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CV Joints

Posted by DexterVW 
Josh Wimpey
Josh Wimpey
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Re: CV Joints
July 07, 2015 10:34AM
Take some pics so we can see.

Car at static ride height
Suspension at full-droop
Struts
etc

What is the overall uncompressed length of your struts from upper knuckle bolt to top of upper spring perch?

Something fishy going on here as I am with Wildert 90% of failures come from not controlling the position of the motor/trans adequately



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john vanlandingham
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Re: CV Joints
July 07, 2015 01:02PM
Quote
DexterVW
Thanks guys... my engine is nicely tied down and the fault lies on the suspension alone. At full droop I do not have enough plunge in the CV's and can actually kill a set before even taking them off the lift sad smiley

Very suspicious conclusion...

Many many guys have more overall travel, and presumably more droop..

I highly suspect the things are simply too long in LOA length Over All. Or something.
I suspect further that to get the car to sit somewhat correct you've sunk the thing down to so point (at which position it has very little compression travel) so it "looks like" it has a whole bunch too much droop...

But who really knows..
This is one of those things which cannot be solved by talking about and might be solvable with tape measures, or rulers..and photos...

So at this point, despite lots of talk/typing...who knows what's up?

I thought getting suspension lengths and the "up/down" balance was the critical thing but I've been wrong often before---I know now that having knobs to twist to "tune" the damping is more important than travel, valving, match spring rates etc..

Have you tried Left Foot Braking?
That is officially the solution to everything.



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DexterVW
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Re: CV Joints
July 07, 2015 01:21PM
I will measure that all up for you tonight gentlemen.

for now.. static ride height picture.



(btw I have measured this all before and come to the conclusion I need the long plunge CV's but I'll entertain you all with real numbers on the screen)



Edited 1 time(s). Last edit at 07/07/2015 01:22PM by DexterVW.
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Josh Wimpey
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Re: CV Joints
July 07, 2015 02:36PM
What size tires are those? It looks pretty/really tall up front to me.





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danster
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Re: CV Joints
July 07, 2015 02:42PM
Did you try changing back to the proper mk3 GTI / VR 5 stud shafts which are approx 5 - 8mm shorter than the 4 stud TDI shafts?

You say you need more plunge, yet you chose to fit shafts that were longer than the ones designed for the 5 stud application...

The thread needs some appropriate music.







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DexterVW
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Re: CV Joints
July 07, 2015 02:50PM
Yup, i've tried both combo's and even a mk4 shaft on the drivers side for a giggle

I think the fact the suspension droops another 1/4 inch after I unbolt the inner CV proves my point but you know I can continue to be told I need shorter shafts till the cows come home.

Dave
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danster
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Re: CV Joints
July 07, 2015 03:03PM
Are there witness marks on the output flange from where the inner CV may be contacting it?

As others have mentioned the car does look pretty "lifted" from the pics, and that may mean the shafts are outwith normal designed parametetrs of movement.
I would have thought the engine side shaft would be contacting the subframe if there was to much droop though.



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Josh Wimpey
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Re: CV Joints
July 07, 2015 03:18PM
Quote
DexterVW
Yup, i've tried both combo's and even a mk4 shaft on the drivers side for a giggle

I think the fact the suspension droops another 1/4 inch after I unbolt the inner CV proves my point but you know I can continue to be told I need shorter shafts till the cows come home.

Dave

OK, just so we are all speaking the same language here. The fact that your suspension droops more after unbolting the inner CV means you have run out of CV extension. Yes, I know this is the same as plunge but backward as the CV is symmetrical. Anyway, --at least at current height --- you need LONGER shafts to keep the CVs from pulling apart at full droop.

Is that all correct?

For me, this brings up more questions:
--What position is your ball joint in relation to the slotted holes in the control arm?
--What are you using for control arm bushings or bearings?
--What is the stroke of your front struts?
--What is the compression of said struts at static height?



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danster
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Re: CV Joints
July 07, 2015 05:00PM
You could determine whether it is drive shaft length, or excessive CV angular articulation that is causing the issue by the following simple test.

Check if you get full droop with full steering lock applied. (whilst checking left side, turn steering full left, and checking right side, turn steering full right)

Reason being is the 5 stud setup by design plunges the drive shaft inwards approx 8mm when full lock is applied due to the bottom ball joint being off the centreline of the strut.

If the drive shaft is too short and restricting full droop, then applying steering lock effectively lengthens the shaft and should release any restricted droop.
If the drive shaft is too long it will bind more when you try to apply steering lock.


And to add, there are also some really shit quality reconditioned CVs on the market so another thing in the mix.



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DexterVW
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Re: CV Joints
July 08, 2015 07:13AM
Quote
Josh Wimpey

Is that all correct?

For me, this brings up more questions:
--What position is your ball joint in relation to the slotted holes in the control arm?
--What are you using for control arm bushings or bearings?
--What is the stroke of your front struts?
--What is the compression of said struts at static height?

Yes that is correct.

-The ball joints are sucked all the way in.
-bushings are R32/TT
-7 inches
-3.5 inches compressed at static height (as seen in above photo)

I'm racing in the Okemo hillclimb this weekend and decided that I should try to lower it down to see if I can save these CV's.. low an behold they got a lot quieter. I dropped it an inch all around and have another 1/2 inch to go on the threads.

John... struts are 18.5 inches from the upper spring perch to upper knuckled mounting bolt at full droop.

what else did I measure.. oh yeah at full droop the short cv is at 20 degrees and the long axle touches the subframe.
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