How Not To Modify Your 205's Suspension...

[Cameron 16]

Load transfer under braking is completely separate to the RC height though, it's a function of CG height and wheelbase so if anything you're getting less by having the vehicle lowered.

 

Running lots of static camber will be an issue for braking and possibly for tyre temp gradient, true.. my 3 degrees up front worked very well though and I certainly wasn't losing out on the brakes! It would have been even better if I'd have got round to fitting my 23mm rear ARB.

 

Edit: Also, another good thing about low RCH is you load the tyres in a way they prefer. Having a high RC means you have a lot of shear force at the contact patch, which is bad for tyre life and grip; having it low (and gaining your roll stiffness back with a bigger front ARB) means you load them vertically, which they like a lot more.

 

If I had another 205 track car, or still had my black one, I'd like to try it with the settings I had - very low, 3 deg -ve front, 2 deg -ve rear, 350lb front springs and 24mm torsion bars - then fit the 23mm rear ARB and a slightly thicker one up front. I reckon that could be a very good combination.

Edited February 24, 2012 by Cameron

[oli-pug 6 2 Cars]

 

If I had another 205 track car, or still had my black one, I'd like to try it with the settings I had - very low, 3 deg -ve front, 2 deg -ve rear, 350lb front springs and 24mm torsion bars - then fit the 23mm rear ARB and a slightly thicker one up front. I reckon that could be a very good combination.

 

I look forward to tinkering with it be interesting to see what difference a proper cage makes to all my old bits ill transfer over actually.

 

I might go with a 309 front arb or have an adjustable one made to try and get the front tyres working better like you say. Bumpsteer reduction is a priority along with machined rear arms for the camber and parallel toe, maybe a hint of toe out if i feel brave

[Anthony 1,003]

I suspect that it will be much better with the higher spring rates, but certainly on modest spring rates I personally found a 309 front ARB to be detremental - just seemed to take all the weight off the inside wheel and meant that it would understeer on-throttle and/or spin up the inside front wheel far too easily. That was running with an uprated rear ARB too, and would have almost certainly been far worse without.

 

With the 205 front ARB refitted, it both had better on-throttle balance, and had far more traction.

 

I would have liked to have tried removing the ARB completely and using stiffer spring rates to compensate as a comparison, but not having coilovers made that difficult to do on a whim.

[Cameron 16]

I think the thicker front ARB would only work well with a low car though, if you had a more "sensible" ride height then you may well have been better without it.

 

Bump steer is the big thing you need to sort out Oli, if you're going to have it sitting low. Mine was very nice in the corners but was a bit of a handful on the straights!

[welshpug 1,657]

been in a 306 rallye without arb's, epic tripoding as it was on comparably soft lowering springs :lmao

[Paul_13 212 1 Cars]

I agree with the above comment about the 309 front ARB on a 205. Always felt it was trying to lift inside wheel and it understeered everywhere. That was at -50mm(ish) drop. 205 arb FTW

[Cameron 16]

As I said though, the thicker front ARB is combined with a low ride height and stiff rear springs and ARB. Telling me you had different experiences without an identical setup is like telling me what you had for dinner yesterday.

[Rippthrough 98]

If it's got a nice low ride height and stiff springs the front arb can feckorf anyway

 

Or use it to mount a 3rd heave damper/spring off and get the thing even lower...

[petert 588]

As I said though, the thicker front ARB is combined with a low ride height and stiff rear springs and ARB. Telling me you had different experiences without an identical setup is like telling me what you had for dinner yesterday.

 

I had chicken. I have 350lb front springs and 23mm torsion bars. My next step is to go smaller or even remove the front ARB, not put a heavier one on. I don't think my car can go any lower.

[Cameron 16]

Mine was definitely worse without the front ARB when I tried it, body control was poor to say the least and both grip and turn-in suffered as a result. That was with std rear ARB and 24mm bars, would have been marginally better with a thicker rear ARB but I'm not convinced the difference would have been enough.

Edited February 27, 2012 by Cameron

[kyepan 291]

Load transfer under braking is completely separate to the RC height though, it's a function of CG height and wheelbase so if anything you're getting less by having the vehicle lowered.

I don't agree.... theoretically perhaps what you say is true, but in karts, with very low CG and RC, and no suspension, all you have is weight transfer, and a bit of chassis flex to lift the inside rear.

 

Edit: Also, another good thing about low RCH is you load the tyres in a way they prefer. Having a high RC means you have a lot of shear force at the contact patch, which is bad for tyre life and grip; having it low (and gaining your roll stiffness back with a bigger front ARB) means you load them vertically, which they like a lot more.

 

Can you explain this in more detail, define sheer force and it's direction.. As opposed to vertical load

 

If I had another 205 track car, or still had my black one, I'd like to try it with the settings I had - very low, 3 deg -ve front, 2 deg -ve rear, 350lb front springs and 24mm torsion bars - then fit the 23mm rear ARB and a slightly thicker one up front. I reckon that could be a very good combination.

 

I've tried a couple of combinations and stiffer rear anti roll kept the car tractable coming out of corners with the power down.. 24mm

[Cameron 16]

Karts and 205's are a little different though, don't you think? Chassis flex isn't what lifts the inside rear on a kart, it actually does the opposite (think about how torque is applied to the chassis by the front & rear axles) it's the front suspension* geometry that lifts the inside rear wheel. Wheel lift doesn't happen because it's favourable either, it HAS to happen so the car can corner with a solid axle. Not wondered why an F1 car doesn't cock a wheel mid-corner?

 

Just for you: Tyre shear force - horizontal force at the tyre contact patch in line with the axle that acts to shear the rubber across the road surface, brought about by the forces acting on the geometric roll centre. Good enough? If not, have a read of Millikens' Race Car Vehicle Dynamics.

 

I'm not going to comment any more on why people have had different results with non-identical setups. Tell me what you had for breakfast.

 

Edit: *I say suspension through force of habit, I mean steering, you get the idea.

Edited February 27, 2012 by Cameron

[kyepan 291]

Wheel lift doesn't happen because it's favourable either, it HAS to happen so the car can corner with a solid axle. Not wondered why an F1 car doesn't cock a wheel mid-corner?

 

I am aware that the kart needs to lift the rear wheel to turn, and they have solid axels.. because I-race-them-all-the-time, thank you very much Cameron. The chassis's do flex, and chassis geometry is pretty critical to a kart behaving, get a bent one and you won't have a good day because it won't act predictably. Though you're right about the steering helping the turning (as far as the geometry is concerned) as you wind on the lock it also winds on loads of caster because the king pin is inclined back.

 

In karts, you are the suspension and weight distribution, bracing for breaking for example - if you don't make your upper torso ridged and back, you can't get the weight back on the rear wheels and stabilise the kart into the breaking.

 

TBH - throw all the theory you want over the fence, I know what i feel when driving, and the stiffer rear anti roll bar does work. I agree that less static caster should also work to make the car behave during heavy breaking and acceleration, how ever the toe angle and and reduced bump steer (standard height setup) have redressed most of the handling gremlins.

 

From previous experience, running with a bump steer modification is the best bang for buck, it was on the pulsar anyway.. totally transformed the way it turned in, tracked, through the corners, especially during transition back onto throttle and general front end grip..

 

Going back to the old old conversation, what really lets the pug down, is the inclination of the rear struts and the ratio they run. watch that sprint video of a colin satchel prepped shell with turreted rear, it's got zero understeer..

[welshpug 1,657]

 

Iasn Beecham, I can't remember if this was one of Colins chassis, might have been John Read

[Cameron 16]

I never said the chassis don't flex, I said they don't flex in the way you were thinking and that it was steering geometry that predominantly governs wheel lift.

 

This is what amuses me.. you've tried to go into great detail on the theory of why a roll centre needs to be raised early on in the topic, but the moment I use theory to explain myself you start the whole "CaMoron is all theory and no practise" argument again.

 

Theory is an important thing to understand in order to make the right changes, so don't poo-poo it like that. Sure you could tune the car by throwing parts at it and changing the settings here there and everywhere, but how long would it take you and how much would it cost? If you don't understand why what you've done has or hasn't worked then you haven't really got anywhere, you've just spent money and arrived at false conclusions.

[kyepan 291]

Sure you could tune the car by throwing parts at it and changing the settings here there and everywhere, but how long would it take you and how much would it cost? If you don't understand why what you've done has or hasn't worked then you haven't really got anywhere, you've just spent money and arrived at false conclusions.

 

Which is exactly why I wrote the initial topic! i'm glad we agree. I'm just saying that ignoring the empirical evidence would be silly! Just because people can't directly link what their arse and hands tell them whilst driving to a specific vehicle dynamic theory, doesn't make their feelings less valid.

 

if you get me.. "we're not computers, Sebastian, we're physical"

Edited February 27, 2012 by kyepan

[Anthony 1,003]

Theory is an important thing to understand in order to make the right changes, so don't poo-poo it like that. Sure you could tune the car by throwing parts at it and changing the settings here there and everywhere, but how long would it take you and how much would it cost? If you don't understand why what you've done has or hasn't worked then you haven't really got anywhere, you've just spent money and arrived at false conclusions.

Equally though Cameron, sometimes theory ≠ practice and that is something that you sometimes seem to have difficulty in comprehending/accepting judging from previous threads judging by the way that you'll argue until you're blue in the face with people that have actually done and have experience of what you're theorising about.

[Cameron 16]

So does tuning my own suspension based on my own conclusions not count as applying theory into practise? I suppose designing my own suspension geometry and settings from scratch then building it into a vehicle isn't valid either? Forgive me, I didn't realise it's only recognised when one of the "elite" members does something.

 

I don't mean to be rude or condescending, but maybe you should read the definition of what a scientific theory is. It isn't guesswork, it's laws based on observations that are accepted to apply to real life. Hundreds of thousands of race cars have been designed and built on theory alone and it always applies to practise. The only time it doesn't is when a factor has been overlooked. Your findings may differ from mine, but without running an identical setup in the first place how can you possibly expect to compare anything?

[kyepan 291]

Forgive me, I didn't realise it's only recognised when one of the "elite" members does something.

 

now hang on a minute.... lets not start slinging mud about cameron, i hope you're not directing that at me!

 

I'll make my point again slightly more bluntly, but please don't take any malice from this..

 

You're quite happy to quote theory at me(edit: which is fine i might add, learning is good), but when i tell you what i've done in practice and try and relate that to theory. you don't accept the practice, and bash me about the head with more theory until i have to ask for explanations, where by the tone gets a little patronising.

 

so, it comes across to others that you're not accepting peoples practical findings, and quite happy to heap theory on them until they are out of their depth. A good way of making people feel stupid and not helping the debate an awful lot, it's clear you know alot, and are happy to share your knowledge, this is all a good thing. Please just try and keep other people in mind as and when you choose to dish it out..

 

It's great your doing the scratch build, and good that you're posing theories, just go easy on what everyone else thinks, especially if they've not had the pleasure of three year suspension dynamics text book enema... he he. I had friends on that course, and they were all pretty nice chaps, if a little more laid back.

 

 

Cheers

J

Edited February 27, 2012 by kyepan

[Batfink 201]

I am aware that the kart needs to lift the rear wheel to turn, and they have solid axels.. because I-race-them-all-the-time, thank you very much Cameron. The chassis's do flex, and chassis geometry is pretty critical to a kart behaving, get a bent one and you won't have a good day because it won't act predictably. Though you're right about the steering helping the turning (as far as the geometry is concerned) as you wind on the lock it also winds on loads of caster because the king pin is inclined back.

 

In karts, you are the suspension and weight distribution, bracing for breaking for example - if you don't make your upper torso ridged and back, you can't get the weight back on the rear wheels and stabilise the kart into the breaking.

 

TBH - throw all the theory you want over the fence, I know what i feel when driving, and the stiffer rear anti roll bar does work. I agree that less static caster should also work to make the car behave during heavy breaking and acceleration, how ever the toe angle and and reduced bump steer (standard height setup) have redressed most of the handling gremlins.

 

From previous experience, running with a bump steer modification is the best bang for buck, it was on the pulsar anyway.. totally transformed the way it turned in, tracked, through the corners, especially during transition back onto throttle and general front end grip..

 

Going back to the old old conversation, what really lets the pug down, is the inclination of the rear struts and the ratio they run. watch that sprint video of a colin satchel prepped shell with turreted rear, it's got zero understeer..

 

Ian Beechams car wont have a front arb, but it has modifications to the roll centre, bump steer and front track width. The subframe is quite heavily reenforced as well. The rear (if kept with colins initial setup) will be relatively soft springs with the turreted dampers. Certainly works well for sprints. I've done trackdays without the front modifications and the car was very neutral but for my own driving style the rear needed to be stiffer. This will also be affected by tyre choice as well though.

[Cameron 16]

Look, you only need to scroll up to the top of this page to see why I way dishing out the theory - you asked me for it directly. I went to the trouble of giving you a nice concise explanation and what do I get for my efforts? A load of sarcasm and a complete brush-off of everything I'd just said. Maybe it's because you misinterpret what I've said to have a condescending tone, maybe it's because you're a smug git who likes to think he knows better, and the only reason you asked was not out of interest, but to try and catch me out.. who knows, but it's certainly the latter that comes across to me from your posts.

 

Oh that feels much better.

 

And for the record I don't try to baffle people with theory in order to "win" an argument, I do it because sometimes I feel that's the best way to explain what I mean.

Edited February 27, 2012 by Cameron

[Tom Fenton 1,542]

Crikey, would you speak to one another like this face to face? I doubt it.

 

Wind necks in please.

[EdCherry 34 1 Cars]

I stopped putting my own views/finding in this thread a while back for numerous of the above reasons.

 

I dont intend to defend anyone in any way here, but you have to see from cameron 'QUALITY' feedback is the key, data that you can rely on. This is my opinion coming from a roughly similar background as cameron.

 

Edited February 27, 2012 by EdCherry

[Cameron 16]

I'm going to take a leaf out of Ed's book, thank you and goodnight.

[kyepan 291]

Crikey, would you speak to one another like this face to face? I doubt it.

 

Wind necks in please.

Fair comment, although i thought i was being diplomatic- clearly a fail there.

 

Apologies if i have come across a bit harsh on you cam, I know you're trying to help, you just got my back up a bit.