Strut Travel on C/O Struts & Bump Stops

[Dave Patten]

I kind of got off track on the "SSW Front Coils worth the money?" thread regarding coil bind on short springs.

I know their are many people just adding C/O over kits, lowering their cars without worrying about travel and then end up wondering why their cars don't handle all that great. Byron 510 also mentioned suitable bump stops. This adds another aspect to the travel topic.

Given the popular coil over set-up for a 510 is to use an MR2 cartridge in a shortened 280ZX strut where do folks try to establish ride height within the strut's travel distance?

Should it be 50/50? 60% bumptravel? More? Given a short cartridge has about 6" of travel and the C/O hat takes away .5" or so, use of a bump stop limits travel even more.

Does anyone have a rule of tumb they use for amount of bump travel? and comments on bumpstops.

[okayfine]

Given the popular coil over set-up for a 510 is to use an MR2 cartridge in a shortened 280ZX strut where do folks try to establish ride height within the strut's travel distance?

I don't know if the MR2 strut is popular. I think it is used mainly by those looking for the lowest ride heights while still maintaining some suspension travel. Still applicable for the discussion, of course.

Purloined from a separate discussion:

"A soft, progressive urethane foam bump stop like the ones used on every modern car will let you actually use that last 2 inches of travel, not just get bounced off of it. Sadly, I know of no science to predict exactly what you need, but start some trial and error with foam stops and you'll be amazed. If you can't find a good source of cast-off production parts, Koni makes some too."

[James]

Purloined

Word for the day

[rnorrish]

Purloined

Word for the day

I prefer sirloined.

[James]

http://www.youtube.com/watch?v=8Qtgm5g5Gyo

[hang_510]

I prefer sirloined.

i dub thee: Sir Loin.


BUMP stop to get back on track!

[okayfine]

Should it be 50/50? 60% bumptravel?

Suspension theory isn't one of my strong points, but I'd think it should be less.

More travel with just the spring rate. This way you'll know better how it will react as you spec the spring rate, intead of trying to interpret the amount of addition rate the bump stops will add. Bump stops should be thick enough to be effective (in preventing metal-on-metal contact) but not overly generous (adding rate way before metal-on-metal is possible). I would also think that setting up to eliminate coil stacking isn't the job of the bumpstop, but the job of the correct spring.

[Byron510]

Well, for what it is worth...

On the Bronze I run 275# springs up front and have 2 1/2" of bump with 1 1/2" droop for my ride height - 3" at front X member (effective droop before the spring actually comes loose - I need to install one of those nice stacking flat springs to keep it all under tension when airborne!).

Works fine, I really have to hit a good hole in my car to bottom the front suspension on the bump stops. I have done it at elevated speeds while hitting a bit of a sink hole on the highway. the rear of my car is another issue - no bumpstops = not good, I know!

I did take the front X member out a few years ago in a road construction area – always a worry in a low car…

http://www.the510realm.com/viewtopic.ph ... s&start=15

Unfortunately it looks like the photos are gone, but those guys are still in my good books today for helping me out that night! Proof that the suspension does compress a whole lot more than it ever had before (or since)

Byron

[speeder]

This might be a good starting point:

http://www.thezstore.com/page/TZS/PROD/23-4196

[bertvorgon]

I am basically the same as Byron 2.5 - 2.75" bump, with #300 front springs. I have only just touched once at the front, at very high speed, on the Duffy Lake road.

On very hard toss in's, on sticky race tires, at the slaloms, I never once felt I went through the travel. It always felt like there was compliance, which it obviously needed. Even on the Specialty road race cars at the time, we used about the same travel, with one of the cars running #350 springs. I have my front shocks set at about a 50/50 rate ( custom valved Bistein).

I only run a small bump rubber in there, maybe 1/2" thick. After the crash I had, I have never even wanted to get near a bump stop, even though I know some times silastics are used to "tune" the suspension some times. I have just felt that the spring will be my constant, with out trying to figure in some thing else that is deforming. Let the spring do it's job.

I do not even run a bump stop at the rear....if I get to a coil bind point...I have more serious issues happening, than the need for a bump stop, at least with my set up. My shock has more than enough travel at the rear, my spring would bind up, before the shock hits it's final point.

Having traveled the Duffy Lake road, at it's bumpiest time, at very high speed, 100+ MPH, which I consider to have been the worst of any bump/dip situation, not once did my rear end lose it's composure. Any of our group that has driven that road at true speed, will understand what I mean.

If you read Carrol Smith's book, TUNE TO WIN, while he does talk about silastics, he really does say let the springs do their job, making sure they do not rattle around on droop.

So, at least in some of our cases up here, our setups seem to work very well, with the 2.5 - 2.75" of travel out front, and about 3" out back.

[Baz]

we have a race strut using a 180mm spring (7") 275 lb.
No coil binding & spring is fully captive.
We can actually preload this.
Just measure & calc all variables first.
Included link so you can check the saddle height.

http://www.datsport.com/strut-dsk280R.html