Desert suspension 101 - Ford Bronco Forum
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post #1 of 28 (permalink) Old 03-22-2009, 12:34 PM Thread Starter
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Desert suspension 101

As you guys know I did not design my suspension. And I did not build it. Thus I find the discussion on how it works very interesting. Below are a couple of threads to follow for tech info. Lots you you guys already know all this, but maybe it is of value for the new guys.

First is the discussion about dual springs at
http://www.race-dezert.com/forum/showthread.php?t=60528
And it explains to someone who never thought about $2 springs$ why is is a good way to go. The extra cost is worthwhile and is common for the Bronco TTB.

Second is all about leaf springs and why it is hard to get tuning correct.
http://www.race-dezert.com/forum/showthread.php?t=55843
This thread has good info and agrees with the fab guys I had help me. The leafs are hard to get correct due to the rate change. The whole time I had my leaf setup I constantly was tightening up my rebound. Even with my C/O setup the rebound had to be tightened to get rid of rear kick in the whoops. The answer for leafs is $bypass$ shocks. More important for the short WB Bronco compared to a long WB pickup.

My observations
-- I was at RM12 at the SCORE unannounced check at SF and right beside where I logged the cars was a deep hole. I was surprise how many 1 & other buggies had inadequate rebound. The result for the guys that did not know about the hole was the vehicles kicked up in the rear almost vertical on their front wheels. Some of the racers had the hole marked and just drove around it. (both Broncos and the FSs went around - lots of room). The fast cars were correctly dialed in and just floated thru the hole. No TTs had any issue and the front runnig 1s had no issue. The fast guys hit the hole and went airborne, but the cars stayed horizontal and they just flopped back on the track with all 4 wheels hitting the ground at the same time. Perfectly dialed in.
-- Its real sad to see a Bronco pre-runner all wadded up due to inadequate rebound. What happens is if one goes to fast in the whoops with low rebound in the big whoops and endo is possible and happens. Two of them in 2008. I did not see any this year.
-- It works in the front as well. Another example is my good friend driving a Jeep TJ. Single coils in front and hardly any rebound with his adjustable Ranchos so as to give the thing a smooth ride. When going up a gentle smooth rock on the trail the front started to bounce. He backed off and tried again with more pedal. I sat there and watched. The first bounce raised the front wheels about 1-2' the second bounce resulted in a back flip and he landed on his roof. The reason for the action was there was so little rebound in the shocks that the springs just threw the thing in the air and over. Extreme example of a bad setup with to little rebound in front. All was fine, nobody hurt, the stock rollover cage was adequate & undamaged and the diy fixup was less than $2k.
Paul
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post #2 of 28 (permalink) Old 03-22-2009, 01:09 PM
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good info. Damping and seperate adjustablility between compression and rebound is critical in suspension systems, and a lot of people don't seem to realize it.
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post #3 of 28 (permalink) Old 03-22-2009, 06:33 PM
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inner stop rings?

I believe that my stop rings arent in the right location.Im pretty new to this stuff and learning alot.I read the Race dezert thread.Thanks.And saw that they had mentioned placing the stop rings(Threaded dealymabobs)about 1 inch above the plastic guide collar between the two springs.Does anybody have any more info about placement for them?Heres two pics that show where mine are at now.It looks pretty obvious I need to move them down,but I will run out of threads before 1 inch.Looks like I have more like 2 inches from plastic collar.Can you just add how many coils you have and there diameter to figure coil bind and put your stop rings just slightly before coil bind?
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post #4 of 28 (permalink) Old 03-22-2009, 06:48 PM
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Good stuff. Thanks for posting this Paul!

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post #5 of 28 (permalink) Old 03-22-2009, 06:50 PM
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Awesome links... thanks for the information Paul

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post #6 of 28 (permalink) Old 03-22-2009, 11:23 PM Thread Starter
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C/O adjustment

Quote:
Originally Posted by yogib View Post
I believe that my stop rings arent in the right location.Im pretty new to this stuff and learning alot.I read the Race dezert thread. Thanks. And saw that they had mentioned placing the stop rings(Threaded dealymabobs)about 1 inch above the plastic guide collar between the two springs.Does anybody have any more info about placement for them? Heres two pics that show where mine are at now. It looks pretty obvious I need to move them down,but I will run out of threads before 1 inch.Looks like I have more like 2 inches from plastic collar.Can you just add how many coils you have and there diameter to figure coil bind and put your stop rings just slightly before coil bind?
===
HMMM, You need to take the tire off and show us a pic of the whole thing from the top of the shock to its lower mount. But the pic has to show us the spring/shock at ride height. Tire off - floor jack to hold the truck up to the normal ride height.
Stop collar placement is controlled by the deflection/stroke where you want the rate to change. You have to dertermine that. But probably you are correct?
Somebody on this forum and help for sure.
I can give it a try since I just did my 72 Bronco. I think I understand it now. Took a couple of trys since I had no help. My 96 was perfect so no adjustment was required, but I changed the coils on the 72 so I had to figure it out.
Paul
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post #7 of 28 (permalink) Old 03-23-2009, 01:05 PM
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Well its sitting on the ground at ride heigth in my pics.I guess I should just give Brett at King a call.
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post #8 of 28 (permalink) Old 03-23-2009, 01:36 PM
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Just got off the phone with Shon at King Tech support. He said they generally dont use the inner collar lock rings on TTB suspensions.Only if your trying to raise ride Heigth.He said there more for A-arm suspension.Sounds good.I guess I can leave them where there at.
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post #9 of 28 (permalink) Old 03-24-2009, 05:16 PM Thread Starter
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rear leafs with bumps?

Just a follow up.
A new post on racedezert advocates hydraulic bumps in the rear. IMO since the springs have such a high rate at full compression then bumps are not necessary. Our Broncos did not use hydraulic bumps. I used the stock rubber bumps. Chris drives much harder and he uses the Nissan voided rubber(poly?) bumps. Neither of us hit so hard that they ever come into play.
My rear C/O set up has hydraulic bumps. Different design.
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post #10 of 28 (permalink) Old 03-24-2009, 11:00 PM
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I have King 2.5" hydraulic bumps all the way around on my Bronco with Deaver 13 leaf race packs and two link in the rear. At a place like San Felipe last week the bumps got a pretty good workout. I was watching closely because I just upgraded from 2.5 to 3.0 4 tube bypasses. The bump stops definitely stop the big hits and although with the shock tuning I am not hitting as hard or as often, I still feel that they are important to have.

I raced for several years in both stock mini and stock full using Deaver race packs and two bypass shocks on each corner on both trucks. In those classes, hydro bumps are not allowed and I can tell you it was a huge disadvantage. I used to replace the blown out rubber stops every race, by the end all that would be left is the plate and bolt. I tried to set up the bypass shocks on the stock full to work as a bump with a ton of compression in the final part of the stroke but it was not nearly as smooth as having the hydro bumps.

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post #11 of 28 (permalink) Old 03-24-2009, 11:16 PM
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Excelent info...stickied...

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post #12 of 28 (permalink) Old 03-25-2009, 12:22 AM
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Quote:
Originally Posted by PWMTN View Post
Chris drives much harder and he uses the Nissan voided rubber(poly?) bumps.

Paul
I believe those are high density foam Paul.

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post #13 of 28 (permalink) Old 03-25-2009, 12:35 AM
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Quote:
Originally Posted by PWMTN View Post
The leafs are hard to get correct due to the rate change. The whole time I had my leaf setup I constantly was tightening up my rebound.
Tight indeed, Paul! They take the big hits nicely, but as you indicated, could use a bit more compression, because the rear has been bottoming occasionally on some of the bigger hits. The F53 pack seems a bit lower rate than the Nationals you were running. I'm thinking of mounting my 2.0 bumps to compensate. I've been experiencing quite a harsh ride above 40mph through a series of whoops. At 60, the ride is quite rough and feels like it's stacking up/rebounding too slow. Passengers are complaining about their necks. Ha! I've got a different valving set-up (big thanks to SteveG) I'm going to try to see how it fits my driving style and Barstow type whoops, which I believe are tighter than what you had this set up for... SF.

Brian

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post #14 of 28 (permalink) Old 03-25-2009, 01:32 AM
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As always Paul, you come to the table with much to offer. Those of you that haven't figured it out already, Paul is gracious enough to pass on years of experience and information that is almost always acquired the hard way.

Funny enough, though, I do disagree on a few things. I guess now that I agree with Bryan about something I have to move on to someone else... Ha!

Quote:
Originally Posted by PWMTN View Post
The whole time I had my leaf setup I constantly was tightening up my rebound. Even with my C/O setup the rebound had to be tightened to get rid of rear kick in the whoops. The answer for leafs is $bypass$ shocks. More important for the short WB Bronco compared to a long WB pickup....

My observations...
I was surprise how many 1 & other buggies had inadequate rebound. The result for the guys that did not know about the hole was the vehicles kicked up in the rear almost vertical on their front wheels.
I find all this very interesting Paul as it is exactly opposite of everything I have learned and practiced when shock tuning. This contradiction is nothing new as I have read a lot of Chris' posts and always thought the same thing when he's discussed shock valving.

I run very little rebound valving in all my shocks. Especially so with shocks mounted on the front of the beam. A friend of mine used to have a Ranger with HUGE (4+" in diameter) external bypass (all for compression) shocks that had no rebound control other than free-bleed holes. His rear wheels would rebound so fast that on a big jump the wheels would fall to full droop, top out the shock and actually bounce into compression once before staying topped out (all while still airborne). If you pay close attention, occasionally you'll see Trophy Trucks do this as well. The Ranger in point was incredibly fast and well-mannered over just about anything you threw it at. I think I have some video of this somewhere. I'll try to dig it up later.

While a bucking rear suspension is a shock or spring tuning problem in general and can happen for A LOT of reasons, I think people focus too much on controlling it by changing the rear valving alone. They figure that the problem is happening in the rear so it must originate in the rear. I was once caught up in this and was driving myself nuts trying to tune the "buck" out of one of my old toys. Until, someone opened my eyes and told me how to valve the front and rear to work TOGETHER! Holy shit did it hit me like freakin' train. I wasn't seeing the forest for the trees!

I thought the front worked great but the rear bucked on any bump over about a foot tall. The truth, I found, was that neither was working anywhere near as well as it could. I had been adding more and more rebound valving to the rear and it worked worse and worse every time I valved it. In the end, the solution was to remove most of the rebound valving in the rear AND the front. The idea was to make the front end push off bumps. Instead of keeping the body flat over big stuff I want the front end to come up, then the rear comes up to match it. The same basic principle applies to landings. The front end pushes up off the landing, the rear does the same then the truck settles to it's in-motion ride-height. Watch some of the Laughlin Leap videos and you'll see what I mean.
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post #15 of 28 (permalink) Old 03-25-2009, 01:35 AM
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Quote:
Originally Posted by yikesbb View Post
I've got a different valving set-up ....
It'll be interesting to see how it feels.
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post #16 of 28 (permalink) Old 03-25-2009, 01:04 PM Thread Starter
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More suspension 101 comments

All, Thanks for your indulgance. As you all know I arrive late in this world after a long life an a serious mountain climber and as an aerospace engineer. The guys if feed from are orders of magnitude smarter, but mostly hands on racers. Thus I solicit all your inputs.

Great to have more inputs. Nothing is better thatn real world info.

- First go look at "Streetable trophy truck Post #35". See a slight error on rebound setting. Thanks Steve, I could not produce any videos and my still camera work is way to slow.
- Bumps do help if your leafs ate more flexy than we were using. This a good deal. IMO, do not and the bumps until the oems or Nissans are being damaged.
- Not sure what a difference is made by the 3" vs the 2.5" leafs. No experience with 3"
- About National or Deaver. Both produce good stuff and use the same metal. Always look at your new springs for minute flaws like scratches or nicks. Spring performance results are based on your input. Often the spring packs need to be tweaked to get the ride height and rate correct for your truck. Its not simple. Lots of leafs for my truck and the others for them to get happy.

More fodder for conflicting comments.
Best regards, Paul
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post #17 of 28 (permalink) Old 03-25-2009, 01:14 PM
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In the interest of consolidating info and posts:

Quote:
Originally Posted by steveG View Post
Very cool! That thing has always needed more damping in the front end. It looks like their going to use a coil-carrier and bypass....

I thought he was done putting money into that thing! I'm glad to see it get an update. It's definitely one of my favorite trucks.

Remember this?

g54YCQ9YfQM
Quote:
Originally Posted by PWMTN View Post
Steve, Good post
The video is a classic example of a setup with a very slight error in rebound. Video is a great tool for tuning. The rock crawler guy in Farmington had problems tuning his shocks for rock racing (Brown's Toy pickup). The shock guy said send me a video and all the shocks. The result was perfect tuning and with lots of air with no issues. After tuning the truck always flopped down on all 4 wheels at the same time on all kinds of different whoops.
The video should be linked to "suspension 101"
Paul
==========
Quote:
Originally Posted by steveG View Post
I think that one was more of a problem with the approach and launch. The truck had a fresh engine with a lot more power than he was used to and even he said he got spooked and lifted too early allowing the truck to rotate. I've seen the same truck with no changes go off that jump and land like a champ.
Carry on.
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post #18 of 28 (permalink) Old 03-25-2009, 01:22 PM Thread Starter
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Brian's setup

Quote:
Originally Posted by yikesbb View Post
Tight indeed, Paul! They take the big hits nicely, but as you indicated, could use a bit more compression, because the rear has been bottoming occasionally on some of the bigger hits. The F53 pack seems a bit lower rate than the Nationals you were running. I'm thinking of mounting my 2.0 bumps to compensate. I've been experiencing quite a harsh ride above 40mph through a series of whoops. At 60, the ride is quite rough and feels like it's stacking up/rebounding too slow. Passengers are complaining about their necks. Ha! I've got a different valving set-up (big thanks to SteveG) I'm going to try to see how it fits my driving style and Barstow type whoops, which I believe are tighter than what you had this set up for... SF.

Brian
=======
Oh, I forgot you have a different spring pack. Since the Nationals did not hit on my Bronco the difference must be the different springs. What length are your Deavers? Anyway, if you talk to Deaver they may suggest a slight change . Maybe the top leaf. Probably cost less than bumps?
Paul
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post #19 of 28 (permalink) Old 06-15-2009, 11:48 AM Thread Starter
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post #20 of 28 (permalink) Old 09-23-2009, 01:54 PM
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WOW...... ive spent the last 3 days just trying to cram my brain with all the years of test and tune you guys have in these broncos! Fantastic group here, cant wait to get my project up and running. my eyeballls hurt
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