JP3

Ok guys. We dont have a dirt track section in thos forum so ill ask you guys. I have a 94 prelude si that i will be racing on a dirt circle track. While testing the car i ran inti a major wheel hop issue on the right front that occurs when powering through and off the corners. My set up is as follows..
Weights
RF 700#
LF 840#
RR 520#
LR 480#

Pressures
RF 30#
LF 25#
RR 45#
LR 40#

3 degrees camber (all that is allowed)

Front is toed in 5/8"
Rear is toed all the way out

Any help at all that could stop the wheel hop will be greatly appriciated.

Xian

Disclaimer: I've only got road course and autox experience so...

You say the problem is with the RF so I guess you run clockwise and it's the inside front that's hopping? I thought most circle track stuff was counter-clockwise, no?

Why all the front toe-in? I get the rear toe out and tire pressure but I don't see what the toe in is getting you here?

Christian, just asked a string of questions and gave no answers...

PS
Do you have the front sway bar still hooked up? I assume the rules require "stock" suspension, bushings, etc...

JP3

We run counter clock wise. All left turns. The toe is set in to help car get set in the corners better and more naturally. No front sway bar so thats not what is causing RF (outside tire) to poad and unload. I must use stock suspension but we can get a little crafty with it. Anything to get rid of this wheel hop

Xian

I'm pretty surprised to hear that the hop is from the outside, loaded tire. You sure that it's not the inside tire? If the outside tire is hopping, you'd have the world's most powerful (and pushy) Prelude... also seems unlikely that the outside tire is spinning/hopping unless you've got a ridiculously aggressive LSD.

JP3

No lsd to my knowledge. We have never had this issue with our other cars. On dirt circles with fwd cars push is always a issue we run into and the setup that we run usually helps curtail it. Yes im sure its the RF doing the hopping. Its a stock h23a1 motor running 205/60/15 yokohoma ice quard ig20 tires as we cant run a race tire and they are the closest ive found to a race tire. Would running a smaller tire help it or hurt it?

JP3

Also i guess it could be bushings. I need to look at all my bushings

Xian

As I said, I've got precisely zero experience on dirt/oval but:

#1- rear toe out will help rotation and reduce the push.
#2 front toe in typically hurts/slows turn-in and reduces the amount of corner entry oversteer you can carry (I've never seen/heard of anyone running large amounts of toe in but, as I said, no dirt/circle experience).
#3- I'm having difficulty seeing how the RF is getting enough power down to spin/hop as the inside wheel should be the one spinning up (unloaded, no LSD).
#4- I'd assume a smaller tire would make things worse as it'd shorten your gearing and make wheelspin more likely?

Given that you're sure that it's your RF tire that's giving you the hop, I'd look at the bushings (as you mention) or possibly what you're feeling is an axle that's on it's way out and not actually wheel hop?

JP3

Didnt think about the axel. I will tear it all apart and inspect bushings. I have spare axels so thats a easy fix if thats the issue. I totally agree that the RF should basically be dead without lsd. Its just perplexing to me as we have never had a issue like this with any other cars. Here is a link to some pics of the car if your curious about what it looks like. https://honda-tech.com/forums/honda-prelude-4/gen4-dirt-track-car-getting-closer-3194309/

Xian

I don't know about the H-series setup but I know the B's can be sensitive to extreme axle angles... and I've got to think your car is seeing that on stock springs/shocks with no front bar. If it's down to axle angle and not a part on the way out, I'd either look at putting the front bar back on or running stiffer/more RF bumpstop. BTW, have you tried running front tow out or zero toe?

Another idea... are you allowed to attach the LF swaybar end to the chassis instead of the suspension? Thinking this would give you additional roll stiffness at the RF without reducing inside traction any further.

JP3

Toe out would make the car favor darting the wrong direction. But you have a good idea with putting the sway bar back on and preloading it. I will look at that too. Im also thinking about shimming the RF radius arm 1/2" which would roll it fwd making the right side of the cars wheelbase a little longer which should help corner rotation.

Xian

Dunno about the "darting" concept... I'm talking about total toe front toe of zero to "slightly" out. As soon as you start turning the wheel, the inside tire is already pointed "deeper" in the corner. This should help turn-in at the expense of some scrubbing down the straights.

Yeah, I've never played with swaybar preload or just attaching it to the suspension on one side and chassis on the other (basically a torsion bar for the RF). Seems like it should work though.

I haven't tried an asymmetric WB setup... honestly never even thought about it. Is there any advantage to be gained by using spacers to increase the track width but on one side only?

Or can you play with corner weight via sliding the front shock tube up/down in the shock fork? Thinking you could lower the RF and raise the LF to de-wedge the car and get it to turn in better?

JP3

We r on the same page with the toe. What im calling you are calling out. Increasing track width would help but not sure how to do it without getting caught in tech. And you are right on the corner weights. Already using spring rubbers but i could space the struts with washers. That would help too. I guess i need to decide if i want the RF to be planted like the LF to stop the hop or if i want to break loose and not bite at all. Physics wont allow it not to bite as we are only making hard left turns. Just kinda lost. Bc if i distribute more weight to the rf ill lose lf bite n push i dunno. Ill go check all the bushings and the axel. And work from there. Maybe try sumn with the sway bar too. You came up with alot of ideas. Ill play with em n see if i can get any of em to help

Xian

Ahhhh... gotcha on the toe. That makes more sense.

On the corner weight thing... does the Prelude have the front strut/shock slide into a fork where it goes over the axle and attaches to the front lower control arm? On the Integra/Civic/CRX, there's enough "give" there to slide the shock tube up or down in the fork and thereby change the ride height at that corner a little bit. If you drop the RF and raise the LF, it may be enough to influence the car's balance in left turns. I played with wedge one time on my ITA car and there was a noticeable difference in how it turned going left vs. right.

The tough thing with spring rubbers is that you can end up with crazy high rates which (I'd think) would be bad for overall grip on dirt. Maybe check out some of the custom bumpstops at either the circle track places or RESuspension.com You can pick a lower, progressive rate foam bumpstop that'll limit total outside travel without making a harsh transition that could cause you to pick up some push.

Regardless, hope some of this helps! I'm interested in hearing how things go with the car.

JP3

Yes the struts are that style. The RF is already seated as low as possible. Ill pull LF and move it up as high as i can. I will also play with that sway bar idea. Also it is possible that my tires are to grippy. They are really soft sticky bastards. I can try running a slicker harder tire on the RF like what i run on the rear. Ill start there and see what happens.

JP3

Also alot of stuff i read on fwd wheel hop says that using solid motor mounts or filling the stock ones with windo-weld helps alot. But that is mostly drag strip guys. Dunno if it will help in this situation

Xian

The biggest cause of wheel hop on these cars is toe oscillation. You mentioned radius rods previously... double check to see if there's play in the big radius rod bushing. Could be the problem...

JP3

Ok. I played with the tires and air pressure some. Didnt have time this evening to do much else. I put 32 RF on a slicker tire and 30 LF on the good traction tire and that smoothed things out some. I still get a little wheel hop but its almost manageable. I will inspect all the bushings tomorrow and hopefully find a bad one. Got a race saturday its non-points so ill just use it to test and try a few things. Hell the issue may completely go away on the race surface. Its alot different than the hard dry dirt ive been feeling it out in.