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Thread: Corner weighting

  1. #11
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    Re: Corner weighting

    didn't like the idea of paying a shop upwards of $300~$500 for a session especially when they keep telling me it's impossible to realise a 50% cross weight on a road car, and that my ride heights will definitely be uneven.
    It's really cool that you guys are that serious as enthusiasts. Yeah there are a lot of incompetent people who talk rubbish.. from your height example, to brakes, tires, suspension, engine hardware, tuning, etc. I have some killer examples to share just that I haven't had time to write.

    Regarding asymmetrical setups; to develop a properly optimized one for specific track, requires either a lot of time and money testing with an excellent driver, and/or quite a bit of time spent on a good DOE and in high quality simulation. And in the end it still takes a good and focused driver to really gain from the setup, especially if the setup is aggressively asymmetric for maximum benefit and not mild to the point that other variables overshadow the changes by an order of magnitude. If a driver is 0.25% or more off on best 3-lap-repeatable laptime ( nearly 0.4 seconds on a 2:30 lap) and/or inconsistent on any longer stint, then he shouldn't even be thinking of asymmetric setups. With any part of the 3 missing (proper simulation, proper testing, very good driver), it is too easy to get completely misled. As to how to determine how far off a driver is, that's a whole other thread.

    There have been drivers here around 3% off on laptime (which can be caused only by missing the driving fundamentals), who were misled by workshops and friends into messing around with asymmetric alignments, tweaking it every trackday based on inaccurate feel, assumptions, with no physical measurement at the track, no data. On top of that tweaking the dampers and rake constantly.. ending up wasting lots of time and money, constantly blaming the car for the times. While it would be interesting to discuss the minutiae of developing a proper asymmetric setup and how it integrates with the tactical and strategic elements in racing, it would not be practical for enthusiasts for cost and driver-quality reasons.

    The same might be said about corner weighting, but the difference is that while asymmetric alignment is looking for speed, corner weighting is only looking for stability or predictability. It is a necessary process to run after installing any ride height adjustable component to be a stable foundation for learning the basics of sport driving. Corner weighting is also many times cheaper and more straight forward vs developing a proper asymmetric setup. In the case of stock cars that are not ride height adjustable, we live with what the manufacturer has given us, which is probably a lot better than some aftermarket stuff just slapped on by some local garage just eyeballing it.

    For all enthusiast drivers, the truth that should be applied 99.99% of the time (but almost never is) is to forget power, forget super sticky tires, etc. and to just sort out hardware for of all oil and water temperatures and pressures, get braking repeatable, alignment and weight in the ballpark - symmetrical and normal. Lock this very normal and repeatable setup down down and then go out and start to do 5 - 10 lap stints, and a lot of them. Unless within 0.5% of best real laptime with electronics off, just keep practicing and working on the driving until it is there, even if it takes 10 trackdays. Before the first trackday and in between all subsequent trackdays, read authoritative driving books and think. Study whatever data you can collect and confirm the concepts you've read about so you remember them. When the driver finally gets to the ballpark times, he'll know what he wants the car to do dynamically and the low and high limits in different areas. He will have a much better idea on what to get, how to set it up, how to test if it's really doing what he needs it to.

    ===

    I think Daniel (dcs2k) was referring to alignment, in which case there is no need to disconnect the bars.
    For weighting he would have to disconnect the bars.
    Last edited by Shaun; 26-10-2013 at 01:31 PM.
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  3. #12
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    Re: Corner weighting

    shaun...very tough to digest. 3% of 2min 30sec is 4.5seconds. if a driver drives laps in that kind of variance. i think he shud forget about corner weightings or any other mods. he has other things to sort out like his consistency. n driving.
    also how many cars can be consistent in a 5-10 lap stints?


    so my question is...assuming a consistent enuf driver....doing corner weightings. how much time r we trying to shave here?

  4. #13
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    Re: Corner weighting

    Quote Originally Posted by totoseow View Post
    shaun...very tough to digest. 3% of 2min 30sec is 4.5seconds. if a driver drives laps in that kind of variance. i think he shud forget about corner weightings or any other mods. he has other things to sort out like his consistency. n driving.
    Yes, but the 3% was off from target laptime, not on variance. In terms of variance given a largely fade free vehicle it should be +/- 0.2% given clear laps. Even if the vehicle is subject to fade as most full weight high power road ars are, it is still very easy to compare 5 - 10 lap averages to a reference driver and laptime degradation over an extended stint.

    So within 0.25% of best 3-lap repeatable laptime (not one offs that kill the tires), and +/- 0.2% in terms of variance, carried over a longer stint.

    also how many cars can be consistent in a 5-10 lap stints?
    Few roadcars stock , but most can be made to do so in terms of everything except the tires. The driver will have to manage tires. Everything else can be made to take it if the drivers would just stop throwing money at power and trick suspension, carbon whatever, trick intakes and exhausts, and put it towards extra and/or better quality coolers, plumbing, ducts, shrouds. The car can actually become pretty fade free.

    so my question is...assuming a consistent enuf driver....doing corner weightings. how much time r we trying to shave here?
    Depends on how far off the car was to start, but I would say fairly little somewhere around 0.25%, but if the driver is quick and consistent and time matters to him, then 0.25% close to the boundary is worth a lot. The closer to the laptime asymptote, the greater the value of every tenth. The driver needs to be quick and consistent to really see a gain from it and not have it hidden by the driving variable which can easily overlap the weighting gain by multiples.

    The other thing about baseline setups like weighting, alignment, is just to get it sorted and know for sure it is not those issues when you think you feel something is wrong or you just don't know why the times are a certain way. It is also to eliminate stackups like if I decided to do a rough alignment and then a rough weighting and roughly set up my shocks, and roughly estimated my aero, etc. Each might only be worth a little time but it would all show in the time. If it is straightforward and not too expensive to sort out, I would just do it. It's not necessarily about spending on new hardware, but just setting up what you already have to better efficiency.

    ===

    On the topic of fade and consistency - please excuse me, but it is a major reason why karting is so great. Given a clear track, any variance in the last 15 laps of a 20 lap stint is purely due to driver inconsistency. The kart just doesn't fade significantly in any way once settled into temperature. Let's go!
    Last edited by Shaun; 07-01-2011 at 02:39 AM.

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  5. #14
    Shaun's Avatar
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    Re: Corner weighting

    Also consider what happens if the suspension coordinates and/or spring rates (most would be surprised) hence corner heights are far off enough on the car to require some fairly large height changes at the perch in order to get proper corner weights.

    If the damper that does not have its length separately adjustable from where the shaft sits at rest, now the points of limit travel in both bump and droop are different in right and left turns.. asymmetric..and can mean huge and sudden changes in relative roll stiffness (hence handling) if the previous setup ended up close to bumpstops or droop limit across the lap. This is one reason why inboard dampers activated by adjustable push/pull rods is preferred. With outboard dampers, as most all roadcars run, it can be useful to have a separate height adjuster other than the lower spring perch which changes proportion of bump and droop travel.

    The shorter the total travel, and closer to bump or droop limit a car runs, the more important it is to have adjusters that allow you to set exact damper shaft position start point independent of height. On spring-perch-only ride height adjuster outboard dampers, the multi-negative of low quality springs is clear. Unequal spring rates especially if paired diagonally = more perch adjustment on other diagonal = asymmetric roll stiffness = near equal wheel load but at differing spring rate

    Even in the case of dampers with independent height to preload adjustment, poor quality springs mean uneven preload as commonly set by installed length or number of turns on perch from initial contact of the spring's free length.

    ==

    While this is interesting and fairly inexpensive to do, it is generally overkill for road cars and lower tier racing, in fact most lower level race teams don't do it because they're constantly busy sorting other more basic issues. It's just that while on this topic there's no harm going one step further conceptually... same as with driving or tuning concepts.

    So anyway the summary is it's interesting to check any chassis with two pairs of exactly equal length (adjustable) completely solid struts installed at the nominal shock lengths F and R (each length symmetrical left to right) in place of the coilovers and check the corner weight which will show roughly how accurately the chassis was made. In a secondary test with these struts, you could induce a height change at one corner and the delta in cross will give you an indication of how torsionally stiff the chassis is. These struts can be designed to be installed on all cars with a simple and modular adapter system. Tires can be taken out of the equation by running solid wheels or plates with a flat edge.

    Also spring ratings should not be trusted but tested independently. Tested when new and periodically after that to check for changes in rate and/or length. The very best springs can have rate and length changes of around 5% after a season of hard running although unintended. You can only imagine how bad it would get with lower quality springs that manufacturers say are designed to even settle in at lower free heights...degree of which is large enough to just visually confirm. If a set of springs is not (or no longer) matched close on rate, then they should be matched to where the diagonal cross of their rates is as equal as possible.
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  7. #15
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    Re: Corner weighting

    WOW nice info !

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    Re: Corner weighting

    Hi Shaun,

    Great stuff, I just posted on this in the suspension folder only to find your thread here ( makes more sense for it to be in suspension folder IMHO)

    Qn: Where in SG can I find a workshop that knows how to do a proper coilover install, set rebound, compression...etc and have it corner weighted?

    Pls feel free to PM me in private if it's not convenient to post publicly.

    Cheers

  9. #17
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    Re: Corner weighting

    Quote Originally Posted by ClemZ View Post
    Hi Shaun,

    Great stuff, I just posted on this in the suspension folder only to find your thread here ( makes more sense for it to be in suspension folder IMHO)
    Hi Clemz, while it is a process carried out on the suspension system, I suppose the reason it was started in the track section is because the process can only be fully appreciated on track. On public roads, just about all driving is under limit and on rails....and if it's not it's only only a matter of time before the driver ends up maimed, dead, or in jail.

    Still it is good to get a symmetrical handling base even when the drive may not feel it. Same for alignment, damping, brake bias, etc. Without knowing how good the base is, the driver always wonders where he is as driver, where the car is, or what could have been on the whole.

    Qn: Where in SG can I find a workshop that knows how to do a proper coilover install, set rebound, compression...etc and have it corner weighted?

    Pls feel free to PM me in private if it's not convenient to post publicly.

    Cheers
    I'll be back in SG in a couple of days and will write more, but for now the short answer is that there is no one stop location currently (this may change in the near future ). Damper optimization is also separate from corner weighting and alignment. It just happens that usually it's a good time to check on it (depending on damper design) while the car is up in the air, wheels off, etc.

    Damper optimization can hardly be done at all in a garage. Needs track testing to optimize handling, or road testing for ride optimization. Or a mix of both depending on how the car will be used. And it's not just feel, but data acquisition involving a range of sensors, a fair bit of post processing, etc.

    For corner weighting and alignment in SG, I've worked with 2 service providers who are willing to put ego and blind repetition aside and actually think, take a macro view on targets and circumstances before going off course on micro. They're able to do this because of true passion for motorsport.

    There are others besides these 2 who would be capable of doing it, but they don't have the equipment or they are busy focusing on pushing products that make more money off the masses. Many big name garages have the equipment but don't know how to use it properly, or are too proud to ask for help or even admit the possibility that they're not using the hardware at full efficiency. Worse still is talking rubbish (magic talk) and actually applying it to cars, getting drivers more lost than when they started out.

    I'll PM you more info when I get back. It's actually coincidental that right after returning I have a session overseeing set up corner weighting for an already class winning car that immediately after its first corner weight found another 0.5 sec on an already close to limit laptime, to set a new best. This is data backed and not an empty claim. Car's had some changes made since and they second corner weight is just to check it and return it if necessary. If we can coordinate, it works well because the equipment will all be set up anyway. More efficient, lower costs.
    Last edited by Shaun; 17-11-2011 at 02:01 AM.

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    Re: Corner weighting

    Hi Shuan,

    Am very interested in handling mods and firmly believe that corner weighting the car would really help me on the track. Currently am on a set of coil overs with equal heights, feel that the car is leaning about 10 mm to the right as compared to the left. Also to note is that the rear right tyre is also leaning too much as compared to the other 3. Read your posts simply amazing. I am new here. Could you assist in hooking me up with someone who can help me out on this.

  11. #19
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    Re: Corner weighting

    Hi, between what points do you measure your ride heights? Is the 10mm tip actual measurement or 'feel' (eyeball) as you write? Coilovers are equal length in terms of top to bottom mount, or bottom spring perch to top cap? Free length or as installed? If the latter, is it measured with the car up on a lift or at rest down on the ground?

    As for the over leaning RR tire, when/where/how was your car last aligned and what are the numbers?

    Replied to your PM.. cheers

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    Re: Corner weighting

    Cheem but good acticle

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