Frame stiffness - is stiffer better, so to speak? - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 10 (permalink) Old 09-08-2012, 12:32 PM Thread Starter
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Frame stiffness - is stiffer better, so to speak?

Hey all, sorry for what seems like it may be a dumb question. i've been looking at replacing my current ride, a 2002 GMC 1500HD and am set on a diesel. i've been trying to do all the reasearch i can on each different model and all.

planned use for the truck is a daily driver for me and will pull a 13K-14K 5th wheel once a month or so.

i'm mainly focusing on looking at crew cab 1-ton's with SRW's.

My biggest concern is reliability, as i put about 25K+ miles per year on my current truck (doesn't pull a 5th wheel, just an occasional trailer of about 5Klbs and hauls a couple sportbikes and the family)

so, to one of my questions. Frame stiffness. i found this video on line
http://http://youtu.be/p6sPEvxpLoU
and at one point it compares the frame stiffness between the Ford 350 and GMC 3500. video made sense at first, and showing the GMC had a far stiffer frame and that thats better. but, reading through some of the comments on the video got me thinking.

Stiffer frame should be better for a more "solid" feel. but does stiffer = stronger? if the frame is to stiff, could that hurt towing ability of the ground was uneven, or if towing and hit a big bump? where if there was a little flex in the frame couldn't that help keep the wheel planted in going over back country trail (thinking out of the way camping spots down camping roads) or say if i was towing and hit a large bump, pavement transition ect, if it was big enough hit to max the suspension, could an overly stiff frame really suffer damage (like one comment said)?

am i over thinking all this?
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post #2 of 10 (permalink) Old 09-08-2012, 01:50 PM
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Your link has nothing to do with Ford vs Chevy. It is just a bunch of pretty girls.

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post #3 of 10 (permalink) Old 09-08-2012, 05:24 PM
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Frame stiffness is important as that is what everything is mounted to and having the engine, transmission twist is not something you want.
As far as the frame being too stiff, the suspension, and the tires, is what moves to absorb shock loads a stiff frame alows a more stable steering platform.
A stiff frame alows a camper in the box not to crack up from continual twisting.
Ford is very good at putting up big numbers for power, but looses on the real word test. They are great at posting big numbers for what it can tow, but in the real tests comparison it burnt the brakes up.
I live in the mountains at the bottom of a hill, 2,000 ft of down grade and when a vehicle goes by with burnt brakes it is a Ford.
I love Ford without them their would be a million mechanics out of work.

1988 ford van fresh overhaul, 1991 nissan pick-up 1993 Caprice 2000 GMC S10 Blaser 2007 nbs 3500 GMC 4x4 crew-cab long box 17 inch single wheels Duramax Alison. BW turnover Ball. Furakawa FL35 loader. Retired, HD mechanic, worked on engines all my life. Fabricator welder. electrician. in the process of finishing my new shop. Live in Rock Creek B.C. Wife has a fruit stand.
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post #4 of 10 (permalink) Old 10-04-2012, 04:22 AM
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well the only ford i got the brakes smoky on was a 91 ford explorer, trying to respond to volunteer fire call. 80-90 mph coming down a pretty decent little coulee, with a hard turn at the bottom. they were fading noticeably but just a tiny wisp of smoke. my pickup, I know my limits never even get them warm. frame stiffness is great but the stiffer the frame, the more flex the suspension needs. in the mid 80's when the 4x4 magazines started ramp testing you saw huge frame flex, as they developed more flexy suspensions, the frame flex dropped way off. the two go together stiff frame+stiff suspension=rock wagon. soft frame+soft suspension=sloppy piece of mush

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post #5 of 10 (permalink) Old 10-04-2012, 05:05 PM
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I have a GMC 3500 4x4 crew cab Duramax, long box, I go out and get wood with a 14 ft goose-neck dump trailer. I can go threw 12 inch holes, with no problem, There are roads that are decommissioned and only short vehicles can go threw. I have a G80 rear gear and can go threw places in two wheel drive friend's can not go threw, and they have shorter fords. In 4 wheel drive, getting hung up is my only worry.
If you look at a GM frame it has a pipe welded in the frame, as any good welder will tell you, pipes do not twist, or flex.

1988 ford van fresh overhaul, 1991 nissan pick-up 1993 Caprice 2000 GMC S10 Blaser 2007 nbs 3500 GMC 4x4 crew-cab long box 17 inch single wheels Duramax Alison. BW turnover Ball. Furakawa FL35 loader. Retired, HD mechanic, worked on engines all my life. Fabricator welder. electrician. in the process of finishing my new shop. Live in Rock Creek B.C. Wife has a fruit stand.
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post #6 of 10 (permalink) Old 10-05-2012, 01:39 AM
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Quote:
Originally Posted by Johnp3 View Post
I have a GMC 3500 4x4 crew cab Duramax, long box, I go out and get wood with a 14 ft goose-neck dump trailer. I can go threw 12 inch holes, with no problem, There are roads that are decommissioned and only short vehicles can go threw. I have a G80 rear gear and can go threw places in two wheel drive friend's can not go threw, and they have shorter fords. In 4 wheel drive, getting hung up is my only worry.
If you look at a GM frame it has a pipe welded in the frame, as any good welder will tell you, pipes do not twist, or flex.
Um sure they do. Every metal has a yield and tensile limit - not bashing just saying your comment has nothing to do with a frame design. Structures have design and material properties which allow for many loading aspects. It has nothing to with being a good welder.

All I will say is a lot of good friends of mine spend a lot of time developing the very best welded structures found in your trucks and cars. The average person has no idea of the technology behind the materials used to make today's vehicles safe and perform well. Google the following topics to learn more about latest advancements in steel. Dual phase, TRIP, Press hardening.

Some cool things coming down the pipe for automotive structure technology.

Buy a truck that looks nice, rides well and does what you want it do wouldn't worry about the frame. I'd worry more the Mrs. likes it.


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post #7 of 10 (permalink) Old 10-05-2012, 05:01 PM
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A pipe will break it will not twist at anywhere close to the rate of any other shaped steel.
As a mechanic that also fabricated many pieces myself I have seen instances where engineers have installed a pipe cross member, in a location that did not work. I am thinking of a twin-steer cement truck between the front axles they installed a pipe, it would break, I replaced it with a removable, "I" beam problem solved.
You can not make a poor designed frame stiffer by adding inappropriate cross members, it will break the frame, everything has to be designed properly in the first place.

1988 ford van fresh overhaul, 1991 nissan pick-up 1993 Caprice 2000 GMC S10 Blaser 2007 nbs 3500 GMC 4x4 crew-cab long box 17 inch single wheels Duramax Alison. BW turnover Ball. Furakawa FL35 loader. Retired, HD mechanic, worked on engines all my life. Fabricator welder. electrician. in the process of finishing my new shop. Live in Rock Creek B.C. Wife has a fruit stand.
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post #8 of 10 (permalink) Old 10-05-2012, 06:06 PM
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Depending on the stresses it may make more sense to allow some flex rather than making it more rigid. Cast iron is very rigid, lightweight, but when it reaches its limit it fails catastrophically rather than deforming, or flexing and rebounding. Total rigidity may add an excessive weight penalty or transmit mote shock to other components. Point being Chevy has a good frame and so does ford. Different engineers places different priorities on different values

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post #9 of 10 (permalink) Old 10-05-2012, 06:45 PM
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Research "frame beaming". The 2011/2012/2013 GM 2500HD/3500 have redesigned frames (bascially they caught up to everyone else with the hydroformed tube frames) and some of these suffer a shaking at highway speeds.

Mine does a little, feels like a tire out of balance. Add a few hundred pounds to the bed...smooth as glass. The condition is caused by the frame being too stiff...nothing to do with suspension as it will do it on perfectly smooth roads.

SOLD - 2004.5 2500 Ram, 600CTD, NV5600, 4.10s, FASS'd, Dynatrac Free-Spin Kit, Gulf Coast 0-1 bypass, Intake and Exhaust.

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post #10 of 10 (permalink) Old 10-07-2012, 02:36 AM
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Quote:
Originally Posted by Johnp3 View Post
A pipe will break it will not twist at anywhere close to the rate of any other shaped steel.
As a mechanic that also fabricated many pieces myself I have seen instances where engineers have installed a pipe cross member, in a location that did not work. I am thinking of a twin-steer cement truck between the front axles they installed a pipe, it would break, I replaced it with a removable, "I" beam problem solved.
You can not make a poor designed frame stiffer by adding inappropriate cross members, it will break the frame, everything has to be designed properly in the first place.
I agree tubes and pipes have some advantages from a structural point of view just not certain there is a major difference between the design of the three main light truck OEM's - some are boxed some are not. Actually most light truck frames are made by usually either MAGNA or Metalsa (formerly DANA structural solutions) and supplied to ford, gm, dodge, toyota. I think Nissan makes their own frames.

Early 2004 F-250 4x4 CC 6.0


2nd owner, ARP studs 1 at a time, Some parts missing in the exhaust path, BD intercooler hoses, Blue spring, MC filters, Sinister coolant filter, Exhaust manifold gaskets, WARN lockouts, Gold coolant, zoodad mod, autometer boost gauge, high idle mod, Scangauge 2, SCT X3 tuned from KEM, autometer fuel pressure gauge, Archoil 6200 in the fuel, FICM by Ed w/ATLAS40, autometer pyro gauge,'08 Alum Rear Diff cover, 5w-40 Rotella T6 w/ Archoil 9100 in it, zert in the slip joint, harpooned fuel tank, 6.4 banjos


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