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Help With Geometry...


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#1 dannzhu

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Posted 30 May 2009 - 08:50 AM

Model: 1986 City
Any non-standard parts that might be involved with the problem?

  • Minispares full geometry kit
  • Lowered GAZ shockers
  • 12x6 rims (positive offset...dunno how much)


Description of problem:

The 12x6 rims scrub on the front arch (notably the right one). No trimming has been done yet (was hoping if I can get away with trimming).
Then I got the shockers and geometry kit installed by my mechanic and car sent to wheel alignment place.
Cannot get settings print out, but this is according to my mechanic:

  • Camber: 1 deg front, 0 deg rear
  • Toe: Out front, in rear (forgot how much...)
  • Castor: 1 deg (done to this extent to give the clearance...)
  • Shockers: hard
Now the steering wheel is off-center, slight pulling problem (which hasn't been corrected by the alignment), steering seems a bit lighter, car feels more agile, the ride is so bumpy BUT....something feels a bit off.
My questions are:
  • Is it normal to have 1deg castor??
  • Still on castor, I read on the Minispares and this forum, it's suggested about 3-3.5deg. Is that setting universal on all size wheels (10, 12 and 13)? If not, do bigger wheels usually require lesser or more castor angle?
  • My left front wheel seems to stick out more than the right (looking from above). Is it normal?
  • Do I have to adjust the shockers while the car is jacked up or is it OK to do it while car on the ground? I can see the buttons and I can reach them...
  • Do people normally have even shockers stiffness front and back? If not, is it better to have front softer than back or the opposite?
  • I'm thinking of getting the alignment redone again, but I need some advice on how to best approach it to make sure it's done correctly?


Thank you,

Daniel

Edited by dannzhu, 30 May 2009 - 09:02 AM.


#2 icklemini

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Posted 30 May 2009 - 12:58 PM

1.Is it normal to have 1deg castor??

Nope need more...

2.Still on castor, I read on the Minispares and this forum, it's suggested about 3-3.5deg. Is that setting universal on all size wheels (10, 12 and 13)? If not, do bigger wheels usually require lesser or more castor angle?

With the mini, and bigger wheels more castor is usually the way to go...

3. My left front wheel seems to stick out more than the right (looking from above). Is it normal?

Um - might be previous repairs, or such like... Minis arent symetrical though...

4.Do I have to adjust the shockers while the car is jacked up or is it OK to do it while car on the ground? I can see the buttons and I can reach them...

Can adjust them on the floor..

5.Do people normally have even shockers stiffness front and back? If not, is it better to have front softer than back or the opposite?

Personal preference... you do want sume suspension complience though.. Hard isnt the best...


6.I'm thinking of getting the alignment redone again, but I need some advice on how to best approach it to make sure it's done correctly?

A few things to consider... best to get it to a decent tyre/bodyshop/race mechanic who will have 4 wheel alignment who can ensure that the rack is central, and the geometry is set correctly all round...

#3 dannzhu

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Posted 30 May 2009 - 02:47 PM

Thanks for the reply. Your name pops out a lot on the search on suspension geometry... :)

Anyways, you said 1deg castor is not enough and bigger wheels (I assumed wider wheels as well...) require more castor.
Is that solely for arch clearance? Does it have any effect on the steering?? More castor, lighter steering perhaps?
What's the castor angle on standard minis??

I read on a local forum, some people actually has negative castor (-5deg)??
And when Minispares say 3-3.5deg, I assume it's a positive degree...
So, is it correct that positive castor pushes the wheel back and negative pushes wheel forward?

About damper settings, when I bought my car it was fitted with soft coil springs.
It ran almost like a modern car and I've gotten used to it, but it often scrubbed during hard cornering with the original 12x5 wheels.
A friend from the club said I need to get harder damper settings to compensate the soft coil springs.
What's your opinion on that?

The alignment was done at a wheel alignment shop. I think the car was set up on 4 wheel alignment and they used computers to simulate road conditions??
But I guess they forgot about centering the steering rack. They only spent an hour to do it...

I also found that the rear driver side squeaks now. It's like something was loose, and at one point I kinda heard a screw came off.
But I checked the damper mount, rear camber bracket, etc and couldn't find anything wrong...

And what about corner weights? How important is it in the geometry settings for road minis?

I hope you don't mind with all the questions.


Thanks,

Daniel

#4 Pauly

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Posted 30 May 2009 - 04:01 PM

Any wheels over 5x12 will need arch mods, you wont get away with suspension geometry, if you set the suspension up and they miss then you haven't got the suspension setup right and you are putting componments through premature wear.

Paul.

Edited by Pauly, 30 May 2009 - 04:01 PM.


#5 dannzhu

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Posted 31 May 2009 - 12:23 AM

Any wheels over 5x12 will need arch mods, you wont get away with suspension geometry, if you set the suspension up and they miss then you haven't got the suspension setup right and you are putting componments through premature wear.

Paul.


Thanks for your reply Paul.
I was looking at your weekend toy project. I assume you're running 12x6 with W&P arches??
That's what I'm doing as well...
Next step is taking it to the panel shop to do the arches and the inevitable arch mods.

Did you have to cut much? And how hard is it to fit the W&P to modded arches?

Daniel

#6 Pauly

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Posted 31 May 2009 - 07:41 PM

I had to trim a but (not a lot though) the arches do have some give but only a bit, be sure not to trim to much, make sure you suspension cones etc are in good condition (not stupidly low etc) so you dont have to cut more than you need to.

Paul.

#7 icklemini

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Posted 31 May 2009 - 10:56 PM

Anyways, you said 1deg castor is not enough and bigger wheels (I assumed wider wheels as well...) require more castor.
Is that solely for arch clearance? Does it have any effect on the steering?? More castor, lighter steering perhaps?
What's the castor angle on standard minis??


Nothing to do with arch clearance, if the arch is in the way then the bodywork needs sorting... rather than have bad geometry (imho).
More castor gives a heavier feel to the steering wheel.

Standard minis are around 3degs. aim for that at least...

I read on a local forum, some people actually has negative castor (-5deg)??

Um - not mixing that with Camber??

About damper settings, when I bought my car it was fitted with soft coil springs.
It ran almost like a modern car and I've gotten used to it, but it often scrubbed during hard cornering with the original 12x5 wheels.
A friend from the club said I need to get harder damper settings to compensate the soft coil springs.
What's your opinion on that?

Well harder damper settings is one way of trying to sort it... or you could try raising the suspension... or fitting a bump stop to stop the arch rubbing. (note: dont run the suspension on the bump stop and you do need adequate clearance)

And what about corner weights? How important is it in the geometry settings for road minis?

Well thats the icing on the cake really on a road car.. if you have the means then yeah go for it...

Cheers,
Dave




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