Knockback and leak advice needed

[wmhjr]

Guys, I've read a number of threads concerning knockback but I think I need a little more clarity if possible.

Here's the setup. Moser 12 bolt rear end, "new style Ford Torino" axle flanges and sealed ball bearings. 33 spline axles, Truetrack, Wilwood 12.2" 4 piston Dynalites in the rear. I have two different but possibly related issues.

I'm getting knockback - seriously - especially on autox. At Heidts this past weekend, on that last hard right (almost 180deg) turn, I have about zero brakes going into the turn unless I pump twice. If I don't put side loading on the car, brakes are perfect. BTW, I'm running 14" Superlite 6Rs up front. I also have some gear lube leaking out the axle flanges.

Here's what I've done. I've replaced the axle seals - several times, including in the parking lot of the host hotel at Heidts. I've replaced the "old" type Wilwood bearing retainer bracket with the "new" one that puts more peload (frankly, there was zero before) on the bearing.

I've talked to both Moser and Wilwood. Moser seems to think a tapered bearing might do better but cannot promise it will eliminate the knockback. They think the outer seal on the tapered bearing "might" do better in the leak area, and are pointing to a failed ball bearing as the cuplrit for the leaks? As if the inner seal has no purpose? They claim that Strange and others don't even use an inner seal. I'm a little skeptical. Moving to a tapered bearing means replacing my axles, which isn't cheap though if that is what it takes to fix it, I'll do it. Just don't want to spend the money on axles and tapered bearings only to end up with the exact same issues.

I'm thinking maybe size a shim for inside the housing for the bearing (either tapered or ball bearing) to get the bearing more outboard and allow significant more preload? And maybe add some reinforcement on the bearing retainer so it can't flex? Honestly, the parking brake is useless for me so I could even just totally eliminate it. Not sure.

I frankly don't understand why Moser would pretty much ignore the inner seal leaking.

Anyway, I'd love to hear some more ideas or thoughts about where my head is at.

[Bow Tie 67]

Bill,

I'm running the tapered bearings on my Moser 9", ( Timken set20 ) I consider them a must for the side loading you experience on the track. They will not cure your knock back but should help it out. They have no inner seal and with the movement from side-loading will cause the outer seal to leak at some point. I now consider the rear axle bearings to be a wear item with the type of abuse they are exposed to. My driver side has been replaced twice in 9k miles, unfortunately the bearing gets damaged when removed to replace the seal so it ends up getting a new bearing assy.

Here is a link to what the set20 bearing assy and locking collar look like.

https://catalog.foothilloffroad.com/...id=nrlzpdwpknp

P.S. Sorry I bolted without saying goodby but I had to get home early.

[silver69camaro]

Definetly a tapered bearing! It should help quite a bit along with a thick (1/4") retainer plate. Depending on your amount of grip it should eliminate most of the knockback (to where the brakes are still functional, just more pedal travel).



The seal on the Set 20 bearings works pretty well. I've never had one leak.

By the way, what is your wheel width and backspace? This plays a big role in knockback.

[wmhjr]

Matt, no worries about leaving. My dad said you stopped by when you were leaving, but I was out thrashing the pontiac on the speed stop. I think you left most of a case of power-aid, which my son has already confiscated! BTW, nice job on the overall event. Once again you and the car are impressive out on the track. Had we not both been in group B, I would have tried to get you in my car and vice versa.

Thanks for the info about the set20 bearing assembly. When you say it did not cure your knock back but helped, I'm curious how much of an improvement you thought it was.

I'm also curious how this would install. when I talked to Moser, they said I'd need to change to different axles to go with the tapered bearing. There would be press ring that goes inside the housing first, then the race, then the bearing/seal which is pressed on the axle, right? And the preload is still accomplished by the same bearing retainer provided by wilwood?

[wmhjr]

Definetly a tapered bearing! It should help quite a bit along with a thick (1/4") retainer plate. Depending on your amount of grip it should eliminate most of the knockback (to where the brakes are still functional, just more pedal travel).

The seal on the Set 20 bearings works pretty well. I've never had one leak.

By the way, what is your wheel width and backspace? This plays a big role in knockback.

Matt, thanks. My wheels are 18x10", 6.125" BS. I actually thought that the wheel geometry was pretty mild and should not hurt as far as knockback. It actually doesn't really matter much, as I don't have flexibility to adjust that (unfortunately).

Oh, Also I'm thinking about making a set of 1/4" retainers myself. I may use the Wilwood retainer with the lip pointing toward the center, then put the 1/4" or 3/8" thick ones outside of that? Thoughts? I just don't know if I need that "lip" if I go to a tapered bearing. Does the bearing surface protrude from the housingi or is the lip still required for preload? Or should I just think about adding a thin machined shim inside the housing to place the outside of the axle where I want it?

[wmhjr]

BTW, do only "Matts" answer this thread?

[parsonsj]

Those ball bearings have got to go. You need to get to a tapered bearing (the Set20); it's got to be the biggest contribution to knockback on your setup.

Having said that, chances are you'll still have some, but you may find it livable. If you do decide to tackle an axle swap, ask Moser about their Hobby Stock axles. They will give you the best chance of the most reduction in knockback.

[Bow Tie 67]

Bill I'm running floating calipers so I dont have knock-back issues. Todd Akes ? Vegas69 on Lat-g has dealt with Knock-back extensively, do a search over there. The housing end is different for the Set20 setup, I'll try and find picks of mine. The installation of the set20 on the axle is seal then bearing the press on retainer collar. Removal is split collar and then press axle out of bearing, which is why the seal is destroyed.

Matt Jones I'm curious what is the rear end setup on your car? Do you seal the outer section of the set20 with rtv? I cant believe you have no seepage and track the car.

[silver69camaro]

A 10" rim with 6.125" B.S. is pretty good for minimizing leverage on the bearing. With that in mind, I'm with J.P. that the ball bearing is probably your biggest contributor.

For the retainer, you need to have that lip in place to compress the seal correctly. Currie has a 1/4" replacement for Wilwood brakes, although it's a full-circle retainer and you'd have to pull your bearings off (which I guess you're doing that anyway). That might be your best bet. I made mine as a full circle design, but it's a interlocking 2-piece so I can remove it when I need to.

See here for the retainer plate:
http://www.currieenterprises.com/ces...E.aspx?id=3267

Matt, my axle is a Ford 9" made here with Torino style ends. I've never had any seepage with mine, and I know Art hasn't had any either on both of his rigs. We make our own housing ends (forgings and all), so that might have something to do with it. Nothing wrong with smearing some RTV in there, though.

[Bow Tie 67]

My retainers dont compress the lip, they actually have a step in them. Matt do you have the dimension from bearing seat to outer housing end where the retainer mounts? I was always worried about flipping the retainer and putting to much pre-load on the bearing. When the bearing is new and the outer seal has not seen the track I have .015 to .020 end play. After track time is will slowly increase depending how many track days I complete.

[wmhjr]

Matt, I've thought about floaters in the back, but am not aware of a relatively cost effective and non-destructive option. I'm concerned that I'm very happy with braking except for the knockback and don't want to trade one problem for another. I don't believe Wilwood has a solution for me, but I'm going to talk to those guys again.

I'm a little confused about the set20, as it's an option over on the Wilwood site for the Torino ends. I guess among other things I need to get some more details as to what they think about my different options.

Matt (Jones), thanks for the Currie plate link. I think I saw you post that in the other knock back thread. I almost posted this here but also wanted to bring up the seal leak issue, which is why I started the new thread. The only issue with the full circle retainer is that my understanding is that I'll need to replace my axles, and could have them shipped from Moser with bearings pressed on. They're probably not going to be too crazy about sticking a set of Currie plates on there first. I could just order them without the bearings pressed on and do it separately. One thing I'll need to figure out if I press them myself is exactly what depth they need pressed to, right? I want to make sure I do NOT mess with my track width.

[wmhjr]

BTW, between Matt sqaured and John, you guys have convinced me to move to a tapered bearing. Isn't it wonderful how people here can help spend money!

[Larry Callahan]

Wilwood solved mine with a floating caliper. The caliper is now for sale but supposedly MotiV8r has the only prototype production bracket. So far it works awesome!

[wmhjr]

I have a call in to Mike Hamrick at Wilwood to discuss this. Hopefully I'll hear back before long.

[silver69camaro]

My retainers dont compress the lip, they actually have a step in them. Matt do you have the dimension from bearing seat to outer housing end where the retainer mounts? I was always worried about flipping the retainer and putting to much pre-load on the bearing. When the bearing is new and the outer seal has not seen the track I have .015 to .020 end play. After track time is will slowly increase depending how many track days I complete.

You need to have the retainer's lip towards the seal/bearing, and there should be zero end play. Don't worry about putting too much preload on that bearing, more is better. From inside bearing seat surface to the outer housing end face is 0.675" for most housing ends.

Also, you shouldn't need to axles with the Currie retainer. Just press off your old bearings, slide the retainer over the shaft (lip side in!), and press the new bearings on. Do your current axles have stops machined on the shaft for the bearings? Most will have a positive stop so you can't screw it up.

[Ron S]

I have the same issue with my Mustang. In fact it is so bad that as soon as I come out of the turns on the the road courses I have to set the brakes so that the next turn won't be so scary. Its funny you kind of get used to it, but the first couple times at over 100 mph you almost sh*t yourself.

I've tried everything to tighten them up, the tapered bearings don't help much and require different housing ends. A floater is the only real answer. I really hate 9" rears, I am doing a Dana 60 floater for the AMX I'm building, for now I'm just going to live with the problem in my Mustang. Ron

[Van B]

No thread hijack intended here but this thread got me thinking. I had a fab guy I know install my 4 link last year and he also built a 9" housing for me. I have also experienced seal leakage (see thread link below) and brake knockback. This morning when reading this I started thinking about a residual pressure valve, but now I am thinking I have something bigger I have to fix. You can see by the pictures that the caliper mounting bracket holds the axle and seal in the housing but the spacers on the t bolts trouble me and make me think that the axle may have a lot of play and causing the knockback.

Share your thoughts and maybe we all can learn from it.

https://www.pro-touring.com/showthre...eal&highlight=

[Vegas69]

I've went around the world on this deal.

Moser 12 bolt, big ford ends, 33 spline, true trac, roller bearing(to start), 7/8 manual, 13" sl4 calipers, original wilwood plates=Knock back was unbearable and pump brakes city.

1. I found that the Wilwood bearing plate had approx. .010-.020 free play between the bearing and plate. Called Wilwood and Moser and told them to take their head out of there you know what..... I am the reason Wilwood made the new plate way back when.
2. OK, found out Currie made a full circumfrance thick plate and installed. Made very little differernce.
3. Switched to tapered bearings, cut it down by approx. 40%.
4. Put in a 2 psi residual valve, didn't do a damn thing but cost me 20 bucks.
5. Changed to a 1" bore master cylinder. Helped again and cut it by another 20-25%.
6. Shimmed the inside of the bearing races to tighten up the bearings. Didn't notice any difference but I only added .020 in fear of to much preload.
7. Lived with it for a long while but the bearings began loosening up and the knockback gradually got worse.

Like Larry, I also adapted Wilwoods brand new GM floating metric caliper to an internal parking brake set up with a top secret bracket NOT made by Wilwood. I had to go to the 12.2x.81 rotor to make this happen. Brake knockback is 100% gone on the street and still a hint in autocross. Brakes are by far the best they have ever been on the track. Here's the deal, I overheated my front brakes at Pomona two weekends ago running 8 or so speed stops in a row. You don't need these massive rear brakes on a pro touring car. Look at a C6 corvette of C5 Z06 for a moment. There is a reason 98% of factory cars come with floating calipers on the rear axle. hmmmmmmmmm

I also want to say Dustin Burr at Wilwood really helped me out and really helped make the Metric caliper a reality. I don't blame Wilwood for my problem, I made an engineering mistake by using a part in the wrong application.

I will say that my big wheel lip has likely made mine worse along with r888's and I've got my car working pretty decent. Bottom line for me, I'll NEVER build another car with a fixed caliper out back without a floating axle or caliper. I'll also never build another car without a real Ford 9". I think the whole 12 bolt with 9" ends plays into the deal in some instances from all the guys I've talked to over the years. End of story.........

[rsk68]

Only real fix is floating axles or calipers, floating calipers are limited to one or two pistons and is my temporary fix for now, I will be going floating axles in the future.

[wmhjr]

So I talked to Mike at Wilwood last night. Here is my current plan at a high level.

First, I'm moving to tapered bearings, and while I'm at it I'm planning to use the Currie full circumference retainer. It's 1/4" and all the way around so it should make the axle retention as good as it can be. I'll also measure the runout and if necessarly, shim the assembly so that I can get a good amount of preload. Hopefully these steps will eliminate the leaking, and stabilize the movement as much as possible. I'm not sure yet as to the details of swapping the sealed bearing for the tapered bearing, as Moser indicated yesterday that my existing axles as is cannot handle the tapered bearing. I'll find out more details on that.

As for brakes, I'm going to try the wilwood floaters in the back after getting the input from you guys and talking to Mike at Wilwood. There are two piston sizes and I'm planning on using the larger one as currently my prop valve (bias) is wide open with my 14" SL6s up front, 12.2" Dynalites in back, and a 7/8" master. Mike indicated that he would get back to me about bracket timing but thinks we can make this work pretty quick.

Currently I'm like Ron. At Gingerman I was REAL surprised the first time I came accelerating out of a turn and hit my brakes at 100mph+. Good thing we had familiarization laps. At Autobahn, it was a litte better, probably because I swapped the old "thinner" retainers which provided zero bearing preload for the newer ones (on Friday night at the host hotel parking lot)

The real problem was the Autox. At motor state, let's just say that the finish line was always interesting for me. The roadster shop should probably have moved their rig..... At Heidts, it was kind of a good news, bad news thing. The bad news was that there was so much more dramatic left/right stress that I virtually had no brakes most of the time. The good news was that since I never got out of 1st gear (as opposed to starting and staying in 2nd at motor state) that I could mainly use the throttle - EXCEPT for that one last hard right turn before the smoking left hander to the finish.

I really appreciate the advice here, guys. This is a good topic. I'm probably the poster child for this issue, as I have a long, heavy, live rear axle big body car being thrown around on an Autocross, and I have a lot of torque to the ground. If I can get this improved sufficiently then it ought to work for anybody.