frank280zx Posted February 4, 2007 Share Posted February 4, 2007 Why is a semi-trailing arm so bad? as sqaud would improve grip or not ? In my car i have the solid mounting busings, nylon struts bushings with a set of adjustable konis on a 175 Springfield.. my squad is not that bad, and actually it helps me get trough a corner faster as it plants the ass in on my slicks... The site 260zed pointed out is in my bookmarks, as e30's over here are over competitive .. The set up to control camber is relatively complex and expensive. Moving the degree of the sweep angle (angle of the rear sub-frame compared to straight. In a s130 this comes down to ~14 degrees as far as i recollect to the Say between 10 and 12 degree sweep angle ( As the M3 group a and B cars had) is that the rear suspension will have less camber and toe change as the suspension travels. To be honest i like trailing arms better than a arms.. probably since i' m used to them from driving e30's and a souped up 914 powered bug and naturally my z's they are more stable in corners for my taste ( or better more predictable for me) More so than my experiences in s30's ( this maybe tells more about those s30's haha) To quote the site 260zed pointed out ' But also note that this is not necessarily desirable. You do want some gain in negative camber as the suspension compresses to compensate for chassis roll in cornering. It would be nice if it did not change during acceleration and braking but that is tough to achieve. Some small amount of toe-in as the outside rear wheel compresses in cornering is also nice, as it adds a bit of rear-end stability.' Witch is exactly what my friend and rally race car builder explained to me. So now im curious how squad hurts launching?? I can think of the camber changes thus using less of the tires width, but would drag radials and indeed some stiffer springs not solve this? And doesn't the squad press down the tires into the asphalt more than say a A arm or solid ? Quote Link to comment Share on other sites More sharing options...
mtcookson Posted February 4, 2007 Share Posted February 4, 2007 When launching you do want some squat as squat is simply the transfer of weight to the rear (this is why front wheel drive cars are terrible at launching). If your car squats pretty hard and the camber changes quite a bit you're not getting a good tire patch on the ground, its riding on the tire closer to the edge so a lot less traction. What's weird is I would think a trailer arm setup like that would make way less camber changes than an a-arm setup, but I guess they're setting the angles up differently than what I'm thinking. Quote Link to comment Share on other sites More sharing options...
NissanSportMag(Z31) Posted February 4, 2007 Share Posted February 4, 2007 Yes. In road racing, some camber changes are desirable. But the focus of this thread was on drag racing. And camber changes are bad when drag racing. Camber changes make less tire available to the traction part of the equation. And yes. Camber changes in a single A-Arm setup are significantly greater than a semi-trailing arm system. But I don't know the last time I've seen a single a-arm system on a real car. And since we're talking about the Z31 here, the majority of these cars ride at a neutral setting. i.e. about 0 degrees of camber while sitting. Once you launch, the squat makes a fairly significant change in the camber. And, as mentioned, lots of negative camber makes for a loss of traction. Which results in tire spin and slower ETs. The link is a very interesting read, and not something I hadn't thought of myself. But it really doesn't delve into how to fix it. It just gives the raw data. Problems arise when people don't do anything to fix their 20+ year old springs and wonder why they can't get good times at the drag strip. I've seen Z31s with suspension so worn out the back bumper actually hits the ground and leaves sparks from the undercarriage. And that is a significant (6" +) change in geometry. The way I've seen this best reduced is with helper air bags filled to their limits. Weight transfer does occur during squat, but you don't need squat to get weight transfer. A strong motor will raise the front wheels (even if only slightly) and result in weight transfer. Squat that causes traction loss is not a good thing. Quote Link to comment Share on other sites More sharing options...
260DET Posted February 5, 2007 Share Posted February 5, 2007 Actually I know bugger all about drag racing, but is there any advantage with an independant rear there at all? More even weight distribution to the tyres when the body twists under torque? Quote Link to comment Share on other sites More sharing options...
NissanSportMag(Z31) Posted February 5, 2007 Share Posted February 5, 2007 Nope. Solid rear axle is better most of the time. I understand a lot of Mustang Cobra owners swap out their IRS for solid axles if they plan on drag racing. Quote Link to comment Share on other sites More sharing options...
260DET Posted February 6, 2007 Share Posted February 6, 2007 Maybe not as much effort has gone into developing IRS for drag racing? For example, bit of toe in at the rear usually helps stability, easy to adjust on IRS, you don't need a 100 ton press to bend the diff housing Quote Link to comment Share on other sites More sharing options...
NissanSportMag(Z31) Posted February 7, 2007 Share Posted February 7, 2007 Maybe not as much effort has gone into developing IRS for drag racing? For example, bit of toe in at the rear usually helps stability, easy to adjust on IRS, you don't need a 100 ton press to bend the diff housing in a straight line, the thing that helps is toe. but any camber changes greatly affect actual traction. and to maximize traction, you want zero to no camber. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted February 7, 2007 Share Posted February 7, 2007 Just run crazy big tires... like... dually MT's or something. Quote Link to comment Share on other sites More sharing options...
evildky Posted February 16, 2007 Share Posted February 16, 2007 he might only be running 12.4 but at 124 mph! that's low 11 range, can you say traction limited? and I believe the curb weight is supposed to be around 3200 for a stock Z31, and the GLL's had some super duty sound deadening, I'm building a Z31 right now and hoping to get it down to aobut 2700lbs Quote Link to comment Share on other sites More sharing options...
2+2 turrrbo Posted February 17, 2007 Share Posted February 17, 2007 actually a 2 seat z31 will weigh around 3000lbs stock (2+2 is around 3200), you can easily get it down to 2700 if you strip it out ... Quote Link to comment Share on other sites More sharing options...
typhoone Posted February 17, 2007 Author Share Posted February 17, 2007 what all can be stripped out of it??? i know mine doesn't have AC in it, but what else can be taken out? just wondering Quote Link to comment Share on other sites More sharing options...
Sparks280zt Posted February 17, 2007 Share Posted February 17, 2007 Theres an amp under the passenger seat in some models, the stock seats are heavy, atleast mine is because it has the lumbar support. You can toss the spare tire, jack, and the little stop things. Toss out the curise control stuff if you like. Quote Link to comment Share on other sites More sharing options...
2+2 turrrbo Posted February 17, 2007 Share Posted February 17, 2007 the sound deadening , evaporator and other stuff behind the dash.several things in the engine bay . you can easily shave 200lbs from a stock z31. get creative... Quote Link to comment Share on other sites More sharing options...
NissanSportMag(Z31) Posted February 17, 2007 Share Posted February 17, 2007 the metal bumpers some extra bracing inside the car dash etc. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted February 18, 2007 Share Posted February 18, 2007 pull the engine, tranny, diff, and cut a hole in the floorboard and do a fred flintstone! That would be good for at least 500-600 lbs. (i'm sorry, i don't have anything better to add) Quote Link to comment Share on other sites More sharing options...
premo-s12 Posted February 22, 2007 Share Posted February 22, 2007 LOL'in! Quote Link to comment Share on other sites More sharing options...
evildky Posted February 23, 2007 Share Posted February 23, 2007 sound deadening material, undercoating, the stock seats are pretty heavy, ditch all the carpet and padding as well as the firewall insulation, no pass seat at all, no HVAC, no door panels or any interior panels, power steering opump and resivior, all the emisions crap, the bumpers under the covers with bumper shocks, lots fo stuff to remove when the only consideration is getting weight out, and if you've ever pulled a power seat you know those things weight a ton Quote Link to comment Share on other sites More sharing options...
260DET Posted February 23, 2007 Share Posted February 23, 2007 what all can be stripped out of it??? i know mine doesn't have AC in it, but what else can be taken out? just wondering OK, starting right at the back - steel bumper (replace with aluminium/f'glass substitute), metal tail light retaining plates, metal number plate lights (use plastic), radio antenna and wiring. Get the idea? Quote Link to comment Share on other sites More sharing options...
typhoone Posted February 23, 2007 Author Share Posted February 23, 2007 got it Quote Link to comment Share on other sites More sharing options...
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