bluespanner Posted October 22, 2009 Share Posted October 22, 2009 This must have been tried many times before, but what are the pros and cons of bending my own trailing arms? I would probably weld a gusset underneath the bend too. I've just ordered a set of +5" terrafirmas, so I cant justify the £100 or so for new ones. Roland (gas axe at ready ) Quote Link to comment Share on other sites More sharing options...
redneck Posted October 22, 2009 Share Posted October 22, 2009 If you bend them you are shortening them. Shortening them will alter your pinion angle causing potential problems with your prop-shaft. Adding spacers (washers) behind the bushing can restore the original length, depending on the amount of bend and the amount of thread left. Quote Link to comment Share on other sites More sharing options...
bluespanner Posted October 22, 2009 Author Share Posted October 22, 2009 Good point. Maybe I'd be better leaving the arms alone, and cutting the mounts off the chassis and welding them back on on an angle. Quote Link to comment Share on other sites More sharing options...
will_warne Posted October 22, 2009 Share Posted October 22, 2009 Standard arms are hugely weak. You could cut off the standard mounts but I wouldn't - just save up for a month or 2 and do the job properly. Quote Link to comment Share on other sites More sharing options...
redneck Posted October 22, 2009 Share Posted October 22, 2009 Good point. Maybe I'd be better leaving the arms alone, and cutting the mounts off the chassis and welding them back on on an angle. SVA????? Quote Link to comment Share on other sites More sharing options...
Martin.S Posted October 22, 2009 Share Posted October 22, 2009 Just bending standard trailing arms won't help, it's a actually a really bad idea, for two reason; a) it will shorten them which will try to pull the axle forward, which will also pull down the suspension A-Frame, stressing the A-Frame bush, bending the rear springs and damper forward; b) the bush holder at the axle end needs to be offset from the shaft to prevent fouling the mounting bracket. You're fitting cranked arms because of a suspension lift therefore they actually need to be longer (consider the hypotenuse of a triangle, it increases if you increases the height of the triangle). You need to match the length of trailing arms to your lift, the once size fits all approach of some trailing arms manufacturers is also wrong headed because of this. Quote Link to comment Share on other sites More sharing options...
AD90 Posted October 23, 2009 Share Posted October 23, 2009 For 2" lift, we bend standard ones and weld a length of angle-iron along the whole length (on the bottom) That seems to work, the amount they are shortened by is not enough to worry about - they will bind on the brackets a bit though, so I can't imagine what +5" would do! That's why the good after-market ones are offset at the axle end. AD90 Quote Link to comment Share on other sites More sharing options...
bluespanner Posted October 23, 2009 Author Share Posted October 23, 2009 SVA????? ??? I might have to just save up and buy made ones but it seems alot of money for something relatively simple. Quote Link to comment Share on other sites More sharing options...
western Posted October 23, 2009 Share Posted October 23, 2009 ??? I might have to just save up and buy made ones but it seems alot of money for something relatively simple. as moving the chassis mounts would be considered a chassis modification, after the mod the vehicle should to remain legal go through the SVA checks. Quote Link to comment Share on other sites More sharing options...
redneck Posted October 23, 2009 Share Posted October 23, 2009 ??? I might have to just save up and buy made ones but it seems alot of money for something relatively simple. I agree they are simple, however they are not a mass produced item and as such they will cost a reasonable amount. They are however a safety critical component of your vehicle. Unfortunately rarely can you change one component without consequence. Long travel shocks = modified trailing arms, high angle ball joint, spring relocaters/x spring, long brake hoses and wide anglle u.j.s. Not forgeting the front end mods to equalise the suspension travel/articulation. Maybe a granny/suck eggs post, but just in case. Quote Link to comment Share on other sites More sharing options...
simonr Posted October 23, 2009 Share Posted October 23, 2009 To avoid the axle end bush binding, you can modify the bracket on the axle a little and/or bend the arm at that end as well (making an 's' shape). Reinforcing the arm with angle seems to work pretty well - so just do the same on both ends. It is important to extend the arm so the axle is in the proper place - with the bottom spring seats horizontal. Not because of prop angle nor handling, but because in that position, you maximise the travel available in the A frame ball joint. Generally, the extension required is only in the order of 5mm and that can make a huge difference. You can achieve this by placing washers between the chassis outrigger and the rubber doughnut bush. Si Quote Link to comment Share on other sites More sharing options...
redneck Posted October 24, 2009 Share Posted October 24, 2009 This may go a little over the top as you are modifying not building new, but it does explain what goes on with your suspension and how small mods can make big differences in handling etc. Just changing one component can have serious implications. TBH spring seat angle is an indication of your axles angle, therefore pinion angle and upper ball joint angle, but the spring seat will not be parallel/level on a lifted vehicle. Also lifting your vehicle will actually reduce the articulation available on the upper ball joint. Obviously this is all for an ideal world scenario, but there are an awful lot of people out there adding massive shocks and springs and finding out their vehicle is undriveable. http://www.4x4.hr/2007/index.php?option=com_content&task=view&id=69&Itemid=9 Quote Link to comment Share on other sites More sharing options...
carl hurst Posted October 24, 2009 Share Posted October 24, 2009 This may go a little over the top as you are modifying not building new, but it does explain what goes on with your suspension and how small mods can make big differences in handling etc. Just changing one component can have serious implications. TBH spring seat angle is an indication of your axles angle, therefore pinion angle and upper ball joint angle, but the spring seat will not be parallel/level on a lifted vehicle. Also lifting your vehicle will actually reduce the articulation available on the upper ball joint. Obviously this is all for an ideal world scenario, but there are an awful lot of people out there adding massive shocks and springs and finding out their vehicle is undriveable. http://www.4x4.hr/2007/index.php?option=com_content&task=view&id=69&Itemid=9 Some good stuff in that link, Well worth a read, Carl. Quote Link to comment Share on other sites More sharing options...
bluespanner Posted October 24, 2009 Author Share Posted October 24, 2009 I'm building some spring relocators, and I have longer flexis already, aswell as decent props. As for the SVA thing, what would I have to do if I replaced my rear crossmember with a lump of box? Roland Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted October 24, 2009 Share Posted October 24, 2009 Unfortunately, I'd imagine that would count as a chassis modification as well. One could argue a crossmember replacement doesn't count as a mod, as it's a new part like-for-like, but fabricating your own crossmember probably does I think Quote Link to comment Share on other sites More sharing options...
bishbosh Posted October 25, 2009 Share Posted October 25, 2009 HFH asked that question of VOSA / DVLA and they were fine with it as it was an equivalent replacement. Quote Link to comment Share on other sites More sharing options...
muddy Posted October 25, 2009 Share Posted October 25, 2009 I thought you can fit the chassis end bush on the other side of the chassis bracket to account for the extra length or is this a no no due to the forces involved then being placed soley on the three bolts? Quote Link to comment Share on other sites More sharing options...
dieselweasel Posted November 24, 2009 Share Posted November 24, 2009 I just broke a trailing arm, a nice clean break on a weld that holds th' threaded bit to the the main bar. The main bar is hollow. It now looks really weak, I'm tempted to redesign it. You could easily make one to your own length, bend it, sleeve it whatever Quote Link to comment Share on other sites More sharing options...
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