BC coilovers with custom spring rates

kazama · Postby **kazama** » Thu Jan 30, 2014 1:18 pm

hey guys,

has anyone done this? Im fairly set on running 6kg front springs and 4kg rear but i cant seem to find anything off the shelf that fits the bill.

cheers

YanMa YatTai · Postby **YanMa YatTai** » Thu Jan 30, 2014 1:34 pm

Apparently you can specify when you order. Don't know if all resellers will do this though.

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plohl · Postby **plohl** » Thu Jan 30, 2014 1:44 pm

Why those spring rates?

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kazama · Postby **kazama** » Thu Jan 30, 2014 2:32 pm

YanMa YatTai wrote:Apparently you can specify when you order. Don't know if all resellers will do this though.

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hmm yeah ive heard the same. i was just curious if anyone on the forum had first hand experience.

plohl wrote:Why those spring rates?

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i want to run stock size sway bars (albeit with poly bushes) and from my research 6/4 would be a good spring rate to run with my tyre size/compound of choice and driving habits

plohl · Postby **plohl** » Thu Jan 30, 2014 3:27 pm

Right. Just call Just Jap or whoever sells the BC's and ask them. It'll give you the quickest answer. I know zoomzoom got custom spring rates when he ordered his, not sure where he got them from.

manga_blue · Postby **manga_blue** » Thu Jan 30, 2014 3:40 pm

6/4 is one of the few workable combinations I haven't tried. I had 5/4 with Superpro poly bushes for a while and that was a really good compromise between country tourer and track machine, except that it was a little soft at the front and I had to fit a size larger front bar. The car was very competitive like that, as well as taking me comfortably on a few 1,000km runs on the B roads between Melbourne and Central NSW. With 6 Kg instead of 5 at the front it should be just right on stock sways.

Nevyn72 · Postby **Nevyn72** » Thu Jan 30, 2014 3:44 pm

For comparison, does anyone know what the stock spring rates are on a NB SE?
This had the sportiest suspension of any of the factory models.....

manga_blue · Postby **manga_blue** » Thu Jan 30, 2014 4:34 pm

The US '03 Mazdaspeed had 3.8/2.8. Maybe our version of it had the same springs?

edit: stock NB was 2.9/2.1

Lokiel · Postby **Lokiel** » Thu Jan 30, 2014 9:23 pm

Nevyn72 wrote:For comparison, does anyone know what the stock spring rates are on a NB SE?
This had the sportiest suspension of any of the factory models.....

From http://www.mazda-speed.com/forum2/index.php/topic,14604.0.html:
Front: 215 lb/in. (3.84 kgf/mm)
Rear: 157 lb/in. (2.80 kgf/mm)

project.r.racing · Postby **project.r.racing** » Thu Jan 30, 2014 10:31 pm

kazama wrote:i want to run stock size sway bars (albeit with poly bushes) and from my research 6/4 would be a good spring rate to run with my tyre size/compound of choice and driving habits

just get king springs if you aint chasing performance upgrades.

as for coilovers, all retailers/suppliers/manufacturers allow a 1kg increase/decrease. more than this required different shocks and add costs to the coilovers.

kazama · Postby **kazama** » Fri Jan 31, 2014 8:10 pm

manga_blue wrote:6/4 is one of the few workable combinations I haven't tried. I had 5/4 with Superpro poly bushes for a while and that was a really good compromise between country tourer and track machine, except that it was a little soft at the front and I had to fit a size larger front bar. The car was very competitive like that, as well as taking me comfortably on a few 1,000km runs on the B roads between Melbourne and Central NSW. With 6 Kg instead of 5 at the front it should be just right on stock sways.

excellent, thats what i like to hear

plohl wrote:Right. Just call Just Jap or whoever sells the BC's and ask them. It'll give you the quickest answer. I know zoomzoom got custom spring rates when he ordered his, not sure where he got them from.

yeah that would probably be the best bet. i might PM zoomzoom and pester him a little

project.r.racing wrote:
kazama wrote:i want to run stock size sway bars (albeit with poly bushes) and from my research 6/4 would be a good spring rate to run with my tyre size/compound of choice and driving habits
just get king springs if you aint chasing performance upgrades.

as for coilovers, all retailers/suppliers/manufacturers allow a 1kg increase/decrease. more than this required different shocks and add costs to the coilovers.

they certainly are for performance. stiff springs dont work with narrow-ish street tyres. i actually dont mind kings but ill need to run larger sway bars and i personally prefer small bars with (relatively) stiffer springs

project.r.racing · Postby **project.r.racing** » Fri Jan 31, 2014 10:26 pm

kazama wrote:they certainly are for performance. stiff springs dont work with narrow-ish street tyres. i actually dont mind kings but ill need to run larger sway bars and i personally prefer small bars with (relatively) stiffer springs

none of that makes sense in real world applications.

Postby **NitroDann** » Fri Jan 31, 2014 10:29 pm

This.

kazama · Postby **kazama** » Sat Feb 01, 2014 12:23 pm

project.r.racing wrote:
kazama wrote:they certainly are for performance. stiff springs dont work with narrow-ish street tyres. i actually dont mind kings but ill need to run larger sway bars and i personally prefer small bars with (relatively) stiffer springs

none of that makes sense in real world applications.

NitroDann wrote:This.

care to elaborate?

ricky-pinky · Postby **ricky-pinky** » Tue Feb 04, 2014 12:50 pm

If it is not too late to comment, I would run a 6kg front and a 5kg rear combination .
4kg rears will be too soft with the BC's short rear damper stroke and you will need a lot of rear spring preload to keep the back of the car off the bump stops.
And in my opinion, a 6/5 combination gives a better combination of front to rear wheel rates.