This post from your compatriot Black3sr sums it up. (Bear in mind they drive a GE8):

from thread:
https://www.fitfreak.net/forums/2nd-...e-quality.html

 

You mentioned that OE rides on bumps so the photos were just a visual example how it looks like with around an inch drop in the front. Both front and rear bumps are around an inch away from strut cylinders on a stock suspension. You could actually test this by opening the rear hatch and use hands to push the car down. On OE it will allow movement up until the bumps, on your modified it will allow just ever so slightly.

I'm willing to bet 50 bucks you're already on bumps in front judging by the stance in the photos and replacing these with uncut ones will raise your front and it might actually be less stiff and will invoke bounciness because that doughnut you already cut off is the softest part of the bump.

 

You're spot on on what a perceived tradeoff should be based on your previous car and for you there shouldn't really be any fiddling involved to have that.
Why I'm fiddling with it is because of whatever, maybe I made a wrong purchasing decision but lets see and jhn seems to like it very much and is a hobby racer.

It all depends on the spring rate and more importantly, the drop.

Moderate tradeoff would be -20 mm on this car with similar spring rate as stock and optionally, with upgraded struts; something like jhn has.

Major tradeoff would be if drop is -25 mm or more as you'd be running on the jounce springs and the spring rate on those is extremely progressive, gives a bouncy ride.

This is what I gathered so far:

Stock spring rate: F1.8/R2.1 kgf/mm

High.tech spring rate: F2.1/R2.3 kgf/mm -30 mm (different variations in drop between different car versions)

Mugen suspension kit: F1.9/R2.0 kgf/mm -20 mm drop (variations in spring rate depending on the kit for each car version but maintained drop)

Distance between bump stop and strut body: around 30 mm

I've included Mugen kit as an example of a different approach (and much more expensive because Mugen) compared to currently available spring replacements (with possible exception of new swifts) because of it's approach to get what you and me seem to look for, sportier feedback with a relatively maintained comfort level.

They used nearly identical spring rate for 20 mm drop, replaced the struts and it looks (from photos to me, not easy to find and inspect unfortunately) that rest of the components are same as stock; bumps, steering mounts etc.

 

I'm at about 4cm drop in the front right now, depending on how level the car is sitting. I'm thinking about replacing the bumpers to increase the rate in the early part of the stroke. Keep in mind elastomer doesn't function like a raw, undamped spring. It has some inherent damping characteristics.

It's possible it will increase ride height a bit, but the amount I cut off was around 15-20 mm or so. I really don't think it will more than a few mm.


This car has an inherent pushing problem and adding the extra bumper can only make it worse, even the slight amount it adds.

 

What you cut off is the _softest_ part. This doughnut has an internal groove to make it softer.
If I were you, I'd cut one more ring off if pushing is the problem, because it constantly pushes against the bumps.

Test it before cutting, install one strut without the dust boot and have a look at it at rest. I'd hazard a guess here you couldn't go wrong with around 30mm spacing between the cylinder and the bump.

 

Good discussion. Since you're talking bump stops, my (stock) rear stops got rock hard this winter on the coldest days, did anyone else notice this happening?
It cut my rear suspension travel in half or worse, and made the back end buck on frost heaves and rough pavement.
Nasty, worse than my speed3, way worse than my Fit Sport.

 

Thanks for the explanations CN Fit. I'll just have to decide if the dropped look is worth a few hundred bucks for a harsher ride. I'm not sure. I'm not as young as I used to be and I appreciate comfort more and more. The tire and wheel change have already had an impact on comfort levels even if it's not drastic.

 

Not what I want to see but probably very close to reality.

 

I disagree. I think you're obsessing over this bumpstop contact thing like its a problem. My spring mfr says no, don't cut them. Your mfr does specify them to be cut, which tells me they're either designed more for racing with a stiffer rate, or they didn't incorporate the jounce into their rate like they should have.

Either way, cut away if you think think you should. Here's something if you haven't already seen it:


Technical || H&R Special Springs, LP

 

On another note: The OE dampers are position specific, so any lowering changes the operating range of travel, which not only doesn't allow them to operate properly, it will shorten the service life.

If I were you, and unless your springs just have too high a rate to suit your needs, I'd focus on addressing the dampers.

 

Not obsessing over it, just including them as an _almost_ equal member of the stock suspension setup that is creating me a particular problem with these springs I have. I'm also trying to explain you what they shouldn't be doing but you seem to have a different opinion and that's fine, really.

 

OE dampers aren't position specific and the only reason why it shortens service life is if you bottom them out, hit the valving into cylinder bottom. Aftermarket springs are designed to fit on them.

Spring rate is fine, I'm quite happy with how front behaves.
I'm looking at the konis too but for the bound/rebound character and this will come at much later date, not really interested in it now.

I'm gonna reiterate:
stock height 365 mm
Lowered 330 mm
Struts disconnected 310 mm
This is where my problem is, rear is rock solid on an empty car. I don't have to obsess over anything, it's pretty much clear as a day to me that bumps are doing all the work. They're not touching, not preloaded, but fully engaged!

Put two people in the back and watch them launch into ceiling on speed bumps, it makes up on the fun part.

 

Although bottoming could happen (another reason not to cut the jounces), the issue that causes accelerated wear is shock shaft displacement. As the shock shaft inserts into the body, it displaces fluid/ gas, increasing internal pressure. This not only effects the function of the shim stack, but it also shortens the service life of the seals. It could be possible higher internal pressure is supporting the ride height.

 

We're talking here of fit with its stock struts and of aftermarket lowering springs designed for those struts. If those struts would do anything _but_ dampen the vibration, let alone maintain car height at rest, it wouldn't be a budget family car anymore. The biggest reason why those fail sooner than later has more to do with the person driving the vehicle that had those springs installed in the first place than anything else because heat. Same reason your tires will go, brake pads, engine..

 

I will reiterate that I am less technically minded than you guys but your post reminded me of something I read on the Toyota Echo forums a long time ago. People were discussing lowering springs much like we are doing here. Many said that the springs alone (without changing to performance shocks) would make the OE shocks leak and eventually destroy them after a few years. Some actually witnessed this problem themselves on their own setup. I went ahead and put some Tein's on mine anyway ignoring their warnings. Like I said, after 10 years, I was still riding on stock Toyota shocks. They weren't leaking nor broken after all those years.

CN Fit, I certainly believe that the way one drives might make a difference in part longevity but could the spring brand itself make a difference in comfort levels, OE strut longevity and handling regardless of the amount of drop or spring rate ? Some of them probably put more hours into actually testing their products on street and track before putting them up for sale.

 

That's painting with a very broad brush there. If one is looking for circuit days and also drives on crappy roads on stock shocks they're gonna fail in a few months time easily.

What you experienced is probably in line with how and where you have had driven. You we're probably more cautious around bumps, rarely if ever went up on sidewalks, avoided rough roads if choice was available and had rarely pushed the car into curves.

I don't really see how spring vendor choice could affect strut life in the 10 yr span, talking here of premium, recognizable brands with racetrack pedigree. They all have good practices in place that trickled down from races and inherent advancements in technology.

Stiffer spring and lower profile tires will make struts work harder and last shorter, I'm not giving mines on 17 inch more than 60 000 km, judging by the roads I'm driving on. It's possible that many of them who experienced earlier failure also had bigger wheels on.