J666AYP
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| posted on 4/9/19 at 04:51 PM |
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To rose joint or not to rose joint??
Gents,
I know this has been touched on in the past. I'm ready to start building my rear wishbones but I need to decide on either bushings or rose
joints, anyone have any insight into this? I have worked out all the options in my head along with pros and cons of both set ups but I'm left
wondering if rose jointed wishbones would be too harsh for road use?
The way I see it:
Pros to rose joints...
• Much finer adjustment
• Less movement in the whole system
• Fewer squeaks and noises
• Probably more predictable handling
• The coilovers do all of the work
• More connected feel to the car and what its doing
Cons...
• More uncomfortable
• Little to no adjustment with bushes
• More wear/stress on other components
• Price
• more fabrication work
Anything I have missed?
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jelly head
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| posted on 4/9/19 at 05:53 PM |
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i think you've nailed it there.
i found ride quality to be fine on the road with rose joints but personally i wouldn't have them again on a pure road car as they wore out
pretty quickly (maybe they were crap qality), and they're not cheap to replace.
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melly-g
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| posted on 4/9/19 at 07:53 PM |
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I've got 4 of them, some poly bushes and metalastic bushes on the rear of the Avon.
I've only had to replace 1 rose joint in 12 years! Non of the others though?
More than happy with that!
Not harsh at all, but as I said I've got a mix of all types of bushes.
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coyoteboy
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| posted on 5/9/19 at 08:05 AM |
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I don't really see why, if designed correctly, it would be any significant amount more harsh or fast wearing. I've been in fully rose
jointed cars that were super supple and lovely. If they're sized right they won't wear out early.
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peter030371
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| posted on 5/9/19 at 08:10 AM |
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First Striker had metalastic bushes and was a handful on the road (fine on track) as the suspension tried to control the car on less than perfect
roads, bushes all had to be replaced every 6 or 7 years (I had it 18 years in the end so replaced them twice) as the rubber had perished from age.
Adjusting the dampers one or two clicks had a different impact on the handling as the bushes aged (I didn't realise this until I built the
second car, see next paragraph) 
Second Striker is fully rose jointed, the suspension is now only controlled by the dampers/springs which makes road use sooooo much smoother (smooth
track is still great). With the car on stands and the dampers disconnected the wheels can be lifted up and down smoothly and with ease over the full
range of travel...just seems to 'feel right' IMHO. Adjusting the dampers a few clicks has a consistent effect even to this amateur driver
When fitted correctly metalastic bushes have a rising rate effect and I am not sure that is right on a light weight 7 style car. You can measure this
and tune the suspension to 'cope' with this but why should you need to? How many well sorted 7 cars do you see with rising rate
springs?
Including build time the joints are now 5 years old (only down 1000 miles, similar to the old Strikers use though) and they are all still in A1
condition. If they had been metalastic bushes I would be thinking about replacing them all in the next year or two due to age
To me:
Pros of rose joints
the suspension just works so much better
Cons of rose joint
they cost more (but then I would cut back in other areas to cover this cost if need be)
Pros of metalastic bushes
cheaper initial outlay
Cons of metalastic bushes
will wear out, even if not used
do not allow proper suspension control
Never used poly bushes so can't comment on them.
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davew823
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| posted on 5/9/19 at 10:36 AM |
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rose joints
A good compromise is a combination of both. Use the rose joint on the axle attachment side and the rubber bush on the chassis side. This allows axle
adjustment and isolates the frame from the noise and vibration. Also install "Seals-it" on the rose joints. This can easily extend the
life of the rose joint by 2 or 3 times. davew823
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MikeRJ
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| posted on 5/9/19 at 11:44 AM |
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quote:
Originally posted by peter030371
When fitted correctly metalastic bushes have a rising rate effect and I am not sure that is right on a light weight 7 style car. You can measure this
and tune the suspension to 'cope' with this but why should you need to? How many well sorted 7 cars do you see with rising rate
springs?
The force required to twist the bushes is a tiny fraction of the force required to compress the spring. Remove the shock and you can move the bottom
arm up and down by hand, put the shock back on and you'd struggle to move it more than a few mm.
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coyoteboy
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| posted on 5/9/19 at 01:39 PM |
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Guess it depends on the bush, I can barely move the arm on one of my cars without the spring, but by the same token, deflection in any of the other
axes is relatively easy too, making them a bit miserable from a control perspective. A swift pull and I can deflect my tin-top contact patch 10mm
backward.
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peter030371
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| posted on 5/9/19 at 02:05 PM |
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quote:
Originally posted by MikeRJ
The force required to twist the bushes is a tiny fraction of the force required to compress the spring. Remove the shock and you can move the bottom
arm up and down by hand, put the shock back on and you'd struggle to move it more than a few mm.
When I was young free and single and had nothing better to do at weekends I did measure the force on one corner of the car and although I don't
recall the figures (it was nearly 20 year ago) I remember it was a few % of the spring rate on the same corner. Maybe the ones JP fitted on my Striker
were different (he never did follow anyone else). By 'feel' the amount changed with the ageing of the rubber in the bushes, hence I
replaced them all twice during my ownership.
Use rose joints and its a few more % that doesn't change/ is controlled and is in your favour when it comes to predictable handling over time
Obviously if the cost of new rose joints when (or if) they wear out is an issue to you then accept the compromise of the cheaper bushes. They clearly
do work as many, including me on my old Striker, use them but rose joints just seem better in so many ways/ Personally its a choice I made and
has given me a car that is better for my use 
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Bluemoon
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| posted on 5/9/19 at 02:15 PM |
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^^ Poly bushes and metalastic bushes are different... Poly bushes also come in different hardness to add to the complication. If poly bushes require
much force something is wrong and should be investigated.
Metalastic are more compliant, poly bushes can vary from compliant to rock hard, Rosejoints are rock hard. Some suspension geomterys rely on the
"compliance" to stop binding and would lockup with rose joints...
As usual, there is no "correct" answer, just different compromises.
Dan
[Edited on 5/9/19 by Bluemoon]
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JimSpencer
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| posted on 6/9/19 at 06:59 AM |
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quote:
Originally posted by davew823
A good compromise is a combination of both. Use the rose joint on the axle attachment side and the rubber bush on the chassis side. This allows axle
adjustment and isolates the frame from the noise and vibration. Also install "Seals-it" on the rose joints. This can easily extend the
life of the rose joint by 2 or 3 times. davew823
This or a variation thereof
But not because one is 'better' than the other.
But because it allows you to align / set up the car properly once it's built, shimming brackets or worse still cutting them off and moving
things (Got that T shirt  ) is a right PITA, build adjustability in at the design stage and then 'make it as straight as you can' gives
you a solid foundation to get a good handling car IMHO.
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Oddified
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| posted on 6/9/19 at 06:44 PM |
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Assuming the car is to be more performance orientated, then any bushes would be fairly stiff any way so the difference between a few bushes and rose
joints is negligible. As Jim mentioned above, making the suspension adjustable is also far far easier with rose joints.
Ian
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J666AYP
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| posted on 7/9/19 at 12:29 AM |
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Thanks for all the info gents, has been very helpful.
Right I have started building again (sigh). I am in the process of building my rear uprights/hub carriers then I can start on the wishbones. I'm
going to be using polly bushes on the car end and rose joints/spherical bearings or whatever they are called on the spinny rubbery end. Will alow for
some dampening of vibration and at the same time be easier to adjust.
This leads me onto my next question... I have started my uprights and it's going very well so far, the only issue I have is that the rear lower
wishbones wont be horizontal to the ground without some complicated changes that have there own problems. Would it be a real issue to have the lower
wishbones angled up towards the hub by a little bit? Probably a 3/4"-1"from inner mounts to the mounting on the upright?
I guess this is the price for doing things a little bit differently
[Edited on 7/9/19 by J666AYP]
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J666AYP
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| posted on 7/9/19 at 04:32 PM |
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Ok scrap the 3/4"-1" its 10mm that the lower wishbone is raised by towards the hub. Is this going to be a problem?
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Oddified
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| posted on 7/9/19 at 09:40 PM |
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quote:
Originally posted by J666AYP
Ok scrap the 3/4"-1" its 10mm that the lower wishbone is raised by towards the hub. Is this going to be a problem?
Short version of effect is a lower roll centre, but that's only a part of the overall picture and without knowing other factors such as weight
distribution and cg i wouldn't say good or bad.
Ian
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J666AYP
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| posted on 8/9/19 at 10:25 PM |
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Cheers mate, have got the gap down to +/-3mm now so fingers crossed...
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