What makes high spring rates kill shocks? I would think it would help it, since it keeps it from moving as much... less movement = less wear?

 

Less travel = focusing the wear and friction-generated heat across a smaller length of the travel, would be my guess. Same mechanical energy absorbed within smaller space/shorter travel time = higher temperatures in smaller volume.

Just a guess, though.

 

Yeah, I have been searching google and all I can find is "Don't do it with stock shocks because we said so" stuff.

Although I did see a few places saying something along the lines of Koni's are not position sensitive, and they will work in any area of their stroke as long as it doesn't bottom out.

 

shocks slow down the spring.. if the spring is a higher spring rate then the shocks are less effective and get worn down?? that's my guess..

 

I just made a thread in the suspension section of the forums. Don't know if the traffic there is high enough though.

 

The shocks are valved to control a certain spring rate and a certain unsprung weight(suspension etc.) If you run a higher rate than stock with a stock shock the valve will be overloaded and not do its job. Now I don't know if its will actually wear the shock faster or blow the valve to a point that soime of the shims get bent but it won't control the spring.

 

jgrewe is 100% correct it will blow the internals of a shock apart making it pretty much useless.
if you are upgrading spring do the shocks at the same time. if you don't have the money for both themn buy one then the other and install them togther.

 

Cool. That is what I was getting the gist of, but since I have coilovers and tokico blues, should I be in the clear?

I might give a call to tokico and find out the valve specs.

 

What are your spring rates? Is this for track use?

 

you said 425s right? i'm pretty sure the blues are like a 4 on the stock illuminas so they might not be enough..

 

Over 400 lbs on the front? The tokicos won't last long with rates that high, not even rx7 illuminas . `

 

the mr2 illuminas might work for you...

ask billy.. he should know best

 

From my understanding its the rebound, stiffer the spring, the higher the pressure/force on the shock to return to its original shape after compressing.

 

425/200s are what I am running right now.

 

When I bought my RX7 it had 450F and 300R springs with Illuminas on it. The struts/shocks worked pretty good but had to be run at setting 5 all of the time. The owner that put this together talked to Jim Susko about the setup and he said that those rates were about all that the Illuminas could handle. The shocks eventually wore out but I am not sure if this had anything to do with the spring rates or just 5 years of racing abuse.

I have since gone to 400F and 250R springs and run Koni struts and Pro Shocks on the rear. These spring rates match my driving style better and the struts/shocks work better for club racing as I have more of an adjustability range with the Koni's. The Pro Shocks are not adjustable but are a split valve shock - medium stiff on rebound/soft on compression.

My feeling is that what you are doing should be managable for Illuminas. The biggest thing to watch for is that you don't bottom the stuts out. That will do them in for sure.

On a Solo II Mustang I used to have I ran stock struts/shocks with really stiff springs. Nothing dramatic occured - the car just wasn't very fast and bounced around allot. Stock/HD shocks cannot damp stiff springs effectively. Whether or not they eventually fail is not relavent....they will be so bad you won't wait to find out.

 

Scott, did your car have the rx7 illuminas or the mr2 versions?

 

I feel that 350#/375# is the limit for Illuminas. I normally suggest the MR2 inserts for 375#/400#. Anything more than that and you need to mod the struts for race inserts.

The shocks will obviously work with those springs rates - just not for long. You are basically over working the valve system. When something is overworked it is not efficient.

-billy

 

Most likely ones for an RX7. What kind of racing are you doing and are you locked into the spring rates you have?

 

this is what i remember from the PRO7 days too

 

Simple answer is this. The spring moves vertical energy from the road hitting the tire. and since energy can not be created or distroied without a shock after taking a bump the spring in theory would never stop moving. (that is why cars with blown shocks bounce forever after hitting a bump.) What the shock does is it converts the springs mechanical energy and converts it into heat. the higher the spring rate the more energy is present in a smaller area of the spring after hitting a bump and the less transfered through the body. therefore there is more heat to be disapated by the shock. A shock is valved to disapate a certin amount of heat controled through is valving and weather its gas or liquid. That's why you hear about gas/liquid shocks boiling or foaming over they're not desiged to dtransfer teh mechanical energy into heat fast enough. When shocks are not valved to dampen the spring it will wear out faster due to the degradation fo gas or fluid that is in the shock. Or you could have a valve in the shock break from bottoming out. the late great sport compact car had an amazing 6 or 8 part series on suspensions that expalined it all.

 

So it looks like I should either move to MR2 shocks and 400 springs, or just go to 350 springs and stick with the blues.

 

mazdacomp sells bilsteins. i found a koni yellow insert too, but its $$$

there are plenty of options besides tokico

 

I am not a part of MazdaComp though I need to get to some autocrosses or something if they have any around here.

And Bilsteins are usually $$$$$$$

 

from mazda: 0000-04-7217-BL

CARTRIDGE, STRUT (FRT)

Nice alternative to Tokico Illuminas. Can hold up to higher spring rates than the Tokicos. Bilstein high pressure gas montube shock absorber. The superior damping ability helps improve handling and stability without sacrificing ride comfort. Instantaneously self-adjusting for changing road surfaces and their performance does not decline from age, use or heat. Heavy Duty setting fits all models. Requires ring nuts, 0000-04-7227-BL x2. #P30-0104

Notes: P30-0104

http://www.allshocks.com/bilstein/ht...RX-7&year=1979

$140 is more than the tokico, but its not $$$$$$$$

B4-B30-U226B1 is the bilstein ring nut

 

I got the mr2 illuminas with 350 springs up front. I talked to Billy and he said 275 up front or 300 max if I stayed with the blues. You need illuminas either way..