spring relo: offset vs. mini tub for handling?

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ValiantOne

ValiantOne

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Hey All,

I'm trying to plan my next move for rear suspension/wheels and tires. The car is 68 Val, 8.75, LBP. The goal is a corner carver, handling type occasional autoX or road track day car.

Which would be better for handling? A 1/2 spring relocation or full on mini tub with springs moved inboard to frame rails etc.

The reason I ask is right now I am going to new wheels (steelies) and tires on the car. If the 1/2 spring relo would be the best option, I may just do it now and get the correct offset wheels etc.

If the full on mini tub would be better, I'll just use the steelies I have now, put the widest tire I can fit on them and drive it until I am ready to do the full on spring relo.

Thanks for thoughts!

CE
 
Slight spring offset, then the widest wheel/ tire combo you can fit. Quality modern profile rubber (not radial T/As) Then some new springs and shocks.
 
tubs - mini or otherwise are really more about drag racing - you'll be fine with the offset kit and proceed as stated above
 
That is really helpful. I just figured if I had to move rear end perches for the offset............etc.

But if the mini tub is about going straigtline racing that makes life a bit easier for me!

Thanks,
 
No I don't. My car is still in build process, but I am going with Hotchkis springs, shocks, & sway bars. Adjustable strut rods & upper arms. Chassis stiffening from USCarTool. I will probably run Radial T/A's on 15's for street cruising & shows, but I plan to have a set of 17s for track & corner carving. I hear good things about Continentals.
Look for threads or comments on here by autoXcuda or 72bluNblu
Check this
Traction Test - The Best 200-Treadwear Tires - Hot Rod Magazine
the video to the article above:
 
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I think for tires you can look for something in a 200 or 300 tread wear depending on how much mileage you want out of it on the street.

Personally I had some Dunlop Direzza Z1 "star spec" on another car that I really liked and I have read that the Z2 is even better (Z1 star spec is old now). Those tires performed at the level of tires 2 or 3 times the cost at the time.

Currently I am running some Dunlop Direzza DZ102 on my daily which are pretty sticky and after some pretty heavy driving over the past year+ on the street (and mountain roads) aren't showing too much signs of wear. Good for the street in other words, not wearing out too fast but not ultimate grip.

For my scamp I am trying out some BF goodrich G-force sport comp 2 (not the all season ones) that seem pretty grippy the little I have driven on them. The cost was pretty low compared to other stuff in the range. Cant wait to get them out on the auto x to see how they do. I also thought it was kind of cool to pay homage to the radial TA with a newer option "american" tire.

G-force Sport Comp 2 looking mean under there (offset shackles too):

 
Alright, I'll weigh in. :D

I had a response all typed up but then I saw you're planning on running steelies, which I assume means you're going to run 15's. Which pretty much means there's absolutely no reason to do a mini-tub unless you're planning on 500+ hp. Because here's the thing, you're only going to be able to run a 245 up front. With a 15" rim you can only plan on 4.75" of backspace at the most, and that's not enough to get a 245 on a 15x8 inside the fenders. So, you're stuck with a 15x7 and 4.5" to 4.75" of backspace. Honestly you'll need the 4.75", because the only tire in a 245 and a 15 that's DOT legal is a BFG TA 245/60/15, and that's 26.6" tall. Too tall to get near the fenders.

The weight balance on these cars is nose heavy, and under braking of course it gets worse. The front tires are actually the ones that need to be the widest (unless you're running a big horsepower car). But unless you go to a 17" you can't get past a 245, and even with a 17x8 up front the best you can do is a 255 because of the backspace limitations on a 17" rim and the outer tie rod clearance. You really need an 18" rim, which would let you go to a 275/35/18. Even then, with a 1/2" offset you can run a 275, so, no reason for a mini-tub unless you're rocking some serious horsepower you need to put to the ground.
 
Moving your springs in just reduces their effectiveness (leverage) in handling side loads (corners). Maybe 1/2" isn't an issue, but moving them into the frame rails seems counter-productive to me. Just a thought.
 
If you plan on doing the 1/2" offset, keep in mind you can easily do it without buying the "kit." Just redrill the front hanger holes to move the hanger inward against the frame. For the back, I believe you can just flip the rear hanger and drill just one hole each to move the rear hanger 1/2" inward. Then, you just need to move the spring perches over on the axle housing and you just bought yourself an extra 1/2" room to fit 275s (maybe more with larger wheels and shorter aspect ratio) with EASE.

0213131906_zps6be1946a.jpg


0213131906a_zps505694d4.jpg
 
72bluNblu said:
Alright, I'll weigh in. :D

I had a response all typed up but then I saw you're planning on running steelies, which I assume means you're going to run 15's. Which pretty much means there's absolutely no reason to do a mini-tub unless you're planning on 500+ hp. Because here's the thing, you're only going to be able to run a 245 up front. With a 15" rim you can only plan on 4.75" of backspace at the most, and that's not enough to get a 245 on a 15x8 inside the fenders. So, you're stuck with a 15x7 and 4.5" to 4.75" of backspace. Honestly you'll need the 4.75", because the only tire in a 245 and a 15 that's DOT legal is a BFG TA 245/60/15, and that's 26.6" tall. Too tall to get near the fenders.

The weight balance on these cars is nose heavy, and under braking of course it gets worse. The front tires are actually the ones that need to be the widest (unless you're running a big horsepower car). But unless you go to a 17" you can't get past a 245, and even with a 17x8 up front the best you can do is a 255 because of the backspace limitations on a 17" rim and the outer tie rod clearance. You really need an 18" rim, which would let you go to a 275/35/18. Even then, with a 1/2" offset you can run a 275, so, no reason for a mini-tub unless you're rocking some serious horsepower you need to put to the ground.
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So if I am reading this right, are you saying I could go 275 in all 4 corners, if i used 18 in rims (and 1/2 in offset of rear springs)

If so I'd be inclined to go that route. It would be really nice to have all 4 wheels the same size ,etc.
 
DionR said:
Moving your springs in just reduces their effectiveness (leverage) in handling side loads (corners). Maybe 1/2" isn't an issue, but moving them into the frame rails seems counter-productive to me. Just a thought.
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THIS^^ The leaf springs control car roll in the rear, so ANY amount you move them inwards reduces the leverage they have. It MAY (probably) be that you could make this up with a rear anti-roll bar.
 
Do the 1/2 inch offset spring kit, I did the 3 inch relocation set up on a car and never liked the handling, it needed really stiff springs to work decent.
 
ValiantOne said:
So if I am reading this right, are you saying I could go 275 in all 4 corners, if i used 18 in rims (and 1/2 in offset of rear springs)

If so I'd be inclined to go that route. It would be really nice to have all 4 wheels the same size ,etc.
Click to expand...

Yup, with 18x9's you could go 275/35/18 on all 4 corners with a 1/2" offset in the back.

The only problem with that is the offset needed isn't exactly the same in the front as it is in the back if you have an A-body 8 3/4. In the front you need a 25-30mm offset (6" to 6.25" backspace). In the back it's more like a 20mm offset that you need. An 8- 10mm spacer isn't a really big deal, but you will need longer wheel studs.

DionR said:
Moving your springs in just reduces their effectiveness (leverage) in handling side loads (corners). Maybe 1/2" isn't an issue, but moving them into the frame rails seems counter-productive to me. Just a thought.
Click to expand...

67Dart273 said:
THIS^^ The leaf springs control car roll in the rear, so ANY amount you move them inwards reduces the leverage they have. It MAY (probably) be that you could make this up with a rear anti-roll bar.
Click to expand...

67autocross said:
Do the 1/2 inch offset spring kit, I did the 3 inch relocation set up on a car and never liked the handling, it needed really stiff springs to work decent.
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Yup, all of this is true. The 3" spring relocation will require higher spring rates and a larger rear sway bar to compensate for the change in leverage on the springs. For 1/2" offset it's not really a big deal.
 
72bluNblu said:
Yup, with 18x9's you could go 275/35/18 on all 4 corners with a 1/2" offset in the back.

The only problem with that is the offset needed isn't exactly the same in the front as it is in the back if you have an A-body 8 3/4. In the front you need a 25-30mm offset (6" to 6.25" backspace). In the back it's more like a 20mm offset that you need. An 8- 10mm spacer isn't a really big deal, but you will need longer wheel studs.







Yup, all of this is true. The 3" spring relocation will require higher spring rates and a larger rear sway bar to compensate for the change in leverage on the springs. For 1/2" offset it's not really a big deal.
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Hrmm, so no rotating of wheels/tires. Oh well

I'm confused about the 8-10mm spacer.where does that go and what is it for?

Thanks in advance, this is really helping!
 
ValiantOne said:
Hrmm, so no rotating of wheels/tires. Oh well

I'm confused about the 8-10mm spacer.where does that go and what is it for?

Thanks in advance, this is really helping!
Click to expand...

You can rotate wheels, you just need a spacer on the rear wheels. If you bought a set of 18x9's with a 30mm offset, you could use them all the way around with an 8 to 10mm spacer in the back (because then the effective offset would be 22-20mm). That would take longer wheel studs. Or, if you found a set of 18x9's with a 25mm offset, you could probably get by with a 3 to 5mm spacer in the back, which likely would be fine without longer wheel studs.
 
Ah! Love it. That is genius. That makes my decision. Thank you 72blunblu.

Since I JUSTgot this thing drivable for the first time since last October (and still have much to shake down) I'm going to take the two 225/60/15s I have on cop rims and see if they will work up front. If so I'll get two more and put them on cop rims and stick them on the car to finish out the season.

In the meantime I will save my pennies for a spring offset, new springs (wanna ditch the super stocks) rear swaybar and new wheel tire combo (most likely in 18") for next year.

Now to start designing that combo.......... got to do some measuring and make a list of 1000 questions.... :D
 
Perhaps another option might be to figure out what offset works on the front, buy 4 wheels that match and then build a rearend to work with that? If you didn't want to worry about spacers.

More for someone that might be thinking about a different rear axle anyway, rather than a guy that is happy with what he has and just wants new wheels and tires.

72bluNblu's method sounds very workable, just an idea.
 
ValiantOne said:
Ah! Love it. That is genius. That makes my decision. Thank you 72blunblu.

Since I JUSTgot this thing drivable for the first time since last October (and still have much to shake down) I'm going to take the two 225/60/15s I have on cop rims and see if they will work up front. If so I'll get two more and put them on cop rims and stick them on the car to finish out the season.

In the meantime I will save my pennies for a spring offset, new springs (wanna ditch the super stocks) rear swaybar and new wheel tire combo (most likely in 18") for next year.

Now to start designing that combo.......... got to do some measuring and make a list of 1000 questions.... :D
Click to expand...

You shouldn't have any real problems with the 225/60/15's on cop rims. Those are 15x7 and have a 4.25" backspace. I ran exactly that combo on my '74 Duster when it was still wearing the Duster fenders up front. I had to max out the adjustment on my fender to bumper braces, and I cut the 90* corner on the lower front corner of the wheel opening back at a 45* angle to have clearance when turning, but I was running pretty low even then.

DionR said:
Perhaps another option might be to figure out what offset works on the front, buy 4 wheels that match and then build a rearend to work with that? If you didn't want to worry about spacers.

More for someone that might be thinking about a different rear axle anyway, rather than a guy that is happy with what he has and just wants new wheels and tires.

72bluNblu's method sounds very workable, just an idea.
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If you were setting up a custom rear end it would be the thing to do, but obviously there's a lot of money involved there with custom axles and everything. All just to end up with a rear axle that's probably only about 20mm wider. 10mm is about the max width for a spacer I like to run, but if you get hubcentric spacers and use high quality wheel studs it's really not an issue. If you were doing an 8.8 conversion, or ordering a custom axle then it would make sense to set everything up for say a 30mm offset, because that would even give you the small amount of extra room you might need to run aftermarket disks up front later if you wanted. I run Dr. Diff's 13" cobra style kit up front, it adds about 5mm to the track width on each side. And it's a fairly popular offset for 18x9's, so you could use off the shelf rims more than likely.
 
72bluNblu said:
If you were setting up a custom rear end it would be the thing to do, but obviously there's a lot of money involved there with custom axles and everything. All just to end up with a rear axle that's probably only about 20mm wider.
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Too funny. I now realize that the same guy (me) that is too cheap to buy an aftermarket rear axle, is the same guy suggesting that the OP buy one. :realcrazy:

I spent a bunch of my time trying to figure out what OEM wheel would work with an OEM axle, so I didn't have to buy aftermarket stuff at all. But I wasn't worried about being able to rotate the wheels, either. And I was working on 17" stuff, too.

72bluNblu said:
10mm is about the max width for a spacer I like to run
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Ironically, a slip on disk brake rotor is about 6.5mm thick or better, and nobody has a problem with those. Call it a 6.5mm thick spacer and the red flags go up, though. :D

The OP said he has a BBP 8.75, which I am assuming is an A-Body 8.75. I had a buddy with one of those in his Duster, and when we measure the width, it was about 58" or so. If I remember correctly, the standard SBP A-Body 8.75 is 57.125" wide, so his BBP axle should be about 11mm wider per side which means he might not need spacers at all. And if he did, maybe a rear disk conversion would do the job and he wouldn't have to tell people he runs wheel spacers. :)
 
Picture of a 225 60 15 on a cop rim on a 68 Valiant:

IMG_00000799.jpg
 
DionR said:
Ironically, a slip on disk brake rotor is about 6.5mm thick or better, and nobody has a problem with those. Call it a 6.5mm thick spacer and the red flags go up, though. :D

The OP said he has a BBP 8.75, which I am assuming is an A-Body 8.75. I had a buddy with one of those in his Duster, and when we measure the width, it was about 58" or so. If I remember correctly, the standard SBP A-Body 8.75 is 57.125" wide, so his BBP axle should be about 11mm wider per side which means he might not need spacers at all. And if he did, maybe a rear disk conversion would do the job and he wouldn't have to tell people he runs wheel spacers. :)
Click to expand...

Yup, exactly. Using the measurements from B and E body axles to calculate the width of the BBP brakes and adding that to the flange to flange measurements for an A-body 8 3/4 I end up with 57 13/16" for an A-body 8 3/4 with BBP axles and brakes. So, yeah, almost 58". :D

Yeah I don't know what the deal is with all of the wheel spacer aversion. I mean, I try not to run them if I can, but buying rims off the shelf and maxing out your tire width pretty much mean you might need a spacer. Which is exactly how a disk rotor or even a brake drum functions. Small spacers are easy. Too much past 5 or 6mm and you need longer studs and should have hubcentric spacers, but if you do those things they're fine. And yes, with a rear disk conversion adding a 1/4" per side or so no spacers would likely be necessary.
 
Yes it is an a body 8.75. right now it has Yukon axles with green bearings, but those will come out and some of dr, diff's axles will go back in with taper roller bearings. I may go to discs in the rear too. Currently 11X2.5 drums.

This is why I'm really going to have to get a game plan and aave my $'s. So far I've put all my time and money in the frame and suspension, and I still need an engine too. I propped up the poor ol' 273 with timing chain, oil punp and some bearings b/c I don't know how long it will take to get the rest done.
 
Here's my '74 with 225/60/15's and cop rims.

IMG_3619.jpg


Yes, I had to adjust the fenders. I went back and looked at some of my posts back when I had the 225/60/15's on there, I didn't need to cut the back edge of the fender lip at the front corner for them. All I did was use the brace that runs from the lower front corner of the front fender that goes to the bumper bracket to push the corner out as far as the brace would go. I didn't modify the brace, just maxed out the adjustment.

I did the trimming when I added the 275's up front.
 
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