Lots of caster? A WARNING

[JKleiner]

I answered a question posed in another thread and in a follow up the OP asked why other people weren't having the same problem. I don't remember having seen it discussed previously so it made me think that maybe other people ARE having the same problem but are unaware...

If you are running a high level of positive caster, say 6 degrees plus, there is a very good possibility that you will not have enough thread engagement with the standard upper control arm forward links. When I built my car and did the first alignment two years ago I saw how much thread was out of the sleeve and knew that they needed to be replaced with longer ones. Here are some photos:

Here is one of my front links set for +8 caster and -1 camber


This shows how little thread engagement exists when you get into the higher caster range with the standard black 3 5/8" UCA sleeves


The link is still set for the same center to center length but with a 5 inch sleeve


I got the sleeves thru Speedway Motors.
http://www.speedwaymotors.com/Alumin...Inch,2087.html
For a 5" sleeve you want part # 910-34158-5

If you have anywhere close to as much thread out of the sleeve as the top photo please replace them with longer ones.

Be safe,
Jeff

[TXBLU]

Awesome info! I think I'll order up some of those just to be sure. Thanks for the post!!!

Eric

[Jetsbaby]

Would you still have the same problem if you were running the SAI Mod or have a MK4 using the "NEW" mounting holes?? I think you might be still OK???

[astglenn]

That is the best post I have seen in a long time.

Thank you Jeff.

[David Borden]

Great post.... A good rule of thumb is 1.5x width of bolt for thread engagement. Maybe 2x for alum threads.

David

[RJM]

thanks for the info X5.
Ray

[Useless]

Thanks good info XXXXXX

[SNAKY1]

Nice job Jeff,

Now that's the kind of info one can really use! Also, it's great that you included pictures along with the explanation. Very effective.

Really appreciate your thoughtfulness in relaying this information. Although currently I'm not running a lot of positive caster, I'll be saving this information for use in the future.

Thanks again,

Jerry T

[bbk347]

Very good post and pictures. Same info on the tie rod ends. Once you've got your toe set initially, mark (I use a magic marker) on the inner tie rod and remove the tie rod end to see how much threaded material is left. As David said, 1 1/2 times the width of the shaft is a good minimum. Also when trying to get lots of caster, some have taken the locknuts off in order to thread in the rear adjusting tubes more. Not a good idea. The shaft will wiggle inside the tube and eventually break. Be sure to loosen (and retighten) all the bolts and nuts on the adjustment tubes when doing your alignments. If you need a giant set of pliers to try to turn the tubes....something is still tight! The ends of the clevis, need to be able to pivot as you turn the tubes; both tubes, even if you are just moving one of them.

[03SC]

Funny, I have a set of those in my parts bin for just that reason. Haven't put them on since I'm not on the road but keeping them for just this reason.

[JKleiner]

Originally Posted by Jetsbaby

Would you still have the same problem if you were running the SAI Mod or have a MK4 using the "NEW" mounting holes??

Having not seen one I don't know, however when using these upper arms with any of the spindle options to gain positive caster the front link has to get longer while the rear gets shorter, so you need to be conscious of how much thread is engaged.

I did my initial alignment and became aware of the situation while still a go cart. Took the pics and intended to post them back then but got caught up in completing the car and kind of forgot about sharing the information until yesterday when "pittsman" brought it up in the other thread.

Jeff

[CraigS]

I had the same problem on my MkII but solved it differently since i also run about 2.5 deg camber for autocross.My frame has two sets of holes for mounting the UCA crossbar to the frame. I think they are there for standard vs pin drive setups.I drilled an extra hole in between the two rear holes and moved the rear bolt of the UCA to there. this got me more caster and camber at the same time.

[raceral]

You go Jeff....

[kelownacobra]

Excellent info, Jeff. The truest reason for this forum. I'm not running much castor, but if that ever changes I'll definitly change those sleeves. Thanks for the heads-up.

Jim.

[Bob Taylor]

Excellent !!

[astglenn]

Has anyone checked Mikie P's car for this issue? Bill?

[Darren]

Originally Posted by astglenn

Has anyone checked Mikie P's car for this issue? Bill?

His front suspension was in tact.

[AC Bill]

Jeff mentions on the other thread you linked to this thread.

"Mine is a Mk 3. The difference between your setup and mine is that I have Fox spindles. I suspect the geometry variation between them and the SN95 type you have accounts for me not encountering the caster limitation you are seeing."

Can this be confirmed, as to the Fox spindles setup not having this concern? I hate to order some part that I may not need..

[CobraDVM]

There are lots of different front suspension setups - fox vs sn95 spindles, and SAI vs no SAI - probably something you just have to wait and see how it sets up before deciding if you need to get longer sleeves. Anyone with 94/95 spindles and the SAI mod having this problem with lots of caster with power steering?

[Rob]

Great info and great write-up..

Just a question? Wouldnt STEEL be better than aluminum for a suspention part.

[FFRdreamer]

Originally Posted by Rob

Great info and great write-up..

Just a question? Wouldnt STEEL be better than aluminum for a suspention part.

As far as strength? Possibly. As far as unsprung weight? No.

[JKleiner]

AC Bill,
Either the Fox or SN 95 spindles can have this concern if the front link is extended far enough. It is simple physics; when you start getting agressive with caster the front link is adjusted to be longer and eventually thread engagement becomes a concern. What pittsman was asking about in the other post related to the fact that when he tried getting more than 6.5 degrees of caster he could no longer maintain -1 degree of camber. I am at 8 degrees + with Fox spindles and wondered if the limitation he encountered was due to differing geometry with the SN 95 type he is dealing with. That doesn't change the need to use a longer sleeve if the link is greatly extended.

Rob,
The factory installed black sleeves are aluminum (as are all parts of the UCA with the exception of nuts & bolts and the crossbar) so no qualms with using a longer sleeve of the same material.

Cheers,
Jeff

[Rob]

I was just making sure... I did not know the black ones were aruminum! :-)

Are the older ones, the ones made by Pole Position steel?

Very intresting post... with so many cars out there I wonder if people are driving and not knowing. That first picture with 3/4 inch or so threaded into the tube is SCARY!

Rgds

Rob

[pittsman]

Hey Jeff:
I took the upper control arm apart today and confirmed that at -1 degree camber and 6-1/2 degrees of positive caster the heims were only screwed in .330". Min for 5/8 threaded heim should be about .940". Shortest swage tube that I could find was 5 ". For anyone keeping an eye on this thread I am pretty sure I can still back the caster down to about 5 degrees before the threads are adjusted all the way in with a 5" tie rod adjuster. I will confirm and publish when I have the data. I can also get swage tubes in custom sizes 4 or 4-1/2 for the same price and a three week wait. They're about 11.00 bucks each, steel with 7/8 od and yellow zinc coated.

[GWL]

I don’t want to get in the way of the discussion here, as I think it is an important one. I haven’t really started to work on my Mk.4 yet but I took some pictures today for this thread.

All I have to go on now is what I’ve read here about the mounting of the upper ‘A’ arms. I don’t have the new ‘Build Manual’ yet.

Below are a few pictures I took for this post.

Picture of two sets of holes for mounting the upper ‘A’ arms-Looks like they are still going to drill the old holes as on the Mk.3 but the entire mounting looks different from the original Mk.3


Mk. 3 Mounting of ‘A’ arms-Holes are there so I guess that is where the Mk. 3 mounted.


Mk. 4 Mounting of ‘A’ arms-only going from what I’ve read here


See my next post as I compare them, George

[GWL]

Both ‘A’ arms sort of mounted together to show the difference-difference is about one inch vertically and didn’t measure horizontally because new mounting puts the mounting on an angle to the Mk.3, see next picture


Showing the difference in angle of mounting of the Mk.3 to the Mk.4


Maybe the original Mk.3 does not mount the same as is shown here. I don't know. But it looks like it does put the 'A' arms in a better position to avoid this problem.

George

[JKleiner]

pitts,
You could order the 5" ones and cut 1/4" or 1/2" off if necessary. I'll let you in on a secret---when I ordered mine Speedway only had one 5 incher in stock so I also bought a 6" and cut an inch off!

Jeff

[rponfick]

I had previously ordered the 4" item from Speedway to solve this problem. Price was $7.99. I hope the 4" is long enough to solve the problem.

Ralph.

[Jetsbaby]

Originally Posted by GWL

Both ‘A’ arms sort of mounted together to show the difference-difference is about one inch vertically and didn’t measure horizontally because new mounting puts the mounting on an angle to the Mk.3, see next picture


Showing the difference in angle of mounting of the Mk.3 to the Mk.4


Maybe the original Mk.3 does not mount the same as is shown here. I don't know. But it looks like it does put the 'A' arms in a better position to avoid this problem.

George

The lower mounting holes is the SAI mod built into the frame..The upper or "original" mounting holes is which the MK1,2,3,3.1 came with..I would use the lower holes..I have a MK 3.1 with SAI mod from Dave Borden..Same as a MK4 just I had to buy the adapter plates..

[chazbell]

Can anybody confirm what the total length of threads is? Or even better, what is the maximum amount of exposed threads one can have and still be “good”? I wound consider exposed threads the length between the jam nut to the knuckle.