Garth S

Injectable urethane has effectively been used by the BMW crowd to stiffen the OM bushings throughout the suspension .... with pleasant results: this appears to be a feasible mod for our 993's.
Replacement of the front control arm bushings recently discussed in this thread prompted me to take a prybar to the bushings as Geoff ( Red rooster) described ... and compare the deflection to a (nearly) new bushing I had mounted in a vise. Happily, they all appear equivalent - but nonetheless, it is relatively easy to compress the two asymmetric air voids molded into the bushings for NVH suppression.
The voids of the front bushings are easily accessible .... and look to be perfect candidates for injectable urethane: the objective is to increase the net bushing 'stiffness' to minimize this deflection by using a urethane of sufficient cured durometer/modulus ..... and still leave some NVH suppression (noise, vibration, and harshness).
The material of choice is 3M Windo-Weld 8609 Super Fast Urethane ....available in a convenient caulk gun cartridge .... at least the choice for me: before trying this, thought I'd open this one for discussion to see it there has been any BTDT, etc
The plus side is that it can be done on the car, and if the improvement does not meet expectations .... then tear them out and do the DIY discussed in the thread referenced. Cons???? - that's what I'm looking for .
The Viagra thing? .... just a cheap attention grabber ...

Red rooster

Garth,
If this new stuff can be pulled out easily ,will it just fall out when you are driving ? I would have thought that a seriously good adhesive would be part of the equation ?
One of the usual failure modes for the oe bushes is that they delaminate from the steel backing sleeve and can wander here and there !! Might be worth checking for a gap forming at the edge of the rubber bush ?
The bush fever has got you now - no escape !!
Geoff

tj90

Wow - it would be cool if this worked. Never considered this before. Wouldnt filling the gaps just strengthen only part of the bushings? I thought the bushings were purposely gapped to increase compliance in 2 axis.
Like Geoff mentions - not sure how effective this euthane would be with cracks or delaminations.

Garth S

Geoff,
This particular 3M product is an adhesive .... used for setting windscreens, etc: sticks like brown stuff to a blanket .. . Users reported damming the cavity with tape during the injection and leaving the car stationary until set-up. Then, the stuff is impossible to budge ... so 'fall-out' is unlikely.
I'm not suggesting this as a cure for delaminated bushings, rather a firming up of healthy bushings - which may keep them that way for a longer life. Besides, 5 min. of satisfaction with a caulking gun in hand is more appealing than 5 hrs of grunt work to cut old bushings out.

Red rooster

Garth,
OK, understood. The other thing that comes to mind is that the bushes have to give , to allow the wishbone to rise and fall . It would be pretty important to get the wishbone horizontal before applying the stuff .
Sounds like an axle stand under the wishbone and a jack on the front lift point .

A little bit of care but certainly an easy sounding job .
Looks like you have started something now !!

All the best

Geoff

ceboyd

well, the guys with SR20de equipped sentra's and G20's have used the stuff with great success.. as have the VW kiddies... cheap yet an improvement I've heard

Mark in Baltimore

Very cool post. Never heard of this. Thanks for the info, Garth.

Is there injectable steel?

chris walrod

One thing we used to do with our drag cars, being class specific where std rubber bushings are to be used, is to screw sheet metal screws into the bushings to stiffen them up.

Mark in Baltimore

Can you elaborate, Chris? I dumb and comfuzed.

chris walrod

Yes, looking at the end of a bushing, we would wind screws into the bushing circumfrencially about the inner pivot bush/fastener.