The Stovebolt Site Forums The Shop Area Engine Shop Rear End width recommendations

I have a 51 half ton with a stock rear. I plan to install a Tremec 5 speed behind a 1957 235 motor. I need help with recommendations for a rear. My target would be a 12 bolt, but a 10 bolt might work. I want to install a positraction unit as well. I am planning to install the Jim Meyers IFS and have seen a bolt in set of rear leaf spring that claim to lower the truck 4 inches.

Ok, as I measure it the stock axle is 61 inches. Some 12 bolts ar up to 62 inches. I hope to install the widest tires I can fit on the front and then use the same on the rear. I have noticed on a stock truck the tires in the rear seem "set back" further from the fender edge than in the front. What I am trying to avoid is when I install a wider wheel, having the deep inset in the rim. That would mean I need a wider axel I think. Has anybody been through this? Right now the truck is in pieces so I have a hard time measuring tire sizes.

I also plan to switch to 5 lug wheels. I will have to find somone that can build a steel wheel that will take the stock hubcap.

Any advise from others that have set up a truck would be appreciated.

Don't know if this will help but I'm running a 54 w/straight axle, 5 lug disc conversion (CPP) on the front with 235/70/15's on 15X7 rims with 4" back spacing. Theses clear both the stock tie rod ends as well as the upgraded ends by 3/4-1".

On the rear I am running an 88 Camaro 3.42 (62") with 255/70/15 on 8" rims with 4" backspacing. These are a bit close on the inside (box) but with swaybars and near stock ride height they work fine. If I had it to do over again I would go with 15X7's w/4" bs and 235/70/15's all the way around. The 89 Camaro IROC-Z diffs come with posi/discs but most are 3.08.

The Camaro diffs are only 2-5/8" tube diameter so you have to make a strap shim if you want to use stock 3" U-bolts. I have pics in my Webshots" Shoebox album that can give you some idea of the process and the end result. Hope this helps you.

Dave

I agree, that I would use the same size tires all the way around.

How big ar the front disks? I am looking at 11 inch disks and hope they fit under 15 inch steel wheels.

How has the 3.42 rear ratios worked out? I have had about 3.5 in my mind as a good ratio. Yours is pretty close to that.

The CPP 5 lug kit uses GM 11" rotors and GM calipers and they work fine with the 15" rims. An advantage of using the 5 on 4-3/4 setup is that you can use the inexpensive over-the-counter GM rotor/hub/bearing/seal combination instead of the pricey "mail order only" upgrade bearings used in the 6 lug stock hub upgrades. CPP sells a bracket kit that comes with the necessary mounting hardware and special bearing spacers and you buy the rest of the components from your favorite local parts supplier. I'm running drums on the rear with a manual Corvette master cylinder and adjustable proportioning valve. I've found that power assist masters without an ABS system can get you in deep trouble during high-speed panic stops. The downside of the 5 on 4-3/4" conversion is that you are going to have to buy rims to get the 4" backspacing. No j-yard stuff that I could find. However, the selection of 5 lug 15" rims seems to be greater than for 6 lug 15" rims.

Depending on your 5th gear OD ratio, your rear tire diameter I'd use the 3.42 as the low-end R&P ratio. I originally went with a 3.08 IROC-Z posi/disc but it was just too tall. My 54, which has had all the suspension upgrades but still running a straight axle, is most comfortable at the 60-70 mph cruise speed and the 3.08 had me lugging down the engine out of the torque curve at 60 mph. With the 3.42, .72 and 29" tire I cruise at 65-70 mph at 1900-2000 rpms. I can drop down to 45 in 5th and accelerate back up to traffic speeds without a downshift.

Probably the best part of running this ratio combo is being able to get into 4th gear around town from 35 mph up and yet be able to run comfortably in 4th at 60-65 mph. This would make hilly country a non-issue. You could run the numbers for a 3.73. I haven't run into any GM 3.50 R&P's and even the 3.73's are few and far between. The 3.42's are found behind the 2.8's V6's in late 80's Camaros with automatic transmissions. Most of these diffs show very little wear. Hope this helps.

Dave

learn to do a search as there is TONS of info on this subject


http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=013343;p=1#000002

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You really need to decide what size tires you are going to run first.

For instance, if you tires at 10 inches wide, and you want the wheel mounting surface centered in the wheel, and the tire exactly 1 inch inside the fender, you then have some basis to calculate axle width.

I don't recall the exact measurements, but if the distance from bed wall to fender is 12 inches, that would mean the wheel mounting surface on each side would need to be 6 inches outside the the bed wall. If the bed is 50 inches wide, your axle would need to be 62 inches.

My numbers are all ballpark, but if you measure your stuff and choose your wheels and tires first, you should be able to determine what axle width will do exactly what you want.

The next challenge will be finding one the rigth width...

I think that I want to run something like a 235/65-15. I try to watch for articles in Classic Trucks magazine. I then read the spec sheets to see what has been used. I have not tracked it real well. I called Jim Meyers Racing and they said that they can do the stock fron in either 57 or 59 inch width. I measured mine at 59 inches. I guess that the width reduction would allow me a wider tire but I am not sure. It would reduce the backspacing. I linke the webshots that Fla54Chevy3100 has.

For a bolt in rear spring kit I used a TCI kit.

How did you like the TCI kit? That is what I have been thinking that I would use. I know that my IFS will lower the front. I am trying to not build a pavement scraper. But if the front is lower the rear will have to lower as well. It looks like an easy bolt in kit. The hardest part will be determining the proper angle for the spring perches. Without my body and bed on the frame , I can strap the suspension down but it will still be an estimate of actual frame height.

Todd the TCI kit was a problem to fit as the 3600 has a more narrow frame than the 3100 which these kits are built for. Had mine been a 3100 it would have bolted right up. No complaints...

"I hope to install the widest tires I can fit on the front and then use the same on the rear."

Remember TODD M that you have to steer this thing and those wide tires up front make that more difficult. Mine has 235R15-70 and it is too much tire. Paralell parking becomes a challenge. The wife can only do straight line driving and it's her truck. I'd recommend a 195 or 215 as the largest front tire w/o PS.

Dave is right about the wide tires up front. However if you plan on a Mustang II front end with PS you should be OK with 235/65-15.

Thanks for the info. I hadn't thought about the front tire width. I guess I will have to consider that. I plan to use the Jim Meyers (GM spindles)front end with manual steering. So, I will need the narrower tires. I want wider tires out back than 215 I think. I will have to try to find pictures of a truck with 215s all around. I may want something like 215/70s up front and 235/65s out back. I can do the math and figure out what combo will make the outer diameter about the same.

iw ent with chassis engineerings bolt in rear kit.got almost a 5" drop in the rear.kit was bolt in and was pretty much straight forward. i also popped for their rear sway bar that works with this kit.although i havent installed the bar yet everything else was simple.as far as pinion angle if you miss the mark you can always use shims to correct it later........dave