jos
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| posted on 28/2/06 at 08:57 AM |
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Twitchy back end
The car I mean.
Ive just adjsuted the camber on all 4 wheels to be as close to vertical as possible with just a little negative camber. Ive also adjusted the toe on
the front to be as close to parallel.
My problem is this. Whenever I change up a gear the back end gets twitchy, and I would like to get rid of the twitchyness as its quite unnerving.
I'm guessing I need more negative camber on the rear and possibly a bit of toe in so that i dial out some of the resposiveness to steering
(created when taking one hand off the steering wheel during gear changes)
Anybody had similar experiences and how did you solve it.
.: Motorsport / motor racing circuit / track wall art Apex Traxs :.
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donut
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| posted on 28/2/06 at 09:28 AM |
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If the back end was ok before i would re adjust the back to near what it was and see if that helps.
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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jos
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| posted on 28/2/06 at 09:35 AM |
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What I had before was negative on the offside and positive on the nearside. Not idea I know but I might put the off side back to more negative &
adjust the nearside to match
[Edited on 28/2/06 by jos]
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richijenkin
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| posted on 28/2/06 at 10:20 AM |
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for £50 the car repair garage oposite me will sort this for you. Even with the proper tools it took him 3 times to get the front wheels aligned
properly. Definetely worth it knowing its all running how it should.
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smart51
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| posted on 28/2/06 at 10:27 AM |
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negative camber on the rear wheels reduces oversteer whereas positive camber promotes oversteer.
Im not so sure about toe but I think a small amount of toe out at the rear reduces oversteer. I think that the theory is that with toe out, the
friction with the road is trying to turn the wheels out more, loading up the bushes in the suspension. When you turn into a corner, the loading gets
higher. If you have toe in, the friction tries to turn the wheels in more and so when you turn in, the outer rear suspension changes loading from toe
in to toe out causings a momentrary change in wheel angle. I think.
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RazMan
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| posted on 28/2/06 at 12:37 PM |
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I have to agree with richijenkin - a four wheel lazer alignment will give you the assurance that everything is pointing in the right direction and the
ride quality and roadholding (and therefore safety)will be enormously improved.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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NS Dev
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| posted on 28/2/06 at 01:19 PM |
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More to the point..........what rear spring rates do you run and what settings are your dampers on???
Classic twitchiness on these cars is too stiff on rear springs and dampers.
You want it as soft as you possibly can get away with.
As long as your rear springs are no more than 170lb and you have avo/protech/gaz/spax rear dampers, then back them off to minimum ( 0 clicks ) and try
that, then add clicks gradually.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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jos
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| posted on 28/2/06 at 02:02 PM |
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Just went with the MAC#1 coilovers (GAZ I think) with the reccommended sprinds for a pinto build.
I'll try adding toe in to start, then if that doesnt work I'll try toe out. Then if that doesnt work I'll reset to parallel and
back of rear dampers
[Edited on 28/2/06 by jos]
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scutter
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| posted on 28/2/06 at 02:36 PM |
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I can recommend checking your damper settings, after spending £120 on a pro chassis set up, my car was still twitchy then realised the dampers where
still set in the mid position they're now set 6 clicks off full soft, result the cars now a joy to drive.
ATB Dan.
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jos
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| posted on 28/2/06 at 02:51 PM |
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From memory I think theyre set to 3 clicks so I'll be interested to see what happens when I fiddle some more
During normal driving its lovely. Its just when I change gear that it gets twitchy
[Edited on 28/2/06 by jos]
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Syd Bridge
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| posted on 1/3/06 at 09:21 AM |
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You might try being a bit less aggressive when you come back onto the throttle. ie smoother. Sqeeeeeze it on, dont jump on it. 
Syd.
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JoelP
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| posted on 1/3/06 at 09:27 AM |
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mines a live axle, so i have no choice about rear wheel settings, but i found a modicum of toe in on the front helped straight line stability, though
to be fair having a quick rack and not much self centering its always going to be a little unforgiving at the front, when steering one handed!
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jos
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| posted on 1/3/06 at 10:26 AM |
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Its coming off the throttle that the twitchy ness is present.
I could understand it spinning up when power is reapplied but when its let off ?????
I added toe in (1 turn) dont know about degrees or mm's last night but it started snowing and was -ve deg C - not the best conditions to try
setting up a twitchy back end.
Ho hum I'll just have to wait for the roads to clean and warm up before trying my new settings.
BTW my rear dampers were set to 3 clicks off softest.
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Mark Allanson
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| posted on 1/3/06 at 09:31 PM |
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I set mine up on a laser Hunter system (I have one at work), I took my time (4 hours on a Saturday) and really pleased with the results.
I have:
Front
Toe -0°10' Total
Castor 5°40'L 5°50'R
Camber -0°30' each side
Rear (Capri live axle)
Toe -0°12' each side
Camber -0°25' each side
Not gospel, but a good starting point.
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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jos
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| posted on 2/3/06 at 08:26 AM |
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Getting that precise with a spirit level, some lengths of string and a tape measure is going to be difficult.
Where abouts are you and any chance I can use your rig one weekend to do the same.
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smart51
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| posted on 2/3/06 at 09:07 AM |
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You could take it to a race car setup place. They should get it better than your local tyre fitting place. They should even be able to set up the
corner weights too. I guess you'll have to tell them what angles to set your wheels to though.
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jos
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| posted on 2/3/06 at 10:17 AM |
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Yeah richijenkin has recommended a place thats local to me.
Id like to do the setting up myself but dont have the equipment.
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OX
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| posted on 5/3/06 at 12:44 AM |
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Tudor Motor Body Repairs
Shrewsbury Road
Market Drayton Shropshire TF9 3EW
Tel: (01630 652596)
kevin is the man you want to speak
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blueshift
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| posted on 5/3/06 at 03:59 AM |
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I may be talking fart, but I seem to remember rear toe-out can be quite dangerous. At least, on an mx5.
if you think about it, as you approach the limit of grip, the outside wheel is doing a lot more of the gripping, and it's steering out slightly,
trying to turn the back out.
As previously pointed out though, may be talking fart.
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jos
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| posted on 5/3/06 at 09:42 AM |
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Cheers for that OX Richi gave me contact details for them on wednesday and I went up and spoke to Kevin on Thursday evening.
They seemed to know both of you VERY well. Any ideas why????
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OX
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| posted on 5/3/06 at 08:16 PM |
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Iv known kev for over 16 years,wouldnt take anything to anyone else .i used to pop down and put all the fairing panels back on any bikes that
they'd resprayed and he used to touch any panels up for us that we'd caught on our bikes.he does a top notch job on anything he
touches,he's just restored my mums SA Tourer and it looks brand new 
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DarrenW
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| posted on 10/3/06 at 03:11 PM |
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Jos,
Here are the settings Mark recommended for me:
Tyre pressures critical 18 psi,
front shoxs 7 th click
rear shoks 3 rd click
Make sure your suspension bolts are just tight enough, ie you have movement,
Ride height, front shocks 15 threads showing
rear shocks 8 threads showing
toe in -1.5°
caster maximum on mushroom
camber 0° to - 1° (check it with a blumb weight,)
Im yet to set front toe. Have rear camber approx between 0 and -0.25deg. Im going to set to -0.5. For pure race use they recommend -1deg.
Using the above settings mine isnt too twitchy. I do get some spin changing down the box sometimes when road conditions are crap. on hard acceleration
and sharp up shifts i can get the back wheels to spin up and step out a touch - again road conditions are not good so i can put this down partly to
poor traction.
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jos
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| posted on 10/3/06 at 09:17 PM |
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Ive set her up as close to those settings taking into account my smaller wheels & lower ride height, and I seem to have cured the problem.
I reckon Ive been running with too grippy front tyres, and not grippy enough rear tyres. Ive just had a set of Yoko A539's put on the rear and
have moved the budget tyres from the rear onto the front. Previously I had been running the budgets on the rear and bald A021's on the front
and I think the twitchyness was so prominent because the fronts were gripping so much and reacting to me being too violent on gear change.
Since putting the budgets on the front & new yokos on the rear Ive got rid of alot of the nondesirable twitchyness and will have the front budget
tyres replaced with decent tyres, probably another pair of 539's as soon as I know how my efforts in setting up camber & toe have changed
the wear rate on the front.
Problem solved. Thank you all for your help.
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