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Modified front suspension - Overloaded Trunnions?

Posted: Wed Jun 13, 2012 10:23 pm
by oilypaws
Hi,

Just looking at cars for sale locally and saw this:

http://www.trademe.co.nz/motors/used-ca ... 239209.htm

A 1600 twin cam toyota engine might be fun, but the setup looks a bit dodgy to me. Apart from the underfloor bracing which may or may not be OK, I note that they have cut out the engine bay cross-member (between the upper suspension mounts) to get the engine in - Would I be right to think that will weaken the car?

Looking at the pictures, I noted the addition of telescopic dampers, and wondered about the effect on the bottom trunnions at the front.

*Normally, the lower trunnion takes the weight of the car and transfers it to the spring.
*However, when the wheel hits a bump, the armstrong dampers SHOULD resist the movement of the wheel (at least somewhat) so some of the shock load will go through the kingpin to the damper.
*BUT, with the setup shown, i.e. damper going to the lower suspension arm, this would actually ADD the shock load of hitting a bump to the load that the lower trunnion carries.

Having read posts about trunnions failing, i'd be nervous about increasing the loads on them!

Is this the normal setup for modifications (i.e. coil-overs or telescopic dampers)?

I'm just about to overhaul my front suspension, and the car has done a lot of miles (not with me - I've only done about 30km total getting it home!). I think I'll take the trunnions apart and inspect them, and see if I need new ones. Any suggestions as to what I should look for?

Thanks for the help! This is a very handy forum.
Regards!

Re: Modified front suspension - Overloaded Trunnions?

Posted: Wed Jun 13, 2012 10:47 pm
by Alex'n'Ane
Cutting the cross member is fine, as long as it was braced, and re strengthened when re-shaped. (jlh does this to fit the zetec) It atleast looks a fairly good job, not a bodge from those pictures anyway... The damper kits all mount on the lower arm, so thats not the issue. There are now more "modern" alternative welded mountings, see jlh website for the dampers, but still similar, just the top is welded elsewhere slightly. But that is a very traditional and common design for the tele dampers.

Re: Modified front suspension - Overloaded Trunnions?

Posted: Thu Jun 14, 2012 12:28 am
by bmcecosse
The front dampers won't add any worrying load to the lower trunnions - BUT - note they are mounted about half way along the lower suspension arm - so their effectiveness is much reduced. The top mount is also weak... They really do need (as Alex mentions) a properly welded in mounting. However all this is nothing compared to the ridiculous rear damper installation - with the dampers at 45 degrees to the suspension movement! Madness !!!! And yes you are right to worry about cutting away the bulkhead crossmember - it would need much alternative strengthening - and IF that has been done - it will be fine. There is something seriously wrong with the prop-shaft/final drive connection - just look at the horrible angle . it will never work like that. :roll:

Re: Modified front suspension - Overloaded Trunnions?

Posted: Thu Jun 14, 2012 7:48 am
by kennatt
like mbc says the angle of the prop axle would cause me some concern,would think that the uj would need changing at regular intervals.

Re: Modified front suspension - Overloaded Trunnions?

Posted: Fri Jun 15, 2012 2:03 am
by oilypaws
kennatt wrote:like mbc says the angle of the prop axle would cause me some concern,would think that the uj would need changing at regular intervals.
Yeah I thought that looked a bit odd too...
Thanks for comments!