Pad Knockback

[Elvenhome21]

Wheel bearing won't last over 100k in a race car. Or 50k or 20k. Maybe in your grandma's FIAT, but not in a race car. As Elven mentions you're going to see some flex in the stock suspension. This is compounded if you have worn bearings, improperly torqued axle nuts, stock brakes, etc... There have also been instances of hub failure in the 2g cars that see open track use. I'd replace them every season on a race car. I replace them every two years, along with the wheel bearings on my track car.

Use a torque wrench on the axle nuts and torque them to spec. I can't remember the torque spec offhand but it's ungodly high. I can tell you that my impact gun only got them to about 120. Which, when corrected, got rid of 90% of my knockback issues with no other changes to the front suspension.

I'd suggest going through the front suspension with new components and proper torques before going the route of the residual valves. They're a a great solution, but only after all the other variables are eliminated.

I was looking over my video tape from the spring fbody event at RA and noticed that your rear tires particularly the inside tire are locking up going into 12 and 14.

 

[schemauer]

Thanks - yes, I've played with the adjustable bias for some time and just have come to accept the lockup on some corners. The car will actually lift the inside rear wheel in some corners. The combination of a stiff cage, light car and it being FWD contribute to the problem.

 

[mavisky]

Thanks - yes, I've played with the adjustable bias for some time and just have come to accept the lockup on some corners. The car will actually lift the inside rear wheel in some corners. The combination of a stiff cage, light car and it being FWD contribute to the problem.

If you ever find a way to stop it from doing that while using a decent suspension setup let me know.

You must be logged in to view this image or video.

 

[Elvenhome21]

stiffer rebound on the rear and more compression on the front shocks

 

[schemauer]

I've played with suspension settings a bit, but there just isn't enought weight on the back of the car to get any grip.

 

[mavisky]

stiffer rebound on the rear and more compression on the front shocks

That's what I'm thinking, I'm going to be cranking the rears up as the Koni's are only rebound adjustable.

As for the front, I was thinking about adding a front bar due to the amount of lean I get, but I don't think I'll start there just yet. I may also actually back down the rear bar a notch to see how that helps.

 

[Slow old poop]

Here's what suspension flex can do. This is my right front on the high banks at Iowa Speedway. It was set to -5 deg camber, but the tremendous cornering g-forces stood that mother straight up! Looks like the tire is about to come off the rim at the bottom, too. This is about 125 mph at the top of the 13-deg banking. No wonder we get pad knockback with this kind of flex in the suspension.

 

[schemauer]

Great pic Rich. That tire is screaming for mercy.

I have a pic of the Archer car - I think in turn 5 at Road America where the outside front tire looks straight vertical as well. I normally have about -3.5 deg static camber.

 

[talonTSIDriver]

AWESOME pic!!

 

[Slow old poop]

Great pic Rich. That tire is screaming for mercy..

My buddy Jon, who was riding along at the time, said the Hoosiers were "howling" all the way around the banking. He said he never heard anything like that before, and thought they were going to break loose any second. It wasn't that bad. They were dancing around on the hairy edge, but still sticking pretty good. I never had a problem up there until a car came up from below right in front of me, and took away my "air." I lost whatever dowforce I had, and the wall kicked me out. Now THAT was a wild ride! Sidways at 100+!

The NASCAR boys lap Iowa Speedway at 125 mph all the way around, and we only hit 125 (starting from the infield) by the third turn. With a little aero, it would stick better.

 

[turbosax2]

For those of you using residual pressure valve's, are you using just one for the front brakes or are you using one for the rear brakes too?

 

[Slow old poop]

For those of you using residual pressure valve's, are you using just one for the front brakes or are you using one for the rear brakes too?

We used two: one for the front, one for the rear. I suppose you could get away with only the fronts.

Using two stopped pad knock back -- now it only takes one pump ti get pedal pressure instead of three or four pumps.

 

[turbosax2]

We used two: one for the front, one for the rear. I suppose you could get away with only the fronts.

Using two stopped pad knock back -- now it only takes one pump ti get pedal pressure instead of three or four pumps.

Where did you place them? I read they are supposed to be within 12" of the master cylinder.

 

[Slow old poop]

Where did you place them? I read they are supposed to be within 12" of the master cylinder.

I'm not sure what you call all the components in that snake's nest of plumbing. However, I THINK we put them on the primary and secondary lines coming out of the master cylinder going to the proportioning valve. In any case, it requires deft hands and fingers to snake them in there and tighten 'em down. It's best to do it with the motor out, but we did it with the motor in. (Well, *I* didn't. My big fat hands would never get in there. My fabulous crew did it.) Wish I had photos, but the car is gone.

 

[underradar92]

Mine is about 4 or 6 inches from the m/c, you can see it in the third & fourth pic's in this thread: http://www.dsmtuners.com/forums/road-course-autocross/267262-first-impressions-load-mods.html It's the little blue deal hiding in the mess. I only used one on the front brakes. Installed with the engine in place also, total pain in the arse.

If the routing is left as diagonal, two would be required. Mine is no longer that style.

 

[turbosax2]

Thanks guys.

underradar92, I have a few questions for you. I've been considering getting rid of abs and doing a setup like yours. (I talk about my plans here.) What are the downsides of switching to F/R style? I remember reading the diagonal style is a safety so if the master fails your brakes will still work. Is getting rid of that safety something I should be real worried about? This car will be mostly street driven.

Why don't you need the rpv for the rears when you use F/R split? This picture leads me to believe an rpv should be used for fronts and rears.

 

[Slow old poop]

Mine is about 4 or 6 inches from the m/c, you can see it in the third & fourth pic's in this thread: http://www.dsmtuners.com/forums/road-course-autocross/267262-first-impressions-load-mods.html It's the little blue deal hiding in the mess. I only used one on the front brakes. Installed with the engine in place also, total pain in the arse. If the routing is left as diagonal, two would be required. Mine is no longer that style.

If I had kept my car, one of the winter mods would be to beg and plead with Jim (Underradar) to help me set up a braking system like his, with an adjustable propotioning valve.

Ya know, what we really need around here is a Modification Manual that incoporates all the clever stuff that people like Underadar, Brent the Fabricator, and Mike the Mechanic have come up with to make our cars run so good. I hate to see people re-inventing the wheel all the time when the problem has already been solved by somebody on this forum.

It's hard enough to sort one of these cars without having to puzzle over what's wrong and invent something to fix it. For example, I hope all of you have learned to carry a 5-cent crush washer for the oil pressure sending unit as a spare. If you search on this forum long enough, you'll find the post where I reported the problem, how we couldn't find one in Plymouth, Wisconsin, on a Sunday morning, and lost the whole day--all because of a crummy crush washer.

I'm not sure why I am still posting here. After all, I drive a BMW now. Guess I can't let go.

 

[Slow old poop]

Thanks guys. underradar92, I have a few questions for you. I've been considering getting rid of abs and doing a setup like yours.

I ran a 3000GT VR4 for four years with ABS before buying the Eclipse, which does not have ABS. The first time on the track with the Eclipse, I flat-spotted the front tires. It took quite a few laps for me to learn threshold braking without ABS, and I still locked them up on occasion.

I highly recommend keeping the ABS. What you want to work on is threshold braking at one micro-smidge before the ABS engages--that is maximum braking in anybody's book. Youi can't stop any better than that. The great thing about ABS is that, even if you overcook a little and slam on the binders, the ABS won't flatspot those expensive racing tires.

Keep the ABS. When I had the Eclipse, I kept looking for some way to add it back on.

Besides, I bet a manual proportioning valve would work with ABS. Jim can probably figure it out.

 

[underradar92]

Thanks guys.

underradar92, I have a few questions for you. I've been considering getting rid of abs and doing a setup like yours. (I talk about my plans here.) What are the downsides of switching to F/R style? I remember reading the diagonal style is a safety so if the master fails your brakes will still work. Is getting rid of that safety something I should be real worried about? This car will be mostly street driven.

Why don't you need the rpv for the rears when you use F/R split? This picture leads me to believe an rpv should be used for fronts and rears.

The difference in the split, safety wise is that if you loose pressure in one half of the system, diagonal split leaves one front and one rear operational, while mine goes one end or the other. Older cars were set up f/r, I don't know which is more common on newer cars.

Maybe there should be an RPV for the rears also, but I'm not going through that again, it works just fine as is. Most vehicles don't have one at all, I'll be ok with only one.

Ya know, what we really need around here is a Modification Manual that incoporates all the clever stuff that people like Underadar, Brent the Fabricator, and Mike the Mechanic have come up with to make our cars run so good. I hate to see people re-inventing the wheel all the time when the problem has already been solved by somebody on this forum.

I hope all of you have learned to carry a 5-cent crush washer for the oil pressure sending unit as a spare. If you search on this forum long enough, you'll find the post where I reported the problem, how we couldn't find one in Plymouth, Wisconsin, on a Sunday morning, and lost the whole day--all because of a crummy crush washer.

I'm not sure why I am still posting here. After all, I drive a BMW now. Guess I can't let go.

There is a tech article section, but my typing speed (or lack thereof) would make writing an article into an all day thing for me.

I remember the compression fitting ferrule incident, that was ridiculous that, that item was nowhere to be found. Yet another nail in the DSM coffin for the Poopster.

We do appreciate the fact that you still post, it's very helpful.

 

[underradar92]

Keep the ABS. When I had the Eclipse, I kept looking for some way to add it back on.

Besides, I bet a manual proportioning valve would work with ABS. Jim can probably figure it out.

Unfortunately, my ABS worked like crap. 1g ABS is 2 channel/diagonal and therefore terrible. If you locked both front wheels, all four go anti-stop. Not a fun time. I believe 3000/Stealth ABS is a 4 channel deal.

Using 2 valves is do-able in a non ABS diagonal setup. I wouldn't do it on a 2 channel ABS deal though. It may work ok, but it'd still be a crappy diagonal ABS.

 

[turbosax2]

I ran a 3000GT VR4 for four years with ABS before buying the Eclipse, which does not have ABS. The first time on the track with the Eclipse, I flat-spotted the front tires. It took quite a few laps for me to learn threshold braking without ABS, and I still locked them up on occasion.

I highly recommend keeping the ABS. What you want to work on is threshold braking at one micro-smidge before the ABS engages--that is maximum braking in anybody's book. Youi can't stop any better than that. The great thing about ABS is that, even if you overcook a little and slam on the binders, the ABS won't flatspot those expensive racing tires.

Keep the ABS. When I had the Eclipse, I kept looking for some way to add it back on.

Besides, I bet a manual proportioning valve would work with ABS. Jim can probably figure it out.

This is the kind of opinions I want to hear from you racers. I have never raced but I really want to, so for now I have to rely on the experienced guys to share their thoughts.

You have the same opinion as DG and this is basically the only thing keeping me from ripping it all out. Would you still say keep it if I wasn't using racing tires?

The adjustable proportioning valve was only going to be used if I eliminate abs. I'm only considering eliminating abs now because I will have the motor out so the process will be easier.

 

[underradar92]

Eric, do 2g's have a faster 4 channel ABS deal? If so, adding 2 prop. valves in line to the rear brakes might be to your advantage. That way, lowering, different brake kits, mis-matched pads and all that stuff can be compensated for, that's mostly why I did it.

That & because the slow-arsed 2 channel ABS is trash.

 

[Slow old poop]

Would you still say keep it if I wasn't using racing tires?
.

Yes, if the 2G ABS is better than the 1G. ABS is one of the few modern technology gadgets that really works on a race track. Besides, you can flatspot a street tire more easily than a sticky race tire, and then they are history.

 

[underradar92]

Yes, if the 2G ABS is better than the 1G. ABS is one of the few modern technology gadgets that really works on a race track. Besides, you can flatspot a street tire more easily than a sticky race tire, and then they are history.

Yeah, my not quite R-compound tires have a few very slight flatties on them. Oh well, it's better than the car having flat spots from the wall.

 

[turbosax2]

Eric, do 2g's have a faster 4 channel ABS deal? If so, adding 2 prop. valves in line to the rear brakes might be to your advantage. That way, lowering, different brake kits, mis-matched pads and all that stuff can be compensated for, that's mostly why I did it.

That & because the slow-arsed 2 channel ABS is trash.

I have no idea how the abs is configured.

The only reason I was considering using the proportioning valves is because of the abs elimination. I figure I might as well do the brake lines once instead of putting in a non-abs prop valve first, then changing over to an apv once I lower the car. If I decide to keep the abs I will just keep it all stock for now.