Soft front suspension

[Boomer21]

I have a Jan 2015 plated PC LS Challenger which is in stock trim. Originally purchased as a 2t caravan tow tug and light 4WD escape vehicle but the wife has taken to ocean cruising more .

The issue is the front suspension, It bottoms out over shopping center speed bumps at @ 5-10 kph... been like that from new. I have to crawl over them at @ <5 kph or it drops onto the bump stops on the other side. Its starting to irk me no end.

The vehicle doesn't bounce once over the speed bump so I assume the struts rebound damping spec's are still ok. The rear suspension is fine.

I've searched the forum on 'suspension' but its all mostly about lift kits and brands which is not what I'm after or asking.

I just want to stiffen up the front suspension so it matches the rear which is fine over said speed bumps.

Are the stock springs too weak or the struts under dampened in the compression stroke?

Do I need stronger springs in STD height with stock struts or better dampened struts with stock springs? or both?

Does anyone have similar issues and what did you do to make it better?

Vehicle is mostly a town car with the occasional 2 up black top touring / interstate runs.

Looking fwd to your input.

[nj swb]

First step is to confirm that your front suspension hasn't sagged excessively, to the point that you don't have enough bump travel.

Please measure your front "eyebrow height" (EBH) from the centre of the front wheel to the edge of the wheel arch, measured vertically. That information will help us narrow down possible problems, and appropriate solutions.

It could still be your shock absorbers. My Shorty was horrible in the local shopping centre, the speed bumps were really harsh. Replacing the 70k km old front shocks with OME, but keeping the factory torsion bars, made an unbelievable difference.

[old Jack]

Hi Boomer,

Your post really surprises me as your car is only 3 years old and if your signature if correct then you do not have any added weight on the front axle (bull bar, winch, aux battery or aftermarket underbody plates, is this correct?

Are you 100% sure the suspension is bottoming out? Best way to check is to put some masking tape on the compression bumpstops then go for a drive and check for witness marks on the tape.

What are your ride heights, measured from centre of the hub to the underside of the wheel arch in a vertical line?

I have had factory coils and struts, Lovells 30mm raised coils with a 10% increase in spring rate combined with Bilstein struts and now I have Dobinson raised 40mm comfort coils with a lower spring rate than factory with Dobinson MT struts and they ride better than either of the 2 previous setups, and I have 60kg of extra weight over the front axle. I have come to the conclusion that the factory coils are too high in spring rate and the struts too hard on compression and too soft on rebound.

OJ.

[Boomer21]

Thanks OJ and NJ for your replies.

OJ, yes the car is completely stock, bought new in Aug 15.

As I said earlier, It has done this since new.

I've been driving and riding motorbikes for a long, long time and spent 38 yrs in the Army driving the craprovers we had to have on/off road before the new G wagon came in, I think I know what suspension bottoming feels like from the seat of your pants being a passenger in my senior yrs with a few Fangio's at the wheel without the 'crushing the tape test' but I can do that as well.

My 06 Suzuki GV had a better front suspension compliance over same shopping center speed bumps but the 2.7l V6 is a few hundred kilos lighter than the Challengers diesel lump.

NJ, I was thinking the same, where mitzi may have fitted under rated/lower spec struts to the front on my 'runout' model compared to previous PB and early PC models.

I'll do a EBH measurement tomorrow and tape test over local center speed bumps and post it.

Thanks for your replies.

[amec]

I have complete stock front strut assemblies you can have for free if you want a stock replacement. But Wamberal to Brisvegas shipping may apoil that.

[Boomer21]

OJ & NJ,

The EBH of the front suspension is :

R 527mm
L 530mm

amec, thanks for the offer but I think i need better front struts other than replacement stock ones. but thanks again for your offer.

[littleriver]

Oztec have standard height suspension on offer ...

[old Jack]

OJ & NJ,

The EBH of the front suspension is :

R 527mm
L 530mm

amec, thanks for the offer but I think i need better front struts other than replacement stock ones. but thanks again for your offer.

Hi Boomer,


Factory ride heights for the front are 542mm +/- 20mm and rear is 552mm +/- 20mm, so you front ride heights are within spec but in the lower half of the range. I do not why there is such a large variance in the manufacturers specifications, Gen 4 Pajero do not have any +/- figures! Ride heights at full compression bump is front 422mm and rear 432mm, this means both the front and rear suspensions have120mm of compression travel.


Did you do the masking tape test on the compression stops?

My feeling is the suspension is not bottoming out but you are feeling the factory strut going hard as the compression valving makes them quite firm on rapid compression.


Are you running factory spec tyres?
What pressures are you running?


Here is some spring specifications for comparison;
Factory 680lbs/inch 312mm free length. 17.5mm wire diameter 7.25 turns.


Kings make the largest range of aftermarket coils but only 1 standard height.

King KCFS-55 750lbs/inch 300mm free length. Standard to 10mm raised height with 10% greater spring rate.
The springs below are all raised height and for a range of additional loads

King KCFR-55SP 750lbs/inch 310mm free length.
King KCFR-55 750lbs/inch 315mm free length.
King KCFR-55H 750lbs/inch 320mm free length.
King KCFR-55HD 810lbs/inch 325mm free length.
King KCFR-55T 380 to 660lbs/inch 360mm free height, progressive rate raised height comfort coil with minimum extra front axle load.


OJ.