Jump to content
SAU Community

Chassis Flex

rtune
 Share

Recommended Posts

rtune Experienced

rtune

Posted
Posted

So i jacked up my r34 by the front right hard point and noticed when it was

on the jack that the drivers door hangs differently. Not by much but enough

to make a clack sound on the latch as it closes or opens.. passenger door opens

closes the same way however.

lower the car back down by that point and it closes normally again.

Is there really that much chassis flex/twist ?

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/
Share on other sites
BHDave Grand Master

BHDave

Posted
Posted

I don't have links handy but if you are going to foam fill the do A, B and C pillars as well as the chassis rails and sills. There are improvements in rigidity to be had according to some of the OEM manufacturers research but no quantifiable results in our cars.

Or just get a decent cage with some gussets to the a and b pillars...

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/#findComment-4271906
Share on other sites
  • 2 months later...
Duncan Grand Master

Duncan

Posted
Posted

wow I am late.

Yes the standard chassis flexes like crazy, but Ronin 09 said try it on most other cars!

In our new sports sedan we have a very serious cage but have also foam filled the A and B pillars, and the sills and chasis rails to get the most stiffness we can (and it adds stuff all weight). The problem is I can't tell if it made any difference because the didn't exactly do before and after tests on a 6 post shaker rig. But it is dirt cheap and light so it can't hurt.

The most common ways to spot the chasis flex is to close the door on a coupe while it is on a jack (it will clunk not just close), or jack it up from one corner and see how many wheels come off the ground. Our race car will lift 3 wheels off the ground when jacking it up from one corner.....

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/#findComment-4401339
Share on other sites
rtune Experienced

rtune

Posted
  • Author
Posted
wow I am late.

Yes the standard chassis flexes like crazy, but Ronin 09 said try it on most other cars!

In our new sports sedan we have a very serious cage but have also foam filled the A and B pillars, and the sills and chasis rails to get the most stiffness we can (and it adds stuff all weight). The problem is I can't tell if it made any difference because the didn't exactly do before and after tests on a 6 post shaker rig. But it is dirt cheap and light so it can't hurt.

The most common ways to spot the chasis flex is to close the door on a coupe while it is on a jack (it will clunk not just close), or jack it up from one corner and see how many wheels come off the ground. Our race car will lift 3 wheels off the ground when jacking it up from one corner.....

I read some info on foam filling and don't really like what I read. Nissan or Nismo recommend against it too. Why? because

although it appears to add rigidity, it will not flex, it will simply snap. So it might be great for a road car and add rigidity to

a point, but hammer it around a circuit and sooner or later (maybe sooner) it is going to snap at the point(s) that are doing

most work, and once snapped it is totally useless and nearly impossible to remove.

Stands to reason, I mean, take the popular foam products and make a tube, let them set. Very tough, like an iron bar?

but would you lean it against a wall at 45 degrees and stand on it? jump on it? you can do that with a roll cage, no problem,

but the foam will snap like a stick of rock candy. You can probably hit 2g vertical on some corners on some circuits.. thats

a 500 kg load hammering against the foam .. which has no flex at all ..

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/#findComment-4401396
Share on other sites
Duncan Grand Master

Duncan

Posted
Posted

yeah fair call and not just for foam filling. there is no doubt that a car that flexes more will last longer (it will take the shock and then flex back into place). the stiffer the car (or even any solid member) the more likely it is to crack instead of break.

In the case that we are using (light/stiff race car) I am happy to take that tradeoff. The less the suspension mounts can move compared to each other the more predictable the handling will be. If the chasis is stuffed in a couple of years of racing its just $5k for a new one.

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/#findComment-4401400
Share on other sites
Roy Grand Master

Roy

Posted
Posted

I think you will find that the foam in rails is an 60s and 70s thing, mostly from rallying. There was thinking that it helped with stiffness, but the main reason they did it was to keep mud and garbage out of the rails which over time would cause corrosion.

Again it was noted to help the stifness by a bees dick but the other reason i know rally guys do it to the B and C pillars is to improve the acustics in the cabin and help the driver hear the navigator with pace note calls. It tones down the NVH from all the hollow spaces in the cabin

Link to comment
https://www.sau.com.au/forums/topic/244458-chassis-flex/#findComment-4401820
Share on other sites
  • 1 month later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • jez NF
      The Evolution Of "night Fury"

      By jez NF · Posted

      Waaay ahead of ya....(evil laugh!!) Will show the fitment and spec details later when it isnt as rainy !
    • wizlb
      Flex Fuel Kit Workshop

      By wizlb · Posted

      Thanks Dose.....    I appreciate it!!
    • Dose Pipe Sutututu
      Dose's Sometimes DIY and Pay Someone Home & Boat Improvement Thread

      By Dose Pipe Sutututu · Posted

      I'll probably be putting the shit box back on the dyno again soon, I want to dial in the closed loop boost control properly. I'll have a camera facing the car/motor for fun too. Just note, there are essentially 3x 10AN inlets going into the catch can and 1x going back to the intake pipe. Most of the time the catch can "return" to the sump actually is the crank case breather, pushing air out.
    • Piggaz
      Ogura orc1000f vs Osg tr2cd vs Osg r3c experiences, max torque/max hp?

      By Piggaz · Posted

      I have the R3C with a Nismo slave and by no means does it behave like a stocker, it ain’t THAT bad. On take off just give a bit more throttle than you would say a coppermix and it’s fine. It will not slip though.   
    • uchoa
      Yet another RB Neo misfiring thread after reading all the others.

      By uchoa · Posted

      Okay. Final round of testing done. Got a friend to hook up a fancy scanner to the car and we also ran some compression and leakdown tests, she is healthy.  The MAF was definitely the culprit. So for future reference anyone with similar issues that find this thread. I suggest the following steps, in order of affordability:   Check your spark plugs for any fouling, replace plugs if they are bad or re adjust the gaps making it narrower (0.8mm would be good). Check every coil's resistance with a multimeter. It can be done by probing the IB and G pins on the coil pack. Resistance should be around 1.4 (+/- 0.1) Ohms Check the MAF. If you have Nissan connect or a good scanner with the 14 adapter it should allow you to see the voltage on the MAF reading should be around 1.1 - 1.2V when car is idling. But if you don't, buy a new MAF from Amazon and test, then return it. (For instance, I got a Chinese one for $40 that was reporting 1.3v on idle). If you still have scanner, you can run tests on the injectors to see if they are working, just remember to unplug the fuel pump fuse/relay and have no pressure on the line. Then listen for the noises that the injectors make. Clean/replace injectors as needed. Once you find the issue and fix, order thousands of dollars worth of OEM parts to refresh unrelated things (Optional)   PS: Thanks to the absolute legends of this forum for the responses and help to someone that went a bit over their head. (me)
×
×
  • Create New...