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Old 01-22-2003, 12:05 AM   #331
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FJ: Last time I tried this config, the car was impossible to drive, both on and off power. Oversteering all over the place.

It was a TRF414M using 1 degree toe in blocks. Evidently, the -1 and -2 hubs have mounting points of different heights for the links, and I did not check that after swapping from the -2 to the -1s (the -1 hub has a lower mounting point, causing the projected wishbones not to converge inboard.)
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Old 01-22-2003, 12:25 AM   #332
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Alvin - so if i want to raise or lower the roll center what could i do??any suggestions??thanks
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Old 01-22-2003, 01:01 AM   #333
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Alter the links on perhaps your shock tower so that they will meet... it is more accurate if you do a three y=mx+c calculations to really calculate the static roll centre. Are you certain your car comes with the links as such?

I was having a bout an extra 0.7mm shim (approx) and my car already went awry....
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Old 01-22-2003, 01:08 AM   #334
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alvin - i can raise the inboard link with spacers but i cant lower it anymore....but i can raise the outer link......for my front end the top and bottom link are also nearly identical as the rear and if i raise the outer link the car feels lazy to turn .....ok if i have the front links parallel and the rear one are like the ones in the pics....is that a high front/low rear roll center or otherwise....and by by the way to make a car aggressive in steering do i need a higher front or lower
thanks
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Old 01-22-2003, 04:39 AM   #335
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At present, you don't really have a roll centre (there is probably an instantaneous one, but not like is usual with a double wishbone).

You need to raise the outer mounting position, until the link is actually parallel with or angling towards the wishbone. Then you'll have a proper basis to work on your suspension from.

Once you've got to that stage, a lower roll centre occurs when the links are close to parallel. A higher roll centre occurs when the links are more angled with respect to one another.
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Old 01-22-2003, 05:35 AM   #336
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FJ: As sosidge says, you do not have a roll centre based on that diagram... however, it is possible to have short angled links that have a lower rc compared to the those parallel: when it comes down, you need to do the maths to accurately calculate the roll centre.

Aggressive? Perhaps you can explain what you are looking for? If you need more response, you try a softer oil, lager pistons etc. Probably make the car react faster. RC adjustments can also make the car more "aggressive"... for example a car with a high roll *axis* will feel more aggressive than a car with a similar parallel axis but of lower height. But these are generalizations of course. I've driven loose cars where the owners termed it a pushing ride... i could be wrong of course.

My 414m for example running the exact same setup with say 40wt oil but changing the pistons between 2 and 3 holes makes a whole new car.
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Old 01-22-2003, 05:55 AM   #337
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ok guys! sorry i had a brainfart when i drew the earlier pictures....the links are in fact parallel to each other...for now i have a high front low rear roll center.i'm already on 40wt oil with 3hole piston(stock uses 2 hole)....i'm looking for quick response on entering....using about 4deg caster....i also feel using stiffer spring has better initial turn-in softer spring seems lazy on turn in...also on fulltime oneways....

what effects will i get when having the car with low front high rear roll center??

alvin- what is roll axis??

thanks
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Old 01-22-2003, 06:33 AM   #338
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Roll axis is the line connecting the front & rear roll centres.

front high rear low. Is this accurate? I was told this is similar in concept to the 1:1 scale old style Mini Cooper. It had to run a hard rear roll bar to compensate.

Do you feel you need to let off a lot of throttle halfway/corner exit? Usually i get a midcorner to exit understeer car with such a setup, but the response is good, and the entry is very sharp.

Quote:
what effects will i get when having the car with low front high rear roll center??
car would not be as "responsive", but front end is able to have grip throughout the corner. If the difference is too large you might expect some late corner oversteer (too much weight transfer to front; rear does not roll, per se) Reponsive is a personal judgement thing. Some complain the car is too twitching with a high rc; others the opposite. It is driver dependant. Me if i need more twitchness I'd adjust the damping.
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Old 01-22-2003, 07:01 AM   #339
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Alvin - thanks for the reply....i'll try to do some more setting up with the car and post here on what i did....high front low rear roll center i dont need to release any throttle...i.e at MS the turn going to the long straight i could power it up all the way after the 180deg turn(u-turn) going into the straight
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Old 01-22-2003, 07:59 AM   #340
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That corner is rather wide.... if you wanna try more challenging place to setup, rc speedway. The sweeper on the right and tight exit on the left makes for both semi-technical + high speed... the terrain is also very interesting, varying between smooth, and hyper bumpy (i've had my car bottom out on the edges of the straight at RCS)

now pondering if i should get a alex barracuda or an Ova T4 to run. Very bored with setting up my 414... i'm no racer. I just enjoy suspension setup.
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Old 01-22-2003, 08:17 AM   #341
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i thought that was what u meant...i meant mid to exit oversteering...for small tight hairpins its difficult to to see whether it will show exit oversteer symptoms....for wide corners like that it's easier to see whether the front will roll more in the corner thus creating an oversteer effect when more weight is on the front tires....do i make any sense here...

go get the Cuda

Last edited by fReShJiVe; 01-22-2003 at 08:20 AM.
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Old 01-22-2003, 11:06 AM   #342
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alvin, mini coopers do not have rear roll bars, the rear suspension is not wishbone its trailing arm.

sanj
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Old 01-22-2003, 05:33 PM   #343
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Quote:
Originally posted by schumacher
alvin, mini coopers do not have rear roll bars, the rear suspension is not wishbone its trailing arm.

sanj
i think he said 1:1 scale which i suppose is full scale real car
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Old 01-22-2003, 08:45 PM   #344
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hm......
thats what i did to rollcentre freshjive ........ car was ok .... just a bit on the very loose and aggerasive side .... on and off power
are u also on a 414m ?

fixed the too much overstear onpower problem by limiting the rear droop ( less downtravel)
and increasing the front droop ( more front downtravel)
and also switched the c1- c2 hubs to opposite of manual
now its quite ok and nice a slight overstear onpower and offpower ....

forgot to add it was on 2 deg hubs


hehehe alvin .....
yep i also like suspension setup ....

Last edited by imataquito; 01-22-2003 at 08:59 PM.
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Old 01-26-2003, 09:06 AM   #345
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Default More tuning Qns

What are the effect of increasing ackerman angle???
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