I ran 1/4 miles yesterday for the first time, and the best run i did was 15.4 sec. I believe it was due to high heat and humidity, but most of all that stupid wheel-hopping. what causes it, and how can i prevent it?

 

I'm no expert but from what I hear wheel hopping is a direct consequence of bad or improperly adjusted breaks and/or shocks...

 

well, my max had been doing this since brand new.
and my previous car (Probe GT) used to always hop too.

 

You know those liquid filled motor mounts that Nissan shows off? They're built to isolate engine noise and vibration from the cabin?? Those ones that are responsible for why your VQ is so quiet at idle, etc??

They cause wheel hop.

Look at this thread;

http://forums.maxima.org/showthread....hane+AND+motor

DW

 

I read somewhere that the engine mounts are the cause, but didn't believe it, since we are talking about wheel hopping and not engine vibrating.
well, thnx

 

The hop is due to the fact that when you push the engine to the limit the engine mounts are also pushed to their limits. When they hit the limit the engine no longer "rotates" in its mountings and this will cause a little more power to be driven to the wheels resulting in a little of a burn-out. Soon the pressure on the mounts will back off as the wheels spin and this causes enough power to be taken off the wheels resulting in traction again. The cycle starts over and soon again the mounts will hit their max and the wheel will again chirp.

http://www.cattman.com/ Has better engine mounts that apparently get rid of this. I would assume that the mounts are stiffer which would get rid of the wheel hop by causing the wheels to stay in a more controled burn-out.

Hope this answers your question.

Paul

 

what exactly is wheel hop?
is it a loss of traction that makes the wheel spin? i dont understand...
thanks


danny

 

Well in rear wheel drive cars, wheel hop is due to live axles and cheap average road cars being driven at drag strips where they were never designed to be driven.
All sorts of rear suspension mods. need to be made to eliminate wheel hop.
I assume the same is true for front wheel drive cars.
Macferson struts and coil overs are not designed for full throttle launches - family car remember.
Upper and lower A-arm suspensions with stout springs and shocks would help, but these aren't on Nissan cars.

In summary, you wanna drag, get a drag car!

 

The mere fact that it's front wheel drive has quite a bit to do with it. Hard launches in particular transfer weight off the front wheels, which then can spin, and without good shock damping a little chirp-grip-chirp can escalate into a full blown hop.

I think it's mostly a suspension issue, but anything that adds an impact loading (like the engine suddenly coming hard up against the limit of its mounts) serves to aggravate the situation. And probably the shock damping that's been chosen by Nissan for daily driving is all wrong for dragstrip use even before normal shock wear occurs.

Norm

 

Basically, the power of the engine twists the motor mounts beyond their limits, but then what happens PHYSICALLY to the car? Does the front end twist and one tire lifts up allowing it to spin?

At the track as I shifted to second and MASHED the throttle, the car started to shake, the tire(s) squealed, and it felt like the axle was about to fall off. So, I let off the throttle and lost a lot of momentum. I thought it was just the crappy Protenzas losing traction.

Does wheel-hop cause ANY damage? If so, to what parts besides the MOTOR-MOUNTS and any hoses/etc. it twists and stretches?

 

the other guys basically answered the question but I'll add a few tidbits - if you replace all of the suspension rubber bushings and motor and transmission mounts to a solid aluminum or delrin or urethane, you'll reduce the flex. Once you reduce the flex you'll allow the power/torque to be transplated to the ground more efficiently. The problem with solid mounts is that all engine/transmission/road vibrations are transmitted into the vehicle, so you'll get buzzes and vibrations that are annoying for a daily driver.

 

I cant really answer your wheel hop question b/c there are many factors. The tires can also be a problem. I know thw heat could have caused thw shocks/struts to stiffen up and compress less so rather then absorb, it did the opposite.

Just so you know. I was at E-Town that night. I was with Chris91SE. I was the one who had the white 4th gen.

And yes, the heat and numidity killed my runs. Ran 14.4s but couldnt break them.

 

I guess i'll have to consider if eliminating wheel-hop is worth the vibration and noises that i will have to put up with with the new motor mounts??? as of now i dont' think so.
And for all the guys that ask what is wheel-hop, just go into your maxima, and try to peel out.

 

14.4s ??? i'd say that's very good for an auto. what do you have in there? it was nice meeting you man. how often do you go to race? $22 bucks is really not bad. i'd go more often

 

Yea, i can at least hit 14.3 wiht my mods. I have a 99 cali spec auto w/ CAI, y-pipe, and a 50 shot. That is it.

It was nice meeting you as well. Too bad we didnt get to chat. I was too busy icing down the engine. hehe.

I usually go there weds & fri nights. I have been cutting back b/c i dont think i should be sprayin NOS a few times a week.

I'll let ya kow when i head down next.

 

A transverse engine arrangement doesn't generate much chassis twisting (nowhere near the amount that a longitudinal engine causes). The only chassis torsion would come from non-symmetry of the engine mounting points (and possibly some transient torsion due to unequal mount stiffnesses). What happens is that the nose rises in response to the acceleration and that unloads the front tires. Since you don't have even the viscous LSD, the wheel with the lesser grip will spin freely. Lesser grip is a function of static weight and grip coefficient, considering each front tire separately.

About damage. Since each hop represents an impact load, the tire to pavement grip and therefore everything in the drivetrain is also seeing sharp load increases (mitigated somewhat by the springs in your clutch disc). This represents an increased rate of accumulating fatigue damage to everything in the driveline that sees this uneven loading. It doesn't mean that after just a few hops that anything is on the verge of immediate failure, but basically a shorter time to failure is the ultimate result (more hops of greater severity = shorter life than a few mild ones or none at all; among other things, I do fatigue evaluation for a living). The parts that take the worst beating are probably your CV joints, since there is a minute amount of clearance in them that causes a separate impact load when that slack is first taken up in one direction and then in the opposite.

Norm

 

It sure does feel like it could damage something!
With hopping like that, joints, mounts, exhaust anything cold just snap.

 

Thanks Norm.

 

Soft engine mounts cause wheel hop.

 

Wow. I understand everything you wrote! I second that.

 

OK, Norm.

I beefed up the front suspension on my Maxima with stiffer springs/struts and a FSTB. I plan to install Cattman motor mounts, a Cattman/Quaife ATB Differential, and a JWT Stage II clutch. I race with "scrubbed" BFG Drag Radials. Do you believe I'll hop through the first 60' anymore? Or will these mods effectively eliminate the problem forevermore? Please kindly advise. Thank you.

 

Sorry for the slow reaction time (with a T1 connection at work I've never bothered to hook up at home).

Sounds like a plan to me, although since there's a WHOLE lot more to shock damping then just "stiffer", there may well be some experimenting to be done. Don't underestimate the effect of the rear shocks either. They affect how fast the rear squats. Some of the Honda people use some really stiff rear shocks instead of "wheelie bars" (bad term for a FWD car, I know). If the rear suspension were to bottom, you'd get a weight transfer "spike" that would upset traction up front. And I've seen additional (aftermarket) front suspension links that help control compliance steer effects on GM W-bodies (if I can find the pic I'll try to post it); that might help too.

Norm

 

"... bad term for a FWD car, I know ..." Heck, Norm. I do a wheelie every morning in my driveway just backing out of my garage! ;-) Thanks for the insights.

I have stiffer struts/springs in back, too. I inflate the rear tires to 44-psi. I use 15" wheels on the front and 16" wheels on the back to help reduce weight transfer during the launch. The front of my car is certainly lower than the back end by approximately 1".

I wonder about the efficacy of bolt-on sub-frame connectors to tie-up the front-end. These would be custom pieces for a Maxima, I'm sure. If these were widely available, I'm sure they would not be too costly to bolt-on. Oh well... Thanks.

Norm, what can you tell me about the cryogenic tempering process? I'm thinking about giving my tranny the treatment. Your thoughts? Please advise.

 

Sooner or later I'll roll the '01 up onto the ramps or onto a couple of 2 x 10's and look at what's under there and maybe see where there might be some relative motion permitted or where there might be a flexible region. Or a stress concentration. But for now, subframe connectors on a FWD car sound like more of a corner-carver's mod to add some chassis stiffness and facilitate suspension tuning. As far as drag strip performance is concerned, SFC's are useful on domestic front engine / rear drive muscle cars like the Mustang and GM's F-bodies, but the chassis of those cars carries a significant portion of the engine torque reaction back to the rear suspension.

Afraid I can't help much with this one. While I've heard of this treatment I don't know much about how it's supposed to work. Anybody else care to chime in here?

Norm

 

Thanks, Norm. I appreciate your expertise. Take care.