The Stovebolt Site Forums The Shop Area The HiPo Shop What is the highway speed limit of a solid front axle?

I restored my 1950 3600, converted it to disc brakes and have a front sway bar. The truck feels great, up until about 62 mph, where I start to feel vibrations building. Everything was replaced or rebuilt. There is no apparent play in the front end, at least none that I can detect when it’s jacked up off of the ground. No wheel bearing looseness, no king pin play.

I have had the wheel/tire assemblies balanced twice, and it was a big improvement, but as I troubleshoot my vibrations, I really need to know if it is normal front end to get unhappy at speeds above 60/65 mph.

Would love to hear your opinions regarding the stock front end at speeds above 60 mph᠁.I just don’t want to be chasing my tail with it.

Any input appreciated,

Dave

I have an unrestored 1950 3100, 216, 3 spd with new wheels and tires and unrestored steering and front end.

I drive regularly at 55 without vibration or wonkiness. I've had the truck up to 65 without issue. I believe that if my engine could tolerate sustained driving at speeds of 65mph I would experience no vibration.

Check your driveshaft, flywheel, whatever else that causes vibration at speed or just drive 55 and be happy with your old truck.

Swap the wheels front to back and see what happens.

Dave, I’d check the wheels very closely. I chased my tail a few months ago on a vibration that only started above 70 (not on the ‘51). Tire shop couldn’t find the cause. I had another mounted good tire/wheel so just started swapping it around, test, move test wheel, road test᠁..

After determining it was the left rear I carried the wheel/tire back to the shop and they finely agreed it was very slightly bent but assured me it was not enough to be a problem.

One new wheel later and problem solved.

Good Luck

RonR

Why would there be a limit? Gassers do fine.

Even modern big trucks still use solid axles up front and go 80+ MPH all day long. There isn't anything inherently wrong with solid axles.

I would agree with the above to go through all the rotating parts and check them out again. Have you checked your driveshafts and carrier bearings?

I've had my '52 GMC 3/4 ton to 73 MPH (GPS verified) with no shaking. Rear gear is 3.55. Yours is probably numerically higher.

i have a 1939 chevy 1.5 ton truck updated running gear , still the same straight axle . i have had this truck up to 80 MPH with no problems .

When I take my daily drivers in for tire balance/rotate, I specify a "road force" or "load force" balance. Not all tire shops have the equipment for that type of balance, and it's a higher price per tire. It simulates a loaded tire on the balance machine verses the common high speed spin balance. That may be a simple solution.

Drive shaft+U joints if not tires. Specially if its a building vibration and not shaking.

Thank you everyone for your replies. It looks like I have my work cut out for me now- I’ll make a list and start working my way through it.

The wheels are Wheel Vintiques Rallye wheels (new) and the tires are also new, however one or more may have developed a flat spot after the truck sat for a while on the tires. I have put over a thousand miles on it since the restoration, and the problem only appears on the highway at speeds above 60, and is exacerbated by any ripples in the road. It almost seems like a subtle wheel hop.

The custom driveshaft was removed and balanced (again), and it was found to be out of balance right from new᠁. Go figure. Some improvement with that.

I even replaced both rear axles with new, and all new bearings- no change in vibration.

It’s a 3.75 rear axle out of a GM metric blazer. Set up by a reputable rear axle shop.

The truck has a T5 trans that I rebuilt after the vibration was first noticed, with no change after the rebuild. The vibration is not engine-related, as it only occurs at speed, and there are no (unusual) vibrations from the engine at any rpm. When I removed the trans to rebuild it, I also had the flywheel checked again for balance- all good. I also checked everything with a dial indicator (flywheel running true on the crank, engine/bellhousing/trans alignment in both planes).

I am creating the list. From day one I have felt that it is wheel/tire related, and assumed that balancing with a “fingers” setup would solve it, as I have read that some Rallye wheels will not balance using hub-centric setup, due to issues with their manufacturing and the center hole stamping sometimes being off᠁ it got a little better, but it is still there- and that might say a lot about where the problem is- most likely the wheel/tire combo.

I will say this- some of the wheels took a lot of weight to balance, and we had to put weight on the outside of the wheel as well, to get a decent balance. The tires aren’t huge- they are 215/75/15 BF Goodrich Long Trail T/A

If it is the tires, I am going to go with a set of new Coker steel belted radials that are narrower and larger diameter and have a bias-ply look to them ( The T5 has a pretty low first gear with my 3.75 rear end).

One more question: if the truck sat for 6 months on the new tires with that heavy stovebolt engine in there, and I have driven it over a thousand miles since, is it still possible that I may have some flat spots?? I have tried to raise the truck, slowly spin the tires and eyeball them, but I cannot really determine if there is a flat spot there, but to normal tire irregularities.

Thank you again,

Dave

I strongly recommend against Coker tires from personal experience and that of others. I had a belt separate inside a tire in under 10,000 miles. Cokers have a pretty low reputation in the collector car community for being difficult or impossible to balance properly.

Corky Coker told the president of our club that if the car is being driven like a normal vehicle instead of just for show, he should purchase a set of Diamondback tires.

I have 3 sets of them and they're the best radial tires I've ever had on my Cadillacs and Packard. They're radials and have a bias ply look. The ones on the black car are the new Auburn radials and have a pie crust edge that looks even closer to the old bias plies. The close up is a Yokohama truck R700 truck tire with the whitewall vulcanized to it.

I think swapping your wheels front to back and back to front might give you a clue about the source of the vibration.

www.dbtires.com

Dave,
Mine is a ‘48 3100 but with a 327/700R4/3.73 Posi/255-70-15’s on Progressive aluminum rims-also front disc brakes, and I’ve also kept the original solid front axle. The sweet spot at highway speeds is about 72mph, although I’ve had it up to 85mph (at which speed my common sense kicks in?). No vibration. I doubt your vibration can be attributed to the solid axle. Many years ago at the shop I started at the manager required that if a tire had a dot on the sidewall (orange, yellow, red) that it be lined up with the valve stem hole on the wheel. The explanation being that the tire and wheel companies marked their product accordingly such that the alignment of the dot and valve stem would insure that the high spot of wheel was matched to the low spot of the tire thereby keeping the radial runout of the assembly to a minimum. Common sense. Not to long ago I got a new set of tires at Firestone and my “sweet spot” was GONE! Bad vibration at 55-65. Back to Firestone and a rebalance improved the situation marginally. I got my dial indicator out and the left-front had .090” radial runout!!!! After close inspection I could see the orange dot on the sidewall on 3 of 4 tires and they were NOT aligned with the valve stem. Back to Firestone and I had them remount the tires: problem solved! Dave, above you said you dial indicated “everything”. Have you checked your lateral and radial runout on your wheel/tire assemblies? This will also confirm if you have any flat spots on your tires from sitting. Specs attached᠁.
Good luck, Dave

Man, that is pretty cool. I have seen those dots on tires in the past and never knew what they were for. Clearly most tire shops don't know what they're for, either!

Question, how would the tire company know what wheel the tire was going on, in any given application, to know where the high spot of the wheel was? Steel? Aluminum? Magnesium?

If I remember from my training a billion years ago, it was a balance issue. Tire steel belts have joints and wheels have holes for valve stems which create a very slight imbalance on either assembly. Lining up the dot with the valve reduced that imbalance as much as possible.

Somewhere along the way, we were told that setting the beads, then allowing the air to escape to relax the tire, then reinflation to pressure, equalized the way the bead set on the rim. Something most tire shops won't do as it adds time to the job.

MNSmith,
I’ve heard your argument also. I’ve never worked for a wheel company or a tire company. My understanding was that all the wheel companies (steel, aluminum, magnesium) had an agreement that the valve stem hole was an indicator of where the runout of the wheel would counteract the runout of the tire (as indicated by the dot). I won’t argue that the material removed to punch the hole for the valve stem does contribute to some minimal imbalance. I do know that matching the hole to the dot made the service manager happy and kept me from getting my butt chewed. And in my recent Firestone case it fixed my vibration. I followed up w my dial indicator and my runout was reduced to .020”. Maybe someone in the group that may have worked on the engineering side of a wheel or tire company can chime in?

Thanks. I'm definitely smarter now.

This is what the manager of the local Discount Tire told me as well.

I kinda want to go measure the runout on all my tires now... Not that I have any complaints, I am just curious.

Another item to address is having the tire trued to round. An old timey tire store or alignment shop should be able to do this. They spin the tire on the vehicle and shave off the high spots. When done correctly the tires will roll like a pool ball on a slate table, with no bumps.

Back in the dark ages when I was an equipment maintenance man for Armstrong Rubber Co. in Madison Tennessee tires got stamped with a blue or a yellow dot (or none at all) to indicate "conicity"- - - -the tendency of an inflated tire to pull toward one side or the other. Try to roll a cone-shaped paper cup in a straight line sometime. The tire was inflated on a piece of machinery that measured the side to side pull and stamped accordingly. People in the know about that would choose to install tires with the same colored dots on opposite sides of a vehicle so the pull of each tire would cancel the other out and avoid the vehicle from wandering one way or another. The old mechanic's tale about aligning the dot with the valve stem was, and probably still is a myth.

That was in the late 1970s- - - -things might have changed since then.
Jerry

To me it sounds like there's a chance it could be flat spots. Most folks will say 6 months, but a fellow who worked for a tire shop here told me it can happen in a month to 6 weeks depending on a few different factors. He said they tell folks if the tires are good quality and the problem is from sitting in storage or parked in the same place a long time to (1) overinflate the tires by 5 to 10 pounds, (2) drive the vehicle...preferably on warmer days and only for 50 to 60 miles at a time. He said not to drive faster than when the shaking is felt, not to take a long trip until you see if the situation improves (could cause odd tread wear or in some cases belt separation) and to expect it to take weeks to be okay unless you're doing this in the middle of the summer. I had this happen on a Pontiac I almost never drove. No amount of balancing, moving dots on tires to match the valve stem location, switching tires...nothing helped until the tires finally settled back down. Once they did, all was as it should have been. Good luck!

Jon, I did exactly that, and there was improvement, but the vibration is not completely gone.

I am going to jack the truck this weekend and pull out my dial indicator. I have no idea what the wheel runout limit should be. I will put the indicator on the outside of the wheel, right where the tire seats.

Flat spots are hard to locate, especially when they are small ones᠁. Tires have imperfections, and I cannot tell the difference. Shaving the tires is something that I considered, however, if they have flat spots, I feel that that would not be a good idea- if they were simply out of round, I could see doing that.

Measuring tire flat spots is not easy- I have been spinning the wheel by hand and trying to feel the tread with my hand᠁ not very scientific. Perhaps I should create a tool/jig with a skateboard wheel on it that I can place against the tread, and see if contact is lost as the tire is rotated?

I have never had issues with tires before, and I have owned a lot of older cars- so this is new territory for me.

If I do have to get new wheels, are you guys running hub centric wheels on lug centric axles/hubs? I don’t like my wheels anyway, and may end up just changing them at some point. I would change to cast aluminum wheels. My rear axle is not hub-centric, neither are the front hubs.Just thinking ahead here, as my tire diameter is actually too small for my gearing, and it looks small on the truck, and I am guessing that I am going to discover that at least two of my tires are messed up from supporting the front end.

The last place that balanced the assemblies said that they had a hell of a time, which is what the first shop said as well.

I’ll report back my findings here this weekend. Thanks again, Dave

Norcaldave
“ I am going to jack the truck this weekend and pull out my dial indicator. I have no idea what the wheel runout limit should be. I will put the indicator on the outside of the wheel, right where the tire seats.”

Maybe the attached will help:

Flatblu4748: What book is that?

Dave, on my pickup I just have 15 inch GM wheels (6 lug) that I picked up when I was moving away from the slightly more narrow 16 inch ones. I've never checked them...never had trouble but I usually drive at 60 and not faster than 65. On the GM Heritage pages years ago you could see an internal memo (appeared to have been written to dealership managers) stating the AD trucks had been engineered for a constant highway speed of 55 mph and were ok for intermittent speeds of up to 65 mph. I averaged those and figured with the improvement in tire design it would be okay.

Also fyi I am using Hankook Optimo All-Season Tire - 205/75R15

Thanks Jon- that is EXACTLY what I needed!

If I do replace the tires, I may try to go a little narower, if I can- 215's are fine until I have to parallel park the truck... I have 6" rim width, though, so I'll have to check the minimum rim width for a 205. I will say, the 215's are really nice on all the curvy roads I have where I live.

Fibonachu:
From a GM Training Center Class I attended 20+ years ago. It says July 1996 on the back cover.

I have 205's on my '72-91 Blazer/4x4 15"x6" wheels up front and they seem to fit fine, tire shop didn't say anything about it when I had them put on. They are Cooper Trendsetters that I believe have been discontinued.

I run mine at 70 on the highway for as long as traffic allows until I get where I'm going, and have no noticeable vibration issues. 216/T5/3.90, disc/drum, 3" dropped solid axle up front, stock leaf springs. It feels like an old truck on bumps, but doesn't vibrate, bump steer, or wander.

If you have a stock front end/suspension, the best thing will be to match as closely as possible the width and height of the wheels/tires originally used plus the wheel offset (if your new wheel deviates from centerline orientation, that is). This is to preserve (or not cause to make more negative) your scrub radius. The more negative your scrub radius becomes, the more difficult your steering becomes...usually exponentially.

The 205 has a minimum wheel width of 5.5" so you would be fine with 6 inches.

That is a cool resource. Thanks for sharing it.

Thanks Jon!

Thank you very much for posting those pages- now I know what to do.

I cheated.

Smokey Yunick said " It's only cheating if you get caught". That a beautiful setup, can't wait to see the chassis together.

Smokey Yunick said " It's only cheating if you get caught". That a beautiful setup, can't wait to see the chassis together.
[/quote]
Thank you. It's designed to leave the ground and safely return. There are needle bearings in the king pins and Heidts pins on the spindles. I'll be working on the chassis this winter.

Sorry for the late question but can you describe the vibration? Once it starts does it get worse with speed or does it remain the same? Keep in mind that we are driving these trucks at speeds that they we not designed to do initially. In my truck, in the rare times I get it up to speed, I develop a vibration around 55-60 but it then goes away past that. Every truck that I take up to speed does that. Looking at your photos you have a longer wheelbase than my truck so your vibration may just be a little higher like Charlie, our Stovebolt Flagship.

Keep in mind this truck is not ever going to ride like a modern truck with stock suspension.

The vibration feels like a wheel hop/bounce, and it becomes most noticeable around 60mph, increasing in intensity with an increase in speed. It is exacerbated by any rhythmic imperfections in the road surface, such as ripples.

The way I see it, if I have new bearings and my alignment is correct, I should be able to do over a 100 mph easy, just as older dragsters do with the same type of front end, provided my wheels and tires are good, and there are no loose/worn suspension or steering components. That said, I’m only looking for 65 with no vibration᠁..and I will continue to drive it at 60, as usual.

So-

I jacked the truck up today and followed the procedure posted by flatblu4748 . I have a low spot on every tire. The worst one was on a front tire, and it was 0.10. A tenth of and inch! The rest were .065 to 0.070. This measurement was of a definite “low spot”, not really a radial runout.

I didn’t dismount the tires, so I could not properly check the rim lateral and radial runout from the inside of the rims, but I did run the dial indicator along the outside of the rims as best I could- lateral and radial deviations ran between 0.010 and 0.020 on the outside of the wheels, and this is after they were blasted an powder coated, so I think the wheels are probably okay. We’ll see after the new tires are mounted.

My tires are ruined due to the truck sitting for many months on them. My mistake. I tried all the tricks- slightly over inflating and taking 50-60 mile trips, etc᠁ after over 1,200 miles of trying, I am giving up and buying new tires. With my 3.73 rear end and my T5 close ratio trans, I need a taller tire anyway- 1st gear is like a granny gear right now.

I’ve got 15x6 wheels and have ordered a set of Diamond Back Auburn Deluxe radials, size 820-15. They will be the perfect diameter (I was running 215/75/15 and they were not tall enough). About a tenth of an inch narrower in the tread than my 215’s , which is good. Perhaps it did not help that my 215’s are on a slightly narrow rim (6” width is limited to 205’s per most charts I have seen).

Anyway, in a couple of weeks I’ll post again after the new tires go on, with pics and a test drive on the highway.

BTW- those Auburn tires are NOT cheap! $279 a piece, but Summit Racing offers free shipping. I don’t like ordering anything from large companies, and would have preferred to order direct from DB, but I figured the shipping $$$$ all the way across the country would be prohibitive. And since this is an unplanned re-do, the expense is already depressing. The reviews on DB tires are almost all stellar, and I want to get it right this time. DB told me that they will not ship tires with a cure date over 2 years, and that presently, because the product moves quickly and they just got a container in October, my tires will have a much more recent cure date.

What was the price when ordering them directly from Diamondback? Was Summit cheaper?