Alright folks, for those of you running higher spring rates, I need some help. I'm at 400/600 on my revalved Konis right now, and in general it feels good. But under hard high speed, late braking, the car is absolutely wild. Ask Corey... He got a good view... Shoulda seen when I went into T1 pointing left! The rear end just dances all over the place. If I brake about half a marker back, then the car brakes normally (rear end just a little light), but what fun is that?

I'm running hawk blues front and rear. Revalved Koni yellows w/ 400F/600R. Oh, and I'm running on total ghetto Kumho Victoracer discards in 205/50-15. Hey... I can't complain @ $10 each. John Starnes mentioned he was going to run really high spring rates on revalved yellows. I was a bit worried about doing this, as Greg @ TC mentioned the yellows wouldn't be able to keep up after about 800. Would stiffening the front even help? According to Scott's calculations the deflection would reduce by a substantial amount. I'm wondering if this is enough to keep a decent contact patch in the rear. I'm tossing around 600/900 in my head, if the yellows will hold.

Oh, and another thing, and this one is really bad, sometimes at the end of a braking zone, as I'm about to turn in, or I'm already turning in, the car hops. This feels like crap, and obviously the car is all sorts of pissed off when it's doing this. Late on sunday I heard a chirp or two from tires. Is it possible that I'm briefly locking up a front? This problem is really quite nasty in the wet. The car hops all over under medium-hard braking. Ideas? Anyone?

Warren, who may actually have to buy new tires next year to keep up

 

Just looking at it as a non-Honda guy, I would try a bit softer spring rates in the year. We SE-R guys generally don't go even over 400 in the back.

What alignment specs do you run? I try and run zero toe in the rear -- toe out will cause my car to behave somewhat like you're describing. Well, maybe not that bad, but I think the toe settings in the rear contributed to me snap-spinning into the turn 3 gravel trap at Summit last year.

 

Warren, I'd go with a less aggressive pad on the rear. My CRX gets very nervous under hard braking with VGX pads on the rear. The 300lb difference in spring rates should be entertaining; can you say World of Outlaws sideways. Take it for what it's worth

 

Warren, I would think that you would want to runner a higher rate in front & adjust the rears from there. I was bottoming out with 475#. (EG civic with a D16=lighter than your car in front) I now run 600# in the front. The chirp & the rear end griping/sliping could be caused by the front bottoming. The chirp you are hearing could be from lifting the inside rear & it coming back down (chirp). = braking a little too late/pushing the front thru too much(see bottoming) ? What is your rear toe at? I don't run toe out in the rear anymore as the car feels too twitchy to me under braking. I keep it @ 0 or 1/16" in. 300# differrence f to r might be a bit much depending on your rear bar size & what you don't like about the car now. As always opinion differ. HTH.

 

I asked for my alignment to be toed in by 1/16" total in the rear. I forgot to pick up the sheet though, so I'm not sure what it's actually set at. I'll have to check this before the next outing.

re: rear pads. It seemed even worse when I used stock pads a while back. I can try the stock ones again, but I think it's just going to be even crazier.

I think I'm going to have to use the Feb. events as test and tune.

Warren

 

I think this is the root of your problem, in that setting the rear toe at 0, and the front at 1/16" seemed to completely solve this situation for me (june last year T1, Summit main vs. a couple months ago w/NASA).

97 R
Bilstein/GC, 300F/500R, Mugen big bar, R4 pads all around.
The switch in alignment (reverse of stock recommendations/specs), was at the suggestion of Ben Schaeffer.
Now I can just stomp on the binders and it stays perfectly straight (even chirp the fronts). Even the Instructor commented on the brakes. He just didn't like that I was looking in the rearview and letting everyone past.

Now about my oversteer ... I need to get that front Mugen bar in (one of these years),
along with those 400# springs onto the front !!


[Modified by zygspeed, 2:11 PM 12/11/2001]

 

Warren, I guess I'm in agreement with the other replies. My ITA CRX (met you at the glen in October) uses 500F/700R springs and stock brake pads in the rear. Other CRX's are running even higher spring rates. Some Integra's are running over 1000 # on the rear. I will be going to a slightly more agressive rear pad next year, but still not the same compound as the fronts. You do need a quality race valved shock to handle the high spring rates. I use single adj. race valved K's now but, budget permiting, would like to get double adjustables which would allow me to crank up the rebound rate of the rear shocks to help control dive under braking and keep some weight on the rear wheels. I agree that you might want to play with the alignment settings to see if that helps. Remember, make one change at a time and then test.

I guess you got the engine fixed!

joe

 

Warren,

Longitudinal weight transfer (symetrical) under braking doesn't know about spring rates. Nothing you do to your spring rates is going to change your rear corner weights and hence contact patches under braking. As you might imagine I don't think stiffer front rates will do anything you really want.

Your hopping is possibly some sort of bushing windup/release or damper hysteresis/cavitation on reversal - both could be exascerbated by sloppy footwork on release. Does it feel like a vertical hop, or just a sudden lateral shift?

Remember that the rear has some bumpsteer and a nice side effect of stiff rear springs is that they minimize it.

With stock bushings you may need 1/16 toe in on the rear to keep the rear from feeling busy - I did when I ran Lowdowns.

If you are going fast enough and braking hard enough you are going to be busy under braking, and that's got to do with the tires.

Scott, who just discovered his chassis is twisting and what I thought was a lead brick tumbling around in my spare tire well is actually my Autopower roll bar creaking as it's twisted. Gonna have to check all my nuts and bolts, inspect for cracks in the sheet metal, remove it all, and weld in a full cage, and finally get some peace and quiet in the cockpit......it's always something.....


[Modified by RR98ITR, 6:33 PM 12/11/2001]

 

Enough rebound damping to do that could have such dramatic effects on transient lateral weight transfer as to make the fix worse than the problem. Don't try to fix a possible dynamic alignment problem with shock damping adjustment. Then again if you increase your front spring rates this might be a nice condiment. I think it would be a mess though.

AND IT WON'T KEEP ANY ADDITIONAL WEIGHT ON THE REAR WHEELS - it will transfer the same weight forward that it was going to anyway, and it will actually do it faster. I am neglecting dynamic changes in CG height in saying this. I suppose enough rebound damping and then hammer the brakes and you might temporarily take all the weight off the rear wheels, but that's another subject, possibly even another organized motorsport somewhere.....

Scott, who want's to be emphatic....but friendly.....

 

Scott, it feels like a vertical hop, and it can occur multiple times in the same braking zone, especially in the wet.

It would probably get mad s+y13 points in some circles... The car isn't lowered very much at all. I'm starting to wonder if I'm tagging the bumpstops because my rebound is set too high and the spring rates are too low.

I'll try and get in touch with one of the shock engineers @ TC tomorrow too.

Warren

 

Call OPM as well, they are very knowledgeable about all honda setups...

 

Scott, the reason I was thinking front bottoming was because it happening when turning in (although after rereading the first post that isn't always the case). My thought was that if Warren bottomed the front corner, that wheel would have basically a super, duper, whooper spring rate. The slip angle would go thru the roof. After it slid a bit, suspension travel could return, allowing the car to corner 'normally'. It would then repeat the cycle. What 'cha think?
Warren, how much compression until you hit the bumpstop? Obviously, the front rate you have would be fine if you had enough travel. added in edit-Hmm, after reading your last post, I don't think it is a bottoming problem either.
If you are running super high rates (e.g. 1000# rears), you better have a really good cage. These cars are just not that stiff. Scott's comment about his AP bolt-in tells it all. It is creaking as the car flexs around it.


[Modified by civicrr, 10:56 PM 12/11/2001]

 

Here's my $.02:
- - - My braking style: I brake late and I brake hard.
A) It's not the shocks. I've never had a "hopping" problem as a result of shocks and I've used both revalved shocks and old, used, leaking shocks that have never been revalved (this past weekend) and didn't have a problem.
B) Springs: Not sure, but when I had the stock springs with Konis, I never experienced a hopping sensation.
C) Tires: Possibility...
D) Brakes: I use Blues in front and a good endurance pad in the rear. I DON'T want the blues in the rear. If I were to brake late and do a little turn in, don't want the rearend to come in. Plus trail braking is a big issue.
E) Alignment: Possibility...must people I know that race the ITR have a little toe out at the front and zero toe at the rear.
F) The actual Braking: I believe this is the issue. On the front stretch at VIR I hit the brakes hard as hell at 4 (~135mph). And yes, the rear is VERY VERY light. You just have to keep the steering wheel straight. One time I passed a car on the inside at T1, Under heavy braking, I gave the steering a little input, and the rearend started coming around, let off the brakes, a little steering input and everything was ok. I've had people tell me under very heavy braking, they see one of the rear tires (right) off the ground and about 1" patch of the other rear tire (left) on the ground. The ITR just has AWESOME front brakes...big rotor, big pad, great ABS, 60%+ of the weight is at the front of the car when the car is stationary, now add the best pad, fresh, good brake fluid... Better yet...get on a bike, get going pretty good and hit the front brakes.

I'll ask around, but my money is on (F) the Actual Braking.... Good luck finding the problem. Granted I could be 100% wrong, but it's just my opinion...

JON - who thinks "www.bussetech.com" and "Cobra" has some great pictures...

 

By the way, my spring rates 800lbs front, 1000lbs rear.

 

Mike,

I don't think you could get the hopping phenomenon we are talking about with so little detail from cyclic bottoming at the transitition from braking to turning either - and here I'm assuming this is happening at the front. When I've bottomed (and stayed bottomed) I've gotten severe push that didn't let up when I got off the bottom (I attributed this to tires being very hot by that point).

I'm pretty stumped. My only experiences that sound similar are being into the ABS (presumed to be of much lower magnitude and not to be mistaken by Warren), and 2nd gear acceleration in a rough corner during which I got massive front end shake that was a natural frequency phenomenon induced by some combination of spring rates, bushings, tires, and the specific spacing of the bumps.

Scott, who's interested to hear what TC or other paid professionals think.....

 

TC is stumped. They also advised me not to go over my current spring rates The guy that actually revalved my shocks thinks that they will overheat w/ 600/900. Jon, who did you speak to at TC about your Konis? I'm considering going against their advice. Hell, you tried 800/1000 on off the shelf-ers.

Gonna be busy figuring this one out.

Warren

 

Although not directly relevant, I had a similar hopping problem on my stock suspensioned ITR under hard braking. The front wheels would momentarily lock and slide, ABS would then disengage and I would get control back. After swapping in a fresh set of OEM struts, the problem vanished.

Given that, I'd be inclined to dyno the struts the struts (re-valve as necessary) and verify the rear toe alignments then start looking elsewhere if it doesn't solve the problem.