Comparing a 510 4door chassis to a 2door chassis.
Comparing a 510 4door chassis to a 2door chassis.
We have all heard at one time or another that a 4door 510 has a more ridged [stiffer] chassis. I have seen many of them done up for different forms of motorsports and I was wondering what the pros and cons are when comparing a 4door to a 2door from a performance standpoint.
--- Is a 4door chassis more ridged or is this a myth? [Stiffness before any roll cage] and if so by how much? i.e. % stiffer / seat of the pants feel.
---How much more weight is a 4door over a 2door etc...
I would think that many 4doors are being used for racing now because they are easier to come by and are less expensive when compared to a 2door. I do know a 4door is a little harder to put rear flares on when larger tires are needed, but other than that is it giving up anything when comparing it to a 2door? 2doors arguably may be rarer, better looking, a better investment,ect.. etc... But let’s just talk about the performance differences if any.
-----CHAD----
--- Is a 4door chassis more ridged or is this a myth? [Stiffness before any roll cage] and if so by how much? i.e. % stiffer / seat of the pants feel.
---How much more weight is a 4door over a 2door etc...
I would think that many 4doors are being used for racing now because they are easier to come by and are less expensive when compared to a 2door. I do know a 4door is a little harder to put rear flares on when larger tires are needed, but other than that is it giving up anything when comparing it to a 2door? 2doors arguably may be rarer, better looking, a better investment,ect.. etc... But let’s just talk about the performance differences if any.
-----CHAD----
In just two days from now, tomorrow will be yesterday.
Re: Comparing a 510 4door chassis to a 2door chassis.
I'm guessing that what you are asking for isn't going to be answered. Likely there will be speculation and a little data here and there, but really this can't be determined without alot of science. With that said, Bertvorgon has said a couple of times that when he saw the 2 door flex on a big....thingy (tired )...the most give and flex was inside the door frame. So it seems that the more door opens you have the more flex you'd have....
"An intercooler...has never been, nor should ever be, considered icing on the cake. A proper intercooler is more cake."
Corky Bell, Maximum Boost
"one of the little things that add up"
-defdes
Corky Bell, Maximum Boost
"one of the little things that add up"
-defdes
Re: Comparing a 510 4door chassis to a 2door chassis.
I've heard over the years that the 4 door has a stiffer chassis than a 2 door. I don't buy it though, anyone who has taken a quarter panel off a 2 door knows that it has all the crap for a 4 door still in there. The only difference is the quarter is that it's welded on, which to mean makes it seem like it would be stiffer. But how much? I don't think very much.. At this time in there life's I think which ever one is less rusty has a stiffer chassis
"People don't like it when shit doesn't match their rule of thumb." Sam
Re: Comparing a 510 4door chassis to a 2door chassis.
Jeff, I think you hit the nail on the head there!icehouse wrote: At this time in there life's I think which ever one is less rusty has a stiffer chassis
I think the general notion was conceived because most rally and off road cars were 4 doors. This wasn’t because they were stiffer. Generally the 4 door cars sold for less (and racers are cheap), and the back seat was easier accessed for thing like mounting spare tires, which you really needed a lot of back in the days with the comparatively inferior tire designs. The 4 dr is heavier, slightly – 100 lbs.
Both cars have the same floor stampings, sheet metal thickness, same roof stamping; only the pillar is welded in a different spot.
Honestly, I think the difference would be minor.
From a guy who's rallied both - there was no difference in my opinion. But I did like the back seat access of the 4 dr for piling in spares when driving between events!
Byron
Love people and use things,
because the opposite never works.
because the opposite never works.
Re: Comparing a 510 4door chassis to a 2door chassis.
The difference is quite likely minor. I think the "four-door is stiffer" argument comes from the four-door having smaller individual openings for doors. The two-door door is, what, 4-5" longer than the four-door front door?
I'd also think rally cars being common with four-doors would also have something to do with access. If you've got tools or spares in the back, lots easier to open a door to get to them than move the front seat and get around whatever cage you might have.
I'd also think rally cars being common with four-doors would also have something to do with access. If you've got tools or spares in the back, lots easier to open a door to get to them than move the front seat and get around whatever cage you might have.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson
Re: Comparing a 510 4door chassis to a 2door chassis.
In my rally car, rear doors are awesome access hatches. I will also disagree that 2 doors are better looking. 2 door coupes, sure, but IMO the sedan proportions look best with 4 doors...proflex wrote:We have all heard at one time or another that a 4door 510 has a more ridged [stiffer] chassis. I have seen many of them done up for different forms of motorsports and I was wondering what the pros and cons are when comparing a 4door to a 2door from a performance standpoint.
--- Is a 4door chassis more ridged or is this a myth? [Stiffness before any roll cage] and if so by how much? i.e. % stiffer / seat of the pants feel.
---How much more weight is a 4door over a 2door etc...
I would think that many 4doors are being used for racing now because they are easier to come by and are less expensive when compared to a 2door. I do know a 4door is a little harder to put rear flares on when larger tires are needed, but other than that is it giving up anything when comparing it to a 2door? 2doors arguably may be rarer, better looking, a better investment,ect.. etc... But let’s just talk about the performance differences if any.
-----CHAD----
Oh yeah, the biggest drawback to the 4-door is the extra lip inside the rear wheel well. Flaring a 4 door is much more than a "little harder" than a 2 door. Rolling fenders doesn't get your much on a 4 door. This is my only regret about getting a 4 door.
Re: Comparing a 510 4door chassis to a 2door chassis.
All 510 sedan shells start life as 4 doors as stated previously.
All SR conversions in South Australia require torsional rigidity tests for road approval.
A non rusted 4 door will record on average a 600HP rating.
The 2 doors have recorded up to a 700HP rating.
Note that these are fitted with our kits which braces the front rails.
The addition of 2 pak foam in the sills & pillars plus a few light braces has recorded 950HP.
No roll cage on a 4 door.
The use of 4 doors for rally is a definite for access to spare tyre & battery etc.
Batteries & tyres in the boot (trunk) is a no no for rally use.
All SR conversions in South Australia require torsional rigidity tests for road approval.
A non rusted 4 door will record on average a 600HP rating.
The 2 doors have recorded up to a 700HP rating.
Note that these are fitted with our kits which braces the front rails.
The addition of 2 pak foam in the sills & pillars plus a few light braces has recorded 950HP.
No roll cage on a 4 door.
The use of 4 doors for rally is a definite for access to spare tyre & battery etc.
Batteries & tyres in the boot (trunk) is a no no for rally use.
Re: Comparing a 510 4door chassis to a 2door chassis.
Well it would appear that the 2door has a stiffer chassis if we go by what Baz is saying. I would imagine that they run these tests with the car mounted on some kind of machine to get these numbers which would put some science behind it. It makes sense to me because the 4door has two large openings in its side while the 2door has one slightly larger opening [4to5 inch’s] and one small opening where the quarter window goes. The 2door has the added bracing from the longer outer quarter panel and the bracing on the inside under the interior panel.
Does this matter? Probably not as the 4door can be made stiffer by adding bracing, roll cage, etc... I just wanted to see if there was any proof to what I have heard over the years that a 4door has a more ridged chassis. As you all have said above they do appear to have other advantages. Pros = Rear seat area access/ storage and lower purchase price. Cons. = 100 lb heavier and harder to flare. I would think that from a performance standpoint they would both make equally great cars after modifying them.
I love reading stuff like this. Thanks for everyone’s input. -------- CHAD -------
Does this matter? Probably not as the 4door can be made stiffer by adding bracing, roll cage, etc... I just wanted to see if there was any proof to what I have heard over the years that a 4door has a more ridged chassis. As you all have said above they do appear to have other advantages. Pros = Rear seat area access/ storage and lower purchase price. Cons. = 100 lb heavier and harder to flare. I would think that from a performance standpoint they would both make equally great cars after modifying them.
I love reading stuff like this. Thanks for everyone’s input. -------- CHAD -------
In just two days from now, tomorrow will be yesterday.
Re: Comparing a 510 4door chassis to a 2door chassis.
Outstanding! I love it when you come through with data I didn't know exists that backs up my very non-scientific thoughts! Thanks for that info BazBaz wrote:All 510 sedan shells start life as 4 doors as stated previously.
All SR conversions in South Australia require torsional rigidity tests for road approval.
A non rusted 4 door will record on average a 600HP rating.
The 2 doors have recorded up to a 700HP rating.
Note that these are fitted with our kits which braces the front rails.
The addition of 2 pak foam in the sills & pillars plus a few light braces has recorded 950HP.
No roll cage on a 4 door.
The use of 4 doors for rally is a definite for access to spare tyre & battery etc.
Batteries & tyres in the boot (trunk) is a no no for rally use.
Edit* what is 2 pak foam? google results are paint brushes and foams
"An intercooler...has never been, nor should ever be, considered icing on the cake. A proper intercooler is more cake."
Corky Bell, Maximum Boost
"one of the little things that add up"
-defdes
Corky Bell, Maximum Boost
"one of the little things that add up"
-defdes
Re: Comparing a 510 4door chassis to a 2door chassis.
It was discussed on an earlier project of his, it's a structural foam blown into the rockers and A pillars for stiffness.
Re: Comparing a 510 4door chassis to a 2door chassis.
The torsion test is done on a jig of sorts.
The rear end is anchored to plates dyna bolted in dead level concrete floor.
the mounting points are at the rear crossmember outer mounting bolts.
The front end is attached by a plate mounted to front crossmember.
This plate is bolted to a large beam which pivots on a mount that is also dynabolted to the floor.
the large 20ft beam is at 90 degrees to the center line of the car.
a number of dial indicator are lined up along the lower edge of the sill panels.
As weights are added to the beam the twist is recorded from the dial indicators.
A calculation is done to ascertain the amount of torsional twist and a rating is arrived at.
The rear end is anchored to plates dyna bolted in dead level concrete floor.
the mounting points are at the rear crossmember outer mounting bolts.
The front end is attached by a plate mounted to front crossmember.
This plate is bolted to a large beam which pivots on a mount that is also dynabolted to the floor.
the large 20ft beam is at 90 degrees to the center line of the car.
a number of dial indicator are lined up along the lower edge of the sill panels.
As weights are added to the beam the twist is recorded from the dial indicators.
A calculation is done to ascertain the amount of torsional twist and a rating is arrived at.