Ron240zxt Posted October 21, 2001 Share Posted October 21, 2001 Just wondering if its possible to make a z car lift the front tires off the ground with the factory rear Suspension. Or How would you convert it to a ford 9in? Just curious. Thanks Ron Quote Link to comment Share on other sites More sharing options...
stony Posted October 21, 2001 Share Posted October 21, 2001 Im pretty sure there isnt a stock IRS in any car out there that could withstand the impact of a wheel lift launch. Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted October 21, 2001 Share Posted October 21, 2001 Ron i have a freind in TX running NOS that has done it. I have seen pictures. Unfortuantely the rearend blows up after like two runs or something breaks. Its a full drag car btw. IE no dash and stuff. Ev Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 22, 2001 Share Posted October 22, 2001 i would love to see that // physics make it almost imposible for a zz to lift the front end... MY car runs mid nines and I have cut 1.40 short times and the wheels come no where near lifting.. the way the independant rear is set up the suspension squats instead of lifitng the front of the car ... to lift the front the car would have to have almost solid rear springs and drag springs with drags struts in the front.. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 22, 2001 Share Posted October 22, 2001 [ October 22, 2001: Message edited by: 1fstz ] Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted October 23, 2001 Share Posted October 23, 2001 Hrm, perhaps he does have a solid rear and i was mistaken. Evan Quote Link to comment Share on other sites More sharing options...
jeromio Posted October 23, 2001 Share Posted October 23, 2001 Someone posted pics and an mpeg of I think a 260Z with a reportedly stock IRS lifting the fronts off the ground. This was in response to someone posting something about how the IRS was "no good for dragracing". I think it was about 4-5 months ago? Car was like white or silver and had some stock looking (6 spoke 280ZX?) rims. I agree that the the typical reaction of an IRS car would be to squat. Perhaps this guy's setup (pretty sure he's a member here) uses stiff springs and shocks in back? It wasn't exactly doing a wheelstand - more like the fronts were just barely lifted. Quote Link to comment Share on other sites More sharing options...
Andrew Bayley Posted October 23, 2001 Share Posted October 23, 2001 I'm going to try and take a stab at this. Please forgive me if I am way off... Anyway, I once asked this same question to a close friend of mine who seems to know quite a bit about suspension travel and dynamic axle loading. The most basic way I can think to describe this, is to account for differential windup. When major amount of torque is applied to the differential, the front of the pig naturally wants to wind up towards the sky. This is most likely why most Z cars with slicks and/or big power have destroyed the original front differential mount. Not so much because the OEM unit is junk, but more so because of the added upwards force on the differential. Solid axles are submitted to this same force. This is why there are "pinion snubbers" on most solid axle sports cars. The snubber acts as a "bump stop" for the front of the pig. However, once the differential has been torque’d against the snubber, the remaining torque still needs to be transferred somewhere. Since the axle housing is solidly connected to the vehicle, there is a solid firm connection to each side of the frame. Most always, the connection to the frame (i.e. leaf spring, lower control arm, ladder bar, traction bar, etc...) is in front of the rear wheel. Therefore, the windup of the axle is transferred as a force to the frame of the car in a point between the wheels. As more torque is applied to the axle, the force pushing upwards at the point between the wheels becomes greater and greater, until it is strong enough to raise the front wheels off the ground. In an IRS setup, the torque on the differential is isolated from the rear control arms of the Z. The windup of the differential is still presented, but the upward force is significantly greater since the moment arm consist of the short distance between the front and rear mounts and is limited to the differential. Now this is where things got confusing for me, I'll try to do the best to be comprehensible. A side effect of the IRS is a rotational force about the rear wheel that is opposite from that of a solid axle. When torque is applied, the rear control arms want to "roll forward" with the wheel. Since the rear control arms cannot roll with the wheel, the torque of the wheel will cause the control arm to compress towards the cg of the vehicle. In layman’s terms: "squat". Take the front and rear control arm points, and draw a straight line through the two towards the front of the vehicle. This line will fall well below the cg of the vehicle. A simple solution to reduce the rear squat of the Z is to either raise the front mounting point or lower the rear point. Of course, the car will ride for shit... but it wont squat any more. There are other ways to reduce the squat of the Z car and actually reverse the effect on the rear suspension (push the wheels down rather than lifting them). I've been toying around with one particular idea, but I've yet to implement it. It will be exciting to see if it actually works. All theoretical calculations say so, but we all know how things work in the real world (i.e. guess and test). So, could an IRS Z lift its front wheel off the ground? Yes, but it would have to be a pretty large bump in the road -Andy Quote Link to comment Share on other sites More sharing options...
jeromio Posted October 24, 2001 Share Posted October 24, 2001 Well, crap. Maybe I just remembered it wrong. Here's the thread that I was referring to (took forever to find it): http://www.hybridz.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=000590 All the links are broken (which is really unfortunate), but no one says anything like "Holy cow! The wheels are off the ground!" or anything. I remember following those links when they were active and I have this image in my mind of the wheels just barely leaving pavement. But that could just be an exageration of the reality. Anyway, it is definately possible, and as I said, I agree not really likely considering the implementation of most IRSs including that of the Z. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 24, 2001 Share Posted October 24, 2001 Andy, I'm having trouble with the reaction to the torque at the tire. This same torque is at the diff side axles. Since there is a bearing at the hub carrier, I don't see how the control arms come into play. I believe all the reaction to the torque is at the front diff mount and the mustache bar. Since the mustache bar is closer to the halfshaft, I'd think the upward force at the front diff mount is greater than the downward one at the mustache bar attachments. But it's 1 am, I'm probably all messed up on this. Free body diagrams were 15 years ago. Quote Link to comment Share on other sites More sharing options...
Guest Thurem Posted October 24, 2001 Share Posted October 24, 2001 The torque that turns the r. wheels also lifts up the front end, regardless off rear suspension. If you accelerate hard enough to lift the front wheels off the ground, you have transferred all the weight of the car to the rear tires, this is why the rear suspension is compressed. So in the transition from standstill to wheelie the rear suspension is gonna compress. A solid rear axle works against the suspension getting compressed because the front pinion snubber hits the stop and prevents the suspension from compressing. This is why the independent rear suspension is better than a solid rear axle, cause you don't disaable the rear suspension when accelerating (unless your springs are so weak they instantly bottom out), the suspension will still absorb bumps and provide better traction. If you have to do wheelies make an effort to move your center off gravity up and back (ie. motorcycle). Thure Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 24, 2001 Share Posted October 24, 2001 Thurem, I agree. Doesn't matter what kind of suspension. The squat is caused by weight transfer. But then there's the issue of anti-squat geometry. Gotta get those suspension books back out for this one... Quote Link to comment Share on other sites More sharing options...
stony Posted October 24, 2001 Share Posted October 24, 2001 i have the mpeg somewhere on my computer. ive seen it but i dont think it its an irs i think you can even see the pumpkin.... yes i think its a solid axle.... the rear wheels dont camber like a irs does when it squats off the line. even if you could get the irs to lift the wheels i would think over time it would be cheaper to do a solid axle. the diff and axle can not handle the jolt that would lift the tires. my 2 cents stony Quote Link to comment Share on other sites More sharing options...
stony Posted October 24, 2001 Share Posted October 24, 2001 ill email the mpeg to anyone that wants it 1.2 meg Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 25, 2001 Share Posted October 25, 2001 I'd love to see it if you can send it to me, but I got hotmail with it's 1 meg limit, you got aim? I can DL from you quick if you got an ethernet connection. If you got modem, you're better off putting it on a webpage and letting people DL it from there, it'll take less all around time, that's what I'm doing with a z video right now. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted October 25, 2001 Share Posted October 25, 2001 If your talking about the Silver Z in the short video awhile back, I believe that is Jason's Z and it is IRS. He's in the Dallas area. Has recently run high 9's, low 10's. MIke Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 30, 2005 Share Posted March 30, 2005 In any rear wheel drive, regardless of suspension design, the resultant torque during acceleration acts from the rear axle to raise the nose. Resultant torque is the sum of all the different torques that are present in all of the links from flywheel to rear tires. No matter WHAT all those torques are and how many links they go through, and in whatever direction they are, the RESULTANT torque is at the rear axle and acts to lift the nose. "Z squat" is a by-product of the way all the internal torques act on the Z control arms AND from the CG of the car pushing back and down on the rear suspension. IF the CG of the Z is low enough (close to the height of the rear axle), it will not contribute much to front wheel lift force. By squatting, the CG of the car gets even lower and may even have the reverse effect, pushing the front wheels down. Quote Link to comment Share on other sites More sharing options...
johnc Posted March 30, 2005 Share Posted March 30, 2005 IF the CG of the Z is low enough (close to the height of the rear axle), it will not contribute much to front wheel lift force. By squatting, the CG of the car gets even lower and may even have the reverse effect, pushing the front wheels down. Funny, the ROD lifted a front wheel on almost every corner. Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted March 30, 2005 Share Posted March 30, 2005 This is a blast from the past. I know the post stated factory IRS but the responses seemed to venture off to IRS in general. Can a Z (or any car) with IRS lift the front wheels? Yes, because I did it although not with a factory IRS as it could not withstand the "abuse". We are not talking wheelstand here, just enough to get air under the tires. Here is a hi-9 sec GN-powered C4 (IRS I ran) doing it. Look at that awful squat Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 30, 2005 Share Posted March 30, 2005 Funny, the ROD lifted a front wheel on almost every corner. Yeah well we were talking at the drag strip from pure acceleration and rear wheel torque. HEAVY cornering loads mixed with accel loads will change the equation much more. Nice photo! Quote Link to comment Share on other sites More sharing options...
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