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Suspension and spring choice for a factory smooth ride
For shocks I went with the factory GR2 replacement inserts and agx adjustable in the rear on full soft.
Roads here are horrible! I don’t want to drive a stiff rattle trap. Not really concerned with cornering it’s a straight line “drag/hotrod cruiser” setup.
Got a set of adjustable coil over mounts on and I have new 2.5” x 12 125# springs. (had these springs from a past vehicle).
From what I’ve read the factory FWD springs are 120#? Are the non-progressive springs (IE same diameter the entire length) a ton firmer than a factory style progressive spring?
I can push down the factory spring by hand a good 2” or more. It feels REALLY weak in comparison to my new 2.5” 125# spring.
Just curious if anyone has had direct experience with this before I install it all and test it out. Feel like these may be too stiff.
I have 250# in the front and 200 5"x8" (really its 100# 5x16 cut in half). IIRC, replaced and removed an inch off the urethane bumpstops.
Front *could* be a little softer, the rear definitely could be softer and longer (maybe I'm kissing the bumpstop though..) Out of the two I frequently consider finding 75# 5x20 spring (again cut in half). The suspension was well past due when I bought the car so I don't have a comparison.
Old springs could have worn out over time. On Mazdatrix's old site they measured OEM springs at 100lb/in.
Racing Beat's front springs are 145lb/in.
Have you driven with the GR2 struts yet? New dampers will make for a less bouncy ride but that may be negated if you switch to a spring that's too soft.
Appreciate the input. I haven’t driven on the gr2 cartridges yet in this car. I did have a set on my old car and it felt ok. But I had an unknown spring in that chassis.
Just got the drivers side assembled and installed last night. Spring compressors are a pain to get in/out these little 2.5” shocks! Going by my shade tree mechanic methods, these 125# springs are MUCH firmer. Worried they may be too stiff, but time will tell now. I’m already committed at this point.
I’m sure the OEM springs were shot. This chassis had 198k on it and they appear to be original equipment. Had the original completely blown strut as well.
They had 100 and 90# options in this same spring so I can always change them out later if I have to. I’ll keep this up to date and let you know.
Springs are cheap circle track stuff from speedway motors with their cheap 2" blisteen coil over sleeve. Had to trim the sleeve down about 2” to clear the gland nut thing that holds the cartridge in and drill the top spring hat out a bit. But otherwise it was a bolt on affair.
Yeti - Your spring set-up is pretty close to the old Pro7 specification. Fronts were 275-350 and rears were 175 5x9. I used 350 fronts with 200 (5x8) rear for quite awhile and that was very stiff and race oriented. Eventually ended up last few years of racing with 450-250. Also, if you didn't trim the bumpstop, you are almost certainly bottoming out from time to time. I think I removed 2/3 of the stop to avoid bottoming out under normal race conditions. I needed the last third to keep the lower spring perch from hitting the "frame" during offroad excursions.
Yeah, now that you mention it I probably should have included that note. I did more or less base it off Pro7 specs. I tried to err on the softer side because I didn't want it to ride like a truck. I'll try to keep my comments short as I don't think this setup will be acceptable for vxturboxv based on more recent comments. But while I may have Carl's attention front struts are Koni 8610 race cartridges and the rear are Bilstein 24-024075 Camaro shocks. Which I wasn't totally sure if they'd be acceptable or not and may be why the rear is so harsh. I'm open to suggestions.
This all said.. my DD is a 2007 Mazdaspeed 3 with the only suspension being Bilstein shocks and I'd say the ride between the two is comparable. Sure the rx7 is stiffer but at least with my East TN roads not terrible.
Edit: Oh and yeah the bumpstop is trimmed maybe not enough though. I need to apply some grease and go for a drive.
In response to yeti. I would say that the 200lb springs in the rear are probably pretty harsh for the street. The Camaro Bilsteins might contribute as well. I used Mustang Bilsteins (probably similar to Camaro spec) with 200lb springs and the race ride was not good. The Mustang Bilsteins worked well with 250 rears (and 450 fronts). Tokico blues or Illuminas on mid settings worked pretty well with the 200lb rears. It was still a race ride tho. Not particularly pleasant on the street.
So got it all together and test drove it. Rides really well I think. Hard to tell 100% because the rear is still so stiff. Need to get a super light spring in the back Hope the loosest setting on the AGX shock isn't to firm. Sits a tad high up front. Has a little alum block/head small block in it. I thought it'd sag more with 125lbs springs. Will be interesting to see what the front wheel weights are here soon. Guessing they are less than I thought they'd be.
08-27-24, 11:32 AM
