I need to Check my A-Arm suspension geometry to desert race!

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
Hi, I from Chile, Southamerica. I designed a buggy and I need to know the best set-up to my suspension before to built.I drew in solidworks and now I need to check if the geometry used is the best to ride in desert and dune


Front suspension: A-Arm
Caster: 8°
Front view
track width: 83"
Ride height: 40% droop, camber -1°
Full bump camber -6
Full droop camber -4
Scrub radius: 1"
Toe-out: 1/8"
Wheel travel:18-20"
Tire: 33"x12"
no bumpsteer
inner pivot with bushing
outer pivot (spindle side) whit 5/8" chromoly heim with spacer.
Unequal non-parallel whishbone.
I used a toyota hilux 88´ Spindle, but I think that I built a new spindle so I will need the dimension to design.
2 coilovers 16" travel with reservoir and 2 simple shocks.




Rear suspension: Semi-trailing arm
Wheel travel: 17"
Semi-trailing arm angle:8°
Stock VW CV joint (but I´m trying to find other with more angle)
I considered the plunge.
2 coilovers 16" travel with

Other
Transmission:VW 6 ribs.
Engine: Nissan SR20DE (150 HP)
Roll Cage: Based on FIA.


Please, comments.
image.png
 

Rory

Crayola Killer
Joined
May 11, 2001
Posts
6,652
RDC Crypto
4,157
Location
Arizona
Website
www.racers-only.com
Jose, go over to the "Shop" section of the forum (or it will most likely be moved for you), someone will be able to help you I'm sure.
 

spi6616

Well-Known Member
Joined
Aug 24, 2007
Posts
114
RDC Crypto
8
Location
Phoenix, AZ. 85014
I have been building and designing Off-road cars for 35 years and A-arm front suspensions with great success for 25 years! I noticed that in your information list you didn't include your KPI (Kingpin Inclination) it is extremely important to have this correct with Off-set of wheels, Diameter of tire and scrub -That you did include! email me if you want any other advise on your project. Dspencerpi@aol.com or PM me!!
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
I have been building and designing Off-road cars for 35 years and A-arm front suspensions with great success for 25 years! I noticed that in your information list you didn't include your KPI (Kingpin Inclination) it is extremely important to have this correct with Off-set of wheels, Diameter of tire and scrub -That you did include! email me if you want any other advise on your project. Dspencerpi@aol.com or PM me!!

Thanks mate! I email you today!

Rgds
 

QurtysLyn

Well-Known Member
Joined
Jul 8, 2005
Posts
739
RDC Crypto
167
Location
Centerville, Utah
I can't say much on the front geometry, as I don't have any experience with A-Arms. But that is one bitchin' looking buggy.

When you say Stock VW CV joint, which one Type 1, Type 2 or Type 4? You can get a lot more angle out of a Type 4 than you can a Type 1, or you can step up to 930 CV's and get even more.
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
I can't say much on the front geometry, as I don't have any experience with A-Arms. But that is one bitchin' looking buggy.

When you say Stock VW CV joint, which one Type 1, Type 2 or Type 4? You can get a lot more angle out of a Type 4 than you can a Type 1, or you can step up to 930 CV's and get even more.

Thanks mate. Is hard find type 4 in Chile, there are type 1 and 2. I bought Type 2. 930 is not comercial here. I will take a look on ebay.
Type 2 CV is a big problem for me jajaja it reduce my wheel travel almost in 4" but is better than the type 1.
 

DesertGuy1

Well-Known Member
Joined
Sep 29, 2007
Posts
807
RDC Crypto
143
Location
CA
Concerning your front geometry, the information provided lacks a few details to give a 'good' opinion. That said, based on the above, a few questions come to mind.

A combination of coilovers and emulsion shocks is not something that is seen often. What is the front's motion ratio that requires a 16" shock in the front?

What is the lateral tire scrub throughout the suspension's cycle? Meaning, how much does the width of the suspension grow or contract throughout the cycle (this is different than tire scrub). High lateral tire scrub numbers are not a suspensions best friend on parts, especially in desert terrain... it is more forgiving in sand but a detriment in hard packed. At first glance at the above numbers, I'd suspect it to be a little high.

Very nice model, btw
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
Concerning your front geometry, the information provided lacks a few details to give a 'good' opinion. That said, based on the above, a few questions come to mind.

A combination of coilovers and emulsion shocks is not something that is seen often. What is the front's motion ratio that requires a 16" shock in the front?

What is the lateral tire scrub throughout the suspension's cycle? Meaning, how much does the width of the suspension grow or contract throughout the cycle (this is different than tire scrub). High lateral tire scrub numbers are not a suspensions best friend on parts, especially in desert terrain... it is more forgiving in sand but a detriment in hard packed. At first glance at the above numbers, I'd suspect it to be a little high.

Very nice model, btw

Thanks for your comments... I understand all that you say...

I designed a new spindle with 17° kingping angle and my number change.

Camber bump: -6
Camber rigth heigth : -2
Camber droop: -2,5
New wheel travel 19.5"
I measured the new scrub radis and is 1 1/2"

the width change between full bump and full droop is 3.6" I dont know if that number is too much or is good.
Respect to the coilovers I used 16" and dont have any problem ( in the software) with them but you recommend 14"??? Both shock are with reservoir
attached a pic show it the wheel travel, change width, camber change, wheel ratio and instan center.

Thanks for your help and I hope your comments.

1111.png
wheel radio.png
instant center.png
 

Scott_F

Well-Known Member
Joined
Dec 28, 2003
Posts
1,045
RDC Crypto
61
Location
Tucson, was Anaheim
I like your design, and you are doing an excellent job so far.

In my opinion, your shocks are way too long. At full bump, it is no where near 90*.

The 5/8" heims are way too small for your spindle pivots. You should use at the very least, 3/4" or 7/8" heims, or 1" uniballs.
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
Thanks scott...
Yeah, desertguy1 helped me a lot.
I redesigned my front suspension. Now I have 12" coilovers with 90* at full bump.
I have a ratio between wheel travel and shock travel of 1.72.
Now I have a little scrub tire but less than 1/4".
I designed a spindle with 9 degrees and 1/2" of scrub radius.
The camber is -6 at full bump, -1 at right height (40%) and -6 at full droop.
I have 20" wheel travel front
I change the caster to 7 degrees.
Which is your opinion?

For semi-trailing arm I used 8* for torsion housing and now I need to know if to use 1/8" toe in and -2 camber at right height.

And my last question is: can I use u joint instead of cv joint? I have a 6 ribs transmission and cv joint type 2 with 17* but is the limit for my wheel travel almost 16". I can't buy other cv because in my country don't sell 930 or other. I need to import f-o-a coilovers and is a big cost in tax and shipping.

Regards

Jose



Sent from the RDC Mobile App. Get it for your IOS device today
 

DesertGuy1

Well-Known Member
Joined
Sep 29, 2007
Posts
807
RDC Crypto
143
Location
CA
For semi-trailing arm I used 8* for torsion housing and now I need to know if to use 1/8" toe in and -2 camber at right height.

And my last question is: can I use u joint instead of cv joint? I have a 6 ribs transmission and cv joint type 2 with 17* but is the limit for my wheel travel almost 16". I can't buy other cv because in my country don't sell 930 or other. I need to import f-o-a coilovers and is a big cost in tax and shipping.


Drive axles do not like being offroad. When designing the rear suspension, do not 'design' in a vacuum - understand how the rear relates to the front and what, if any, packaging of components will play. Will the transaxle be mounted as a drop-out, where will the fuel cell be located, any clearance issues of engine or transaxle, etc... Consider all parameters (front/rear) then adjust geometry accordingly - in my opinion. You don't want to get too far down the design road to realize you need to take two steps back (been there/done that...multiple times).

http://www.race-dezert.com/forum/showthread.php/89157-tranns-axel-placement?p=1197350#post1197350
 

QurtysLyn

Well-Known Member
Joined
Jul 8, 2005
Posts
739
RDC Crypto
167
Location
Centerville, Utah
Thanks mate. Is hard find type 4 in Chile, there are type 1 and 2. I bought Type 2. 930 is not comercial here. I will take a look on ebay.
Type 2 CV is a big problem for me jajaja it reduce my wheel travel almost in 4" but is better than the type 1.

Understandable. You have many BMW's there? The CV's off of the following will mount up to a Type 2 output flange if I remember correctly.

BMW: 1500, 1502, 1600, 1602, 1800, 1802, 2000, 2002, 316 (6.'75-8.'78 ), 318 (6.'75-8.'78 ), 320/4 (6.'75-8.'78 ), 320/6 (6.'75-8.'78 ), 320i (6.'75-8.'78 ), 323i (6.'75-8.'78 ), 518 (6.'72-9.'78 ), 520/4 (6.72-9.'78 ), 520/6 (6.'72-9.'78 ), 520i (6.'72-9.'78 )

This site, http://www.rorty-design.com/content/CV_joints.htm , is a write up on it. They should get more travel than a Type 4, I remember reading that they could go 23° or 24°, but I can't find it. I'll keep searching.
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
Tranks man, I'll try to find these cv joint.

I want to begin to build the roll cage and front suspension. I think that I finish front suspension design. Tomorrow I'll upload some pics of my design.



Sent from the RDC Mobile App. Get it for your IOS device today
 

neneossa

Well-Known Member
Joined
Dec 18, 2012
Posts
78
RDC Crypto
38
Location
Chile
I've learned a lot these past few weeks. I redesigned the front and rear suspension, all my numbers changes.
Now I have:

Caster:7°
SAI angle: 9°
Offset: 0
Camber: -6 at full bump, -1 at right height and -6 at full droop.
Lateral tire scrub: less than 1/4"
Front wheel travel: 20"-21"
Rear Wheel travel:18-20"
Shock angle at full bump: 90°
Front suspension: coilovers2.0" x 12" (travel) and 12" bypass
Rear coilovers: 2.0" x 16"
torsion housing angle: 8°
Rear camber at right height: -1
Spindle with 3/4" Heims (upper and lower)
Semi trailing arm with 1" uniball and 7/8 heims.

Now I began to build the chassis. I need to finish all the details on my design as rear arm, wheel steering support, fuel tank, and other more stuff that need a lot time.

Please comments about the numbers and design.
any feedback is welcome!

946601_10152048652567656_1191231840_n.jpg
1075674_10152048652387656_1217403817_n.jpg
1005435_10152048652467656_368321305_n.jpg
1.png
2.png
3.png
4.png
 
Last edited:

redmist

Well-Known Member
Joined
Jun 8, 2006
Posts
406
RDC Crypto
25
Location
Christchurch, Canterbury
Thanks mate. Is hard find type 4 in Chile, there are type 1 and 2. I bought Type 2. 930 is not comercial here. I will take a look on ebay.

Think you'll find the 930 is incredibly common... everywhere. It's a BMW series 5 CV, or TVR Cerbera, and more than likely placed in considerably more vehicles. Even if you have problems sourcing them you'll want a couple, with grease and race prepped ready to use, as such it'll be of no issue to you if you have to source them remotely.
I source my 934 race CV's from the states (I'm in NZ), have a full set that I keep spare and alternate them into the car when I rebuild a set. As such I have no issue if I have to order new cages.
 
Top