The one thing I have noticed the most as a problem of sorts for the mp5 is the amount of bump steer in the car. I.E. when round an off or onramp of the freeway/highway and you hit a crack/bump the torque steer is pretty bad.

In an article I saw a SCCA driver had them use strut extensions with ball joints but I was looking for a more practical application for this.
I have looked at bilstein strut inserts or the mp3 bump stops....or maybe both.

Anyone has ideas or has actually done anything to decrease the bump steer info is much appreciated.

 

First off, don't confuse bump steer and torque steer. The two are very different animals.

To address the question, bump steer is an inherent problem with ALL cars that have McPherson strut front suspension. The problem is that the ends of the steering arms move in a different arc than the wheels when the suspension moves up or down.

You can change the bump steer geometry of a strut car by moving the steering arms and/or outer pickup point for the lower control arms. This is commonly done with strut-to-ball-joint spacer blocks (AWR sells them for the Protege), but can also be done with special ball joints, offset steering arms, special control arms, moving the entire steering rack up or down, and a variety of other methods. However, two things to note: (1) you will NEVER get rid of the problem entirely on a strut car, and (2) the stock bump steer geometry is probably close to ideal at stock ride height because Mazda engineers are NOT boneheads when it comes to chassis design. (Honestly, the days of stock cars coming from the factory with majorly FUBAR bump steer geometry at stock ride height ended 15 years ago.)

Bottom line: on a lowered car, it can be corrected with AWR spacer blocks. On a stock ride-height car, there's not much you can do. You CAN stiffen the ever-livin' %^#& out of the suspension and reduce the problem by reducing suspension movement, but this strategy comes with its own set of problems. And once again, you will NEVER eliminate the problem.

 

Torque steer is when the spin of the engine at increasing RPMs actually causes the front of the car to turn in the direction of the spin of the motor, correct? This happens with a motor that aligned longitudinally (front to back), correct?

Now, bump steer, practically, is when, like p5sunDevil said, you hit a bump or crack, and it feels like the whole car picks up and moves sideways?

 

well I dont think it has the entire car move sideways but yes that is about right. For example when on an off ramp that is a right turn (about 270degrees for example) and I hit a crack or bump the front end has a bump or jolt towards the outside of the turn.

Similar to torque steer as it is the front end wanting to go in a different direction but from a different cause.

Torque steer I havent noticed as much because , as said above, mazda's suspension is super nice.

Carguy- Thanks for the info, I wanst confusing bump and torque steer I just accidentally interchanged the words in my explanation. I will have the car lowered at the end of this summer, I already have my eibach pro kit at home but wont be installing it till beginning of september. At that point Ill go with some AWR suspension components to reduce the bump steer a little but I know it will never be gone, just want it reduced a little as I like taking those 25mph offramps at 50 =p

 

Torque steer is a problem with most torquey FWD cars...Not just cars with non transversely mounted engines...RWD cars don't have this, and only highly front biased AWD cars experience it normally...

Torque steer is kind of difficult to explain...It can happen in both Open and LSD equipped FWDs...When you launch a open diffed FWD car like a protege, one front wheel gets the torque most of the time...The open diff sends the engine's torque through the path with least resistance, so if launched hard enough this is why only one wheel spins...If somehow both tires have identical grip, which is rare, both wheels will get nearly equal torque...but I am getting off the topic..



The non-equal torque output will try to rotate one tire and thus the car around the other, and effectively "steer" the entire car. It also happens with LSD's becuase of the torque sensing internals will transmit the torque back and forth between the wheels, not just give an identical 50/50 torque split...Lockers will also not completely illiminate torque steer because of tire adhesion issues and pavement conditions...

when the tires/wheels that steer the car get the power, torque steer can be an issue...It is physics...when one front wheel gets the torque, it accelerates tire rotation which will turn the car unless the other front wheel gets identical torque and maintains the exact same amount of grip on the road...which is where all this is going, it never happens...

Please someone explain this better, I am too tired....

 

you soound really confused. what you are describing is the tires skipping across the pavement from hitting the crack or ridge. bump steer will be felt at all times when one wheel hits a bump and the other doesn't, not just when going into a turn. in this case, one tire hits a bump and causes the steering rack to move over, which causes the other wheel to turn and shimmy the car over. i also agree that not many cars these days exisbit any traits that would feel like bump steer, since it can make the car feel very nervous.

 

Thanks for the explanations. My dad's Volvo S80 has a serious torque steer issue. I floored it once, and the front end went well left of where it was, required some serious correction. I guess they didn't design it too well.

My pro, especially on a particular on-ramp, does skip to the right because of a nice combination of cracks and bumps, doesn't sound like njaremka's explanation of bump steer. Of course, I am usually putting some G's on at that on-ramp...

 

i was explaining true bump steer, and unless you have driven an older rack and pinion car, you probably haven't experienced bump steer. i had a 1972 triumph spitfire that had horrible bump steer, and the only thing you could do to lessen it was to change the tie rod ends out for ford capri ones. in that car, going down a straight road with irregularities on one side, the car would shimmy all over the place.

bump steer describes a phenominon that occurs when you are going straight. if you are going around an on-ramp and the car darts to the outside of the turn when going over cracks and seams, the tires are skipping sideways.

 

Not exactly. All Proteges, and all other strut cars, exhibit some degree of bump steer. A variety of things can cause bump steer; in the case of the Protege, it's the inherent geometry compromises of McPherson struts, and I also suspect that suspension bushing deflection has something to do with it too.

From a later post:

There isn't really such a thing as "true bump steer." Bump steer is a generic term for any change in steering angle caused by changes in suspension position. All sorts of things can cause it.

BTW I suspect that the reason why Ford Capri tie rod ends helped your Spitfire's bump steer problem has to do with the suspension geometry, not steering rack movement. FWIW many older cars exhibit horrid amounts of bump steer because most automotive engineers in the early 60's didn't understand many basic concepts of suspension design.

Yeah, I'm nitpicking.

 

Thx guys well it looks like when I get back Ill throw on that pro-kit`, some bilstein inserts and maybe some mp3 bump stops if I can find em cheap and will do with what I have at that point.

Again it isnt a big thing, just because, like others, I like pushing the G's(damn that sounds gangsta =P) as taking those 25mp ramps at 50-60 =)

feels the same as torque steer, but as I said it is from hitting cracks or bumps and not just the pull of the engine/FWD combo coming off a line. I havent noticed too much of the latter from my p5, just some "bump steer" however you define it.

 

the best idea is not to take bumps at speed while cornering. they disrupt the suspension on any car and make it less stable. ive noticed its worse on macpherson strut cars on this one spot where i notice it every time, but its a problem on even our rwd porsche

 

try avoiding bumps in South Carolina... much worse than southern cal

 

ahem(Well this is little of topic)


OR

We can send mass emails to the governers of all states asking and asking and asking them to fix all the road

N.VA residents/DC/S.MD, you guys know what I am talking about
the roads are extremely bad, you can shoot yourself from it
Seriously, there isn't a road that I know that isn't repavaed or not cracked in a way that will drive you crazy

but, that is live......

BTW... This thread is a very good in explaining the diffrence....Thanks!