Tuesday, August 22, 2006

"Springtime for BOB"

Springtime indeed!

I went to see Greg Tunstall at the weekend after speaking to him about getting hold of some uprated springs for the big trip to Perth. I really wanted some Chris Witor springs, but the postage cost is prohibitive (more than the cost of the springs!) Greg very kindly gave me a selection of springs to try out.

I'm not particularly interested in changing the ride height, I just want to increase the load capacity so we can carry all we need to go EWE (East coast to West coast and back to East coast again) ... 9,000km. We're self-catering campers so there's a fair amount of equipment to carry, which increases the need for good springs, and we'll probably put a 50 litre fuel can and a large water carrier in too. Of course if these springs improve the handling when unladen I won't complain, although BOB had fairly new looking KYB gas shockers on front and back when I bought it and the ride quality has been very good.

After a late Saturday night out I spent Sunday morning messing around taking measurements and fitting a set of the different springs... it was all a bit like a school experiment but with a hangover (i'm glad the car is parked underground out of the sun).
Here's the line-up of my 5 sets of springs to try out, with one of the originals that was on the car already shown on the left (sorry about the shadows)

Spring lineup
I selected the big fat short ones with the least coils but the thickest coil diameter to try first. Here's what one looks like compared to the original spring (black):

before v after


Once I'd fitted them I did some measurements to compare them. Then took the car for a bit of a drive. They're definitely an improvement - far firmer but not exactly uncomfortable. Speed bumps were good at speed. This table shows the effect these springs have had:
SPRINGFREE LENGTH# COILSRIDE HEIGHT (REAR) UNLADENRIDE HEIGHT LADEN (95KG)SPRING MOVEMENT (AS % OF UNLADEN HEIGHT)RIDE HEIGHT FRONT

original

328mm

12

595mm

565mm

5%

640mm

#1

300mm

9

608mm

584mm

3.9%

636mm

#2

301mm

13

-

-

-

-

#3

304mm

9

-

-

-

-

#4

312mm

12

-

-

-

-

#5

315mm

10

-

-

-

-


Unladen B4 change
RHul b4zoom
Unladen with Spring #1
RHul afterzoom

B4 change + me (95kg)

RHl b4zoom

Spring #1 + me
RHl afterzoom
So that's the first set of springs tried out. The question now, though is whether I should try any of the other springs out. I'm not entirely sure how to make a judgment on what the qualities of the others are likely to be based on their characteristics... anyone else know?

2 comments:

VitesseEFi said...

You're being very methodical about this Graham!

In general the fewer coils on the spring, the higher it's rate and thicker material will tend to indicate this too. So you've probably selected the highest rate ones akready by the sound of it.

Rather that fit them all on the car (sounds too much like work too me!) you could just work out their rate by piling weights on top and seeing how much it takes to shorten by 1".

As you've now go two 'on the car examples for comparison this ought to narrow things down a bit.

Good luck

Nick

Graham Reeks said...

Yes Nick, I am/was being very methodical, wasn't I? ... unusual for me :-)

I think you're right about the 1st choice of spring being the firmest, which is why I tried them first - and you're definitely right about it being too much work trying them all out!!! So i'm settling with the ones I've put on.

We now have to test the car out with some heavy loads...

Graham