will add 10mm to the wheel face and 40mm to the inner (strut side)
hope this helps

LV_V
04-16-12, 11:38 PM
The 12" +45 wheel will stick out 20mm further than the 10" +40 stock wheel. I agree that this is several mm too far, but Forgestar seems to think it will work. If it turns out being too aggressive I can mill it down a few mm? Not what I want to do, but what more can I do.

Thanks for measuring. Hoping to pick up my V Coupe tomorrow!

obd2
04-16-12, 11:54 PM
The 12" +45 wheel will stick out 20mm further than the 10" +40 stock wheel. I agree that this is several mm too far, but Forgestar seems to think it will work. If it turns out being too aggressive I can mill it down a few mm? Not what I want to do, but what more can I do.

Thanks for measuring. Hoping to pick up my V Coupe tomorrow!

You are right and i have corrected my post. I am sure you are realy looking forward to you coupe
enjoy

LV_V
04-25-12, 05:44 PM
I posted something similar on a few different boards earlier this month, but have received no responses, so I thought maybe I could get some good feedback here. I have made the decision to go with the 345 25 20 Nitto Invo tire because it is 0.6" slimmer than the Michelin Super Sport 335 30 20, from what I have found online. After I get the wheels & tires installed I'll make the decision to lower it, most likely with the D3 comp springs. What do you guys think?


Stock CTS-V stance with 285-35-19 on 10" rim (my offset pushes the wheel face out 20mm further than this):
http://www.techgatz.com/wp-content/uploads/2011/04/2011-Cadillac-CTS-V-Coupe-front-view-2.jpg


Lowered CTS-V with 295-30-20 Proxes 4 on 10.5" rim (my offset pushes the wheel face out 1mm further than this):
http://www.vossenwheels.com/gallery/FileUpload/Gallery/Cadillac_CTS_VVSCV3_7ca.jpg


GTR with 335-30-20 Super Sport on 12" rim (same rim model and size I have coming):
http://www.forgestar.com/blog/pics/redgtrcf102.jpg


Vette with 345-25-20 Invo on 12" rim (same manufacturer of rim and same size with the Invo tire):
http://www.forgestar.com/blog/pics/gc6z063.jpg

rangerrob
04-26-12, 11:29 AM
the 345/25 profile looks much better than the 335/30, hopefully it fits for you! can't wait to see the end result! what's the current ETA on these, 2-3 more weeks?

LV_V
04-26-12, 12:22 PM
They quoted 4-6 week build time. I ordered on 4/13. Hopefully they don't come too soon because I haven't even bought my V yet lol!

D3 Outlet
04-30-12, 08:48 PM
We've done 20x12 but running an undersize tire 325/25R20 thats the only way to fit a 20x12. We also tried running a 335/30R20 Pirelli Rosso which is a lot bigger over all diameter than factory tires, there was no way to fit that tire with out heavy fender modification.

LV_V
04-30-12, 11:10 PM
We've done 20x12 but running an undersize tire 325/25R20 thats the only way to fit a 20x12. We also tried running a 335/30R20 Pirelli Rosso which is a lot bigger over all diameter than factory tires, there was no way to fit that tire with out heavy fender modification.

Thanks for that info. I chose the Invo because it runs significantly thinner than other makes. I found a measurement comparison that showed the Invo 345 was thinner overall than a Pirelli and Michelin 325. The lack of a true rim protector is a large part of it IMO. We shall see... I'll definitely be reporting back here every step of the way with pics! And I just purchased your competition springs to complement the new wheels and tires.