Ke36 Posted August 4, 2008 Share Posted August 4, 2008 Hey guys Have a problem with my diff conversion in the the diff pinion angle is now pointing in a downward angle, not good for unis etc What I want to do is lengthen my top diff arms in order to bring the angle of the diff more horizontal, diff is a triangulated 4 lin setup Rang the guy who will be certifying my car etc and he said that’s not a problem but just to check all the swing arc ratios etc, and it doesn’t bind etc Anyone got any usefull info on these ratios? I assume it’s the arc the suspension wants to take from the different upper and lower trailing arms and there respective relationships? Keen to know what difference lengthening my top arms will make and things I need to be wary of? Tried looking info up through google etc but came up with nothing just guys talking bout bike swing arms and music ratios lol cheers Quote Link to comment Share on other sites More sharing options...
Unclejake Posted August 4, 2008 Share Posted August 4, 2008 Coil springs? Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 4, 2008 Author Share Posted August 4, 2008 yea coil sprung spring sits on a seat on top of axel housing, i .e not a strut type arrangement heres a terrible pic from my project thread that top arm is the one im wanting to lengthen can see the spring seat sitting there too im not worried about the car handling like its completely on rails as i see a half cage and proper even length, parallel four link possibly in the not to distant future what i am worried about is fucking something up badly and my car handling worse than stock, being a bag of shit/dangerous heres a nice paint picture from the top view im keen to learn etc try to work some stuff out myself aswell but cant find any info about what i need to be checking, measuring etc rang a local diff place today to ask some questions about it and they basically told me to fuck off unless i was guna pay them to do the work Quote Link to comment Share on other sites More sharing options...
Unclejake Posted August 4, 2008 Share Posted August 4, 2008 Yikes! From your diagram and photos the entire arrangement is going to be fighting itself silly due to the different pivot points and arcs scribed by the top vs. the bottom arms. Are there spehrical bearings at the end of each of the longtitudinal links? I think you should jack the car up on stands, take your springs out and watch what happens to the diff rotation durring compression and rebound. Measure the distance from beneath the boot floor the diff sits at when the car is at rest first Before you start get some paper, string, drawing pins and a pencil. Looking side onto the car pin the string to the paper in positions relative to the upper and lower arms and cut two lengths of string to match the lengths of each arm. Scribe the arcs imagining the diff moving up and down and you will see what I mean. Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 4, 2008 Author Share Posted August 4, 2008 yea thats the factory arrangement, fricken stupid setup, no spherical bearings just normal rubber bushes real pain in the arse wishing id just gone the whole hog and taken my backseat out now for a proper four link but wasnt that keen on the idea of just having a 2 seater! unfortunately the car isnt with me at the moment is currently getting wired up and this is the last thing i need to have done before it goes on the dyno from the amount of fecking around id done earlier, during compression the diff head definately rotates downards, hence why since lowering it points where it does it has also "pulled" the wheel forward in the guard due to the fact the arms swing in the arc (making them effectively "shorter") so the whole diff moves forward, this is why my option is to lenghten the top arm as opposed to shortening the bottom arm which would pull the diff even further forward to straighten it up. is the thing the cert guy talking about where arcs intersect etc? obvioulsy my upper arm being shorter and having the mount slightly more rearward is going to intersect the arc of the lower arm does this need to happen at a certain point etc? i cant see with the limited amount of movement the rearend will be having that it will be all that much of a problem but i have no idea what im talking about Quote Link to comment Share on other sites More sharing options...
macabre Posted August 4, 2008 Share Posted August 4, 2008 hey, i had same problem with my diff when i put it in had the mad vibration when driving it, lengthened top arms 25mm i think. just jacked front of diff level then measured what total lenght of arm had to be, and got a new bit of tube welded onto the bush housings. worked mint Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 4, 2008 Author Share Posted August 4, 2008 yea the arse ends are a cunt aye probly been my biggest headache of the car sweet doesnt sound like its guna be do much of a problem then, did you even give any consideration to this sorta shit or just go for it? i was just guna do it and assume all would be sweet till the cert guy mentioned the swing ratios blah blah hopefully just a temp measure till the half cage and 4 link Quote Link to comment Share on other sites More sharing options...
macabre Posted August 4, 2008 Share Posted August 4, 2008 yea the arse ends are a cunt aye probly been my biggest headache of the carsweet doesnt sound like its guna be do much of a problem then, did you even give any consideration to this sorta shit or just go for it? i was just guna do it and assume all would be sweet till the cert guy mentioned the swing ratios blah blah hopefully just a temp measure till the half cage and 4 link i have a mental problem, i dont think before i do things thats why ive probably spent enuff time and money on my car to build it 3 times. But in saying that the top arms is one thing i havent had to redo lol Quote Link to comment Share on other sites More sharing options...
Testament Posted August 5, 2008 Share Posted August 5, 2008 are the arms anywhere near paralell with the ground at the moment? changing those lengths n a beam axle car will change antisquat/antidive more than your real roll centre (more controlled by panhard rod/ride height) but you need to know all the variables to really work out what your change might do i.e. lengths of all links and location of attachment points on body and on diff. and then because its for the angled top arms (like my 131 also) it makes it even harder as all the info out there is to do with plain 4 link setups. if you are a bit concerned about it you could lengthen the top arm and shorten the bottom arm, this will reduce the relative change. Hmmm I just looked at your pic again and noticed no panhard rod or watts link, is it just not bolted up? or do the angled arms do all the side to side axle location on these lancers? Quote Link to comment Share on other sites More sharing options...
WDE_BDY Posted August 5, 2008 Share Posted August 5, 2008 DELETED Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 5, 2008 Share Posted August 5, 2008 may not be much help but here are some piccys.. found them on my work comp, not sure where/what theyre from Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 5, 2008 Author Share Posted August 5, 2008 yea no panhard or watts just the top arms to stop that movement yea have been told what you said about the binding etc wde bdy by a couple clued up racing guys at work, they were trying to talk me into a proper 4 link when i was looking at getting my diff done and i should have listened to them i looked at modifying some adjustable arms for a ae86 to fit into my car but the tube thickness was too much and fouled where my chasis has allready been notched to fit these arms, plus the added cost of having to buy them then get them modded what level of fine tuning am i going to get from the adjustable arms?i was just going to go with diff head close to parallel to the ground maybe a little downwards angle (from what ive read on the net and been told this improves hookup on launch etc) this is going to be no worse handling wise etc than what it would have been stock? adjustable arms are just going to allow me to change pinion angle for better hook up etc correct? when you talk about the bottom mount, do u mean the lower arm mounting on the body?i have heard of lancer rally guys lowering theres by 12mm on lancerregister where would i look into for spherical rod end prices, avalibility etc? i would just get the diff end welded with a adjustable rod end section/sleeve if its worth it Quote Link to comment Share on other sites More sharing options...
esky 73 Posted August 5, 2008 Share Posted August 5, 2008 caldwells will have prices on rod ends, i reckon you mite want to look at a panhard rod, will help keep everything where it should be, on our commy race car we try to keep the diff head just below square, so whenn the power comes on the pinion trys to "climb" the crown wheel giving the effect of pulling the rear of the car downwards, so at max load/acceleration the diff flange will be square to the road, we dont have very much adjustment due to the regs of the class, but if we were allowd we would certainly have rose jointed arms, also handy to square axle to the car Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 5, 2008 Author Share Posted August 5, 2008 panhard rod, well actually probly a watts linkage, will come later on if i go the full hog four link/cage these arms are just to stop my car shaking itself to bits, and destroying components yea just below square is where we are aiming for but only just below, i guees if i go adjustable we can alter to where we want, just depends how pricey the bearings are at the moment its on like a 20 degree downward angle lol Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 5, 2008 Author Share Posted August 5, 2008 also is a rose joint going to give more movement around the point making it less likely to bind up?have been told not to nolathtane those bushes as it will handle worse than rubber bushes due to binding, so a rose joint would be the best option correct? just going to be a pain adjusting it with only one end adjustable, have to take the arm off one end etc Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 6, 2008 Author Share Posted August 6, 2008 ok talking to myself some more went and had a yarn to the engineering place and sorted what im going to do there guna take an old nissan or toyota adjustable arm, which ever fits better to my factory arms, and just weld the middle adjustable section into my factory lancer arms, no need for rose joint and still fully adjustable that way ive got whatever length i need and then adjustment etther way to get best diff pinion angle for launching etc sorted by the way have no idea bout swing ratios etc but Quote Link to comment Share on other sites More sharing options...
Unclejake Posted August 6, 2008 Share Posted August 6, 2008 ^ Good work. It will be fine. Not race car shit but fine none the less Quote Link to comment Share on other sites More sharing options...
Ke36 Posted August 6, 2008 Author Share Posted August 6, 2008 sweet yea at the mo its more of a need something that is going to work witout having to throw heaps of cash at it cos ill probly change it later on anyways, but at the same do do the job properly but not over the top just wanna get the damn thing going but at the same time not waste$$ and time on something im going to to redo Quote Link to comment Share on other sites More sharing options...
Jase Posted August 6, 2008 Share Posted August 6, 2008 i'll try an explain the set up for you a wee bit when you launch you are throwing those top arms into compression and your lowers into tension, if the force generated in tension does not become equal and opposite during this moment as to the compression it will bind or shudder, your top arms are going to compress in to a centre point but there momentum is parallel with the car so the diff is trying to push a bow in your top arms whilst pull the lowers towards the back of the car, the shudder happens when that bow occurs and your arms flex under accellaring meaning that the force on the lower arms is greater than your top arms can supply and your diff twists up and bounces/shudders, like a seesaw you can apply less weight at a greater distance to provide an equal amount of force to suspend that heavier weight at a shorter distance, so by making your arms adjustable you are going to be able to find the point of equilibrium where the forces all balance and it don't bind or shudder don't ask me bout going round corners but i hope that helps a little bit Quote Link to comment Share on other sites More sharing options...
Unclejake Posted August 6, 2008 Share Posted August 6, 2008 By unclejake at 2008-08-06 Quote Link to comment Share on other sites More sharing options...
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