[Mr. 5]

Originally Posted by dzenno

Just got word from DSS that my monster axles have shipped Amazing turnaround time...they received them 11:35AM yesterday, shipped at 5PM a day later...nice...initial turnaround time was 4-5 days...

Invoice states "E92" Bar and CV internal upgrade...FBIS, I guess they have it named E92 because you were in there first with your E92 right? John (ultimateracing335i) did his upgrade there as well but he has an E90 like me...i just checked realoem.com and the axles are the same (same part #) for manual transmissions...i'm assuming this is fine...

Did they fix the broken one or did they reinforce a new one?
This would be an interesting upgrade to us strip folks.

[scrufy]

Originally Posted by shiv@vishnu

I don't know if this is pertinent to the problem but I always found ceramic clutch disks to bite way too abruptly. Which leads to excessive stress downstream in the system. They are great for road racing conditions where they can take a lot of heat and never slip between gears. But going from 0 torque to big torque instantly (at a launch) can shock the rest of the driveline badly. I've got over a hundred max power launches (slicks, 20psi, race+meth) and have yet to break a drivetrain component. Even my orginal clutch lasted 60k miles before slipping in 4th gear. Upgraded with a Spec stg 2 with light flywheel since then. I'm sure a bent/broken axle is somewhere in my future but I think keeping things somewhat pliable (organic disk, flexible drag tires, etc,) has helped a bunch.

Shiv

Shiv, I usually don't agree with a lot you say but your spot on here. Everything from the crank out is multiplied dimensionally all the way through the drivetrain to the axles to the hub
Wheel hop is usually directly related to the length from the frame mounts to the rear end/ axle tubes. The longer the distance there, the more wrap and hop your going to have. With a ceramic clutch, the lockup is even more pronounced... but those things grab so good....The jolt there is directly proportional to how the springs let the axle wrap up. Think of the connection at the rear end from the frame as a pivot point. the more distance you have there, the more leverage the wheels have to twist and bounce. That is how the hot rod guys with leaf springs fix theirs... By using simple traction bars. What they do is limit suspension movement on one side in sudden jolts. I'm sure you've seen those bars that look like helper/overload leafs before. If your really serious into it, a modified panhard bar and different rate springs and modified trailing arms would help. Any racing shop would be able to help set that up for you.
Disclaimer: I'm absolutely the last guy you want to help with a race car set up..it's all new to me..but I have won class in many, many desert races including Baja so I kind of know basic suspension setup stuff...
So if anyone has holes in my explanation as it applies here, I'm more than willing to learn new stuff also...

[techlogik]

Originally Posted by scrufy

Shiv, I usually don't agree with a lot you say but your spot on here. Everything from the crank out is multiplied dimensionally all the way through the drivetrain to the axles to the hub
Wheel hop is usually directly related to the length from the frame mounts to the rear end/ axle tubes. The longer the distance there, the more wrap and hop your going to have. With a ceramic clutch, the lockup is even more pronounced... but those things grab so good....The jolt there is directly proportional to how the springs let the axle wrap up. Think of the connection at the rear end from the frame as a pivot point. the more distance you have there, the more leverage the wheels have to twist and bounce. That is how the hot rod guys with leaf springs fix theirs... By using simple traction bars. What they do is limit suspension movement on one side in sudden jolts. I'm sure you've seen those bars that look like helper/overload leafs before. If your really serious into it, a modified panhard bar and different rate springs and modified trailing arms would help. Any racing shop would be able to help set that up for you.
Disclaimer: I'm absolutely the last guy you want to help with a race car set up..it's all new to me..but I have won class in many, many desert races including Baja so I kind of know basic suspension setup stuff...
So if anyone has holes in my explanation as it applies here, I'm more than willing to learn new stuff also...

Not sure what you are saying is the exact cause of wheel hop.

I was under the impression that:

1) The tire has traction and grip.
2) Force is applied to the tire as it moves forward, the toe of the wheel changes, grip begins to lessen/slip eventually (wheelspin).
3) AS traction is lost during the slipping, the acceleration lessens and toe changes again as it moves back into it's original equilibrium state. Regains grip again.
4) Back to #1. The tire has traction, and grip, force it applied and the toe changes again....repeat.

This is the time wheel hop will occur. The cause of the hop could be bushings/RTABS, drivetrain/indepedent suspension flex etc...that applies force to cause the changing of toe and the repeating "hop".


It literally has to be where the rubber meets the road because the wheel/tire is making contact then the reaction of the suspension/drivetrain as force is applied creates the hopping.

How the toe is being changed might be different depending on the type of suspension, drivetrain and such. That is another thing to determine.

[dzenno]

Originally Posted by Mr. 5

Did they fix the broken one or did they reinforce a new one?
This would be an interesting upgrade to us strip folks.

They took my broken one and the other one that didn't brake (but had a some binding in the CV movement, so it was on its way out soon anyway).. They change almost everything on them (full rebuild) not just the bar but a new inner and outer CV..definitely a MUST for anyone going to the drag strip..otherwise you've got a tow of shame back home in your future

[BrianMN]

dzenno- so you were on street tires when this happened? Isn't that kinda surprising? Were they 'good' street tires that could hook up really well?

[dzenno]

Brian, I was on Mickey Thompson DRs and they hook really well but it seems 335i rear suspension links are the most likely cause of wheel hop (rear guide rods and subframe mounts)

[harry$]

Gentlemen,don't bother swapping out parts,it will do very little to improve the wheel hop. You need to make your self a diff snubber.
This is something you will have to custom make to fit on top of the front of the differential to make for a more ridged set up.

The independent rear suspension is the design flaw.

When horsepower is suddenly delivered to the differential, whether from a clutch or a torque converter, the pinion attempts to "climb" the ring gear. This sudden shock of torque causes the entire rear axle housing to rotate backwards in a counter-clockwise direction. This causes the springs to distort, resulting in severe driveshaft/cv-joint misalignment.

Spring Reaction Unloads Suspension, Causing "Wheel-Hop":

The axle housing is allowed to continue its rotation until it meets resistance from the suspension/springs, which then try to "snap" the housing back to its original position. As power continues to the differential, the housing is once again allowed to rotate back against the springs. This action/reaction of the suspension, commonly known as "wheel hop," continues much like a tug-of-war. Instead of launching your car forward, you sit there bouncing around and spinning your wheels.

As i stated previously,stiffer shocks ,springs and bushings will do very little if anything for wheel hop,


Tires do not cause wheel hop, though they do determine the grip level at which wheel hop occurs.( no slip=no hop / slip=hop) For example, race tires, with their increased grip over street tires, will not break traction until you reach a higher level of acceleration. Some people might think that race tires solved their wheel hop problems, but in truth they merely changed their "wheel hop acceleration threshold" from a level below their launch acceleration to a level above their launch acceleration. Once they increase their horsepower to the point where they can accelerate enough to once again reach that threshold, their wheel hop will return.

Limited-slip differentials will also not prevent wheel hop. They may increase the acceleration threshold at which wheel hop occurs (much like installing race tires), but once again an increase in horsepower will eventually reintroduce the problem.

Ultimately the only real solution would be to switch to the solid Axel with ladder bars or a 4 link suspension as is what some mustang and ac cobra guys eventually do in the end.

[dzenno]

diff/pinion snubber eh? i guess we'll see after I get this stuff installed how it does...might be enough to keep the wheel hop threshold high enough so not to run into it again until hitting some higher HP figure in the future...i guess we'll know soon...any idea how you'd go about making one? I've seen a few pics of them online and they don't look too hard to make but how do we know this'd work with bmw's suspension?

[BrianMN]

There are 2 differential bushings that I think can be upgraded...just nobody has tried it yet.

[harry$]

Originally Posted by dzenno

diff/pinion snubber eh? i guess we'll see after I get this stuff installed how it does...might be enough to keep the wheel hop threshold high enough so not to run into it again until hitting some higher HP figure in the future...i guess we'll know soon...any idea how you'd go about making one? I've seen a few pics of them online and they don't look too hard to make but how do we know this'd work with bmw's suspension?

This diff snubber could be the cheapest part of the parts replacement program and maybe the most effective, maybe try this first,as with all the numerous parts its a guessing game as well,this could be all you need.

[harry$]

Originally Posted by dzenno

I was going to post this in the suspension category but felt it'd get a lot more attention in this section of the board...

A bit of history: Recently had a Wavetrac LSD put in as well as a 6 puck ceramic clutch and lightweight flywheel. These components put additional stress on the rest of the driveline components that haven't been upgraded to stronger components such as rear half shafts (rear drive axles), gearbox, wheel bearings, rear subframe, etc. As some of you already know this past weekend I managed to snap one of my rear half shafts (driver's side one). When I took them off the car I noticed that even the passenger side one was damaged for who knows how long and didn't have smooth movement at the CV joint, it was binding quite a bit.

Car's at the shop right now and half shafts have been sent down for a 1000hp upgrade using chromoly bars by the Driveshaft Shop and they should arrive back next week (4-5 day turnaround once they get them, thanks Former_Boosted_IS for your review, just in time). This is a great upgrade and alternative to purchasing a new OEM set of halfshafts that carry the same risk of breakage as the previous set and I can't wait to get them installed. On top of that I've ordered a few M3 rear suspension bits to firm up rear suspension and plant it better on the ground (M3 rear subframe mounts and an M3 rear wishbone kit) from Tischer...

Currently I've got the KW V2 coilover suspension installed and this is what I had on the car when they broke past weekend. They've been on the car for about 2 years and when they were installed not much attention was paid to detail around their adjustment other than to have the car stanced nice

When my halfshaft snapped it wasn't due to first occurrence wheel hop at that particular moment. I've been experiencing wheel hop every single time I was at the strip but I'd slightly back off throttle every time I felt it. Eventually it took its toll. I can attribute the actual breakage to 3 things:

1) Running 100% UT in 1st gear on Procede instead of 50% as usual creating a massive torque hit in 1st gear. I always used to decrease it to 50-75% before but decided to leave it at 100% this time around.

2) 6 puck ceramic clutch from Clutch Masters that's truly a piece of art and performs amazingly well. This thing will not slip no matter what you do, it'll GRAB and hold without a flinch. With the OEM clutch I am thinking since it was A LOT weaker than this ceramic one it'd allow slippage a lot of times and that way would relieve stress on the rest of the driveline.

3) Relatively weak OEM half shafts...really not meant for racing from a dig or burnouts, obviously

4) Lightweight flywheel from clutch masters...this is a 16lb single mass 2-piece flywheel. I'm extremely happy with its performance when it comes to acceleration in lower gears and really does the job amazingly well. I thought it was giving some vibrations into the rear of the car but I now realize it was because of a bad half shaft (the one that didn't snap, bad CV joint)...Lightweight flywheels provide for faster acceleration mostly in 1st, 2nd and 3rd gears and hp increases due to decreased rotational mass really are felt. I feel that having this flywheel also contributed to a more vicious wheel hop torque hit than what you'd typically encounter with the 38lb OEM dual mass flywheel

Given this situation and the fact that half shaft snapped NOT on launch but maybe 20-30 feet down the track after taking off due to wheel hop I'm looking to you for advice on how can this be addressed properly. I really feel that some form of procedural wheel hop tune-out needs to be done on these cars. Some members on this board may have already addressed this or at least tried to but I couldn't find any comprehensive discussion on the topic or potential ways on how to address it on this platform (other than "maybe" m3 rear suspension parts that I've ordered).

Having stickier tires (slicks or DRs) on the car doesn't "solve" the problem. It just moves the threshold of when wheel hop will occur around. For example, with the same DRs you may experience wheel hop if you launch at 3500rpm but not if you go higher, say launch at 4500rpm. However, you actually may wish to launch lower as you feel that your 60' would potentially be lower. Moving this threshold around with stickier tires or launch RPMs isn't a real solution to wheel hop and I'd really like to avoid discussing that particular item in this thread unless you feel its really relevant.

Shoot your opinions...wheel hop is bad and I really hope it can/should be cured on every car before you launch/take off hard again

EDIT: What happens when you launch like you "should" :
http://www.e90post.com/forums/showthread.php?t=444333

Dzenno, How is this project going,what were the results?

[Cloverdale]

Originally Posted by harry$

Gentlemen,don't bother swapping out parts,it will do very little to improve the wheel hop. You need to make your self a diff snubber.
This is something you will have to custom make to fit on top of the front of the differential to make for a more ridged set up.

The independent rear suspension is the design flaw.

When horsepower is suddenly delivered to the differential, whether from a clutch or a torque converter, the pinion attempts to "climb" the ring gear. This sudden shock of torque causes the entire rear axle housing to rotate backwards in a counter-clockwise direction. This causes the springs to distort, resulting in severe driveshaft/cv-joint misalignment.

Spring Reaction Unloads Suspension, Causing "Wheel-Hop":

The axle housing is allowed to continue its rotation until it meets resistance from the suspension/springs, which then try to "snap" the housing back to its original position. As power continues to the differential, the housing is once again allowed to rotate back against the springs. This action/reaction of the suspension, commonly known as "wheel hop," continues much like a tug-of-war. Instead of launching your car forward, you sit there bouncing around and spinning your wheels.

As i stated previously,stiffer shocks ,springs and bushings will do very little if anything for wheel hop,


Tires do not cause wheel hop, though they do determine the grip level at which wheel hop occurs.( no slip=no hop / slip=hop) For example, race tires, with their increased grip over street tires, will not break traction until you reach a higher level of acceleration. Some people might think that race tires solved their wheel hop problems, but in truth they merely changed their "wheel hop acceleration threshold" from a level below their launch acceleration to a level above their launch acceleration. Once they increase their horsepower to the point where they can accelerate enough to once again reach that threshold, their wheel hop will return.

Limited-slip differentials will also not prevent wheel hop. They may increase the acceleration threshold at which wheel hop occurs (much like installing race tires), but once again an increase in horsepower will eventually reintroduce the problem.

Ultimately the only real solution would be to switch to the solid Axel with ladder bars or a 4 link suspension as is what some mustang and ac cobra guys eventually do in the end.

My experience in failing to eliminate wheel hop in a 370z leaves me in agreement with what's been stated here (experienced in an AT and Manual). I now have 2 335's, wheel hop in the manual, but no wheel hop in the auto for reason's unknown.

[iqraceworks]

It might have already been mentioned....but start buy swapping out your old and worn subframe bushings. I'm running the Whiteline hard poly subframe bushings, and I have NO wheelhop with street type radials on the road. If they spin...they just spin. I'm probably putting down low/mid 400hp to the rear tires.

It's amazing much move subframe movement you get when the bushings are all worn out....the entire diff and rear suspension just walk all over the place.