Lower car - suspension geometry question? - Alfa Romeo Forum
You are currently unregistered, register for more features.    
Tuning & Upgrades Discuss performance enhancements for your Alfa Romeo

Reply
 
Thread Tools
(Post Link) post #1 of 42 Old 15-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Lower car - suspension geometry question?

What do you think about my thoughts.
When the car is lowered, front suspension arms mounts on the subframe are lower than the mount at the wheel.
So when car gets into corner and the outside wheel is pushed even further up, it goes into positive camber which is bad for traction.

I made some sketch in the attachments.

What if i would lower the arm at the wheel with some kind of spacer (on the picture red and yellow)

I know they make "spacers" for some very old alfas so that when car is lowered, arm stays in the same place and in the corner forces the outside wheel in more negative camber for better traction.
Attached Images
File Type: jpg geometry.JPG (18.6 KB, 35 views)
File Type: jpg rokagtv.jpg (58.1 KB, 31 views)
alan Q4+33 is offline  
Sponsored Links
Advertisement
 
(Post Link) post #2 of 42 Old 16-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Anyone?
alan Q4+33 is offline  
Status: -
AO Platinum Member
 
David C's Avatar
 
Join Date: Aug 2003
Location: London, England
Posts: 29,957
Re: Lower car - suspension geometry question?

You have -ve camber and +ve camber the wrong way round!

You already have -ve camber as std, when lowered you get slightly more -ve camber. You will never get +ve camber.
David C is offline  
Status: One foot in, one foot out!
AO Platinum Member
 
zulu ferret's Avatar
 
Join Date: Oct 2006
Location: wgc
County: herts
Posts: 42,278
Re: Lower car - suspension geometry question?

Eactly as David C states.

A negative camber reduces the camber angle when the vehicle is cornering and the vehicle tilts. A negative camber therefore provides an improvement in vehicle handling whilst the vehicle is cornering.

However, negative camber also increases the offset and therefore produces heavier steering. Note that negative camber will also increase tyre wear as the camber angle increases.
zulu ferret is offline  
alfafamily
Status: - Update
Guest
 
Posts: n/a
Re: Lower car - suspension geometry question?

If you were in UK I would strongly advise against the mods you are suggesting especially for road use. In any insurance claim after an accident you could be on very dodgy ground.
The extra neg camber you get when lowering can be responsible for unwelcome excessive tyre wear. I would look into other ways of re setting the geometry.
 
Status: -
AO Platinum Member
 
David C's Avatar
 
Join Date: Aug 2003
Location: London, England
Posts: 29,957
Re: Lower car - suspension geometry question?

He needs to look carefully at the GTV's front suspension design.

His diagrams show the angle of the wheel changing in relation to the strut. That can't happen. The hub is bolted to the strut, so it stays at exactly the same angle to the strut no matter how the suspension moves.
Lowering will give slightly more -ve camber because the wheel moves upwards into the arch slightly more. But the amount of -ve camber will not be a problem.
What will be a problem is the tracking. Make sure it is set to 0mm tow. Any toe-out will quickly scrub off the inner edge of the tyre.

David C

Audi TT 3.2v6 DSG
2012 Renault Twingo 1.2
xAlfa 156 Selespeed sp3 + Brembo conversion
Fiat Cinquecento 899cc

Last edited by David C; 16-03-09 at 10:22.
David C is offline  
Status: One foot in, one foot out!
AO Platinum Member
 
zulu ferret's Avatar
 
Join Date: Oct 2006
Location: wgc
County: herts
Posts: 42,278
Re: Lower car - suspension geometry question?

To you both.:
zulu ferret is offline  
(Post Link) post #8 of 42 Old 16-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Quote:
Originally Posted by David C View Post
He needs to look carefully at the GTV's front suspension design.

His diagrams show the angle of the wheel changing in relation to the strut. That can't happen. The hub is bolted to the strut, so it stays at exactly the same angle to the strut no matter how the suspension moves.
Lowering will give slightly more -ve camber because the wheel moves upwards into the arch slightly more. But the amount of -ve camber will not be a problem.
What will be a problem is the tracking. Make sure it is set to 0mm tow. Any toe-out will quickly scrub off the inner edge of the tyre.

No no no, i know that wheel doesnt move in relation to the strut.
My point is just that the arm does a circular motion when moving up-down. Thats why the track of front changes in width when lowered. problem is that in my case (i'm sure in others too) car is very low and arms are higher at the wheel then at the subframe, so when the wheel is pushed into the wheel arch the arm pulls the wheel in, so it's changing the camber too.

This is negative /----\ and this is positive camber \---/ as i know.


I know it's hard to understand this, and i'm not so good in english.

Here is a pic of distances for subaru arms:

alan Q4+33 is offline  
Status: -
AO Platinum Member
 
David C's Avatar
 
Join Date: Aug 2003
Location: London, England
Posts: 29,957
Re: Lower car - suspension geometry question?

Do you still think you are getting +ve camber...?

How much lower than std is it?
David C is offline  
(Post Link) post #10 of 42 Old 16-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Too much lower, i dont know because it was like that when i bought her.
First i will change the springs for eibach sport kit 20mm drop.
I think she will go up for 20-30mm form now.

Here is a picture from the pdf of gtv, standard suspension (just the stabilizer is diferently linked here- like on a 155)

Ideal for lower arm is this position on the picture, so when the wheel goes up, arm gets into horizontal position, or maybe little over, so that she gets perpendicular to the shock absorber.

alan Q4+33 is offline  
(Post Link) post #11 of 42 Old 17-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

I found almost exactly what i need (knuckle risers)





These are for old alfa gtv, so that after lowering arms get into stock position.

Now i'll fabricate something for mine.
alan Q4+33 is offline  
(Post Link) post #12 of 42 Old 17-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Useful page: Racing Aspirations - a 750 Formula constructors diary (Fiat FIRE 1108) - Utilities
alan Q4+33 is offline  
Status: a good shot of nitrous will sort that!
AO Silver Member
 
jbsmith1's Avatar
 
Join Date: May 2008
Location: United Kingdom
County: Essex
Posts: 1,968
Re: Lower car - suspension geometry question?

Just a thought, but I think you may induce bumpsteer if you lower the bottom wishbone, I think you will need the steering arms to follow the new arc too
jbsmith1 is offline  
(Post Link) post #14 of 42 Old 17-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

You are correct, they have to be parallel so there is no difference in arc and travel. I'm focusing on lower arm because it's the difficult part. Then the steering...
alan Q4+33 is offline  
Status: a good shot of nitrous will sort that!
AO Silver Member
 
jbsmith1's Avatar
 
Join Date: May 2008
Location: United Kingdom
County: Essex
Posts: 1,968
Re: Lower car - suspension geometry question?

goodluck with the modding.
jbsmith1 is offline  
Status: -
AO Silver Member
 
edward's Avatar
 
Join Date: Dec 2003
Location: United Kingdom
County: Somerset
Posts: 3,000

Member car:

156GTA & 33racer

Re: Lower car - suspension geometry question?

I dont know if it helps but we used to change camber on 33's by keeping the bottom inner bolt in place and elongating the other 3 holes. We then used a camber gauge once the car was at the correct height to create the camber we wanted.

Dont forget the toe though!
edward is offline  
(Post Link) post #17 of 42 Old 19-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

I did that too on some cars, so the camber could be adjustable.

Here is the point that camber changes when the wheel goes up-down.

I measured everything and with the program i have linked previous i have found that camber changes for 0.8 when the wheel goes fully up. Problem is that it changes from -1 to -0,2 so it's almost zero in the corner. If i lower the arm enough and leave the camber at -1 then when fully depressed arm gets into parallel with the ground or slightly up so that it's perpendicular with the shock absorber come to almost -2 camber and that would be ideal for cornering.

Somthing else i will try is to move mounting position on the top, to get little more camber as standard and little more caster.
All will be fully reversible so no problem with that.

alan Q4+33 is offline  
Status: -
AO Member
 
Join Date: Jun 2005
Location: Australia
County: Queensland
Posts: 640
Re: Lower car - suspension geometry question?

This article may help.

http://www.whiteline.com.au/images/a..._Align4_06.JPG
tremolo is offline  
Status: bought a 75 3.0
AO Silver Member
155 Lounge Winner 09
 
shiny_car's Avatar
 
Join Date: Dec 2006
Location: Australia
County: Victoria
Posts: 7,713

Member car:

GT . 155 . 75

Re: Lower car - suspension geometry question?

interesting mods. top-mount camber 'kits' are common place, but i haven't seen 'knuckle risers' before - cool.

indeed, it is possible to have postive camber relative to the road surface during heavy cornering, even though the camber is negative relative to the chassis. it depends totally on the design of the suspension geometry and pivot points. i've no idea if the GTV is subject to this though.

shiny_car is offline  
(Post Link) post #20 of 42 Old 20-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Here is a picture that shows what happens whit travel of the suspension. Now you can understand, why it's best that the arm never gets more than 90 angle to the strut. Up to that angle the strut is pushed out, over that angle it's pulled in again, and the camber goes from negative to 0 and to positive in some cases.

The best is that the strut is pushed out max when the suspension is fully depressed. That's why moving the arm back to stock position after the lowering is good.

(picture is not mine, it's from the web)

alan Q4+33 is offline  
Status: -
AO Silver Member
 
Alfie GTV's Avatar
 
Join Date: Oct 2005
Location: United Kingdom
County: Wiltshire
Posts: 2,274

Member car:

2002 GTV T.Spark

Re: Lower car - suspension geometry question?

Quote:
Originally Posted by David C View Post
He needs to look carefully at the GTV's front suspension design.

His diagrams show the angle of the wheel changing in relation to the strut. That can't happen. The hub is bolted to the strut, so it stays at exactly the same angle to the strut no matter how the suspension moves.
Lowering will give slightly more -ve camber because the wheel moves upwards into the arch slightly more. But the amount of -ve camber will not be a problem.
What will be a problem is the tracking. Make sure it is set to 0mm tow. Any toe-out will quickly scrub off the inner edge of the tyre.
Hi David. Is 0mm tow correct for the GTV in standard form, and should it stay the same if lowering by about 20mm?
I ask as both inside edges are more worn than the rest of the tyre.I know FWD has this effect, i hate having to replace the tyres when 3/4 are still legal
Alfie GTV is online now  
Status: -
AO Member
 
Join Date: Feb 2009
Location: United Kingdom
County: Devon
Posts: 185
Re: Lower car - suspension geometry question?

The problem with 'knuckle risers'/roll centre correctors or whatever else they are called is that they change the geometry relative to the track rod joints and can cause excessive bumpsteer. For some cars the kit includes modified track rod ends so as to avoid this drawback.
George K is offline  
Status: -
AO Platinum Member
 
Gary Slegg's Avatar
 
Join Date: Feb 2006
Location: North Wales
Posts: 16,710
Re: Lower car - suspension geometry question?

I read somewhere that lowering a GTV can cause excessive wear of the suspension bushes...
Gary Slegg is offline  
(Post Link) post #24 of 42 Old 20-03-09 Thread Starter
Status: 156 3.0 GTAm 1070kg 200kw
AO Silver Member
 
alan Q4+33's Avatar
 
Join Date: Sep 2006
Location: Slovenia
County: -
Posts: 2,020

Member car:

156, 166

Re: Lower car - suspension geometry question?

Mine has wheels 1mm apart at front, and tyre wear is normal.
I have around 1 negative camber at front.

@ george k

Yes, steering arm has to be parallel with lower arm, so that both do same radius when they move up/down.
This means that if i lower the arms for 3cm i have to lower steering arms by the same amount.

Well first new eibach prokit and then i will see what's what, because my springs are tired and car is too low.
alan Q4+33 is offline  
Status: -
AO Platinum Member
 
David C's Avatar
 
Join Date: Aug 2003
Location: London, England
Posts: 29,957
Re: Lower car - suspension geometry question?

Quote:
Originally Posted by Alfie GTV View Post
Hi David. Is 0mm tow correct for the GTV in standard form, and should it stay the same if lowering by about 20mm?
I ask as both inside edges are more worn than the rest of the tyre.I know FWD has this effect, i hate having to replace the tyres when 3/4 are still legal
Having a lot of toe-out is what wears the inner edges.
Set them to 0mm toe and they will be fine.

If you lower it, it will need adjusting again.

ANY FWD car will wear the inner edges when set to toe-out.
David C is offline  
Reply

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Tuning & Upgrades

Tags
car , geometry , lower , question , suspension

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome