nnrouty
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| posted on 7/9/10 at 09:35 PM |
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why are these so cheap?
Hi all
been looking for the sierra mushroom inserts for my project and found they are around £40 for the pair at most places.
But why are the rally designs inserts so cheap?
http://www.rallydesign.co.uk/product_info.php?cPath=1375_1594_1600_1601&products_id=13003
As long as its fast.... i don't care
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LBMEFM
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| posted on 7/9/10 at 09:38 PM |
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Not so sure why they are cheap but I would trust Rally Design though. Barry
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big_wasa
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| posted on 7/9/10 at 09:40 PM |
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Mass produced and the center tappered hole instead of being offset will also make them cheaper to make.
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dan_g8
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| posted on 7/9/10 at 09:41 PM |
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not sure why but they do not have the offset hole which you need if your building the haynes roadster.
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big_wasa
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| posted on 7/9/10 at 09:47 PM |
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why do they need to be offset for the roadster ?
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austin man
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| posted on 7/9/10 at 09:51 PM |
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the offst allow for adjusting of castor as it gives a cam effect I believe
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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big_wasa
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| posted on 7/9/10 at 10:17 PM |
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Many a thread on here that says it doesnt actually alter the castor.
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Minicooper
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| posted on 7/9/10 at 10:24 PM |
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Well on a test build up I had the offset mushroom adapters in the wrong way and the castor was no where near the 20mm quoted. Turned them round and
got the castor that I expected.
Cheers
David
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big_wasa
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| posted on 8/9/10 at 06:12 AM |
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quote:
Originally posted by Minicooper
Well on a test build up I had the offset mushroom adapters in the wrong way and the castor was no where near the 20mm quoted. Turned them round and
got the castor that I expected.
Cheers
David
Thanks so worth the extra twenty quid then.
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Mark G
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| posted on 8/9/10 at 06:32 AM |
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It's always been a hot topic on here as to if they adjust the caster or not.
I say that they do as the centre point of the wheel is moved in relation to the top and bottom ball joints when the mushroom is adjusted. It is worth
the extra to get offset inserts because you'll struggle to setup your suspension without them.
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Minicooper
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| posted on 8/9/10 at 09:09 AM |
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quote:
Originally posted by big_wasa
quote:
Originally posted by Minicooper
Well on a test build up I had the offset mushroom adapters in the wrong way and the castor was no where near the 20mm quoted. Turned them round and
got the castor that I expected.
Cheers
David
Thanks so worth the extra twenty quid then.
It happens to be the truth, what else can I say, I have no axe to grind here
I looked at the Rally Design mushroom adapters and could have easily moved the top wishbone mounting brackets a small amount to compensate, but a
cheap pair of offset mushrooms came up so I used them
Cheers
David
[Edited on 8/9/10 by Minicooper]
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procomp
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| posted on 8/9/10 at 11:36 AM |
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Hi
Like a lot of stuff supplied these days it originates from China.
The offset items do not adjust the Castor. It's the joints centers that dictate Castor not the upright it's self. It was Mk that started
to do the offset items to supposedly correct the Castor. Then every one else copied them. Complete stupidity and a complete and utter lack of
understanding of basic geometry.
Cheers Matt
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hellbent345
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| posted on 8/9/10 at 11:55 AM |
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the offset centre sorts the anti dive geometry of the sierra upright (apparently) and doesn't adjust castor really... There could be a small
effect induced with moving the wheel centre behind the 'line' between top and bottom joints (i.e. like a supermarket trolley wheel) but
this will be small, and the inserts shouldn't be used for that anyway.
They are cheap because they can be mass produced with a bar feed on a normal lathe with a three jaw chuck - offset inserts require either a 4 jaw
chuck or some sort of live tooling to create the offset, or moving it to a mill etc. Basically more work.
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Minicooper
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| posted on 8/9/10 at 12:32 PM |
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Procomp you know much more about than I ever will, but something is very different depending on the offset mushroom adapters position.
I will take a couple of pictures to show people what I'm trying to explain, one way must be the right way.
Had a poke round the Haynes forum it appears as the offset mushroom is for this quote:
"The reason they are offset is to align the top and bottom pivots with the axle centre line better, If you draw an imaginary line through the
Sierra upright you will see that if the mushroom insert is concentric it will miss the centre line of the axle, requiring more effort to self
centre." Another quote: "The effective castor is less than the actual castor the further away you get from the centreline of the
axle"
I'm not claiming to know anything about suspension geometry that's why I followed the book exactly, including the offset mushrooms.
Even with any potential defiences it will be way better than anything I could do
Cheers
David
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procomp
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| posted on 8/9/10 at 01:58 PM |
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Hi
In very basic terms they are using the offset to align the axle center with the joint centers. But the amount of movement is not enough to worry about
given the very small effect it has upon the handling as a result given the very basics are so far out in the first place.
By all means use the offset items but moving the axle center a few MM without getting the rest of the basics right is a little pointless.
Its still amusing how they have gone from being sold as Castor adjusters to now being sold as highly technical handling improvement devices.
Cheers Matt
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l71300cc
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| posted on 19/10/11 at 08:48 PM |
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If someone can give me the exact dimensions of the mushroom insert with the offset then i can make a pair for a good price for those interested.
thanks,
Albert.
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Talon Motorsport
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| posted on 19/10/11 at 09:57 PM |
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current price is £45 a pair with free postage , off you go then....
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NigeEss
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| posted on 19/10/11 at 11:19 PM |
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I'm sure I've read somewhere that the offset mushroom affect KPI and camber but
not caster.
Time is an illusion. Lunchtime doubly so.................Douglas Adams.
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TheGecko
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| posted on 20/10/11 at 12:32 PM |
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Here's a diagram scanned from "Car Suspension at Work" (ISBN 1-899870-31-8)
What turning one of those offset mushroom things is changing is the Castor Trail NOT the Castor Angle. The Castor Angle is
fixed by the relationship between the top and bottom ball joints which an offset mushroom isn't changing.
Simples?
Dominic
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Steve Hignett
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| posted on 20/10/11 at 02:21 PM |
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quote:
Originally posted by l71300cc
If someone can give me the exact dimensions of the mushroom insert with the offset then i can make a pair for a good price for those interested.
thanks,
Albert.
That's kind of you to offer your time for someone on here...
quote:
Originally posted by Talon Motorsport
current price is £45 a pair with free postage , off you go then....
I don't work in the motorsport industry, so I don't know how it worls there, and I've never been regarded as intelligent, so I could
be wrong, but;- I'm not sure that telling someone what something costs (inc free postage) constitutes exact dimensions...................
Or is it that I'm just not up on the young persons vernacular when it comes to sarcam?
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40inches
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| posted on 20/10/11 at 03:06 PM |
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quote:
Originally posted by Steve Hignett
quote:
Originally posted by l71300cc
If someone can give me the exact dimensions of the mushroom insert with the offset then i can make a pair for a good price for those interested.
thanks,
Albert.
That's kind of you to offer your time for someone on here...
quote:
Originally posted by Talon Motorsport
current price is £45 a pair with free postage , off you go then....
I don't work in the motorsport industry, so I don't know how it worls there, and I've never been regarded as intelligent, so I could
be wrong, but;- I'm not sure that telling someone what something costs (inc free postage) constitutes exact dimensions...................
Or is it that I'm just not up on the young persons vernacular when it comes to sarcam?
Ah! young persons sarcasm, thought I recognized it. Having a 17 and 18 year old in the house, you sort of get used to it
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snapper
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| posted on 20/10/11 at 03:38 PM |
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If you have a camber adjuster where the top ball joint joins the wishbone then some washers either side of the chassis mo ts can adjust wishbone trail
for caster.
Usually the offset top hole in the mushroom is for the ball joint taper to be set at the correct angle in bump and rebound as wishbones are straight
and not kicked up (or down)
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Talon Motorsport
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| posted on 20/10/11 at 04:59 PM |
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The dims for the mushrooms are on the haynes forum easily found with a basic search,funny that haynes parts drawings on the haynes forum? Knowing how
long it takes to set a manual lathe up to do a pair of off set mushrooms and what the material costs per pair I mearly stated that if some one wants
to give their work away for next to nothing then they are more than welcome to.
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