Anyone tried fitting a coil spring suspension system? #2
Posted: Sun Nov 15, 2015 11:53 pm
I am talking about a combined spring/damper setup here as opposed
to the short springs that replace the standard rubbers and use the
standard-type dampers.
I too got sucked in by the "Springs are better" concept...
This was until I realised a fundamental problem with the front setup
on the coil-over system.
On a "traditional" car, you had a chassis, and this contained the suspension.
The body of the vehicle then sat on top - So far so good...
Then along came the Mini with a "chassis" that was in two sections,
ie the front and rear subframes. The strength of the body, in particular
the double skinned sills and the roof made up for the fact that there
was a gap between the front and rear sections of the chassis.
So then someone invents a coil-spring setup for a normal Mini.
Great, that will obviously be the "dog's bollocks" and it will be
totally obvious that this will be far better than the standard setup (etc)...
Being as sucker for things that look like the "dog's bollocks", I got
a complete car set and fitted it to my Mini. The ride was good, but the
car did tend to wander about a bit. I did not experience any of the
banging and crashing about, but the vagueness of things was puzzling
me.
I was at MiniSpares in Potters Bar when one of the shop lads suggested
that we go outside and have a look. We popped the bonnet and I stood
in front whilst the steering wheel was wiggled about...
There was movement from the main "tower" bolts - The problem would
be solved by using more "dog's bollocks" stuff in the form of the ally
subframe tower kit. Sure enough, this solved the weaving about and
I was much happier.
Well, this was until I actually sat down and thought about the physics
of the new system versus the old/standard one. Remember that the
subframes contain the suspension, and the body of the car rests on
top. This is NOT how it is with many of the coil spring front setups
that are marketed today. The weight of the car is taken through the
top shock/damper mount which is connected directly to the body.
The kits have a really heavy duty bracket assembly and there is the
facility to put extra mounting holes in as well. "So, what's the problem?",
I hear you say...
The problem is that whilst the weight of the body is supported by
the coil spring via the shock mount, the weight of the front subframe
containing the engine is now HUNG from the body using the tower
bolts and all the other rubber mounts.
- No wonder it was moving about so much!
It wasn't long after this Eureka moment that I put the front back to a
conventional system, with Hi-Lo's and the uprated "progressive" road
type rubber springs. I have left the rear as it was as it is as I have
dispensed with the subframe and used a box-tube arrangement instead.
Working on just about everything at the back is much easier without
the subframe in the way...
(A box section of 80mm x 40mm is a much better bet than the 3" x 2"
(75mm x 50mm) kits that are sold as this leaves the wheels in more
or less their original position).
On the Mini-Marcos, the front was done the same as the Mini with
conventional uprated rubbers and Hi-Lo's a while back but the rear
suspension has always been absolutely rock-hard, even with standard
suspension. A temporary "fix" was to leave the subframe in situ and
try the coil-sprung rear setup - This was a fantastic improvement and
I wish that I'd done it years ago. Most recently I did the 80mm x 40mm
box section conversion and I am about to get the car MOT'd and on the
road again after 7 months. Dumping the subframe and using a box
section instead resulted in a weight saving of about 11Kg.
Conclusion:
My recommendation would be to have a "normal" setup at the front
and coil-springs at the rear, either with or without the subframe.
Ian
to the short springs that replace the standard rubbers and use the
standard-type dampers.
I too got sucked in by the "Springs are better" concept...
This was until I realised a fundamental problem with the front setup
on the coil-over system.
On a "traditional" car, you had a chassis, and this contained the suspension.
The body of the vehicle then sat on top - So far so good...
Then along came the Mini with a "chassis" that was in two sections,
ie the front and rear subframes. The strength of the body, in particular
the double skinned sills and the roof made up for the fact that there
was a gap between the front and rear sections of the chassis.
So then someone invents a coil-spring setup for a normal Mini.
Great, that will obviously be the "dog's bollocks" and it will be
totally obvious that this will be far better than the standard setup (etc)...
Being as sucker for things that look like the "dog's bollocks", I got
a complete car set and fitted it to my Mini. The ride was good, but the
car did tend to wander about a bit. I did not experience any of the
banging and crashing about, but the vagueness of things was puzzling
me.
I was at MiniSpares in Potters Bar when one of the shop lads suggested
that we go outside and have a look. We popped the bonnet and I stood
in front whilst the steering wheel was wiggled about...
There was movement from the main "tower" bolts - The problem would
be solved by using more "dog's bollocks" stuff in the form of the ally
subframe tower kit. Sure enough, this solved the weaving about and
I was much happier.
Well, this was until I actually sat down and thought about the physics
of the new system versus the old/standard one. Remember that the
subframes contain the suspension, and the body of the car rests on
top. This is NOT how it is with many of the coil spring front setups
that are marketed today. The weight of the car is taken through the
top shock/damper mount which is connected directly to the body.
The kits have a really heavy duty bracket assembly and there is the
facility to put extra mounting holes in as well. "So, what's the problem?",
I hear you say...
The problem is that whilst the weight of the body is supported by
the coil spring via the shock mount, the weight of the front subframe
containing the engine is now HUNG from the body using the tower
bolts and all the other rubber mounts.
- No wonder it was moving about so much!
It wasn't long after this Eureka moment that I put the front back to a
conventional system, with Hi-Lo's and the uprated "progressive" road
type rubber springs. I have left the rear as it was as it is as I have
dispensed with the subframe and used a box-tube arrangement instead.
Working on just about everything at the back is much easier without
the subframe in the way...
(A box section of 80mm x 40mm is a much better bet than the 3" x 2"
(75mm x 50mm) kits that are sold as this leaves the wheels in more
or less their original position).
On the Mini-Marcos, the front was done the same as the Mini with
conventional uprated rubbers and Hi-Lo's a while back but the rear
suspension has always been absolutely rock-hard, even with standard
suspension. A temporary "fix" was to leave the subframe in situ and
try the coil-sprung rear setup - This was a fantastic improvement and
I wish that I'd done it years ago. Most recently I did the 80mm x 40mm
box section conversion and I am about to get the car MOT'd and on the
road again after 7 months. Dumping the subframe and using a box
section instead resulted in a weight saving of about 11Kg.
Conclusion:
My recommendation would be to have a "normal" setup at the front
and coil-springs at the rear, either with or without the subframe.
Ian