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Front end rigidlity query

Joined
23 January 2006
Messages
244
Hey track stars: My question regards whether the front bumper beam adds rigidity to the front frame stubs by resisting twisting. I know some say they have pulled the beams altogether. While I've seen the realtime cars several times, i can't recall what the race cars do, and what are you track stars doing. I'm trying to drop weight and took a flier on a procar CF beam as I liked the rear beam that doesn't provide any stiffness, but from what I can see thru the hood, it looks like the stock front beam does provide considerable resistance. To be clear, I'm not talking holding the front stubs at a given distance, I'm talking the three bolts on each end resisting the frame stubs from twisting (looking from the front or back). FYI I don't yet have the R supports, but I plan to add. Thanks all!
 
Yes the front bumper adds rigidity. You should feel the difference.

EditI believe the Real Time car had the reinforcements. They had to add weight to the car to be allowed to be in the class they competed in back when they last campaigned a NSX. This was told to us by Mr. Cunningham at Lime Rock, at a NSXNE event a few years back.

I have sent a question to them about this. I'll get back to you.

You'll feel the difference with the Type R supports as well. I do.
 
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Chassis rigidity is extremely important on a race car.
Is that what you're making or are you just seeking to lighten a mostly street driven car?

John, have you taken your front reinforcement off for the weight advantage? If you have, do you feel any difference in the front rigidity?
 
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Yes the front bumper adds rigidity. You should feel the difference.

PBasso is right :smile:

But please ALSO note that the six bolts that hold up the bumper to the chassis bars are not directly bolted into the chassis bars themselves. The bolts are fastened to clips which allow a small amount of play.

If you think the Procar CR front beam might not be stiff enough, you could try the aluminum version. From what I have been told by people that have mounted it that one is very stiff and strong.

I have NSX Coupe and after adding the NSX R front chassis bars I could feel the difference. I would highly recommend them especially if you are tracking your car.
 
PBasso is right :smile:

But please ALSO note that the six bolts that hold up the bumper to the chassis bars are not directly bolted into the chassis bars themselves. The bolts are fastened to clips which allow a small amount of play.

If you think the Procar CR front beam might not be stiff enough, you could try the aluminum version. From what I have been told by people that have mounted it that one is very stiff and strong.

I have NSX Coupe and after adding the NSX R front chassis bars I could feel the difference. I would highly recommend them especially if you are tracking your car.
Thanks Mym on the bolting, I obviousy have to look better tonight. I assumed with six large bolts that Honda intended this to resist the frame stubs and didn't even look hard. I don't think Procar has the alum beam any more. I want to talk with Detlef before commenting more on their beam. And John, HDPE and track time is NOT RACING (ouch!). Thanks all
 
John, have you taken your front reinforcement off for the weight advantage?

I do not run bumper beams on either of my race cars, nor have I ever retained them on any of my street or track day cars.

If you are uninhibited, then certainly a typical 'mod' is to remove them during prep. Frankly it's just extra weight you don't need hanging off the polar ends of the frame rails. They are certainly not an essential load bearing cross section for the suspension. They are primarily designed to bare impact and torsional loads.

Here is what they are really for. Note the word "fast laptime" does not appear to be mentioned anywhere. The driving factor has been the insurance industry trying to mitigate the cost of low to mid speed fender benders, and the NHTSA requires manufacturers provide them on US bound road cars.


If you have, do you feel any difference in the front rigidity?

No. I cannot say I've ever noticed anything negative by removing them on any car I've had.

I just use the Type R bars and slap the nose on using some modified brackets- basically the same simple assembly principles you would find on the pro cars such as the Le Mans GT-1 or Super GT, sans the dry carbon nose of course. :smile:

Particularly on an NSX, the chassis relative to most cars is already quite stiff. I further have a roll cage for one, and for two- bumper beam rigidity discussion aside, an increasingly significant portion of my front and rear substructure has been completely cut away at this point. I am prohibited by SCCA class rules in my region from extending my cage up past the bulk head, but it still rides like a skate board.


I don't think Procar has the alum beam any more. I want to talk with Detlef before commenting more on their beam.

I have a factory aluminum rear beam here if someone wants it for weight savings on their street car, drop me a PM. It's even polished.


And John, HDPE and track time is NOT RACING (ouch!). Thanks all

The same engineering principles apply to road course performance universally.

The only difference is, if and when you do get started racing an NSX- you may also come to appreciate not having that expensive and unnecessary pro-car or equivalent rear beam on when you get a light tap.

Aside from being totally pointless and unnecessary... and perhaps contributing to a more significant spin... the design hasn't been tested to the same standard as stock either... so it may not even serve the original function for which it was intended [when the #14 car backs into you in the paddock and takes out the tail lights and trunk lid.]

My 0.2
 
They are certainly not an essential load bearing cross section for the suspension. They are primarily designed to bare impact and torsional loads.

Not entirely true or accurate in this case. The reinforcement does tie the front rails together and decrease the front side member flex on the NSX. While it may have minimal if any effect to the shock towers the control arm and lower suspension mount points DO and will move with the rails.

Here is what they are really for.

A good read.
I am familiar with the article's premise and it is covered in much greater detail in I-Car Classes ie., structural damage identification, unitized structure repair and damage evaluation.


The front rails flex up and down and are not absolutely rigid front to back.
Proof of this is when cars are three dimensionally measured the specs are based on the front hanging which certainly gives a different, negative datum plane than when sitting on level ground. Untie the two front rails by removing the front beam increases the independent travel and twist of the front rails on this car and really would come to bear in the corners or any uneven height of the track surface.

I just use the Type R bars .
There you are! You're tying together the front rails. When you use these bars it is further stiffing up what the front reinforcement and radiator support provides. You are further minimizing that front rail/apron flex and twist.

I further have a roll cage .
Ah! I thought so. A roll cage will so stiffen up the driver's compartment it can keep you from feeling what's moving around in front of you beyond the cage because the twisting will end at the cowl and will decrease your likely hood of feeling it happening beyond that point, where you sit.

I agree the rear beam on this car does not have the same effect.
This is because in addition to a solid rear body panel there is a floor pan tying the two rails together keeping them from independent movement.

If forward crash protection is not a concern the aluminum front reinforcement you mention sounds like it is going to help keep the front rails tied on the same plane.

Again, in your driver's compartment with that cage and harness you likely won't feel the difference but your rails will stay on a more parallel plane to each other.
That should mean something for your lap times, once you adjust.
 
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Not entirely true or accurate in this case. The reinforcement does tie the front rails together and decrease the front side member flex on the NSX. While it may have minimal if any effect to the shock towers the control arm and lower suspension mount points DO and will move with the rails.

I am not debating that some questionable degree of extra rigidity may be a minor consequence, but it was not in fact the primary function of installing the part by the manufacturer.

Ultimately, you may too come to the conclusion that the benefit is of less overall value than the extra 40-50-60 or so odd lbs. If you are really concerned, simply substitute the re-inforcement bars or extend a cage to the front and it will be essentially a non-issue. Otherwise, leave it a road car which by design intent accounts for every possible contingency. :cool:


Ah! I thought so. A roll cage will so stiffen up the driver's compartment it can keep you from feeling what's moving around in front of you beyond the cage because the twisting will end at the cowl and will decrease your likely hood of feeling it happening beyond that point, where you sit.

I removed the bumper beam from my bone stock S2000... and the only significant effect I noticed on a race track was the acceleration was no longer quite as sluggish, my brakes were more responsive, and steering felt slightly more nimble/responsive.



I agree the rear beam on this car does not have the same effect.
This is because in addition to a solid rear body panel there is a floor pan tying the two rails together keeping them from independent movement.

Not really, no. The sheet aluminum floor pan can be bent by hand. The trunk floor pan is ribbed, so as to be rigid enough to support its primary function- holding detailing supplies. Their is, however a lateral aluminum span and sub-frame pieces which are structurally far more significant.


Again, in your driver's compartment with that cage and harness you likely won't feel the difference but your rails will stay on a more parallel plane to each other.
That should mean something for your lap times, once you adjust.

Ok. You worry about your bumper beam chassis rigidity.

I'll worry about the new set of Hoosier R6's that should be trackside for my race on the 8th, which I think should make a difference in my lap times, once I adjust. :wink:
 
The front reinforcement weighs under 20 lbs. In another thead NSXSupra said 17.73 lbs and I'd say that's about right.

With those tires, a cage, no front beam and hard G's on the corners I suggest that you occasionally closely check your side members for cracks.

Good luck racing and that is NOT sarcasm.:wink:
 
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First, sorry to John, apparently you DO race your NSX, my bad. Of course stiffened race cars are not exactly germain to the thread. The issue now from my seat regards Mym's comment about the bolting. If the beam attachment nuts "float" therefore not providing a rock solid stay, then thinking that the beam ends will resist frame stub twisting is a bogus. I can't verify without taking the damn thing apart. The beam would still hold the correct stub to stub distance which is a factor, but It's a smaller factor than the twisting. The Procar beam is about 1 1/2" by 2 1/2" and only about 1-2 millimeters thick. Yes you read right. It won't be going on the car, at least not without considerable beefing. Their rear beam is very nice at about 8 millimeters, so I didn't ask how think it was. If there is any torsion resisting going on, it will tear this beam to shreds on rough roads. I could make an alum plate, say 3/16" or so which would do the job, but If I do that, I'm not sure what good the $1000 beam will do me. I haven't emailed Detlef yet as i wanted to analyze to load conditions (I are an engineer FWTW). I'll have to pull the nose this weekend and study. Thanks all!
 
I'm talking the three bolts on each end resisting the frame stubs from twisting (looking from the front or back).

The rails won't twist on a central axis going front to rear if the front reinforcement is removed. Even if the rad support were cut in half or removed, I just can't see the box side members doing that.
 
Pbassjo- I'm speaking from ignorance here, but isn't that what the R bars do? I know the front stubs look massive, but generally all front stubs flex on the track. Thats why race cars generally brace accross the top to limit flex, right? I decided NOT to take my front end off and do my self-analysis as the driving season is just too short as it is. I spoke with Detlef about his beam that I feel is pretty useless. Regardless of our armchair analysis, it only makes sense to make sure the aftermarket part does at least as much as the stocker, in terms of chassis stiffness. He feels it is just fine of course, but it sounds like he will make me a stronger part. Thanks all, I will follow up this winter or if he makes me a better part before.
 
Here at the shop I have noticed that the rails will go left/right or up/down just by lifting the car.

Twisting the rail on a front to rear axis I have never encountered.

It is the opinion of some people, and not just here, that the front reinforcement is for forward crash protection and any rigidity it contributes is cursory.
I could agree for some cars but this one seems like it does make the car more rigid.

Later this week I am going to Le Mans, France and there will be several people from Honda of Japan including the father of the NSX, Mr. Urehara.
I plan on asking them if the reinforcement on this car adds rigidity or just crash protection.I'll get back to you.
 
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Pbasso, your input is excellent and your findings may help us determine the type of front reinforcements to use now that Stempo(sp) is offering a different product from the R bars. On my front beam issue, Detlef has agreed to make me another beam with members around 6mm. I'll see what we find out about the twisting. IF the stubs flex even a little, they would bend or break the beam. I'm kind of locked into this beam at this point, but I could easily make a 3/16" of so plate to fit under the CF beam to hold the stubs. I'm leaning towards that approach for the moment just to be safe.
 
A lot has been said here... we did a lot of r&d on the car to determine the importance of the front stability. I also noticed a big difference in braking ability when I installed ti-daves front clamps.. so I believe a noticeable difference can be felt on front rigidity..

With that said, I noticed a big difference on my car with our front beam as soon as I installed it and drove on freeway overpass turns...

If anyone would be willing to make a third party before and after opinion.. We would be willing to send a few out on a big discount... We would be willing to send more than one for this cause as well... pm for details
 
chassis flex sometimes is a desireable thing if you understand what is happening and you can use it to your advantage.
 
I do not run bumper beams on either of my race cars, nor have I ever retained them on any of my street or track day cars.

If you are uninhibited, then certainly a typical 'mod' is to remove them during prep. Frankly it's just extra weight you don't need hanging off the polar ends of the frame rails. They are certainly not an essential load bearing cross section for the suspension. They are primarily designed to bare impact and torsional loads.

Here is what they are really for. Note the word "fast laptime" does not appear to be mentioned anywhere. The driving factor has been the insurance industry trying to mitigate the cost of low to mid speed fender benders, and the NHTSA requires manufacturers provide them on US bound road cars.




No. I cannot say I've ever noticed anything negative by removing them on any car I've had.

John, just curious--have you ever been punted off the track? I have a few times in my Integra, and my rear bumper beam really saved my ass in terms of body work cost. My car was already 50% bondo back there anyway, so I fear it would have shattered had the impact gone into my rear quarter panel. :) After holding the rear bumper beam and seeing how light it was (at least the Integra one seems pretty light), I had no problem getting another one from the junkyard to replace it. It was worth the extra few pounds for me.

In the front of my car, I don't have a bumper beam, but I do have a nerf bar inside the bumper made of roll cage tubing. It has also saved me body work in certain cases where I was inadvertent punter. I bought the car used and it came with the nerf bars, and I always thought it was odd, but they really did work in the real world.

Note: I was not driving in a destruction derby! :biggrin:
 
John, just curious--have you ever been punted off the track? I have a few times in my Integra, and my rear bumper beam really saved my ass in terms of body work cost. My car was already 50% bondo back there anyway, so I fear it would have shattered had the impact gone into my rear quarter panel. :) After holding the rear bumper beam and seeing how light it was (at least the Integra one seems pretty light), I had no problem getting another one from the junkyard to replace it. It was worth the extra few pounds for me.

In the front of my car, I don't have a bumper beam, but I do have a nerf bar inside the bumper made of roll cage tubing. It has also saved me body work in certain cases where I was inadvertent punter. I bought the car used and it came with the nerf bars, and I always thought it was odd, but they really did work in the real world.

Note: I was not driving in a destruction derby! :biggrin:

My take on that is it just depends on the context.

If you are in a heavy grid perhaps, or with a lot of spec cars, and the green flag drops, and before the first corner their has already been six accidents on the first lap... ok.... maybe you will want to bolt-it back on that day, or better think twice about whatever it is that you are doing. LOL.

For the open track day, or enduro's, or racing with cup cars whereas everyone dials it back that one notch and gives each other a little more racing room, I don't think I share all that much of a concern. For qualifying, hot sprints, in-climate weather, etc... I've spun out or just left the track backwards many times at like 80mph... and the truth be told at the end of the day if you find a concrete wall and ball up an NSX chassis it is just going to be an expensive mistake. So, make good decisions and try to not do that.

As to your fixability point... I've seen many accidents on-track and the resulting damage over the years. I think their comes a point as a driver, where with the speeds you are carrying where it just really doesn't matter anymore. If you find a concrete wall or collect a car in your aluminum coke can- it's not going to be pretty with or without the 35mph safety bumper feature installed. It's just going to be tens of thousands of dollars if not a total loss. Always be prepared to accept that, or don't bring your car to a race track.
 
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If anything else, my newly installed front end chassis bar will hopefully protect me from a head-on collision. Otherwise, it's a very expensive chin-up bar.
 
If anything else, my newly installed front end chassis bar will hopefully protect me from a head-on collision. Otherwise, it's a very expensive chin-up bar.

Ken... are you reffering to the bar as being a non-working part???

I just want to state that we are believers in making our customers happy... If your un-happy with that bar I can issue a full refund and pay the shipping back... the brake ducts and clothes are yours to keep as our gift... but dont keep something you dont want, like, or believe is non-funtional.... please pm or call if this is the case...

Regards
 
Correction: I'm 100% satisfied. In fact, I was just making a sarcastic remark about the front bumper support as a response to the above posts.

On the track, I find improved steering response once the front chassis was firmed up. Hence the need for a beefier front chassis bar as the STMPO one I currently have installed. Keep making those cool parts...

Larry
 
Correction: I'm 100% satisfied. In fact, I was just making a sarcastic remark about the front bumper support as a response to the above posts.

On the track, I find improved steering response once the front chassis was firmed up. Hence the need for a beefier front chassis bar as the STMPO one I currently have installed. Keep making those cool parts...

Larry

Larry... man... sorry for calling you Ken... I was trying to figure out what name went with that handle

I wasent sure if you were sarcastic or not... I want to make sure everyone is happy so I always offer a refund if there are not... can you believe that...

Someone let Mark Johnson at Dali know this....not only do I actually ship every order... i'll let you ship it back!!!!!!

glad to hear you could feel the difference too man... you should write a review so more people get it... as in it's own thread... just a thought :smile:
 
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