flatlander937
Member
- :
- '11 Mazda2 Sport
Hey Zach I double checked the measurements of the shock body stock vs my Koni housing, stock is 13" for the body and my housing is exactly 12". There is roughly 4.5" showing above the top of the tire for stock, so I'll potentially have maybe 3" of usable adjustment(some taken up by the adjuster ring itself). Due to the shorter housing I probably will not be sinking it downwards as it won't gain me anything, it will be mostly all uptravel anyway(which is fine and will be good for ride quality).
In other news: I got my 7in/400lb and 6in/450lb springs:
My solid rod to press into the bearing holders to attempt to prevent welding distortion:
And I took the time to at least ballpark unsprung weights tonight for shock curve calculation reasons:
Here is the pertinent info I found:
According to my bathroom scale:
-My 15x7.5 TRM C1 + 205/50R15 Direzza ZII Star Specs weight 30.8lbs. Note that according to Tirerack wheel and tire weights this combo should be about 30.2lbs. It's mounted, been driven on a bit(so some small pebbles and crap in the tread), and has a valve stem in it so it's not too far off. I just need my unsprung weights estimated somewhat reasonably close.
-The weight of the left front wheel/tire/suspension is 51lbs. This includes the entire weight of the strut, but done properly by disconnecting the sway bar when measuring. Figure about 46lbs since the weight of the top half of the strut plus the whole upper mount is not really unsprung. For other wheel/tire combos it's somewhere in the neighborhood of 13.5lbs + the weight of your wheel/tire combo.
-The rear weight is much more of a pain to estimate because of the trailing beam suspension, you cannot disconnect the "sway bar" and it all gets weighed at once, and some weight is not fully reflected due to me being lazy and not loosening the trailing beam pivot bolts so some bushing compliance probably mucked up the results. Again I just need close enough. With both shocks unbolted and both springs completely removed, the vehicle in the air, I weighed under each tire.
I got 55lbs for the left rear and 57.6lbs for the right rear. As stated above some is clearly lost due to the beam twisting/bushings/etc. This is obvious because with both wheels hanging the weight doesn't add up to the actual weight of two wheels.
To get an idea of how much weight is transmitted across the beam I unbolted the OPPOSITE side wheel/tire to see how it changes the weights. With the left wheel removed, the weight of the right side dropped to 38lbs. I'm estimating there is about 4-5lbs of unsprung weight per side as I measured it, plus the weight of the wheel/tire itself, I'm estimating maybe 2lbs per side due to bushing compliance error, plus maybe another 1lb to account for 1/2 the weight of the shock and spring which were removed for this procedure. So I'm estimating the rear unsprung weight at around 41lbs per side. Most of the weight of the rear trailing beam is located far forward right at the pivot itself, so it has very little effect on unsprung weight as measured at the wheel centerline.
I'll be putting a bunch of info into the suspension calculator on www.farnorthracing.com to try and establish a decent shock curve to know what to order/specify.
Some other ASSumptions I'll be making:
-I did not corner weigh my car. Based on a combination of Edmunds' total weight plus weight distribution measurements(2280lbs 61.9F/38.1R 1411F/869R) plus what Andy Hollis got his down to in full STF prep trim(2188lbs total, 691LF 639RF 370LR 396RR), mine will be somewhere in between. I just need averages of front and rear weights ignoring left and right. I'll be estimating 1380lbs for TOTAL front weight, and 820lbs for TOTAL rear weight. 2200lbs total. The only weight loss efforts I'll really be making will be in losing the battery up front and pulling the spare/tools/etc and running with no gas in the rear. I'm not pulling airbag equipped seats in my daily driver.
edit: Jasyatz has provided some actual corner weights of a car set up basically exactly like mine, so I'll be using his numbers in hopes of it being a little more realistic for calculations.
For those interested, the front motion ratio is somewhere in the .97-.98 neighborhood which is typical of a strut front end. The rear motion ratio is about .97 at the spring, and 1.23 at the shock. I got these as measured from the beam pivot center to the center of the spring is about 14.5in, to center of the "axle" is 15.0in, and to the shock mount is 18.5in.
This means some conversions are necessary to calculate correct shock damping curves(spring and shock are not coaxial with each other). If you were to move the spring from stock location to the shock location(like the Bilstein kit I believe does, or maybe one of the Fiesta kits, I don't keep up with which ones do what), it means your spring is effectively MUCH stronger/heavier now. A 550lb spring on stock perch is the exact same as a 342lb spring in the shock's location due to the different motion ratios. Or said another way a 550lb spring mounted in the SHOCK location is the same as an 884lb spring in the STOCK location.
This is important because in the calculator, you can only enter one motion ratio(it is assumed the same for both spring and shock). So since I want to estimate a 450lb rear spring(in stock location), but want shock forces needed, I will input the motion ratio of the SHOCK where it asks for it, but for the spring rate I will input "280" as that is the equivalent to what would be needed if it were done like a coilover on the shock itself.
I've also estimated the spring ratio of the tires themselves(since the calculator asks for it). I did this by measuring the height of the tires when they are JUST starting to touch the ground(can still spin by hand but starting to drag a bit), the dropping the car with it's normal weight on it, then measuring the height of the tire again with weight on it. I estimated 700lbs on the left front and 400lbs on the left rear. I unfortunately do not have my measurements around me right now, but basically based on applying a "known"(read: estimated) weight, and being able to measure how much it compresses, you can convert the distance measured to a full inch, then based on the multiplier needed to do that, you apply that same number to the "weight applied" and get the spring rate of the tire.
At least in half-ass theory. I just wanted a number. I came up with 1280lbs/in in front and 1072lbs/in in rear. From my limited reading on this subject this is normal because tires increase in spring rate as load is applied. This also means it will be changing constantly while driving so it probably means nothing. It will also change with tire pressure as well. I just wanted a somewhat realistic number estimated to throw into the calculator. +200-400lbs may be more realistic in dynamic loading situations. I'm not an engineer and don't pretend to be, I just want to do all I can to get a suspension that doesn't suck.
In other news: I got my 7in/400lb and 6in/450lb springs:
My solid rod to press into the bearing holders to attempt to prevent welding distortion:
And I took the time to at least ballpark unsprung weights tonight for shock curve calculation reasons:
Here is the pertinent info I found:
According to my bathroom scale:
-My 15x7.5 TRM C1 + 205/50R15 Direzza ZII Star Specs weight 30.8lbs. Note that according to Tirerack wheel and tire weights this combo should be about 30.2lbs. It's mounted, been driven on a bit(so some small pebbles and crap in the tread), and has a valve stem in it so it's not too far off. I just need my unsprung weights estimated somewhat reasonably close.
-The weight of the left front wheel/tire/suspension is 51lbs. This includes the entire weight of the strut, but done properly by disconnecting the sway bar when measuring. Figure about 46lbs since the weight of the top half of the strut plus the whole upper mount is not really unsprung. For other wheel/tire combos it's somewhere in the neighborhood of 13.5lbs + the weight of your wheel/tire combo.
-The rear weight is much more of a pain to estimate because of the trailing beam suspension, you cannot disconnect the "sway bar" and it all gets weighed at once, and some weight is not fully reflected due to me being lazy and not loosening the trailing beam pivot bolts so some bushing compliance probably mucked up the results. Again I just need close enough. With both shocks unbolted and both springs completely removed, the vehicle in the air, I weighed under each tire.
I got 55lbs for the left rear and 57.6lbs for the right rear. As stated above some is clearly lost due to the beam twisting/bushings/etc. This is obvious because with both wheels hanging the weight doesn't add up to the actual weight of two wheels.
To get an idea of how much weight is transmitted across the beam I unbolted the OPPOSITE side wheel/tire to see how it changes the weights. With the left wheel removed, the weight of the right side dropped to 38lbs. I'm estimating there is about 4-5lbs of unsprung weight per side as I measured it, plus the weight of the wheel/tire itself, I'm estimating maybe 2lbs per side due to bushing compliance error, plus maybe another 1lb to account for 1/2 the weight of the shock and spring which were removed for this procedure. So I'm estimating the rear unsprung weight at around 41lbs per side. Most of the weight of the rear trailing beam is located far forward right at the pivot itself, so it has very little effect on unsprung weight as measured at the wheel centerline.
I'll be putting a bunch of info into the suspension calculator on www.farnorthracing.com to try and establish a decent shock curve to know what to order/specify.
Some other ASSumptions I'll be making:
-I did not corner weigh my car. Based on a combination of Edmunds' total weight plus weight distribution measurements(2280lbs 61.9F/38.1R 1411F/869R) plus what Andy Hollis got his down to in full STF prep trim(2188lbs total, 691LF 639RF 370LR 396RR), mine will be somewhere in between. I just need averages of front and rear weights ignoring left and right. I'll be estimating 1380lbs for TOTAL front weight, and 820lbs for TOTAL rear weight. 2200lbs total. The only weight loss efforts I'll really be making will be in losing the battery up front and pulling the spare/tools/etc and running with no gas in the rear. I'm not pulling airbag equipped seats in my daily driver.
edit: Jasyatz has provided some actual corner weights of a car set up basically exactly like mine, so I'll be using his numbers in hopes of it being a little more realistic for calculations.
For those interested, the front motion ratio is somewhere in the .97-.98 neighborhood which is typical of a strut front end. The rear motion ratio is about .97 at the spring, and 1.23 at the shock. I got these as measured from the beam pivot center to the center of the spring is about 14.5in, to center of the "axle" is 15.0in, and to the shock mount is 18.5in.
This means some conversions are necessary to calculate correct shock damping curves(spring and shock are not coaxial with each other). If you were to move the spring from stock location to the shock location(like the Bilstein kit I believe does, or maybe one of the Fiesta kits, I don't keep up with which ones do what), it means your spring is effectively MUCH stronger/heavier now. A 550lb spring on stock perch is the exact same as a 342lb spring in the shock's location due to the different motion ratios. Or said another way a 550lb spring mounted in the SHOCK location is the same as an 884lb spring in the STOCK location.
This is important because in the calculator, you can only enter one motion ratio(it is assumed the same for both spring and shock). So since I want to estimate a 450lb rear spring(in stock location), but want shock forces needed, I will input the motion ratio of the SHOCK where it asks for it, but for the spring rate I will input "280" as that is the equivalent to what would be needed if it were done like a coilover on the shock itself.
I've also estimated the spring ratio of the tires themselves(since the calculator asks for it). I did this by measuring the height of the tires when they are JUST starting to touch the ground(can still spin by hand but starting to drag a bit), the dropping the car with it's normal weight on it, then measuring the height of the tire again with weight on it. I estimated 700lbs on the left front and 400lbs on the left rear. I unfortunately do not have my measurements around me right now, but basically based on applying a "known"(read: estimated) weight, and being able to measure how much it compresses, you can convert the distance measured to a full inch, then based on the multiplier needed to do that, you apply that same number to the "weight applied" and get the spring rate of the tire.
At least in half-ass theory. I just wanted a number. I came up with 1280lbs/in in front and 1072lbs/in in rear. From my limited reading on this subject this is normal because tires increase in spring rate as load is applied. This also means it will be changing constantly while driving so it probably means nothing. It will also change with tire pressure as well. I just wanted a somewhat realistic number estimated to throw into the calculator. +200-400lbs may be more realistic in dynamic loading situations. I'm not an engineer and don't pretend to be, I just want to do all I can to get a suspension that doesn't suck.
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