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front spring options for ride comfort.

Posted By Lmackattack Friday, June 11, 2010 7:50 AM
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Lmackattack
 Posted Friday, June 11, 2010 7:50 AM
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32 year old Mack rides well....like a 32 year old mack should

currently has a 3 leaf spring set up. Is there a way to soften up the front end for ride comfort but still retain the axel rating. New trucks seam to ride alot better and can still put weight up front. what are the options. not looking to remove a spring and louse axel rating. intrested in finding out if a spring shop can reproduce a newer spring for me that will work on a older truck.  has this been done before?




1977 Mack RS700L....parked.... 

1965 Mack B61 currently restoring. its only been 9 years
Geoff Weeks
 Posted Friday, June 11, 2010 8:23 AM
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A lot has to do with the pins and bushings, If they can't move easly then the whole thing is stiff. 3 leaf should be good, its the old stacked leaves that are hard rideing. Check the ride height and make sure they haven't taken a "set". I have to replace the fronts on the Marmon soon because of it. The front is lower then the back.
glenn akers
 Posted Friday, June 11, 2010 4:37 PM
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Also the longer the spring is the softer the ride.The newer truck may have a longer spring than your 32 year old truck.

glenn akers
Freightrain
 Posted Thursday, June 17, 2010 9:24 AM
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When I checked with my local spring shop about getting tapered leafs for the B, he looked through his spec book and we compared numbers.


Guess that would be the first stop.  Get your part number and compare to anything else.  Likely, like Glenn said, the spring will be too short to put a late model set up under it.


Larry
I'm no expert........but I did stay at a Holiday Inn Express last night.
Lmackattack
 Posted Friday, June 18, 2010 10:33 AM
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called the local spring shop and they said to get a OEM number first. Will start there first. just thinking out loud could you removing a top spring and add a air bag under it to help the ride .....or  will that greatly reduce hauling capacity.

I have seen these pick up trucks with the air helper bag and have been in a few




1977 Mack RS700L....parked.... 

1965 Mack B61 currently restoring. its only been 9 years
John_Costley
 Posted Sunday, June 20, 2010 11:53 AM
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Trent,

Like Geoff said, the first step is to make sure both ends are free and the leaves arent frozen together.

If everything is free, a set of custom parabolics will smooth her out.Rob Swallow was looking into this option for one of his RLs.Run a search on the forum for the word parabolic.John
Rob
 Posted Sunday, June 20, 2010 3:25 PM
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John_Costley (6/20/2010)
Trent,

Like Geoff said, the first step is to make sure both ends are free and the leaves arent frozen together.

If everything is free, a set of custom parabolics will smooth her out.Rob Swallow was looking into this option for one of his RLs.Run a search on the forum for the word parabolic.John


Hi John, glad to see you back and hope all is well on the personal front:

I had neglected to update you what I found out with the front springs for my RL series tractor.

This series of truck uses front spring pins that are threaded into their corresponding mounts which also support the radiator and hood mounting arrangement. I was able to come up with a spring through Dayton spring that was within 3/16ths of an inch in length to fit but would require that I bore my original mounts in the front larger, then bush them down to a corresponding straight pin for the replacement spring. There was no pin available that was the correct length off the shelf so that would have needed custom fabricated and hardened. Where you would need to bore for a retaining fastener to hold this new front pin into it's corresponding mount would appreciably weaken the structure, so I went no further with the project.

I ordered a set of new springs from St. Louis Spring Co. whom I've used for over 30 years and they made me a stock set of springs in the correct ride height and weight rating. I was told the old spring packs were "stuck" so I'm certain that had a little to do with the harsh ride on the steer and the passenger side second leaf was broken through. I have not mounted the new springs under the truck yet as I ran into title problems with this chassis that are since resolved. I'll get back to it after the Detroit engine is installed into the other R700 truck.

Need to get something finished around here.......

Rob
Lmackattack
 Posted Monday, June 21, 2010 6:05 PM
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Welcome back John

what I noticed was these springs have groves at the ends where the leafs were rubbing on each other. as rob has mentiond the front hangers have pins that get scred in and the rear hanger have a simple shackle that lets the rear pivot. they do move and I keep them well greased. the ride is not all that bad when loaded but pretty bad when empty.

just searched Parabolic spring and that is kinda what I was thinking would work with an air bag. simmalar concept I had in mind.

 Looking at this site

http://www.parabolicspring.com/parabolic.htm

I wonder If a spring shop could calculate what the current main spring is and then how to incorparate 2-3 leafs but in a parabolic style. here is a pic of the 3 leaf spring set up on macks. I think that because all 3 springs are so flat that the friction they have does not let them move freely and soften the ride. They do last tho. have never heard of a issue with the stock set up besides the driver complaining about the ride quality!





1977 Mack RS700L....parked.... 

1965 Mack B61 currently restoring. its only been 9 years
John_Costley
 Posted Tuesday, June 22, 2010 12:20 PM
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Trent,

You probably already noticed from searching online, but there arent many domestic manufacturers that make parabolics.Heres one http://www.standens.com/spring.htm  But they dont advertise doing single order customs.Heres the outfit Rob used  http://www.saintlouisspring.com/   Seams like there should be some good old fashioned spring shops around Chicago that would still have the machinery to build their own spring packs from flat stock, rolling their own ends on site and arching leafs in house.Thats the way they all used to do it, though most spring shops just resale other peoples import stuff nowadays.

If a spring shop gets confused or nervous when you ask them for custom parabolics, just tell them you want what will basically be a Pete 379 3 leaf spring using youre end style, youre width, youre center bolt location, and youre overall leangth.If they build springs from scratch it shouldnt be a big challenge.They could use a stock Mack main leaf with two Pete parabolics underneath if they measure out right.The parabolic effect comes from the arch and end contact of those lowers leafs.Empty, they dont do anything and you basically ride just on the main, loaded they make contact and support the main, the heavier the load, the more they flatten out and contact the main.Most parabolics dont look as exagerated as the ones shown on that site you posted, most just have enough extra arch on the lowers to leave a gap between the leafs, aside from that they look like any other leafs.Same principle as extended leaf Hendrickson.John

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