mushroom inserts

[georgenewman1]

hi again, bought a set of mushroom inserts off of ebay for cheap, the only problem is that they have the hole in the middle, is this a problem as the book ststes that you need it offset toward the front, any ideas???

[alga]

AFAIU shifting the pivot point forward changes the effective length of steering arms, which in turn adjusts (I think) the front axis turn radius. If the mushrooms are centered, the axes of front wheels will intersect at the Sierra's standard wheelbase -- 2608 mm, whereas the Haynes Roadster's wheelbase is 2300 mm.

[frankie boy]

HI
The offset mushroom is for the caster. This mushroom is needed to maintain the correct geometry. Before SVA I had the centre hold mushroom but it didn’t self centre very well. I have noticed on some cars with the sierra upright haven’t used the offset mushroom or have the angle on the top wishbone not sore what affect this would have on the ride of the car.

[alga]

Frankie, I used to think so too, but consider this: the hub will rotate around the axis going between the top and bottom ball joints. Caster is the slant of this axis. The offset, or position, of the mushroom insert will not shift this axis at all.

[RAYLEE29]

I am no suspension expert but I beleive it has something to do with kingpin inclination.
the suspension is designed to use an offset mushroom so if you want your car to handle properly use one thats offset.
Ray

[squbti]

hi all, does anyone know if it would be ok to use ali mushrooms ?
cheers
Samy

[londonsean69]

Originally Posted by squbti

hi all, does anyone know if it would be ok to use ali mushrooms ?
cheers
Samy

No idea if it is OK, but mine are going to be Ally, when I get my lathe sorted.

I guess it also depends on what you are using for power, and how you are using it.

BEC vs Car engine
Road vs Track
etc.

Sean

[squbti]

yeh i think it should be ok too, i know there are some uprights made of ali so i cant think of any reason why ali mushrooms wont work .
Samy

[londonsean69]

MNR do theirs in HE30 ally (same as me), so no reason not to use ally.

Although I am sure someone will be along to tell us why not

As an aside, what are the 3GE inserts made from?

Sean

[Spikehaus]

Offset mushrooms are building an unstable pivot into the geometry. A grub screw may help any correct any movement for the IVA. I am yet to here of any calculations to backup this geometry. I have run this item past all the local precision engineers and yet to receive any feedback to the contrary.

I challenge some geometry based calculations or drawings to prove this? Ally is acceptable, but I recommend that that the stem is extended to fill the hub counter bore.