Jig for testing straightness of struts?

Tom '74 911 · 11-27-2013, 08:55 AM

Hi -

I was wondering if anyone has built a jig for testing struts for straightness? I found this older thread that has photos of a factory tool which is pretty cool looking (see attached), but likely NLA and/or crazy expensive...

Strut bent?

I could probably fabricate something similar to the factory jig, but I don't know what any of the angles need to be etc... Anyone done this or know what the angles should be for a straight strut?

Thanks,
Tom

DRONE · 11-27-2013, 09:12 AM

Looks like you could just enlarge the picture and get the angle right off of it. With the axel flange level (set the Electronic Digital Protractor at 0)you should be able to run an Electronic Digital Protractor up the strut and see if the readings remain the same thru it's entire length to see if there is any bend. I think this would be an easier solution than building a jig. ( just a thought)

Trackrash · Trackrash's Garage

Are you having alignment issues? Bent struts do happen. It's difficult to accurately measure the spindle included angle.

Do you have the struts off the car?

Some body repair shops have a jig, like and alignment jig, that can be used to straighten struts on the car.

I have successfully straightened a bent strut using a very large, securely anchored vice, to clamp the spindle. I clamped the brake mounts in the vice and used a very long stiff bar in the strut tube to bend it back straight.

Once you are SURE they are straight you may want to consider welding in reinforcing gussets to prevent further bending.

Flat6pac · 11-27-2013, 12:13 PM

I was always told if there is cracks in the paint around the spindle its probably bent

Tom '74 911 · 11-27-2013, 12:49 PM

Quote:

Originally Posted by DRONE

Looks like you could just enlarge the picture and get the angle right off of it.

Yeah, I'm looking for a little more accuracy than eyeballing the proper angle of the spindle off the image above...

Quote:

Originally Posted by Trackrash

Are you having alignment issues? Bent struts do happen. It's difficult to accurately measure the spindle included angle.

Do you have the struts off the car?

I guess to be more clear, I am wondering about the spindle and steering arm angles being off. The strut tube itself looks OK and the dampener action seems unaffected. There doesn't appear to be cracked paint or any evidence that anything might have moved, but I hit something pretty hard and bent the a-arm significantly and the turbo tie rod (and the car). The struts are currently off the car so they are easy to inspect. I'd love to be able to verify if it's straight or not before putting it all back together.

Quote:

Originally Posted by Flat6pac

I was always told if there is cracks in the paint around the spindle its probably bent

I can't see much in the way of cracked paint, but as I mentioned, it was a hard hit and I'd like to verify that the spindle and steering arm are still aligned correctly if possible.

Thanks,
Tom

Trackrash · Trackrash's Garage

In your situation I would definitely want to verify the struts as being straight. Being off the car it should simplify things. My experience is the tube above the spindle can be slightly bent, but it will not be obvious by casual inspection.

The best I could do was use a machinist's protractor to measure the angle. I'm sure there must be a better way.

Hopefully someone with more experience than me will chime in.

Tom '74 911 · 12-08-2013, 04:45 PM

Found some photos of more cool suspension parts jigs. Anyone have these or have access to them?

Thanks,
Tom

RWebb · RWebb's Garage

besides a bulge (as pictured on the other thread) or cracked paint...

if the strut insert can be removed and reinserted with no problem, can that be used as a test for straightness or integrity of the strut (the strut housing)?

Tom '74 911 · 12-08-2013, 04:56 PM

Quote:

Originally Posted by RWebb

besides a bulge (as pictured on the other thread) or cracked paint...

if the strut insert can be removed and reinserted with no problem, can that be used as a test for straightness or integrity of the strut (the strut housing)?

I'm not as concerned with the straightness of the strut tube as I am with the alignment of the spindle on the tube...

johnsjmc · 05:39 PM

Quote:

Originally Posted by RWebb

besides a bulge (as pictured on the other thread) or cracked paint...

if the strut insert can be removed and reinserted with no problem, can that be used as a test for straightness or integrity of the strut (the strut housing)?

No. The ball joint allows movement at the bottom which allows a bent strut to still attach at the A arm , even when bent badly. The spindle angle is something like 11 to 14 deg. (by memory.) The weaker tube bends causing the spindle angle to change. I believe it,s not actually the spindle itself which is bent but the result is the same.
I,m not an expert as I,ve only seen this a few times .
The usual symptom of a bent strut is an alignment issue where you can,t get close to the same camber setting on one side compared to the other. (with the car known to be level side to side.
It could be the body bent or sagged or the strut (weaker part) is bent. Most likely from a collision and likely on only one side.
Usually if it,s bad enough to replace you can see the bend ,bulge or dent with a careful visual examination. A straight edge along the tube might help identify a problem also. They always bend above the steering arm because the lower part is reinforced and shorter below the spindle. I,ve never tried to straighten one, only replaced them with a good used one.
The shock shaft could also be bent inside the tube and would only affect a camber change
at droop vs at normal height.
When you see the camber side to side problem you need to check everything until the damaged parts are found and the difference explained.
Chuck Moreland Elephant Racing must have a jig made so he can raise and weld spindles. He would probably charge nominally to check one for straightness.

johnsjmc · 05:45 PM

It must cost a million dollars for all the special tools and jigs Porsche has. No other car has as many special tools as Porsche (perhaps Ferrari but I,ve never worked on one.
Many of the special tools can be substituted with some good pullers etc.
Gone are the days you could rebuild and align a car with vicegrips, a level, and a piece of string. (well almost)

Steve@Rennsport · 12-08-2013, 05:59 PM

I've not seen the factory tools in a very long time, back at the dealership (mid-70's).

We use the milling machine table, protractors, and other measuring tools to see if a spindle, steering arm, or strut tube is bent and compare the values with a brand new strut.

Jon B · 12-08-2013, 07:29 PM

Quote:

Originally Posted by Tom '74 911

Found some photos of more cool suspension parts jigs. Anyone have these or have access to them?

Tom, the photo at the top of the page is mine, from a previous thread.
I have most of the old factory tools from 1950's through 1980's.

Jon B · 12-08-2013, 08:24 PM

Quote:

Originally Posted by Tom '74 911

I was wondering if anyone has built a jig for testing struts for straightness?
I found this older thread that has photos of a factory tool...

Original tool in question:
P286b
Strut jig, 911/912/914-6 from 1969-on.

Jon B · 12-10-2013, 11:18 PM

Quote:

Originally Posted by Tom '74 911

Found some photos of more cool suspension parts jigs. Anyone have these or have access to them?

Here's another suspension jig, not yet pictured:

P288
Transverse control arm jig, 911/912 from 1965-68.
These tools and fixtures were very well made, considering their limited use.

Tom '74 911 · 12-11-2013, 11:55 AM

Hi Jon,

Thanks for posting! I think these original factory tools/jigs are so neat. It's nice to know that they are still out there and being used very now & then. Short of finding some for sale somewhere (which seems pretty unlikely!) I will go Steve W.'s and try to compare know good parts w/suspect parts using more medieval methods and materials - straight edges, protractors, rulers etc....

Thanks,
Tom

gearya · 12-11-2013, 06:37 PM

If my front end aligns ok, does that mean I don't have to worry about a bent strut?

Trackrash · Trackrash's Garage

That depends. What exactly do you mean by "OK"?

A friend of mine just had his '71 aligned. The mechanic was able to get about 1 deg negative camber on both front wheels. When you looked in the trunk at the tops of the struts, both were all the way to the left in their towers. (when looking from the front). One of his struts was slightly bent. His alignment was OK, but not ideal.

Tom '74 911 · 12-13-2013, 03:30 PM

Quote:

Originally Posted by gearya

If my front end aligns ok, does that mean I don't have to worry about a bent strut?

If the alignment numbers are w/in spec. and the settings are symmetrical from side-to-side, then most likely, everything is as it should be...

Jon B · 12-13-2013, 06:23 PM

Quote:

Originally Posted by Trackrash

When you looked in the trunk at the tops of the struts, both were all the way to the left in their towers. (when looking from the front). One of his struts was slightly bent. His alignment was OK, but not ideal.

If a strut is bent, you may be able to achieve desired alignment in a straight forward direction, but when the bent strut is turned on its altered axis, the spindle arc and placement will differ from that of a straight strut on its normal axis. In addition, a bent spindle can cause mis-alignment between the brake disc and caliper.