Ride Height and Suspension Geometry
Discussion
the gazman said:
Hi Nigel.
1st question, are the wishbones about level.
2nd question, if you measure the out-rigger to the ground on a flat surface, is it about 145mm the front end and 155mm at the back end.
If not, go see Andy
I had this wishbone-level discussion with someone the other day, I'm convinced it's the most often talked piece of rubbish spouted with regard to suspension!
It can only be important (if at all) if:
The car is close to original spec and the original designer wanted the wishbones level because he found that to give the best overall handling compromise for most people and you yourself like that same handling bias.
It's not in the slightest bit important if:
The original designer found that having them not-level gave the best overall handling compromise or:
you have played about with the ride height and found a setting that gives you the handling you desire but this puts the wishbones at non-horizontal level but it feels great to drive!
It's also a complete waste of time to think about having level wishbones as soon as you put any load variation into the chassis.
In short, forget all about it, it's a complete red herring
Joo
I take on board what you are saying but there is this fashion of running cars lower than a snakes belly but still running on standard geo settings and we know this is wrong, don't we?
If the wishbones are roughly level, the ride height is around 150mm and that is apparantly close to the original factory setting, I then suggest having the back 10mm higher.
I only suggest this as a rule of thumb to establish if the car is running way too high or low and my recomendation of 155mm/145mm outrigger to ground is also not an exact science but does give an indication to the DIY market that they are not far off and can run at this before they take it in to a specialist for a full geo check.
Oh, BTW I've agreed to let Gugi do mine now I've fully Powerflexed and shocked it, I'll bet you a tenner he won't change the ride-height by more than a few mm.
>> Edited by the gazman on Sunday 23 April 08:02
I take on board what you are saying but there is this fashion of running cars lower than a snakes belly but still running on standard geo settings and we know this is wrong, don't we?
If the wishbones are roughly level, the ride height is around 150mm and that is apparantly close to the original factory setting, I then suggest having the back 10mm higher.
I only suggest this as a rule of thumb to establish if the car is running way too high or low and my recomendation of 155mm/145mm outrigger to ground is also not an exact science but does give an indication to the DIY market that they are not far off and can run at this before they take it in to a specialist for a full geo check.
Oh, BTW I've agreed to let Gugi do mine now I've fully Powerflexed and shocked it, I'll bet you a tenner he won't change the ride-height by more than a few mm.
>> Edited by the gazman on Sunday 23 April 08:02
Yes but is that to give the handling he wants, what he thinks you want, or what you actually want?
I have a fundamental problem with people saying the customer needs XYZ because Mr Smith at ABC garage says so, when in fact it may not be what the customer wants at all.
For example, A race car I know very well and have spent a lot of time developing with it's owner went into an often-pushed Race shop and the race techie there undid all the hard work I'd done on the back end, putting it back to it's pre-modded format. Result? .. car slower and less predictable and promptly put back to my spec. The techie also was saying stuff about suspension which was fundamentally untrue. What i'm saying there is you can't have a set of rules that you can universally apply to every car and every owner.. the mere fact we have a market for adjustable suspension proves that! .. and there's more to adustable suspension than ride heights/wishbone levelnessessess and damping rates.
A lot of what is said about suspension is red herrings and half-information, and some of what is said by some specialists is sometimes not very special (or even true) at all .. I'm just trying to explain that so much stuff is said and taken as gospell when in fact the reality is often very very different. I also disagree to some extent with your opening sentence, primarily because there are situations when i run my own car with it's belly on the floor (relatively speaking) , and other times when it looks like a 4by4 off roader. It depends what use i'm putting it to.
It all reminds me of being at school and being told things in class which actually aren't exactly correct, but will get you the marks in an exam answer without having to understand teh reasoning behind it - i like to know the fundamentals. I can never understand why anyone wouldn't want to tell how it is .. instead of saying generalisations which can often muddy the waters.
For instance .. when it's said set the rear 10mm higher .. is that unladen? driver? full tank of fuel or empty or half full? passenger? any luggage? on power or on trailing throttle or on contant light load? roof on or roof in boot? it all makes changes to the attitude of the car .. unless you work with the customer you'll never get to the bottom of any handling issues they have .. and is one reason i do very little mail order sales on suspension and lots of workshop-fit with the customer present and preferably a track day together aswell. Setting the rear 10mm higher unladen will be no good for an owner who uses his car primarily for heavily laden continental touring with his or her partner. Pointless information to him/her yet they might take it as absolutely necessary if setting up at home. It's not the information i woud be giving them.
Talk in generalisations and averages and you get an average car.
.. is what I believe and what is borne out from my experience
I have a fundamental problem with people saying the customer needs XYZ because Mr Smith at ABC garage says so, when in fact it may not be what the customer wants at all.
For example, A race car I know very well and have spent a lot of time developing with it's owner went into an often-pushed Race shop and the race techie there undid all the hard work I'd done on the back end, putting it back to it's pre-modded format. Result? .. car slower and less predictable and promptly put back to my spec. The techie also was saying stuff about suspension which was fundamentally untrue. What i'm saying there is you can't have a set of rules that you can universally apply to every car and every owner.. the mere fact we have a market for adjustable suspension proves that! .. and there's more to adustable suspension than ride heights/wishbone levelnessessess
and damping rates. A lot of what is said about suspension is red herrings and half-information, and some of what is said by some specialists is sometimes not very special (or even true) at all .. I'm just trying to explain that so much stuff is said and taken as gospell when in fact the reality is often very very different. I also disagree to some extent with your opening sentence, primarily because there are situations when i run my own car with it's belly on the floor (relatively speaking) , and other times when it looks like a 4by4 off roader. It depends what use i'm putting it to.
It all reminds me of being at school and being told things in class which actually aren't exactly correct, but will get you the marks in an exam answer without having to understand teh reasoning behind it - i like to know the fundamentals. I can never understand why anyone wouldn't want to tell how it is .. instead of saying generalisations which can often muddy the waters.
For instance .. when it's said set the rear 10mm higher .. is that unladen? driver? full tank of fuel or empty or half full? passenger? any luggage? on power or on trailing throttle or on contant light load? roof on or roof in boot? it all makes changes to the attitude of the car .. unless you work with the customer you'll never get to the bottom of any handling issues they have .. and is one reason i do very little mail order sales on suspension and lots of workshop-fit with the customer present and preferably a track day together aswell. Setting the rear 10mm higher unladen will be no good for an owner who uses his car primarily for heavily laden continental touring with his or her partner. Pointless information to him/her yet they might take it as absolutely necessary if setting up at home. It's not the information i woud be giving them.
Talk in generalisations and averages and you get an average car.
.. is what I believe and what is borne out from my experience
trackcar said:
Yes but is that to give the handling he wants, what he thinks you want, or what you actually want?
I have a fundamental problem with people saying the customer needs XYZ because Mr Smith at ABC garage says so, when in fact it may not be what the customer wants at all.
For example, A race car I know very well and have spent a lot of time developing with it's owner went into an often-pushed Race shop and the race techie there undid all the hard work I'd done on the back end, putting it back to it's pre-modded format. Result? .. car slower and less predictable and promptly put back to my spec. The techie also was saying stuff about suspension which was fundamentally untrue. What i'm saying there is you can't have a set of rules that you can universally apply to every car and every owner.. the mere fact we have a market for adjustable suspension proves that! .. and there's more to adustable suspension than ride heights/wishbone levelnessessess
A lot of what is said about suspension is red herrings and half-information, and some of what is said by some specialists is sometimes not very special (or even true) at all .. I'm just trying to explain that so much stuff is said and taken as gospell when in fact the reality is often very very different. I also disagree to some extent with your opening sentence, primarily because there are situations when i run my own car with it's belly on the floor (relatively speaking) , and other times when it looks like a 4by4 off roader. It depends what use i'm putting it to.
It all reminds me of being at school and being told things in class which actually aren't exactly correct, but will get you the marks in an exam answer without having to understand teh reasoning behind it - i like to know the fundamentals. I can never understand why anyone wouldn't want to tell how it is .. instead of saying generalisations which can often muddy the waters.
For instance .. when it's said set the rear 10mm higher .. is that unladen? driver? full tank of fuel or empty or half full? passenger? any luggage? on power or on trailing throttle or on contant light load? roof on or roof in boot? it all makes changes to the attitude of the car .. unless you work with the customer you'll never get to the bottom of any handling issues they have .. and is one reason i do very little mail order sales on suspension and lots of workshop-fit with the customer present and preferably a track day together aswell. Setting the rear 10mm higher unladen will be no good for an owner who uses his car primarily for heavily laden continental touring with his or her partner. Pointless information to him/her yet they might take it as absolutely necessary if setting up at home. It's not the information i woud be giving them.
Talk in generalisations and averages and you get an average car.
.. is what I believe and what is borne out from my experience
Hi Jools
(And apologies to all for the quick hijack of this thread)
Just wondering if you ever set the geometry up on mine when it was owned by Shaun?
I know you have worked on the car in the past but unsure exactly what!
Thanks
Rob
trackcar said:
Yes but is that to give the handling he wants, what he thinks you want, or what you actually want?
I have a fundamental problem with people saying the customer needs XYZ because Mr Smith at ABC garage says so, when in fact it may not be what the customer wants at all.
Erm,I give up Joo, we all know that every specialist has their own way of achieving a car set-up. I recomend everybody to go and get the car set up by a local specialist but so many people want to fit shocks and springs themselves and there has to be a starting point for getting the car near the mark to start with and that's all my settings are.
As whether having weight in the boot or passengers on board needs to be taken into consideration on an initial set-up is surely questionable but I take your point that there are many factors in getting the car set up to suit individual needs and even after a specialist set-up, it is entirely possible that a follow up visit may be necessary.
As for the race car being set up not to the owners liking, the relationship between a racing driver and workshop is not built up on one visit, surely it is based on long term discussions and feedback from the driver.
I'll leave it at that.
Derek
Don't be like that Bugsy, I'm just trying to say that there's a better way to approach this than just saying put the wishbones parallel to the ground.. and it's based on what the customer actually wants and teh car can deliver given it's design constraints rather than some arbitrary notion that I believe doesn't actually hold water in the real world anyway, what I'd like to see is getting rid of superfluous information that's largely misleading and substitute sensible advice that actually gets the job done.
For instance the wishbone thing (as that's a favuorite of mine) .. is said as : make the lower wishbones parallel with the ground.
Why? I understand your argument that it gets the car off the floor .. but is that then the right height? Why the rear 10mm higher? who came up with that figure? If 10mm is important why wasn't it 11mm? or 13mm? or 9mm? Is it just another arbitrary figure? People will be measuring their cars to get exactly 10mm now thinking that's going to give them sublime handling. Then they'll put some petrol in and it'll be 5mm.
Why only the lower wishbones? are the upper wishbones not important? Are either of them important? Why does this piece of information get bandied as the holy grail of setting ride heights? Why is it always stated and yet never related to the loading in the car? I believe that since the loading constantly changes this advise is at best misleading and really totally irrelevant in setting up the car imo...
It's this kind of advice that I think needs eliminating from forums.
The only thing that matters about ride height is that it gets you as close to the handling/grip you require with no bottoming out and no running out of droop in most situations (or at least limited if there's a good trade off elsewhere). Anything else is largely irrelevant. The height you end up with will be dependant on the use you're putting the car to, the spring/damper package you worked to and the type of driver you are. If ride height isn't important beyond the parallel wishbone scenario why sell adjustable platform dampers? (not just you, i mean anyone selling adjustable ride height dampers).
Don't give up, just say why setting the lower wishbones is the best way to quickly set up a car that's all. I'm not having a go at you or being awkward, I'm trying to work out why this piece of advise is so often used. It's use completely baffles me.
I'm more than willing to be proved wrong .. just let's see what technical merit there is for the arguement for lower wishbone parallelnessessess.
Anyone?
Edited to add :
the other reason the wishbone parallel thing is a red herring is that the actual wishbone has *nothing* to do with the geometry at the front of the car in itself .. that's governed by the line intersecting the ball joint and the wishbone inner pivot bushes.
On a TVR (as we're talking about), the articulation in the ball jont is significantly *above* the line of the wishbone, therefore you're not even putting the ball joint in line with the inner pivot by seting them parallel .. not that that matters anyway but I just wanted to clarify that point in case anyone was thinking that was the reason.
>> Edited by trackcar on Sunday 23 April 12:21
For instance the wishbone thing (as that's a favuorite of mine) .. is said as : make the lower wishbones parallel with the ground.
Why? I understand your argument that it gets the car off the floor .. but is that then the right height? Why the rear 10mm higher? who came up with that figure? If 10mm is important why wasn't it 11mm? or 13mm? or 9mm? Is it just another arbitrary figure? People will be measuring their cars to get exactly 10mm now thinking that's going to give them sublime handling. Then they'll put some petrol in and it'll be 5mm.
Why only the lower wishbones? are the upper wishbones not important? Are either of them important? Why does this piece of information get bandied as the holy grail of setting ride heights? Why is it always stated and yet never related to the loading in the car? I believe that since the loading constantly changes this advise is at best misleading and really totally irrelevant in setting up the car imo...
It's this kind of advice that I think needs eliminating from forums.
The only thing that matters about ride height is that it gets you as close to the handling/grip you require with no bottoming out and no running out of droop in most situations (or at least limited if there's a good trade off elsewhere). Anything else is largely irrelevant. The height you end up with will be dependant on the use you're putting the car to, the spring/damper package you worked to and the type of driver you are. If ride height isn't important beyond the parallel wishbone scenario why sell adjustable platform dampers? (not just you, i mean anyone selling adjustable ride height dampers).
Don't give up, just say why setting the lower wishbones is the best way to quickly set up a car that's all. I'm not having a go at you or being awkward, I'm trying to work out why this piece of advise is so often used. It's use completely baffles me.
I'm more than willing to be proved wrong .. just let's see what technical merit there is for the arguement for lower wishbone parallelnessessess.
Anyone?
Edited to add :
the other reason the wishbone parallel thing is a red herring is that the actual wishbone has *nothing* to do with the geometry at the front of the car in itself .. that's governed by the line intersecting the ball joint and the wishbone inner pivot bushes.
On a TVR (as we're talking about), the articulation in the ball jont is significantly *above* the line of the wishbone, therefore you're not even putting the ball joint in line with the inner pivot by seting them parallel .. not that that matters anyway but I just wanted to clarify that point in case anyone was thinking that was the reason.
>> Edited by trackcar on Sunday 23 April 12:21
trackcar said:
Why only the lower wishbones? are the upper wishbones not important? Are either of them important? Why does this piece of information get bandied as the holy grail of setting ride heights? Why is it always stated and yet never related to the loading in the car? I believe that since the loading constantly changes this advise is at best misleading and really totally irrelevant in setting up the car imo...
It's this kind of advice that I think needs eliminating from forums.
Don't give up, just say why setting the lower wishbones is the best way to quickly set up a car that's all. I'm not having a go at you or being awkward, I'm trying to work out why this piece of advise is so often used. It's use completely baffles me.
Sorry Joo, I didn't mean to be prickly about this.
There is much conflicting advice on the forums but two things are true IMHO and those are.
1) The standard ride height of a Chim/Griff is around 150mm
2) Most experts have a nose down attitude of 10/15mm static.
It just so happens that the lower wishbones are not far off level at these settings and for the DIYer are a good starting point.
Peace and love
We know Spax and AVO read these forums, Id love to have a dialogue with one of their guys about this topic .. I accept what you're saying about the starting point Bugsy .. But i'd really love to know why this feature of wishbones always crops up in so many topics and yet I've never found anyone who can adequately explain it's relevance in car set-up to me, especially so if the ball joint is not even on the wishbone centreline. You could have an S shaped wishbone and still have the same geometry if the pivots remain in the same place.
Like I say, it only seems remotely relevant to me if that's what the suspension designer ended up with as a result of his work, as soon as you move from std you should reconsider your ride heights accordingly.
Like I say, it only seems remotely relevant to me if that's what the suspension designer ended up with as a result of his work, as soon as you move from std you should reconsider your ride heights accordingly.
I think the reason for setting the lower wishbone level is so it goes into positive camber much easier when it is the inside wheel on a corner. one problem is though if you look at the front wisbones on a griff you are not looking at the right angle because the pivot point on the upright is above the wishbone and this is the real angle that matters .To get the most grip you have to have as much of the tyre on the road as you can ie. 0 degrees camber all the time but TVR suspension is not very good at this so the option for owners is to try and keep the car at the right angle to the road with harder springs and try and keep the wheels in one place like a gokart. I tried to induce more camber change on the front of my cerb by moving the outer pivot point down ( in relation to the wheel) and the car feels very nice to drive but I do not have the time or money to really test what a difference it has made .I am going to try something similar on my griff but moving the bottom pivot point down is not so easy so I am going to raise the top one to top wishbone doing more work. I have had some longer top ball joint holders made so they can be set to different angles in the hub carrier . The rear , which is more important I think , is going to be much harder , David
.. but i'm interested in the technicalities behind it all .. it's open for anyone to answer just Bugsy thought it was a dig at him i think when in fact i was wanting someone to give me a good answer, anyone lol!! and hopefully we might all learn something instead of taking everything in print as gospel. I question everything, especially when i can't think of a reason why something should be the way it is... it's in my nature and it's how people learn
I use the 'parallel wishbone' setting as a rough starting point. I don't see as many TVRs as you two do, but even so I see a huge variety in ride heights, usually quite a bit lower than I could recommend. The typical explanation is that it looks better because the wheels 'fill the arches more', sometimes this is backed up by 'it lowers the center of gravity which improves the handling'.
There are three issues with the ride height. It defines the working envelope of the wheels, springs and dampers. It defines the position of the roll axis, which has a big impact on the handling. It defines the amount of roll (and bump and pitch) induced camber change. Normally you would expect a suspension designer to resolve the first two issues, and then choose suspension mounting positions that address the third.
Purely in terms of the amount of roll induced camber change, having the lower wishbone flat gives a reasonable amount of roll induced camber for a roadgoing TVR; it's a reasonable compromise between fully compensating for the effect of body roll on camber, and getting too much camber change in pitch/bump.
There's no 'silver bullet', but I see flat wishbones as a reasonable starting point for an average road car, and I think you should be cautious about straying too far from there unless you know what you are doing to the handling.
Having said that: I run the front quite a lot lower than that on mine, I like having more roll induced camber on the outer wheel and with my suspension rates I don't suffer from high pitch/bump travel. It's not particularly scientific and probably not optimal, but it works for me.
There are three issues with the ride height. It defines the working envelope of the wheels, springs and dampers. It defines the position of the roll axis, which has a big impact on the handling. It defines the amount of roll (and bump and pitch) induced camber change. Normally you would expect a suspension designer to resolve the first two issues, and then choose suspension mounting positions that address the third.
Purely in terms of the amount of roll induced camber change, having the lower wishbone flat gives a reasonable amount of roll induced camber for a roadgoing TVR; it's a reasonable compromise between fully compensating for the effect of body roll on camber, and getting too much camber change in pitch/bump.
There's no 'silver bullet', but I see flat wishbones as a reasonable starting point for an average road car, and I think you should be cautious about straying too far from there unless you know what you are doing to the handling.
Having said that: I run the front quite a lot lower than that on mine, I like having more roll induced camber on the outer wheel and with my suspension rates I don't suffer from high pitch/bump travel. It's not particularly scientific and probably not optimal, but it works for me.
Indeed Peter, however, the compression/droop induced camber variation isn't a function of the lower wishbone position only, it's the function of the interaction of both the upper and lower wishbones and their relationship to the hub and chassis as you're aware.
The intersection of the centre of instantaneous rotation of the wishbones and the tyre contact patch defines the roll centre, and it's attitude from front centre to rear centre defines the roll axis .. which is fine and all understood .. but any of that can be alterered by the position of the upper arm, and indeed the roll centres for the whole mechanism can be altered by going to a different tyre profile even .. so i really really struggle to understand why the parallel wishbone thing is so often used. It really is largely immaterial from what I can see.
It sounds like I'm making a big issue out of this, and maybe I am .. but essentially the issue isn't with this particular topic as such (though it's a fave of mine as i said earlier) .. it's with the amount of techie info that's spoken which in actual fact is misleading, but for some strange reason keeps getting said over and over.
Peter .. how do you arrive at your working ride height, and what factors are taken into account whilst doing that .. and how much importance do you attach to the positions of your wishbones?
The intersection of the centre of instantaneous rotation of the wishbones and the tyre contact patch defines the roll centre, and it's attitude from front centre to rear centre defines the roll axis .. which is fine and all understood .. but any of that can be alterered by the position of the upper arm, and indeed the roll centres for the whole mechanism can be altered by going to a different tyre profile even .. so i really really struggle to understand why the parallel wishbone thing is so often used. It really is largely immaterial from what I can see.
It sounds like I'm making a big issue out of this, and maybe I am .. but essentially the issue isn't with this particular topic as such (though it's a fave of mine as i said earlier) .. it's with the amount of techie info that's spoken which in actual fact is misleading, but for some strange reason keeps getting said over and over.
Peter .. how do you arrive at your working ride height, and what factors are taken into account whilst doing that .. and how much importance do you attach to the positions of your wishbones?
Whilst I don't stray into discussions about roll centres because I am not qualified to do so, it has always been explained to me that lowering the car without completely changing the geo settings will efectively give you a car that does not handle very well.
I therefore advise all DIYers to stick to standard ride heights until they can consult with an expert and if I can I will suggest that they get the shocks supplied and fitted by one of these experts in the first place, which is probably why only about 20% of my sales are retail.
I therefore advise all DIYers to stick to standard ride heights until they can consult with an expert and if I can I will suggest that they get the shocks supplied and fitted by one of these experts in the first place, which is probably why only about 20% of my sales are retail.
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