Re: 275/60/15 on a Cuda (long)
[Re: davenc]
#888998
12/26/10 11:05 PM
12/26/10 11:05 PM
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Joined: May 2005
Posts: 598 NC, USA
davenc
OP
mopar
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OP
mopar
Joined: May 2005
Posts: 598
NC, USA
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The leaf springs on a Cuda are not parallel to the frame rails. With the 4.5" BS wheels in front of the axle there was 1.5" of clearance between the tire sidewall and the spring; behind the axle there was only 3/4" of clearance. Again I turned to the Moparts archives to see if there was clear consensus on how much clearance was needed to be safe. Unfortunately there were mixed opinions on this. In the end I decided that 1/4" of clearance behind the axle after going to 5" BS wheels was not going to be safe enough, again because it was a street car.
Some folks put B-body rears under an E-body to allow for more BS. I may consider that at some point as well, but if I did that I would go with a Dana, and there was no funds to undertake such a project at this time. The other option was to move the rear spring perches on the 8 3/4. That would violate my "nothing but bolt-ons rule", and besides, I was not up to welding, and didn't know anyone I would trust to do it either. I was stumped on how to make this work the way I wanted.
After pondering the dilemma for some time, I finally had an insight that lead to my current solution. There was plenty of leaf spring to tire sidewall clearance in front of the axle, and where I need the additional clearance was solely behind the axle. The wheelwell itself had more than adequate clearance for the 275/60/15. I realized that if I could pivot the leaf spring about the spring perch locating pin, then I might be able to use more backspace without having to cut off and re-weld the spring perches. Based on the stock E-body leaf spring dimensions (22" front segment, 35" rear segment), it appeared that if I moved the front eye of the spring OUT away from the centerline of the car by 1/2", then I would gain 1/4" of additional clearance behind the axle. If I could achieve that then I would have 1/2" total clearance between the spring and tire sidewall.
Moving the front spring segment towards the tire was a bit counterintuitive, but I was hoping that perhaps a front eye hanger from another body style would help. At that point I called the good doctor (DrDiff) to consult on the feasibility of what I was trying to do. He indicated that I could try to use his A-body 1/2" offset front hangers, mounted on the wrong side of the car to change the offset direction, and his E-body 1" offset rear hangers. The thinking was that there would be enough play in the arrangement to use the 1" offset instead of the 3/4" I had calculated. Cass told me that Use of the A-body front hanger required a 5/8" hole, but that was easy to accommodate. The other downside was that the A-body front hanger could not directly provide the stock E-body height; there were two holes for the spring bolt, and one would lower the car by 1/4" and the other would raise it by about 1" (if I remember what he told me correctly). I decided this was close enough to try!
The assemble was straight forward, and I decided to use the upper mounting hole for the eye of the spring. The axle perches easily set down on the locating pins. I could now see that the leaf spring was almost parallel to the centerline of the car. Measurements from the brake drum mounting surface confirmed that all was going to plan. I ordered up a set 5" BS custom offset 15 X 8 Torq Thrust IIs, which took about 4 weeks to come in. I then got the MT ET Street Radials moved from the previous rims to the new ones, and put them on the car. I was much more pleased with the appearance, and just recently put the car back down on the ground on 4 tires. The tires are now nicely located in the wheelwells, and the size is somewhat concealed.
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Re: 275/60/15 on a Cuda (long)
[Re: davenc]
#889002
12/26/10 11:09 PM
12/26/10 11:09 PM
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Joined: Nov 2007
Posts: 21,822 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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I run 275/60/15's on a 70 Cuda with Torque Thrust wheels but I chose either 4.75 or 5" back space. Don't remember which. No contact. I am thinking you must a good 1" tween tire and leaf-spring? I have about 3/4"
Edit after reading your post above. Yes the close spring contact area is the rear segments, I thought about intalling the rear offset hangers to gain clearance, but didn't have to for 275/60/15s. In fact, I think it may be possible to fit 295/50/15's with the offset hangers.
So now you are sitting on a set of barely used 4.5" BS TT's?
Last edited by Pacnorthcuda; 12/26/10 11:19 PM.
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Re: 275/60/15 on a Cuda (long)
[Re: davenc]
#889003
12/26/10 11:09 PM
12/26/10 11:09 PM
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Joined: May 2005
Posts: 598 NC, USA
davenc
OP
mopar
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OP
mopar
Joined: May 2005
Posts: 598
NC, USA
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DrDiff reminded me to check the pinion angle after changing the height, and to my surprise it looks like I will be fine with use of a simple shim. I assembled everything with a 4 degree shim in place, because I was concerned that the upper mounting position would rotate the pinion too far up. However, I hadn't considered that in lowering the rear of the car, that was improving the down angle of the transmission output. Currently the car has the trans output at 4 degree down, and the pinion is 2 degree down, and I am considering changing the shim to a 2 degree shim but I think I will try it as is for now.
In conclusion, this approach allows a 5"Bs wheel to be easily used on an E-body without use of any cutting or welding. The only consequence is that the ride height will need to change some.
Two other interesting tidbit is the weight of the rims. The original AR TT-II rim in 15 X 8 with 4.5" BS weighed 16lbs. The custom 15 X 8 5" BS rim weighed close to 18lbs. This was more than I expected, but I certainly want a nice strong weld between the two halves. In addition, I didn't know up front that AR was not going to dress the weld in any way. At first, I was sort of upset by this, but with the wheels on the car, I can't really see the weld from the outside.
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Re: 275/60/15 on a Cuda (long)
[Re: davenc]
#889008
12/26/10 11:33 PM
12/26/10 11:33 PM
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Joined: Nov 2007
Posts: 21,822 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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Quote:
Also, I don't think you can use the offset rear hangers with no change in the front hanger, without relocating the spring perch. That was something I was avoiding doing.
Yea I think your right on the front segments. But I was able to get the needed clearance so thankfully didn't have to go down that road. I would really like to try some 295/50's with the offsets, but at that point the 8"wheel starts to be a little on the 'too narrow' side.
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Re: 275/60/15 on a Cuda (long)
[Re: jvcuda]
#889011
12/27/10 12:08 PM
12/27/10 12:08 PM
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Joined: Jan 2003
Posts: 1,756 London, England
Gavin
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,756
London, England
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Nice post and good thinking, it's always good to see someone thinking of a new and simpler way to try and achieve something. I've read a LOT of posts on this issue over the years (E-Body tire clearance) and don't ever recall someone pivoting the leaf spring in the way you mention. IIRC, most people have found they can accommodate 275 or some even 295 without alteration, but it is certainly true that it depends on a number of factors that might differ from car to car. I'll put this on my list of options to consider when I actually come to spec and buy my wheels/tires - top of the list so far had been a Dr Diff relocation kit (rewelding perches) with stock axle. Nice one and thanks for posting
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