T120 - Tire PSI 36/40 feels better than manual's 32/36. Thoughts? - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 10 (permalink) Old 06-17-2019, 02:59 AM Thread Starter
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T120 - Tire PSI 36/40 feels better than manual's 32/36. Thoughts?

Hello and thanks for reading.

Had my break-in service on my new T120 the other day and asked the tech to stiffen the rear preload. He moved it to the middle position from softest (so two increments) and inflated the tires to 36/40 from the 32/36 recommended in the owner's manual. Feels far better to me now in two ways. First, it doesn't bob and bounce like an old bed, which I'm thinking is due to the preload. Second, it takes noticeably less effort to turn in and transition, which I'm think is due mainly to the increased tire pressure (though perhaps preload could impact this as well if the rear is sitting differently — my understanding of this is limited).

And I'll add that I'm just over 200 lbs.

I assume the modest increase in tire pressure isn't an issue. Any thoughts?

Thanks!
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post #2 of 10 (permalink) Old 06-17-2019, 05:18 AM
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Like you o have found upping the tyre pressure improves the feel.of my bike an ST . I will try normal pressure when I replace the rubbish OE tyres.

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post #3 of 10 (permalink) Old 06-17-2019, 06:05 AM
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Modren tyres run higher pressure than the old days, on my 2013 Thruxton I run 41r and 38f better than reconmended pressure and I been running the reconmended pressure in my new Thruxton but going to up the pressure a bit higher and see if it makes a differents as after my ride yesterday found my rear tyre is starting to wear flat in the middle, but I have 11k kms on the stock tyres, the front one is still good.

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post #4 of 10 (permalink) Old 06-17-2019, 09:00 AM
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I'm 170 lbs. all geared up. I've found that reducing tire pressures works better for me, along with a single notch of rear pre-load. Pressures work best (for me) at about 30/34. The book pressures leave the bike a little too skittish, and riding rough. For the riding I do. Your results are guaranteed to vary.

The book recommendation of 32/36 is for operating at maximum vehicle gross weight (MVGR). Most tires will also have a maximum inflation pressure on the side wall. On the T120's OE Pirellis, this pressure is 42 PSI, front and rear, at the maximum stated load.

The best course is usually to play with tire pressures some, looking for a combination that works best for you. When I hit the road for along trip with a loaded bike, then it's the book 32/36. This will reduce side wall flexing and heat build up in the tire.

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Last edited by tsmgguy; 06-17-2019 at 09:18 AM.
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post #5 of 10 (permalink) Old 06-17-2019, 10:47 AM Thread Starter
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Quote:
Originally Posted by tsmgguy View Post
I'm 170 lbs. all geared up. I've found that reducing tire pressures works better for me, along with a single notch of rear pre-load. Pressures work best (for me) at about 30/34. The book pressures leave the bike a little too skittish, and riding rough. For the riding I do. Your results are guaranteed to vary.

The book recommendation of 32/36 is for operating at maximum vehicle gross weight (MVGR). Most tires will also have a maximum inflation pressure on the side wall. On the T120's OE Pirellis, this pressure is 42 PSI, front and rear, at the maximum stated load.

The best course is usually to play with tire pressures some, looking for a combination that works best for you. When I hit the road for along trip with a loaded bike, then it's the book 32/36. This will reduce side wall flexing and heat build up in the tire.
Funny, I looked over both sides of my OE Pirelli Phantoms last night and for the life of me couldn't find a max pressure anywhere, so thanks very much for establishing it's 42 PSI. You mention how lower pressures expose you to greater side wall flexing and heat build up. I presume the benefits are a somewhat more cushioned ride and potentially greater grip if more tire is making contact with the ground through this flex action.

Am I correct to assume that inflating the tires more will result in quicker turn-in (less drag from the contact patch), but also a less compliant ride and less traction (smaller contact patch)?
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post #6 of 10 (permalink) Old 06-17-2019, 12:16 PM
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Tire pressure is probably affecting easier turn-in. The other factor here is increasing rear preload. That raises the rear of the bike, effectively decreasing the front fork rake which has a noticeable effect on turn-in.

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post #7 of 10 (permalink) Old 06-17-2019, 12:55 PM
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The turn in will dramatically improve once you replace the OEM 2x4’s, opps, I mean “tires”. They are truly awful IMO.
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post #8 of 10 (permalink) Old 06-17-2019, 06:19 PM
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Originally Posted by Hookalatch View Post
Tire pressure is probably affecting easier turn-in. The other factor here is increasing rear preload. That raises the rear of the bike, effectively decreasing the front fork rake which has a noticeable effect on turn-in.

Chuck
Preload is the pre loaded tension on the spring, will not change the ride height
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post #9 of 10 (permalink) Old 06-17-2019, 11:42 PM
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Quote:
Originally Posted by shadydaverave View Post
Preload is the pre loaded tension on the spring, will not change the ride height
Preload will usually have negligible effect on the unloaded bike. However when you add a rider slightly over 200 lbs as the OP stated he weighs and he cranks the preload adjusters 2 notches higher as he stated he did it will certainly raise the rear of the bike up.

Chuck
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post #10 of 10 (permalink) Old 06-25-2019, 02:51 AM
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I'm with Chuck here. With the rider aboard, changing rear preload changes the rear ride height, nothing else. It does not make the ride softer or harder. The spring rate and the damping rates are unchanged.

In my experience with Daytona 955i, with a reasonable spring rate and enough low speed rebound damping to control oscillation, the main contributor to ride comfort is reducing excessive high speed compression damping to allow the suspension to react to sharp bumps. Just enough damping to prevent bottoming on the worst of high amplitude, short-wavelength undulations. This requires changing the compression shim stack on the shock piston for a softer one (which is easy to do as part of a Gold valve upgrade). But I ride on the road, not the track. My ultimate suspension test road is Woodenbong to Tabulam in northern NSW.
Armed with this experience, I plan to have the rear shock on my 2016 S3R revalved for less high speed compression damping, although the Ohlins, set to the "comfort" setting in the owner's manual (23 clicks out on the compression damping) is worlds ahead of the stock Showa on the 955i, for comfort as well as performance. In terms of comfort I think just about any other Triumph model's suspension is worlds ahead of the 955i S3/Daytona's.
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Last edited by blacki999; 06-25-2019 at 03:29 AM.
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