So what exactly causes my rear wheels to "hop" as opposed to spin out?? It's one of those things I have noticed that happens anytime I would really get on it from anywhere below, say 30mph.

Just messing around I have tried burning out from a stop but the closest I really get is to have my back wheels hop (feels like they are actually coming off the ground a bit, with the rear of the car shaking and vibrating). It almost reminds me of jumping a pool ball tournament style (where you have to pull the ball off the felt by applying insane topspin) except the weight pulls the wheels back to the ground.


Anybody know what could be causing this? Is it something to do with the suspension, or am I just a really bad driver??

Thanks

 

well driving could have something to do with it, lol. but my guess is you have fairly new tires and the surface you are trying to spin on is allowing for good traction.

 

a number of components cause rear wheel hop.

the two primary offenders are:

#1 the big soft rubber bushings that hold the differential. these should be replaced by poly bushings.

if you need convincing place a floor jack under the diff case and start jacking. the case will rise an inch or so before the car starts rising.

#2 is the big rubber bushing at the front of the lower longitudunal link. any deflection in this bushing and your wheels toe in and out.

pure evil. replace w poly bushing or rod end.

#3 PPF flex. if you put enough power down w the PPF you will break your diff case. buy Banzai Racings new PPF support.

#4 suspension settings and tire pressure.

fix the above and say goodby to wheel hop.

howard coleman

 

Thanks Howard, good info!

Sounds mildly expensive to fix, though definitely necessary =\

 

The brace you mention still does not address the power transfer from the front of the nose to the rear of the diff, the pinion will still want to climb and still break the case....the PFsupercars brace prevents this, which is similiar in design to Ari's and Dans, and yes i know people have been asking about this craddle, its been so busy at the shop there hasnt been much time to get the production under way, but as soon as it does I will inform everyone

 

Actually our brace does address the issue, by limiting the verticle movement of the front of the diff housing, it greatly reduces the chance of failure. Wanklin created a very nice diagram here is is:

 

Your brace still attaches to the same point as the other style diff braces, so its anchor point is still holding it at the front of the diff...actually, i feel it may have increased the chance of breaking the diff case, right where your arc in your pic is, is where mine broke and will still break with yours...and we both had the same attaching points...I had the same brace on my diff and I still broke the case in half....ask Dan (jigsawrx7) about your attaching point, he will agree, it still will break, as he found out using a similair brace that he made like yours. yes, your brace like the other will prevent wheel hop, and help reduce that, but it still will break the diff case imo. You have to transfer all the power complete from front to rear of some sort of bracing...still like the one Ari, Ray, Peter, Adam S. use...and we are talking cars with over 650 whp, not your typical street crusier. Anyway, they look nice, good luck with them. ErnieT and me are going to be using the PFsupercars braces, if that gives anyone any idea's since both our cars are over 600 whp

 

You are acting like there aren't any mounts at the rear of the diff casing. Our brace eliminates the arc from happening. The KG brace allows the nose to climb and pop back. To state that our brace would increase the chance of breakage is ridiculous. It is pretty simple mathematics to see that the pinion movement is greatly reduced with our brace, the only way it would climb the ring gear would be if the bearings were shot in the diff housing.

 

https://www.rx7club.com/showthread.p...ight=wheel+hop

Particularly read DamonB's posts.

Dave

 

Granted the possibility is still there, but you would have to be generating enough power to either destroy our brace, or bend all the legs

 

There are diff mounts in the rear, and people who run stock ones still have a Decent amount of play, not everyone has or wants the resonations from solid composite plastic, nylon, derlin, etc...Thats my whole point, like I stated in above post...those of us who are making over 600 whp and the torque to go along with it,...and even with the pfsupercars brace...you would break the PPF before you break the diff case, which is what I would rather happen, now if you could somehow adapt both the braces together, you would eliminate the PPF breaking and diff case breaking. I am not trying to sway anyone from buying it as it looks to work better for wheel hop reduction then the older style braces, but...just saying it can still break the case with that design. And by me saying it may have increased the reason why my diff case broke in half, was because the pinion wanted to climb and now I had even more resistance with the kg style brace in place, it had even less play to absorb the movement and may have caused it to snap quicker. It depends on the power you are making...let me test your brace alone on my car and launch it off the 2 step and dump the clutch with slicks and see if my case holds together, we can do a back to back testing with yours and the pfsupercars brace. Better yet, let ErnieT test it on his as well, we can both go to the track together since we are local to each other. Peter knew what he was doing and did research and real world testing, and I am sure he would have made a similiar design to yours for this specific reason if it had worked, and again, dan Schecther has made and tried a similiar brace with the same mouting points as yours and STILL broke diffs, like I said, all the guys who are making big power are or were running the same design as peter's.
Any btw, let me talk with Rob (wanklin) and show him the difference in setups.

 

I am currently traveling (checking email from internet cafes) so I cant get into great detail here. A ridgid front mount decreases the likelyhood of casing failure by transferring some of the pivot energy from the pinion to the chassis and by decreasing the abrubtness (think wheel hop) of the pinions motion. I do agree however that the front of the casing will still attempt to climb with the pinion and create pressure points in the casing that are not entirely eleviated by a frontal mount. I also believe that the PPF config only makes this problem worse by putting in the casing in a stressed state through a transfer of torsional energy into the casing. I agree with Greg that it would be interesting to test the various setups to establish failure threshholds.

 

Ok, who would like to sacrifice multiple differential housing to establish a baseline?

Blitzed- you are NOT the only high powered car on this forum or the road, and PFS is NOT the only shop that does testing.

I personally have a 500+ HP car, and have been testing this design of brace for 3 years. I have yet to break my casing with the brace installed. I do not however run drag tires and I don't get to the track much since we moved the shop. We used to 10 minutes from the track now we are 2 hours.

 

Peter, Ray, Dan, me and Ari already have and have PROVEN that their style braces work, where they have made ones like you are trying to sell and have broken cases.

Excuse me sir, where did I say I was the only one with a high hp street RX7? I also did NOT say that PFSupercars was the only shop that did testing, I merely stated that Peter was doing this research and racing developement before you probably even had a third gen. and knew what worked and didnt.

I am glad that you also have a 500+ hp RX7, care to share the dyno sheets with the analog data, I always like seeing the power curves, and I think its great to see the numbers being put down.

Again, since you dont have any real long term drag strip testing as you admitted and dont use tires that hook.... we are talking about two different environments....street on street tires that will spin vs. track and tires that hook. You really cannot compare the two, so if you are testing the brace on your street car, then its not taking the abuse that a seat time car at the strip will have seen. I was going to ask, what is your best 60 ft time with your brace...peter was cutting 1.3xx 60 ft times running 9's and never broke a case with his style brace, dan has cut 1.3xx 60 ft times and was breaking cases until he switched to that style as well. Same with Ray Wilson....

Again, I never said it was NOT a good product...I just said it still doesnt address the breaking of the cases in high hp cars, esp. drag racing. So please stop trying to turn this into a pissing contest....let people make up their own minds with given experience, not hear say.

Good luck and nice chatting with you.

 

Hey Rob,

I will have to take a pic of the brace and show you what I am talking about.
basically its like a craddle that hooks to the front diff studs, and travels all the way to the rear of the diff, held in by the diff cover bolts at the back...and it encases the bottom half the diff. Peter made a top half that actually encases the whole diff, but Ray only used the bottom half when he was drag racing. The craddle piece mounts to the studs on the front of the diff nose, then the PPF hooks on the outer part of the craddle. So now, when the power is transferred, instead of it being trasferred to the nose and want it to rise, it is transferred all the way down the craddle to the back of the diff, thus forcing the whole diff to have to rise as the craddle takes the full length of the energy, and not just a point at the front. This also eliminates the torsional energy being transmitted into the diff casting/case and only to the craddle itself. Thats why I said it would break the PPF first before it breaks the diff case, AND...I would rather have a broken PPF then a broken diff case, ruined ring and pinion, and have to go through and setup everything in the rear again (back lash, carrier bearing preload, breakaway torque, pinon depth, tooth wear etc..)
I would imagine a cryoed PPF or mazdaspeed PPF would help, or somehow integrating both braces so that it would help with the elimination of the diff wanting to rise and when it still does, it WONT break the case because the energy is being transferrered the whole length of the diff forcing the whole thing to have to rise, and not breaking off at the nose/middle where they always break, and like mine did

-Greg

 

How about eliminating the PPF all together??? If the twisting force from the engine is being transfered to the diff through the PPF, wouldn't it be logical to remove it all together? Then all you have to do is support the front of the diff properly, a new pinion mount? I have a solution for this; I haven't tested it with a rotary but with an LSX motor making 420rwhp and 390rwtq. Definately not the same power as your making but good enough to prove it works.

 

Sweet, Thanks for that info Greg. I may be completely wrong here, but I think it is working a little differently than you are describing. The nose of the differential is following the pinions semi circular travel up and back over the ring (pink arrow) while it is also attempting to pivot in an arc wich originates at the front mount (marked red in my diagram). The combination of this pivoting and pushing/pulling creates pressure points (green) on the top and bottom of the diff; one side is getting stretched while the other side is getting compressed. I believe that the brace that you are describing helps by creating a beefy connection between the front and rear end of the differential which soakes up the pressure that could otherwise target the middle sections of the differential by adding to its net structural fortidude, not by tranferring all of the pinions forces to the rear. Simply put, I think the brace just makes it a bitch to break the casing because the you,d have to stretch the craddle to the point of failure to get there. Either way I think its a sweet idea for high HP drag apps, but I do believe that eliminating wheel hop and PPF torsion are two important steps in this fight. Also if you can build a front mount which impedes frontal rotation and longitudinal/vertical movement then you are infact reducing the efficiency with which the pinion strains the case. When I finally throw on the ProCharger and forged internals I will either get a thicker front casing casted or go with one of these braces, but for now I feel that my current IRS setup is more than adequate.

Rob

 

I agree with you Rob, wheel hop is def. a key point to eliminate, and your IRS should be more then adequate for sure. I cant wait till you get the charger as well
Just wondering, how long have you been in the UK? When are you coming back and are you still going to be near your brothers house?

 

You are the one turning this into a pissing contest stating that the brace will increase the chance of the case breaking.

I do not have to post my HP in my sig for every post, to convince people like you. I also do not have to go around the forums touting my HP to try to justify my existence. I have owned my FD since 2001, but I do not see how that matters. Next you will want a copy of my resume and degree... I see that you are the type of person that has to try to prove you are better than other people with personal attacks.

You can continue to swing from Peter's jock, I personally do not care. PFS is a good shop and they make some nice products, they are NOT however the only shop in the US that developes products for the RX7 based off real world testing. Everyone one of our products is tested for on our own cars and customer's before being released.

BTW This thread was about wheel hop NOT case breakage.

Nice chatting with you as well.

 

If you re-read my post, I was talking about the KG style brace was the reason I thought my case broke even quicker and may have been the cause, I never said that about yours, although I did mention it still attached at the same mounting spot on the diff, which is why it can POSSIBLY still break. You are getting really defensive so you must be the one that is insecure about something. I have not attacked you personally at all, PLEASE show me where I personally attacked you as a person, I have said nothing about your character at ALL, so please stop trying prove your made up hidden agenda.

Now you get mad about me just asking to see your graph...what for, I said in my post it is nice to see big numbers put down, thats all, geez, lighten up buddy.
Where is all this justifying existence crap coming from, you really are taking my posts personally, sorry if you feel you are getting butt hurt over this. You do care or else you wouldnt have mentioned you owned your FD since 2001.

Again, you are going no where trying to stereotype me into this so called category of yours as I have nothing to prove...just mentioning a fact with which Rob agreed with me.

It's OBVIOUS you do care that I continue to talk about this subject and a product that DOES work, that another shop has..funny thing is Peter isnt even in the RX7 business anymore, however, I was giving credit where credit is due. And again, PLEASE show me in this thread where I said PFSupercars was the only shop in the US that tests its products...

To end this saga, and most everyone will see what is going on....you are trying to sell a product, someone called you out on ONE small thing, and you really get butt hurt over it, its called criticism sir, learn to deal with it, and if it helps give people some knowledge, then there is nothing wrong with it. Another note, Ray doesnt even advertise his craddle anywhere, so dont worry about them trying to outsell you or anything like that, lol.

Oh and btw, when you are a customer, NOT a shop owner of a shop car or have a shop car, because of course a shop car is expected to be all that...then of course you would be happy making the kind of power like me, ernieT, kevin have made and likewise with Eric+PDviper for gotham racing, and crispeeds customers, and give the SHOP credit for their tune/build. So what is wrong with crediting a shop for knowing what they are doing with a history of racing...yup, take it easy, and dont take these things so personally, as I have not attacked you as a person, never said your product wasnt good, in fact, I have said it looked like a good product and would help with wheel hop, re-read, all I said was I dont think it address's the diff case breaking under drag racing and high hp with which rob agreed.

And by your own hypocrisy, you actually attacked me in this post by stereotyping me personally etc...so really you made your self look like an ***.

 

No need to get into a pissing contest over this stuff. I know Greg. He's a good guy who would never try to take a **** on you, he was just sharing some insightful info that may help others with over the top power goals. I dont think your brace is doing anything but helping people. I think it has been clearly substantiated that your brace decreases wheel hop and so decreases the likelyhood of diff casing failure by reducing shock and PPF torsion, especially when used in conjunction with higher durometer differential bushings.

With that being said, it also serve as a pivot point for the front of the diff casing (doesn't mean it's more likely to break). Without the brace, the diff nose would rise until it reached the end of the vertical range of motion of the PPF at which point it would whip lash the diff (potentially snapping fingers off of the PPF) amplifying the pressure experienced by the casing. With the brace, the nose is held stationary, but the internal dynamics are still much the same. Now the back of the diff will travel in an arc originating at the axle centers while the front will want to travel in a arc in the opposite direction originating at the front mount (unless the mount is designed to resist rotation). The point to remember once the front mount is in play is that the pinion doesn't have to actually climb for their to be pressure on the casing. To use of the word "climb" is probably even a bit unprecise as it only describes the direction in which forces are being exerted, not necessarily where movement is occurring. In other words the fact that a front mount will hold the casing still does not move does not mean that the pinion is not stressing the casing (unless the mount is designed to impede pivoting - this would require four mounting points).

I just spent a decent amount of money to purchase Paul's IRS setup so believe me when I say that pinion support is worth the expense, but it is important also be pragmatic in formulating our expectations.

Both Banzai and PFS produce quality products which deliver as promised, what more can we ask for?

 

I agree, I was not trying to **** on the product and people can make a decision for themselves. I feel I wont be posting much on these forums. I do have the backing of some moderators and shop owners on this subject and about this thread in my defense, but I do not feel the need to involve them. Any other posts towards me from Banzai racing, will be ignored be it positive or negative. So the best thing is to buy the product and test it out yourself. Then if you have issues, you will have your experience and learn what works and what doesnt. If you want more information on the pfsupercars brace, then your best bet is to call the shop and inquire. I am through trying to give insight and other perspectives on things as all it does is bring negativity. I know from personal experience myself what does and doesnt work and from the knowledge from people who have been there and done that. Good luck to all you guys.

 

No. The axles have nothing to do with fixing the location of the diff on the FD. How could they? The axles have flexible joints at each end! The only things locating the diff case in space are the diff mounts and the ppf.

No. The entire diff will attempt to pivot about an arc whose center is through the eyes of the diff mounts. The torque reaction of the diff case is not through the axles, it's through the diff mounts and the ppf. If the reaction wasn't in the diff mounts none of us would ever have to concern ourselves with the condition or type of diff mount installed...

 

I am so glad you posted Damon, you understand what Peter knew way back then, and also what Ray wilson knew and why he and Peter both ran that style of brace back in 2001-02 when they were both Running 9's in the 1/4. Ray just explained it again to me tonight and makes complete sense why his brace works.

 

I think you have all leap-frogged a very important point. There is another diff failure that happens at much more moderate HP levels. When the stock torsen fails it splits in half , usually taking the case out with it. This happens much more often then the high hp failures, considering there are many more moderate HP cars running around. The stress put on the torsen from wheel hop is what cracks the torsen internals. Hence wheel hop is what we are trying to help reduce with our brace.

I never made any claims that in huge HP drag applications that this brace would eliminate diff failure. It was not even designed with that in mind. Howard answered the original posters question and Blitzed said that the brace would cause the casing to fail. This is incorrect.



Apples and Oranges