Smaller Tires or Shackle Flip?

[cpavelko]

Hello,
Just wanted to get some peoples opinion on this from experience on what would be better. I currently have 35x12.5x15" tires with a 4" block lift on the back of my Blazer. The tires are positioned too far to the front due to the lift. I'd like to do the classic shackle flip but would that buy me any clearance wit hthe tires I have? If I just go with smaller tires for now such as 31's or 32's, would that allow me to have more clearance? Should I look into cutting the rear wheel well to allow better clearance? Just looking to make the truck functional when taking it on some simple trails. I don't need a ton of clearance so downsizing the tires wouldn't hurt me there.

Here is a pic of my buddy acting like a dork in the Blazer but you can see the clearance issue.

[fxdxharley]

your best bet would be to loose the blocks and get new springs. off road design makes lift springs that will reposition the axle in the correct spot. there is several build here that use them. look threw the build section.

[1972_K5]

ORD makes a zero rate leaf that you could add which allows you to mount your axle centered, forward, or back. Would probably be the lest expensive fix and would correct the droop that you have in the back.
http://www.offroaddesign.com/catalog/Zero%20Rates.htm

[2003 silverado]

I have a 4IN on mine and I believe the rear blocks have the Pin /hole Off set for that problem???

[SeventyOne]

Dont cut it!

If it were me and I wasn't doing it on the cheap...

shackle flip, no lift block, and a 1" lift zero rate to move the axle back. If you want to spend even more...go with new rear springs too. Stock height.

Will be nice.

How are the tread on the tires? If you need new tires anyways you could go to 33"s and get even more clearance but that's up to you.

[cpavelko]

Back from the dead!

Finally got around to do the shackle flip (DIY4x). Measured the axle position as it sits on the springs and to center it in the wheel well it seems like it would need to shift back 3.25 inches. This should allow the clearance I need for the 35" tires (which have plenty of tread left).

I was going to fabricate some plates to offset the axle back but had concerns of offsetting the spring back that far and also probably need to look into the drive shaft slip yoke, it seems to be maxed out so may need a different drive shaft.

- Would shifting the axle back 3.25" on the stock springs with the shackle flip be ok?
- Any suggestion on a driveshaft to grab? Maybe a 4x4 short bed driveshaft?

If this doesn't work out, I may have to go with new springs or smaller tires to clear the wheel wells. I don't want this to be too much of a money pit.

[cpavelko]

Saw this posted from this thread: http://67-72chevytrucks.com/vboard/s...d.php?t=378271


The 56" springs will bolt up with no modifications. I will tell you that the pin is not in the exact center of the spring, it's offset. But in my case that was a good thing. When i did the shackle flip on my 1970 with the stock 52" springs, my axle got pushed forward about 2 inches, and i had to use the ORD 1" add-a-leaf blocks to move the axle back so it was centered in the wheel well. Might not be as bad on longbeds, but on my shortbed it was very apparent and i would definitely plan on getting the ORD add-a-leaf kit if you go with stock length springs. I switched to 56" springs and it alleviated the problem completely. Plus, with the stock length springs the shackle angle is terrible, the shackle will be straight up and down and it will take more energy to move it, and you'll have a rougher ride. If i were you i would order the shackle flip, and tuff country ez-ride 2" springs for a 73-87 truck. Call tuff country to verify the length of their springs. Hope that helps.

I'm assuming I could pull a set of 56" springs from a 73-87 chevy and it should help with the wheel center issue and give a softer ride at the same time?

[Chulisohombre]

If your springs are still ok in the rear a shackle flip will move them back a lil bit. That and a zero rate in the reverse position will put it centered or a lil rearward again. Then you may need a shim or shift the spring perches to get the pinion pointed correct again if there is vibration. You might be ok on your stock driveshaft but won't know til you do the flip.

[AJs72K5]

Originally Posted by Chulisohombre

If your springs are still ok in the rear a shackle flip will move them back a lil bit. That and a zero rate in the reverse position will put it centered or a lil rearward again. Then you may need a shim or shift the spring perches to get the pinion pointed correct again if there is vibration. You might be ok on your stock driveshaft but won't know til you do the flip.

Actually....a shackle flip rotates the rear axle forward in an arc with the front spring mount acting as the pivot. I put new perches in to move it back 1.5" after installing the flip. Same can be accomplished with a set of Zero rates.

[Chulisohombre]

Originally Posted by AJs72K5

Actually....a shackle flip rotates the rear axle forward in an arc with the front spring mount acting as the pivot. I put new perches in to move it back 1.5" after installing the flip. Same can be accomplished with a set of Zero rates.

Wouldn't that depend on where you bolted the flip on and length of springs and schackle length as well. I've seen it done so many ways I guess so stock might be different. I also haven't seen it done on too many first gens.

[AJs72K5]

Originally Posted by Chulisohombre

Wouldn't that depend on where you bolted the flip on and length of springs and schackle length as well. I've seen it done so many ways I guess so stock might be different. I also haven't seen it done on too many first gens.

Yes, assuming you stay with a 52" rear, 4.5" shackle, and bolt the flip to the factory rear hanger as they're intended, it'll move the axle forward. Assuming we're talking the ORD or DIY4X flip here, this isn't first gen specific. Changing the rear shackle from tension to compression, you put the rear spring eye roughly 8" lower than it originally was. Since the front eye position is fixed, and the spring length is constant, the rear eye moves in an arc downwards, bringing the forward axle with it.

[Chulisohombre]

I see what you are saying. I guess I thought since the shackle switches sides it pulls the spring back farther since a lot I've seen use a longer shackle. Thanks for clearing that up. I'm guessing using a 63 inch spring and moving back the hanger it would offset some. I think I read that the longer chevy spring has a offset to help center the spring.

[AJs72K5]

Originally Posted by Chulisohombre

I see what you are saying. I guess I thought since the shackle switches sides it pulls the spring back farther since a lot I've seen use a longer shackle. Thanks for clearing that up. I'm guessing using a 63 inch spring and moving back the hanger it would offset some. I think I read that the longer chevy spring has a offset to help center the spring.

The 6" shackle would make the axle location even worse as you'd push the rear eye further down the arc. I think a 56" spring would be better in this case. That way you'd only have to move the flip back to keep the shackle angle decent.

A 63" spring would necessitate moving the front hanger too. If you're gonna move both hangers, well, you put the axle anywhere you want it. But, at the end of the day, I don't think the original poster was looking to do that much fab work.

But you're correct, pinion angle definitely changes with a flip. He'll need to be prepared to shim it, or weld new perches in to address it.

[Chulisohombre]

Yeah I guess I had it a little wrong. I thought that the longer shackle Would help the spring flatten it too but I guess only To A small extent. Ive never done it personally just was going off of what I thought it did on other trucks. My lift springs were offset to relocate the axle so I guess I was just going Off that. So A flip with like a two inch lift Spring would probably move the axle a lil bit but would need a zero rate to move axle and shim or reweld axle perches to get it to a usable amount of pinion angle. I've heard of red ruling springs too to get the axle Back farther as well. It still Seems like a lot More work for just a four inch lift. My lift springs only cost 400 bucks with shipping in the rear from pro comp. they hold weight for towing and flex pretty
Well.

[cpavelko]

Hey guys. Just getting back to this thread from a long weekend. I measured that the axle needed to mvoe back 3.25" in order to be centered in the wheel well. With a 35" tire and 36" wheel well opening, centering the tire will need to be more precise.

1) I ended up visiting the Junkyard on Satuday and pulled a set of 56" springs from a '90 4x4 2500 Suburban (6 leafs plus a helper leaf). I plan on flipping these so the longer (30") side of the spring is foward which will give the axle enough offset back to center my 35" tires in the wheel well. May actually need to move the axle forward a 3/4" once I do this.

2) The DIY4x shackle flip, I can swap sides so the shackle mount point moves back an inch or so, which will accomodate the bigger springs.

3) I will need to address the pinion angle and axle legnth once everything is bolted up.

4) I also needed to buy a longer flex brake line which I will replace this week.

[Chulisohombre]

Ord or skyjacker can get you stainless beaded brake lines for a hundred bucks. Sounds like your spring idea will work but may still need a zero rate to get it perfect. I don't know if it will work but could ask to have it milled to be a shim as well. That's what I did.

[cpavelko]

I've always used Inline Tube for all my stainless lines. This one cost me $35 I believe with all the fittings. It should be here any day now.

[Chulisohombre]

Yeah they're good too. I wasn't sure if you needed a complete set for the front as well.

[AJs72K5]

Originally Posted by cpavelko

Hey guys. Just getting back to this thread from a long weekend. I measured that the axle needed to mvoe back 3.25" in order to be centered in the wheel well. With a 35" tire and 36" wheel well opening, centering the tire will need to be more precise.

1) I ended up visiting the Junkyard on Satuday and pulled a set of 56" springs from a '90 4x4 2500 Suburban (6 leafs plus a helper leaf). I plan on flipping these so the longer (30") side of the spring is foward which will give the axle enough offset back to center my 35" tires in the wheel well. May actually need to move the axle forward a 3/4" once I do this.

2) The DIY4x shackle flip, I can swap sides so the shackle mount point moves back an inch or so, which will accomodate the bigger springs.

3) I will need to address the pinion angle and axle legnth once everything is bolted up.

4) I also needed to buy a longer flex brake line which I will replace this week.

Be prepared to cut a notch in the DIY4X flip to clear the gas tank strap. Pretty sure Kert isn't sending these out notched. Check the first page or two of the build thread link in my signature to see what I mean.