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  #1  
Old 2 Apr 2009
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Tyre pressures for a FULLY loaded R100gs?

Could anyone let me know what tyre pressures I should be looking to have on my '88 R100gs. Its carrying a pillion, two full 35ltr aluminium boxes, a few tools, tent etc. Not sure of weight exactly but quite a lot! Haynes manual only gives pressures with a pillion (36front 42rear) it doesn't say what to do if you are carrying the equivalent of three or four!
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  #2  
Old 2 Apr 2009
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What tyres? I should stick with what BMW suggest and see how the bike feels
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  #3  
Old 2 Apr 2009
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On the side of the tire they have the max load and pressure.
I would not go over that.
In most tires I see that is 42.
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  #4  
Old 2 Apr 2009
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My r80gs with two up, two large tech panniers stuffed to the max (my missus likes stuff) and a full HPN tank 43 lts we both weigh in total with gear on about 23 stone and I ride front at 36 psi and rear at 42 max I would drop that a bit once on crap roads 32/36 max no real problems so far, I reckon you really need to make sure your rear shock is set up right though. seems to make a huge difference to the handling when loaded up.
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  #5  
Old 2 Apr 2009
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thanks for responses, I've got Metzler Tourance on. Think I'll stick with what is says for pillion and see how i get along.
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  #6  
Old 2 Apr 2009
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My R80-100RT weighs about 270kg at summer and 285-290kg something at winter.
I do not carry a passenger (with very few exceptions).

Front 1.9-2.1kg
Rear 2.3-2.4kg I would need to go up to 2.6-2.7kg if I have a 50-60kg passenger and 2.7-2.9 if I have a 90-100kg passenger.

You need to have someone who can read tire-looks under load to check the apperance of the tires under load...
Or - you do as we were taught at driving-school - put the hand on the tire directly after a ride; cold = too high pressure, warm/hot = too low pressure. Should be "handwarm" - 35-45'C or so if I understood it correctly.

It is better that you run with a bit too high than a bit too low pressure!
BMW manual is -not- correct concerning asphalt surface... they state graveroad pressures(!).
Which brings your question to - you will need to adjust the pressure in accordance to the surface you will be running on and the ambient temprature.

Too low pressure => very sensitive to uneven road surface; the bike uses a full lane or more...

Comparison to my VW Type 4.
Supposed to have 2.2kg... must be an aprils fools joke! I use 3.5-3.7 front and 3.3-3.5 rear. Friend of mine had 3.8-4.0kg front and 3.6-3.8 rear when he drove his T4 as a taxi.
It is the same thing with bike tires - you will have to raise the pressure significantly above factory specs.

The pressure affects, damping, tracking, grip, braking power, wear, and mileage. Too cold or too hot => more wear on highway; off road is a compleatly different issue.
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Old 3 Apr 2009
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maybe more than recommended by BMW

My old BMW F650GS recommended 31 / 34 when 2 up. Fully loaded (me alone and my panniers) it felt like having flat tyres.

When I replaced my rear shock (in preparation for my trip to south america), I was asked by the workshop to come fully loaded. The mechanic there recommended me to pump up the pressure to 34 / 44. At that pressure the bike felt real good at speed.

You should experiment to see how the bike feel but you with pillion and luggag eyou should give a go beyond BMW recommended pressure.

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  #8  
Old 3 Apr 2009
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I run 37.5 PSI front and rear all the time unless I will cover long distances in soft sand.
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Old 3 Apr 2009
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Psi

how much do you runn in soft sand and with wich tires.

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Old 4 Apr 2009
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Quote:
Originally Posted by HendiKaf View Post
how much do you runn in soft sand and with wich tires.
I’m not a big fan of dropping the pressure so I don’t do it before I get stuck a few times. The pressure is dropped multiple times until it works, I don’t use any gauges for this but I don’t like it when the pressure is below approx 7.5 PSI. 3 PSI has also worked…


Mostly I use Michelin T63 or Pirelli MT21.
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  #11  
Old 4 Apr 2009
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Quote:
Originally Posted by AliBaba View Post
I run 37.5 PSI front and rear all the time unless I will cover long distances in soft sand.
37.5psi (2.5bar) seems very high for an MT21 front tyre. I would have thought that sort of pressure would make the front feel a bit skittish.

The Tourance would probably work better on the road with higher pressures and it will heat up less and therefore wear less but reducing the pressures for off road won't make much difference
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  #12  
Old 4 Apr 2009
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Given that my sidecar weighs a lot more than most bikes that might run narrower off road tyres I was looking into all this stuff a while back, to try and widen my choice of tyres with some metric options.

That and the fact that I, too, ran a BMW two up and heavily loaded, athough this was the lardier 1150GS, led to me posting this, so I hope it helps:

I can't comment on the pressure of the tyres regarding the upper limit of normal, other than what is written on the side of the tyre as previously pointed out. However, I will say that, because I did not check my pressures as muh as I should, the weight did make the knobbles on my TKC start to split at their base when the pressure was too low.

The one thing that I will comment on, though, is the weight limit of the tyre, rated by a numerical value. If your bike is as heavy as you claim, I would ride it down to a workshop with scales and measure the whole weight and that over the individual tyres, to be sure that these do not exceed the weight rating of your particular tyre brand.

See what I mean here: in the right hand column.

To give you an idea my rear tyre was supporting about 350kg when we were both on board and fully loaded.
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  #13  
Old 4 Apr 2009
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Quote:
Originally Posted by Magnon View Post
37.5psi (2.5bar) seems very high for an MT21 front tyre. I would have thought that sort of pressure would make the front feel a bit skittish.
In my experience 2.5 bar is the best pressure for general use and the tire will work well in most conditions.

The problem with MT21 (at least for me) is that the knobs next to the center wears out, this increase with lowered pressure. This is mostly a problem if you brake aggressively (typical driving high speed on forest roads) but for desert and touring use it’s the best tire I’ve used.
MT63 doesn’t have that problem but it lacks a bit of grip, it’s also quieter at high speeds.
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  #14  
Old 5 Apr 2009
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The weight of the bike unladen is 220kg, we then have a fair bit of luggage (45kg) and two people (140kg) so a total of 405kg. It doesn't look all that bad, not compared to some I've seen, but it does feel heavy and the front can feel a bit skittish. Is this heavy?
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  #15  
Old 5 Apr 2009
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See if the tyre manufacturer has a website and whether it lists recommended pressures. I know Metezler do.
Bear in mind they are probably the only people who can be sued for misinformation as anyone elses opinion is just that, an opinion. That's not to disparage anyones opinion.
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