Effect of Track Width on Suspension Geometry
Discussion
What effect would widening the track of a vehicle have on the effectiveness of the suspension? Let me clarify.
Say a suspension was set up(ie attachment points, A-Arm length, ect) specifically for a certain wheelbase and track width. What if you moved the entire suspension (attachment points and all) say 2 inches outward on each side, would that have a negative impact on handling?
No, this is not just putting spacers on a wheel and calling it a day, this is actually moving the entire assembly out a couple of inches (retaining the same attachment points, just moved out parallel to the ground from where they were). This would increase your track width by 4" overall. Would you have to start from scratch at that point, or would anything at all need to be changed?
Say a suspension was set up(ie attachment points, A-Arm length, ect) specifically for a certain wheelbase and track width. What if you moved the entire suspension (attachment points and all) say 2 inches outward on each side, would that have a negative impact on handling?
No, this is not just putting spacers on a wheel and calling it a day, this is actually moving the entire assembly out a couple of inches (retaining the same attachment points, just moved out parallel to the ground from where they were). This would increase your track width by 4" overall. Would you have to start from scratch at that point, or would anything at all need to be changed?
LastPost, awesome response, that was pretty much what I was looking for. You're knowledge of the dynamics of suspension is impressive.
The aforementioned vehicle has unequal length A-Arms front and rear.
If the roll center was raised, would lowering the suspension slightly lower the roll center? I am not referring to the center of gravity. I know that as you lower a car, the roll center of the car is lowered to a greater extent than what the car was lowered.
The rear track would also be increased, however I was thinking the rear could be done with wider wheels with a little less offset. Though it would be almost as easy (but not quite) to move the rear out as well. To fine tune the oversteer/understeer tendencies could you not adjust it with a anti-sway bar and even shock/spring adjustment?
Could this be corrected by changing the lengths of the control arms, or would the attachment points need to be changed as well? I was looking at some suspension software that helps calculate correct lengths/angles ect of the suspension. This is for the most part hypothetical, but was really looking at widening my SLC.
I still have yet to fully understand Ackerman steering geometry (will have to do more reading on that one).
The aforementioned vehicle has unequal length A-Arms front and rear.
If the roll center was raised, would lowering the suspension slightly lower the roll center? I am not referring to the center of gravity. I know that as you lower a car, the roll center of the car is lowered to a greater extent than what the car was lowered.
The rear track would also be increased, however I was thinking the rear could be done with wider wheels with a little less offset. Though it would be almost as easy (but not quite) to move the rear out as well. To fine tune the oversteer/understeer tendencies could you not adjust it with a anti-sway bar and even shock/spring adjustment?
Could this be corrected by changing the lengths of the control arms, or would the attachment points need to be changed as well? I was looking at some suspension software that helps calculate correct lengths/angles ect of the suspension. This is for the most part hypothetical, but was really looking at widening my SLC.
I still have yet to fully understand Ackerman steering geometry (will have to do more reading on that one).
Edited by guitaraholic on Sunday 7th April 06:02
Good points.
LOL,, sorry I didn't specify. SLC as in Superlite Coupe. With full access to the monocoque, it's not to hard to add new extending brackets and attachment points to the chassis. If fact, I was looking at the design, and it could be made reversible (for the front at least).
this one is mine, it's sitting in storage till I get back from overseas
here is a finished example.
Here is a shot of the front suspension (again, this one is not mine)
LOL,, sorry I didn't specify. SLC as in Superlite Coupe. With full access to the monocoque, it's not to hard to add new extending brackets and attachment points to the chassis. If fact, I was looking at the design, and it could be made reversible (for the front at least).
this one is mine, it's sitting in storage till I get back from overseas
here is a finished example.
Here is a shot of the front suspension (again, this one is not mine)
when I get a chance in a few months I'll look at how mine are fastened. It looks like at least the attachment points for the UCA are just bolted on. I'll have to look for how the LCA are. That's the bad thing about being overseas, I can only let my mind wander, and do nothing about it for the moment.
http://staceydavid.com/sites/default/files/imageca...
http://staceydavid.com/sites/default/files/imageca...
Widening the track will be a two fold benefit.
1. Wider track will (if geometry is correct) should give better handling. Though from what I've been told it already out corners almost everything on the street.
2. Yes aesthetics are part of it. The car is too flat on the sides, widening the front and rear will give a nice contour and more depth. There are some other changes I am looking at as well.
I have been looking up a few suspension design programs (eg SusProg3D). I will more than likely be fabricating new control arms. Actually, going with chomoly should lighten it up a little bit as well vs the aluminum ones supplied.
From what I have been told the current SLC's suspension is within 3% of that of the Ford GT's. I was thinking if I were to widen the track 4-5", then maybe copying the setup of the Enzo would work. Though getting the measurements might be a bit of a trick. Enzo has (wheelbase 104"), (width 80").
1. Wider track will (if geometry is correct) should give better handling. Though from what I've been told it already out corners almost everything on the street.
2. Yes aesthetics are part of it. The car is too flat on the sides, widening the front and rear will give a nice contour and more depth. There are some other changes I am looking at as well.
I have been looking up a few suspension design programs (eg SusProg3D). I will more than likely be fabricating new control arms. Actually, going with chomoly should lighten it up a little bit as well vs the aluminum ones supplied.
From what I have been told the current SLC's suspension is within 3% of that of the Ford GT's. I was thinking if I were to widen the track 4-5", then maybe copying the setup of the Enzo would work. Though getting the measurements might be a bit of a trick. Enzo has (wheelbase 104"), (width 80").
You are correct, though was implying it to better corner grip. Yes, handling has to do more than with overall lateral grip. Handling also involves turn in, oversteer, understeer, responsiveness, ect ect. What would you recommend as a good suspension design software? I know there are guys that can hand jam it, but that's a special mind. I would much rather the software help design the optimal geometry.
I did look at Susprog3D. I guess the only way to do it is dive in and play with the software a bit.
The SLC has a pretty decent wheelbase of 105", and a track I am guessing around 61-62" for the front, with the rear being a little less due to the wider tires (I'll have to measure it when I get back)
As a comparison the Enzo has a 104" wheelbase and a F65"/R65" track.
Figure I would be adding about 3-4" of track with the increased width, it would be close to the same ratio of that of the Enzo, with almost the exact same weight distribution and height center of gravity.
This is just a question, but could you take out a little bit of the twitchiness by running a little bit of toe in on the rear wheels?
I did a little bit of a look up on the Stratos. Holy Chit Batman, the thing had a 86" wheelbase and was 69" wide. Yeah, that's go kart territory. Did some calculations after finding the track of the Lancia. Ratio is around 1.45, yeah, that's pretty nutts!!!!
The SLC has a pretty decent wheelbase of 105", and a track I am guessing around 61-62" for the front, with the rear being a little less due to the wider tires (I'll have to measure it when I get back)
As a comparison the Enzo has a 104" wheelbase and a F65"/R65" track.
Figure I would be adding about 3-4" of track with the increased width, it would be close to the same ratio of that of the Enzo, with almost the exact same weight distribution and height center of gravity.
This is just a question, but could you take out a little bit of the twitchiness by running a little bit of toe in on the rear wheels?
I did a little bit of a look up on the Stratos. Holy Chit Batman, the thing had a 86" wheelbase and was 69" wide. Yeah, that's go kart territory. Did some calculations after finding the track of the Lancia. Ratio is around 1.45, yeah, that's pretty nutts!!!!
Edited by guitaraholic on Sunday 7th April 16:53
I got the info from this site: Though after reading, the left column was a customized Stratos, the measurements below (a little narrower, are the real Stratos, which is 1.49, but still pretty short.
http://www.rallycars.com/Cars/Lancia/Stratos1.html
Length: 3710mm
Width: 1750mm
Height: 1114mm
Wheelbase: 2180mm
Front track: 1433mm
Rear track: 1457mm
Laden weight: 980Kg
Fuel capacity: 2 tanks totaling 80lt
And yes, I have definitely taken your words to heart. I may or may not go through with this, just looking at, if I do, to do it correctly. I'm still overseas for another 6-8 months, so it's just dreaming for now.
http://www.rallycars.com/Cars/Lancia/Stratos1.html
Length: 3710mm
Width: 1750mm
Height: 1114mm
Wheelbase: 2180mm
Front track: 1433mm
Rear track: 1457mm
Laden weight: 980Kg
Fuel capacity: 2 tanks totaling 80lt
And yes, I have definitely taken your words to heart. I may or may not go through with this, just looking at, if I do, to do it correctly. I'm still overseas for another 6-8 months, so it's just dreaming for now.
Edited by guitaraholic on Sunday 7th April 18:11
The reason I asked, the SLC's cousin, the Superlite LMP, uses the same hubs as the SLC, the car has a 78" width, but a 114" wheelbase (vs 104 for the SLC). The car is about 200lbs lighter than the SLC, and is about an inch lower. However, the geometry would be set up for a 78" wide car.
The weight distribution for both cars are pretty close as is the height c.o.g. From what I've read on the testing of the LMP, is it's a record breaking monster, can't wait to see it in action. Getting back on subject, all things considered would the suspension swap still be optimal if....
... Track width of SLC was modified (add 4") to be exactly that of the LMP
... Attachment points of the SLC were exactly replicated to that LMP
... Use LMP control arms
Yes, will still have to figure out the Akerman, but I think that's a lot easier than trying to get roll center's and such.
The weight distribution for both cars are pretty close as is the height c.o.g. From what I've read on the testing of the LMP, is it's a record breaking monster, can't wait to see it in action. Getting back on subject, all things considered would the suspension swap still be optimal if....
... Track width of SLC was modified (add 4") to be exactly that of the LMP
... Attachment points of the SLC were exactly replicated to that LMP
... Use LMP control arms
Yes, will still have to figure out the Akerman, but I think that's a lot easier than trying to get roll center's and such.
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