Looking for some thoughts on 31" vs 33" on my RS project

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Looking for some thoughts on 31" vs 33" on my RS project

Postby dma251 » Mon May 29, 2017 8:04 pm

I am continuing to bounce back and forth on tire size with my 89 Trooper RS project. It will be my primary deep-offroad rig, and I am planning to camp from it in some nasty, muddy and rooted areas. I want to try the current re-incarnation of the tire of my wheeling youth - the bias-ply Buckshot Mudder, which is now being reproduced in two sizes to choose from :
N78-15 is 31"x9.50-15, and I would mount it to either my stock 15x7 Snowflakes or some galvanized 15x6 steel HD trailer wheels.

P78-16 is a 33x10.50, and I do not have a set of 16" rims laying back in the "parts dept" so I am would go with 16x6" galvanized steel boat-trailer wheels.
(I know it sounds crazy to try those wheels, but they are rated 3500lbs capacity, and that's more than any similar wheel I could find. they are a field-repairable steel I could heat&beat if I had to, and they have the ultimate in anti-rust coating for ferrous metal - hot galvanizing. Also the hands-down homliest function-over-form wheels I could imagine)

I like the gearing of the smaller 31" tires, and with a rooftop tent, I need to try to keep the COG low. I am trying to make this a very comfortable off-road ride, and use high-end stuff to keep it strong and reliable. I have a Warn 8274 for the ARB front bumper, and a 10K synthetic rope rear winch. ARBs, low Revo gears, and lots of underbody protection to keep the tire size and overall height down.

The only positive I can think of with the 33" tires is that it would make getting up over some roots and rocks a little easier and increase ground clearance and the wheel track would be a little bit wider because of the 16"7" wheels.


My thinking is if I stick with the stock 31" OD tires, I will be able to keep the suspension set a moderate 1-2" lift, and focus on things I can do to make the ride really smooth. There are many miles of road where you can travel a comfortable 25-30 mph, but then you find these sudden giant potholes that bounce you into the ceiling. I would rather spend money on improving the stock IFS and keep it reasonable and see how it does off road. I've driven through some really nasty stuff on 31" tires much less aggressive than a Buckshot mudder.

I'm looking for any suggestions you die-hard Isuzu fans can share. I have enjoyed being part of enthusiast-forums in projects-past. I respect the combined knowledge and fellowship of trying to keep these old-dinosaurs alive. I'm looking forward to throwing some serious labor and coin at this RS.
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Re: Looking for some thoughts on 31" vs 33" on my RS project

Postby egagnon086 » Tue May 30, 2017 8:50 am

It sounds like you really want the 31"s, not many here would sway otherwise on a 1st gen. You loose a lot of the ride quality and suspension travel on 33's. At least you have the gears to push 33's. I bet you'd come out ahead in ride quality and cost going with 31s. besides with the winch you really don't need the most ground clearance.

From the pic it looks like you have 15" "Snowflakes", Why not use those? They will hold up to abuse.
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Re: Looking for some thoughts on 31" vs 33" on my RS project

Postby paulevans76 » Tue May 30, 2017 11:40 am

If it was a LWB I'd say you definitely want as much ground clearance as you can muster, as they are prone to high centering due to a low breakover angle -- not as much of an issue with the SWB. BUT with the 4.77's and the lighter weight vs a LWB, I don't think you'll have as much of an issue with power on the road. I mean, you'll downshift in hills more, but if it's an offroad only/mostly rig, eh, you have the low range gears, it won't be a big deal.

Another thing to consider is that with a 33 you will be at the limit of what most of the components will put up with. Steering components, CV's, etc don't last as long with heavy wheel/tire combos and lots of traction. But if you don't expect to be binding up or bouncing through high-traction obstacles, you should be able to make stuff last pretty well. Just have to drive with that in mind. A 31 on an aluminum wheel will be much lighter, but you loose an inch of ground clearance, so it really depends on the terrain and driving style.

Making them fit is no big deal. Just takes a little sledgehammer finesse clearancing the firewall, body seam, etc.
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Re: Looking for some thoughts on 31" vs 33" on my RS project

Postby muddingrodeo » Fri Jun 16, 2017 4:36 pm

You will always have to trade some things for others and I was in the same boat until I decided to go to the junkyard and buy another set of rims.
I installed fat 33" on the yard rims, now I have both options of wheels.
If I need to make a long trip and pull a trailer I put on the factory tires, If i want to go mudding I slap on the big tires and off I go.
98 Isuzu rodeo 4x4 4" lift 32" tires all black ( mudding truck)
98 Isuzu trooper 4x4 4" lift (fixing transmission)( got this one fixed finally and running on 33" tires)
02 Isuzu trooper 4x4 parts car( or may fix up)(my kid wanted this one so its being fixed)
Yamaha Kodiak x 3 (the kids like mud too)
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