Slick sizing needed this time yall. 67' GS 400. factory lip on the qrtr's NOT rolled(yet???). Frame isn't notched either(again, yet???). What I need to know is, can I get something like a 30/31" x 9" in there with no mods to the frame of lip ? If I have to move anything I will move everything and stuff a big tire in it. But for now I am thinking something like a 8-8.5" rim but don't know what backspace to look for, and a tall 9'' slick . Can it work ? Someone has surely done this one............. Later...................
67 tire fit I use an 8.5 rearend from a 1971-1972 Skylark in my 67 GS and it is 2" wider than the weak original 8.2 rear. I had bad rubbing problems. I fixed it by doing 2 things. (1) I rolled the inner lips up. (2) I had my 15" Buick wheels Widened 1" by cutting just behind the center piece and welding a 1" spacer into it. Widening the wheels inside pulled the outer tirewalls inward and improved the tire ground contact as well (made a 7" wheel into an 8"). I now have 28x12.5x15 MT Street tires and hear harmless light rubbing on lumpy driveways only. Polygraphite bushings would help tighten this up. A rear swaybar will help too especially if it is a 1" bar. If the sides (body to tire clearance) is uneven, Loosen the frame/body mounts and shake the body side to side to center it and retighten it.Some rearends just don"t sit in the center of the wheel wells and have to be corrected. MT 28x9x15 slicks are small & would fit easily on my setup since I now have room for a foot wide tirewall to clear.They will likely fit yours too. Some circle track mechanics have the lathe to widen wheels. Ask at your local tracks and speed shops. As for spacing , measure inside a 15" Buick rally and add 1" if you have a 71-72 rear end and want custom wheels. On stock 67 rearend stay with stock Buick demensions. As for any tire larger than 28" diameter: talk to a good body repairman cause you"ll be going into the rocker and fender panels.
Gary, Thanks for the reply I appreciate it. So what you did was increase the back spacing an inch on a stock wheel. Was that a ralley wheel, or what ? Need to know what the backspace is so I can look into wheels. In regards to the tire size, the way I understand you, you DON'T think I will be able to go taller than 28" without modifying the wheel house ? I didn't want to if I didn't have to. So I may have a perfect set of wheel opening mouldings for sale to help fund the project now,lol. The 71' rear is the one I have, so we are along the same lines there. Sounds like you have done what I am gonna be working with, so any info you can forward is gonna be just whats needed. Thanks.............
Wheels, tires, & efficiency: Dave, My widened wheels are factory 15" Buick chrome ralley's. I think they are now between 5-51/2" backspaced but just measure one of your's and add 1". Tires: I don't think you really need to go extra large since many cars run 9 & 10 sec. 1/4 mile times on 28" tires. Just work on traction and converter efficiency by using this formula: Optimum 60 ft = 168 / Quarter mile MPH. If you come within .1 of the optimum figure, your doing GREAT! Example: if your MPH (on the motor) is 112 in the 1/4, your 60 ft would calulate 168 divided by 112 = 1.5 OPTIMUM. Look at what others are doing and you'll see that adding .1 ( 1.6 60 ft) is a realistic goal to shoot for at 112 MPH. Optimum is: the perfect converter, staging position, tires, suspension , track conditions, etc, and is hard to achieve. NOTES; If you run highway gears, low stall converter, TA radials, etc,your efficiency numbers will obviously be slower, so don't forget to add another .1 or.2 for these inefficient obstacles. However, anything that LOWERS top end MPH (fat tires, low tire pressure, poor wheel alignement, loss of power on top end, backing off the throttle too soon,etc.) will cause you to get FALSE HIGH (low number)efficiency readings. Using BENCHMARK NUMBERS such as this formula, will help you set goals and give you concrete compairisons against everyone else. You'll also know exactly WHO to talk to; (those who achieve efficient numbers with efficient vehicles) for further advice.
early 67's had narrow rear, midway through year..... Not all 67's had the narrow rear. I've had several 67's, and only one had the narrow rear, the other 3 car's had the same width rear as the 68-72 A body's. For what it's worth o No:
Thanks Tom, So whatcha think ? 30x9's fit or not ?? Just looking here for opinions and roads to travel. I dont want to roll or notch if I don't have too. And 10's are do-able on 9"s from everything I have seen/read.
30" tire fit I think any diameter over 28" will come too close to the rocker panel area of the wheel well. You could use adjustable lower control arms and lengthen them for more room but your driveshaft may need lengthened also. Other than all that, you'll have to do body work to make the wheelwell fit the tire.
wont you screw up your pinion angle by using adjustable lower control arms if you dont use adjustable uppers?. seems to me that you will end up pointing the housing in a downward direction o No: i run 26X8.5 X15 mickey thompson slicks on my 66 and without N20 i pull 1.7 60' times and with a 125 shot i can pull 1.4-1.55 60' without a traction problem. of course i have poly bushings. competition engineering adjustable shocks, sway bar and an air bag in right rear spring.
pinion angle Yes, You would need adjustable uppers as well. I should have thought of that. Seems your doing well with 26" tires, 28" should be more than enough. Your really hookin'. I would really like to know the exact ROCKER PANEL TO GROUND CLEARANCE you have front and rear on the 26" tires, and did you box your stock arms along with the poly bushings. My 67 GS has lousey traction but I'm still stock suspended and looking at all the posabilities. (I do have sway bar and air bag)
Hey guys, Feel free to keep the info flowing here. I am looking at being in the 700 hp range when done with this, thus the tire sizing concerns. This is a new animal for me and I AM watching. As far as the car goes, I will be dragging it in tommorrow and I have in my posession a set of 29.5x10.5 MT's on a 10'' rim now. And also a set of 30x9 GY's mounted on a 8 inch rim. Both will be tossed on, or attempted to be, and I will let yall know what I find out. I own both sets of tires so testing is no issue once I get the car dug outa storage,lol. Anddddd they both have maybe a half season left on them. So I will be buying new ones shortly. Thus the testing. Now if I could only find a 28x10.5 to use for some sizing..................Gonna keep looking. Will let yall know soon I hope. :TU: :TU:
