Why you shouldnt lower your car too much, front or rear
08-31-09, 07:30 PM
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Why you shouldnt lower your car too much, front or rear
I wrote these 2 articles for an Australian soarer forum after getting numerous questions and after reading numerous threads about cars bottoming out etc.
I thought Id post them up here just incase it helps someone
________________________________________________________
Ok, after seeing numerous peoples cars on here with people whinging about xyz problems, and others wanting some decent performance suspension, but not knowing what they are doing (I call this pedders syndrome where they sell you any thing they can just so they can take your money)
If you only care about having some fun in your car, driving it and you are happy to have a not so perfect suspension package, STOP READING NOW. Close this window and dont bother reading on.
I dont know where to start with this so.... If you cant be bothered reading, just look at the pics, it makes sence really
Your soarer once you have lowered doesnt have enough stroke/suspension travel.
Before you say "I have only lowered it X inches" please think about it as " I have x Centre wheel to Gaurd (CWG)"
What this means is on bumps your car WILL:
Make crashing noises
Get very stiff on big bumps
Unsettle your car mid corner
mid corner if your already bottomed out through body roll and then hit a bump your in trouble
You will get bump steer steering wanders through its suspension stroke
Just to name a few
At any lower than 370CWG you will run into issues with bottoming out, and geometry issues.
No you dont have a one of a kind special one, none of them do, not your v8, not your TT none of them.
Your shock will bottom out on big bumps or high speed transitions.
I hear you saying " but I have a short stroke shock...."
You most likely dont, KYB, Boge, pedders, monroe, gabriel, bilstein, koni - NONE OF THESE ARE ANY SHORTER THAN YOUR STOCK ONES.
The other problem is short stroke shocks only hold the spring more captive, so they dont fall out, they dont give you and more stroke room to stop your car bottoming out.
Shortened body shocks are another story, but this STILL WONT HELP YOU.
Your wheel will collide with your upped wheel arch before you get very far anyway.
Almost every coilover has a shortened body, but as said, and as the pics show, your wheel will hit the wheel arch before you run out of stroke with shortened body shocks.
What this means is you still need to run a big enough bump stop to stop the wheel coliding with the arch, which negates the use of shorter shocks.
Base height or double spring height shocks make both of these problems even worse.
I have attached some pictures to show/prove to you that you wont have an "optimum" suspension setup if your car is too low.
Yes it will still handle well, yes it will feel better than before and it WILL handle better than before, but your suspension package is compromised and not at peak performance
Now onto suspension stroke, Your shock stroke IS NOT equal to your wheel stroke, your suspension rate ISNT 1:1
You prob have between 100 and 120mm of total stroke as it is now when its jacked up, less if your running a coilover.
once you put it on the ground you lose about 30mm, once you lower it from stock height you lose between 20 and 40mm etc.
As you can see at 360 CWG you have exactly half bump and rebound stroke, but the bump stop interferes with bump, so atm I have only about 30mm if that total bump stroke.
I can tell you this its not enough. I have reached the limit of my current suspension setup with stock guards. Nothing can be done except raise the car up.
All my measurements were done using a 235/45/17 tyre, if you are running a bigger tyre/ rim combo than this you are in even more trouble.
So what are your options?
Get stiffer springs, I myself am running 15kg fronts and even at 360cwg it still bottoms out on big bumps.
Raise your car to 370 or 380 cwg
Some bilstein progressive bump stops will help alot, but its not a fix for the actual problem, Rather than them colliding it will slow the shock down progressivly before it bottoms out.
Tub the car, and cut the original arches out completley.
Of the 3 dedicated race soarers in the world, (2 D1GP and 1 in the UK) they all run a full tubbed setup, and the green D1 car runs 26kg springs.
This is what is needed for an optimum setup whether it be street or race use,
The problem is i see alot of cars on this forum that are even lower than mine, and you guys must hae the worst handling soarers in the world.
Its not just me, If you do some research o the US forums you will see on the supra forums, and in the massive Gilmer Gixer suspension thread, that low cars arent a possiblity with soarers/supras, not if performance is your goal.
now I havent even mentioned your suspension geometry problems that you will get form being this low either,
your roll centre will be out, meaning your car will bump steer and also it gets more body roll the more you lower your car.
I wont go into it now, but anyway
Just like the front end you cant lower your car too much with all non airbag soarers.
There are some slight differences to the front end though.
The wheel/tyre itself has infinite travel in the rear, you can slam it as much as you like without having the tyre smash into body work (not including the outer wheel arch)
Where as the front end the tyre hits the upper guard and chops up your wiring loom.
So why cant I lower it too much then?
Simply your shock runs out of travel. The lower you go the less travel you can use.
I have provided the measurements on how much travel you have for a given ride height. I have included some pictures if you need the graphical image.
This is called BOTTOMING OUT. You might not even notice it, but if you were take a drive in 2 identical cars, but one that doesn’t bottom out and one that does, youd notice.
You may think yours isnt, as most of my customers do. They all think “no mine doesn’t do that” but your simply wrong. Refer to the pictures and data below and youll see you are probably riding on the bumpstops right now, you just don’t know it.
The best thing about this problem is there are solutions, unlike the front end.
Now most people will say “but I can get short stroke shocks blah blah”
Sorry your wrong. Even if you could buy a short stroke shock, it wont help you. They will only give you less droop travel and wont gain you and bump travel.
The other thing is, they simply arent available for our cars. No one makes them, don’t argue. You also don’t need a short stroke shock as I just outlined.
What you actually need is a short “body” shock. The yellow part on my bilstiens would be shorter if they were a short body.
One problem, once again they DON’T exist. Sorry to bear the bad news. No brands out there offer a short body shock absorber for our models.
So what can I do to restore my travel issue?
Unfortunately you have to change to a coilover in most cases, read on….
Unlike the front, using a short body/stroke COILOVER in the rear actually works.
It fixes all you bump problems, but it doesn’t allow you enough droop travel in most cases (or not ideal droop I should say)
Many brands out there make a short body coilover, almost any double adjustable height coilvoer will do this for you. Tein superstreets DO NOT, as they are a single adj version.
What is the solution……
This is the easiest and cheapest solution to the problem is what is called in the industry a raised upper shock absorber mount.
What this does is mounts the top of the shock shaft inside the boot area rather than level with the top of the shock mount. These work by allowing the shock absorber body to continue travelling up past the body, beyond where it would normally “bottom out”.
With this design you can basically set your ride up to have factory travel at any ride height. In the pictures of mine, even at the rim tucking ride height it is possible to have plenty of suspension travel.
This means your car will still ride extremely well.
There is a catch though….
This only works a small amount if you are using lowered springs. There is a limit to how much you can raise the upper shock mount if your using normal springs.
The more you raise the mount the more your springs are compressed. 20mm is acceptable in most people’s cases, as almost every lowering spring is 20mm shorter than a stock spring anyway.
Now for the good news….
If your using a coilover setup like myself, OR if you’ve bought some tein super streers (or almost any other coilover) then you can gain back up to 80mm of travel. That’s more than youd EVER need.
The idea is to pick your desired ride height, work out how much Droop VS Bump travel you require and then raise the top shock mount up from there.
A good start is to look at the data I have collected, and work out how much droop vs bump your after.
You may not realsie is at the moment, but you may be running a droop/bump ratio of 90/10 at the moment, or 80/20 if your tyre is roughly level with the wheel arch.
You can work it out with the supplied data, and if your running any shock absorber, regardless of brand (KYB. Boge, OEM, tociko, bilstien etc) this data is accurate to your case.
This is all I have time for, feel free to ask any questions
[img]https://i296.photobucket.com/albums/mm173/buffalotheatre/CWGandShockDiagram.jpg[img]
I thought Id post them up here just incase it helps someone
________________________________________________________
Ok, after seeing numerous peoples cars on here with people whinging about xyz problems, and others wanting some decent performance suspension, but not knowing what they are doing (I call this pedders syndrome where they sell you any thing they can just so they can take your money)
If you only care about having some fun in your car, driving it and you are happy to have a not so perfect suspension package, STOP READING NOW. Close this window and dont bother reading on.
I dont know where to start with this so.... If you cant be bothered reading, just look at the pics, it makes sence really
Your soarer once you have lowered doesnt have enough stroke/suspension travel.
Before you say "I have only lowered it X inches" please think about it as " I have x Centre wheel to Gaurd (CWG)"
What this means is on bumps your car WILL:
Make crashing noises
Get very stiff on big bumps
Unsettle your car mid corner
mid corner if your already bottomed out through body roll and then hit a bump your in trouble
You will get bump steer steering wanders through its suspension stroke
Just to name a few
At any lower than 370CWG you will run into issues with bottoming out, and geometry issues.
No you dont have a one of a kind special one, none of them do, not your v8, not your TT none of them.
Your shock will bottom out on big bumps or high speed transitions.
I hear you saying " but I have a short stroke shock...."
You most likely dont, KYB, Boge, pedders, monroe, gabriel, bilstein, koni - NONE OF THESE ARE ANY SHORTER THAN YOUR STOCK ONES.
The other problem is short stroke shocks only hold the spring more captive, so they dont fall out, they dont give you and more stroke room to stop your car bottoming out.
Shortened body shocks are another story, but this STILL WONT HELP YOU.
Your wheel will collide with your upped wheel arch before you get very far anyway.
Almost every coilover has a shortened body, but as said, and as the pics show, your wheel will hit the wheel arch before you run out of stroke with shortened body shocks.
What this means is you still need to run a big enough bump stop to stop the wheel coliding with the arch, which negates the use of shorter shocks.
Base height or double spring height shocks make both of these problems even worse.
I have attached some pictures to show/prove to you that you wont have an "optimum" suspension setup if your car is too low.
Yes it will still handle well, yes it will feel better than before and it WILL handle better than before, but your suspension package is compromised and not at peak performance
Now onto suspension stroke, Your shock stroke IS NOT equal to your wheel stroke, your suspension rate ISNT 1:1
You prob have between 100 and 120mm of total stroke as it is now when its jacked up, less if your running a coilover.
once you put it on the ground you lose about 30mm, once you lower it from stock height you lose between 20 and 40mm etc.
As you can see at 360 CWG you have exactly half bump and rebound stroke, but the bump stop interferes with bump, so atm I have only about 30mm if that total bump stroke.
I can tell you this its not enough. I have reached the limit of my current suspension setup with stock guards. Nothing can be done except raise the car up.
All my measurements were done using a 235/45/17 tyre, if you are running a bigger tyre/ rim combo than this you are in even more trouble.
So what are your options?
Get stiffer springs, I myself am running 15kg fronts and even at 360cwg it still bottoms out on big bumps.
Raise your car to 370 or 380 cwg
Some bilstein progressive bump stops will help alot, but its not a fix for the actual problem, Rather than them colliding it will slow the shock down progressivly before it bottoms out.
Tub the car, and cut the original arches out completley.
Of the 3 dedicated race soarers in the world, (2 D1GP and 1 in the UK) they all run a full tubbed setup, and the green D1 car runs 26kg springs.
This is what is needed for an optimum setup whether it be street or race use,
The problem is i see alot of cars on this forum that are even lower than mine, and you guys must hae the worst handling soarers in the world.
Its not just me, If you do some research o the US forums you will see on the supra forums, and in the massive Gilmer Gixer suspension thread, that low cars arent a possiblity with soarers/supras, not if performance is your goal.
now I havent even mentioned your suspension geometry problems that you will get form being this low either,
your roll centre will be out, meaning your car will bump steer and also it gets more body roll the more you lower your car.
I wont go into it now, but anyway
Just like the front end you cant lower your car too much with all non airbag soarers.
There are some slight differences to the front end though.
The wheel/tyre itself has infinite travel in the rear, you can slam it as much as you like without having the tyre smash into body work (not including the outer wheel arch)
Where as the front end the tyre hits the upper guard and chops up your wiring loom.
So why cant I lower it too much then?
Simply your shock runs out of travel. The lower you go the less travel you can use.
I have provided the measurements on how much travel you have for a given ride height. I have included some pictures if you need the graphical image.
This is called BOTTOMING OUT. You might not even notice it, but if you were take a drive in 2 identical cars, but one that doesn’t bottom out and one that does, youd notice.
You may think yours isnt, as most of my customers do. They all think “no mine doesn’t do that” but your simply wrong. Refer to the pictures and data below and youll see you are probably riding on the bumpstops right now, you just don’t know it.
The best thing about this problem is there are solutions, unlike the front end.
Now most people will say “but I can get short stroke shocks blah blah”
Sorry your wrong. Even if you could buy a short stroke shock, it wont help you. They will only give you less droop travel and wont gain you and bump travel.
The other thing is, they simply arent available for our cars. No one makes them, don’t argue. You also don’t need a short stroke shock as I just outlined.
What you actually need is a short “body” shock. The yellow part on my bilstiens would be shorter if they were a short body.
One problem, once again they DON’T exist. Sorry to bear the bad news. No brands out there offer a short body shock absorber for our models.
So what can I do to restore my travel issue?
Unfortunately you have to change to a coilover in most cases, read on….
Unlike the front, using a short body/stroke COILOVER in the rear actually works.
It fixes all you bump problems, but it doesn’t allow you enough droop travel in most cases (or not ideal droop I should say)
Many brands out there make a short body coilover, almost any double adjustable height coilvoer will do this for you. Tein superstreets DO NOT, as they are a single adj version.
What is the solution……
This is the easiest and cheapest solution to the problem is what is called in the industry a raised upper shock absorber mount.
What this does is mounts the top of the shock shaft inside the boot area rather than level with the top of the shock mount. These work by allowing the shock absorber body to continue travelling up past the body, beyond where it would normally “bottom out”.
With this design you can basically set your ride up to have factory travel at any ride height. In the pictures of mine, even at the rim tucking ride height it is possible to have plenty of suspension travel.
This means your car will still ride extremely well.
There is a catch though….
This only works a small amount if you are using lowered springs. There is a limit to how much you can raise the upper shock mount if your using normal springs.
The more you raise the mount the more your springs are compressed. 20mm is acceptable in most people’s cases, as almost every lowering spring is 20mm shorter than a stock spring anyway.
Now for the good news….
If your using a coilover setup like myself, OR if you’ve bought some tein super streers (or almost any other coilover) then you can gain back up to 80mm of travel. That’s more than youd EVER need.
The idea is to pick your desired ride height, work out how much Droop VS Bump travel you require and then raise the top shock mount up from there.
A good start is to look at the data I have collected, and work out how much droop vs bump your after.
You may not realsie is at the moment, but you may be running a droop/bump ratio of 90/10 at the moment, or 80/20 if your tyre is roughly level with the wheel arch.
You can work it out with the supplied data, and if your running any shock absorber, regardless of brand (KYB. Boge, OEM, tociko, bilstien etc) this data is accurate to your case.
This is all I have time for, feel free to ask any questions
[img]https://i296.photobucket.com/albums/mm173/buffalotheatre/CWGandShockDiagram.jpg[img]
09-13-09, 04:48 PM
#4
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the fronts Are with a 235/45/17 tire.
The rear is with a 295/30/18 which is the wrong diameter anyway.
The rear doesnt have the same problem as the front (the tyre doesnt contact anything, its only the struts)
09-13-09, 07:44 PM
#6
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It is a new top hat, it basically just sits higher up in the car. So when you lower your car, it effectively gives your car more suspension travel
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