Ultimate Street suspension guide

[Advancedynamix]

Like Brad said, the VW rear shocks are shorter and don't require that mod.
On the KYB Aspire shocks, yes I shorten them 3“. I cut the shafts up by the locator bushing for the bump stop. I cut 3 inches out of the shaft, then drill and tap both parts ¹/⁴-28 and use a stud to hold them together and I tig weld the shaft back together.



These are pictures of a set of Tein coilovers that I shortened, so the shaft looks different than the KYB Aspire shocks, but the procedure is the same.

The MK2 rear coilovers are not worth using unless you want to lift your Festiva. The shock bodies themselves are way too long.

[Festiver]

No that was the festiva struts he originally used. That's what's been bothering me about this thread.

Ohhh alright cool that's what I was worried about and what do you mean it's a little bit of a mess but still good info



Sent from my XT1585 using Tapatalk

[bhazard]

Yes but I thought he took an additional 3" out of the mk1 kybs and the mk2 coilovers


Sent from my XT1585 using Tapatalk

No that was the festiva struts he originally used. That's what's been bothering me about this thread.

[Festiver]

Most of the info in this thread is obsolete. The current technique is to use the rear struts for a mk1 VW rabbit/golf. They are already shorter.

Yes but I thought he took an additional 3" out of the mk1 kybs and the mk2 coilovers


Sent from my XT1585 using Tapatalk

[bhazard]

Quick question this doesn't relate to the quote I'm using but you shortened the length of the shock what 3"? How did you shorten this the bit of info I just can't find

Sent from my XT1585 using Tapatalk

Most of the info in this thread is obsolete. The current technique is to use the rear struts for a mk1 VW rabbit/golf. They are already shorter.

[Festiver]

I was only saying that comparing 2 completely different spring designs by the pressure rating confuses the issue. A bulk of the questions I get concerning peoples suspension setup is based on this confusion that spring rate numbers are the only thing to consider when choosing a spring. The only reason I can recommend the rates that I do with the Southwest speed springs, is because I've tested everything from 105-200 lb of their particular spring product on several Festivas. That doesn't mean I know what x (insert other random kind of spring) will behave like on x (insert other random shock absorber). When people use my spring rate suggestions to select other springs to put on another type of shock, they are on their own. I can only vouch for the products I have personally tested.
The Miata springs you have been using seem to work great with the stock replacement KYB aspire shocks that you have been using. They may also work with the VW mk1 kyb shocks, except you won't have enough tire clearance for the large tires that you run. I theorize that a set of 150lb Southwest speed springs on the VW KYB shocks will work as well, or better than the setup your running, but we won't know until you try it. I fear that this setup will have too low a ride height for your liking though. The 150lb 1 7/8 springs on stock replacement KYB shocks are a little bouncy. That is what is on Tweak, and you've seen the difference first hand on a track. Towing a trailer may not yeild the same results though.

Quick question this doesn't relate to the quote I'm using but you shortened the length of the shock what 3"? How did you shorten this the bit of info I just can't find

Sent from my XT1585 using Tapatalk

[Dragonhealer]

I think you are right to both, will machine up a pair of tophats to compensate for the shorter spring. Anxious to see the difference with the VW shock.
The extra advantage of lowering the rear when unladen would be cool too!

[Advancedynamix]

I was only saying that comparing 2 completely different spring designs by the pressure rating confuses the issue. A bulk of the questions I get concerning peoples suspension setup is based on this confusion that spring rate numbers are the only thing to consider when choosing a spring. The only reason I can recommend the rates that I do with the Southwest speed springs, is because I've tested everything from 105-200 lb of their particular spring product on several Festivas. That doesn't mean I know what x (insert other random kind of spring) will behave like on x (insert other random shock absorber). When people use my spring rate suggestions to select other springs to put on another type of shock, they are on their own. I can only vouch for the products I have personally tested.
The Miata springs you have been using seem to work great with the stock replacement KYB aspire shocks that you have been using. They may also work with the VW mk1 kyb shocks, except you won't have enough tire clearance for the large tires that you run. I theorize that a set of 150lb Southwest speed springs on the VW KYB shocks will work as well, or better than the setup your running, but we won't know until you try it. I fear that this setup will have too low a ride height for your liking though. The 150lb 1 7/8 springs on stock replacement KYB shocks are a little bouncy. That is what is on Tweak, and you've seen the difference first hand on a track. Towing a trailer may not yeild the same results though.

[Dragonhealer]

Still apples and bananas, I know. 10" vs 12", small diameter spring vs large diameter spring, small coil stock vs much heaver coil stock, high energy density vs much lower energy density. But at 12% difference, I thought it worth a try. Scratch the 12%, there is a square function in the density formula. but the spring frequency should be within 12% or so, and the loaded ride height (and associated bump and rebound travel) are about right.

Just not sure why it works!

[Dragonhealer]

Perhaps so, my memory ain't what it once was, but I'll bet I put the NB Miata front springs in the rear of Rosie after you posted this, from: Advanced Suspension Mods, Post #435; (bold added for clarity)

http://i1094.photobucket.com/albums/...pspjfbttdi.jpg

Then I use a 10" long 1 7/8 diameter springs from southwest speed.
I used 105lb springs on this car, as a test. This spring will allow for 7" wide wheels and 4 degrees of negative camber in the back, while still being able to ride 4 or more inches lower than stock. For a car that's only running 2-3" lower, with a typical festiva load, I'd suggest 120lb springs. For a car being used to tow or carry extra weight in the back I suggest 150lb springs.

The base spring rate effects the rate at which the spring rate rises. Running too stiff a base rate will cause the car to ride too high and feel stiff and bouncy. These VW shocks have a lot of rebound dampening, so 150lb springs won't feel bouncy, but they will give a very firm ride and could cause the car to tend to drift.

Last edited by Advancedynamix; 10-21-2015 at 10:29 AM.

[Advancedynamix]

Thanks Charlie, a timely warning.
Can you just delete this post to avoid confusion in what is a great thread?

I'd rather leave it. You brought up a great point, that needs to be discussed. Spring tuning is not a "paint by numbers" picture. You and I have dealt with this many times on race cars, but most people don't hear the facts about chassis tuning.
Your suggestion is extremely valuable. You've really dialed in a Festiva for towing. I am amazed that you safely tow loads that outweigh the car your using to tow with, at freeway speeds, in the middle of the desert! I've seen it work, time and time again, and it never ceases to drop my jaw. Your setup is perfect for Ryan, or anyone else who wants to tow a heavy load over rough terrain. It does fall into the category of "ultimate suspension".

[Dragonhealer]

Thanks Charlie, a timely warning.
Can you just delete this post to avoid confusion in what is a great thread?

[Advancedynamix]

85/150 for 2500 pound trailer?
Ryanprins13 asked me what I had set up on Rosie to tow a vastly overweight load, and I wasn't sure so I took it apart and measured.
Suprised me too, towing it is very solid, but feels nervous when empty and a little dicey.
Aspire swap front and rear,
front and rear struts are GR2's for Festiva, front spring is Festiva 85lb/in, rear spring is 1999/2000 Miata FRONT spring 150lb/in with the long VW bump stop which adds to spring rate after 1 inch of travel .
I'm not sure why this works, less weight on the front axel when 400 pounds on the hitch?

This does not apply to the springs we use on these coilovers.
Spring rate numbers can be very confusing. The rate numbers are meaningless without a full explanation of the springs (ie wire diameter, distance between coils, length of spring, and winding diameter.) A 150lb rear 1 7/8 I.D. spring will be behave much differently than a 150lb OEM spring because the 2 springs are different shape, length and diameter, as well as being made of different wire.
The spring rate tells very little about the actual tension of the spring when installed and compressed, or how it will behave when compressed 4 or 5 inches. We should never use rate alone to compare 2 completely different spring designs, because this is misleading, and will confuse people.

[Dragonhealer]

120/105 with stock engine placement. 150/105 for g series.

150/120 for heavy loads.

85/150 for 2500 pound trailer?
Ryanprins13 asked me what I had set up on Rosie to tow a vastly overweight load, and I wasn't sure so I took it apart and measured.
Suprised me too, towing it is very solid, but feels nervous when empty and a little dicey.
Aspire swap front and rear,
front and rear struts are GR2's for Festiva, front spring is Festiva 85lb/in, rear spring is 1999/2000 Miata FRONT spring 150lb/in with the long VW bump stop which adds to spring rate after 1 inch of travel .
I'm not sure why this works, less weight on the front axel when 400 pounds on the hitch?

[Advancedynamix]

I've seen those on my Festivas too. They do go between the strut mount and the body of the car.