Gt40 suspension configuration and setup

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Dear all

just one point from my side. We have to differentiate Spring and shock and positioning of Spring along the shock absorber. Spring preload ( or changing of spring preload by changing the lower platform level) is not changing the total travel of the spring and point of load where it goes coil bind. As the words says it is only changing the preload which has to be overcome . over all the spring at a given load above the preload will always have the same compressed length.

So first of all the question must be answered , is the spring the correct one. A to weak of a spring for a given load will always go coilbind, independent what preload it will be given.

Secondly. if the spring is to weak the shock can go on block. Same will happen if the spring is to postioned to low on the shock , the shock will go on block before the spring goes on coil bind.

Therefore i can not fully agree to some reasonings in previous postings

TOM

 

[Randy V]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

This can happen to any car.
One thing (actually four) that I have for my car is Shock Bumpers. These will prevent coil bind when the right length is installed as well as preventing damage to the shock absorber itself.

AFCO Standard Blue Shock Bumper - Speedway Motors, America's Oldest Speed Shop

You can purchase these in varying rates of hardness and cut/shim to the appropriate length.

 

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Dear Randy

agree. of course this can happen to every car if the spring is to weak.
Just wanted to point out that the level of preload is not influencing coil bind tendency in any way. Therefore the level of the lower Spring collar is not relevant if the spring develops coil bind or not and therefore the bend arm has nothing to do with the lower spring collar level. It would not make any difference if the lower spring level would be screwed up as far it goes. This just changes the ride height of the car, but the spring would go coil bind at the very same load. Just basic suspension knowledge principles.

Of course shock bumpers can slow down the hard bump effect of coil bind or shock block. But this should be just a last reserve . In my opinion is just curing the symptoms and not the illness.

TOM

 

[Jac Mac]

Guys,

sorry for being absent the last week, but as said I am working for a US company and we are approaching year end and it is q4 the almost most important quarter for us


But back to the facts...

@Andy from Tornado.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I am not an engineer, but usually the spring is the first thing that MUST BLOCK to protect the coil over. If the coil over goes on block first, it can break and based on the design, if it breaks, you perhaps loose the whole wheel...Nice idea
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXI am not going to explain you, how to draw pictures with all forces working on a suspension, read a book.

But the more you move the coil over away from the hub, the more load is going on the suspension arm it is mounted to, and you need to increase stiffness of the material or change the design to carry that additional load.

What we see here on the LEFT side is a bend over time because of the weak material you have chosen. I assume ( not saying it was) that the bend on the right side was the same until the car was approaching the mentioned curve on the ring and then got bend more based on the high load. This explains the different amount of bending we see.

Your suspension arm design is bad and the material you have chosen is not up to the job, not even for street use.

You can call me wrong, but pls do it like an engineer, put facts, drawings and calculations on the table, keep your wrong assumptions for yourself.

And pls don't forget to send us a picture of the improved parts you mentioned.

However, if highly encourage you to visit race tracks and look how race cars are being setup. There are several parts of the old ring for example where the spring goes on block on nearly every car, even modern ones.


Having all said all this beside this, you should be ashamed, accusing other forum member here to bend the arms more just to harm you or your business.



@all other Tornado owners and drivers. My intention was to bring this to your attention so you all can deal with the information and improve your cars or not. But reading some comments here, is a bit disappointing. Don't believe someone how claims to have sold xxx amount of cars, is right with all he is saying. Start asking critical questions and don't trust comments from someone hows only interest it is to sell cars and not to pay for a product recall. It is his right to work revenue orientated, for sure, but clearly there is a borderline between revenue and callousness of other peoples health. Andy is not your best friend, he is ( and again this is his right) a business man who sells cars for a living.

There is a bent suspension arm and the manufacture has not respond to this threat with facts, drawings, explanations or solutions in a professional way.

That was what I wanted out of this.
Instead he is threaten forum members with lawyers, or accusing other forum members

Sorry if I do sound a bit upset but it reminds me to an old saying "Eat more shit a million flys can't be wrong"

Cheers
(C)arlos

(C)arlos, the statement from you in the above post is totally incorrect, The coil spring should NOT go into BLOCK or COIL BIND, to do so creates an instantaneous shock load thru the coil over to both the bottom arm and chassis points at which the coil over mounts, coil overs usually have a rubber or soft compound buffer fitted to the coil over shaft as seen in the attached photos, if not fitted then you must fit a rubber 'bump stop' to some part of the car chassis or suspension arm to perform this function. I have read both this thread & your build thread....you chose to not use the Tornado spring damper units, but sourced & fitted the ones on the car yourself, given the above statement its obvious you made a bad choice & chose/fitted a spring that was/is totally unsuitable for the application, under the circumstances you should perhaps be thankfull that the bottom arm failed in the manner it did. Would not matter what type of bottom arm was fitted, if you use BLOCK or COIL BIND as a travel limiter in any form of suspension it will eventually cause further damage or component failure. Looks like you might be the guy who needs to read some books!

 

[Jac Mac]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Guys,

sorry for being absent the last week, but as said I am working for a US company and we are approaching year end and it is q4 the almost most important quarter for us


But back to the facts...

@Andy from Tornado.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
I am not an engineer, but usually the spring is the first thing that MUST BLOCK to protect the coil over. If the coil over goes on block first, it can break and based on the design, if it breaks, you perhaps loose the whole wheel...Nice idea
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXI am not going to explain you, how to draw pictures with all forces working on a suspension, read a book.

But the more you move the coil over away from the hub, the more load is going on the suspension arm it is mounted to, and you need to increase stiffness of the material or change the design to carry that additional load.

What we see here on the LEFT side is a bend over time because of the weak material you have chosen. I assume ( not saying it was) that the bend on the right side was the same until the car was approaching the mentioned curve on the ring and then got bend more based on the high load. This explains the different amount of bending we see.

Your suspension arm design is bad and the material you have chosen is not up to the job, not even for street use.

You can call me wrong, but pls do it like an engineer, put facts, drawings and calculations on the table, keep your wrong assumptions for yourself.

And pls don't forget to send us a picture of the improved parts you mentioned.

However, if highly encourage you to visit race tracks and look how race cars are being setup. There are several parts of the old ring for example where the spring goes on block on nearly every car, even modern ones.


Having all said all this beside this, you should be ashamed, accusing other forum member here to bend the arms more just to harm you or your business.



@all other Tornado owners and drivers. My intention was to bring this to your attention so you all can deal with the information and improve your cars or not. But reading some comments here, is a bit disappointing. Don't believe someone how claims to have sold xxx amount of cars, is right with all he is saying. Start asking critical questions and don't trust comments from someone hows only interest it is to sell cars and not to pay for a product recall. It is his right to work revenue orientated, for sure, but clearly there is a borderline between revenue and callousness of other peoples health. Andy is not your best friend, he is ( and again this is his right) a business man who sells cars for a living.

There is a bent suspension arm and the manufacture has not respond to this threat with facts, drawings, explanations or solutions in a professional way.

That was what I wanted out of this.
Instead he is threaten forum members with lawyers, or accusing other forum members

Sorry if I do sound a bit upset but it reminds me to an old saying "Eat more shit a million flys can't be wrong"

Cheers
(C)arlos

(C)arlos, the statement from you in the above post is totally incorrect, The coil spring should NOT go into BLOCK or COIL BIND, to do so creates an instantaneous shock load thru the coil over to both the bottom arm and chassis points at which the coil over mounts, coil overs usually have a rubber or soft compound buffer fitted to the coil over shaft as seen in the attached photos, if not fitted then you must fit a rubber 'bump stop' to some part of the car chassis or suspension arm to perform this function. I have read both this thread & your build thread....you chose to not use the Tornado spring damper units, but sourced & fitted the ones on the car yourself, given the above statement its obvious you made a bad choice & chose/fitted a spring that was/is totally unsuitable for the application, under the circumstances you should perhaps be thankfull that the bottom arm failed in the manner it did. Would not matter what type of bottom arm was fitted, if you use BLOCK or COIL BIND as a travel limiter in any form of suspension it will eventually cause further damage or component failure. Looks like you might be the guy who needs to read some books!

 

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

if there's no bump stop and the spring reaches full compression on a bump (because of improper spring selection or excessive pre-loading of the spring, for example)

Just to point it out again, because it is one of the most common missinformations on suspension. The load when a spring goes coilbind has nothing to do with the amount of preload givven to this spring ( except the case one would wind the collar up for full coil bind in still standing).

In any other case it just changes the level of the car. And as the term says, it is a preload, which needs to be overcome by any opposing load to move the spring. Therefore the load when spring goes coilbind is always the same.

If a spring is to weak you need to put in a stronger one, preloading does not help to make it stiffer over all.

to be honest i guess that most of our beloved GT40s replicase are undersprung because of the comfort desire of all us old farts driving them. Face it, they are racecars and its supsension is concepted like a racecars, short strokes, heavy springs, at least on the front, The rear is much more forgiving.

A good hint is to use cable ties as marker on the shocks and check how far the shocks stroke is used up in normal driving conditions, before you going to drive the car harder. if it uses up more than 2/3rds of the stroke and you only have <20% left,, change to a stiffer spring.

Usually the stiffer spring is than to short in full drop. So you will need a helper spring to secure the springs in position.

TOM

 

[Seymour Snerd]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

to be honest i guess that most of our beloved GT40s replicase are undersprung because of the comfort desire of all us old farts driving them. Face it, they are racecars and its supsension is concepted like a racecars, short strokes, heavy springs, at least on the front, The rear is much more forgiving.

That's an interesting point. Can anyone cite, with authority, the typical spring rates for a Mk I as raced in the period?

 

[Randy V]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

That's an interesting point. Can anyone cite, with authority, the typical spring rates for a Mk I as raced in the period?

Spring rates of the originals would only be relative to a replica if the replica shared the exact same configuration, hard points, etc..

One other bad thing about coil bind or bottoming of the suspension is that you will have one VERY evil handling car. One moment you are hooked to the track like a slot car, the next instant, you are backwards in the grass at a high rate of speed.. Ask me how I know this!

 

[Jac Mac]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I think there is a pic of a gold MK11 at le mans? in the gallery somewhere with a placard beside it with the spring rates on it, but as randy points out only useful to those with cars that have original suspension component dimensions. Just make sure that (C)arlos was not involved in its set-up

 

[Seymour Snerd]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I think there is a pic of a gold MK11 at le mans? in the gallery somewhere with a placard beside it with the spring rates on it, but as randy points out only useful to those with cars that have original suspension component dimensions. Just make sure that (C)arlos was not involved in its set-up

Good tip, thanks. In the case of an SPF, the dimensions are original.

In the other cases the figure is perfectly useful if you use the original dimensions to determine the wheel rate (consult your favorite chassis engineering book or recall you high school trigonometry), and then use your own dimensions to get back to the corresponding spring rate.

 

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Dimensioning a spring is pretty straight forward when you know your wheelload ( the load which is put onto the wheel by the weight of your car, cornering forces and all other external acting forces).

I have posted a excel sheets numerous times to calculate static springrate ( wheelrate). It helps to find the correct spring as long you have a reference to measure to.

Thats where the difficult part is. Tires, road conditions, weight distribution, suspension geometry and last but not least the driver is influencing those wheel loads.

One have to find out by oneself. THe savest way to this is probably to start with a quite stiff spring (800 -1000 lbs/inch) and check how far the shock is using his stroke. if you have enough left in even the hardest ride you did. you can probably go softer.

I personaly would go for the spring which uses the maximum ( negativ and positive) suspension travel possible and than make it about 25% more stiff to have some contingency for even harder loads.

But before thinking about the spring , think about your shocks. Put you car in ride height without spring and shock ( i put wooden blocks with 4,25" height under my car) and move your suspension to your maximum in travel. at a certain point usually the ball joint is limiting the travel ( or any other component like tire rubbing in fender and so on). You shock should have a maximum compressed length which is longer than that to avoid the overload the ball joints ( or any other component in binding). Taking account your geometry the stroke of the shock should be the full positive stroke plus idealy nearly the same dimension to give you the same negative travel. For example if your shock strok from ride height to maximum compressed length is 2" , than your total stroke length should be around 4". At ride height this stroke should be used about 50%.

Now it is the task to define the correct spring with the systematic described above.

Once you have found the correct springs, the task it is to balance the car ( oversteer understeer). One can do this with adjusting the swaybar rate, if you have a car with no sway bar you can do it with the spring. Never go softer than the minimum spring rate you have found with the systematic above. If your car understeers usually you go stiffer with the spring in the rear, if it oversteers you correct with a stiffer spring in front.

Springs do not cost a fortune and are quick to change in our cars ( Takes me 2 hours all around)

Again this are some basics and should bring you in the ballpark and should be good enough even for ambitioned street driving.

THis only represents my method to do it and is not meant to be the only thruth.:thumbsup:

TOM

 

[Cliff Beer]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Just to point it out again, because it is one of the most common missinformations on suspension. The load when a spring goes coilbind has nothing to do with the amount of preload givven to this spring ( except the case one would wind the collar up for full coil bind in still standing).

In any other case it just changes the level of the car. And as the term says, it is a preload, which needs to be overcome by any opposing load to move the spring. Therefore the load when spring goes coilbind is always the same.

If a spring is to weak you need to put in a stronger one, preloading does not help to make it stiffer over all.

to be honest i guess that most of our beloved GT40s replicase are undersprung because of the comfort desire of all us old farts driving them. Face it, they are racecars and its supsension is concepted like a racecars, short strokes, heavy springs, at least on the front, The rear is much more forgiving.

A good hint is to use cable ties as marker on the shocks and check how far the shocks stroke is used up in normal driving conditions, before you going to drive the car harder. if it uses up more than 2/3rds of the stroke and you only have <20% left,, change to a stiffer spring.

Usually the stiffer spring is than to short in full drop. So you will need a helper spring to secure the springs in position.

TOM

Tom,

Yes, technically speaking you're exactly right - the amount of pre-load doesn't affect the point of coil bind. However, practically speaking you (and anyone who knows the minimal basics) knows that it does. Why? When a guy winds up the adjuster on the spring perch so that there's less working travel in the spring (commonly done to lower the car....), and re-uses the same spring, then the likelihood of hitting the point of coil bind is much higher. That's how it works practically speaking.

I think everyone understands that. And I think you understand I wasn't suggesting otherwise.

 

[Seymour Snerd]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I think there is a pic of a gold MK11 at le mans? in the gallery somewhere with a placard beside it with the spring rates on it

Just looked, couldn't find it. Might it be somewhere else?

 

[Jac Mac]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Have been looking myself, I know I have posted on another thread in the past, cannot remember what it was in relation to though! will post it if /when I find it, have checked all my own saved stuff as well.

 

[Randy V]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I'm not entirely sure of the relevance of what one particular spring rate would be unless you knew the rest of the setup and the track it was configured for. I can't tell you how many times I changed spring rates for various tracks all on the same car. Right hand turn bias vs left hand, high bank and smooth vs. flat and technical, high speed vs. medium speed, aero no aero, etc.. Would we not have expected the same differing setups of these original cars and teams?

 

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Tom,

Yes, technically speaking you're exactly right - the amount of pre-load doesn't affect the point of coil bind. However, practically speaking you (and anyone who knows the minimal basics) knows that it does. Why? When a guy winds up the adjuster on the spring perch so that there's less working travel in the spring (commonly done to lower the car....), and re-uses the same spring, then the likelihood of hitting the point of coil bind is much higher. That's how it works practically speaking.

I think everyone understands that. And I think you understand I wasn't suggesting otherwise.

Dear Cliff

if i understand you correctly than you talking about the spring taking a set ( which most springs will do to more or less extend, depending on the quality and springlayout). Practically speaking , this set will not be depending on the preload, it will be depending on the total load put on the spring and its capability to withstand. What you end up is a spring with a different unload lenght ( shorter) and more relative spring winds on this new length ( spring winds per inch will increase) and therefore you get a spring with a lower spring rate.

TOM

 

[EGLITOM]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I'm not entirely sure of the relevance of what one particular spring rate would be unless you knew the rest of the setup and the track it was configured for. I can't tell you how many times I changed spring rates for various tracks all on the same car. Right hand turn bias vs left hand, high bank and smooth vs. flat and technical, high speed vs. medium speed, aero no aero, etc.. Would we not have expected the same differing setups of these original cars and teams?

Exactly,

thats what i pointed out also. One have to find the springs for his driving conditions. Of course if you are not fighting for the last 10th , the spring rates for a givven car will be not to far of from one car to the other.

Hey Randy, think this is a interessting discussion, but don´t want to completly destroy Carlos´s Thread. What about asking an admin (wink) to relocate those post to a new tread?
TOM

 

[Fred W Ballinger]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

I think there is a pic of a gold MK11 at le mans? in the gallery somewhere with a placard beside it with the spring rates on it

I have the pic saved. It says

Spring coil
Front - 505 lb
Rear - 336 lb

not a typo, they are non round numbers

Cheers

Fred W B

 

[Randy V]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

Exactly,

thats what i pointed out also. One have to find the springs for his driving conditions. Of course if you are not fighting for the last 10th , the spring rates for a givven car will be not to far of from one car to the other.

Hey Randy, think this is a interessting discussion, but don´t want to completly destroy Carlos´s Thread. What about asking an admin (wink) to relocate those post to a new tread?
TOM

Good idea Tom. I tried to do that once already this AM and failed. Will attempt again after more coffee.. :stunned:

 

[Keith]

Re: Possible Suspension Arm Failure, Racing - Tornado GT40

don´t want to completly destroy Carlos´s Thread.

I think Jac already did that...