Short stroke suspension

[totta Crolla]

without running very stiff springs, is it possible ?
My current front suspension is using 190lb springs and I would like
to lower the car by about 40mm using short stroke dampers. My concern
with using short stroke and 190lb springs is that it will run out
of bump travel very quickly, I do not want to use stiffer springs.
Anyone have any thoughts on this or have any information on
short stroke damper lengths ? Thanks

[jondee86]

The question of how much stroke you require is directly related to how
much energy dissipation you need. And energy dissipation is dictated by
how big the bump is, and how fast you are going when you hit it

My car is around 40mm down with 3kg/mm springs and AGX shocks. The
front struts had 40mm removed above the perch, and I am using full size
lowering springs. Bump stops are shortened one lump

This works fine around town and faster driving on good roads. Where it
falls short is faster driving on poor roads with lots of dips and bumps. The
faster the car is travelling, the harder you hit the bump, and the greater
the energy the spring/shock combination has to dissipate. Note for the
technically inclined; I may not be explaining this in the correct scientific
terms, but you will get the gist of what I am trying to say

When you have limited travel, the result of hitting a decent bump at speed
is "bottoming out" and a sudden upward acceleration of the vehicle as the
spring rate of the bumpstop approaches infinity. So yeah, if its just for a
daily driver, you can go low without rock-hard springs. But for a race car,
the less travel you have, the harder the spring you need.

Cheers... jondee86

[totta Crolla]

I will try to evaluate how much travel I have with my
suspension as it is now, do you think a cable tie around the damper
rod would work for this ?
The question is then, is the lowered ride height worth the
increase in spring rate ?
Thanks by the way.

[NoHachi]

jondee86 Wrote:My car is around 40mm down with 3kg/mm springs and AGX shocks. The
front struts had 40mm removed above the perch, and I am using full size
lowering springs. Bump stops are shortened one lump

I'm having a hard time wrapping my head around this.. if you lower the top of the damper (car body) by 40mm. Then lower the top of the shock body by 40mm, shouldn't you now have the exact same bump stroke as stock? I know mine does with a very similar setup.
You might be having some trouble with spring-bind perhaps?

Twin tube dampers like the AGX also have small piston area's and as a result take a longer time to devellop damping forces.

[jondee86]

NoHachi Wrote:I'm having a hard time wrapping my head around this.. if you lower the
top of the damper (car body) by 40mm. Then lower the top of the shock
body by 40mm, shouldn't you now have the exact same bump stroke as
stock? I know mine does with a very similar setup.

Maybe I'm more than 40mm down ? I know the Espelir springs were rated
40mm down when I bought them. After I installed them I was only about
20mm off the bumpstops before I cut the struts. I'll have a look in my
notes to see how I assessed the bump and rebound travel when I fitted
the AGX inserts. I know I had to cut the bumpstops to get adequate bump
travel.

EDIT: Thinking about it some more, I spent a lot of time trying to set the
front up to function within the total available operating stroke of the AGX
inserts. There is not a lot of working stroke to start with, and cutting the
bumpstops unlocked another 20-25mm. Then I aimed for 60% bump and
40% rebound.

Cheers... jondee86

[jondee86]

totta Crolla Wrote:The question is then, is the lowered ride height worth the
increase in spring rate ?

There is a set of AE86 coilovers complete with new front spindles, that
ships with 8 kg/mm springs for the front. I fantasised about fitting these
to my car All I would need to do would be to get some 4 kg/mm
springs to soften the "drift style" spring rates for normal road use.

Wrong... the front shocks only have about 60mm total travel !! Fitting
softer springs would mean hammering the bumpstops. So I had to give
that idea away. Spring rate and ride height/suspension travel is always
going to be a compromise. Go low and take the big hits, or go high and
put up with the body roll.

If I get round to spending more cash on my suspension, I will go to a
slightly stiffer spring, say 4.5-5.0 kg/mm, and invest in some Bilsteins
valved for the application. Quality shocks will improve the ride when you
are using stiffer springs.

Cheers... jondee86

[NoHachi]

Totta, is this for your rallying efforts?

If so, just look at the Escort Mk2 setups. Their chassis in GP4 spec is 99% similar to the AE86 in places where it matters. They have decades of rally devellopment behind them. Whatever works for the front running escorts will work on an 86 too. Always easier to learn from the pro's.

[totta Crolla]

Here is the deal, yes the suspension is for my (tarmac) rally car and
yes my suspension for that application is very very good at the moment.
I'm very much a function over form kind of person but I have been
offered some short stroke dampers and Corollas always look good low.
The idea was to lower the car whilst keeping everything else as it is
now, it seems my suspicions about this are correct though.

You are of course correct in what you are saying about Escorts and
sometimes I wonder if Toyota got hold of a copy of the "Ford Escort rally
preparation" manual published by Boreham Ford in the 1970's when
they designed the AE86
Most of the Escort design weaknesses picked out in the book appear to have been deliberately over engineered on the '86 a good example is the way the steering column attaches to the body.
RAS motorsport have made the whole book available to download free and here is a link to one of the pdf's. Interesting stuff

http://www.rasmotorsport.com/Billeder/Mo...n-Rear.pdf

[jondee86]

Aha... I had a feeling yours was a leading question, and that you already
knew the answer If you have suspension that works well for the speeds
that you travel on the roads that you use... don't change it just for the
sake of looking cool. My suspension is fine for normal driving, but it does
not handle big hits well. So I drive within its limitations and suffer the odd
kick in the a$$ from dips or bumps that I don't see early enough

Cheers... jondee86

[Lajoosh]

need info and axperience on this.
i have been planning to build coilovers all around for an 86 with adjustable konis, ae92 insert on the front, ae86 oem stroke on the rear. but i dont like tha fact that i have to push and turn the rear shock to adjust damping, as i would have to disassemble the coilover every time i need to make an adjustment. so im questioning, what if i would use ae92 front inserts for the rear too? lenght is good, mounting eye not a problem.
whats your opinion guys?