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Suspension and Alignment Advice
https://www.ausmini.com/forums/viewtopic.php?f=2&t=79640		 Page 1 of 1
Author:  jme [ Sun Dec 23, 2012 4:07 pm ]
Post subject:  Suspension and Alignment Advice
My mini currently has bad torque steer and bump steer. It also has bad pitch front to back under acceleration or braking. Is there anything I can do about it from an alignment perspective?

The car is a 1275 with a quaife ATB LSD, adjustable lower control arms, Spax adjustable shocks on the front and hydro suspension.

Height is about three and a half fingers, toe front and rear is set to about zero, 3 degrees caster, 1.5 degrees camber front and rear. Adjusting the shocks to near max definitely helps the pitch.
Author:  TheMiniMan [ Sun Dec 23, 2012 4:16 pm ]
Post subject: 
The Hydro will continue to plague you with bump-steer issues (that`s what you were talking about when you said torque steer etc)

With Hydro & some power--> the front will always lift & drop (pitch & dive) & until you can sort that, you will continue to have poor tracking (Bump steer)

If you intend to keep the hydro then the best bet is to fit decent double-action shocks on the front (like Koni reds or similar) add some restrictors in the joins of the hyrdo pipes to the hoses (small brass washer with small hole drilled into it) to slow the flow of juice (front-rear)

& if you could find genuine "Competition" Hydro bags somewhere (good luck with that) then they would help too (if they weren`t all stuffed from age/wear)

so,, """THEN"""" you can attack the """"steering rack position & ride height""" (as a package) to reduce the bump steer some more if you like :-)

But,,, please make sure everything is tight & no play & all solid & adjusted correctly before assuming all what i said is needed,,, there may very-well be some issues with play & looseness & miss-alignment that i can`t see through my computer screen :-)
Author:  jme [ Sun Dec 23, 2012 4:29 pm ]
Post subject: 
Thanks for the quick reply.

I actually have both torque steer and bump steer.

I have not driven a front wheel drive with an ATB diff, is torque steer normal for these?

I really like the ride of the hydro so I'd rather not get rid of it.
Author:  drmini in aust [ Sun Dec 23, 2012 5:42 pm ]
Post subject: 
Mine is hydro (with about 125HP at the crank) and it doesn't do that. I only run a stock diff in it though.
I found putting rear comp hydro bumpstops on helped the pitching a lot. Still standard conical ones at front. The comp front ones jack it up too high unless you are going rallying.
Also, @ 3-1/2 fingers I reckon yours is a bit too high.
My front shocks are Pedders reds (same as Gabriel red riders I think) and they've done 100,000 miles now.
Author:  Lillee [ Sun Dec 23, 2012 8:50 pm ]
Post subject: 
I too don't have major problems. Might I suggest checking out how slack your steering is? Is there any play in the steering?
Author:  TheMiniMan [ Sun Dec 23, 2012 9:16 pm ]
Post subject: 
jme wrote:
Thanks for the quick reply.

I actually have both torque steer and bump steer.

I have not driven a front wheel drive with an ATB diff, is torque steer normal for these?

I really like the ride of the hydro so I'd rather not get rid of it.


yeah i think you`ll find that once you get rid of the pitching & diving that you`ll have reduced the toe changes ,,, with all the ride-height changing as you accelerate & decelerate, the toe changes dramatically because of it & coupled to the steering rack positioning,,, makes for quite a bit of bump steer (which is mostly what you`re getting when accelerating) Toreque steer would be very slight indeed (as with most minis with fair power

if you had ,,, say,,, over 100hp & some terribly offset rims & real tight LSD etc etc etc,,, then maybe there`d be an argument for excessive torque steer to banter about with

but if you have (as you say) a Quaife type diff & mild road mini power,,, then my suggestion would be that you have more of a bump steer problem simply caused by the dramatic change in toe setting during all the excessive ride height changes that your car is going through

bump steer is effective simply upon suspension travel movement,,, not just hitting a bump

if you corner , then the suspension on one side squats & the other side droops,,, you have now got changes in ride height which has influenced the bump-steer,,, a simple geometry problem inherent in most minis

my race buggy (for example) i have kept it fairly soft in suspension as there is little weight ,,, but it still moves about because it`s fairly soft so you`d think i`d have some bump steer too right?

but it has almost Zero bump steer,,, no mater what you do with suspension travel it just remains fairly true with it`s toe :-) Good ey? :-) & that`s because i positioned the steering rack to where it was at it`s best to suit the ride height & suspension arm geometry, effectively placing the rack ball-ends in the right spots

:-)

Like i said earlier---> if there`s no play in there Anywhere,,, no loose steering arms???... no rack play???... No worn/sloppy bushes???... no loose steering rack mounting u-bolts???...etc

then i`d look at trying to reduce the excessive suspension travel (pitching & diving) before you do anything,,, sounds like your hydro bags are pretty stuffed ... & maybe those spax may not be doing much either by the sounds of it???

Normally Spax are horribly stiff things for road cars ,,, ah well,,, sorry i can`t help much more than that... once you fix your main problem with the pitching & diving--> i feel you will find very little torque steer left to "torque" about :-)
Author:  mickmini [ Mon Dec 24, 2012 10:46 am ]
Post subject: 
I agree Matt, my 113ft/lb through a cone LSD (effectively locked with low differential torque -i.e aiming straight ahead) has very little torque steer, and very little bump steer. Admittedly i only drive on "smooth" race tracks, and it is a dry suspension, but everything is tight, the spax are not worn out, bushes are good and all the alignment was set up by Greig at Mini Classic. The bump steer is only as bad as the Mini geometry makes it, I barely notice it because I am having too much fun!

Trying to exit a corner with power on makes it want to go straight ahead, but this not what torque steer is.

cheers
michael
Author:  jme [ Mon Dec 24, 2012 5:11 pm ]
Post subject: 
Cool, thanks for your replies.

I have set the damping on the shocks to maximum, it has improved it, I will have a go at lowering the car to three fingers and see what that does.

Is there anything I can do with the alignment settings to reduce the effect of bump steer?
Author:  TheMiniMan [ Mon Dec 24, 2012 8:41 pm ]
Post subject: 
wel;l,,, you could possibly try to assess the co-relation of the suspension lift in the front whilst with power on,,, then take the toe measure whilst the front was compressed like on back-off with brakes on (not as much of the time right?) so you could attempt to land your travel setting in with your toe to keep it as close to a tad toe-out 1/32nd or 1x16/th at the front & """"toe-in"""" the same amount at the back (total) then you`d be doing good.

edit,,, it does sound like you`re a bit high in ride height atm tho hey?
Author:  jme [ Wed Mar 20, 2013 2:14 pm ]
Post subject: 
I just thought I'd provide some feedback on how I resolved this. Basically there were two problems - the back of the car was too low which encouraged the nose lifting and the back squatting, the change in suspension geometry created bump steer. The other problem was that there was free play in the rack, this exacerbated the bump steer.

A new steering rack and raising the back worked a charm. There is still very slight torque steer from the LSD but it is only barely detectable.

Thanks for all the input, it was much appreciated.
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