v8kid
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| posted on 11/11/08 at 04:24 PM |
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Polybush Crush
After carelessly wiping one corner of the suspension off on a tyre wall I decided now was the time to replace the bonded rubber bushes in my front
suspension with Polyrace polyurethane bushes and bought some from the nice Mr Rallydesign.
They come with the center steel sleeve or crush tube about 13mm longer than the bushes - I presume I have to shorten it to suit.
How much pinch or slack should there be?
The polybushes are have an internal measurement of 1" between shoulders and I have made the steel sleeve they fit into 30 thou oversize so the
bush halves will not quite meet in the center. This makes the extermal size of the polybush 1.335" how long should I make the crush tube? 1.32,
1.35" or what?
I don't want too much movement but on the other hand I don't want any stiction. What have you guys done?
David
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Flamez
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| posted on 11/11/08 at 04:46 PM |
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The bushes supplied by mac, meet in the centre, the crush tube is the length of the bush, not oversize, and all fits snugly into the chassis
bracket.
HTH
my build mac1motorsports
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907
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| posted on 11/11/08 at 05:17 PM |
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IMHO
The crush tube should be the same length as the gap in the chassis brackets.
When the bushes are inserted into the w/b tube up to the shoulders they should be about 0.25mm less than the crush tube.
A blob of grease is added inside the w/b tube before the second bush is pushed in.
The gap between the bushes is now filled with grease and any surplus is pushed out when the crush tube is inserted.
When bolted to the car the crush tube is clamped so it cannot rotate and the bushes are free to rotate on the crush tube
lubricated by the reservoir of grease between the bushes.
Once again, this is just my opinion, and is how I did mine.
Cheers
Paul G
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Danozeman
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| posted on 11/11/08 at 05:46 PM |
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I agree with 907 BUT you need rubber grease rather than normal grease as this will eat the bushes?!
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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v8kid
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| posted on 11/11/08 at 05:52 PM |
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Thanks guys it makes sense
David
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flak monkey
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| posted on 11/11/08 at 06:14 PM |
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quote:
Originally posted by 907
The crush tube should be the same length as the gap in the chassis brackets.
When the bushes are inserted into the w/b tube up to the shoulders they should be about 0.25mm less than the crush tube.
A blob of grease is added inside the w/b tube before the second bush is pushed in.
The gap between the bushes is now filled with grease and any surplus is pushed out when the crush tube is inserted.
When bolted to the car the crush tube is clamped so it cannot rotate and the bushes are free to rotate on the crush tube
lubricated by the reservoir of grease between the bushes.
Once again, this is just my opinion, and is how I did mine.
Cheers
Paul G
What 'e said 
Sera
http://www.motosera.com
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MikeRJ
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| posted on 11/11/08 at 07:00 PM |
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quote:
Originally posted by 907
The crush tube should be the same length as the gap in the chassis brackets.
Unless the brackets are the wide ones on the front upper wishbone to give some camber adjustment, and need to be packed out with washers.
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rusty nuts
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| posted on 11/11/08 at 07:27 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by 907
The crush tube should be the same length as the gap in the chassis brackets.
Unless the brackets are the wide ones on the front upper wishbone to give some camber adjustment, and need to be packed out with washers.
Think you mean caster adjustment. Quick way to test that everything operates as it should assemble the bushes with the crush tube and nip the crush
tube in a vice . Everything should rotate around the crush tube.
For those of you with a Luego it appears that the crush tubes supplied by Luego are too short.Check them as above . If your suspension is solid this
may be why. Sorry to hijack thread but it may save a load grief
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procomp
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| posted on 12/11/08 at 08:25 AM |
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Hi.
I think there is some confusion here between the std plastic bushes that the manufacturers are using and the proper polyurethane ones that are being
talked about here.
With the pollyrace type there is no tolerance on the crush tube. It should be the same lenght as the bush when assembled into it's housing.
Mind if opting for the true polyurethane type bushes the Superflex ones get my vote and they also come in a choice of shore ratings and with a
stainless crush tube as std and sachets of the correct grease. 
Cheers Matt
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MikeRJ
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| posted on 12/11/08 at 10:20 AM |
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quote:
Originally posted by rusty nuts
Think you mean caster adjustment.
You are absolutely right, I do!
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Syd Bridge
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| posted on 12/11/08 at 04:42 PM |
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[quote
Mind if opting for the true polyurethane type bushes the Superflex ones get my vote and they also come in a choice of shore ratings and with a
stainless crush tube as std and sachets of the correct grease.
Superflex are rebranded Superpro bushes, available from Superpro direct. Standard are steel bushes, but they'll supply stainless if you ask.
www.superpro.eu.com
Nice people to deal with, and very helpful when looking for odd sizes.
The Superpro stuff cannot be beaten. The best!
Cheers,
Syd.
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v8kid
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| posted on 12/11/08 at 05:21 PM |
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Thanks chaps I emailed the manufacturers and they said ;_ "Crush tubes are just sub flush, to seal out dirt and water."
I see where the manufacturers are coming from but from the performance point of view rather than the longevity I reckon I'll follow you guys
advice.
I'll let you know if it goet tits up and I end in the trye wall again
Will check out superpro next time I buy some.
David
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