Tender springs to help with droop on heavy spring rates
Aug 24, 2011, 09:53 AM
#31
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Dallas,
He hasn't been doing the track work this year - I assume it is because of the new job with more hours, and getting married earlier in the summer, compounded by the fact that his stock short block appears to be on its last legs. He's in the "build new engine" mode and if the car's not taken apart yet it certainly will be soon.
I don't know how much you understand about damper valving and damper dyno plots. It is critical for you to understand the difference between high speed valving and low speed valving. It is also critical to find out exactly how your dampers' adjustment knobs affect the valving - in MANY cases with 1 or 2 way adjustable dampers, the knobs only affect the "knee" from low speed to high speed. In this situation, if the damper wasn't built with enough low speed damping to support high spring rates and roll stiffness, changing the knob setting will make no change or very small changes to the problem. The technically easiest solution is a set of quality triple adjustables. With triple adjustables you get an adjustment over low speed rebound. They are hard to pay for though.
He hasn't been doing the track work this year - I assume it is because of the new job with more hours, and getting married earlier in the summer, compounded by the fact that his stock short block appears to be on its last legs. He's in the "build new engine" mode and if the car's not taken apart yet it certainly will be soon.
I don't know how much you understand about damper valving and damper dyno plots. It is critical for you to understand the difference between high speed valving and low speed valving. It is also critical to find out exactly how your dampers' adjustment knobs affect the valving - in MANY cases with 1 or 2 way adjustable dampers, the knobs only affect the "knee" from low speed to high speed. In this situation, if the damper wasn't built with enough low speed damping to support high spring rates and roll stiffness, changing the knob setting will make no change or very small changes to the problem. The technically easiest solution is a set of quality triple adjustables. With triple adjustables you get an adjustment over low speed rebound. They are hard to pay for though.
Aug 24, 2011, 10:03 AM
#32
Dallas,
He hasn't been doing the track work this year - I assume it is because of the new job with more hours, and getting married earlier in the summer, compounded by the fact that his stock short block appears to be on its last legs. He's in the "build new engine" mode and if the car's not taken apart yet it certainly will be soon.
I don't know how much you understand about damper valving and damper dyno plots. It is critical for you to understand the difference between high speed valving and low speed valving. It is also critical to find out exactly how your dampers' adjustment knobs affect the valving - in MANY cases with 1 or 2 way adjustable dampers, the knobs only affect the "knee" from low speed to high speed. In this situation, if the damper wasn't built with enough low speed damping to support high spring rates and roll stiffness, changing the knob setting will make no change or very small changes to the problem. The technically easiest solution is a set of quality triple adjustables. With triple adjustables you get an adjustment over low speed rebound. They are hard to pay for though.
He hasn't been doing the track work this year - I assume it is because of the new job with more hours, and getting married earlier in the summer, compounded by the fact that his stock short block appears to be on its last legs. He's in the "build new engine" mode and if the car's not taken apart yet it certainly will be soon.
I don't know how much you understand about damper valving and damper dyno plots. It is critical for you to understand the difference between high speed valving and low speed valving. It is also critical to find out exactly how your dampers' adjustment knobs affect the valving - in MANY cases with 1 or 2 way adjustable dampers, the knobs only affect the "knee" from low speed to high speed. In this situation, if the damper wasn't built with enough low speed damping to support high spring rates and roll stiffness, changing the knob setting will make no change or very small changes to the problem. The technically easiest solution is a set of quality triple adjustables. With triple adjustables you get an adjustment over low speed rebound. They are hard to pay for though.
This winter I'll probably be working with the guy who makes these shocks out of vancouver to revalve for my higher than normal rates and get some better information on exactly what the adjusters adjust.
According to Andy at AMR these should be low speed only rebound adjustable. He has a dyno though and Ill get some real numbers as soon as the season ends.
Aug 24, 2011, 10:26 AM
#34
Not yet, the guy who builds them is local though so as soon as my last event is done these will come off and my wonderful Bilstein/GTworx setup will go back on. Then Ill take them to him to have them gone through, revalved, and dyno'd for the 700/900 setup.
I have 4 events left with the last one in early october, so only about a month and a half till I can get them all tested.
I have 4 events left with the last one in early october, so only about a month and a half till I can get them all tested.
Aug 25, 2011, 07:49 AM
#35
Took some measurements yesterday.
The shock has 5.0625" of total travel. The current bump stop is 1.5" long and the spring coil binds at 3.8" of compression.
With just the main spring I compress 1.1875" at static load. To get to 2" of bump and 2" of rebound I would have to lower the lower mount by 0.8125" and conversely take up that much free slack with a tender spring. The swift tender springs have 1.65" of compression.
Given these values, Im going to crunch some numbers to get a effective spring plot.
One thing to note though, if I do this I will have to buy a 7" spring. The preload perch would be too close to the upper control arm if I tried to fit a tender with the 8" spring. I'll lose some travel before coil bind but I check the numbers first to make sure that doesnt happen.
The shock has 5.0625" of total travel. The current bump stop is 1.5" long and the spring coil binds at 3.8" of compression.
With just the main spring I compress 1.1875" at static load. To get to 2" of bump and 2" of rebound I would have to lower the lower mount by 0.8125" and conversely take up that much free slack with a tender spring. The swift tender springs have 1.65" of compression.
Given these values, Im going to crunch some numbers to get a effective spring plot.
One thing to note though, if I do this I will have to buy a 7" spring. The preload perch would be too close to the upper control arm if I tried to fit a tender with the 8" spring. I'll lose some travel before coil bind but I check the numbers first to make sure that doesnt happen.
Sep 21, 2011, 06:51 AM
#38
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Hi guys, could someone elaborate on the effect of the dual spring setup with the tender spring? Is the transition from the tender spring to main spring smooth? Or is the change more or less a sudden kick? For example you are taking a pretty hard corner, so lets say the initial spring rate is fairly soft/comfortable (say, around 250), and the main spring rate is 600, tender is 400, so does it gradually increase from 250 to 600 and then stays at 600? or is the transition going from 250 to 400, then BAM switch over to 600?
Last edited by codenamezero; Sep 21, 2011 at 06:58 AM.
Sep 21, 2011, 06:29 PM
#39
In that case, the rate would be 176 till tender is compressed then 600 after. But the load at transition doesnt change, only the rate of change changes.
But on an Evo a 250lb tender spring will be completely compressed at static ride height. So the spring only comes into effect when the car unloads, like the inside tires during turning.
But on an Evo a 250lb tender spring will be completely compressed at static ride height. So the spring only comes into effect when the car unloads, like the inside tires during turning.
Sep 21, 2011, 06:39 PM
#40
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When i say 250, i mean the initial spring rate is 250.
How do you calculate/know that the tender would be completely compressed? Do you take the corner rate of the car?
Also I've seen people having some pretty high tender spring rate, say, 800 tender, 500 main, does that mean the tender would never compress before the main does...? I'm lost.
How do you calculate/know that the tender would be completely compressed? Do you take the corner rate of the car?
Also I've seen people having some pretty high tender spring rate, say, 800 tender, 500 main, does that mean the tender would never compress before the main does...? I'm lost.
Sep 22, 2011, 08:26 AM
#42
If you know your corner weights you can calculate the load at the spring. (CW-USW)/(MR^2). Knowing the load at the spring, its pretty easy to find the wheel load to fully compress a spring given the data for an eibach spring. I cant really find any hyperco springs but I'm also not worried about absolute accuracy with the tenders.
I plotted out all my options for tender springs in excel to get an idea of the travel based on load and know what preloads I would need. Turns out for what I'm doing stiffer isn't necessarily better. Id prefer to keep some numbers to myself, but a lower spring rate with more preload will give the same or more force at max droop and fully compress sooner.
The large rate springs I think are used for cars the pre-compress the tender only. If you do it right then the tender only comes into play under heavy bumps reducing rate at high travel so the car is upset less. It doesn't have any effect in this situation at full droop or roll in corners.
I plotted out all my options for tender springs in excel to get an idea of the travel based on load and know what preloads I would need. Turns out for what I'm doing stiffer isn't necessarily better. Id prefer to keep some numbers to myself, but a lower spring rate with more preload will give the same or more force at max droop and fully compress sooner.
The large rate springs I think are used for cars the pre-compress the tender only. If you do it right then the tender only comes into play under heavy bumps reducing rate at high travel so the car is upset less. It doesn't have any effect in this situation at full droop or roll in corners.
Feb 23, 2016, 07:16 AM
#43
Evolved Member
Can i plz revive this? I'd like to see if you ended up using tender springs or normal helpers.
I just purchased 2 way remote MCS coils on 800/800 in/lb springs and 3.5 kg/mm swift tenders on all 4 corners. They will be fully compressed at static ride height, but i am really curious to see if anyone has experience running stiff tenders. I hope i didn't make a mistake :0
I just purchased 2 way remote MCS coils on 800/800 in/lb springs and 3.5 kg/mm swift tenders on all 4 corners. They will be fully compressed at static ride height, but i am really curious to see if anyone has experience running stiff tenders. I hope i didn't make a mistake :0
Feb 23, 2016, 12:45 PM
#44
I use med-soft tenders with a lot of preload in the rear. That gave a bit extra travel to rebound over bumps without fully extending the shocks and in my case is more of a comfort thing. If nothing else, it removes the jarring effect of hitting the drop limit of both wheels.
Up front I use 6" springs and no helper/tender to keep the perch above the top of the tire for clearance.
Up front I use 6" springs and no helper/tender to keep the perch above the top of the tire for clearance.
Feb 24, 2016, 05:19 AM
#45
Evolved Member
i was wrong, i just looked it up. The tenders i purchased are 6 kg/mm. They have a 1.6 inch range of extension/compression. I got them specifically for droop. My springs are 7 inch hypercos at 800in/lb on all 4 corners. Do you think the tenders up front will be unecessary? Do you ever run out of droop up front?
With my 700 lb rear corner weights, i'll have about .2 inches of compression into the rear main spring after compressing the tenders at static ride height. Up front i'll end up having .6 inches of compression into the main spring.
how much total droop does your tenders provide out back?
With my 700 lb rear corner weights, i'll have about .2 inches of compression into the rear main spring after compressing the tenders at static ride height. Up front i'll end up having .6 inches of compression into the main spring.
how much total droop does your tenders provide out back?
