johnfm

Question to those who have fitted lowering springs. Got mine back yesterday. Ride is not particularly harsh, BUT, the rear of the car is MUCH MUCH noisier over bumps, especially at very low speed. I'm talking ripple strips or anything, but driving slowly ovre a road with small imperfections in the tarmac generates loud, hollow knocking noises in the rear.

Any clues??

FYI, I have retained the standard shocks(for the time being). The front does not exhibit any extra noise. The ride is not too hard, the ride height is about 30mm lower.

Andy Roe

johnfm,

Just a guess, but it could be the rear shocks bottoming out!

Andy

Adrian

Dear John,
I am sure we advised you that this would happen. Andy is correct. The rear shocks are not valved correctly and they are bottoming out. You have reduced the amount of travel by 30mm which basically means you have moved the piston 30mm closer to the bottom of the shock. Now you have 30mm less travel before the thing impacts something.
Ciao,
Adrian
911C4

johnfm

I am surprised that 30mm will cause bottoming out over small irregularities at low speed (I'm talking 10 mph here!!!).

I will have the garage check to make sure there are no problems with the fitting.

If they are bottoming out, replacement will be pencilled in for next month!

Adrian

Dear John,
It is not the speed it is the force being generated and transmitted through the wheel and the shock absorber trying to counter this. When you lowered the 964, you will have changed the weight distribution as well. Did you have the corner balance/levelling procedures carried out.
Ciao,
Adrian
911C4

johnfm

Yes it was re-aligned etc.

I expect you are right re: bottoming out - its just that the sound seems more hollow and knocky, rather than a 'bottoming out' clunky sound.

Anyone got any contacts for re-valving boge shocks - or should I just replace these ones.

Adrian

Dear John,
I do notknow who can re-valve Boges in England but I would recommend you replace them anyway. They maybe be damaged and then they will leak. However if you change the rears you are also advised to change the fronts as well.
Ciao,
Adrian
911C4

johnfm

My simple understnding:

Springs control how much the suspension will deflect under load. Their stiffness is rated in how much load (in newtons or pounds) is required to compress them by a given linear distance.

So, though the lowering springs are shorter, they are also stiffer than standard. They should require greater loads to compress them.

Shocks are a damping device that control the rate (in metres/sec or imperial equivalent) at which the suspension can travel and rebound. Re-valving them will alter how quickly a bump compresses the spring, but not how far the spring/strut is compressed.


So, still not sure what the hollow bumpy sound is??

Adrian

Dear John,
I am afraid this is where all the original advice comes in. You have used H&R lowering springs correct? These are not significantly stiffer than standard springs. Maybe 20lbs and I am being very generous. I think you also used the progressive versions as well.
Anyway, face what you are facing is very common when you install lowering springs onto standard shocks.
On the re-valve issue what happens on a Boge re-valve that I have seen carried out is they do actually replace the inner parts needed to ensure you get the correct amount of reduced internal travel. Naturally you have to ask the re-valving facilities to compensate for the 30mm lowering. Certainly this service was available to pre Nov 90 build 964s due to the lack of available replacements. I know also that in the USA, this service was also available for Munroe and Koni shocks and struts. Boge support was available via Sachs. I cannot help you in the UK though. It probably is worth purchasing new and correct replacement units to avoid messing around. Both fronts and rears otherwise your handling will be awful.
Ciao,
Adrian
911C4

johnfm

VERY annoyed

got in my car just now to drive to shops - return to see large (1ft diameter) pool of oil where front right wheel was. Not sure if this is oil from damper or engine oil.

Severely annoyed at myself, more than the garage, for tinkering with a perfect car. Will I never learn!!!!

Eric-17

John:

One of my trainers ran into the exact same problem (with his Dodge Neon). He bought lowering springs but did not replace the shocks/struts, against the advice of myself and his mechanic (he's young ). Not only did his car handle much worse at speed, he bottomed out over almost every imperfection in the road. To back up what others have written, it did not sound as you might expect.

Hope you leak turns out to be an easy fix

Have a good day.
Eric

joey bagadonuts

[quote]Originally posted by johnfm:
<strong>Severely annoyed at myself, more than the garage, for tinkering with a perfect car. Will I never learn!!!!</strong><hr></blockquote>

Hang in there! This WILL have a happy ending. Promise.

johnfm

Car is back in garage:

oil leak is front strut failure - no coincidence. After 90k miles, it seems it didn't like the lowering spring OR didn't like the way the mechanic handle it!!


On rear noise, they rode in the car and after 50 yards mentioned it isn't bottoming out and the noise isn't normal. Car is back on the ramp & they are investigating. I expect a large degree of goodwill to be shown by them -0 as they suggested to stick with the original struts. Replacements will cost about £120 each for the the front......

..what do they say..If it ain't broke don't fix it.......

johnfm

<img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" /> <img src="graemlins/c.gif" border="0" alt="[ouch]" />

DougB

Excessive toe-in on the rear will increase road noise quite a bit.

Hopefully they aligned this car when it was lowered as toe-in will increase when you lower the rear end of these cars.

-doug