These have probably been fitted to many 740s but no one seems to have written a review…Welcome to the Internet's first English review of BC Racing coilovers for the 740!
Why coilovers? Plenty of info out there but in short:
Height adjustable
Springs and shocks can be matched as well as shock body-to-spring height and travel
Tuning to get the most of your tyres
Surprisingly there are quite a few options out there. The cheapest by far was BC coilovers which are fairly easy to fit. The other options were:
Local:
- GAZ - Ash is the man to speak with
- HSD DIY sleeve kits - similar to Kaplhenke but cheaper and local. See Otomoto in Sydney.
- MCA - If I was living in QLD…
International:
- Kaplhenke (US). Few options varying in custom work but all require shock inserts.
- Ceika (warehouse somewhere in Asia?) - I like to call these guys upgraded BCs as they also have a huge application list and possibly better quality shocks. Came close to buying them for my last car. Would love to try these sometime in the future. They also make big brake kits. Decently priced.
- Retroturbo (UK) - must be made of gold…
Handling
With help from a very knowledgeable and experienced friend plus a bit of reading on motion ratios (zzz...) I decided to choose 10kg for the front and 7kg in the rear to suit my purpose of gracefully going sideways. The rears were a bit too stiff so I ditched the rear sway bar. The front however is superb. Gone are the days of sailing in the open waters betting on all hopes that the seas were calm and serene. Strap yourselves in girls this is one roller coaster ride you don't want to eject from. The stock 740 is desirably neutral and this setup has retained it without all the body roll. Flick the wheel and she instantly reacts. The grip levels are actually amazing IMO. I don't have decent tyres but with 235 front and 205 rear it is more than you need for a very spirited run up the hills. I also have a welded diff which alters the handling significantly.
Ride quality
As expected ride quality took a pretty big toll. Most of it depends on the rear spring rate and quality of the shocks. I have tuned my shocks to match the springs which helped a lot but you get what you pay for. I think something like 6 or 5kg rear would probably be better for me. I can feel all the little bumps on the road but there is still a bit of compliance lol. There has been BC rebuilders in Australia for sometime now which can help with this.
Conclusion
Overall, I'm quite happy with these budget coilovers for my somewhat budget runabout. I would probably go even stiffer at the front if I had to order them again maybe 11 or 12kg which would make it flick faster for feint entry style dori. For the occasional spirited driver a spring and shock combo is probably adequate and the only other reason to get coilovers besides handling is looks which it easily satisfies. Here's how she currently sits:
Front height is 64.3 mm and rear is 61.6 mm. Measured from the fender lip intersecting the centre of wheel to the ground. Can someone do me a small favour to compare the stock height? I was lazy and forgot.
If enough interest I could write up an short "fitting instructions" as the box never came with one but it's fairly straight forward. In a sentence, you cut 50mm short of the spindle, slide in the BC shock body and weld.
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October update: (nothing new, just consolidated development since August)
TLDR: Don't get BCs as rear spring are V-barrel type and 6kg is the lowest rate.
I've been in contact with BC racing via Just Jap trying to get rear springs with a much lower rate than 7kg. As I mentioned in the initial review, the rear is very stiff. I didn't take into consideration the motion ratio for the rear springs. DOH!
To get the actual spring rates, you get the motion ratio, square root it then multiply by the spring's rate. So for my 740 with 7 kg springs it would be:
1.22^2 x 7 = 10kg/mm - whoa!! No wonder it's crazy stiff. The car is very twitchy as well and tends to snap when you get it sliding at higher speeds. I took the MR number from turbobricks as my measurements were way off...
The problem now is BC racing can't do rates lower than 6kg for the rear. This is based on their in house testing. In house must be an ice skating area.
Second problem - the rear springs are v-barrel type so I have to get something made up or swap out my rear perch for some that will accept a 5 inch OD spring. Volvo live axle rear takes 5" OD on the rear trailing arm and I've been told 5" OD are a standard although I haven't seen many examples. I'm in the process of modifying my existing perch from BC to accept 5" springs.
Basically the rear BC setup is useless.
Conclusion:
If I had known about these two issues I wouldn't have bought them. The fronts are good so if you can get them separately you could put together a nice budget setup. I'm a little disappointed about the spring selection but they are a cheap kit and I should have done my homework with the rear motion ratio. At least I have the rear adjustable shocks though!