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Discussion Starter #1 (Edited)
So my GTOs in the shop right now, and when its done it should be making around 600 maybe more (edit: wrote it wrong before... currently i already have 500 to the wheels) to the wheels...
I'm buying new wheels and tires and I want to keep the wheels size at 18" but how wide can/should i go with them to handle that power?
 

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You're going to have to go wider than that. Mini-tub is really the only answer. Yes you can go 275-295 with the right suspension and fender work and the right wheels but that still wouldn't hold. I think you'd need 315-325s. What are you having done?
 

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Discussion Starter #3
Currently i already have done the cams, long tube kooks, forged front end (pistons, rods ect.) tvs 2300 magna charger (currently running about lbs of boost with a mild tune),
I'm going to be upgrading the pulley to about 11-12lbs of boost, upgrading the fuel system, probably getting upgraded cams (current cams were from before the s/c), and a performance tune.
Ill also be upgrading my suspension. Probably to this.. This is a quote i got for parts..

"BC Coilovers F&R with upgraded 8K/10k spring package: $999.99

X41771-LOVELLS POLY STRUT MOUNTS or ROADSAFE RUBBER MOUNTS (YOUR CHOICE). POLY WILL BE SENT UNLESS RUBBER IS REQUESTED.
X82047-LOVELLS FRONT RADIUS ROD BUSHING
N81099-LOVELLS REAR RADIUS ROD BUSHINGS
N51233-LOVELLS FRONT CONTROL ARM BUSHINGS
N92350-LOVELLS CROSSMEMBER MOUNTS
N61483-LOVELLS REAR CONTROL ARM BUSHINGS (1 KIT)
X63109-LOVELLS REAR CAMBER ADJUSTER
N92616-LOVELLS DIFFERENTIAL INSERT
LOVELLS SHOCK BUSHING
LOVELLS STRUT BOLTS
LOCK NUTS
Normal Retail Price $770.88...$706.00 Shipped...No Substitutions
IF BC RACING FRONT AND REAR COILOVERS ARE ORDERED AT THE SAME TIME...GET A $99.00 OFF.

Strut tower braces will not clear superchargers, thats why I havent included them

Total Package price with all incentives $1606.99"

As for the wheels, I'm buying brand new everything, wheels and tires... So should i just look for 18x10.5 for the rear and 18x9.5 for the front if the tires need to be that wide?
 

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18/275 rears-18/245 fronts I would also look at driveline and clutch Word of advise I have S/C motor 528RWP with stock tires and driveline it does not hook but I will probably not break the driveline, if it hooks you will break stock driveline as big HP finds the weakest part. Get poly motor and trans mounts if you do not have them, the short motor mounts will allow a BMR strut brace to fit. Good luck with project, should be a beast.
 

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Discussion Starter #5
18/275 rears-18/245 fronts I would also look at driveline and clutch Word of advise I have S/C motor 528RWP with stock tires and driveline it does not hook but I will probably not break the driveline, if it hooks you will break stock driveline as big HP finds the weakest part. Get poly motor and trans mounts if you do not have them, the short motor mounts will allow a BMR strut brace to fit. Good luck with project, should be a beast.
Thanks a lot, i will look into that.
Also you think that the 275 will be wide enough to grip/handle the power it'll be making?

(when it's all done ill post up pics/vids. its finishing up getting painted right now, range rover fuji white, with black accents)
 

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Sounds like a torque monster build. I don't think 9.5" will fit on the front. 8.5" seems to be the most common and 10.5 in the back is going to be really iffy too. Most go with 8.5" and 9.5". You can't get the tire back there that needs the 10.5" anyways. Getting a 10.5" with a offset that could stand a slim chance of working would probably take a custom wheel or using the coilovers adjusted to a jacked up 4x4 height.

I see you're getting the rear adjustable camber kit and coil overs. Not a big fan. Unless you're autocrossing it and know how to set it up. I'd rather just pick a spring height and go with it. If you have like a 20mm drop you don't need the rear adjustable camber, have the alignment challenges, the issues of them and can stick with the fixed bushings. It's your car but you're going for the extreme and that doesn't always work.
 

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18/275 rears-18/245 fronts I would also look at driveline and clutch Word of advise I have S/C motor 528RWP with stock tires and driveline it does not hook but I will probably not break the driveline, if it hooks you will break stock driveline as big HP finds the weakest part. Get poly motor and trans mounts if you do not have them, the short motor mounts will allow a BMR strut brace to fit. Good luck with project, should be a beast.
Exactly. I'd plan on at least $3,000-$3.500 in driveline parts. Clutch, drive shaft, stubs and half shafts would be my advise. I'm running everything except the half shafts. It's mostly been a money issue to upgrade but I consider the half shafts to be kind of like a fuse and break before the rear end. I picked up some used ones as a precaution if I break one at the track.
 

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Discussion Starter #8
Sounds like a torque monster build. I don't think 9.5" will fit on the front. 8.5" seems to be the most common and 10.5 in the back is going to be really iffy too. Most go with 8.5" and 9.5". You can't get the tire back there that needs the 10.5" anyways. Getting a 10.5" with a offset that could stand a slim chance of working would probably take a custom wheel or using the coilovers adjusted to a jacked up 4x4 height.

I see you're getting the rear adjustable camber kit and coil overs. Not a big fan. Unless you're autocrossing it and know how to set it up. I'd rather just pick a spring height and go with it. If you have like a 20mm drop you don't need the rear adjustable camber, have the alignment challenges, the issues of them and can stick with the fixed bushings. It's your car but you're going for the extreme and that doesn't always work.

Thats not definitely the suspension package i am going to get, just the main one I'm looking at as of now.. If you have any package you would suggest please lmk...

Also what tire sizes would you recommend for the 18x8 (or18x8.5) and 18x9.5 wheels? Also what offset?

Thanks!
 

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For the front most people get 235s and a some have finessed 245s. In the back you can go up to 265-275 with the proper fender work, rolling or cutting of the outer fender and a hammer massage on the inside fender. The offset for the front is around 35-40mm. If you get too close to the strut you can use up to 1/4" spacer to bring the wheel back out a bit so a little too much offset is better than too little. In the back a 9.5" would like to be in the 50-55mm offset range.

Just my observation but most guys with coilovers play with them a bit because they can but because your alignment changes they end up leaving it at whatever. Picking a height and sticking with it is by far the simplest. For handling and ride I like the 20mm drop. It lowers the center of gravity a little over 3/4", makes the tire look like it's in the right position looking from the side and still gives a forgiving ride.

There's not a lot of travel in the suspension as it is and if you take away a lot you either have to have a really stiff spring or you'll be slamming the bump stops on rough roads especially with weight. You also can use stock spec aftermarket dampers with 20mm. If you drop more than that you need a "shorter" set.

Also with 20mm drop the rear camber will still be fine. With a coilover "dropped" you need the adjustable camber control arm bushings and have the pain of adjusting them. Then if you raise it you need to adjust them again.

Beware of some people's claims that run larger. Yes they may have done it but something I found out a long time ago is the builds on these cars is different and what fits on one won't on another especially when you're pushing the envelope.

Kollar has the 20mm drop kit. It's even a bit cheaper and then you can pick whatever dampers you want. JMHO
 

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Re

Hockey first thing you gotta do is figure out what you wanna do with this car. Drag racing road racing. Either way if your gonna be beating the balls off the car. the main upgrades would be the drive line. If your going for the occasional beat around town than I would say the drive train could survive. Learn the car and find out what mods will work for what you wanna do with the car. This way you are not spending money over and over on mods. You already put a cam in it and now your gonna do this again when you go maggie. First thing I would check is to see if you cam you have will work with the maggie.------danfigg
 

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+1 on the rear end. I've broke a rear axle launching w/ stock power. Just for an idea, a buddy of mine is running a procharged 04 A4 making 601 rwhp. He's running 275's in the back on 17's with bags and gets no traction when he punches/launches it, even at 60 mph. Good luck with your build!
 

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Discussion Starter #12
Hockey first thing you gotta do is figure out what you wanna do with this car. Drag racing road racing. Either way if your gonna be beating the balls off the car. the main upgrades would be the drive line. If your going for the occasional beat around town than I would say the drive train could survive. Learn the car and find out what mods will work for what you wanna do with the car. This way you are not spending money over and over on mods. You already put a cam in it and now your gonna do this again when you go maggie. First thing I would check is to see if you cam you have will work with the maggie.------danfigg

The maggie has already been in since then end of last year, the cams were done about 2 years ago... I had it done by the vette doctors so I'm sure they would have said something if there was a problem with the two. But I'm sure i could also put a better one for the maggie then whats in it now.. I've only put like 1000 miles on it since the s/c work was done though because I'm getting body work done right now, then as soon as the body works done, its going back to the vette docs, for the fuel system, smaller pulley, (possibly cam) and suspension. Also as of now It's more just cursing and road, mostly around town, not drag, though eventually i will probably be taking it to the track, but not yet...
 

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I think you picked the wrong platform to run that kinda power. Gonna have to tube the rear to fit tires. I'm thinking an 11-12" wide rear wheel with some 315+ tires are going to be needed.

I wouldn't go any bigger then 8" in the front and a 245 tire.
 

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So my GTOs in the shop right now, and when its done it should be making around 600 maybe more (edit: wrote it wrong before... currently i already have 500 to the wheels) to the wheels...
I'm buying new wheels and tires and I want to keep the wheels size at 18" but how wide can/should i go with them to handle that power?
FYI - If you're wanting to increase the size of the tire contact patch to improve traction, you get more/better results from going "taller" than you get from going "wider". Going "taller" though does affect gearing.

Bear
 

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Discussion Starter #15
I think you picked the wrong platform to run that kinda power. Gonna have to tube the rear to fit tires. I'm thinking an 11-12" wide rear wheel with some 315+ tires are going to be needed.

I wouldn't go any bigger then 8" in the front and a 245 tire.

So unless i do tube it ill probably only be able to fit like a 9" wheel up to about 275 right?
And you don't think 275 would be enough at all?
 

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Discussion Starter #16
FYI - If you're wanting to increase the size of the tire contact patch to improve traction, you get more/better results from going "taller" than you get from going "wider". Going "taller" though does affect gearing.

Bear
but how much taller would i have to go to get the equivalent traction or better then 275 wide?
 

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Discussion Starter #17
Been also thinking, if i just keep the wheels i have on there now (all 4 RPM 505 18x8 with 38mm offset) and just get 2 new wider ones for the back.. Only issue i see is that i only see them in 18x.9 but the offset is only 38 still... So basically if i was to get that, then the rear tires would stick out.. correct?
 

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So unless i do tube it ill probably only be able to fit like a 9" wheel up to about 275 right?
And you don't think 275 would be enough at all?
My buddies C5Z is putting down very low 500rwhp and is running 305(10.50 wide wheel) Nitto r-comps(I believe 555R II) and can still roast the tires on a bad launch.

I'm basically a stock C5Z running a 295 summer tire(PS2) and the rear and wish I was a tad more grip.
 

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Discussion Starter #19
I'm gonna just mini tub the rear and put 315s or 335s back there... What offset for the rim should i be looking for now though? I'm assuming I'm gonna use a 10.5 rim..
 

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With 10½" wheels to keep the same distance to the outside you'd need a 80mm offset although a small amount less should work. Stock 8" wide wheels are a +48mm off set. Whatever you add in width you take half (10½" wheel is 2½" wider divided by 2 =1¼" X 25.4mm = 31.75mm additional offset) and add that to the original 48 and get 79.75mm. With rolling/cutting of the fenders what ever you gain there you can subtract from the offset. If you have enough room for the tire/wheel to come out an inch then you can subtract 25.4 from the 80mm to a roughly 55mm wheel off set. An inch is a lot to gain but there is a certain amount you can use anyways plus how far the fender lip is adjusted.
 
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