Tie down lf and rr

[sidewinder69]

Wouldn't it make sense tie the lf and rr down in slick track conditions, to keep load constant in the left rear while not letting it rise up on the rr so you keep both rear tires loading for better exit traction

[TheJet-09]

I tether the LF and chain the RR. Not saying it helps at all, but I mainly started doing it with the RR to keep it supported while I change springs or bar angles. But, I have heard of those who mess with the "gap" between the top of the RR spring and spring nut, to alter how much the RR can lift off the spring. From what I have heard, some will go to a zero gap on the RR in the slick. I have set mine to around 1/2" and just leave it there.

Somewhat on topic, obviously a bearing chain mount on the LR axle tube is popular, but for those chaining the RR are you using one there as well? I ask because I was flat horrible in the slick this year, and one thing different than previous years (not that I was much better then) was the fact I had a solid (non-bearing) LR chain mount on the rearend this year. But I've always ran a solid one on the RR at the same time. With the LR chain being probably twice as long, if not three times as long as the RR chain, I think a non-bearing mount on the LR can be more forgiving during rearend wrap up based on chain length (relative to the chains "arc"), but conversely not nearly as much on the RR (obviously the RR axle tube wraps up the same amount as the LR).

It's just one of many areas I need to look at, but was curious of what others thought...?

[sidewinder69]

That does make alot of sense. In the slick you are trying to keep movement in the 5th to maintain the traction so it's possible the clamp mount could be working against that movement

[billetbirdcage]

I tether the LF and chain the RR. Not saying it helps at all, but I mainly started doing it with the RR to keep it supported while I change springs or bar angles. But, I have heard of those who mess with the "gap" between the top of the RR spring and spring nut, to alter how much the RR can lift off the spring. From what I have heard, some will go to a zero gap on the RR in the slick. I have set mine to around 1/2" and just leave it there.

Somewhat on topic, obviously a bearing chain mount on the LR axle tube is popular, but for those chaining the RR are you using one there as well? I ask because I was flat horrible in the slick this year, and one thing different than previous years (not that I was much better then) was the fact I had a solid (non-bearing) LR chain mount on the rearend this year. But I've always ran a solid one on the RR at the same time. With the LR chain being probably twice as long, if not three times as long as the RR chain, I think a non-bearing mount on the LR can be more forgiving during rearend wrap up based on chain length (relative to the chains "arc"), but conversely not nearly as much on the RR (obviously the RR axle tube wraps up the same amount as the LR).

It's just one of many areas I need to look at, but was curious of what others thought...?

Just in case you wanted the info:

Take a solid not bearing/rotating chain mount that has the chain hole 1.5" above the axle tube, then rotate it 5.552 degree's which is the amount it would rotate for a 36" long torque arm moving 3.5" of travel. The effect length change on the measured chain drop would be a whopping .01407 of an inch. (Granted this isn't taking into account the angle change of the chain when the rear end moves forward or back which will have some effect - I could figure that if I knew how far the RR actually moved back and had the orignal chain angle - but it's going to be minimal but probably more then the .014 I listed depending on how it's set up)

As you can see it has very little effect on overall drop change.

[TheJet-09]

^^ That's excellent info! Thanks. When I mounted it, I even tried taking into account the mounts rotational index (if that makes any sense), in clocking it so say at half of the 5th coil travel, the mount would be in direct line with the chain.

Possibly a bad job of explaining it on my part, but thanks for putting numbers to my thinking.

[Austin34471]

^^ That's excellent info! Thanks. When I mounted it, I even tried taking into account the mounts rotational index (if that makes any sense), in clocking it so say at half of the 5th coil travel, the mount would be in direct line with the chain.

Possibly a bad job of explaining it on my part, but thanks for putting numbers to my thinking.

If that's how you mounted it, then your problem is not how the chain is mounted to the rearend. The bearing mount for the cage is just Racecar Part MFGs taking advantage of people that don't know how to math

[Kromulous]

LOL i always tell myself that when buying new parts, these companies are in business to sell things, do i really need that or can i just make it?

Anyway, last year we tried tethering up the LF about 1/2 inch from spring disengagement off the cup, and i loved how the car looked on the track, but we had a hard time with the car being loose in. Now looking back, and others have told me, when you do this i think if you limit the RR as well, and then add a stiffer spring you can get the car to firm up and feel better on entry.

I kept the same 225 lb spring, i should of went up to a 275lb maybe. We just took off the limiter on the LF and the car was a lot better, but i wonder overall if that was the right move. We race mainly on slickish conditions thou. Also probably should of added a lot of rebound to the RR shock, i usually have some degree in it, but probably more was needed.

Hindsight, LOL.

[TheJet-09]

I tried a 275# on the RR and it just didn't do what I needed. I also tried that (and about everything else) without moving the J-Bar at all. I just left it a touch below even with the pinion.

What I did end up liking was a bump stop on the RR (Christmas tree type) that I would shim to change the engagement. That actually helped the car most when there was still traction (early and through transition of the track surface). It was a black bump, so maybe it needed to be stiffer for the slick?

[Kromulous]

I have seen guys running traditional coil spring rubbers in the RR and RF, i think that may be a good option to look at. Quick and easy to put on and change.

I think a lot of the key with these new style setups are in the RF. You need the spring rate to be soft initially and get progressively stiffer, at a very fast rate. I have been thinking about cutting up the RF of a spare chassis we have and redoing how the RF shock is mounted, and how the RF upper A frame is mounted to make it wildly progressive, while using a stack.

Currently you do not have enough shock movement to work with, to gain enough progression in a spring set up. My idea may allow me to run a 9 inch shock and a 3 spring set up, but time is always the limiting factor for me. I may just sit here and model it on the computer and talk to someone about it LOL, lazy way i guess.

[Matt49]

I just tried the LF tether for the first time last season. We had a bunch of things very different on the car from the previous year so I wasn't sure what to attribute it to but we fought loose getting in especially as the track got slicker even with our "normal" adjustments for slick. Like we couldn't stay in front of the track changes. So finally on our last night out, we went pretty crazy with the bottom right bar down and really got the car feeling good on entry. That same night, the tether on the LF broke a few laps into the feature and the car switched to so tight getting in that I burned the RR off in just a few laps because of how I had to drive it to get it through the center. So we learned kind of the hard way that tethering the LF can really free up entry just by itself. I knew in theory that it would but I never imagined how drastically.
That being said, we're going to put the tether back on for 2018 because we believe the aero advantage is worth having and then we might just go up on RR spring or lower the entire j-bar to compensate for balance issues it gave us. We've also considered just using spring rubbers in the RR as the track slicks off or potentially using an air bump and shim it according to conditions.

[Kromulous]

Question, how did the car feel coming off after you made the radical change on the RR, while the tether was still on? I would think really good. My brother liked it off, but couldn't get used to entry, said it was like there was nothing connected to the track on RR.

MBR told me to try a 300 lb spring but i never did, we just took off the tether.

[billetbirdcage]

A couple things to keep in mind on a LF tether:

1. It can lessen the sweet spot or make the car less forgiving if you miss a little on a set up.

2. It can cause the car to swing loose/tight very quickly if it tries to lift the LF.

3. Usually more changes are needed then just limiting LF travel.

4. The aero advantage doesn't always overcome the negatives if the track is really slow, just something to keep in mind.

5. Increasing RR spring rate isn't always the answer or the best solution.

As with anything your experience's may vary, and not too many are going to give out a ton of info here but that should point you in the right directions if you think about it. I will say I have never been a fan of limiting the RR for the most part and will rarely do that, but hey right or wrong that's just me.

[billetbirdcage]

That does make alot of sense. In the slick you are trying to keep movement in the 5th to maintain the traction so it's possible the clamp mount could be working against that movement

Before the advent of the bearing chain mount, companies where selling mounts that put the chain in front of the axle so when on the chain it would hold load in the 5th arm. I tested back to back chain on top vs chain ahead of axle, I made a clamp that had a hole at top and 3 holes in front (in 1" increments forward - so the farthest out hole was 4" in front of the axle tube). All was set up in shop with different chains so travel was as close as the same as possible.

Private test: 2 different drivers and not one of them could tell a lick of difference, neither did the stop watch.

[TheJet-09]

Excellent information! I appreciate you sharing. Not relative to this thread, but all things being somehow related...is anyone running a short, straight left mounted panhard bar anymore? Or at least tried it with current type setups? Way back when I loved using that, but haven't had the guts to try one out in the modern era.