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mrpye

11.00-20 tyre choice

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Hi all,

I have a douglas Taskmaster tug which I need to get some tyres for, It says in the handbook that it should have 11.00-20 tyres on it, it currently has a 10.00-20 and a 12.00-20 tyre. Question is would a 11.00R20 tyre fit? as there are a pair of those on Ebay at the moment. I've looked into new 11.00-20 tyres and they are nearly £300 each! 

 

Thanks Matt

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As long as tyres are equal size accross the axle should be O.K. Sounds as though the ones you have on at the moment are miss matched It depends on the width of the wheel as to weather the tyre /wheel fit is correct. A 20 inch wheel rim will fit all of the tyre sizes you have mentioned, but a 10.00 x20 will have a different bead fit to a 12.00x20 on the same wheel centre, giving the inflated tyre a different profile. Also a different load/ speed rating.

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Yeah they are mismatched at the moment. I want to get some 11.00-20 tyres. The ones I have found are 11.00R20 though will these be the same as 11.00-20? If not what is the difference? The wheels are split rim type. Thanks Matt

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If it has an R in the description that means they are Radial ply construction. Radial and Cross ply constructed tyres should not be mixed on the same axle. They have different Rolling and adhesion characteristics, also different speed and weight carrying abilityes. Radial and Cross ply have different bead shapes but generally they are interchangable on tubeless and split rim wheels, the internal finnish of the tyre is smoother on a tube type tyre. With split rim wheels it is esential to make sure the locking rim grips its position on the wheel and they are both clean before starting the assembly procedure. If possible use a cage when inflating

Edited by john1950
spelling and addition.

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Ahh thanks, its only for the rear axle so if I got 2 Radials then I should be ok, they are the same ply rating as in the handbook. I had a feeling they couldnt be mixed but wasn't sure if Radials could be used on a split rim or not. Thanks Matt 

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Don't forget that you are stuck with using tubes if you have split rims and that fitting tubes to tubeless tyres is not a great idea.  The tyre sidewalls will be marked tubeless or tube type.

Vehicles such as loading shovels and Foden DROPS use tubeless tyres with a split rim but the outer rim is sealed to the wheel with a large square section rubber ring.

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Not been mentioned so far is that traditional military cross ply tyres such as 11.00-20 are 100% profile so the overall diameter is  20" (the hole) + 11" + 11" (the extra radius of the hight of the tyre twice) = 42"

An 11.00R20 is probably 80% profile (may be almost anything though, and should be marked) and that will be 20" + 8.8" + 8.8" = 37.6" diameter which is a bit different ! This results in a 13.82" difference in circumference or how far you go for one turn of the wheel.

As your vehicle has four wheel drive you must have the same size wheels on all four corners or bad things will happen to the transmission. It is a bit hard to see how issues like speed rating and adhesion qualities are relevant to this application but not destroying prop shafts or diffs is in my opinion

David

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Ahh ok so a 11.00R20 tyre will more than likely lower the top speed a little? The wheels are for the back axle of an aircraft tug, they will be on the rear axle which is driven so propshafts etc isn't a problem, the front tyres are 6.50x16 I think. 

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Ahh, sorry, I had thought that you had a much bigger one with four wheel drive and equal size tyres all round. My mistake !

As you only need to think about the two you have a fairly free choice. One option is the 12.00-20 bar grip tyres that Bedford MKs use. Part worn ones are pretty cheap and good for traction if you are actually pulling aircraft about, plus they are a little bigger so top speed is slightly greater - handy if you are trying to go somewhere.

David

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From my Continental Tyre data list an 11.00R20 is 1082mm outer diameter on an 8" rim which is 42.6" in old money.

The theoretical sizes are often a good way out of the actual, a 10R20 would theoretically be 40" but is actually 1052mm or 41.4".

I have only seen % aspect ratios marked on truck tyres of 80% and under.

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Also different makes of the same size can be different overall diametersand very different tread widths.

David

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I did think about 12.00-20 tyres as it has one on it already but it's very tight in the arch and quite hard to get on and off. Also i may have to put bigger tyres on the front to compensate for the extra height at the back. I have noticed they are easier to get though. I might see how much these 11.00R20 tyres go for on ebay and see if they will work if not i'l look out for some 11.00-20 tyres.

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With tyres the only constant is the wheel size, internal diameter. Overall diameter depends on the tyre makers original design use, type of compound, and tread pattern. Off Hyway, Mixed use, On Hyway, Long Haul or Urban. Steer, Drive,or Lift Axle.Then you get into Pneumatic Specialist Pneumatic, or Solid. I once drove a rig on the docks with a mix of Pneumatic, Pneumatic with tyre fill and Solid on different wheel stations. 

Edited by john1950
correction and addition

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What ever size tyre you choose, if you are fitting them yourself please remember that the first time you inflate the tyre a split rim wheel can blow apart even if you think that everything is in place and this has resulted in serious injuries and even be fatal.

How inflating should be done:-

http://www.hse.gov.uk/pubns/indg433.pdf

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Many truck type radial tyres can be used either tubed or tubeless. This will generally be marked on the sidewall. Split rims (with the locking ring) can be very dangerous if not assembled correctly. Divided rims (which are bolted together) are generally pretty safe when bolted up to the proper torque.

Cheers,

Terry

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I tried 1100R20 for my CMP truck, and they were significantly smaller.  I sold them on without  fitting them.  If you look back in the archives you should find the discussion.

 

My advice is to keep looking - 1100-20 do crop up.

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I re-tyred my Diamond T 969 many years ago with part worn 9.00-20. You would be surprised at the variation in diameters. Even Goodyear made in USA and Goodyear made in the UK were significantly different even though both were all service with a similar amount of wear.

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