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Serpent7 Samba Member
Joined: May 26, 2008 Posts: 410 Location: Temple Hills, MD.
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Posted: Fri Jun 30, 2017 7:20 pm Post subject: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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I have a '73 Thing and I have never Indexed/lowered an IRS Type 1 before. I want to lower it approx 4.75" and after some research found out this is the best (cheapest) way to do it. I'll be turning the inner spline 2 notches, but I have a few questions...
What should I expect for a first timer doing this?
What specialty tools do I need to complete the job?
How hard is this to do? (I've already done dropped spindles and I disk brake install on the front.)
How long should it take to do both sides?
Any advise before I get started?
Finally, would you recommend a first timer doing this by himself?
Thanks!
_________________ 2019 Audi Q5
2014 Volkswagen Touareg X
1997 Honda Shadow
1979 Kawasaki KZ1000
1979 Volkswagen Transporter
1973 Volkswagen Thing |
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GI Joe Samba Member
Joined: April 28, 2005 Posts: 2012 Location: Athens, TN
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Serpent7 Samba Member
Joined: May 26, 2008 Posts: 410 Location: Temple Hills, MD.
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Posted: Wed Jul 05, 2017 4:24 pm Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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Thanks, GI JOE! Anyone else wanna chime in? The more info. I have, the better... _________________ 2019 Audi Q5
2014 Volkswagen Touareg X
1997 Honda Shadow
1979 Kawasaki KZ1000
1979 Volkswagen Transporter
1973 Volkswagen Thing |
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oukno Samba Member
Joined: December 11, 2007 Posts: 138 Location: Cali
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Posted: Thu Jul 13, 2017 9:32 am Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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Just look at a few posts on here
This sh!t is rocket science if you can work on any part of one of these tinker toys you can work on other parts! _________________ 64 baja
64 ghia
74 Scout II
74 Tahiti Jet boat
02 Sierra 2500 HD
Love them all but I never enough time to play with them. |
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doublecanister Samba Member
Joined: September 23, 2008 Posts: 1184 Location: Richmond, Va
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Posted: Thu Jul 13, 2017 10:58 am Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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just throwing this out there,
I dropped my 73 Thing's ride height by about 3inches (no more than 4) by
just changing the tires.
I had 205x70 r15's and I believe I went to 185 x 60 R15's.
I used a tire formula I found online for figuring out wheel and tire total height to come up with the tire size I went with.
using the formula it's not that much of a change but ride height I noticed it at the front windshield when standing next too it, before on the 205x70's I couldn't see over the roof, then with the change it dropped the roof level
and it was about 3 inches.
It really didn't affect the speedo either, tested with GPS and it was right on.
Good thing I've not gone lower, with that rear sway bar on it now, the center section sits about 3inchs lower than the pan, sure helped the ride and handling though.
The reason for the tire change, my right foot kept catching when getting out of the THING and my dad couldn't get his leg up high enough to get in, but that tire change sure helped all that.
T
"the formula" I used:
Here's the formula for determining the diameter of a tire based on the
Standard size designations:
Diameter (in inches) = (2 * tire-width * aspect ratio / 25.4 ) + wheel rim size
The division by 25.4 is to convert mm to inches.
Using 205/60-15 as an example:
Tire width = 205 mm
Aspect Ratio = 60 (sidewall height is 60% of tire width)
or 0.6 * 205 = 123 mm
Wheel rim dia. = 15 inches
So the diameter of a 205/60-15 tire is = (2*205*0.6/25.4) + 15 = 24.69 inches _________________ ****************************************
2020 - Mustang Eco Boost [High Performance]
1973 - Thing
1966 - Mustang GT- Fastback
1951 - Ford F1 pickup Flathead V8 |
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911pickup Samba Member
Joined: March 06, 2004 Posts: 625 Location: Near Goats on the Roof
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Posted: Thu Jul 13, 2017 4:00 pm Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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How did you drop your ride height by 3 inches by going from a 205/70 to a 185/60?
The diameter of a 205/70 is 26.3"
The diameter of a 185/60 is 23.7"
The difference is 2.6" which needs to be divided by 2, since the diameter loss is a combination of top and bottom when the wheel/tire is mounted on the vehicle.
The ride height difference works out to 1.3"
Have I missed something here?
As for your speedo, I suspect that your mph was way out with the 205/70 and the 185/60 brought it back close to stock height.
The difference between a 205/70 and 185/60, at 60 mph, is 6 mph. |
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doublecanister Samba Member
Joined: September 23, 2008 Posts: 1184 Location: Richmond, Va
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Posted: Fri Jul 14, 2017 9:42 am Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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911pickup wrote: |
How did you drop your ride height by 3 inches by going from a 205/70 to a 185/60?
The diameter of a 205/70 is 26.3"
The diameter of a 185/60 is 23.7"
The difference is 2.6" which needs to be divided by 2, since the diameter loss is a combination of top and bottom when the wheel/tire is mounted on the vehicle.
The ride height difference works out to 1.3"
Have I missed something here?
As for your speedo, I suspect that your mph was way out with the 205/70 and the 185/60 brought it back close to stock height.
The difference between a 205/70 and 185/60, at 60 mph, is 6 mph. |
Hey 911pickup,
Answer is simple, magic!
Actually I had selected a few different tire sizes trying to guesstimate the best one to go with.
I got new 15inch rims (the old chrome ones were bent and had a bad wobble at 45+mph) and with the new tire size and it dropped it right about where I ballparked it would.
It was about the perfect amount too for entry and exit.
I will have to check my tire size for exacts, (they may be 195's) but that was a from memory tire size.
I had to get a different size for the spare to fit under the hood with the 15in rim, that could be the spare size.
I'll check it this weekend and let ya know.
But, I used that formula I posted and a ruler, I measured the way it 'was sitting" [on the old chrome rims and 205's] and subtracted the differences from the various sizes I calculated and that helped me pick a size to go with.
I'll look, I know I posted that stuff on the samba (I think I did) a few years ago, if I find the post i'll re-post or put the link in here.
T _________________ ****************************************
2020 - Mustang Eco Boost [High Performance]
1973 - Thing
1966 - Mustang GT- Fastback
1951 - Ford F1 pickup Flathead V8 |
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doublecanister Samba Member
Joined: September 23, 2008 Posts: 1184 Location: Richmond, Va
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Posted: Sat Jul 15, 2017 8:13 am Post subject: Re: Indexing the rear, inner spline 2 notches for a 4.75" drop? |
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hey 911
I may have made a calculation mistake when I figured this out, I don't remember. The drop I noticed was at the windshield height right after I did this.
and you're correct, it calculates to about a inch difference on the tire.
I did this just now:
195x65r15 Width in MM: 195mm (2*195*0.6/25.4) + 15 = 24.98 ~25inches
205x70xr15 Width in MM: 205mm---(2*205*0.7/25.4) + 15 = 26.3 inches
( I may have used 0.6 here instead of 0.7 for the aspect ratio when I first did this).
like you noticed: the difference is about 1.3 inches.
if you add 1/2 inch for vehicle weight compressing the tires a bit: I got 1.37 inches which is close to 1 & 1/2 inchs.
But my THING now sits at the windshield at about 59 3/4 inch from the floor.
at 63 inchs I cant see over the window.
SO best guess was a to 2 1/2 inch 3 inch drop in ride height.
Hey whatever it did, it fixed my 'foot drag' issue so I'm happy!
T _________________ ****************************************
2020 - Mustang Eco Boost [High Performance]
1973 - Thing
1966 - Mustang GT- Fastback
1951 - Ford F1 pickup Flathead V8 |
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