• Forum membership has its advantages....

Is IRS a good option for the new AWD trucks??

Dezertpilot

Well-Known Member
#21
w suspension technology today, has any one looked at a full blown tt front straight axle, i mean it works killer in the back, why not the front, im not talking about koh type , but somthing way beyond that, just thinking .ps is that cars or drivers going back to ' classless'?
By design will not ever work like an Independent front suspension.
 

jon coleman

Well-Known Member
#22
thats what im thinking, the current status quo( strt axl) wont stack up, sombody i think will come up w a little bit of the best of both worlds,ifs/ straight axl,? & win race's, and cause sore losers .i hope.bottom line whose gonna update the same basic design since the 20's?:rolleyes:
 
Last edited:

isdtbower

Well-Known Member
#25
An offset differential in both Straight rear Axles and IRS can improve ground clearance significantly. Both use a rear motor to a transfer case near the drivers feet.. The straight thru Transfer case driveshaft goes to the centered IFS.

Joe Thompson builder, UFO Fabrication, Nor Cal. This car has seen the Ultra4 podium a number of times. The center has a BIG dog bone looking double CV. This is a single center seat rig but the "driver side" arm has clearance probably equal to a portal. ...but you could let that center squat to the ground if you let it.

An IFS can definitely be designed and built that works worse than a straight axle. Surprising is that the geometry so common in top desert trucks and almost all Rally/Dakar cars has not filtered totally into Ultra4. The pro's like the new Rhys Millikan truck/buggy get it. Not sure about the new AWD trucks as the media thinks great post-able pictures are only in the air or exploding dust bowls. One compromise with IFS is turn angle vs wheel travel. Ultra4 is probably 35* and more turning, while desert might be 30* and less as all that is necessary. Wheels can recede when hitting things in the desert, but tend to lift the front when climbing in Ultra4. Driven IFS also presents huge forces on the steering racks and linkage. The half shafts make the upright feel like it is locked up transferring every hit and throttle/brake force back thru the steering when articulating. Breaking 4ea 3/4" bolts was common until keying the rack to the uprights was developed. As with most things. It is easier to tell what NOT to do than what TO do.

Scott at Proformance, Australia, showing off the possible but "un-probable."

An early adopter of IFS that rolled on several occasions until body roll was controlled. Successful cars like this take GREAT drivers.
16299270_1041670532604347_6360876919535137525_n.jpg
299189_221245927922605_5256089_n (2).jpg
004_10492127_10150389445839971_30499181754667330_n.jpg
 

jon coleman

Well-Known Member
#26
seems to be a trade off between dancing on top of 3-4 foot whoops ,rock crawling,& rallie racing,its the ying/ yang happy balance thing.or just have different race tt's for different course layout$just look at the BFG BLAZER pics on rDc when u think more is better, shoot, my old toyota sr5 had more travel....
 
Last edited:
#27
It’s an excellent option for any TT. The biggest consideration needs to be optimization. It’s all about compromise. Every type of suspension has its strengths and weaknesses.

If your truck was Strickly designed for Baja or Vegas to Reno, then absolutely run IRS.
 

Bro_Gill

Well-Known Member
#28
It’s an excellent option for any TT. The biggest consideration needs to be optimization. It’s all about compromise. Every type of suspension has its strengths and weaknesses.

If your truck was Strictly designed for Baja or Vegas to Reno, then absolutely run IRS.
I think it depends on course layout. If the Baja course used a lot of the San Felipe type whoops, then I think the straight axle in the rear has an advantage.
 

J Burleson

Well-Known Member
#29
I am currently building an IRS car with 28" of rear wheel travel at 22* CV angle. All off the shelf parts. It is designed to run in class 1 or TT. I cant say if I'm in the design phase of an AWD version or not, because I dont want to give away any secrets! Yes, IRS is legal in TT! only in SCORE are live axles NOT allowed in class 1. I will start a build thread if anyone is interested. You can also checkout my Instagram for more pics and info @burlesondesigns
 

Attachments

PeteRock

Active Member
#34
I am currently building an IRS car with 28" of rear wheel travel at 22* CV angle. All off the shelf parts. It is designed to run in class 1 or TT. I cant say if I'm in the design phase of an AWD version or not, because I dont want to give away any secrets! Yes, IRS is legal in TT! only in SCORE are live axles NOT allowed in class 1. I will start a build thread if anyone is interested. You can also checkout my Instagram for more pics and info @burlesondesigns
Can't wait to see this build! there have been a few cars with similar design over the years, but the components available today should make your build leaps ahead of the previous cars.
 

J Burleson

Well-Known Member
#35
Thanks PeteRock! Yea, all of the parts I am using are either tried and true, or very basic. Im using the Proformance D80 diff in these chassis. What I love about Scott's parts is that he always seems to find a way to take as many small components out of the equation as possible, instead of adding more parts to break!
 

Ol' Curmudgeon

RDC's resident crackpot
#37
Thanks PeteRock! Yea, all of the parts I am using are either tried and true, or very basic. Im using the Proformance D80 diff in these chassis. What I love about Scott's parts is that he always seems to find a way to take as many small components out of the equation as possible, instead of adding more parts to break!
How will you protect your back when both rear wheels are at full compression and the chassis slams the crown?
 
#38
I don't think so, not when I saw it at Laughlin or Barstow, IIRC.

SA JGC was Leslie's.

Why would you think I would quote you and give you an example if I thought it was?
nope. all the Cherokee bodied vehicles race in the trophy truck class was the leslie class 8 and then a cherokee bodied trophy truck driven by curt leduc first in the original red and then the valvoline colors. you probably thought it was twin traction beam cause it has swing set steering like one.
 

Attachments

isdtbower

Well-Known Member
#40
You are making the assumption that the added rear wheel travel (over a standard class 1) is being gained at compression?
The Proformance Center is pretty big in diameter...unless you are using portals. I am using a quick change without portals and definitely limiting. With 85" OoT, I will probably have to drop from 24" to 20ish on 40's.. How are you doing on plunge?

Check your camber to the ground with 80% compression and 5* (rear) body roll. Best not to go positive. Semi swingarm numbers turned to trash for me at the bigger strokes.

Jimco has a solution, in the right direction, for IRS... But their TT's still run SA, I believe.
 
Top