So I learned something rather important after 15 yrs tinkering with ITR suspension etc - suspension bump stops were carefully tuned by Honda as an integral part of the car's ride/handling/balance. They are not just for preventing metal/metal contact between shock and upper spring perch as the name implies. They are actually a spring used in parallel with the coil spring and have a rate that can be higher than the coil spring (actually progressive rate that increases strongly with wheel travel - talking >500 lb/in in front with rear roughly half the rate of front). Interestingly, this means the coil spring rates and changes thereto, have much less impact on balance than if the bump stops weren't being used in parallel. I find it interesting that I have never come across any information about this 'situation' in forums etc I only realized this after recently installing Ground Control coilovers and leaving off the shock dust shield, showing the very close proximity between bump stops and shock body with car on the ground.

Lesson here is that any change to ride height or suspension travel should also include careful resetting of the bump stop lengths as part of balance tuning. If you lower the shock body relative to the upper spring perch/bump stop (this happens when you lower the car from stock), you should trim the stop by the same amount to maintain same relationship between bump stop and top of shock body - both front and rear. If you trim material off the small end of bump stop, you are increasing the stiffness of the part. If you trim off the large end, you are not changing stiffness very much - as long as removing less than 1/2 of the height of the largest section.

Another thing to consider is that reducing clearance between shock body and bump stop (or even preloading bump stop) due to lowering car without trimming stops will result in harsher ride quality - especially if this is done in the rear...

 

yep. these cars don't have much free travel.

But lots of cars use bumpstops as springs. Probably almost all cars do.

Its pretty common tuning for oem and aftermarket. Aftermarket coilover companies and lowering spring companies do the same thing.

 

Thanks for this. Returning my DB8R suspension to stock so I am doing my research.

 

^^ You can get new OEM bumpstops cheaply.