Stock axles, 2nd gear launch at the drag strip

[Hammerhead13579]

I searched for a while and couldn't find a definitive answer. I know people have broken axles while stock and definitely on stage 2 - but has anyone had an issue with 2nd gear launches at the drag strip with stage 2? Looking at the gear ratios I would imagine it's quite a bit safer vs 1st gear launches.

I know there are a ton of factors so I could be perfectly fine even if others have had issues - I just wanted to get some more information about the conditions that caused the failures (if there have been any)...like tire pressure, how good the prep was, what RPM was used to launch, what tire & sidewall, etc. My track has excellent prep but I haven't run this vehicle yet.

Details:
Stage 2 BM3 E50 OTS
Xhp stage 2 with start in 2nd gear enabled
Drag radials

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[jmikes]

Supposedly some people have snapped them on the streets with E50 tunes and semi-slicks, but most confirmed instances have been at the drag strip and often with radials. I'd imagine that if they're going as far as to buy radials and E-blend, then a lot of those people who broke their axles are smart enough to know that launching in 2nd is better than 1st at the drag strip, but others will know better than me.

 

[olivia_49]

Second gear launches usually put less stress on the axles than first, so you’re probably in a safer spot, especially with good track prep and proper tire pressure. Still, things like RPM, sidewall, and how aggressive you are off the line can make a difference, but with drag radials and careful launches, it should be fine.

 

[MisterSkiz]

LOL - get new axles dude or you will be either changing them on the side of the track covered in sticky gear oil, or on the street where you will be having a tow truck coming to destroy your front end as it drags it up the back of the truck.

 

[M340Manny]

Ik im not contributing what's so ever here, but are supra axles that much weaker then the M340 axles. OR does it come down to the (My) M340 being awd.

 

[Hammerhead13579]

Ik im not contributing what's so ever here, but are supra axles that much weaker then the M340 axles. OR does it come down to the (My) M340 being awd.

Not sure. But I think it's one of those things that becomes overblown because people hear the horror stories. People said this stuff in the mustang forum and I ran my 700whp car at the drag strip a bunch of times with no issue. My wife even botched a burn out in the water box and then at the line launched at 2k RPMs and squealed the tires for 30 feet before letting off.
Also, my vehicle is actually a Z4 M40i but I'm pretty sure all the axles are the same.

 

[jmikes]

Not sure. But I think it's one of those things that becomes overblown because people hear the horror stories. People said this stuff in the mustang forum and I ran my 700whp car at the drag strip a bunch of times with no issue. My wife even botched a burn out in the water box and then at the line launched at 2k RPMs and squealed the tires for 30 feet before letting off.
Also, my vehicle is actually a Z4 M40i but I'm pretty sure all the axles are the same.

Surviving (and a little luck) doesn't necessarily mean it's actually safe.

Same thing as how some VQ37 owners manage to push 700+ WHP no problem on the stock block and transmission for years without issues, even though the commonly agreed "safe" power/torque limits for the engine and transmissions are in the 400-500 range.

 

[Hammerhead13579]

Surviving (and a little luck) doesn't necessarily mean it's actually safe.

It also doesn't mean it's not safe....

This also doesn't compare at all to modified engine power. We are talking about axles here. And if everybody always listened to post #4 - who thinks there is absolutely zero possibility of successfully running the car without breaking the axles - then how do we know everyone isn't wasting their money? There are so many variables that nobody can even give a percent chance of failure....but even it's it's 50% chance...I could still run my car 10 times and it's possible nothing bad will happen.

I know for a fact that lots of people have upgraded their turbos and not upgraded their axles...and those axles never broke...

Lots of mustangs that broke their axles at the drag strip were manual or they were trying to use 2-step launch control or they were using street tires instead of hot soft radials...

All of the Supra's that had a failure had a root cause for the failure. That's how life works. What does the science tell us? Vibration from wheel hop? Too much torque with no slip? Too much torque from too high of RPM at launch? Were they in 1st gear or 2nd gear? What tune were they running? Did they have other mods like suspension? What mode was the car in for handling/suspension? What wheel/tire setup was used?

Again...so many variables...

 

[razorlab]

The biggest variable is the driver.

The driver that stays in it with wheel hop, knockCEL flashing, engine temp warning light blaring and just keeps going and launches 20x a day = things break every time

The driver that has brain cells combined with mechanical sympathy, and lets out of it at the slightest hint of wheel hop, keeps an eagle eye on gauges and knows the importance of cool downs = much less possible issues.

Having been a tuner for 20+ years... A lot of people are absolute morons with zero care/clue.

 

[Hammerhead13579]

The biggest variable is the driver.

The driver that stays in it with wheel hop...

...keeps an eagle eye on gauges...

Welcome King Razorlab.

I have to disagree that the driver is the biggest variable. It is certainly one of the variables but I don't think it's a very significant variable.

Reason 1: This is a mechanical failure. 100% caused by force and stress. You can put any driver in the vehicle and it wouldn't change the force and stress that the axle sees before it fails.
Reason 2: You only talked about a specific scenario when an axle might break - during wheel hop. I haven't personally broken an axle but the many videos I have seen at the drag strip the vehicle barely moves because it happens almost instantaneously upon takeoff. On the street - sure this is more of a factor. But I plan to race my vehicle at the drag strip with full prep. After a proper burnout with proper tire pressures there shouldn't be any wheel hop.
Reason 3: Talking again about the drag strip - my eyes are on the tach, the tree, and then on the track in front of me. There are no special gauges I am monitoring that will indicate that I am about to break an axle if I'm about to attempt to launch with all 550 ftlbs of torque to the rear wheels that are "glued" to the track surface.

 

[M340Manny]

Welcome King Razorlab.

I have to disagree that the driver is the biggest variable. It is certainly one of the variables but I don't think it's a very significant variable.

Reason 1: This is a mechanical failure. 100% caused by force and stress. You can put any driver in the vehicle and it wouldn't change the force and stress that the axle sees before it fails.
Reason 2: You only talked about a specific scenario when an axle might break - during wheel hop. I haven't personally broken an axle but the many videos I have seen at the drag strip the vehicle barely moves because it happens almost instantaneously upon takeoff. On the street - sure this is more of a factor. But I plan to race my vehicle at the drag strip with full prep. After a proper burnout with proper tire pressures there shouldn't be any wheel hop.
Reason 3: Talking again about the drag strip - my eyes are on the tach, the tree, and then on the track in front of me. There are no special gauges I am monitoring that will indicate that I am about to break an axle if I'm about to attempt to launch with all 550 ftlbs of torque to the rear wheels that are "glued" to the track surface.

I say you wont break an axle. You simply don't make enough power too. Just be mindful of wheel hop.

 

[razorlab]

Welcome King Razorlab.

I have to disagree that the driver is the biggest variable. It is certainly one of the variables but I don't think it's a very significant variable.

Reason 1: This is a mechanical failure. 100% caused by force and stress. You can put any driver in the vehicle and it wouldn't change the force and stress that the axle sees before it fails.
Reason 2: You only talked about a specific scenario when an axle might break - during wheel hop. I haven't personally broken an axle but the many videos I have seen at the drag strip the vehicle barely moves because it happens almost instantaneously upon takeoff. On the street - sure this is more of a factor. But I plan to race my vehicle at the drag strip with full prep. After a proper burnout with proper tire pressures there shouldn't be any wheel hop.
Reason 3: Talking again about the drag strip - my eyes are on the tach, the tree, and then on the track in front of me. There are no special gauges I am monitoring that will indicate that I am about to break an axle if I'm about to attempt to launch with all 550 ftlbs of torque to the rear wheels that are "glued" to the track surface.

I forgot to mention in my post that the other biggest variable is I personally have zero interest in car bowling so I was coming from a normal out-on-the-street point of view.

The actual sentiment of my post seems to have gone over your head though. It's all good.

 

[i3igpete]

At the end of the day it's all statistics. One guy could launch all day on drag pack and be fine, another unlucky guy will snap his axles the first time he wheel hops. Could be totally out of his control, a bad grain boundary or inclusion/porosity in the shaft. If you don't want to break an axle (or more precisely, you want to have a smaller chance of breaking) then get the upgrade.

That being said, you won't find much information on second gear launches versus first gear launches, because second gear launch is already the generally recommended method.

 

[MisterSkiz]

Ik im not contributing what's so ever here, but are supra axles that much weaker then the M340 axles. OR does it come down to the (My) M340 being awd.

Apparently totally different parts, not shared between platforms - click "Vehicle Fitment"

https://www.bmwpartsnow.com/oem-parts/bmw-2022-2024-bmw-z4-cv-axle-assembly-33205a74ac8

https://bmw.oempartsonline.com/oem-parts/bmw-axle-assembly-33205a74ac3

 

[Hammerhead13579]

Apparently totally different parts, not shared between platforms - click "Vehicle Fitment"

https://www.bmwpartsnow.com/oem-parts/bmw-2022-2024-bmw-z4-cv-axle-assembly-33205a74ac8

https://bmw.oempartsonline.com/oem-parts/bmw-axle-assembly-33205a74ac3

Interesting. It seems to related to power and weight of the vehicle but then the B58 Z4 has the same axles as the B48 Z4, 3 and 4-series. Do all automatic Supra's have the same axles regardless of engine? If they using BMW parts it would seem the answer is yes.

So the 340i and 440i's quite possibly do have stronger axles...they have the same axles as the M2.

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