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Thread: FWD track alignment

  1. #1
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    FWD track alignment

    I'm hoping the PF brains trust can help, I recently put in coilovers for the excel and it now handles like a bucket. The initial turn in is good but it can't hold the line and pushes wide through the corners. The alignment settings are -4 degrees camber front and rear, 2mm toe out at the front and 0 toe in the rear, 7 degrees of caster with 105mm ride height at the front and 110mm rear ride height, temperate spread between the inside, middle and outside of the tyre is 10 degrees in total.

    It handles worse than when I had king springs and shocks in the car, the previous alignment was -4 degrees camber front and rear, 2mm toe out front and 2mm toe in rear.

    A couple of other competitors suggested I am running too much caster, which is about the only other thing that I can think of changing to make a difference.

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    How much have you lowered the ride height at the front with the new coliovers, vs the King springs, vs the stock ride height?

    Edit: Where I'm going with this question is roll centre height.
    Last edited by Sprinkles; 29-08-17 at 05:45 PM.

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    Honestly I'm not sure I didn't measure the height when the King Springs were in the car. The other competitors run the ride height all the way down to 100 mm.

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    So I'm assuming this is an Excel Series race car? If so, you might be constrained on some of the following by the regulations, which I'm not familiar with, but I do understand that you have a control suspension package.

    The following is some causes of understeer in FWD McPherson strut track cars, and how to fix:

    Roll centre height too low, due to lowering ride height too much - Correct by raising ride height or adding roll centre correction such as longer ball joints.
    Front springs too stiff - softer springs
    Front roll bar too stiff - softer front roll bar, or disconnect
    Rear roll too soft - add stiffer rear springs or rear roll bar.

    I think your 4 degrees static camber sounds OK, especially with 7 degrees of caster. As you turn the steering, the caster gives you camber gain, and compensates for body roll. I suggest you try the easy stuff first, such as raising the ride height and disconnecting the front roll bar, these cost nothing.

    As a reference point for you, I have a Suzuki Swift track car, and had all of the above problems plus more in the past. We got them dialled out so that the car is now very neutral, and we can easily tune it between understeer or oversteer on any given day.

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    It is a Excel Series race car, there is a choice of 4 coilovers that can be used with set spring rates, i went with the xyz coilovers. Also can only run 4 degrees of camber and minimum 100mm ride height.


    When you say roll centre is too low, do you mean in regards to the control arms sitting at a poor angle when the car is lowered? I've tried disconnecting the front bar, hasn't helped, is there such thing as too much caster?

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    Re the roll centre height, you are correct re the control arm position. Stick your head under your car, if the control arms are parallel to the ground, that's as low as you want to go, if the chassis end is lower than the wheel end, that's too low, and you get too much body roll. On the Swift we found a 10mm correction to roll centre height was noticeable.

    Re the castor, we found that the more we added, the better the car went, to the point where we have the strut as far back in the tower as it will go, but I don't have a measurement sorry. We have 5 degrees neg camber. You can have too much castor, but I can't think of how it would cause mid corner understeer.

    Do you know the spring rate of the xyz, or could you find out? And do you know if its identical to the other coilovers permissible under the regs?

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    Click image for larger version. 

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ID:	101472 This is what i had do to get the extra caster, then adjusted the camber with slots in the strut housing. I'm wondering if the way it's installed is the cause of the understeer.

    Springs are 180x10.5 front and 180x9.5 rear.

    The shocks have been set to their softest setting so i can't have the front any softer. I'm happy with the way the rear react but the front is just crap.

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    That strut top is exactly how we have done it in the Swift, and it works great for us. I doubt that's your problem. Do you know your spring rates in pounds per inch, or KG per mm? The springs in the front of the swift are 7kg/mm.

    What tyres are you running? I presume there's a control tyre for the Excel series.

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    Registered User Stevil's Avatar
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    2mm tow out seems pretty extreme to me ??, maybe bring it back to 1mm total and straighten the rear to 0. Thats the setup that works for my Civic and alot of mates run it aswell. Go from there I reckon

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    Sprinkles i looked at the website i got them from, they have it listed as 6.3kg (350 pnd) front and 4.5kg and 250 pnd rear. Yes just running control tyres.

    Stevil rear is currently 0, i thought 2mm is ok for a track car?

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    Quote Originally Posted by Mai View Post
    Sprinkles i looked at the website i got them from, they have it listed as 6.3kg (350 pnd) front and 4.5kg and 250 pnd rear. Yes just running control tyres.

    Stevil rear is currently 0, i thought 2mm is ok for a track car?
    Ok, and what does the car weigh?

    Front toe really only affects your transient handling, ie initial turn in. I don't think that's your issue, and reducing toe out will make the turn in aka rotation less sharp. I think 2mm is fine, we run 1mm but have run up to 3mm.

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    Registered User hrd's Avatar
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    Your alignment is basically unchanged, and after changing the springs and shocks it runs wide. The changed handling characteristics are down to spring rates. To correct the understeer you either want a softer front or stiffer rear spring. Or a bigger rear swaybar. If you have the part numbers of the old King Springs you can get the spring rates, then match the F:R ratio with your coilover springs.
    Last edited by hrd; 30-08-17 at 10:33 AM.

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    Sprinkles - car weighs 1010 with driver

    hrd - i tried searching the part number of the king springs and they don't list the spring rates. The caster was the other thing that was changed which I am wondering is the problem. As the springs are a control item, is the only option I have is a bigger rear swaybar?

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    Quote Originally Posted by Mai View Post
    Sprinkles - car weighs 1010 with driver

    hrd - i tried searching the part number of the king springs and they don't list the spring rates. The caster was the other thing that was changed which I am wondering is the problem. As the springs are a control item, is the only option I have is a bigger rear swaybar?
    I had a read of your regs, it's a bit confusing, the suspension paragraph says springs are free, but then later it says if your car was log booked after 1 Jan 16 you have to use one of the suspension "packages". So you need to understand what is legal for your category. A stiffer rear sway bar, stiffer rear springs, or softer front springs, if any if these are legal they should be a step in the right direction. Otherwise try raising the front ride height. If you want go a bit more radical, try a bit of rear toe out, but be careful, it will be unstable.

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    Springs are free if you use spring shock combos, if you use coilovers you can only use the 4 listed 'packages'

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    Now that you have coilovers, have you corner weighted the car? I would suggest taking your car to Ken Graham at Accurate Suspension at Woodridge. I expect he has done work on a number of Excels by now, and knows what works.

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    Haven't corner weighed the car yet, aim was to get the baseline and work from there.

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    I have an Excel thats getting slowly built. Ive heard so much conflicting info on the suspension packages. The SA guys all preffered the Supershock packages but then a few Vic guys (top 10 iirc) went over & beat them running the Xyz packages (less than 1/2 the cost of the shockworks gear...). Then i hear that a few top 10 NSW Qld guys are running the king spring / whatever strut combo wuth great success. Fuct if i know.....
    Spring rates on the coilover packages are fixed from the supplier so the only advantage i can see with coilovers is ride height. Are the tyres sticky enough to benefit from such high spring rates (again, just based on what suspension people have told me)?
    Any info I've seen on cheap coilover "adjustability " is that its bullshit with the measured differences being all over the place from each strut and only the top end Bilstein & above showing any advantage.
    My thoughts are that using the king sprjng option you can at least try different strut brands to get a combo that might work. Thoughts?

    Sent from my SM-T819Y using Tapatalk

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    snelens what I've learnt from my limited experience is that the king springs that are off the shelf aren't stiff enough as I can see the tyre rolling over to the other edges. You could go the king spring route but you would want custom made ones and still have no height adjustability and you would have to slot the shocks for camber(i ran those offset camber bolts but even with spot welds to keep them in place i had one move on me). By the time you do all that I think you are getting towards the costs of the cheap coilovers and from what I've been advised the excels perform better with abit of rake.

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    Raise the rear?

    Definitely get it corner-weighted.
    Quote Originally Posted by brewdles View Post
    In short, some cunt at test and tune had a 250cc honda turning to 11ty and it sounded porn. Do that.

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    Quote Originally Posted by snelens View Post
    My thoughts are that using the king sprjng option you can at least try different strut brands to get a combo that might work. Thoughts?

    Sent from my SM-T819Y using Tapatalk
    To my mind it would depend on if you could get the full permissible 4 degrees of negative camber. If so, I would go for the freedom allowed with non-coilovers, if I could dial in plenty of camber, and a bit of extra caster.

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    tryhard snelens's Avatar
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    Quote Originally Posted by Sprinkles View Post
    To my mind it would depend on if you could get the full permissible 4 degrees of negative camber. If so, I would go for the freedom allowed with non-coilovers, if I could dial in plenty of camber, and a bit of extra caster.
    Thanks Sprinkles.

    Yes of course the tops wouldn't be adjustable...can't recall anything about "bending" struts in the regs so maybe that could be the way?

    Sent from my Nexus 5X using Tapatalk

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    Quote Originally Posted by Mai View Post
    snelens what I've learnt from my limited experience is that the king springs that are off the shelf aren't stiff enough as I can see the tyre rolling over to the other edges. You could go the king spring route but you would want custom made ones and still have no height adjustability and you would have to slot the shocks for camber(i ran those offset camber bolts but even with spot welds to keep them in place i had one move on me). By the time you do all that I think you are getting towards the costs of the cheap coilovers and from what I've been advised the excels perform better with abit of rake.
    For sure coilovers look cool and are easier to set up, but once you've got a setup that works, you won't spend a lot of time making further adjustments. Tyres rolling over onto the edge implies not enough camber in the corners, this could be caused by insufficient static camber or too much body roll. Uneven tyre wear and a bit of understeer isn't necessarily a bad thing

    The bottom line is: Are your lap times faster or slower on the new coilovers? If slower, and your regs don't permit a softer front spring, maybe you need to think about putting the old struts back in and getting the camber adjusting bolts welded in properly.

    Corner weighting is done to get the car handling the same turning both left and right. Unless the car is understeering when turning in only one direction, corner weighting won't help you at this point.

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    Quote Originally Posted by snelens View Post
    Thanks Sprinkles.

    Yes of course the tops wouldn't be adjustable...can't recall anything about "bending" struts in the regs so maybe that could be the way?

    Sent from my Nexus 5X using Tapatalk
    My read of the suspension paragraph is that the whole unit is free. So you could do whatever you want to it. Another option, see if you can slot the bottom mounting holes in the strut where it bolts up to the hub, to lean the hub inwards, and get camber that way. You want to properly weld the nuts onto the foot of the strut once you have got the position right, you can see Mai has had trouble with them breaking loose and moving, we have had the same issue on the Swift from not welding them thoroughly.

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    As mentioned above snelens, if you go the strut spring combo you should slot the struts to dial in the camber. Also don't use the off the shelf king springs, they aren't stiff enough.

    Sprinkles, there was sufficient camber as i was running the max allowable, it was definitely from body roll which is why i went the coilover route. I understand what you are saying about coilovers better just because they are coilovers but the control overs had to tender to be a control suspension and are proven to work with other competitors.

    Coilovers are slower, but to the point where it's well out of where it should be performing, I believe it's the way I've installed it trying to get more caster but I don't have enough time to make too many changes to get it at least in the operating window it should be before the next race.

    Steps look to be change the plates back to horizontal, if that doesn't change the handling then raise the ride height abit, final step will be to throw in the old spring strut setup.

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    Quote Originally Posted by Mai View Post
    Steps look to be change the plates back to horizontal, if that doesn't change the handling then raise the ride height abit, final step will be to throw in the old spring strut setup.
    Sounds like a sensible approach. Please let us know how you get on.

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    Quote Originally Posted by Sprinkles View Post
    Sounds like a sensible approach. Please let us know how you get on.
    Will do, next event is in two weeks on the 16th.

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    Just a follow up on what's happened, I went to a timeattack day yesterday and I flipped the plates to the horizontal to drop the caster which improved it a little. The front end wasn't skipping as it under steered but was still having trouble going wide as the outside gets loaded. I raised the car and turned up the dampening on the rear which helped a little but car was still understeering badly. I went to the general practice today with my old king springs and shocks with the intention of pulling out the coilovers as I had nothing no more answers.

    I was about to pull off the coilovers when I notice some faint marks on the slots of the coilovers where they bolt onto the uprights. Seems the wheel alignment place didn't tighten up the bolts fully when they did my alignment, so after tightening the bolts I took the car out it's now finally handling well. I was almost going to pull out of the race on the weekend but now that it's been sorted I'm excited about the race

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    Registered User PXL265's Avatar
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    Frustrating when shit like that happens, but glad it's sorted.

    I know you shouldn't have to,, but you really need to check any work done on your cars twice to make sure it has been done....

    Hopefully have a great weekend.

    Sent from my XT1635-02 using Tapatalk

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    So if I understand this, you didn't have the neg camber you thought, is that right? If so and you have now pushed the struts in to get the camber right, you should re-check your toe in. Let me know if u want some pointers on how to DIY your wheel alignments. Better, more reliable and cheaper than shops
    Last edited by Sprinkles; 15-09-17 at 09:42 PM.

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