Bouncing rear end !!

[Steve T]

So how do I stop my rear end bouncing up and down then. Above about 50/60mph on motorway, my rear end starts to oscilate and bounce up and down about 3 times per second, quite uncomfortable at times (unless lucky enough to have passenger with large breasts !!).

 

Its a 2006 SV with standard shocks (billys) not adjusted, just fitted from factory at build. Checked tyre pressures, 18psi cold and about 20 to 22 warm (ie after 30 miles of motorway driving etc). Interestingly having checked them both at the start (rears) at 18, today i checked them straight after a 30 mile motorway stretch and one was 22 the other was 20, but they both cooled to the same 18.

 

I have changed wheels (with tryes) to eliminate wheel balance/tyre etc and still get the same effect.

 

On a very smooth surface it drives great, but as soon as i negotiate a bump in the surface it sets about bouncing. I have a rear ARB and watts linkage set to 2nd hardest position.

 

Anyone got any ideas why this happens, is there something that needs to be adjusted ???

 

Have done 1500 miles from new build and it has been there from the start but only noticable at 50/60 mph plus on non smooth surface.

 

Editted to add, had my Powerspeed zaust fitted today, top blokes, took them nearly 5 hrs to fit cause my 'std' SV didn't seem to match their jig, seems the newer SV engine mounts are in a different position (1/2 inch or so and slightly taller), they had to modify 2 of the primaries to get them to fit but they did a great job, cheers Dave !

Oh yes, wow, what a transformation, lots of loverly torque !!

 

Edited by - Steve T on 6 Jun 2006 22:19:23

 

Edited by - Steve T on 6 Jun 2006 22:22:39

[Petrolhead]

It sounds like the springs are too hard but thats supprising on a std car.

 

Are you a light person?

 

NE7Club Web Site

R5 no 65 😬

[Steve T]

errr never been called light, well not recently anyway, about 100kg !!

[Colin Mill]

Its hard to believe that it could be the shockers too light but from what's happening its sounds possible. Do you get the same sort of bounce over speed humps at low speed?

 

[davef]

There's part of the Surrey stretch of the M25 where my seven turns into a bucking bronco at about 50-70 - I've put it down to the road surface (it's concrete panels and I assume the spacing of the expansion joints is hitting a resonance). Otherwise on other road surfaces it's fine (it's a superlight with adjustable suspension)

 

Dave

[Steve T]

I cant recall noticing it at low speeds, but it may be the case.

[Steve T]

You might have the answer, ive only noticed it on M25 between J10 and 12 and on the M20 on the stretch between Maidstone and Ashford.

[Phil Bishop]

There's a stretch of the A12 southbound past Chelmsford that has done this to both the Sevens I have owned.

[davef]

Steve - as long as it is fine elsewhere, I wouldn't be too concerned if it does it on those two stretches of motorway

 

Dave

[Unclefester]

Yep! I've noticed this on that part of the M25.....what an appalling surface...it's just the wrong frequency for a light car, threw poor Twinkerbelle all over the place.

 

It wasn't so bad in the 2002 SV though. Are your shocks set too light?

 

NICE PLATE!!!

😬 😬here *eek*

[WILL FLY]

Davef has hit it on the head, when I was taking my newly built car round the M25 for the post build check, I thought it was falling apart when I hit the resonant frequency, I nearly did a Clarkson. 😳

 

Its even more fun following a stiffly sprung VX round the M25, they hop and skip like Mike Tyson.

 

Roy.

 

See willfly.net for more info.

If you don't spin you ain't trying

Happiness is knowing you have just a tad too much power

DVA 1.8K R345

 

[Steve T]

Im a bit of a numpty with suspension, i fitted the Billy's as they were supplied out of the box, do they need setting up ? They have 2 ally rings, presumably for adjusting the preload or spring rate, was i supposed to do something with these at the build ?

 

Steve

 

1,000 miles so far and counting !