Hi all, bit of a Friday afternoon question but I'm trying to get my head around something.
The situation is with my current coilover setup the spring (linear rate) isn't captive.
To fix this i'll be changing to a shorter stroke strut, which will make the spring captive as well as regain some suspension travel.
What I'm trying to understand is the optimum stroke location. It appears at ride height you want around 70/30 ratio? 70% compression and 30% droop of the total travel.
Assuming thats correct... What I can't get my head around is if you have the spring captive which means the shock must be fully extended and with some pressure from the spring on it.
The ratio of compression/droop will only be dictated by the amount the spring compresses from the weight of the car @ ride height?
If you have a stiff linear spring, the spring might not compress hardly at all, and you would not end up with the optimum stroke location? Like instead of 70/30 might end up with 90/10 for example.
Your train of thought is similar to mine. I haven't yet faced problems of this sort but I have spend time thinking and studying this. Anyway, there are three ways of playing and fixing this, that I know of. I'm ruling softer springs out as a fourth option.
In order of cheapest and easiest:
1. Spacers. If you have short stroke with spacer. Get O-spacer and regular bottom spacer. Example if your spring sets 20mm off the upper spring seat (20mm from captive). Get 20mm bottom spacer in the bottom of strut and 20mm O-spacer top of the strut. This will move the cartridge 20mm lower. You wont get 70/30 ratio anymore but 20mm in the most cases isn't nothing. Make sure that there is enough rebound left.
2. Helper spring. Easy and best but illegal(in Finland). Progressive springs kinda belongs in this category.
3: Height adjustable strut-tops. These have same affect as the spacer-trick. Basically these reduces rebound but these have more adjustment to play. Think about how easy it would be to make things match.
As you can see option 2 is the best route if you have serious dilemma with un-captive springs. 70/30 ratio isn't always valid depending on shock and its original application. For example Konis shouldn't be too overparticular about 70/30 ratio thing.
Do you think that you will have captive (captivetaty/captivitation OR woteve) problems with 5.1kg/mm(?) springs and short stroke setup. I mean, I have 4.0kg/mm springs and short stroke setup with 40mm bottom spacer and my springs are 30-40mm captive.
Just remember that when you haven't enough compression left - you might break your shocks but when you haven't enough rebound left you might break your whole car.
I hope this gives you some thoughts and feel free to correct me.
And once again sorry my bad English.
Fri, 05 March 2004 03:52
