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How do I measure for Straight Axle track width?

43394 Views 47 Replies 14 Participants Last post by  manicmechanic
My '53 Ford Mainline has king pins in stock setup... So do I meaure center of king pin to center of king pin... then order a straight axle at that width?

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If nothing else, that'd at least give you a base number to start with. If you're gonna be running skinny front wheels, you could go a little wider with your axle so your wheels don't look " sucked in too far " if you know what I mean. Should be more stable And handle better also
Yeah I will be runnin a 15" X 4.5" front wheel... and I do know what your talkin about I don't want it real narrow in the front. I measured king pin to king pin @ 50" maybe I should go with a 52 or 53" axle. I was lookin at the Speedway catalog and the 46" axle says it will measure 54 1/2" hub to hub. So do I go by king pin to king pin since that is what I'm measuring @ on my stock suspension or do I take a hub to hub measurement?


Okay, I measured hub to hub....I should be more clear I measured backing plate to backing plate @ 53". So should I order the 46" axle since it says 54 1/2" hub to hub? Why do I got a feeling I'm making this harder than it should be...LOL...?

Speedway's kits measure as follows"

44", 52 1/2" hub to hub
46", 54 1/2" hub to hub
48", 56 1/2" hub to hub
50", 58 1/2" hub to hub

See a theme here? Add 8 1/2" to the king pin measurement and you're golden. Hub is the wheel mounting surface.

What I would do is pull the front tires with the lower arms resting on jacks and use a couple yard sticks or levels on the drum face and measure the distance, mounting surface to mounting surface. Find the axle that is the closest match based on what wheels/offset you want to run on the front. I don't think your car is narrower than my '55 Chevy and the 46" was too narrow for mine.

The backing plate is the wrong place to measure. Just like working with wood, measure twice (or more), cut once. :D

I like the tires to track fairly even with the fronts. It looks better and the tires fit better in the wheel well. Also, the wide-track worked for Pontiac. :p



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Just like working with wood, measure twice (or more), cut once. :D


Now someone tells me its measure twice cut once, no wonder I have so many pieces of scrap....I mean uhhhh "pre-cut" pieces lmao. ;)

back to the OP......I do all early Ford spindles and have found it is much better to measure hub to hub with your new wheels in place. As previously mentioned they don't look as good when they are sucked in by going to a narrow wheel. Also depending on the spindle some vehicles have a different spacing from king pin c/l to wheel mounting surface. Even using aftermarket brakes can change the dimension some. Wilwoods were notorious for pushing wheels out up to 5/8 of an inch. Not good when you may already have clearance issues.
I measured my fender width outside to outside on my car, as I wanted my tire sidewalls to be even with the fender edge. I then took the tires and wheels I wanted to use and set them up inside the fenders and measured them from outside edge overall side to side, and moved them until that measurement matched the overall width of my car's frontend sheetmetal. Once I had the tires sitting exactly the width I wanted, I then measured inside to inside on the mounting surface of the wheels. That's the measurement I went with.
Since the Speedway axle is 8.5" hub to hub, plus king pin width, that's how I came up with how wide my axle should be. Unfortunately, the narrowest axle Speedway has was 5.5" too wide, so I ordered it and cut it down 5.5" before it fit my car's width.
...I like the tires to track fairly even with the fronts....
Oops! I meant 'I like the front tires fairly even with the rears'. The picture showed what I meant.

1946Austin, that's a good way to measure, too. It is probably more accurate for the desired final result.

So much good info here.

Lots of great info for sure! I like where my wheel sits in the fender in stock position, so I want to get as close as possible to that. I measured today with the wheels off mounting surface to mounting surface and it was 57 1/2" I'm gonna order the 50" axle putting the hub to hub measurement @ 58 1/2" which is close enough for me. Custom length axles are an extra $100, 1" will not change the look too much and I shouldn't have any clearance issues and I can spend that $100 somewhere else... Oh & sorry about the picture problems, I'm still trying to get it taken care of.
I'd do the same thing. I know that saving a few bucks here and there makes me feel better, especially if it doesn't make a real difference. I went disc brakes for that reason; they were cheaper than drums on the Speedway kit. I know they don't look traditional gasser, but they work better, and they saved me money. :)
I'm not here to promote myself, but I hate seeing everyone jump on the Speedway bandwagon. I build custom straight axles for 245.00 to any length you want, about a week lead time (I try to machine several at once to save setup time) We use 2" od x .250 wall USA made DOM tubing and I weld each one myself. I guarantee the work is way nicer than the speedway axle. We also can fabricate custom brackets if needed on our CNC plasma table. I have built hundreds of them and quite a few of the cars you see in Gasser Wars and Gasser Magazine have our axle. If you buy our axle you also get our tech help.
Coupebuilder, I agree with your "Speedway bandwagon" statement. That is partly why I went with a '59 Chevy truck axle under my 55 Chev. When I do my next one though, I'll more than likely be calling you.
Well I wont make any apologies for buying the Speedway kit. I hear people complaining about Speedway, and I've had nothing but good experiences with them. Many companies build very fine straight axles, and competitively priced too, but the Speedway axle and kit is a fine product, and complete down to the smallest part.
For those of us who don't have the experience or knowledge to put together all the parts needed to complete a straight axle, it's a viable option. I've done 3 other axle cars using 55-59 Chevy truck axles, and they also work excellent, but none of them worked out as well as the Speedway axle in my Austin did. The Speedway axle I bought was surprisingly heavy, and once I cut and narrowed it to fit I found out why. It's 3/8" wall tubing, which is a bit heavier than most, but I'm sure it will hold up for as long as I'm alive and own my car.
Coupebuilder, I'd be interested in what your company provides in the way of complete kits also, as I like options. If you have something similar to the Speedway gasser axle kit, with disc brakes and all the hardware for the $800 price that Speedway sells their's, then please let us know.
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Coupebuilder, I'd be interested in what your company provides in the way of complete kits also, as I like options. If you have something similar to the Speedway gasser axle kit, with disc brakes and all the hardware for the $800 price that Speedway sells their's, then please let us know.

If you had a complete kit compairable in price I would be interested. Because I'm willing to bet you would be more informative in the TECH support end. I also lack experience when it comes to setting up suspension & steering... this is a kinda learn as I go process, not always the easiest way but don't really have a choice. "Speedway Bandwagon" , I didn't realize there were that many guys runnin' the Speedway axle setup, well least it makes me more confident in my purchase, because I haven't read any bad reviews & they must perform pretty decent too. BTW, are the Speedway axles made in the USA?.... I doubt it but would be nice to know.
Gentlemen, don't get me wrong. I'm not putting down the Speedway kit at all. Its just that almost every car that being built, and every car you see is running a Speedway axle kit. To me it's like going to a all Corvette show, after seeing a few they all look the same. Looking under a car and seeing what axle they chose, how they set up their steering, what they used to mount the axle, basically how they engineered it is what interests me.
But, I realize the bottom line is fittment, drivability, owner/installer skill level, safety, and wallet size are the things that should determine your choice of axle. The Speedway axle is a fine kit, I just feel that people in general don't realize that there are other options or take the time to think a little outside the box.
Sorry for the rant, this is just my .02cents....
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I did look at other axles prior to doing the Speedway. None of the donor axles were even remotely close to the width I needed, which was 52" to the outside edge of my tires. My car is so small that I quickly realised I needed to go to an axle that was either custom, or a tube axle that could be safely narrowed.
I then began looking at what could be purchased and would be the exact width I needed without cutting it down. All the makers I spoke to were in the $350-$500 range for a custom width. I then talked with them about the various steering brackets, tie rods, joints, etc. and found that they usually either sent me towards a used source, or a second vendor to buy the rest the spindles, brackets, etc. Often the vendor they sent me towards was Speedway for the rest.
After going through the options, I decided it was easier, cheaper, and less hassle to so to Speedway and get all of the parts as a kit and narrow the axle. I welded two pieces of angle iron on the main tube to retain the kingpin alignment, then cut 6" out of the middle of the tube. After that I got a 12" piece of shaft from a conveyor assembly and pressed it half into each side of the main tube. I left it about .5" apart in the middle and that was welded up to surface and turned down. It added some unsprung weight to the axle, but kept it strong.
Once it was welded up I cut the angle iron off the tube, ground it smooth and installed it under the car with 7 degrees on the king pins. It tracks straight at freeway speeds, and corners well too.
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Texasratrap, I was told by Speedway that the axles are a combination of imported and US made parts. The main tubes and kingpin ends are US made, that's why they offer custom lengths also. (wish I'd known that when I got mine) Some of the various pieces are made for Speedway overseas, while others are US. Pretty much like any new car built today, a mixture of vendors.
Hey guys, first of all by no means am I putting down the Speedway kit. Some of their parts are very good and some are so-so. I buy a few things from them here and there and the service is good and prices not bad. However, when it comes to the axles I have seen piss poor welding on several and when it comes time to get install help there is no one to guide you. I am no expert in every possible vehicle scenario and I will be the first to tell you that if asked. However I have built hundreds of axles and installed dozens of them in various cars from narrow 33 Willys, to Henry J's to T-birds etc. My axle alone is less expensive than the custom Speedway axles and complete kits priced competitively. I am slightly more on complete kits because I only use top quality parts....USA made forged spindles, USA made caliper brackets, USA made springs (not trailer springs) brand new calipers instead of re-man and a killer forged steering arm setup for top steer that I was one of the very first to develop ten years ago. It all but eliminates bumpsteer in most cases and makes a much better look than a drag link angled down at 30 degrees. I can also design any type of bracket you need and weld it on the axle before the king pin bosses, that way it is a 360 degree weld and won't warp the axle. I am not trying to bash anyones setup, just offer a different option than the big-box type stores that have taken over the country. We all look to save a few bucks when possible, me included. But I pride myself on making parts and cars safe and top quality and when your doing 100mph do you really want to worry about whats under the front end? Take a look at our website and you can see some of the cars and parts we build.
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Nice website and nice cars you are building there... That T-Bird Gasser is Awesome! You got my attention now, so how much for complete kit minus the calipers & rotors, my dad is in the parts buisness and I can get these parts for cost.... but would need to know for what year, make & model ( rotors & calipers ) bolt to your brackets & spindles and can you give me a parts list what comes in the kit. I am working on a budget so maybe we can work something out. You can PM me or email me at [email protected]
I understand what you are saying about the big box stores cause my dad works for a small parts warehouse selling to mom & pop owned parts stores that actually still use books to look up parts and are more knowledgeable unlike the 16yr. old working at "O'ReillyZone". I rather spend my money in the Mom & Pop type parts stores where the owners use to be involved or still are involved in some sort of car racing or car building, yeah they're a little more expensive but you don't have to put up with idiots. Hope I didn't offend anyone it wasn't my intentions just been burned too many times.
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Been doin' some thinking & I like the look of the I-Beam over the tube axle. I was in the garage farting around drinking a beer & I happened to look over in the corner of the garage and I totally for got about the stock (no drop) Ford axle I've been holding on to... measuring 51" . So question is, could this be transformed into a parallel leaf spring axle.. I dont want a transverse spring car. I think it would definitely be different cause its not totally straight has a slight curve or am I drunk & it'd be too much trouble...and SH!T Can the whole idea! I do like I-Beam axles over tube, but don't like drop axles.
Converting a transverse spring axle to parallel springs is not impossible, but it would be tough to do.
If you want to use a beam axle, then I'd go looking for one of three donor trucks. Either a Chevy van, Ford Econoline, or '55-'59 Chevy truck.
But remember when you use a donor axle you need to either build your mounts at a height that gives you the correct kingpin angle, or you will have to fabricate shims to adjust the kingpin angle on the axle. You'll need a minimum of 5 degrees, and probably not more than 7 degrees. If you situate the axle under the car and it's not close enough to adjust with mounting alone, then you'll need to also shim the axle at the spring mount to get the rest.
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