SRi rear suspension

[Telegram Sam]

I believe, until someone corrects me, that the GSi has IRS rather than the SRi fixed rear beam. How easy, costly, practical, feasible ... would it be to get hold of the bits required in decent nick and do a conversion?

[James McGrath]

Have a look at some of the phenomenal work that btcctroy has put into his project so far and you'll get an idea of how difficult it is to do:

viewtopic.php?f=21&t=4109

The independent rear suspension upgrade starts on page 34.

[Telegram Sam]

Quick end to a long dream! I thought it might be a straight swap with just a few tweaks though I'd have guessed a few more with the Vectra C.

[James McGrath]

Yeah, the Vectra C sub frame is harder to put in but it gives you an idea of the level of work that is required for such a conversion. It's not impossible though, just need to find a fantastic welder.

[Telegram Sam]

Would the GSi substitution be any easier even if the end result was not as good as a Vectra C?

[Super89]

Get some eibach springs & bilstein b6 dampers or similar quality setup. Its what i have on mine and it rides very nice indeed. The whole setup set me back just under £500!

[Telegram Sam]

Straight replacements? I think Humbucker mentioned Gazshocks or something similar and Powerflex bushes but I don't want to make the ride much harsher

[Super89]

Straight replacements mine are yes, No idea on the GAZshockers i had them on a Mini once. Never looked into them for the Cavalier tho.

[Super89]

What setup do you have on there now? Anything uprated will make the ride harsher. Most of the cheap shocker & springs setups off ebay are terrible, All my old items went in the bin LOL

[Telegram Sam]

What I have is SRi bog standard and it would only be worth changing in line with what folk there recommend cos of what you say. Present results are liveable with if the only way of improving would be at the expense of a harsher ride. But I wonder if there's a better trade-off - like with adjustable shockers and playing around with settings. Which led me on to thinking about the GSi IRS ....

[humbucker]

Koni dampers and Eibach springs are a good option too, Iain.

[humbucker]

An IRS conversion would require an entirely new rear floor, wouldn't it?

[Robsey]

Yes the rear floor pan is completely different, and so is the fuel tank set-up and so on.
You get the idea.

If you are still on 20 year old springs -
New springs, dampers, bushes and ball joints would probably make the whole car feel completely different.

Regarding the Vectra-C rear suspension.
It is very effective, but it is a very complex set-up with lots of linkages and bushes.

And to be honest is quite firm - standard GM springs are made from colts-foot rock and snap for fun.
Eibach or similar are much better, but still quite "scrunchy" going over speed bumps etc.
The Vectra-C set-up does not inspire confidence for those who listen for odd noises from their car.

[colin1]

An IRS conversion would require an entirely new rear floor, wouldn't it?

Yes the rear floor pan is completely different, and so it the fuel tank and, and, ....

What I was thinking
Not been to see a GSi for the purposes of buying it but as I understand it, it's an area that should be looked at by the prospective buyer - problems here (tin worm) usually being the deal-breaker (or maker)

[Robsey]

Indeed - GSi floor pans do rot for fun.

So unless you enjoy welding (even in your sleep), many models are simply not fit for saving from the crusher, despite their inherent value and rarity when done up.

[Telegram Sam]

Koni dampers and Eibach springs are a good option too, Iain.

Thanks, just when you'd got me weaned on Gazshocks

RIP Vectra C and I suspect GSi also I think.

If you are still on 20 year old springs -
New springs, dampers, bushes and ball joints would probably make the whole car feel completely different.

I was told that if there was that much dodgy in the suspension etc then the friendly man from the MOT would stop being friendly. It's probably a matter of doing things on an incremental basis depending on the condition (can you assess visually?)

[Lowrider Dave]

GM springs are made from colts-foot rock and snap for fun.

LOL.

I second Eibach springs, I have them on the V6 and are good replacement for standard. I use Bilstein shocks, but Koni dampers are just as good.

[Robsey]

MOTs are down to the examiner's perception of a vehicle's condition.

leaking dampers are an obvious fail.
the basic bouncing the corners of the car is a simple enough test of the dampers too.

Springs - will not fail an MOT test unless they are visually faulty (cracks, snaps or very severe corrosion).

My Cav used to sit 3/4" (19mm) lower on the driver's front corner than the passenger front corner.
Probably due to covering so many miles with my lardy-arse in the driver's seat.
Yet it never failed the test, nor had advisories for suspension.

Usually for corrosion in the underbody / sills or the brake / fuel pipes.

[Telegram Sam]

I second Eibach springs, I have them on the V6 and are good replacement for standard. I use Bilstein shocks, but Koni dampers are just as good.

Sorry to keep banging on about this but what you've installed did that result in a harsher ride?

There are no very obvious faults with what I've got other than that (unlike most of the remainder of the car!) it's still original spec, and I get envious when I hear reports of what other folk have got ..

[humbucker]

GAZ is better than Koni, no question. I was just pointing out alternative options that are at your disposal.

[Lowrider Dave]

Sorry to keep banging on about this but what you've installed did that result in a harsher ride?

Yes, not a great deal but any spring/damper alterations that deviate from factory spec will firm up the suspension characteristics. My V6 has a mild 40mm drop with appropriate Bilstein dampers, it delivers a slightly firmer ride.
Shorter springs are available but this induces a harsh ride as the suspension has shorter to travel when trying to soak up speed bumps and potholes. If matched with correct dampers and polybushed ARB it can stiffen the driving experience and help handling, but really this is mean for motorsport use and not really for everyday use unless you like spinal injuries.

[Telegram Sam]

That's the point - policemen, both sleeping and awake, on the local housing estate don't appreciate the finer points of motorsport, and there are easier ways of landing up with the osteo again. I'm thinking / hoping that if I restrict myself to adjustable GAZshocks or whatever I might be able to get the best of both worlds?

[Robsey]

Coming back to Bilstein.

Febi Bilstein supply a lot of what we would regard as GM original parts.
So dependent upon exact damper model, somewhere in there, there will be a direct equivalent from factory spec.

Although I will be honest - I have no idea what the difference is between B4, B6 or B8 dampers is... just a number to my uneducated brain.
One of the true suspension gurus will probably know this without thinking about it.

Regarding set-up -
There will always be a compromise between wallowy handling and back comfort versus stiffer precise handling with a potentially horrendous back busting ride.

Again - going to the n'th degree.
Wheel and tyre size, tyre pressures, bearing condition, suspension bush condition and so on, can all make a car handle like a blancmange or like a bone shaker.

[Telegram Sam]

... which is why you plug in the CavMk3OC computer to tell you what to get and what to do with it
I believe I made the mistake earlier of assuming that when Vx-GM were making Cav's and Vectra's in the 80's and 90's they standardised as much as they could on common floorpans and things and that to convert from one model to the other (SRi > GSi) was just a matter of swapping a few peripherals. Easy - or not.

[Super89]

I have Bilstein b6 all round on mine Sam, Its a nice ride for the odd weekend bit of fun but i would not want to use the car everyday. Also tyres make a huge difference, I have yokohama ad048s and they have made the ride even harder and alot of tyre noise but the grip is mental.