Board logo

Shrooms
craigdiver - 29/8/17 at 06:44 PM

I have bought anodised blue mushrooms for my front sierra hubs. These have the hole for ball joint taper in the centre. I have also got mushrooms with an offset hole.

Will I be ok with the blue ones with the hole centrally? Or is there a good reason for me to use the offset ones?

ian locostzx9rc2 - 29/8/17 at 07:28 PM

Offset ones will give you some camber/castor adjustment

loggyboy - 29/8/17 at 07:28 PM

Offset is to allow camber adjustment, but will also affect caster/kingpin inclination. So car will need geometry redone.

adithorp - 29/8/17 at 08:46 PM

quote:
Originally posted by loggyboy
...will also affect caster/kingpin inclination...


Hmm, bit of a can of worms but... no it won't. As the ball joints don't move relative to the chassis (or each other) then the castor angle doesn't change. The trail will, as the spindle position moves relative to the ball joints. That does affect steering in a similar way to altering castor but it's not the same thing.

craigdiver - 29/8/17 at 08:51 PM

I found these issues when I tried to find an answer myself, car is not going to be raced so should I just fit the blue ones initially as long as I'm getting sufficent steering centering?

Minicooper - 29/8/17 at 09:05 PM

They are not for camber or castor, I do know what it's for directly from the horses mouth (Chris Gibbs) so to speak but I'm finding it difficult to explain in words, I see if I can find a picture to help.

One thing it seems that people have had good results with out the offset and just used the much cheaper centre bored alloy mushrooms from Rally Design

As you have both why not use the offset mushrooms as per the book plans

David

[Edited on 29/8/17 by Minicooper]

bonzoronnie - 30/8/17 at 08:03 AM

quote:
Originally posted by Minicooper
They are not for camber or castor, I do know what it's for directly from the horses mouth (Chris Gibbs) so to speak but I'm finding it difficult to explain in words.

[Edited on 29/8/17 by Minicooper]


Same here

I spoke to Chris about the offset. He explained that the offset was never intended to be a means of adjustment.

Offset as far forward as possible then locked into place with a grub screw.

As with Minicooper, cant't remember the exact terminology or words, but the offset was introduced to the mushrooms purely to get a better degree of self centering of the steering.

ETA

Matt at Procomp recently gave his comments on the offset issue.


Quote:

"Hi.

Just buy the rally design ones. Having the offset is a complete waste of time. Anyone selling offset inserts claiming to be for caster correction is talking complete rubbish.

Cheers Matt "

Given Matts experience in this field, It would be unwise to not heed the advice given.

[Edited on 30/8/17 by bonzoronnie]

snapper - 30/8/17 at 07:41 PM

The offset mushrooms allow the ball joint to be located at rest in the central position as the top wishbone is not normally horizontal