Koni 8611/8610 Spring Rate Advice - MR2 Owners Club Message Board
 
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post #1 of 18 (permalink) Old April 4th, 2019, 10:25 Thread Starter
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Question Koni 8611/8610 Spring Rate Advice

I'm working towards putting together my Koni 8611/8610 setup. I have 8611-1257's for up front, and a pair of 8610-1437 for the rear.

I'm going to do something with some machined aluminum sleeves I had made up a while ago that will give me adjustability on the lower spindle mount, at least up front I will, will probably weld up something permanent on the rear.



So my question is spring rates:

My goals: Primarily street, some track work with sticky street tires or 100 tw NT-01s or the like. No aero. Max tires widths 235/255. It's not a daily, but I do want a pretty comfortable car for cruising and am willing to sacrifice some speed on track for it (this is not a car I'm trying to keep up with super fast modern metal with). But it needs enough composure not to flop over on the bumpstops all the time and destroy the shoulders of tires etc. I also have Tein Street Basis coils on the car now, and I feel like the rates are in the ballpark of what I'd want at 4/7 kg/mm.

For a street/track car, Alex W has a recommendation for a street application of 250 front / 350 rear up to 350/450, with maybe the front rate dropping some if you're willing to play with sway bars.

I have stock 1993 sways, but I've considered going with an ST front sway to get some adjustability with roll stiffness front/rear.

Rates: How does something like 275/400 sound? That's about 4.9/7.1? I also have some 6.6 kg/mm ERS springs sitting around, but I think they're only 7" long. I can't imagine those would work in the rear without coilbinding everywhere?

Length: With the above rough range, what sort of lengths would I need front/rear? Maybe 8" front and rear? Does that fit well? The rear looks a little low on block load vs. static load (I generally try to keep a roughly 2x margin between the two), so maybe 10" on the rear?

I'm also thinking of tender springs in at least the rear to make sure the rear stays in contact, especially driving around the street up driveways etc., but that's something that's not too critical on what rate they are as long as they can push against the sway at full droop a bit.
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post #2 of 18 (permalink) Old April 4th, 2019, 11:55
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To give you another date point, since you rode in my car, that was with 400f, 550r. I run 7" springs front and rear, with helper springs.


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post #3 of 18 (permalink) Old April 4th, 2019, 15:01 Thread Starter
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Yep, that felt good, but maybe a bit higher ride frequency than I'm looking for.

Do you have any pics to show the travel of your coilover housings at rest at your given ride height? And do you run full length Koni bump stops?
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post #4 of 18 (permalink) Old April 5th, 2019, 19:06 Thread Starter
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Aren't a lot of people running these struts on their MR2???
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post #5 of 18 (permalink) Old April 5th, 2019, 19:43
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Quote:
Originally Posted by DefSport View Post
Yep, that felt good, but maybe a bit higher ride frequency than I'm looking for.

Do you have any pics to show the travel of your coilover housings at rest at your given ride height? And do you run full length Koni bump stops?
I trim the bump stops by about 3/4 inch. I will try to get some measurement or pictures at ride height, but it will be a few days.

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Aren't a lot of people running these struts on their MR2???
At least a dozen that have bought my setup, and I'm sure more that have gone the DIY route. I'm not sure if that counts as a lot or not!


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post #6 of 18 (permalink) Old April 5th, 2019, 19:58 Thread Starter
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Interesting, I thought it was more than that. I've sold about 40 pairs of my threaded sleeves for Nissan S chassis guys, and I'd say there's another 50-80 pairs of fixed housings out there in the wild.

I thought it was comparable on the MR2 side of things, but apparently not.

What kind of spring rates and lengths do most people go with for a street/track build? I can use spring preload to my advantage up front with having the lower mount being adjustable, but I'm concerned in the rear of potentially needing a 10" long spring at ~400 lb/in or a bit less to keep things from coil binding in a corner and encountering a bump.

I know the 7" 6.6 kg/mm (370 lb/in) springs would coil bind in my S13 on the rear, and the corner weights were like 625-650 lbs (including unsprung weight). I know the MR2 will be an easy 30-40% more than that, so I'm worried an 8" won't work out back there.
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post #7 of 18 (permalink) Old April 6th, 2019, 12:19 Thread Starter
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Originally Posted by Alex W View Post
I trim the bump stops by about 3/4 inch. I will try to get some measurement or pictures at ride height, but it will be a few days.

And thanks for being willing to put out some more detailed info on this. I've got a bit of a blank slate on how to fab up my rear housings, and the front housings I can adjust a lot(thinking of putting the sway bar connection on the lower spindle bracket so I don't have anything permanently on the housing blocking adjustment), so I'm wondering if I should bias things one way or the other for travel etc. I feel like things are more critical when you're running spring rates on the softer side and you're really using a lot more travel in general cornering/braking forces.

Have you found yourself ever contacting the bumpstops on your setup, which is why you trim them 3/4"?
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post #8 of 18 (permalink) Old April 6th, 2019, 15:45 Thread Starter
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Any potential interference with things using an 8" spring front and rear, with probably tender springs in the rear, maybe front?


I have some 50 lb/in H&R tenders, which are really just barely above helper rates, but I was thinking of aiming for something more in the 100-200 lb/in range for a tender with about 1-1.5" of travel to help make the car that little bit more civilized on the street, going up into driveways/angled entrances etc.
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post #9 of 18 (permalink) Old April 7th, 2019, 00:16
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It'll be interesting to see how you get on with these.
I ran 8611's in the front of my Alltrac for a while and flogged them out in no-time
They lasted about 12 months, maybe 5,000 miles.

I think they are designed for light weight club racing cars, open wheelers, etc.
They couldn't handle the side-loading on the shaft that 3deg camber, 5deg caster, the weight and accel/braking put through them.

They did work great while they lasted though.

Im now running these: https://streetwiseparts.com/collecti...rts-strut-46mm
No way these will have that same problem.
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post #10 of 18 (permalink) Old April 7th, 2019, 10:50 Thread Starter
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I ran them for about 70+ track days and probably 5k mi on the street and they were still solid when I sold my S13. It was a bit lighter than my MR2, but it also had aero and would sustain cornering in the 1.4-1.5 G range.
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post #11 of 18 (permalink) Old April 11th, 2019, 15:21 Thread Starter
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Anybody?

I've done some more reading on swaybars, and it sounds like the adjustable front swaybar doesn't work due to an out of plane load on the strut causing a steering moment. So I'll just plan to stick with stock '93 bars for now.


How does 300/400 sound? That's roughly the same front/rear stiffness split as Alex W's 400/550 (at 75% front stiffness vs. 72.7% of the 400/550), and dropping the rates all around by the same ~25%.

Are 8" springs the answer? That would give at least 5" of main spring travel, which seems a safe place to be on an 861x setup (5.6" front, 6.0" rear travel). A 7" spring is down in the ~4.2-4.5" of travel, which seems potentially risk of coilbinding before using a reasonable amount of bumpstop travel.

Do the 8" springs cause things to interfere with each other?
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post #12 of 18 (permalink) Old April 11th, 2019, 20:48
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I'm running with FA coilovers , but I have 300/400 right now with the ST front bar. I like it, not too bad around town. With the ST bar it is ultimately a bit pushy but does manage very stable on-power rotation. I'm also running 225/245 stagger at the moment. I will probably play around with spring rate in the future once I change my tires. Likely going 245/255 next to keep within 17" street tire sizes.

I run a 7" rear spring and that is fine for a reasonable range of ride heights. For the front I went to a short 5" spring. This allows me to keep the top of the tire below the spring - but this only works for short 15" tires. At the time I was thinking about stuffing a 275 hoosier in front, and it should fit in the fender. I'd run a 6" spring otherwise. Depending on the height of the sway link connection you may not get low enough with a 7" spring. Buy hypercos and measure travel and I don't think you should have coil bind issues. i run a progressive bump stop as well. Right now I have like no droop but I need to add some helpers to the setup.

I originally wanted to make some threaded sleeves like yours to adapt konis to the FA hub mounts...I lost motivation

Last edited by Tritsch; April 11th, 2019 at 20:51.
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post #13 of 18 (permalink) Old April 12th, 2019, 12:44 Thread Starter
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A 5" spring sound entirely too short to use even half the travel on the Konis.

I found some mentions of an 8" spring in the rear potentially running the spring perch into the unibody on full droop (Alex W mentioned it, guessing his camber plates aggressive upper position makes it tight on the inside). Since I'll be running those same camber plates, I'm a bit nervous going with an 8" spring and confirming the issue.

So looks like I'll go with 7" 300 lb/in front and 7" 400 lb/in rears. The rears are a little light on travel, with only about 750-800 lb more load capacity available before coilbind. That's about ~1.7 G equivalent load, so maybe enough with some contribution from a fairly long bump stop to give a more progressive rate towards the end of travel?

The front 7" 300 lb/in looks like it has plenty of capacity. The 6" is way too tight, so no go there. 8" might make things tight on setting ride height.



So I guess in the absence of any other better info, I'll just send it with these rates/lengths and see how it goes.
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post #14 of 18 (permalink) Old April 12th, 2019, 14:18
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Don't forget that on my setup, probably 1.5" of travel is in the helper spring. With fully threaded housings and no helper springs, more travel may be required on the main springs. Although in my experience, even with my helper springs using up that much travel, the tire will still rub the chassis before I run out of strut travel (of course, tire diameter is a factor here). In your case with fully threaded housings, you probably won't ever hit the bump stops, but you still may not need any more spring travel.

300/400 sounds like a pretty good street setup to me...


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post #15 of 18 (permalink) Old April 12th, 2019, 19:55 Thread Starter
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Quote:
Originally Posted by Alex W View Post
Don't forget that on my setup, probably 1.5" of travel is in the helper spring. With fully threaded housings and no helper springs, more travel may be required on the main springs. Although in my experience, even with my helper springs using up that much travel, the tire will still rub the chassis before I run out of strut travel (of course, tire diameter is a factor here). In your case with fully threaded housings, you probably won't ever hit the bump stops, but you still may not need any more spring travel.

300/400 sounds like a pretty good street setup to me...
I kept that in mind. I'll have about 4.5" of spring travel to block up front (~2.5" travel past static) and ~4.2" of main spring travel in the rear (again, about ~2-2.25" beyond static). I'll also run some 50 lb/in H&R tenders in the rear (more like stiff helpers) that have 1" of travel to get full travel in the rear on steep slopes etc. So I'll have roughly 75% the shock travel up front to coilbind, and about the same in the rear.

The fronts I'm a little worried of running out of room to put everything in (spring perch, swaybar link, lower bracket with lock etc.), so I went with a 7" there. The rears, I'll not use a lower adjustable mount, and I'll put it in roughly the same location you use for your housings, so it should work out ok I think, if maybe a bit heavy on bumpstop usage in corners and hitting bumps.

7" all around seemed like a good starting point, and I'll need to really see where the deficiencies are (if any) to make an informed decision past that. If I was to go 8" anywhere, it'd probably be up front where I could potentially run zero, or even some positive spring preload at my desired ride height. But again, gotta fit everything on the threaded housing and the 8" spring might start getting a tad tight on things based on a few rough dimensions. Plus I don't think I can really use ALL 5.6" of travel an 8611-1257 gives up front through the spring. So I might end up with a big ole' bumpstop, and rely on spring coilbind as a hard limiter at the very end of the bumpstop compression where the rate might as well be near infinite anyway. I don't imagine I'll use it often on this car, but maybe I'm underestimating how much the suspension will move.

Anyway, we'll see how she does once I get it all put together. This is a summer project where I won't have to take the car down for extended periods of time, wrenching on it 2-3 hrs per week. I can take measurements, mock stuff up, pull it off and keep the car driveable during our dry summers.
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post #16 of 18 (permalink) Old April 13th, 2019, 22:15
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post #17 of 18 (permalink) Old April 14th, 2019, 21:49
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There's not much room in there up front. You'll get to make your own sway link mount that is a bit shorter, but with the FA lower hub mount, an 8" spring would not be able to go down to stock ride height in front. As-is the provided 7" spring could only get about 3/4" lower than stock ride height. If you add in Alex's upper mounts (which I do recommend) you lose a bit more room too. I only have about 1" of wheel travel from static currently, 3" total travel. Even with a 5" spring I can hit the tire on the fender before coil bind and I don't run particularly low, about 1.25" lower than stock. I limited the travel because I didn't like the bump steer effects and I use the progressive stop to add rate.
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post #18 of 18 (permalink) Old April 14th, 2019, 22:29 Thread Starter
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Interesting, I guess I'll have to see how it all packages up front. I was going to weld on a sway bar endlink attachment up front on the lower spindle mount. Figure I can put it where I want it there.

I guess we'll find out if the 8611 in a height adjustable spindle mount setup is pointless or not. It was at least nice to have on an S-chassis because of the prevalence of "drop knuckles," which require completely different length coilover mount placement to use.
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