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Old 02-06-2006, 01:59 PM   #12661
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Quote:
Originally Posted by trf racer
because springs shock position shock oil can all effect the type of roll center you have
stop it please i can't breathe, this is sooooo funny

Man you do have a good sense of humour
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Old 02-06-2006, 02:01 PM   #12662
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Obviously, you can make the car too stiff, but you can go too soft as well.The kit yellow springs are too soft IMO. At the moment I am running 16 or 18 pounds in the front, and 14 or 16 pounds in the rear - I don't think that's too stiff, but I agree if I ran "carpet" style springs it would be too stiff.

I have only had this car for 4 meetings so I'm still learning with it, but atm it is working better when it is stiffer.

Whether or not there is more stability is down to the driver and how they like the car to feel IMO. I don't like any car (off-road or on-road) to body roll - as it feels very slow and has poor reactions.

I try and set my cars up stiff so that they respond VERY quickly. They are not stable at all like this (opposite to your findings), but in fact VERY difficult to drive.

In the end lap times are all I go by - and I get better lap times when the car is stiffer even though it is much harder for me to drive. It could be just my driving style but that's what I've found so far.

Interestingly, the tuning guides from XRay, XXXMain, Losi, & various internet sources never agree about these things either - so I'm not sure if there is a definitive answer when it comes to the way these adjustments work.

I am currently using the JRXS set-up guide as it's findings are similar to mine.

My roll-centres are currently:

FRONT: 3mm under inside
REAR: 1mm under inside, 2.5mm under outside
BLOCKS: std - no shims

My comment are always based on asphalt or concrete only as I have no experience racing on carpet.
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Old 02-06-2006, 02:02 PM   #12663
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Don't forget though, indoors we generally seem to rely on the springs for roll stiffness (as well as for and aft traction), whereas outdoors, roll bars are used to increase the roll stifness, with the springs being softer for longitudinal traction.

My general outdoor setup uses tamiya yellows all round, and I tune the roll stiffness with the roll-bars

I don't know the entirety of your setup bender, would help if you posted it here (not having a dig). One I mean to say is, if your not using roll bars on your current set-up, this may be part the reason why the stiffer spring works
To put it this way... a stiffer spring (on a setup with no roll bar) would acheive a similar affect to a stiffer roll bar, in terms of roll stiffness.

I have deffiently found that a higher r/c works well indoors. I'm yet to try it outdoors though (damm uk winter) but I will try it.

And pete... the only things that affect your r/c are the arm positons.. not the other bits you mention

Also bender, you make a very good point. It suits you... if you feel it's faster than thats the best thing right? We're all different in the way we drive (Fab more than most ), so each of us is different.

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Old 02-06-2006, 02:06 PM   #12664
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Will post my setup when I get home (currently at work).

I don't use the roll bars atm, and I agree running a roll bar with a softer spring might be better than a stiff spring and no roll bar - but our tracks are very bumpy, plus the standard roll bar mounts have too much slop in them to make the roll bar completely effective.
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Old 02-06-2006, 02:16 PM   #12665
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Pete (TRF racer) please can you explain how stability relates to the interaction between the tyre and the ground, I fail to see how it does.
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Old 02-06-2006, 02:29 PM   #12666
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Quote:
Originally Posted by bender
Will post my setup when I get home (currently at work).

I don't use the roll bars atm, and I agree running a roll bar with a softer spring might be better than a stiff spring and no roll bar - but our tracks are very bumpy, plus the standard roll bar mounts have too much slop in them to make the roll bar completely effective.
Ok. One thig though, if your track is very bumpy, surely you would want the springs to be as soft as possible to absorb the bumps? You can increase your roll stiffness (and hence corner speed) with the roll abrs then... just a thought.
For roll bar mounts... Evo4 ones with a grub screw does take out a lot of the slop

HiH
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Old 02-06-2006, 02:37 PM   #12667
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Anyone know the dimensions for the 950 hub bearings please

Cheers, Chaz
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Old 02-06-2006, 02:44 PM   #12668
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Quote:
Originally Posted by TRF415boy
stop it please i can't breathe, this is sooooo funny

Man you do have a good sense of humour
maybe you can eligten me as to why all these things dont contribute to how you would set up your rioll center as to me you dont think it does.
everything effects each other.you say other wise?
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Old 02-06-2006, 02:45 PM   #12669
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Quote:
Originally Posted by Charles Godwin
Anyone know the dimensions for the 950 hub bearings please

Cheers, Chaz
9 mm OD 5 mm ID
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Old 02-06-2006, 02:45 PM   #12670
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Quote:
Originally Posted by Charles Godwin
Anyone know the dimensions for the 950 hub bearings please

Cheers, Chaz
5MM Inside Diameter, 9MM outside diameter, not sure about width, maybe 4mm?
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Old 02-06-2006, 02:46 PM   #12671
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Thank you, would these ones fit then ceramic ones , click the drop down bit , also found these ones Corally CR1151 here they are , just wondering as i need these for next week

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Last edited by Charles Godwin; 02-06-2006 at 02:56 PM.
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Old 02-06-2006, 02:47 PM   #12672
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Quote:
Originally Posted by TRF415boy
Pete (TRF racer) please can you explain how stability relates to the interaction between the tyre and the ground, I fail to see how it does.
ok,how can one man be out to get another one sooo much lol.
ok, you have grip on one side and stability on the other.
if you produce too much grip,you grip roll,an inheret of less stability.
and vice versa.easy?

you seem to be on first name terms,may i have yours as i asume we may have met some were?
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Old 02-06-2006, 03:09 PM   #12673
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Quote:
Originally Posted by trf racer
maybe you can eligten me as to why all these things dont contribute to how you would set up your rioll center as to me you dont think it does.
everything effects each other.you say other wise?
pete, roll centre is calculated via the angle of the suspension arms and links. The other bits control how the roll centre moves...
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Old 02-06-2006, 03:48 PM   #12674
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Quote:
Originally Posted by TryHard
pete, roll centre is calculated via the angle of the suspension arms and links. The other bits control how the roll centre moves...
i know how roll center is calculated.
but it interacts with every other setting yopu have on the car.
the way i adjust it is how ive said above when trf415boy laughed.
is there a wrong or right way to adjust it?
surely its all personal preference and at the end of the day there isnt much point in people saying what does it do if all we do is have this debate on it,ive tried it,i know what works and what doesnt work for me in every situation i have tested now.
and i suppose i cant be much off as i made the a main at carpet wars 2 day and last weekend.
if iam wrong then fair enough but i will still adjust my roll center how i do now.
iam sorry if iam wrong hehe,have to agree to disagree.
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Old 02-06-2006, 05:05 PM   #12675
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He he I saw Ed calling you pete so I took the liberty of doing so aswell, we have both raced at Stafford mod national (what a crap week end that was for me) but I don't think we spoke there.

Anyway I think you are getting very much confused. grip is grip, lack of grip is lack of grip. A car can have a lot of grip and be unstable, or lack grip and be unstable, same goes with it being stable. Stability relates to the way the car handles, we say an unstable car to be oversteering, and a stable to be understeering or neutral.

Then there is the amount of grip your tyres produce. We can decompose it in two : lateral grip and forward/aft grip. The former is commonly refered simply as grip, the later as traction.

The amount of grip that a given tyre will produce depends on the vertical force applied to it. The higher the force the more the grip, this follows a linear slope, until the tyre limit is reached. When it is reached the grip decreases drastically.

And so lateral grip in corner depends on how much vertical force is applied to the tyre. This is a relation between the roll centre's position, the centre of gravity's position and the stiffness of the suspension. In general the stiffer the springs, the higher the force, until the tyre limit is reached, in which case the tyre will lose grip all of a sudden.

A good technique to find the best springs is to try and go stiffer and stiffer until the car starts to loose grip unexpectedly, then go back to the stiffness below. However, this will give a very edgy car so you have to make sure you can actually drive it. A car with soft springs will have more give and allow mistakes, it will also react slowly, a stiff car won't allow mistakes and will react quick.

This is for a given roll centre, raising the roll centre will have a similar effect on grip than softer springs, but without the loss in reaction time. The car will also have less tendancy to slow down in corners (good for stock, not that good for mod on technical tracks). So when using soft springs a higher RC might help with transitions.

A special case is when using way too hard springs, then the springs prevents the car from rolling, which results in the outer tyre not being as loaded as you'd expect and actually loose grip. Some people use this phenomenon on high grip carpet, sometimes along with high RC, and it does help with grip roll but makes the car very edgy. I think this is why a lot of people say if you grip roll then go harder on springs, and i think it's the wrong method. As TRF Racer said, to prevent grip roll going softer is the easiest way, raising the RC is another way, angling and shortening camber links also helps.

Roll bars are a bit of a gamble game for me. Sometimes they decrease grip and make the end of the car concerned more progressive, sometimes they increase grip. They do though always make the car transition more slowly. On buggies you'll hear people tell you to use roll bars with softer springs on bumpy tracks. I have tried a soft setup with roll bars, a harder setup without the bars and then with the bars round ashby (quite bumpy track), and the harder without bars was the fastest.

I hope I didn't lose you guys, good efforts to those who have read it all.
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