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Old 08-16-2018, 01:45 PM   #1
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1970s Era Chevy/GMC C Series Chassis - Front end suspensions and steering.

My 1970 C40/Thomas bus has steering wobbles even after steering and suspension rebuild. Any luck working on these beasts and their handling issues?
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Old 08-16-2018, 04:19 PM   #2
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I cant see pics but if you have Dayton rims, make sure the last people to have a tire off got the rim back on straight so it is running true..



if you have Budd-rims, make sure they are centering correctly... worn stud-pilot rims may not center correctly, ir if the incorrect nuts are used..



when you said front end rebuild - was the lash tested on the steering Box?



finally, how are your front tires?
-Christopher
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Old 08-16-2018, 05:04 PM   #3
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I cant see pics but if you have Dayton rims, make sure the last people to have a tire off got the rim back on straight so it is running true..



if you have Budd-rims, make sure they are centering correctly... worn stud-pilot rims may not center correctly, ir if the incorrect nuts are used..



when you said front end rebuild - was the lash tested on the steering Box?



finally, how are your front tires?
-Christopher
Front tires a good, but rims should be looked at as you suggest, not sure which kind they are, but one looks older like a widow maker style. Will ask the mechanic who worked on it about rims and lash. Thanks Pix coming soon
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Old 08-16-2018, 07:20 PM   #4
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King pins??? Had to ask.
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Old 08-16-2018, 07:25 PM   #5
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Could tire balance be an issue? Are these usually balanced? I remember running golf balls in the dump truck tires to auto balance them.
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Old 08-16-2018, 08:22 PM   #6
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King pins were replaced, that’s what I first assumed when I first noticed steering vibration. The rebuilt steering box, hub bearings, new shocks and more that I can’t remember. I’m looking into to rim or tire issues next.
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Old 08-17-2018, 06:34 AM   #7
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bias ply tires? or radial? Radial will made a big difference in handling. So will adjusting slack in the steering box. Seems your problem is most likely balance though.

Have to ask does it brake smoothly? an out of round drum can also cause vibration even when not braking, and would be felt more when braking.
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Old 08-17-2018, 08:39 AM   #8
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bias ply tires? or radial? Radial will made a big difference in handling. So will adjusting slack in the steering box. Seems your problem is most likely balance though.

Have to ask does it brake smoothly? an out of round drum can also cause vibration even when not braking, and would be felt more when braking.
Bias 7.50 x 20, wish radials were available for rim size, otherwise I think I'd have to switch rims to 22.5 for radials with proper height/diameter to match existing. Braking is smooth as far as I can tell. I'll check slack in steering too, but as I mentioned previously I'm betting on rims or tire balance being the issue.
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Old 08-17-2018, 09:37 AM   #9
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Nope radials should be available.. im fact I was just in Portland and got Jacked around by Schwab on a couple on my latest bus purchase... I needed two front tires bad.. so I took it to them and they said they could get 9R20 Radials to put on my Locking-ring rims.. I asked about swapping up to 11R22.5 stud pilot and the guy said "cant do it" ..


so on went the 2 9R20's. they found a bad drive tire.. flat... and I said.. just put all new drives on.. i need good tires.. chinese tires.. cheaoer.. no biggie.. so I drive the 2 miles back to my hotel and get a call "Hey would you like to go to tubeless tires? 22.5 low profile are a near size match.. "what about 11R22.5?".. 'sure' youll just need a new spoeedo gear..'..


so hey what about those fronts? 'oh yeah we can do those but cant give you $$ back because we mounted those fronts and you drove 2 miles'...



grrr! when they gave me bad info... so yeah I have a bus with 2 9R20 radials up front on 10 bolt Budd rims.. they do exist.
-Christopher
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Old 08-17-2018, 04:09 PM   #10
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Thanks, I’ll look into those 9R20s! Done with bias I thought 40 years ago, lol. Also now recalled that the piece not replaced was the drag link, as none were available through various sources other than ones as worn as mine. Any ideas on where to find such rarity and/or could a custom shop fab one?
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