1984 720 MH tire question

[ztome]

Hello I recently picked up a 1984 720 motorhome. The dually's are dry rotted and am trying to figure out what tire options I have. The size on there currently is 27x8.50r14. Can I go smaller? I'm new to this so I have no clue , but it seems the clearance between the tire and wood is so close. Is this normal?

 

Would something like this fit? https://www.walmart.com/ip/TRAILER-KING-ST-2-ST215-75R14-LRC/143333506

 

Thanks

[weldingrod]

Could be springs are tired and need to be re-arced. A cheaper method would be to add a couple more leaves.

 

Have a set of dually rims here if you need spares.

[ztome]

26 minutes ago, weldingrod said:

Could be springs are tired and need to be re-arced. A cheaper method would be to add a couple more leaves.

 

Have a set of dually rims here if you need spares.

Thanks. It only has 50k, but maybe the age has gotten to them. I was thinking maybe smaller tires would help a bit too? 

[datzenmike]

E78 14 is what's called for. That's 205/70 R 14 or just over 8" wide X 25.3 tall. This is from the '84 Nissan FSM

 

27" tall is way too much and the 215/75 R 14 isn't much better at 8.45" wide and just under 27" tall. Both are over 2.5" taller than what's called for. You speedometer must be way out.

[ztome]

3 hours ago, datzenmike said:

E78 14 is what's called for. That's 205/70 R 14 or just over 8" wide X 25.3 tall. This is from the '84 Nissan FSM

 

27" tall is way too much and the 215/75 R 14 isn't much better at 8.45" wide and just under 27" tall. Both are over 2.5" taller than what's called for. You speedometer must be way out.

 

Thank you for that info. No wonder there's no room under there lol. Do you think these would work? https://www.walmart.com/ip/Freestar-M-108-Radial-Trailer-Tire-ST205-75R14-C-6-Ply/55346788

 

Or 

 

https://www.walmart.com/ip/Set-of-2-New-Heavy-Duty-Trailer-Tires-ST-205-75R14-8PR/199425824

https://www.ebay.com/itm/2-New-Trailer-Tires-ST205-75D14-2057514-205-75-14-F78-14-VR383-Bias-6PR-/142049856452

 

Also my heater fan blows, but no heat. What would be the first thing to check? I see some hoses capped off, maybe that's the cause? Do you think I will gain a few mph with the proper tires on there because its struggling to get past 50-55. It looks like it has a new carb, and was starting/idling/running rough when I picked it up. I turned the idler screw counter clockwise a turn and that seemed to help a bit. Any other things I should check?

 

Thanks a lot!

[Crashtd420]

The only thing that bothers me about your tire choices is your looking at trailer tires.....

I dont think they are they the same as a regular all season tire?

I could be wrong but you might wanna make sure they are ok to use

[datzenmike]

Larger diameter tires may increase your mileage but the engine works harder to turn them. E78X14 are the correct tires. You want to be sure they match the fronts as well or replace them also.

[MaxChlan]

4 hours ago, Crashtd420 said:

The only thing that bothers me about your tire choices is your looking at trailer tires.....

I dont think they are they the same as a regular all season tire?

I could be wrong but you might wanna make sure they are ok to use

I was thinking the same thing. IMO tires are something you don't cheap out on. General Tire makes good ones. A "good" tire to me is one where the siping goes the full length of the tread, not just halfway like some models or manufacturers. 

[ztome]

4 hours ago, Crashtd420 said:

The only thing that bothers me about your tire choices is your looking at trailer tires.....

I dont think they are they the same as a regular all season tire?

I could be wrong but you might wanna make sure they are ok to use

 

That's what I'm wondering as well. Trailer or passenger tires?

[Crashtd420]

My vote is for correct tires for the application.... quick search and they are available for the size you want, but be careful the 205/70r14 does seem to be a trailer tire..... make sure you check the notes to see exact specs on the tire....

Load and speed ratings and application.

They have websites to compare tire sizes.....  

A 190/75r14 is close and I saw a bunch of good all season tires in that size.....

 

[Stoffregen Motorsports]

Trailer tires have different internal construction which makes them track straight well. They are definitely not recommended for use on a vehicle.

 

Adding a leaf is a great way to regain suspension height after years of sag. Air bags are also a great way to get the ride height correct. I use air bags on pickups where the loads vary, but on a motorhome, the load generally stays the same, so adding a leaf AND installing airbags is probably the smart way to handle this situation.

[ztome]

Thanks everyone. Is a 91 load index ok? 

[ztome]

Also anyone know the leaf size?

[datzenmike]

2WD

1,200mm by 60mm wide by 7mm thick. There are two of these leaves, but the top one has the round eyes for mounting the one under is slightly shorter. Under these two is an overload spring that is shorter still but 60mm wide and 13mm thick.

 

Without any load on it, if you measure down from a line drawn through the shackle holes to the top of the leaf pack it should be 6.34"

 

 

[Stoffregen Motorsports]

I would bet that the shop that performed the camper conversion also upgraded the leaf springs.

 

This website has a lot of good info on stock leaf springs - http://www.stengelbros.com/suspension-springs/leaf-springs/light-medium-truck-leaf-springs/nissan-truck-leaf-springs/pickup-leaf-springs/

[Charlie69]

On the drivers door jamb should be a sticker that list stock tire size.  Be careful of the tire load rating with this being a motorhome.

[wayno]

The motorhome was not built by Nissan, the truck was likely a cab/chassis and then motorhome manufacturing facility did what they needed to fit the motorhome structure to the chassis.

They put these weird overload helper springs on the existing leafs which in my opinion are a joke.

Now I have a Nissan dually axle under my 521 work truck, I have hauled massive weights with my truck, now I am not saying I should have done what I did, but when I stripped my roof maybe 4/5 years ago I rolled over the scales at 7200lbs, my truck weighed 3400lbs at the time, so at that time I had 3800lbs loaded on the truck, and I had four P195/75R14 tires on the back, each tire was rated for 1500lbs, so that is 6000lbs, I still had brakes, I have hauled way more in the past and didn't have hardly any brakes.

I would run passenger vehicle tires on your motorhome, they make light truck radial tires that will work for your needs.

Keep in mind that my work truck has 2 extra leafs in each leaf pack(on each side), coil over rear shocks, and overload air bags, my truck is made to haul weight, I had power steering, and 1990 Hardbody V6 dual piston caliper front disc brakes at the time, a few years ago I fabricated power brakes.

Any reputable tire store should be able to fix you up with the proper tires, as for the leafs you likely have stock 720 leafs with helper/overload leafs added, if they are not there, then someone likely removed them.

Recently I converted my 521 over to a 1986 Nissan 720 cab/chassis frame that came from the factory with a dually axle, it had a dump bed on it since the city of Portland owned it(this information came from the previous owner), I scrapped the 86 cab and put my 71 Datsun 521 cab on it and modified the flatbed I had on my stretched 521 chassis to work with my cab on this chassis, when I did the conversion I transferred every leaf in my 521 leaf pack except the main 521 leaf to the 720 main leaf and it is great, there was no change in my ride, but I did not use the coil over shocks, nor did I install the air bags as I do not expect to haul the weights I have hauled in the past ever again, you can see my truck wood loads in my 521 thread link below.

The tires are squatting a little in this photo, but there is a lot of weight on this truck, them are P195/75R14 tires, I suspect they would work fine but truck tires of the same size would likely be better.

This below was what I had for a suspension before converting over the the 1986 Nissan 720 chassis

[Stoffregen Motorsports]

Yep, air bags.

[ztome]

Thanks "wayno" for the input. Went with these: Westlake RP18 Touring Radial Tire - 195/70R14 91T

 

Before:

https://imgur.com/RlARIik

https://imgur.com/1nfBueW

https://imgur.com/GHh6vVj

 

Suspension:

https://imgur.com/tcfG7JH

 

After:

https://imgur.com/hU21ISK

https://imgur.com/VKa8rpD

 

Anyone know what would make it sputter with low rpm rev and need a lot of pumping when first started?

 

 

[datzenmike]

Lot of pumping when first started cold? Choke not working of maybe set incorrectly causes hard to start and hard to keep running till warmed up.

 

 

[ztome]

Yes, on first start. 

 

I'm new to carbs, where is the choke to check?

 

Thanks!

[ztome]

Hi, I have been experiencing intermittent reverse gear grind when engaging. I don't see a tranny dipstick to check fluid. Where is it please?

[datzenmike]

1/ Look on the driver's side of the transmission about half way up for the fill bung. Usually it has a square hole that a 1/2" ratchet or breaker bar will fit. Remove and you should be able to slip your little finger in and dip into the oil if it's properly filled. It uses GL4 80w90 gear oil. NEVER GL-5. If you don't know when the oil was changed last now is an excellent tine to do this. Two liters are needed to fill. The drain bung is on the under side and has a magnet on it to collect ferrous metal debris. Usually it will have a black paste, if it has chunks or ball bearings on it, that's not good. Wipe it off so you can check the last amount of wear at the next oil change in 30K miles. I run a few feet of old garden hose down from the engine compartment and into the fill hole. Get a kitchen funnel from the dollar store and push into the hose. Fill away. When oil spills out you are full.

 

The oil will slow the spinning gears when you clutch to place in gear from neutral. But if you hold the clutch down and very slowly pull the shifter towards reverse and the gentle grinding is continuous it's not lack of oil.

 

2/ Likely the clutch is not fully disengaged and the transmission gears are being turned by the spinning engine. Now this could be a damaged clutch ... as in the disc coming apart, a spring from the disc lodged in the pressure plate diaphragm or the pressure plate broken. But most likely the hydraulic clutch is not working. This could be simply low hydraulic fluid in the master reservoir beside the brake master. Top it up and it will self bleed and be fine. Possibly air is now in the hydraulic line and must be bled out. Top up the master and have extra fluid ready. Have someone depress the clutch pedal several times and hold it down. Loosen the bleeder screw on the slave and let fluid and bubbles out, close bleeder and let clutch pedal up.... repeat till only clear fluid comes out without any  bubbles. Tighten bleeder and that's it.

[ztome]

On 12/14/2018 at 8:13 PM, datzenmike said:

1/ Look on the driver's side of the transmission about half way up for the fill bung. Usually it has a square hole that a 1/2" ratchet or breaker bar will fit. Remove and you should be able to slip your little finger in and dip into the oil if it's properly filled. It uses GL4 80w90 gear oil. NEVER GL-5. If you don't know when the oil was changed last now is an excellent tine to do this. Two liters are needed to fill. The drain bung is on the under side and has a magnet on it to collect ferrous metal debris. Usually it will have a black paste, if it has chunks or ball bearings on it, that's not good. Wipe it off so you can check the last amount of wear at the next oil change in 30K miles. I run a few feet of old garden hose down from the engine compartment and into the fill hole. Get a kitchen funnel from the dollar store and push into the hose. Fill away. When oil spills out you are full.

 

The oil will slow the spinning gears when you clutch to place in gear from neutral. But if you hold the clutch down and very slowly pull the shifter towards reverse and the gentle grinding is continuous it's not lack of oil.

 

2/ Likely the clutch is not fully disengaged and the transmission gears are being turned by the spinning engine. Now this could be a damaged clutch ... as in the disc coming apart, a spring from the disc lodged in the pressure plate diaphragm or the pressure plate broken. But most likely the hydraulic clutch is not working. This could be simply low hydraulic fluid in the master reservoir beside the brake master. Top it up and it will self bleed and be fine. Possibly air is now in the hydraulic line and must be bled out. Top up the master and have extra fluid ready. Have someone depress the clutch pedal several times and hold it down. Loosen the bleeder screw on the slave and let fluid and bubbles out, close bleeder and let clutch pedal up.... repeat till only clear fluid comes out without any  bubbles. Tighten bleeder and that's it.

Thanks a lot for this info, it will help me a great deal.

[Stoffregen Motorsports]

Has this truck been sitting a long time? If so, the clutch could be coming apart, causing the grinding into reverse. It could also be rust or debris in the clutch causing it to drag slightly. If it's just rust or dirt debris, it may work itself loose and clean itself up with use.