This statement doesn't make sense to me. You adjust the perch which shortens/lengthens the spring, hence increasing/decreasing the preload. This is one of the frequently touted drawbacks of the KW V3s, but I think it's overstated since there is a small helper spring which is actually taking up almost all of the preload, so the "preload" effect becomes inconsequential.

 

Yes.

 

Yes

 

I do not remember the exact numbers and i cannot just check because the difference was really small and the only 100% flat area i can trust is the alignment shop's ramp. Keep in mind that the amount of gas, spare wheel and exhaust type change things a lot.

BillJ. Maybe the term preload was incorrect. I am referring to the situation where the spring is "concentrated" to the top of the shock rather than the whole body of the shock. I have set the ride height to the minimum solely for that reason. Should i move it to the upper range in order to have more travel and not mess the RCs too much?

 

I was thinking the same... I did not know about the exact job of the helper spring though. This is another reason to raise the height from the lowest recommended setting.

 

The spring perch location does not shorten or lengthen the spring. The spring perch location will however affect how much the helper spring is compressed (preloading the helper spring -if you will) but it is not preloading the main spring and has no effect on handling.

IF you raise the spring perch location beyond KW's max setting, then you can completely compress the helper spring and start to compress (preload) the main spring. Since you are not adjusting the ride height to this level, you are not prealoading the spring.

KWs are designed with far more droop travel than most coilovers out there which have almost no droop travel. In order to have this droop travel and not have the spring loose and mis-align on the spring perches when full droop (jacking up the car or going over a big bump that launches the car), the helper spring maintains steady pressure on the main spring to keep everything aligned under all circumstances. Most racecars use shorter springs (which are lighter btw) and helper springs to keep the main spring aligned under full droop travel.

I would hardly call this a 'frequently touted drawback of the KW V3'. The V3 is designed to work in a certain operating range (which KW states in the owners manual) that will have sufficient compression and droop travel. Most people don't even know what preloading the spring even does (affects initial roll resistance which is so minute most people wont feel it anyway). Preloading the spring in any asian coilover greatly reduces droop travel. Cars that play with preloading the spring and have little to no droop travel are formula cars and prototype cars, with very little travel, perfect suspension geometry to work in that short range of travel, etc... For production cars and especially for street cars, you don't want this little of droop travel.

More droop travel will prevent the car from 'skipping' across bumps in the road, and especially after hitting apex curbing on the track. More droop travel will make the car feel much more planted and confidence inspiring, while keeping the tires on the ground to generate more grip. Too little droop travel (by prealoading the spring too much) can and will reduce overall grip if the droop limit is reached from bodyroll alone.

The whole threaded body with independent spring perch height and ride height (via lower body perch) is a great way for the manufacturers to use the same size shock internals for many applications as well as a great marketing gimmick to people who don't fully understand the so-called "benefits". Look at any production-based racecar out there; you wont see the asian coilover with "preload" design but rather a single spring perch, main spring, more often than not a helper spring, and more droop travel than most the street cars with 'coilovers' out there.


Billy
FX Motorsports Development
FXMDBilly@gmail.com

 

Thanks for the informative post, Billy. I want iterate that I wasn't trying to say I also think the perch design is a compromise (I think the helper spring almost entirely eliminates this problem).

However, if I can be pedantic here for a bit, there is no way adjusting the perch doesn't shorten the main spring to some degree. I think Robi said earlier that the helper spring is 70 lb/in. If we compress that spring by one inch to raise the ride height by one inch, we have applied 70 lbs of force to that spring, which then must be transmitted to the main spring. Fortunately, 70 lbs of force only compresses the main spring only about 1/8th of an inch (70 lbs force on a 515 lb/in spring = .14 inches of compression). Like I said, we're not talking about a lot, but we are still definitely preloading the main spring.

 

I am learning from this discussion....Thanks.

Check out Rob's website on how he corner balance his S2k:
http://www.robrobinette.com/corner_weight.htm

Stock S2k cross weight is such that left front < right front, right rear < left rear so the car has slightly more grip in left turn than right turn.
So we should expect to raise the perch on rear right and left front to balance it.

 

The whole point is everyone is concerned about and talk about preloading the spring when the primary thing you are doing is simply setting the ride height.

If you want to look into it that much detail, yes if you compress a 70lb/in helper spring (they vary depending on the model/application) one inch, then yes you have 70lbs of force compressing a 456-571 (V3-CS) spring -which is minimal.

Just talk about ride height and not spring 'preload'.

 

Keep in mind that the corner weight for each car is different, mostly depending on the ride height at each corner in relation to each other.