Tyre weight limit

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paulwolf
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Posts: 38
Joined: Sun Jun 23, 2013 8:06 pm

Tyre weight limit

Post by paulwolf » Mon Sep 16, 2019 1:35 pm

Having had a good ride, 2 up with 2 panniers & top box from Bristol to the IOM to see the Classic TT on the Commander, one night my mate said have you ever weighed your fully loaded bike against the max load of the rear tyre?I said,no but i did when i got home and this was the out come.
Rider 100 kg
Pillion 91Kg
Top box 13Kg
2 panniers 26Kg
Full tank 17Kg
Weight on rear wheel 139Kg
Total 387Kg
Michelin rear tyre max weight 290Kg
It seems im 97 Kg over weight so will have to look for a rear tyre with increased max weight.Cheers Paul

johnbirchjar
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Re: Tyre weight limit

Post by johnbirchjar » Mon Sep 16, 2019 10:45 pm

Food for thought indeed,J.B.

Clive603
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Re: Tyre weight limit

Post by Clive603 » Mon Sep 16, 2019 11:36 pm

Not convinced your sums are quite right given that some of your weight and most of the fuel tank and tank bag load will be on the front tyre. But it does sound a bit marginal. Especially given that modern tyres in Commander sizes are more middleweight orientated. Not so much in load capacity but more in general dynamic behaviour.

Maybe time to look into the Conti ClassicAttacK radials mentioned elsewhere which the Commando folk seem to be doing quite well with. Encouraging although I'm underwhelmed by the mileages being quoted. Although I've not, and never will, use them I do have some experience with radial tyres on a Commander which may, in a roundabout way, have some relevance.

Not so sure about the 90 section though. I'm now convinced, from experiences recounted below, that the big win with radials is the shallower sidewall which allows everything else to be retuned for better stability, better behaviour and longer active life. With the deeper 90 section sidewall I suspect the changes from ordinary to ClassicAttack tyres are going to be more akin to what happened back when the Avon Venoms and similar tyres came along than the full radial experience. Not so dramatic but potentially well worth having. More a retuning of tyre load capability and dynamic behaviour to suit a different type of machine. If they have got their sums right. As ever the $64,000 question is going to be how well they play with that flexi front fork.

Back in the early 1990’s there was a very definite shift in tyre design in our sizes to suit middle weight machines. Not so much in load carrying capacity but in general dynamic behaviour and natural frequency response. Remembering that tyre is a (very) non-linear and partially damped suspension component its a major league miracle that they can be made to work on a range of quite different machinery. In those days I found scary front end instability issues building up at relatively low mileages and became seriously fed up with throwing away half worn pairs with 5,000 miles on the front and 2,500 on the back, instead of the 12,000 / 6,000 I'd always considered the norm. My favourite Avons were the first to go but nothing really worked for decent mileage on my commuting roads(?). I did try a steering damper (POS £££ "race developed" Ohlins) with, ahem, "interesting" results.

Received wisdom then was that "radial" tyres had to have more flexible sidewalls than the conventional breed and could only be made to work properly on motorcycles at 70 section and below. Not to mention the considerable heat and light surrounding the debate over what actually, in motorcycle terms, constituted a radial tyre as opposed to narrow angle bias belted and too many other press promulgated terms to remember.

Certainly a major reason for getting Richards Supreme Commander rework was my conviction that not only would a proper radial tyre never be made for standard Commander rims but also that normal tyre dynamics would, by design, continue to be unsuitable for standard Commanders.

After Richards modifications my Commander runs a 120/70 ZR17 on the front and a 160/70 ZR17 on the back. Much as I miss the enduro bike in super-tourer disguise nimbleness I have to admit that extra stability is more than a little re-assuring at times. Lord knows how many more miles its gonna take for me to always remember to push the bars a bit harder if it wants to run out in a tightening corner rather than gently ease with the knees Velo (or horse) style. With 150,000 + Velo single miles behind me in long(ish) hair and flared pants days probably never gonna happen.

Interestingly my (second) Yamaha GTS 1000A "funny front end" bike also runs a 120/70 ZR17 on the front albeit with a 170/60 ZR17 on the back. Back when I ran my first GTS alongside a standard Commander the handling, and riding style demanded, differences were profound. The GTS being pretty much a herd of water buffalo and the Commander a ballerina. These days the GTS still retains its liking for truck driver steering inputs and retains the same militant indifference to road surface quality but I can be more relaxed with the Commander due to much greater natural stability. No more need for the hyper aware focus and light touch teamwork if pushing hard on testing roads. Which I sometimes sort of miss. But at 9 stone dripping wet I'm probably a couple of stone or more under the official best weight for Commander pilots.

Clive

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