rear springs

[jeff.fenton]

I bought on EBay a pair of "Excel rear springs", made by Suplex part no. 16017. There were no spec's listed , and the seller didn't answer my question so presumably dosen't know. The only on line supplier of Suplex I could find, has no reference for this part number. They seem to be of German manufacture, has anyone any information, or could one of our German members access the Suplex catalogue direct please? My car has all new, adjustable shocks, and new Lotus front springs, the rear springs are original and presumably weakened, as the back end dips noticeably after bridges and humps. I don't want to fit the new ones and find they're way too hard for normal road use. Many thanks, Jeff.

[amarshall]

Were they listed as Lotus Excel or just Excel ? (If the latter, it may mean Hyundai...)

[jeff.fenton]

Hello Angus, they were listed as Lotus Excel SE rear springs. Jeff.

[Lotus-e-Clan]

You can work out the spring rate by taking key measurements off your spring.

You want:

wire diameter
Spring Outside diameter
Spring free length
the number of coils

You count the number of coils by starting at the bottom where the wire ends. Then count whole coils upwards - and when you get the the last one, IF the wire end is directly above the lower wire end, its counted as a whole coil. IF it's 180 degrees further around it's a half coil, 90 degrees around, it's a 1/4 coil etc.

You then put the numbers into an online spring rate calculator (google one) to find the spring rate in Ibs/ inch deflection. Then compare to known SE spec.

I can't find the calculator I downloaded years ago - I have the executable - but can't upload it to this site AFAIK.

CLICK here is an online spring rate calculator. Not quite as good as the one I have but it will do for now...

NB, OMIT the compressed length - it still works

[jeff.fenton]

Thanks for that, free length 12.75", coils 10.5,(active coils 8.5?), wire size 0.6175"(assume disregard powder coat thickness?), mean diameter 3.75": if I'm doing this right it comes out at over 450 Lb/inch. I haven't got the Lotus spec' to hand, but think it was in the mid 200's. Any views? Thanks, Jeff.

[richardw]

Hi Jeff,

I think that it is unlikely your springs have gone soft. If this were the case, the car would be sitting lower than normal as the weight of the car would compress the softened spring more than normal. Also, I did a test at Lotusbits a while ago on some rusty old Elite springs which, despite their age, were within a pound or two of the rating they were meant to have.

Adjusting the shock absorbers could help with the dipping you are experiencing - have you tried a stiffer setting?

ATB Richard

[don.hasi]

or could one of our German members access the Suplex catalogue direct please?

They have no online catalogue. The web page of them is rubbish... I have mailed them the question. Lets see, what they are saying.

Regards

[Hawaiis0]

Thanks for that, free length 12.75", coils 10.5,(active coils 8.5?), wire size 0.6175"(assume disregard powder coat thickness?), mean diameter 3.75": if I'm doing this right it comes out at over 450 Lb/inch. I haven't got the Lotus spec' to hand, but think it was in the mid 200's. Any views? Thanks, Jeff.

from memory the rate is 300/250

[Lotus-e-Clan]

Thanks for that, free length 12.75", coils 10.5,(active coils 8.5?), wire size 0.6175"(assume disregard powder coat thickness?), mean diameter 3.75": if I'm doing this right it comes out at over 450 Lb/inch. I haven't got the Lotus spec' to hand, but think it was in the mid 200's. Any views? Thanks, Jeff.

Just not sure about your OD measurement of 3.75 ...we need the extreme OD - not a mean OD?

So taking the OD of 4 inches (instead of 3.75) with 10.5 coils my calculator (with Chrome Van steel type coils selected) gives approx 515 LB/in. With 3.75 OD they are nearer 650 LB/in.

Either way, they sound like they are uprated compared to std.

Next thing to do is to measure your std springs and use the same calculator to get a relative view on how much they are uprated.

Are these front or rears?

[jeff.fenton]

Thank you all for your help and suggestions. I went over the measurements and calculations, seems the wire diameter has the largest influence on the result, measured at 15mm with anti-rust primer and powder coating, gives 390 lbs/inch. 14mm would give 290, and 13.5mm 250. Difficult to be exact, but removing a small area of coating back to metal seemed to be over .5mm thick, ie 1mm+ overall. This should bring the spring rate into an acceptable area, so I intend to fit them and hope, will report back. Jeff.