My expensive journey with bumpsteer and a tribute to Albert Fang - WP Auto

[advocates]

Bro, the steering system needs to work by transmitting the force from the steering wheel towards the road wheels with some amount of feedback for feel. this force if its going the otherway ie from the road wheel back towards the steering then its bumpsteer. in both cases the steering rack is the media. the bushes you mentioned are used to create frictional force within the rack to limit this force from being transmitted both ways. it being just a poly bush, does not care which way the force but will give the resistance while its wearing. its a stop gap measure for now but the unintended force is still there per see.

i have simulated bumpsteer before and find them related to the offset that you run on the front wheels. found that the further you operate from the originally specified wheel offset, the more bumpsteer you get. you may want to look at this.[/SIZE]

Hi tropos,

Thanks for the input. I agree on the offset principle..that is why I changed my 18 inch breyton to the original rims with the correct offset..to no avail. I also agree that the bush is a stop gap measure and the unintended force is still there..but it greatly minimizes the force transmitted.

I am wondering whether it is the steering rack. Although I have replaced my steering rack, it was a used unit and could be defective as well...but Albert cannot confirm whether the rack is the culprit and he has no spare unit for me check...

 

[tropos_net]

bro, what is the original rims offset? the breytons offset?

steering rack is only a linear mechanism with preset rack to pinion ratio. the fluid is there to both power assist when needed and also offer some damping force from the force coming upwards to the steering. fault in the rack can only be free play in the pinion shaft or leaky seals.

regarding bushes in the rack, there are teflon (like what you have now), copper and brass. i find copper to be the best as they do not crack like the teflons. both the machining tolerances of the bushes and their length would dictate the frictional force exhibited. a thing to note is, while this frictional force by the bush is limiting the upward unwanted force, the power steering would need to work harder to assist the downward going force.

another thing which came to mind: is yr steering wheel now is of smaller diameter than the original?

 

[advocates]

Hi tropos,

Tx for your valuable input again. The e46 offset should be from ET 40 to ET50. I can't remember the offset for the breyton though. I changed it caused I didn't like the 18 inch rims. I changed it to ori rims Style 89 with an offset of 47. Then I swap rims with my friend and the rims have an offset of 40.

One thing I note though, if the tires are thicker profile, the bumpsteer is much lesser.

steering wheel is smaller diameter as in the turning radius reduced after installation of the bush? Yes.. .

Again, thank you for your input.

 

[tropos_net]

you are right at offset 47 there should not be any bumpsteer. i have taken the offset gradually way down till ET22 and at that point there was plenty of bumpsteer plus the dreadful scrub radius issue.

steering wheel diameter which i was referring to was the steering which you have fitted inside the car. some had gone on MOMO and the likes for smaller diameter which will also hv it effects. i know the ori is big and ugly with all the bells and whistles on it.

tyre profile should the calculated from the original wheel size as you need to get back with the right overall wheel height +/- a little. i read somewhere that you have a complete spare rack system. if in doubt you always send in this spare rack for refurbishing in places like sun eng hup or hitec recon. places which refurbish the autobox will normally also refurb steering racks. at least then you are sure that rack is as good as new.

btw the pinion valve fitted on the rack will need some attention as well. if its worn/not functioning well, it would be sending the high pressure fluid the wrong way in the circuit. on the assembly holding the rack and pinion shafts there is a york adjustment needed. this part is usually shimmed just the right amount so that the assembly does not rattle.

if you had completely reverted to the std factory system, it quite hard to understand why the bumpsteer is there!

 

[BlackE90]

.hey guys, can you share exact adress, if not GPS coordinates, of his shop ??

Bro, here's the address & GPS coordinates

WP Auto
No.41 Jalan 3/5
Pandan Mewah Industrial Park
68000 Ampang
Selangor.
Albert Fang 012-2017792
GPS N03 07.737 E101 46.133

 

[xcrave]

With all the Germans and such... it boils down to... what are the fix had been used ?

Pictures guide will be best. Then again i agree on the offset PLUS RIm Width, i found out that when i switch to 8jj front and 8.5jj rear; setup... bump-steer became worse and this is caused basically by more area of contact transferred to the steering.

If this bush-nylon thing can reduce that imagine the impact it gives to the other members?

 

[seewai]

Bro, here's the address & GPS coordinates

WPAuto
No.41 Jalan Mewah 3/5
Pandan Mewah Industrial Park
68000 Ampang
Selangor.
Albert Fang 012-2017792
GPS N03 07.737 E101 46.133

Partially missing road name added in blue.

 

[advocates]

you are right at offset 47 there should not be any bumpsteer. i have taken the offset gradually way down till ET22 and at that point there was plenty of bumpsteer plus the dreadful scrub radius issue.

steering wheel diameter which i was referring to was the steering which you have fitted inside the car. some had gone on MOMO and the likes for smaller diameter which will also hv it effects. i know the ori is big and ugly with all the bells and whistles on it.

tyre profile should the calculated from the original wheel size as you need to get back with the right overall wheel height +/- a little. i read somewhere that you have a complete spare rack system. if in doubt you always send in this spare rack for refurbishing in places like sun eng hup or hitec recon. places which refurbish the autobox will normally also refurb steering racks. at least then you are sure that rack is as good as new.

btw the pinion valve fitted on the rack will need some attention as well. if its worn/not functioning well, it would be sending the high pressure fluid the wrong way in the circuit. on the assembly holding the rack and pinion shafts there is a york adjustment needed. this part is usually shimmed just the right amount so that the assembly does not rattle.

if you had completely reverted to the std factory system, it quite hard to understand why the bumpsteer is there!

My steering wheel is the original from factory. Haven't changed it. The pinion valve on the rack is new to me. Will ask the mechanic to have a look at it.

My spare rack is a refurbished unit. A friend of mine bought it and after installation, there was no bumpsteer on her car....

Much appreciated. Tx.

 

[advocates]

The following links are quite helpful for those who experience bumpsteers.

http://www.e46fanatics.com/forum/showthread.php?t=511206

http://forum.e46fanatics.com/showthread.php?t=481780

The first link seems to suggest that caster is out of specs as the root cause of bumpsteer.

The second link attributed it to power steering pump. However, for my case, all the mechanics are of the view that the PS pump is not faulty.

 

[tropos_net]

looks like you may need to look at replacing the top shock mounts to rid of out of spec caster. or well maybe, you need the alignment parameter readouts first just to be sure. does it look worn right now (very shallow dip at the top center plastic cover is)? also control arm bush condition is mentioned, is that OK on yrs?

 

[advocates]

Have checked the top shocks mount. It is ok.To be sure, Albert replaced it with a brand new top mount and since it did not solve the problem, he put back the existing top mount. The control arm bush was just replaced. Any possibility of steering pump issue?

 

[oolork]

hehe.. I got the blue nylon in my rack too.. with the new coupling, the bumpsteer almost near to 0.
I think we are the 2 guinea pig with some good result.

 

[advocates]

Hi oolork,

U did yours at Albert's ? I agree with tropos that whilst the bumpsteer is almost near to 0, it is still actually there. Out of passion and curiousity, I want to pursue the bumpsteer issue which means more money to be spent (althought I am selling off my ride). Now I recall that when I first have the car, there were camber plates in the front but had to remove it when I replaced my absorber as the installer overtighten the plates. If I cant recall, there were no bumpsteer prior to removal of the camber plates..I wonder whether with the camber plates, one can adjust the caster as well..will check with my alignment guy on this.

Btw, after installing the bllue nylon bush, do you think your turning radius has been reduced?

 

[oolork]

Do let me know the outcome from you alignment guy.
About the turning radius, it supposed to reduced but seem mine not that significant.
Anyway, I will remove it soon to try another fitting, and then I will measure the radius.
will update.

 

[wutty]

Bro advocate, I had similar problem like yours but with my e39. I had both bumpsteer and rattling that sounds like a thick metal rod rattling in a plastic pipe when going over uneven road at low speed.

Just like you I have replaced many parts including those you mentioned. When I first got my car 12mths ago, the problems were mild but after about 2-3 months they got worse and became very irritating, especially the rattling sound.

Last week even after replacing the steering rack and coupling and new complete absorber+kits etc, still couldn't fix it. One night, this was a week after I left the car with my mechanic, he called me up and happily announced that he had finally found the source of the problem. (he has been trying for months, every tine I send my car in for service or repair, he would look into it)

It was one of the upper control arm bush which I replaced when I first got the car. They still appear to be in very good condition but a bit soft that allows excessive movement. My previous mechanic who replaced them told me that they were German product and the current mechanic says they look like Lemforder. So to be fair, they could be but I am not 100% sure it is Lemforder.

He tried to get original BMW ones from Bavarian Auto, but they need to order from Singapore and it may take several days but I needed the car back already. So he searched the chop shops and found two good upper control arms with BMW bushes.

He replaced them and now both the rattling and bumpsteer are gone. Hope this helps

 

[advocates]

Hi wutty,

Thanks for sharing. When I first got the car, I replaced mine with Lemforder and after 6 months, it cracked! I did try to get the ori control arm bushes but to no avail. So I got myself the PU BUsh. It helps a lot but squeeks everytime i brake. So I removed it and replaced with meyle..but it was of no help. Will ask Albert to help me to source for the ori bmw ones.

 

[advocates]

This is how the nylon bush looks like ...

View attachment 24662

 

[oolork]

My bad, coz the bush fixed to the right so no radius reduced making u-turn.
Yes, it about 70 degree lost at end to left.

 

[astroboy]

I thought bumpsteer is part of the steering feedback? One of the traits of an Ultimate Driving Machine. Car with no bumpsteer got drive feel meh?

 

[wutty]

I thought bumpsteer is part of the steering feedback? One of the traits of an Ultimate Driving Machine. Car with no bumpsteer got drive feel meh?

The bumpsteer I experience is a bit excessive that I can see the steering wheel turning on its own 5-10 degrees when driving straight slowly on uneven road. It is not just feel.