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zob

Torque steer after bush replacement

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zob

My Mk2f used to suffer from some pretty 'fun' torque steer - caused, I assumed, by the fact that one TCA-ARB bush was all but disintegrated and the other a totally different shape/make.

 

After replacing the TCAs and ARB and getting the tracking done the front end feels great but on the first motorway drive today its evident the torque steer is not only back but different and in the opposite direction!

 

On hard acceleration or deceleration (I assume shifting enough of the car's weight around) the steering bias feels to swap sides - it almost feels like one wheel shifts ahead of the other on deceleration and then the other way round on acceleration if that makes sense? The old torque steer was a momentary impulse that needed to be countered - this feels more like a constant bias.

 

I assume this is likely to be the alignment of the ARB in its bushes or the castor angles or a combination of the two. How should I go about adjusting this? 

 

Or have I got this all backwards and there's something else at play? Anyone else gone through this?

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caretakerplus

Suggest that you use an accurate tyre pressure gauge as a first step to sorting the problem.

After that, a steering geometry check should identify the problem. (I am assuming that your suspension is standard.)

Regards

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dvderlm

Are the front suspension top mounts equally shagged?

I imagine one could shift under torque input, but never felt that myself.

 

Any weird tyre wear from worn ARBs?

Does it go straight-ahead hands off the wheel on a flat road with just enough gas to be constant speed at 20 to 40mph?

I assume the tracking was done right. Sounds like it.

 

And just pulling away from rest do you need to correct the steering at all?

I once had a worn out hub that appeared to pull left despite tracking adjustment.

If with engine off you press hard on the brake pedal then turn the wheel left then right from centre do you get a clunk?

Does it then not clunk with brakes off?

Then I'd investigate for wheel play.

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zob
1 hour ago, caretakerplus said:

Suggest that you use an accurate tyre pressure gauge as a first step to sorting the problem.

After that, a steering geometry check should identify the problem. (I am assuming that your suspension is standard.)

Regards

 

Thanks - i'll check with another gauge, although the tyre pressures havent been touched since before the bushes were done. Yeah - everything standard, no lowering.

 

1 hour ago, dvderlm said:

Are the front suspension top mounts equally shagged?

I imagine one could shift under torque input, but never felt that myself.

 

Any weird tyre wear from worn ARBs?

Does it go straight-ahead hands off the wheel on a flat road with just enough gas to be constant speed at 20 to 40mph?

I assume the tracking was done right. Sounds like it.

 

And just pulling away from rest do you need to correct the steering at all?

I once had a worn out hub that appeared to pull left despite tracking adjustment.

If with engine off you press hard on the brake pedal then turn the wheel left then right from centre do you get a clunk?

Does it then not clunk with brakes off?

Then I'd investigate for wheel play.

 

Pulling away it runs straight and also feels straight when in equilibrium ('hands off' at speed it tracks a straight line). Tyres look the same both sides in terms of wear. Just tried rocking the steering with the brake pressed hard and no clunk.

 

Could the left/right position of the ARB affect things? When I put the new bushes on the bar it obviously clamped the bar to the position the bushes were installed (the bush housings only have one position but the location of the bar in the bush might be wrong?). 

 

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zob

Top mounts seem fine - don't think they're that old

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kiran_182

Youll need to track it after the work has been done as it will have been tracked with the wear in place

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zob
2 hours ago, kiran_182 said:

Youll need to track it after the work has been done as it will have been tracked with the wear in place

 

Oh certainly - got the tracking done after I replaced all the bushes. I'm guessing you mean i'll need to get the toe alignment done again after fiddling with the ARB position?

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zob

Right - did some tests (why does driving cars like these so often feel like being a bloody test pilot?) and I think I'm getting closer. The skating steer is only present when the car is accelerating or decelerating sharply - the effect isn't replicated by braking at any speed.

 

When the throttle is lightly blipped (in either direction, i.e. taking the pressure off or putting it on) when moving there is a distinct 'clunk' associated with the steering motion. The 'clunk' noise doesn't appear in any other circumstances and isn't steering related (i.e., doesn't happen just from being at full lock like a dodgy CV joint might). I can reproduce it with really light 'blips' from the throttle so I don't think its coming from weight shifting around. It almost reminds me of when you pedal hard on your bike suddenly and theres a clunk as the freewheel moves a fraction before the pawls engage hard against the hub.

 

I'll jack the front up and check all of the fasteners to see if anything has come loose later - anything else I should check while I'm under there? I checked both front wheels for play after the last round of work and didn't feel any play.

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zob

Well if this isn't the cause I don't know what is.... slightly frightening

IMG_20190617_1112042.thumb.jpg.9ab1358c481fdec0a9f5707458547ef3.jpg

 

The 'lock' nut at the end of the ARB had vibrated loose - makes sense that the skating motion would come from a rather variable castor angle...

 

 

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zob

And the clunk was a combination of the ARB wobbling around in the TCA and this.....IMG_20190617_1127058.thumb.jpg.26bf2bfccfe8b5204e33f3422c1aca01.jpg

 

The counterweight on the OS driveshaft has given my sump a good whack. Is this sump going to need replacing? Hard to tell whether the scuff is a removal of material or a caving of it in...

 

Going to order some new locknuts for the ARB. It was definitely done up to 75Nm - shouldn't have failed so catastrophically. Thank god I caught it!

 

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dvderlm

Ouch.

 

Original nuts reused on end of ARB?

Do you trust your torque wrench?

 

Looks like dent and scrape, but not much material lost.

Sump is not leaking at that point, but probably worth reinforcing with filler and painting over to stop rust from outside. 

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zob
28 minutes ago, dvderlm said:

Ouch.

 

Original nuts reused on end of ARB?

Do you trust your torque wrench?

 

Looks like dent and scrape, but not much material lost.

Sump is not leaking at that point, but probably worth reinforcing with filler and painting over to stop rust from outside. 

 

Yeah - re-used the nuts. The other side is still at torque, lord knows what happened here. Ordered a couple new OEM locknuts for peace of mind.

 

Well I thought I trusted it! Its a Draper and had it for yonks. Could probably do with checking that.

 

Isn't the sump made of Alu? I'll fill it in and give it a paint anyways.

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caretakerplus

A couple of things about 'checking' the torque of a nut or bolt and torque wrench calibration.

 

The correct torque of a bolt/nut can ONLY be checked whilst it is actually being tightened - It is NOT possible to simply put the torque wrench back on it to 'check' as the initial resistance to turning would prevent an accurate reading - It might even be possible to increase the setting slightly and still get a 'click' out of it without it turning the bolt/nut.

 

A very rough method of checking that your torque wrench is giving something like the correct result is to use a spring balance at a point exactly 12 inches from the centre of the drive square.

Set the wrench to a setting in lbs/ft (ft/lbs if you like) , grip the square in the vice and pull on the spring balance - the wrench should 'click' at the appropriate setting.

This is NOT a super accurate calibration check, as there are some variables - not least, the accuracy of the spring balance (but you could check that against a known weight).

This check is best repeated at two or three settings of the wrench.

 

Regards

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zob
1 hour ago, caretakerplus said:

The correct torque of a bolt/nut can ONLY be checked whilst it is actually being tightened - It is NOT possible to simply put the torque wrench back on it to 'check' as the initial resistance to turning would prevent an accurate reading - It might even be possible to increase the setting slightly and still get a 'click' out of it without it turning the bolt/nut.

 

Very true - I always try and make sure I have enough space around the wrench when torquing a nut up to hit the click in one smooth movement. When I say the other nut was still at torque I mean it hasn't moved from where I torqued it to.

 

I'll see if I can't set up a test rig to check the wrench - it'll be something to do in the evening if nothing else!

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zob

Torque wrench was reading a tad high - used a digital luggage scale at a measured point on the handle and pulled against the wheel nuts (vice didn't grip the socket head enough. All calibrated now - thanks for the headsup!

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zob
3 minutes ago, dvderlm said:

Sorry to disappoint you. Sheet steel at £25 ish.

 

Feld Motorsport sell an alu sump for €240 ish.

https://www.feld-motorsport.de/files/CLASSIC-LINE-ANGEBOTSLISTE-PDF.pdf

 

Ha! Consider me disappointed! I'll have to get on giving that a lick of paint asap. Either that or just swap for a new sump when I next do the oil (which is pretty soon anyways).

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dvderlm

Was it a nyloc nut on the ARB end? Please don't reuse those.

 

I can find N0221414 described as nylock at VWheritage.

but the 7zap picture looks like it could be tapered thread

N__0221414.jpg 

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zob
1 hour ago, dvderlm said:

Was it a nyloc nut on the ARB end? Please don't reuse those.

 

I can find N0221414 described as nylock at VWheritage.

but the 7zap picture looks like it could be tapered thread

 

 

 

It wasn't a nyloc, and looks like it wasn't even a tapered locknut to begin with... Stupid oversight - you live and learn...

 

Yeah I think that description is wrong - would seem strange to use a nyloc when every other nut on the suspension is a tapered locknut. Found two original VW nuts to use either way.

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