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#1002987 - 12/31/17 05:03 PM Re: 2017 R1200RT Stability [Re: dirtrider]  
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workin' them angels Offline
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Originally Posted by dirtrider
Originally Posted by Bernie

Thank you for the correction and info, I somehow remembered something around 60 or so.
Is there somewhere a table or chart that would tell me what the pressure would be at different temperatures?
Will the moisture percentage mess that up?


Afternoon Bernie

Yes, there are a number of PSI per degree (F) or (C) charts but the easy way to remember it is "about" 1 psi change per 10°f of (tire) temp change (so 40 psi @ 68°f would be 41 psi @ 78°f)

Moisture content will effect it slightly but so little that you won't be able to measure it with a common gauge or TPS sensor.


[Linked Image]


Brilliant! Thanks DR (and a chilly Good Morning to you!) With several TPS systems in use between many of us, it can get a little confusing for a simple Hoosier trying to keep all these numbers straight. I remember trying to explain to Jerry how his TPS conversion worked on his 2015 RT will little success - and I even used small words. Conversely, I have the FOBO system and it allows you to toggle between actual current PSI and the 'adjusted' psi based on ambient temp.

Having a simple rule of thumb is great and I predict this info will shorten many a coffee and lunch stop discussions on tire temps and the like.


Dave
06 R12RT

The point of the journey is not to arrive...
#1002992 - 12/31/17 06:06 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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Here's a thread that goes on quite a bit about tire pressure temps, ambient temp, and TPM's. I think the bottom line in this thread was to follow the advice in the manual and make sure you set the pressure you want with the tires cold, regardless of the current ambient temp.


'16 R1200RT
#1002994 - 12/31/17 07:05 PM Re: 2017 R1200RT Stability [Re: Bernie]  
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roger 04 rt Offline
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Originally Posted by Bernie

Terry, The reason I use 60 F Degree as an ambient temperature to set my cold tire pressure, is because the BMW computer or what ever it is that converts the tire pressure readings of TPS on the bike into the readout in the dash, adjusts those pressures to a cold tire temperature setting of 60 F Degrees. So if I adjust the pressure to 40 PSI at a ambient temp of 40 F, it will as a low pressure on the read out, while the sam cold tire at 80 F ambient at 40 PSI will read high. A little confusing and twisted.
Yes, I actually have by default my tire pressures displayed and with in a few miles the readings stayed between 39 and 41 psi for the front tire and 41-43 for the rear tire.
I have no clue how I will be able to check and adjust my cold tire pressure, once the winter is over, as then the temperature in my garage will be between 80 and 110 F. But I think I will just do what I always do and check and set them for the coldest morning temperature of the week and do it before the sun warms up the tire. We will find out how BMW will adjust to the warmer then average German temps, I just hope it doesn't void the warranty. LOL :-)

By the way Roger what is your tire pressure read out telling you as you ride the bike?


The TPM display is showing my desired (target) pressure. The manual explains how to do it. Take the bike for a ride, note the pressure. Say the display said 36 but you want 38. You need to add 2 psi. Then measure with your gauge. It reads 39. Add two psi to 41 psi. Go for a ride, the display shows 38 psi. A little convoluted but it works perfectly and is always with 1 psi later, cold or hot.

Last edited by roger 04 rt; 12/31/17 07:06 PM.
#1003045 - 01/01/18 11:51 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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Paul De Offline
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Dave,

Being -10F here today, it's good to know that 43F and 49R works for all temperatures below 0F. A lesson learned as a teenager was that messing with tire pressure when ambient temperatures are well below zero is fraught with peril. Moisture in the compressed can very well freeze the tire valve open and a low tire becomes a flat tire

Last edited by Paul De; 01/01/18 11:52 PM.

If the good old days were so damn good, why did we bother to invent modern times?

Most missed bike: Bultaco Sherpa T 326
#1003051 - 01/02/18 04:54 AM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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workin' them angels Offline
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Happy New Year one and all.

Hey Paul - you have us Hoosiers beat by a whopping 5 degrees or so. Obviously, I didn't make the chart, so - as those who know me best already know- "I know nothing". I apologize for posting the chart - i thought a visual might be helpful, but I don't want to sidetrack the discussion. Happy to discus tires, pressure etc in a separate thread if someone ends up starting one.

While frigid here, I came very close to riding today - but just too much snow/ice scattered around.


Dave
06 R12RT

The point of the journey is not to arrive...
#1003056 - 01/02/18 01:17 PM Re: 2017 R1200RT Stability [Re: workin' them angels]  
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It was a joke actually. Maybe I was a bit too dry in my humor and there is no way would I ride at this temp unless there was some very compelling reason to do so. The chart is awesome and confirms the 1 PSI for ever 10F rule of thumb at reasonable temps and pressures of interest. If I ever find myself riding to Dawson in winter...Ok, leaving the snarky comments alone

Last edited by Paul De; 01/02/18 01:30 PM.

If the good old days were so damn good, why did we bother to invent modern times?

Most missed bike: Bultaco Sherpa T 326
#1003071 - 01/02/18 04:13 PM Re: 2017 R1200RT Stability [Re: Paul De]  
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Morning ___

Just keep in mind that Bernie asked "Is there somewhere a table or chart that would tell me what the pressure would be at different temperatures?" he didn't ask at what temp you should stop adding more air.

That tire inflation chart stops at 0°f so the tires don't end up being inflated over the max tire pressure rating as they come up to operating temps not because the universal gas law changes at 0°f.


D.R. ___
Sent from my rotory dial wall phone!
#1003074 - 01/02/18 04:56 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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Back to my original issue, which I’ll now describe as weaving (as opposed to wobbling), meaning that the handle bars don’t move but the bike turns left right left right briskly as if I was throwing my weight around. It happened at speeds around 35-40 mph (neutral throttle, never when accelerating) and also at 75+.

Originally my front tire was 34-35 psi. (I wasn’t smart enough to use the TPM before adjusting and I lost a bit of air.) and the rear tire was 44 psi. Last week I adjusted the front to 39/40 psi and the rear to 42 psi. The tendency toward weaving was better, nearly gone.

I’ve been out riding several move times since, and decided to see what would happen if I lowered the front pressure to 36 psi but ended up at 35. I went for a ride and pushed the bike a bit and now have wear on two-thirds of tread surface. I detected weave only once (in a quick turn) and it was slight.

I’ve ruled out that I’m imagining this, wink but not fully ruled out that it’s just me interfaced to the bike. Is it possible that the tires are behaving differently as I’ve scrubbed them up?

Edit: I have also run the spring preload setting from one rider to two with gear a couple times to make sure it was in the correct position. At full preload (two with gear) but just me (200#) the bike feels a touch less stable.

Last edited by roger 04 rt; 01/02/18 05:00 PM.
#1003075 - 01/02/18 05:08 PM Re: 2017 R1200RT Stability [Re: roger 04 rt]  
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dirtrider Offline
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Originally Posted by roger 04 rt
Back to my original issue, which I’ll now describe as weaving (as opposed to wobbling), meaning that the handle bars don’t move but the bike turns left right left right briskly as if I was throwing my weight around. It happened at speeds around 35-40 mph (neutral throttle, never when accelerating) and also at 75+.

Originally my front tire was 34-35 psi. (I wasn’t smart enough to use the TPM before adjusting and I lost a bit of air.) and the rear tire was 44 psi. Last week I adjusted the front to 39/40 psi and the rear to 42 psi. The tendency toward weaving was better, nearly gone.

I’ve been out riding several move times since, and decided to see what would happen if I lowered the front pressure to 36 psi but ended up at 35. I went for a ride and pushed the bike a bit and now have wear on two-thirds of tread surface. I detected weave only once (in a quick turn) and it was slight.

I’ve ruled out that I’m imagining this, wink but not fully ruled out that it’s just me interfaced to the bike. Is it possible that the tires are behaving differently as I’ve scrubbed them up?

Edit: I have also run the spring preload setting from one rider to two with gear a couple times to make sure it was in the correct position. At full preload (two with gear) but just me (200#) the bike feels a touch less stable.


Afternoon Roger

I guess we should have asked this earlier-- Is JUST the bike weaving with bars holding still or does it feed back into the handlebars & cause those to move (or you can feel a change in bar resistance in cadence with the weaving)?


D.R. ___
Sent from my rotory dial wall phone!
#1003077 - 01/02/18 05:16 PM Re: 2017 R1200RT Stability [Re: dirtrider]  
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workin' them angels Offline
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Originally Posted by Paul De
It was a joke actually. Maybe I was a bit too dry in my humor and there is no way would I ride at this temp unless there was some very compelling reason to do so. The chart is awesome and confirms the 1 PSI for ever 10F rule of thumb at reasonable temps and pressures of interest. If I ever find myself riding to Dawson in winter...Ok, leaving the snarky comments alone


Paul - Sorry, it went right over my head - which again shouldn't be surprising. computer dopeslap One of the nice things about this site is that we can joke with one another. One of the reasons I didn't quite get it was that I'd been having a side conversation about ambient tire temps and the effects Full Moons, ocean currents, artificial hips and chasing Bernie have on tire pressure. AND Universal Gas Law. Frankly, it - like so many things - went mostly over my head and left a fine Southern Gentleman to give up on making his point and instead opted to send me chasing my tail as he claimed my GPS included a volt meter. wave computer

The silly reason I would ride if the roads allowed is that I've not been able to for the last Month, so that itch is getting a bit distracting. thumbsup read bike I've been putting off some electrical work on the bike hoping to ride a little, but its going to be a week before we see temps above freezing here, so I might as well start playing the Wichita Lineman burnout spittake





Originally Posted by dirtrider
Morning ___

Just keep in mind that Bernie asked "Is there somewhere a table or chart that would tell me what the pressure would be at different temperatures?" he didn't ask at what temp you should stop adding more air.

That tire inflation chart stops at 0°f so the tires don't end up being inflated over the max tire pressure rating as they come up to operating temps not because the universal gas law changes at 0°f.


Thanks for pointing that out, D.T. My thinking went along those lines after Paul mentioned the static psi pressure - I'd failed to look that closely at the chart and didn't notice that when I first posted it. But that makes perfect sense (to me anyway)!


Mongo is only pawn . . . .


EDIT: Roger: Sorry our posts overlapped.




Last edited by workin' them angels; 01/02/18 05:28 PM.

Dave
06 R12RT

The point of the journey is not to arrive...
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