| Turn in Concepts | 11-21-2006 09:05 PM |
a thought on weight distribution
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You know over the past few days I've been thinking about something, and I want to get some more input in it. I figured the motorsports area would be my best bet as I'm betting someone in here has already played with this.
Anyway - on to my thought. I'm starting to think that a 50/50 weight distribution on these cars is not really the ideal setup. The root of my thinking on this goes to the fact that you can still, even with all sorts of trick suspension bits, rather easily overtax the available grip in front.
So I'm thinking to myself, don't overwork the front tires so much. That got me on to thinking of how I could keep that from happening. Aside from the obvious, and obligatory answers that are about to follow discussing driving style, turn-in, corner exit and that I'm an idiot, I was thinking something along the lines of a 47/53 or 45/55 might show some gains in front end grip at the limit.
Now, am I off my rocker for thinking this, and has anybody played around with that setup?
Anyway - on to my thought. I'm starting to think that a 50/50 weight distribution on these cars is not really the ideal setup. The root of my thinking on this goes to the fact that you can still, even with all sorts of trick suspension bits, rather easily overtax the available grip in front.
So I'm thinking to myself, don't overwork the front tires so much. That got me on to thinking of how I could keep that from happening. Aside from the obvious, and obligatory answers that are about to follow discussing driving style, turn-in, corner exit and that I'm an idiot, I was thinking something along the lines of a 47/53 or 45/55 might show some gains in front end grip at the limit.
Now, am I off my rocker for thinking this, and has anybody played around with that setup?
| waktasz | 11-21-2006 09:16 PM |
In a Subaru ? :O
| 10th Warrior | 11-21-2006 09:24 PM |
difficult to do with the engine hanging out beyond the front wheels.
| the_poser | 11-21-2006 09:34 PM |
fill the trunk with bricks
| Draken | 11-21-2006 09:56 PM |
wow. First off, Subies don't come stock with 50/50 weight distribution. So to acheive the figures you mention, you would need to either relocate several hundred pounds, or add several hundred pounds to the rear. Fairly impractical imo.
But good luck!
Chris H.
But good luck!
Chris H.
| Turn in Concepts | 11-21-2006 10:19 PM |
Hmmmm... perhaps I should have rephrased that. Replace weight distribution with corner weighted. Currently, I'm evenly corner weighted all around, and yes that does account for my fat butt.
| spazegun2213 | 11-21-2006 10:48 PM |
Well, if you really want an answer to having more weight in the rear, drive a 911. Or go ask some aircooled guys ;)
My "thought" based on my VERY limited knowledge of car dynamics and racing leads me to believe this. Subaru's in general have a long wheel base so pushing the car to 45/55 would mean that there is a LOT of weight as far back as you can put it. Therefore with the weight so far forward and so far in the rear the sedan would be very easy to unsettle. I would assume the car would understeer a little and with any lift of the throttle flip into oversteer.
As for corner weights... I think it would allow the car a little more traction on front but could lead to a semi twitchy car with throttle lift. However, I've never even had my car corner balanced, so i have no idea.
My "thought" based on my VERY limited knowledge of car dynamics and racing leads me to believe this. Subaru's in general have a long wheel base so pushing the car to 45/55 would mean that there is a LOT of weight as far back as you can put it. Therefore with the weight so far forward and so far in the rear the sedan would be very easy to unsettle. I would assume the car would understeer a little and with any lift of the throttle flip into oversteer.
As for corner weights... I think it would allow the car a little more traction on front but could lead to a semi twitchy car with throttle lift. However, I've never even had my car corner balanced, so i have no idea.
| kursplat | 11-21-2006 10:51 PM |
[QUOTE=Turn in Concepts;16074828]So I'm thinking to myself, don't overwork the front tires so much. That got me on to thinking of how I could keep that from happening. Aside from the obvious, and obligatory answers that are about to follow discussing driving style, turn-in, corner exit and that I'm an idiot, I was thinking something along the lines of a 47/53 or 45/55 might show some gains in front end grip at the limit.
Now, am I off my rocker for thinking this, and has anybody played around with that setup?[/QUOTE]
well, i've always wanted to do an auto-x with all the cars driving in reverse, that would net a serious change in weight distribution :lol:
Now, am I off my rocker for thinking this, and has anybody played around with that setup?[/QUOTE]
well, i've always wanted to do an auto-x with all the cars driving in reverse, that would net a serious change in weight distribution :lol:
| topguneagle1 | 11-21-2006 10:55 PM |
in a lot of well balanced cars, i have seen set ups with the gas tank relocated to the rear even more, the battery to the rear, and like kumakubos drift sti, the radiator is in the rear, this may help with your weight distribution problem
| Jack | 11-21-2006 10:57 PM |
I would disagree with the twitchyness thought. Think of cars like a Fiero, MR2 for example. Very low moment. Get the car a bit out of kilter and they just love to start spinning around their center. Take a car with the weight way out front with counter weight way out back, it's going to take a lot to turn that thing and a lot to make it get upset.
I don't think it's a bad idea, if my understanding is correct. You're building a racecar, so you make it as light as possible and add weight to get to your minimum class weight. You're proposing to put the weight waaaay in the back to even up the f/r bias. I'd say that it will also make the car easier to drive and keep under control. I won't say that it will make the car faster through a corner, however. I don't know that.
jack
I don't think it's a bad idea, if my understanding is correct. You're building a racecar, so you make it as light as possible and add weight to get to your minimum class weight. You're proposing to put the weight waaaay in the back to even up the f/r bias. I'd say that it will also make the car easier to drive and keep under control. I won't say that it will make the car faster through a corner, however. I don't know that.
jack
| kursplat | 11-22-2006 01:32 AM |
does this exercise need to fit within any particular rules/class ?
| wagonmasta | 11-22-2006 03:24 AM |
buy a wagon :devil:
| spazegun2213 | 11-22-2006 08:02 AM |
[QUOTE=Jack ffr1846;16075732]I would disagree with the twitchyness thought. Think of cars like a Fiero, MR2 for example. Very low moment. Get the car a bit out of kilter and they just love to start spinning around their center. Take a car with the weight way out front with counter weight way out back, it's going to take a lot to turn that thing and a lot to make it get upset.
I don't think it's a bad idea, if my understanding is correct. You're building a racecar, so you make it as light as possible and add weight to get to your minimum class weight. You're proposing to put the weight waaaay in the back to even up the f/r bias. I'd say that it will also make the car easier to drive and keep under control. I won't say that it will make the car faster through a corner, however. I don't know that.
jack[/QUOTE]
True, but the reasons the MR2, nsx and others have close to 50/50 is the engine is in the middle. I do agree they spin like a top when unsettled (at least my friends NSX did). But, take that weight and put it at both ends, with none (well a passenger and thats about it) in the middle and you get almost the same thing. When the car is unsettled, one part of the car with all that weight/momentum is going to keep going.
Take a 911. I've heard from many reliable sources that most are totaled the first day they they really "drive" the car. Simply and owner not used to all the weight in the rear will lift in a corner. All the weight back there is unsettled and the back end comes around... and in a hurry too. Now, add 400 lbs to the front of a 911 and you still have the same problem when you lift.. correct?
I'm by no means an expert here, but this is a cool topic.
I don't think it's a bad idea, if my understanding is correct. You're building a racecar, so you make it as light as possible and add weight to get to your minimum class weight. You're proposing to put the weight waaaay in the back to even up the f/r bias. I'd say that it will also make the car easier to drive and keep under control. I won't say that it will make the car faster through a corner, however. I don't know that.
jack[/QUOTE]
True, but the reasons the MR2, nsx and others have close to 50/50 is the engine is in the middle. I do agree they spin like a top when unsettled (at least my friends NSX did). But, take that weight and put it at both ends, with none (well a passenger and thats about it) in the middle and you get almost the same thing. When the car is unsettled, one part of the car with all that weight/momentum is going to keep going.
Take a 911. I've heard from many reliable sources that most are totaled the first day they they really "drive" the car. Simply and owner not used to all the weight in the rear will lift in a corner. All the weight back there is unsettled and the back end comes around... and in a hurry too. Now, add 400 lbs to the front of a 911 and you still have the same problem when you lift.. correct?
I'm by no means an expert here, but this is a cool topic.
| Calamity Jesus | 11-22-2006 08:09 AM |
[QUOTE=spazegun2213;16075634]Subaru's in general have a long wheel base [/QUOTE]Only when compared to Miatas and Wrangers. Subarus often have the shortest wheelbases in their respective classes.
| the_poser | 11-22-2006 08:17 AM |
[QUOTE=STi Wamper;16077364]buy a wagon :devil:[/QUOTE]
couldn't have said it better
couldn't have said it better
| speedyHAM | 11-22-2006 08:58 AM |
I've wanted to try something like this for a little while and with the new SM autoX class weight rules (I have to run 135 lbs heavier this year than last), I am thinking about still taking weight off the front where ever possible and adding weight near the middle to get my CG as far back as possible. 50-50 front rear isn't that hard to get, so I'm thinking with some additional weight reduction at the front I could get 45-55 after the balast is added into the rear seat footwell.
The trick to great handling is to get the moment of inertia as low as possible while getting the CG of the car as low to the ground as possible and getting the CG a little behind the mid-wheelbase line of the car.
The trick to great handling is to get the moment of inertia as low as possible while getting the CG of the car as low to the ground as possible and getting the CG a little behind the mid-wheelbase line of the car.
| Virrdog | 11-22-2006 12:55 PM |
Bringing weight to the rear like you mention takes a load off the front tires allowing it to turn the front faster... but you end up with a back end that wants to go sideways. Ideally I think you would want more weight in the rear since that enhances your braking and turning. But since it can bite you so bad when the back end comes out... you are back to square one. Its a balancing act. :) (What's a pun?)
| Turn in Concepts | 11-22-2006 01:12 PM |
[QUOTE=Virrdog;16081362]Bringing weight to the rear like you mention takes a load off the front tires allowing it to turn the front faster... but you end up with a back end that wants to go sideways. Ideally I think you would want more weight in the rear since that enhances your braking and turning. But since it can bite you so bad when the back end comes out... you are back to square one. Its a balancing act. :) (What's a pun?)[/QUOTE]
Bingo! Thus my wondering if anyone has tried balancing more to the back. You can't tell me I'm gonna be the first to experiment with this, someone here has to have tried it.
Bingo! Thus my wondering if anyone has tried balancing more to the back. You can't tell me I'm gonna be the first to experiment with this, someone here has to have tried it.
| solo-x | 11-22-2006 01:33 PM |
newton just cringed reading this thread.
a car with a high PMI will be very difficult to get out of sorts, but equally as difficult to get back under control. once it gets going, it just doesn't want to stop. a car with a low PMI will be more easily unsettled, but also easier to reel back in. one of the adjustments i had to make going to the formula ford last year was that catches were much more subtle then when driving tin tops.
corner weights? double-u-tee-eff? one subject at a time d00d. screwing your corner weights won't help front grip unless you only turn one way.
with an awd car, moving weight rearward is going to improve front grip. adding weight to accomplish this is going to make the overall package slower though. if i had a choice between 2700lbs total weight with 54% on the front axle vs. 2900lbs total weight with 54% on the rear axle, i'd take the 2700lbs every single time.
a car with a high PMI will be very difficult to get out of sorts, but equally as difficult to get back under control. once it gets going, it just doesn't want to stop. a car with a low PMI will be more easily unsettled, but also easier to reel back in. one of the adjustments i had to make going to the formula ford last year was that catches were much more subtle then when driving tin tops.
corner weights? double-u-tee-eff? one subject at a time d00d. screwing your corner weights won't help front grip unless you only turn one way.
with an awd car, moving weight rearward is going to improve front grip. adding weight to accomplish this is going to make the overall package slower though. if i had a choice between 2700lbs total weight with 54% on the front axle vs. 2900lbs total weight with 54% on the rear axle, i'd take the 2700lbs every single time.
| Draken | 11-22-2006 01:38 PM |
[QUOTE=solo-x;16081892]newton just cringed reading this thread.[/QUOTE]
ed z 45
ed z 45
| Suba_Roo | 11-22-2006 01:39 PM |
Check in with Gary Sheehan. If I remember correctly when he was campaining the WRX they were both battleing understeer and carrying a lot of penalty weight. I remember they even experimented with a big metal plate in the back of the car with exciting results. :huh:
I'm sure that they experimented with putting the "penalty" weight in all sorts of places so they should have some good info on what weight distribution does to the handing of a tracked subaru.
I'm sure that they experimented with putting the "penalty" weight in all sorts of places so they should have some good info on what weight distribution does to the handing of a tracked subaru.
| Turn in Concepts | 11-22-2006 01:43 PM |
[QUOTE=solo-x;16081892]newton just cringed reading this thread.
a car with a high PMI will be very difficult to get out of sorts, but equally as difficult to get back under control. once it gets going, it just doesn't want to stop. a car with a low PMI will be more easily unsettled, but also easier to reel back in. one of the adjustments i had to make going to the formula ford last year was that catches were much more subtle then when driving tin tops.
corner weights? double-u-tee-eff? one subject at a time d00d. screwing your corner weights won't help front grip unless you only turn one way.
with an awd car, moving weight rearward is going to improve front grip. adding weight to accomplish this is going to make the overall package slower though. if i had a choice between 2700lbs total weight with 54% on the front axle vs. 2900lbs total weight with 54% on the rear axle, i'd take the 2700lbs every single time.[/QUOTE]
I guess you missed my post where I clarified by explaing I was talking about cornerbalancing.
and of course you'd take the 2700lb car every single time...
a car with a high PMI will be very difficult to get out of sorts, but equally as difficult to get back under control. once it gets going, it just doesn't want to stop. a car with a low PMI will be more easily unsettled, but also easier to reel back in. one of the adjustments i had to make going to the formula ford last year was that catches were much more subtle then when driving tin tops.
corner weights? double-u-tee-eff? one subject at a time d00d. screwing your corner weights won't help front grip unless you only turn one way.
with an awd car, moving weight rearward is going to improve front grip. adding weight to accomplish this is going to make the overall package slower though. if i had a choice between 2700lbs total weight with 54% on the front axle vs. 2900lbs total weight with 54% on the rear axle, i'd take the 2700lbs every single time.[/QUOTE]
I guess you missed my post where I clarified by explaing I was talking about cornerbalancing.
and of course you'd take the 2700lb car every single time...
| solo-x | 11-22-2006 01:51 PM |
your first post talks about rear weight percentage. you "clarification" post changes the subject to cross weight percentage, or 'cornerbalancing'.
| Migo | 11-22-2006 02:05 PM |
I made some calculations and even used a wagon (more weight in the rear) to see what kind of distribution I could get out of it.
Here's the thread, and I think I had a conclusion somewhere a few posts down.
[url]http://forums.nasioc.com/forums/showthread.php?t=1128095[/url]
Here's the thread, and I think I had a conclusion somewhere a few posts down.
[url]http://forums.nasioc.com/forums/showthread.php?t=1128095[/url]
| Turn in Concepts | 11-22-2006 03:44 PM |
[QUOTE=solo-x;16082126]your first post talks about rear weight percentage. you "clarification" post changes the subject to cross weight percentage, or 'cornerbalancing'.[/QUOTE]
And that is what I had meant to say. The root of my question is this - has anybody played around with cornerbalancing to acheive beyond 50/50 distribution to something like 47/53 or 45/55? And if so, what was the affect on helping to cure understeer?
And that is what I had meant to say. The root of my question is this - has anybody played around with cornerbalancing to acheive beyond 50/50 distribution to something like 47/53 or 45/55? And if so, what was the affect on helping to cure understeer?
| Turn in Concepts | 11-22-2006 03:45 PM |
[QUOTE=Migo;16082323]I made some calculations and even used a wagon (more weight in the rear) to see what kind of distribution I could get out of it.
Here's the thread, and I think I had a conclusion somewhere a few posts down.
[url]http://forums.nasioc.com/forums/showthread.php?t=1128095[/url][/QUOTE]
Thank you. I will check that out.
Here's the thread, and I think I had a conclusion somewhere a few posts down.
[url]http://forums.nasioc.com/forums/showthread.php?t=1128095[/url][/QUOTE]
Thank you. I will check that out.
| afpdl | 11-22-2006 04:07 PM |
[QUOTE=Turn in Concepts;16083688]And that is what I had meant to say. The root of my question is this - has anybody played around with cornerbalancing to acheive beyond 50/50 distribution to something like 47/53 or 45/55? And if so, what was the affect on helping to cure understeer?[/QUOTE]
You cannot change f/r weight distribution with corner balancing. When you make your car 50/50 through corner balancing you are talking about cross weights not f/r. The only real goal is to make the car turn right and left equally not to affect over/understeer.
You cannot change f/r weight distribution with corner balancing. When you make your car 50/50 through corner balancing you are talking about cross weights not f/r. The only real goal is to make the car turn right and left equally not to affect over/understeer.
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