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    • HPF M3 loses control at the strip

      We just received these videos of an HPF turbo M3 which lost control at the Irwindale 1/8 mile strip and ended up going into the wall. The car looks like it is running bias-ply slicks with radial street tires up front. This may have contributed to the driver losing control as the general rule is not to mix due to instability up top. Additionally, once the car starts to sway it looks like the owner stays in it and then tried to brake too late which causes him to lose it. Hopefully we will have more details on the car and the setup soon.





      This article was originally published in forum thread: HPF M3 loses control at the strip started by Sticky View original post
      Comments 195 Comments
      1. gringotegra's Avatar
        gringotegra -
        If he ran a true slick, he should have extended studs on the rear... they are required if you run a true slick... some people go and pass tech on street tires then change them out for slicks later on... i never had studs on my car and thats what i would do... there are no rules that i know of that require you to have matching tires....

        Now onto the tire part, ive never seen or had an issue running miss-matched tires... now its a little different for me being FWD, but i have plenty of friends with supras/RX-7's/RWD V8 cars that run slicks in the back and regular street tires in the front and dont have a problem... The Slicks + regular street tire is not the issue here..

        Looking at the video again, it looks like it was pretty cold there.. everyone is wearing warm looking cloths, when track temp gets to 40-50 deg, that VHT/Rubber thats on the track gets SLICK as hell....

        Driver stayed on the gas longer than he should have, and lost control.. nothing to do with the tires being miss matched... the track being cold didnt help his traction either..
      1. PEI330Ci's Avatar
        PEI330Ci -
        Click here to enlarge Originally Posted by nickr519 Click here to enlarge
        While your patronizing tone just reeks of elitism, I'll bite anyway. I must comment, yes I'm an electrical engineering student but I couldn't be f*cked to have any idea how a differential works, you got me bud Click here to enlarge Who elevated the diff as a factor above all else? Chris clearly stated in the post on e46F that the the tire mix was a no no, and added that the differential may have been a factor as well. Again with "the factor" you write like this incident was caused by one factor, and you seem to be implying all differentials behave in exactly the same way under load, both of which I'm sure you know better than. Certainly driver error and a poor setup were large factors at play, but you're smarter than that. Even if you do come off as a bit of a dick Click here to enlarge

        Anywho, I did not know that you could pass tech inspection with that tire combination. While you're certainly taking your own safety into your own hands, as was seen by the relatively close call in the video the safety of the other parties involved are also at stake, isn't that kind of the fundamental idea behind tech inspection? Click here to enlarge
        I didn't see anything wrong with Sticky's post.
      1. 930chas's Avatar
        930chas -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        No one is claiming anything along the lines of it being only one factor simply that elevating the diff above all others is stupid, because it is.

        If you drag race frequently or even know how a diff works you realize the diff was not the factor here. Let's not confuse a diff sales pitch with what the major factors really were.
        Amen to this.
      1. PEI330Ci's Avatar
        PEI330Ci -
        Click here to enlarge Originally Posted by gringotegra Click here to enlarge
        If he ran a true slick, he should have extended studs on the rear... they are required if you run a true slick... some people go and pass tech on street tires then change them out for slicks later on... i never had studs on my car and thats what i would do... there are no rules that i know of that require you to have matching tires....

        Now onto the tire part, ive never seen or had an issue running miss-matched tires... now its a little different for me being FWD, but i have plenty of friends with supras/RX-7's/RWD V8 cars that run slicks in the back and regular street tires in the front and dont have a problem... The Slicks + regular street tire is not the issue here..

        Looking at the video again, it looks like it was pretty cold there.. everyone is wearing warm looking cloths, when track temp gets to 40-50 deg, that VHT/Rubber thats on the track gets SLICK as hell....

        Driver stayed on the gas longer than he should have, and lost control.. nothing to do with the tires being miss matched... the track being cold didnt help his traction either..
        Correct on the studs being required, as is a driveshaft loop with slicks.

        Also, that track is known for requiring a roll bar over 90mph in the 1/8th....which the car was capable of.

        I ran a mixed setup for years, but it wasn't that simple. I ran a 26" slick with a wider rim width so that the sidewall tappered inwards. This creates stability. Secondly, I did a lot of test runs with varying tire pressure to figure out the slick. By test runs, I'm talking about up to 30mph or so. I didn't just jump into the car and run 100mph. I also ran more toe on the front and rear of the car to keep it stable. It might have cost me a little bit in ET, but I think it was worth it. The car was pretty solid down the 1/8 mile, but the back end would move around a tiny bit on the top end in the 1/4. The trick was to just let it move around, and not try to correct. You can get the same thing happening with bias ply on both ends of the car, and if you aren't used to it, you can steer yourself into a wall.

        Now...would recommend a mixed setup? Nope. The next wheel setup I run for racing will be bias ply on both the front and rear.
      1. GG///M3's Avatar
        GG///M3 -
        Click here to enlarge Originally Posted by PEI330Ci Click here to enlarge
        I didn't see anything wrong with Sticky's post.
        +1
      1. gringotegra's Avatar
        gringotegra -
        Click here to enlarge Originally Posted by PEI330Ci Click here to enlarge
        Correct on the studs being required, as is a driveshaft loop with slicks.

        Also, that track is known for requiring a roll bar over 90mph in the 1/8th....which the car was capable of.

        I ran a mixed setup for years, but it wasn't that simple. I ran a 26" slick with a wider rim width so that the sidewall tappered inwards. This creates stability. Secondly, I did a lot of test runs with varying tire pressure to figure out the slick. By test runs, I'm talking about up to 30mph or so. I didn't just jump into the car and run 100mph. I also ran more toe on the front and rear of the car to keep it stable. It might have cost me a little bit in ET, but I think it was worth it. The car was pretty solid down the 1/8 mile, but the back end would move around a tiny bit on the top end in the 1/4. The trick was to just let it move around, and not try to correct. You can get the same thing happening with bias ply on both ends of the car, and if you aren't used to it, you can steer yourself into a wall.

        Now...would recommend a mixed setup? Nope. The next wheel setup I run for racing will be bias ply on both the front and rear.

        Roll bar @ 90mph? wierd... my local track is strict as hell on the roll bar rule... i went 11.48@126 a few years ago and they said no more lol.. the rule is faster than 11.49 and you need a roll bar... i consistently trap 101-103mph in the 1/8 on street tires and they never say anything but every track is different...

        I was the same, first time i ran slicks i started them at like 15psi lol.... us FWD guys normally run them at 6.5-7psi (i know pretty much flat but it works).... i have driven a few rwd slick cars down the track along with my car and they do tend to walk around a bit up top but its nothing serious.
      1. nickr519's Avatar
        nickr519 -
        Click here to enlarge Originally Posted by gringotegra Click here to enlarge
        If he ran a true slick, he should have extended studs on the rear... they are required if you run a true slick... some people go and pass tech on street tires then change them out for slicks later on... i never had studs on my car and thats what i would do... there are no rules that i know of that require you to have matching tires....

        Now onto the tire part, ive never seen or had an issue running miss-matched tires... now its a little different for me being FWD, but i have plenty of friends with supras/RX-7's/RWD V8 cars that run slicks in the back and regular street tires in the front and dont have a problem... The Slicks + regular street tire is not the issue here..

        Looking at the video again, it looks like it was pretty cold there.. everyone is wearing warm looking cloths, when track temp gets to 40-50 deg, that VHT/Rubber thats on the track gets SLICK as hell....

        Driver stayed on the gas longer than he should have, and lost control.. nothing to do with the tires being miss matched... the track being cold didnt help his traction either..
        Interesting insight gringo ...

        I certainly don't drag race frequently as it doesn't appeal to me whatsoever, but I do appreciate it as a form of comparing cars to some extent.
        And there's nothing "wrong" with sticky's post (whatever that means), but the tone he posted in reveals his usual patronizing holier-than-thou attitude which pervades the bmw modding community in general, it's really not rocket science ... bmw forums, whether bb, e46, m3f, could all benefit from their members stepping off of their high horse every so often. I mean seriously, is that how you talk to your buddies sticky? "I don't know if you know understand a diff works," lol do your IRL buddies enjoy condescending comments like that?

        PEI While I don't necessarily agree you and Sticky are certainly far more knowledgable about bmw's with respect to drag racing than myself. My comments were made out of generality.

        930chas while Chris is definitely a businessman, at least here "major factor" recognizes that there's not just 1 (lol) which is what made me Click here to enlarge in the first place
      1. ZooyorQ's Avatar
        ZooyorQ -
        I personally think that when you're dealing with 600-700hp and up there are ALOT of things that could be the factor. Could it have been possible that a spline shredded in one of his half axles causing it to go? I don't know.. but there's no disputing radial+bias == bad idea for the inexperienced. Ultimately the crash was driver error which is evident when you watch his reaction time at the tree and his braking during the skid.. I raced shifty karts for many years and while they have no suspension so you don't have to deal with loading/unloading its still a similar concept.. you never want to do anything 'drastic' while losing control .. aka braking or over correcting/etc.. you'll end up typically doing a tank slapper and hitting the grass/wall.

        I have heard of many people saying that driving on the freeway with a mix causes the car to sway and change lanes even when not under a load or causes vibration.

        Oh and its very discerning to hear of individuals dropping so much money on these cars then having to ask what the difference between a radial and a bias is, or suggesting that it was the diff, etc. Very common knowledge for most people.. even myself and I'm by far no car expert.

        Some of these HPF m3's need driver mods, not diffs or slicks.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by nickr519 Click here to enlarge
        Again with "the factor" you write like this incident was caused by one factor, and you seem to be implying all differentials behave in exactly the same way under load, both of which I'm sure you know better than. Certainly driver error and a poor setup were large factors at play, but you're smarter than that. Even if you do come off as a bit of a dick
        No, it does not sound like I am saying the incident was caused by one factor, quoted for reference:

        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        No one is claiming anything along the lines of it being only one factor simply that elevating the diff above all others is stupid, because it is.
        Fairly simple, right? Not trying to be elitist but you also come in acting if the diff "could be" a factor. Yes, and some sand that happened to blow onto the track could have been a factor, a prior oil spill, lack of VHT, etc. Plenty of could be's and could have factored in's but we have concrete info to go on. I don't see why any kind of different diff would made a difference here, sorry.

        Click here to enlarge Originally Posted by nickr519 Click here to enlarge
        Anywho, I did not know that you could pass tech inspection with that tire combination. While you're certainly taking your own safety into your own hands, as was seen by the relatively close call in the video the safety of the other parties involved are also at stake, isn't that kind of the fundamental idea behind tech inspection?
        The tech inspection is a basic inspection to make sure the car is mechanically sound as well as checking for basic safety. There is no way to be 100% accident proof. However, risks can be minimized but ultimately it is the responsibility of the owner for their own safety.

        A tech inspection checks to see if nitrous lines are properly setup, a driveshaft loop, cage, fuel cell, etc. You will notice, all of these things are checked for in the event of an accident, not to prevent one. Tire tread is checked, making sure no fluids leak, etc, but if someone is running a bias-ply made for the strip in back they are well within the rules. It is not a 100% guarantee mixing them will result in an accident. If it was me, I would go so far as to say you run all bias-ply or you do not run. Some guys would not like that though, just like some guys don't like having to have a cage.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by nickr519 Click here to enlarge
        but the tone he posted in reveals his usual patronizing holier-than-thou attitude which pervades the bmw modding community in general, it's really not rocket science ... bmw forums, whether bb, e46, m3f, could all benefit from their members stepping off of their high horse every so often. I mean seriously, is that how you talk to your buddies sticky? "I don't know if you know understand a diff works," lol do your IRL buddies enjoy condescending comments like that?
        If my buddies say something like that, sure, I tell them exactly what I think. I'm their buddy, no point in pulling punches.

        You are also a bit new around here, I think you will find this is the most down to earth BMW forum in existence. I think I was pretty mild but if you were offended, my apologies. Don't expect a politically correct atmosphere though...
      1. Funkboy316's Avatar
        Funkboy316 -
        Click here to enlarge Originally Posted by ZooyorQ Click here to enlarge
        I personally think that when you're dealing with 600-700hp and up there are ALOT of things that could be the factor. Could it have been possible that a spline shredded in one of his half axles causing it to go? I don't know.. but there's no disputing radial+bias == bad idea for the inexperienced. Ultimately the crash was driver error which is evident when you watch his reaction time at the tree and his braking during the skid.. I raced shifty karts for many years and while they have no suspension so you don't have to deal with loading/unloading its still a similar concept.. you never want to do anything 'drastic' while losing control .. aka braking or over correcting/etc.. you'll end up typically doing a tank slapper and hitting the grass/wall.

        I have heard of many people saying that driving on the freeway with a mix causes the car to sway and change lanes even when not under a load or causes vibration.

        Oh and its very discerning to hear of individuals dropping so much money on these cars then having to ask what the difference between a radial and a bias is, or suggesting that it was the diff, etc. Very common knowledge for most people.. even myself and I'm by far no car expert.

        Some of these HPF m3's need driver mods, not diffs or slicks.
        guess i should sell my car as well then, cause i didnt know the difference either. and dont care to run the strip for the most part. most ppl that modify these cars are doing so for the street where a bias ply would never be needed it seems. so your logic is kind of screwy anyway.
      1. nickr519's Avatar
        nickr519 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        No, it does not sound like I am saying the incident was caused by one factor, quoted for reference:



        Fairly simple, right? Not trying to be elitist but you also come in acting if the diff "could be" a factor. Yes, and some sand that happened to blow onto the track could have been a factor, a prior oil spill, lack of VHT, etc. Plenty of could be's and could have factored in's but we have concrete info to go on. I don't see why any kind of different diff would made a difference here, sorry.



        The tech inspection is a basic inspection to make sure the car is mechanically sound as well as checking for basic safety. There is no way to be 100% accident proof. However, risks can be minimized but ultimately it is the responsibility of the owner for their own safety.

        A tech inspection checks to see if nitrous lines are properly setup, a driveshaft loop, cage, fuel cell, etc. You will notice, all of these things are checked for in the event of an accident, not to prevent one. Tire tread is checked, making sure no fluids leak, etc, but if someone is running a bias-ply made for the strip in back they are well within the rules. It is not a 100% guarantee mixing them will result in an accident. If it was me, I would go so far as to say you run all bias-ply or you do not run. Some guys would not like that though, just like some guys don't like having to have a cage.
        fair enough. not really convinced about the diff. it was the "the factor" not the above quote that threw me ftr. good to know about tech inspection in case I ever decide to run my 300, i really dont think I will though. For some reason I enjoy throwing it into some turns on a mountain road a lot more
      1. ZooyorQ's Avatar
        ZooyorQ -
        Click here to enlarge Originally Posted by Funkboy316 Click here to enlarge
        guess i should sell my car as well then, cause i didnt know the difference either. and dont care to run the strip for the most part. most ppl that modify these cars are doing so for the street where a bias ply would never be needed it seems. so your logic is kind of screwy anyway.
        You're smart enough not to put it on the strip.. that's all that matters. I'm saying there are people who i've seen stating they can't wait to put it on the strip, they've invested tens of thousands into their cars yet don't know some of the more basic principals of drag racing.

        Bias Ply vs Radial.. Bias is an older tire manufacturing method and if I'm not mistaken is still not uncommon on many cars in other countries. Bias Ply is not made strictly for drag racing and I think (and I could be completely wrong here) Nascar ran Bias until about 1990.

        Although I'm pretty sure now days bias ply tires are strictly for old hot rods (authentic look/etc) and drag racing as radials are far superior on the road and provide more predictable handling.

        I'm simply saying if you're going to take your $70k dollar car onto the strip you should atleast invest 15 minutes reading a few articles on the basic principals behind drag racing.. most would probably cover tire/suspension setup and within that would probably be a mention of bias ply vs radial.

        Not trying to insult you or any other HPF owners (including myself.... ) but some of the HPF owners simply send their cars out for the $40k package deal and then immediately think they're Mario Andretti on the circuit and John Force on the strip.
      1. spdu4ea's Avatar
        spdu4ea -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        This issue was not one created by the diff. Nor would a different diff save him, he already had an LSD and really an open diff once pretty much works the same way on the strip once it has traction.
        An OS Giken would not have saved him once he started to lose it, but there is a decent chance it would have prevented him from getting so squirrelly in the first place. And differentials do not all work the same:


        An open diff transfers torque to the path of least resistance. Once 1 tire starts spinning, more torque goes to that spinning tire. The car remains relatively stable -- aided in large part by 1 rear tire maintaining traction.

        The M3's "Variable M" diff is an odd duck -- but basically when 1 wheel starts spinning fluid pressure builds up, activating the opposing clutch packs to divert torque to the slower-spinning wheel. Whereas a typical gear-type torque sensing diff might be able to split 75% torque to 1 wheel, 25% to the other, the M variable is capable of delivering 100% torque to one side. That sounds great in theory, but in practice there is quite a bit of lag when pressure is building up. Combine that lag with 3x more power than was calibrated for the unit, and you've got a recipe for some instability: right rear starts spinning fast enough to activate 100% torque for the left rear, which, thanks to the shear pump's lag, then spins fast enough to activate 100% torque for the right rear. During this time, each wheel assembly is toeing-in under load and toeing-out when torque is diverted back away causing the back end to start wandering around. Add a novice driver combined with an unstable tire setup and you've got a recipe for disaster.

        A clutch-type diff locks based on the torque being passed through the differential -- regardless of whether one side is spinning faster than the other. Once you put the required amount of torque through the rear end, the axle locks. Since both wheels are rotating the same speed the toe-in under loading is equalized (provided both tires have roughly same available traction) -- so even when the back end loses complete traction the chassis isn't giving the back end a reason to wander.


        That said, there are still external reasons to wander (grooves/crowning in the pavement, uneven traction traction on one side of the lane vs the other) so it is important for the driver to know how to deal with it.
      1. ccsykes's Avatar
        ccsykes -
        Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
        That said, there are still external reasons to wander (grooves/crowning in the pavement, uneven traction traction on one side of the lane vs the other) so it is important for the driver to know how to deal with it.
        When I bracket raced, I didn't get a good stable run until I switched to a spool. Even with skinny's it was a wobbly ride. Almost like riding in a boat. So I could imagine what 700+ HP on bias bly slicks would be like through an OEM diff..

        Bottom line though, the slick/radial combo was to blame.
      1. DBFIU's Avatar
        DBFIU -
        I just watched the video for the first time.

        After looking closely it's really hard to tell what caused this. I will tell you what could have prevented it though.

        The driver took forever brake. He didn't let off when he should have, as soon as the car began to sway; you need to let off and regain control. I don't know why he stayed on the throttle as long as he did.

        Second, why the long ass burnout? Slicks only need a couple seconds to heat up. I think he was a little too riled up and just trying to show off... Which leads me to believe the "not letting off attitude" of my first point as to what really caused this accident.

        Most accidents are caused by people, not machines.

        I'm sure the tire combo didn't help; but I have seen a ton of people run strange tire combos on a variety of cars. That's not to say it's 100% tire combo, and 0% his fault. But somewhere in between.
      1. nickr519's Avatar
        nickr519 -
        Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
        An OS Giken would not have saved him once he started to lose it, but there is a decent chance it would have prevented him from getting so squirrelly in the first place. And differentials do not all work the same:


        An open diff transfers torque to the path of least resistance. Once 1 tire starts spinning, more torque goes to that spinning tire. The car remains relatively stable -- aided in large part by 1 rear tire maintaining traction.

        The M3's "Variable M" diff is an odd duck -- but basically when 1 wheel starts spinning fluid pressure builds up, activating the opposing clutch packs to divert torque to the slower-spinning wheel. Whereas a typical gear-type torque sensing diff might be able to split 75% torque to 1 wheel, 25% to the other, the M variable is capable of delivering 100% torque to one side. That sounds great in theory, but in practice there is quite a bit of lag when pressure is building up. Combine that lag with 3x more power than was calibrated for the unit, and you've got a recipe for some instability: right rear starts spinning fast enough to activate 100% torque for the left rear, which, thanks to the shear pump's lag, then spins fast enough to activate 100% torque for the right rear. During this time, each wheel assembly is toeing-in under load and toeing-out when torque is diverted back away causing the back end to start wandering around. Add a novice driver combined with an unstable tire setup and you've got a recipe for disaster.

        A clutch-type diff locks based on the torque being passed through the differential -- regardless of whether one side is spinning faster than the other. Once you put the required amount of torque through the rear end, the axle locks. Since both wheels are rotating the same speed the toe-in under loading is equalized (provided both tires have roughly same available traction) -- so even when the back end loses complete traction the chassis isn't giving the back end a reason to wander.


        That said, there are still external reasons to wander (grooves/crowning in the pavement, uneven traction traction on one side of the lane vs the other) so it is important for the driver to know how to deal with it.
        Click here to enlarge
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
        An OS Giken would not have saved him once he started to lose it, but there is a decent chance it would have prevented him from getting so squirrelly in the first place. And differentials do not all work the same:


        An open diff transfers torque to the path of least resistance. Once 1 tire starts spinning, more torque goes to that spinning tire. The car remains relatively stable -- aided in large part by 1 rear tire maintaining traction.

        The M3's "Variable M" diff is an odd duck -- but basically when 1 wheel starts spinning fluid pressure builds up, activating the opposing clutch packs to divert torque to the slower-spinning wheel. Whereas a typical gear-type torque sensing diff might be able to split 75% torque to 1 wheel, 25% to the other, the M variable is capable of delivering 100% torque to one side. That sounds great in theory, but in practice there is quite a bit of lag when pressure is building up. Combine that lag with 3x more power than was calibrated for the unit, and you've got a recipe for some instability: right rear starts spinning fast enough to activate 100% torque for the left rear, which, thanks to the shear pump's lag, then spins fast enough to activate 100% torque for the right rear. During this time, each wheel assembly is toeing-in under load and toeing-out when torque is diverted back away causing the back end to start wandering around. Add a novice driver combined with an unstable tire setup and you've got a recipe for disaster.

        A clutch-type diff locks based on the torque being passed through the differential -- regardless of whether one side is spinning faster than the other. Once you put the required amount of torque through the rear end, the axle locks. Since both wheels are rotating the same speed the toe-in under loading is equalized (provided both tires have roughly same available traction) -- so even when the back end loses complete traction the chassis isn't giving the back end a reason to wander.


        That said, there are still external reasons to wander (grooves/crowning in the pavement, uneven traction traction on one side of the lane vs the other) so it is important for the driver to know how to deal with it.
        Sorry but part of this is incorrect, an open diff applies the same torque to both wheels at all times. Each wheel does not get different amounts.

        He is already running a limited slip. An OS Gilken is an LSD just with with different locking characteristics. I don't see this making any difference from him already running an M diff on the strip. On the roadcourse or in poor weather? Sure.
      1. Sticky's Avatar
        Sticky -
        Something you guys need to understand about a Limited Slip, which he was already running:

        This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches. Some of these have a cone clutch that is just like the synchronizers in a manual transmission.

        The spring pack pushes the side gears against the clutches, which are attached to the cage. Both side gears spin with the cage when both wheels are moving at the same speed, and the clutches aren't really needed -- the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn.
        A different LSD would not have saved him from a poor setup and driver error, it is a moot point.
      1. GG///M3's Avatar
        GG///M3 -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        Something you guys need to understand about a Limited Slip, which he was already running:



        A different LSD would not have saved him from a poor setup and driver error, it is a moot point.
        Some can't understand this fact, and thats the sad part.