Hey all, after a long time lurking seems like I finally found an issue not yet discussed in the forum.

I'm from italy so I apologize in advance for my broken english.

I'm looking to give some love to my first car, a 2006 Octy 105PD Elegance with 300k KM that was handed me down from my mother after she got her Mk3 TDI a couple of years ago.

 

The car has always been regularly serviced and is in good mechanical shape, unfortunately I can't say the same about the handling and ride quality.

In particular in the last few months I have been pursuing a problem regarding the rear suspension, that caused the ride to be quite "springy" over speed bumps and squirmy on potholes and manholes, especially in short radius corners.

 

I was able to fix the springiness by replacing the shot shocks, but replacing bushes and drop links seems to have done very little for the perceived lateral play of the rear axle.

I replaced all the arm bushes that seemed to have play (or were easy enough to replace, as preemptive maintenance) but the handling hasn't improved at all, if anything the new stiffer bushes seem to have exacerbated the problem, to the point where last week a friend riding with me noted how the rear end "does not feel right" over potholes and such.

All the bolts are fastened at the torque spec, wheels don't shake when yanked and tires are at the correct pressure.

 

Any idea on what should I investigate next?

Rarely ever read about them, but could it be the rear subframe bushes?

The car has done several thousand km fully loaded with a boat in tow across multiple summers, if that helps.

 

Thanks

 

Have you checked/changed the rear springs? If it has been towing a lot they might be quite soft by now, OR if your mother had them upgraded for towing they might be too stiff for standard shocks?

 

Also how certain are you that it is the rear squirming? I changed my rear shocks a couple of months ago (one was doing nothing!) but not the springs, although I did do the drop links because I had an MOT advisory on them that I wanted to get out of the way at the same time. Afterwards for a while I felt maybe the front end was feeling a bit bouncy now that the rear was behaving, I haven't changed anything there yet, I just got used to the different feel! I could be wrong of course, maybe it is still my rear end feeling a bit bouncy because I didn't bother with the springs?

 

I did once replace the rear subframe bushes on my vectra as part of a full rear end overhaul (was cheaper to buy a full bush kit and I was dropping the subframe anyway), I never noticed a difference in handling but it was more a case of 'whilst I am there' than because they actually needed doing. That was probably at 230000 miles (350000km) so I don't think they normally wear out, but if it has been towing a lot who knows?

 

Just a thought, most suspension components when using original rubber bushes are supposed to be torqued up with the normal weight of the car on the suspension. If you don't do this; because the bushes don't rotate once torqued up you can end up setting them in the wrong position so they get over stressed in normal use. It doesn't matter if you use polyurethane bushes because they will rotate and not get twisted up, but they also completely change the feel of the rear end. Make sure you find a safe way to get the weight of the car onto the suspension to torque the bolts, it is not always easy at home without access to a ramp or pit.

You had 4 wheel alignment done?

Thank you very much for your replies

 

14 hours ago, Jim-octavia said:

Have you checked/changed the rear springs? If it has been towing a lot they might be quite soft by now, OR if your mother had them upgraded for towing they might be too stiff for standard shocks?

 

Also how certain are you that it is the rear squirming? I changed my rear shocks a couple of months ago (one was doing nothing!) but not the springs, although I did do the drop links because I had an MOT advisory on them that I wanted to get out of the way at the same time. Afterwards for a while I felt maybe the front end was feeling a bit bouncy now that the rear was behaving, I haven't changed anything there yet, I just got used to the different feel! I could be wrong of course, maybe it is still my rear end feeling a bit bouncy because I didn't bother with the springs?

 

I did once replace the rear subframe bushes on my vectra as part of a full rear end overhaul (was cheaper to buy a full bush kit and I was dropping the subframe anyway), I never noticed a difference in handling but it was more a case of 'whilst I am there' than because they actually needed doing. That was probably at 230000 miles (350000km) so I don't think they normally wear out, but if it has been towing a lot who knows?

 

Just a thought, most suspension components when using original rubber bushes are supposed to be torqued up with the normal weight of the car on the suspension. If you don't do this; because the bushes don't rotate once torqued up you can end up setting them in the wrong position so they get over stressed in normal use. It doesn't matter if you use polyurethane bushes because they will rotate and not get twisted up, but they also completely change the feel of the rear end. Make sure you find a safe way to get the weight of the car onto the suspension to torque the bolts, it is not always easy at home without access to a ramp or pit.

 

14 hours ago, Vrsburnzy said:

You had 4 wheel alignment done?

 

The springs are factory (I was told by my father that the car is equipped with the sportier lower suspension) and from a visual inspection they seem fine, not even a hint of rust and the original paint is barely faded.

Same for the rubber stoppers(?) that slot in the lower control arms, no cracks in them and the rubber is still soft.

 

Regarding torquing the bolts, I was aware of the correct procedure but I cannot get nor me nor my torque wrench under the car when it is on the ground so I had to tighten them with the car on jacks.

I will ask the shop to re-tighten all the bolts once I bring my car in for the four wheel alignment, which I have not yet done.

Regardless, I am pretty sure it isn't an alignment issue or a problem with how I tightened the bushes, because the car goes straight and does not "walk" left or right at higher speeds, rather the issue is most evident at lower speeds, where the rear end feels like shifting to the outside of the corner, giving for a split second the impression of having shopping cart wheels in the back.

After that I can hold the trajectory just fine, it's just the initial turn-in that shows a very apparent jolt, as if the rear suspension as a whole, both left and right side, is shifting laterally to the outside of the corner by an inch or so.

 

In all honesty I know I need to check the subframe bushings, I'm really just hoping that someone would suggest something else I did not consider as the culprit as changing these seems to be the biggest PITA as far as rear suspension work goes.

15 minutes ago, 10mm_socket said:

The springs are factory...rear suspension work goes.

None of which actually answers the question as to whether or not the suspension geometry has been checked!

37 minutes ago, KenONeill said:

None of which actually answers the question as to whether or not the suspension geometry has been checked!

It hasn't.

Have you ever heard of a bad suspension geometry causing such issues?

I haven't found anything of the sort in my researches around the web.

IT does happen, I had serious oversteer on low speed tight radius corners, turned out the rear camber was at almost 3 degrees! Should be 0.5-1.5. Made all the difference to the handling of the car. Though make sure it is a full alignment setup, not just toe angles, but camber, caster, toe etc.

I get all my cars aligned, makes a massive difference, as said above make sure it’s 4 wheel alignment, you rear is adjustable so if wildly out it can cause odd behaviour.

Rear tyre pressure been checked? The pressures on the back of my work van were about 10psi too low and the back end felt completely disconnected from the front. The tyres still looked like they had the correct pressure in so took me a while to figure out.

Edited 20 December, 20196 yr by Updown789
Just realised that the pressures have been checked!