Adjusting ride height with coilovers (preloads vs shock length)

[aus jd 2703]

ok I bought a pair of bc br coilovers for my gt four and they have been ok (not as smooth as a friends teins even though bc's are softer spring rate).
recently ive been doing trackdays and looking to refine my handling so was going to lower m front to get more turn in etc.
but then I read MCA's article on setting shock length to set max compression (bumpstops) then using spring preload to set ride height.
this article made sense to me given springs are designed to be linear (xkg/mm) adding preload to achieve ride height shouldn't affect spring rate.
so why do bc suggest using shock length? is there any advantage to using shock length over preload? anyone have any feed back on the methods?

if it matters the car is daily driven and tracked about once a month, its a gt four so all grip no drifting or off road.

[eightsixboy]

The only other way to adjust height would be to adjust were the spring sits, alot of the cheaper tein's have this. Base adjustment is best as the spring is captive 100% of the time and you can adjust spring preload.

Adjusting the base of the BC's doesnt change how far the spring is compressing, I think you will find that on most coilovers with correct preload on the spring you wont even get close to hitting the bumptops.

I would be investing in better front/rear diffs and swaybars/setup if your chasing better turn in, any awd especially the GT4 will suffer with understeer.

[aus jd 2703]

no front diff options exist under $5k sway bars are already done.
this to me is set up.
your answer isn't quite clear to me, are you saying adjust with preload or with "base height"?
also adjust base height effects bump stops and droop, I believed this was undesirable as bump stops are ideally set to prevent tyre to guard contact?

[Ken_T]

Try preloading your springs 5 or 6mm. It loads up and removes any irregularity/non-linearity in the spring.

Set the ride height by the base height. Put a ziptie around the shock shaft and to a normal hard lap. Avoid hitting any big bumps. Come back in and check the ziptie location. If it's real close to the bump stop (like a cm), that's good. If it's crashing into the bump stops, add more preload. If it's more than 15mm away, remove some preload.

What you want to do is come close to the bump stop in normal hard driving without hitting it. That way you have the most amount of droop available and less likely to lift a wheel. Hitting the bump stop when you hit a big bump is fine, having progressing bumps stops is best.

Remove the aftermarket front ARB and fit the stock one back if you want to deal with understeer.

[eightsixboy]

no front diff options exist under $5k sway bars are already done.
this to me is set up.
your answer isn't quite clear to me, are you saying adjust with preload or with "base height"?
also adjust base height effects bump stops and droop, I believed this was undesirable as bump stops are ideally set to prevent tyre to guard contact?

What I'm saying is the base adjustment on the BC's is better then adjusting via lowering the spring like on cheaper coilovers, really on any coilover with a fairly stiff spring you shouldn't be getting anywhere near the bumpstops or full shock travel.

If you adjust the coilover base to adjust height, the spring/shock doesn't move anymore/less, not sure why you think this adjusts how far the shock travels. The only way the shock would travel further and hit the bump stops is if the spring had no/less preload on it or if you had lowered the height via the spring, which is not what you want to do.

On all the coilovers I have had I have always had enough preload on the spring so its captive and adjusted the height by the base adjustment, this way shock travel isnt affected. There really isnt any reason to adjust spring preload to adjust height as thats what the base adjustment is for.

To answer your main question, if you want better turn in I don't think playing with shock travel/spring preload is going to help much if at all, you would be better off trying different spring rates or different damper settings.