AVO coilover shocks

[catswhiskers]

I am currently setting the ride height of my car and need to make fine adjustments. I have set all the shocker mounting points at the correct height for tarmac settings but feel that the rear is about 20mm too low now. Am I right in thinking that I can just screw up the bottom spring seat several turns to add more 'pre-load' to the spring, therefore lifting the body? :confused:
Seems to be logical but I'm no suspension boffin :rolleyes:

Thanks in anticipation of being shot down in flames :D

Fabrizio

[rutthenut]

It will only generate 'preload' if the shock rod is at full extension. And if it did that, the body ride height would not change; it would just increase the stiffness of the suspension when it encounters bumps.

But if you find that jacking up the car gives some free travel between spring and mount, you would be able to change the right height by adjusting it.

This will also have an effect in changing the balance from front to rear, seeing as that is how 'corner weights' are set. With the offset engine, it won't be at all easy to get the weights correct anyway, but there is a fair amount of theory involved.

[strat6v]

Lower the front 20mm for that super low rider kool look.There has been many articles in the bike magazines on this issue. I can't remember the outcome but i think to a degree, it would do it but its not quite the correct way.Probably just makes the arse end firmer. I could use a similar line on the local muppets next time i'm out in chessie, 'Here lass, let me tweak them preload adjusters........ :D :D :D

I have a book by Alan Staniforth, 'Competition car suspenders' if you want to borrow it

[catswhiskers]

But if you find that jacking up the car gives some free travel between spring and mount, you would be able to change the right height by adjusting it.


John, I used the term 'pre load' very loosely(and probably incorrectly). With the car sat on level ground, the shock absorbers are compressed approx. 60% and the bottom spring cup is only screwed up enough to prevent the top location cup disengaging when on full droop. Does this mean I am safe to wind up the bottom seats a bit more? :confused:
I know I'm a bit thick but I mean well ;)

Fabrizio

[strat6v]

Anyway, with all those pot holes around Mansfield i thought youd need to fit long travel kit like the safari cars.

[strat6v]

I plan on having mine set up professionally. I don't have the know how or the kit to attempt it but from what i have heard it is money very well spent.
Once you start it can get very complex. geometry, ride height, damping rates, arb's, etc.

[chris.richard]

I plan on having mine set up professionally. I don't have the know how or the kit to attempt it but from what i have heard it is money very well spent.
Once you start it can get very complex. geometry, ride height, damping rates, arb's, etc.
Did you do your own bump-steer adjustments, or is that going to the pros too? I think I'll get some professional help with my setup too. Any idea how much it'll cost? :eek:

[catswhiskers]

I'm having the whole geometry set up properly by 'man that can' He brings all the kit out to your site to do everything. Sando and me (and probably Bernard) are planning a block booking. I dont think the cost was bad. I'll dig out the info and post tomorrow.

Fabrizio

[guy mayers]

Bumps steer is straightforward to do yourself if time consuming! Remove the shocks and bolt long straight edges to your hubs/discs. Then change the height of the rack using shims until the tip of the straight edge describes as small a curve as possible as the suspension is raised and lowered. It's a once only job that isn't dependant on ride heights but will significantly complicate the suspension set up later and add to your costs.
Guy

[CorseChris]

I made a bump-board a long time ago while struggling with the Marcos. I think it was a Staniforth idea. Two pieces of 1/2" board, about 2' x 10" and 2' x 2', a hinge along the long edge. Fixed pin at one end of what is the vertical board, a cheap dial-gauge at the other, a third piece of board that bolts to the hub or attaches to the wheel with straps, marked with a simple scale each end so you can make sure it's going up & down square. As Guy says, you adjust rack/TRE height until you minimise the movement left/right as the wheel goes up/down. Sounds complicated maybe but really is simple to do. Worked a treat. Setting the bump on the Corse is maybe slightly easier as the rack mouting is designed with adjustment slots. Down-side of this is if you disturb the rack of course! I did ponder some sort of adjuster but figured I wouldn't be removing the rack that often so left it alone. I used spherical joints for track rod ends on my car which allows for more adjustment if you are having problems. Ideal target for bump steer is zero across entire suspension travel (unles your name is Lotus and you design it in for a specific reason). Probably won't achieve this, but get as close as possible around the centre of the range. You can compromise the extreme ends a bit (better to let it go out on droop than bump) to minimise the error in the middle. You should be able to get your Corse to damn near zero top to bottom. IIRC, I got my S to a few thou. across about 90% of the travel. Which reminds me...I need to do it again after changing the pinion! You'll have to keep running from side to side as you move the rack up & down as one side affects the other of course. Two bump-boards would be better....take the spring off the font shock of course.....and a small screw-jack is ideal for moving the wheel up & down.

From your description Mick, I'd just wind up the spring seats for now to achieve the ride height you want then wait for the man with the gauges to set it spot-on. As John says, it's a complicated subject. Dave Walker joked that he leaves suspension to other, smarter people and sticks to engines 'cos they're simple. Bearing in mind how spectacularly wrong I got it chosing a simple spring, I think this is probably good advice.

We did receive an offer of a club-rate block booking for chassis setup while we were at Castle Combe earlier this year. I can't recall the name of the company at the moment, but the chap who runs it was very interested in the cars (thinking of building a Corse). He says he gets an awful lot of kits to sort out.

[catswhiskers]

From your description Mick, I'd just wind up the spring seats for now to achieve the ride height you want then wait for the man with the gauges to set it spot-on. As John says, it's a complicated subject. Dave Walker joked that he leaves suspension to other, smarter people and sticks to engines 'cos they're simple. Bearing in mind how spectacularly wrong I got it chosing a simple spring, I think this is probably good advice.


Agreed Chris. :D
I think the company I'm thinking of are based in Stoke on Trent. Chassistech comes to mind. Sando will be able to confirm this.

See you at Donnington anyway.

Fabrizio

[John]

According to the aforementioned Mr. Stanniforth it is a common misconception that winding the spring pan up will increase the stiffness of the spring. the spring is the same rate per inch no matter how short it is and therefore cannot become stiffer by being shorter. ( exception is progressive rate springs of course)
Mick I'm sure all you need to do is wind the spring pan up to raise the car!

[catswhiskers]

Thanks for that John, I did say it seemed logical. :rolleyes:

Mick