Tyre pressures fully loaded

[Casbar]

To gain some confidence in my tyre pressure gauges, I went to a Halfords Auto Centre, they very kindly checked a tyre pressure on my car with one of their brand new air line gauges (these are calibrated & changed every month). This checked out with a digital gauge I have. I now use a compressor with auto cut out at a pre-set (digital gauge) pressure, then cross check with the digital hand held gauge. The results are usually +/- 0.5 psi, close enough for me.

I have a loe hate relationship with home gauges. Had a Halfords digital which I used for racing, but battery packed up and guess what, you can't replace it. (7 years old). Had a Michelin dial gauge, this stopped holding its pressure so you could read it, and now, won't read on the rear tyre. Have now started using a 50 year old cylinder gauge, which only reads in pounds, that seems to be reasonably accurate and agrees with the TPS. So I will see 

[David.]

Used both the compressor with it's digital gauge, cross checked with the digital hand held gauge on a neighbours BMW X3 yesterday, reset the TPM system & all OK.

[Trealesbiker]

It's 2.5 / 2.9 for me on fully loaded PR4 GT's. (on the intrinsic tyre pressure gauge) I never bother cross checking it with the digital readout at a garage as it's always slightly different. Never had any problems with this. of course, changes in ambient temp and pressures will affect the tyre pressure in any case

[David.]

This is the digital hand held pressure gauge.

[Steve F]

Bigger photo please.....!! ;D

[Noel]

12k is a very high mileage even for a front.  Half that is normal for most.  I think being told to increase the pressure way above the recommended was wrong. The recommendations are given for a reason.  A tyre that deforms after only 2K I would consider defective and you should have been given a replacement.

Well let's see.  Still not to the wear bars at 12K miles.  So I should chuck them at 6K miles because that's what others do?  Tire wear is a function of all kinds of variables including road quality and temperature, riding behavior and so forth.  On that same ride of nearly 10K miles my brother had an FJR w/ the same tires and got 14K miles out of the prior set. 


Next, of course BMW didn't pick a number out of a hat to publish in the handbook.  As with car tire recommendations they likely based the number on a few factors such as perceived handling, ride quality and so forth.  In my car I run the tires to the publish max on the tire, 44psi, to get better mpg.  Handling is fine as is tire wear.  So after BMW publishes their recommended pressure new information comes in--run the pressures at their recommended 36/42--and cupping ensues.  Others note cupping/scalloping diminishes considerably with higher pressure.  Ignore the new information and hold steadfast to the published values?  A michelin rep mentions the 40psi in the front--he has the benefit of hearing feedback from lots of dealers and some riders as well I'm sure.


Could be something was wrong w/ the tire but I have no idea. The identical issue happened w/ PR4GT on the FJR and others on an FJR forum mentioned the same tactic to greatly reduce cupping.  My brother mentioned this when we met the evening of day 1 of a 24D trip together pointing out how much cupping was present on my original PR4GTs w/ only 2K miles.  I never really noticed until he pointed it out, but I do agree a trip back to the dealer might have resulted in swapping in new tires, but by then we were on our way cross country.


I posted about the cupping issue on another forum and here are some replies:



[size=1.4rem]Re: How much cupping is typical for PR4GT on RTLC?[/size][size=17px]
I've got a 2016 with about 3,600 miles with pressures in manual, but I noticed the cupping before (maybe after the first service). I was surprised.



[size=17px]I just took my '15 in for the 12k although I am just over 11. I could easily get a couple more thousand out of the original tires but I'm having them switched to Angel GT's while getting the service done. Mine started cupping in the first couple thousand as well. To my surprise the service writer actually engaged me in a conversation about it stating he had just attended a discussion forum about this very issue. It seems the telelever is in fact the suspect in the RT front tire eating. [/size]
[size=17px]
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[size=1.4rem]Re: How much cupping is typical for PR4GT on RTLC?[/size][size=17px]
I'd bet you're a little low on air pressure if you follow the manual. My manual says something like 32 and 36 and I run 40/42 and don't see or hear cupping for quite a while.





like I said before I run 42 front 42 rear and have no cupping I could care less what the owners manual says




[size=17px]I have a '14 RT with Conti tires running factory recommended tire pressures and noticed cupping at 4000 miles.[/size]
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[/size]
[size=17px]Noel, you are making way too much of the tire pressure, let me explain. All bike manufacturers SUGGEST much lower pressures than the tire manufacturers. The reason for this is that the bike manufacturers are COMPROMISING on best grip, wear,etc..[/size][size=17px][size=17px]The down side of this is that the bike manufacturers recommendations for the pressures are BELOW what the tire should be run at, aka UNDER inflation.[/size][size=17px][size=17px]The result is cupping.[/size][size=17px][size=17px]I always run 40/42 on ANY bike, bumping it up to 42/42 if I detect any odd wear.[/size][size=17px][size=17px]It isn't the beemers suspension, ALL bikes will cup the tires if run at bike recommended pressures.[/size][size=17px][size=17px]That's as simple as I can explain it. Hope it helps[/size]

[guest2360]

Find it hard to believe that manufacturers would deliberately recommend you run your tyres under deflated. But who cares.  I look in the book and accept what it says believing that they know best .Same goes for oil grades and levels and fuel. If I thought they didn't  know what's best I wouldn't have the bike in the first place.

[Noel]

...and accept what it says believing that they know best...

Ahh, you're a man of faith then, steadfast in the face of new information.  May it serve you well. 

[guest2360]

I have to ask why you wouldn't go along with the handbook. It can't all be lies put there so we all destroy our tyres as soon as possible so the dealers can sell,us more.

[Casbar]

I have to ask why you wouldn't go along with the handbook. It can't all be lies put there so we all destroy our tyres as soon as possible so the dealers can sell,us more.

Because as explained above and many time in this thread and others, the handbook is a compromise, I run higher pressure in the front and it works for me.

[Noel]

I have to ask why you wouldn't go along with the handbook. It can't all be lies put there so we all destroy our tyres as soon as possible so the dealers can sell,us more.

Don't forget, I ran the handbook recommended pressures initially, but after very premature cupping ensued I poked around for new information, and so far, it seems to be validated by others.

[guest2360]

20 years on BMWs of various types, probably 120000 miles.  Always run the tyres at handbook preassures.  The only cupping I have ever had was on a 1600GTL. pressures on them is 2.9 front and back and strangely even though the bike is 100 kg heavier than an RT it uses the same front tyre. 

[Casbar]

Over 45 years on different bikes including BMWs and riding professionally and racing. Never blindly follow the recommended pressures, always find the happy medium that works. Handbook is a compromise for people who either can't be bothered to try different things or don't have the nouse to!

[richardbd]

This thread is turing into even more fun than either the engine bars/scaffolding one or the short boots one.


Keep it coming chaps...


:alas: :alas: :alas:

[guest2360]

No I give up.