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Offline john348

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Thoughts on pressures
« on: July 10, 2014, 02:56:07 pm »
When I had a new front fitted end of last week I stayed and helped and when the mechanic came to fill the tyre he said "I suppose 42PSI".  I said no it was more like 36.  He pointed out that other heavy sport tourers were more like 42.  He is an ex racer and works on lots of race bikes as well as more 'normal' ones.  He also looked at the old front tyre and thought it showed minor signs of being under inflated (possibly a bit of cupping either side of the centre line.  I was happy to play with pressures so we agreed on 40 PSI and I would try it. 

I have now put about 300 miles on it with the new pressure.  First thing to notice is that at the end of our road there is a right angle right bend followed immediately by a give way onto a very main road.  So it is taken slowly.  I have always found the bike handlebars 'drop' into the corner and take quite a pull.  If this happens on any of my other bikes it means the front tyre is a couple of pounds down (I do check them often honest).  It is very consistent with just 1 to 2 pounds being enough.  With the new pressures the TTSE does not now drop into the corner.

Secondly I have noticed quite a bit of white lining in a village, I drive through just about every day, where they have put a chicane for traffic calming and you have to cross the white line before and in the middle of the chicane.  I now do not get any white lining.

I know Mr Triumph has spent a lot of time and money and shold have chosen the presures for a reason and I will probably go back to "proper" pressures to see if the very slight symptoms come back.  But I thought it was worth discussing.

Offline janfmiller

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Re: Thoughts on pressures
« Reply #1 on: July 10, 2014, 06:45:59 pm »
When I had PR4's mounted the shop, who specializes only in cycle tires, said the same thing, he saw cupping, thought from under-inflation, and recommended trying 38.  so far, after about 3000 miles they look fine.   

He also asked that I use the TPMS 'only as a warning system' and to check tire pressures manually with a known accurate gauge, as any TPMS from any source is often less than perfectly accurate...
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Offline donmoe

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Re: Thoughts on pressures
« Reply #2 on: July 10, 2014, 08:44:24 pm »
With nearly 57K miles on it now, I too have found that my Trophy handles better on Michelin PR3s (or PR4GTs when I can get them) with 38 front and 42 rear. The higher pressure makes the ride a bit firmer on rough roads, but the handling seems more precise.

After the tires heat up, the TPMS readings both show about 5 lbs higher, also depending on the ambient temperature. Thus I check them only in the morning with a digital gauge. There seems to be some seepage over several days.

    Don
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Offline w8d4it

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Re: Thoughts on pressures
« Reply #3 on: July 10, 2014, 10:24:58 pm »
I've stuck with 36 and 42 for a couple of reasons.  First and foremost is that I doubt any measuring device in accurate enough to discern a  1 or 2 pound difference.  Certainly when my fancy dancy pressure gauge reads 36 and 42 my Trophy reads 38-39 and 43-45.  So which is correct?  Secondly and probably just as important is time of the year.  In this Texas heat these roads take a fully warmed up tire to (at least according to the Trophy instrument panel) 41-43 front and 48-51 back.  I get uncomfortable seeing tire pressures at 50 and above.  So I keep the starting pressures lower.  Truth be told I see no difference in the handling or the wear.  But to each their own.    Certainly I see nothing wrong with experimenting with tire pressures...within reason.
« Last Edit: July 11, 2014, 01:05:51 am by w8d4it »
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Offline donmoe

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Re: Thoughts on pressures
« Reply #4 on: July 11, 2014, 12:47:44 am »
w8d4it,

I certainly appreciate your conservatism regarding the tire pressures. When I was touring on my 2010 Concours-14, the tire pressures as recommended by Kawasaki were 42/42. Its TPMS seemed to have been temperature compensated so that the readings would remain close to those values. Doubtless the internal pressures were actually several pounds higher after a lengthy run on hot asphalt.

On my Trophy, I noticed immediately that as the tires heat up, the pressure readings on the TPMS rise also, thus indicating that the sending units are not compensating for the higher temperatures. Additionally my rear TPMS sender warns of low pressure when it is at 38-39, but then clears the warning when the tire warms up and the pressure is 39-40 or higher.

Although the difference in pressure seems insignificant, I do indeed notice a difference in how the bike handles going into curves. With slightly low pressure, presumably in the front tire, the bike seems to want to fall into the curve and I have to hold it back to maintain the line. It's not a lot, but enough to feel. With the tire pressure I have now, the bike seems to hold the line through the curve without tending to fall into the curve or straighten out. Obviously this is somewhat subjective and doubtless varies depending on road surface, loading, wind, etc.

       Don

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Offline john348

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Re: Thoughts on pressures
« Reply #5 on: July 11, 2014, 03:59:04 pm »
W8d4it I totally understand the heat issue.  Mine tend to rise by 5 PSI (as said above) when warm but that is warm over here.  Although they are predicting 30 degC next week  :156: and the time I feel it drop just like donmoe says is when the tyres are cold.

As said I have done quite a few miles now on 40 front and actually like it no hint of understeer and quite stable on fast corners.

Thanks for comments

Offline w8d4it

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Re: Thoughts on pressures
« Reply #6 on: July 11, 2014, 04:17:32 pm »
John348, you and donmoe make interesting points but Texas (at least in the hot season) my tires are warm by the time I hit the second stop sign.  And by the time I've gone a couple of miles I hit the tire pressures I mentioned in my earlier post.  In other words the only time I see a cold tire is before I start riding.  In the cooler months (such as they are) I do adjust my tire pressure to compensate.
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Re: Thoughts on pressures
« Reply #7 on: July 11, 2014, 09:11:35 pm »
I'll second w8d4it's comment about Texas.  Just went for a short errand across town.  Hopped on the bike at 35 and 41 while it was in the garage overnight, and before I got to my second traffic stop it was at 37 and 43.  Mine will also show low pressure warning at 38-39 if it is slightly cool overnight (for Texas this time of year that means less than 90 F.),  I've been pressuring them up cold at 36 and 42 during the day if I haven't ridden it, and it is about 1-2 psi lower early in the morning.  I'm afraid if I put full pressure in them at night it may end up at 41 and 48 or so during the heat of the summer here, and I would prefer not to run them up there.
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