Best wheel and rim size for SBU435 U1700L?

[Vegard_S]

I'm looking for some new shoes for my Unimog, It's a 1980 U1700L with Om352, 168HP, standard gearing, 8-bolt axles.
It currently sits on Pirelli road tires 13.00 R22.5, on 9x22.5 rims. I want simmilar or bigger diameter on the wheels as the current ones, so that the RPM's on the engine can be lowered when the truck is crusing. Now It cruses at 80km/h at aprox. 2500rpm.


I am considering Michelin XZL in the following sizes:

- 13.00 R22.5, diameter=1130mm, (possible to re-use old rims, + same size as used on many older European trucks and trailers)

- 395/85 R20, diameter=1189mm, (Larger tires, seems to be used on a lot of unimog campers, need to buy new rims)

- 14.00 R20, diameter=1258mm, (Even larger tires that will lower RPM on engine dramaticly at crusing speed, cheap 2.hand tires available from various suppliers, but maybe to big, will they require a cabin lift?, also I would have to buy new 11x20 rims)

I'm also considering various rim options. Prefferably OEM Mercedes solid rims or split rims. If I go for the split rims simmilar to these:
http://www.unimogs.co.uk/our-stock/spares/wheel-rims/set-of-4-8-bolt-20-rims-wh0082
- Will I then have to also instal inner hoses in the tires?

I'll be gratefull for any inputt on the subject!

 

[grizzlyj]

Hi
I had 395's on my U1700 which were lovely.
10"x20" wheels are fine for those or 14.00's. Neither particularly want to seal on the bead when you change the tyres though if you get to that. No tubes required. Split rims mean you can fit fairly easily yourself.
395s and 14's were, I believe, standard Mercedes options on the bigger Mogs like a 1700, no lift required.
14s will present a smaller frontal area when pushing through soft ground, the bigger diameter may give you a slightly bigger footprint when aired down, the actual rolling radius might not be too much different to affect cruising speed rpms significantly. Weight wise for you to fit may be about the same? (B@x8$y heavy)
An overdrive is a better bet for relaxed cruising, and to fill the gap between 7th and 8th IMHO. £$€£$€ And then more bhp (intercooler from AV too?) to maintain that higher speed?
I think 395s look much better though

 

[LostInTheWorld]

We ran 395/85R20 Michelin XZL on our LMTV and we now run 365/80R20 Continental MPT81 on our U1300L. The weight (and rotational moment of inertia) difference between the 395 and 365 is very significant. I think the stopping performance difference would be noticeably worse. I don't think I would go larger than the 365/80R20 on our U1300L.

 

[grizzlyj]

We started out with a 7500kg gross U1300l with 14.5s, then changed to the 11500kg gross U1700 on 395s with the same camper having discovered how heavy it was. The difference in tyre size is massive. Equally, brake size between the two Mogs was equally marked.
I can't remember how much the smaller wheel and tyre combo came to, but IIRC the split rims were 50kg and the 395s 110kg, ish. To pick them up from flat definitely needed a deep breath and a straight back. Moving 14.5s around didn't require half as much effort or caution. Some sort of winch arrangement is needed to get either onto their stored position, maybe I could have used a similar system to move them around more generally, just a chain hoist with a strap thrown over the top of the camper would do. Changing them on tarmac is not easy, on an uneven and sloping surface is hard and needs a plan.
If it's true that sticking with 22.5 wheels means you need a machine to change them, then if you carry two spare tyres perhaps you also need two spare wheels? On split rims maybe you would carry just one spare wheel? But that small weight saving would in no way balance out the additional 395 weight.
Two 395s won't fit mounted horizontally across the back of a 2.5m camper, 14.5s will. So one 395 would either need an entirely different location, or a bit higher up the rear camper wall requiring more fabrication and so weight.
The 395 footprint when aired down is massive.
14.5s are easier and much cheaper to buy new. Ours were Conti MPT 80, very noisy, wore unevenly, but new via AV. 395s were used and much quieter. Now our family is three not two I decided to this time not go with used tyres.
It would be worth checking how much weight 14.5 MPTs can carry, with some available not enough for your truck maybe?
Too many maybes in that lot But, as above 395s look better, especially on a fair sized camper
A slightly weirdly set up web page showing bead seating on 395s. You can also see the inch gap between the wheel and where the tyre bead wants to sit that needs sealing, bicycle inner tube used by some, flames by others. But a Merc approved wheel and tyre size pairing. To the left of the pic click once to go left one pic, there's a link under to play a film of setting light to them with air freshener by some muppet. http://www.moglet.co.uk/page109.html

 

[ScottReb]

Five post and no one mentions the excellent matching G! They both look amazing.

 

[thebigblue]

Five post and no one mentions the excellent matching G! They both look amazing.

We all did that in another of Vegas´ threads

 

[erwin z]

Didn't it already come with the best combination ?

 

[Jostt]

I made the mistake to use , 365 85 r20 on my 1300L ....too big , now whit the 80's profile it is much beter , the 85's whit hutchinson 10' rims are very very heavy , even on the rims , now 11' , the diference on weith is big , 10' looks like reinforced to military aplications, I dont know the diference apart the axles on the stering , but I dont think there is a big diference betwen 1300 and 1700, if not ....The rideability is Much beter on the light wheels ( rims +tyres)

 

[CragMog]

365/85’s weigh 20kg more than the /80. It appears to be in the tread structure and therefore the change in centrifical force is significant. I tried them. Bad move. The U1700L is a stronger, heavier truck with more power and much bigger portals and, most importantly, bigger brakes. My U1300L struggled to stop on the /85’s. I believe the /85’s are the standard for the U1700L. The 395/85 is only 10kgs heavier than the 365/85’s and gives you slightly better top speed.

 

[Vegard_S]

Ok, so the 13.00R22,5 that it runs on today are not intended for anything else than good paved tarmac road. Hence the reason for wanting to change. They are also extremely stiff and have almost none contribution to the suspension when riding on bumpy roads. But since they are only 13'' wide,the footprint is relatively small, hence floating abilities on muddy surfaces become poor.
...But they are quiet, the roll ressistance is low, they are widely used on older trucks and trailers in Europe, and are relatively cheap to buy. The weight is also not so bad.

395/85R20 on the other hand...
Looks better (IMHO ), gives better floathing abilities, will contribute more to make the ride "softer" when traveling on poor roads, since there is more rubber in the tire walls, They are allso quite cheaply available from Vrakking Tires in Netherland.. Donwnside being mostly the need for buying 20'' rims and the extra weight compared to the 13.00R22,5 I have now.

The extra diameter should be enough to lower the engine RPM at crusing speed buy some 100's REV. Brake wise, I don't think it will make any big difference. My truck has the upgraded prake system with bigger discs' and double set of callipers. So blocking of all 4 tires in 85 km/h on dry tarmac is no problem

Hmm, decisions decisions....

 

[Sitec]

Hi fella.

In my view it all depends on how much mud work you plan to do... A wet grassy paddock or soft soil track is 'interesting' whatever you are driving be it a car, fourby or truck... and unless you are running all out mud tyres then there's little difference between a drive axle tyre and an all terrain tyre. My truck had 10.00 R20's originally and they have now gone as they were a general/steer tyre, and hopeless on anything but bitumin. I've now gone with a set of 8 second hand 315/80 R22.5 Goodyear Omnitrac drive tyres on rims (giving me 2 spares) that I stumbled across on Gumtree. This gave me a decent drive tyre all round, didn't cost the earth, and is something that's available world wide. I'm also staying with the rear duals on mine (which is a talking point amongst some but irelivant to you). A lot of money can be easily parted with for a wide off road tyre on a specalist rim that looks good, and is awesome off road, but wears quickly on road, is hard to replace if damaged in a remote location, and puts unnecessary load on a portal hub. I was lucky enough to be a tour guide in Africa for a few years, and the company ran old Merc NG/MK trucks. These were all on 11R 22.5's or similar, and they went everywhere we dared put them (which included beaches, sand tracks, dirt and shale tracks, and on one occasion some very soft 'Black Cotton soil'). Apart from the latter, they never failed, and an aggressive mud tyre in the black cotton soil would have made the matter worse! Really we shouldn't have been there in a 12 tonne truck.. Guess what I'm trying to say is that I'd be slow to go for anything wide, fancy and expensive as realistically 98% of what most of us will ever do is on reasonable roads and or good dirt, with the occasional 'uh oh' track here and there... If you arrive at 'that track' miles from anywhere and traveling alone, you'd be asking yourself "do I really need to go down there in my 10 tonne mobile home"? If you could find a slightly wider drive tyre to fit your rims, buy 4 and use your original tyres as spares... Just my opinion tho. Neil (Cloud 9) is on a world tour in his truck and has been here, there and everywhere... all on road tyres... He'd be a good 'go to' for an opinion on this... Pictured is 11 tonnes of 4x4 Drago truck on cheep tyres doing what they do..

 

[Sitec]

And I've posted this pic a few times now, but here's Aminah (an Ex Drago truck leading a new life in West Africa), deep in the soft stuff but still moving. Tyres..... standard 11R 22.5's...

 

[Roverchef]

For the amount of power you have I think you would be best with 365/80/20's. I've run just about every variation out there and always come back to MPT. Just my $0.02

 

[Roverchef]

And YES on the matching G!

 

[Vegard_S]

Thanx for the input guys! A lot of good thoughts on the subject!
I just did a bargain on some 2. hand 10×20" split rims. So 20" tires it will be. Vrakking tires in Netherland has a lot of demo/like new looking tires, at a reasonable price. So I'll probably end up with some tires from them. Stay tuned for the result?