Technical: IRS vs. SRA in Racing Applications.

[07trx400ex]

I would like to start a technical article on the advantages/disadvantages of an IRS equipped quad versus and SRA equipped quad.

I would request that any posts are informative and valid and that everyones opinion is respected as long as it is based on fact.

I would first like to clarify goal of a suspension system: To ensure vehicle stability under any circumstance associated with accelerating, cornering, and braking while avoiding any undesirable movement.

The double wishbone rear suspension has many advantages and some disadvantages compared to a live rear axle.

It allows for increased tuning capabilities including camber, caster, toe etc....

Increasing negative camber gains all the way to full suspension travel. Can be very useful on uneven terrain.

It is more complex and currently weighs slightly more. The design of an dual a-arm setup compared to an axle actually reduces unsprung weight allowing the suspension components to function at a higher level.

Also, without a very stiff anti-sway bar torsional rigidity is reduced producing more body roll. Can be remedied by the addition of a very stiff and rigid anti-sway bar and the shock mounts seem as if it would be a great place to mount one.

IRS do not slide as easy and tend to have more body roll on a turn

[07trx400ex]

Sliding is actually scrubbing off speed. The reason IRS does not slide is based on two principles.

The dual control arms allow camber changes to allow the wheel to be in constant traction.

The two wheels on an IRS quad can move and travel independently of one another allowing for more traction and more precise high speed maneuvering.

If the wheels are grabbing traction the they do not "break loose" and spin as easily.

Also, the body roll/pushing/understeer is due to less torsional rigidity of a wishbone setup compared to that of a live axle. This can be remedied by the addition of a very rigid anti-sway bar.

you need to be able to slide in certain conditions though.

[bradley300]

i would say for dirt track oval racing it would be hard to beat a IRS qua, if you could keep the weight down. like was mentioned, sliding is slower than railing thru a turn. with the advantages of setting camber on the rear, plus having each wheel independent of the other, cold make sliding at a flat track race a thing of the past, and speed thru the corner would go way up.

in mx the best advantage would be not having to square up fora whoop section or jump. this advantage is multiplied in XC where alot of times,squarring up is not an option

the down sides such as body roll can be controlled with the correct sway bar/rear shock set up. the issue is that there is only 1 irs sport quad out, and it being a polaris on top of that, aftemarket r & d is lacking.

the other issue is weight. i'm sure a smart engineer can figure this one out eventually

[RATPACK Z400]

I think the body roll will never be competly gone with stabilizer for one ,two the weight will never compare,and it on off camber will roll over easer than a staight axle would in my opion.Sra is in my opion better and will never be beaten by irs suspention in racequads there only good for the leisure trail rider that cant ride cause of age or weight a REAL sportquad!You people are buying into the Irs BS that there better are being fooled into buying It cause americans are overweight and they need a quad built for them, thats all it really about the market is building to this 30ish to 40ish overweight with money and saying that these quads are the future ,Yes they are the future for overweight people and older leisure riders that have money! not that the irs sus, isn,t good but for racequads get real! The technology isn,t there ,and wont be for a long time.