springs

[reliant-reviver]

I would look into getting a batch of custom front springs made if anyone is interested? Somewhere along the lines of 40mm lower and 250lbs rating.

[CNHSS1]

wiggedy

re front springs, you mention dropping it an 1", but from what point? SS1 front springs are different to the Chevette they are based on and are renowned as being poor material, so sag badly with age. the correct original ride height for an SS1 is 150mm/6" under each of the 4 jacking points on the sill. I'll wager that your cars is already lower than that.
as for getting new springs made, consider exactly what you want the car to do. Daily driver with rubber bushes and 250lb will feel like a tight-ish, taut road car feel but still handle pot holes and give nice feel if you dont drop below 5" ride height. if to be used as a 'fast road', trackday/sprint car, then id go for 300-350lbs personally as below that the handling beneifts wont be maximised. what tyres are you going to use? decent road tyres or List 1b rubber such as R888s etc? again more grip will need stiffer springs and/or front anti-roll bar really and definitely poly bushes or you will be wasting your cash on springs. Again dont go too low on any spring or else the lower wishbones hit the bumpstops very quickly so your effective spring rate goes up from the spring rate (say 250lb) to double/triple that almost instantly as the bumpstop spring assister comes into play. if you intend on going low, then you need to minimise roll (more to do with roll bars than springs in this case) or again you will induce understeer when the bumpstops increase the spring rate massively.

rears are easier as others have said, its a generic coilover setup. AVO used to list both 14" and 13" 'open' lengths suitable for the SS1s and Spax made 13.5" specifically for the SS1. Personally id go for adjustable spring seat on whatever make you choose, allows for new springs to sag (which they do...) and also allows a bit of adjustment for ride height if fully laden/track work.
Dont go any shorter than 13" open though, 13s fine but 12s are too short really, i have them on my racer and theres F-all travel!

Rear spring rates are even more contentious than fronts (read the various stickies and search for posts on suspension in the SS1 and Competition sections...) but dont go mad on rear spring rates. In my opinion they are the easiest change to bugger up the SS1s nice chassis balance. 225lb are my fave, with 250lb for light track work. A full on racer can handle more, but the rest of the car suspension has to be optimised and has to run much stickier tyres, but your call of course mate.
also remember that due to the nature of the semi-trailing arm design at the rear, camber change (gain) during compression of the suspension also changes the camber but in a fixed manner, it cant be varied. Using 13" or 13.5" open rear shocks will help to stop the rear wheels going into positive camber in droop (also known as 'jacking') but careful adjustment of the damping allied with spring rates and static ride height selection, will stop the car gaining excessive camber and compromising the tyre contact patch under bump or hard acceleration. Often excessive wheelspin off the line is just too much squat, causing the rear contact patch to be reduced appreciably. The pi55-poor method to overcome this is just to ramp up the rear spring rates

Nick & Raz will advise on contcat details for getting custom springs made for the front as they have both done it. Worth listening to the compie guys though, as they have been there, done that and generally learned the hard way what doesnt work (all compies have a box of spare springs )

cheers
CNH

[scimjim]

Nice one Craig - very informative as usual and presumably another paragraph in the hot hatch hunting v2.0 - another sticky I think Phil?

[CNHSS1]

Hot Hatch Hunter 2.0 V3 Mk29 will be available hopefully around next major site update

[petesilcock]

Seconded Jim

This is a question that comes up with regularity and Craig has done a superb job of defining the thoughts today.

Can we add -- I think the bump stops as rising rate rubber items are an important part of the front suspension and should be checked as part of a rebuild. - Is that correct Craig??

[CNHSS1]

yep agree Pete, some ive seen and i know you have too, are that knackered they are like a bath sponge whilst others are fine and the chassis turret has rotted away around them!
I think they ought to be considered as part of the springing medium really, but if the cars too low then it becomes all of the springing, rather than part
At a reasonable ride height, the suspension can compress by a few inches in bump (when viewed at the sill) before the bump rubber comes into play, and then increases the rate to stop the chassis grounding out, which is how it should be imho.

[scimjim]

so providing the bump stops prevents the diff hitting the deck, the spring coil binding and the dampers hitting their end stops - you could change the compressive force and length in line with the complete set up?

[CNHSS1]

Que Mr Fawlty?

sorry must be being a bit 'tick, whats the question?

[petesilcock]

Sorry did not make that clear

The front suspension either by design or mistake (cue Reliant joke) uses the bump stops as an important part of the suspension

Rubber due to the rising rate is a very interesting spring medium

Pete

[philhoward]

Sorry did not make that clear

The front suspension either by design or mistake (cue Reliant joke) uses the bump stops as an important part of the suspension

Rubber due to the rising rate is a very interesting spring medium

Pete

Worked in the Mini well enough...

[philhoward]

Nice one Craig - very informative as usual and presumably another paragraph in the hot hatch hunting v2.0 - another sticky I think Phil?

Sort of - have added it to the words of wisdom already proclaimed here..
viewtopic.php?f=4&t=1859&start=0

[CNHSS1]

Sorry did not make that clear

The front suspension either by design or mistake (cue Reliant joke) uses the bump stops as an important part of the suspension

Rubber due to the rising rate is a very interesting spring medium

Pete

Sorry Pete, but it was Jims question i didnt fully understand.

[scimjim]

sorry Craig, it was more of thinking aloud than a question - and some of it was b@lls when I thought about it some more

The bit that did make sense was better explained by Pete and Phil - the compression properties of rubber (as per mini "springs").

Bump stops are largely ignored - certainly on a road car - and are purely there to stop the damper hitting its end stop or the coil binding. Race cars tend to use harder compounds such as polyurethane blocks.

A conventional coil spring is fairly linear in compressive force (Hookes law) until you get to approximately the last 20% of its travel (due to the end coil design). If a bump stop was engineered correctly, it could be used as a secondary spring which could increase your resistance at a certain point of coil spring travel?

I'm sure someone far smarter than me has examined it properly and it's too late to go too deep - oh and did I mention that I have a hole in the back of my head where a doctor took out a subcutaneous cyst yesterday? He probably got most of my brain cells too

[CNHSS1]

firstly Jim, i have a spare sump plug to fill the hole in ya bonce if it helps? or a gearbox plug if it was a big 'ole? should ensure the grey matter and Guinness doesnt leak out...
hope you are feeling better soon ScimBoss

as for the bumpstop rubber, i beleive they have been used as 'spring rate risers' by many manufacturers for some years, i suspect even the old chevette ones on the SS1. They are certainly too long and of a shape that allows contolled compression more than just a bump stop in its purist sense to stop the suspension metal bits crashing together on our lovely UK roads.

Bit of a tangent, but certainly many race cars use the bump rubbers over the shock shafts as a rising rate spring, beauty there is that even if you change teh spring, the 'bump rubber riser' stays in place, as does its effect. Im sure there is a way of measuring the rising rate type poly rubber, but beyond me im afraid, suspect a shock dyno or spring tester rig would be needed, but essentially any increase in rate from the rubber, whether simply a linear 'X' lb/in addition to your fitted spring rate or with some of the tapered and stepped versions ive seen, an increasing with compression rate, will help on ultra low, stiff cars if they have enough mechanical grip (tyres/suspension) and possibly aero grip to exploit it.
a lot of single seaters tend to have a third spring, which doesnt act in roll, but only in chassis bump, mainly due to increased loads from the aero package at speed. On smaller lighter bike engined hillclimb cars these are often rubber 'springs' but on F3 and F1 cars are metal coils (as poor old Massa found out when one hit him on the skid lid...)

[wiggedy7]

hi all
im going to contact gaz to see what they can do to get some gineric coilovers with hight adjustment. however im not sure what to ask them for?
am i looking for a coilover with hight adjustment 13.5" with 1/2" bolt holes either end with a 225 pound spring (fast road use)? its all very confusing