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tyre pressure in PR4s?

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Does anyone know what the recommended pressure is for michelin pr4s on the nc750X- would it be the same as that stated on the swingarm for the dreaded dunlop trimax tyres?

Cheers Tony

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Tex

The 'official' pressures are 36psi front and 42psi rear. Some users (myself included) reduce those by (up to) 10% when riding solo.

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Mike5100

..... and by 10 % again if setting them in winter in the UK (because the recommended pressures assume ambient temp of 20 deg C)

Mike

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Dunnster

I use 36psi front 42psi rear, all year round. No issues as yet.

..... and by 10 % again if setting them in winter in the UK (because the recommended pressures assume ambient temp of 20 deg C)

Mike

Never occurred to me to reduce the pressure in winter. Does that mean 30 psi front and 35 psi rear in winter?

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bazza

I find the front end very heavy if the tyres aren't at recommended pressures -had the forks regreased as well in case the bearings were dry.

So reduce by 10% if solo, Tex

then another 10% in winter

and if off roading even more? so why bother with air in them at all?

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Tex

I use 36psi front 42psi rear, all year round. No issues as yet.

Never occurred to me to reduce the pressure in winter. Does that mean 30 psi front and 35 psi rear in winter?

I personally never go much under 34 front (assuming my gauge is accurate in the first place..) as I don't like the effect it has on the steering. I don't reduce them any further in the winter, either.

Back in the day, BMW (among others) listed different pressures for solo riding, pillion riding and 'fully loaded' (pillion + luggage). I just can't shake this habit. The 36/42 is a committee arrived at 'one size fits all' 'industry standard' setting that's (allegedly) suitable for a solo CB500 and a fully loaded ST1300. Bollocks.

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trisaki

Solo in run 36f and 38r feels so much better then 36f 42r - not anywhere near as bouncy or slides round corners -other members of this forum who's tyres I have adjusted to these pressures agree

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Mike5100

You are not reducing the working tyre pressures if you reduce the 'cold' pressure setting point in winter. If you don't adjust for typical winter temperatures either the tyre will not get to working temperature or if it does it will be overinflated

Mike

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Dunnster

I can understand the reasons behind changing the pressures, I'm just used to 36f 42r.

They must be tested at those pressures for optimum working values. I always thought the majority of tyre blow outs was caused by under inflated tyres. I must be very sensitive to tyre pressures as any drop, I always notice the difference.

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Tex

Fair enough! Everyone should do whatever works for them. Obviously. :)

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MikeBike
On 06/09/2016 at 18:32, Tex said:

Back in the day, BMW (among others) listed different pressures for solo riding, pillion riding and 'fully loaded' (pillion + luggage). I just can't shake this habit. The 36/42 is a committee arrived at 'one size fits all' 'industry standard' setting that's (allegedly) suitable for a solo CB500 and a fully loaded ST1300. Bollocks.

I'm riding motorway and cross country at the weekend with probably getting on for 100kg of Pillion and luggage. What sort of additional pressure should I put in the tyres front and rear?

Up until now I've just used the stanard 36/42 mainly for single riding and am aware from this thread that the suggestion is to drop so maybe the 36/42 is OK for fully loaded?

 

I'm off to get a C spanner too to tweak the preload.

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jeremyr62

Whatever works for you. The recommended pressures are just that. We are supposed to experiment. I run 33/40psi and seems to be OK for me.. 

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Griff

Personally I run 36 front and 38 rear solo. I run the full 42 on the rear when fully loaded with pillion. The only reason I don't reduce the front pressure from the recommended 36 is because the shoulders of the tyre can tend to wear more quickly than the middle. I never go above those pressures regardless of load. My Strom coped with the same pressures in Europe last year practially overloaded (Wife brought kitchen sink) and no issues. 

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MikeBike

Yes, whatever base pressure works, but I was after what sort of difference in pressure I should apply for a passenger and luggage..

Griff says an extra 4psi  in the rear..

Any other opinions?

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jeremyr62

I'd go by feel and experience. Maybe add a few psi and see how it goes. Take a bicycle pump to add air as necessary. 

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trisaki

Passenger and luggage  42psi in the  rear  normal 36 in the front and Jack up the preload  but if you start doing a lot of this put a descent shock  on it and get the sag sorted 

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Griff
16 hours ago, MikeBike said:

Griff says an extra 4psi  in the rear..

 

 

Just to clarify, that extra 4 from solo merely brings the pressure up to that recommended for the bike by the manufacturer. However regardless of load I would never feel the need to exceed that pressure.  

Edited by Griff
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Hickky

It's European regulations on tyre pressures that mean for every tyre in every size and every bike it is 36/42. Although different manufacturers have different carcasses and some rear tyres have different compounds across the tyre width, guess what, recommended pressures are 36/42. This is pure nonsense, regulations determining safety on a purely artificial basis.

When doing trackdays, most tyre experts tell you to reduce pressures by much more than can be explained by increased heat from hard riding, 32/34 is often normal. Its so the tyres reach their operating temperature quickly and road tyres are still unlikely to overheat on a trackday.

These regulations were written before tubeless motorcycle tyres were common and tubes needed to be inflated sufficiently to prevent friction between the tube and the tyre sidewall be a potential cause of premature failure.

Each car has different recommended pressures according to size of tyre, weight of vehicle, aspect ratio and potential speed. Why not with motorcycles?

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Rev Ken
9 minutes ago, Hickky said:

It's European regulations on tyre pressures that mean for every tyre in every size and every bike it is 36/42. Although different manufacturers have different carcasses and some rear tyres have different compounds across the tyre width, guess what, recommended pressures are 36/42. This is pure nonsense, regulations determining safety on a purely artificial basis.

When doing trackdays, most tyre experts tell you to reduce pressures by much more than can be explained by increased heat from hard riding, 32/34 is often normal. Its so the tyres reach their operating temperature quickly and road tyres are still unlikely to overheat on a trackday.

These regulations were written before tubeless motorcycle tyres were common and tubes needed to be inflated sufficiently to prevent friction between the tube and the tyre sidewall be a potential cause of premature failure.

Each car has different recommended pressures according to size of tyre, weight of vehicle, aspect ratio and potential speed. Why not with motorcycles?

I've never heard of an EU reg like that - but am willing to be educated. The Bridgestone tech rep who gave us a talk explained that these pressures were right for any bike unloaded or loaded up to its max (when 36/42 is recommended in the handbook. Some models still have different recommended pressures - someone will come along and know which bikes!). Of course heavier bikes have bigger tyres for the extra weight.

 

However....... I've just looked up recommended tyre pressures for my Vincent Rapide. front 18, rear 17. habitual pillion riding an extra 3lb in rear tyre. Other Vincent models had several different tyre pressures, but all had a front tyre with a  higher pressure than the back. And if carrying pillion passengers regularly it was recommended an average of another 7 lbs in the rear tyre. The technical literature pointed out that these tyre pressures were 'approximate' as they should be varied for different loads, road surfaces and speed. But as we are restricted to 70mph, speed no longer comes into it:ph34r:!

 

I've always run my 'modern' bikes with recommended tyre pressures, but who knows I might pluck up courage one day to drop the rear tyre by a couple of pounds....:devil:

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Griff
48 minutes ago, Hickky said:

It's European regulations on tyre pressures that mean for every tyre in every size and every bike it is 36/42.

 

Not sure I agree there. On my Euro model 250CRF the recommended tyre pressure for the OEM tyres that come with it is 22/22.

 

My former 2012 Triumph Explorer had recommended 36/41 but a few model years later they changed that and from memory the rear dropped to 38. 

 

Imho 42psi is a ridiculous pressure for solo riding  as one gets insufficient heat into the tyre at normal road speeds. 

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Mr Toad
2 hours ago, Rev Ken said:

I've never heard of an EU reg like that - but am willing to be educated. The Bridgestone tech rep who gave us a talk explained that these pressures were right for any bike unloaded or loaded up to its max (when 36/42 is recommended in the handbook. Some models still have different recommended pressures - someone will come along and know which bikes!). Of course heavier bikes have bigger tyres for the extra weight.

 

However....... I've just looked up recommended tyre pressures for my Vincent Rapide. front 18, rear 17. habitual pillion riding an extra 3lb in rear tyre. Other Vincent models had several different tyre pressures, but all had a front tyre with a  higher pressure than the back. And if carrying pillion passengers regularly it was recommended an average of another 7 lbs in the rear tyre. The technical literature pointed out that these tyre pressures were 'approximate' as they should be varied for different loads, road surfaces and speed. But as we are restricted to 70mph, speed no longer comes into it:ph34r:!

 

I've always run my 'modern' bikes with recommended tyre pressures, but who knows I might pluck up courage one day to drop the rear tyre by a couple of pounds....:devil:

 

Padre, it's the EU..................of course there's a regulation.:rolleyes:

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Rev Ken
20 hours ago, Mr Toad said:

 

Padre, it's the EU..................of course there's a regulation.:rolleyes:

So at what divergence from the 'regulation' pressures can insurance firms start to turn down insurance claims by saying we compromised the bike's road holding whcih caused the accident?:cry:

Edited by Rev Ken

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Mr Toad
1 hour ago, Rev Ken said:

So at what divergence from the 'regulation' pressures can insurance firms start to turn down insurance claims by saying we compromised the bike's road holding whcih caused the accident?:cry:

 

I suspect that as soon as you deviate in any significant way from the manufacturers recommended pressures in the handbook. I understand that all cars sold in the EU from 2016 have to be fitted with tyre pressure monitoring systems, something I only discovered recently. Given that bit of info it leaves insurance companies even more wriggle room on the basis that if your tyre pressures are off and your motor has a TPMS then I can see them passing some of the blame on and reducing their settlement accordingly.

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pjm

Real world chances of an insurance company checking tyre pressures = zero. How would they be able to prove it did not deflate after the event?. Who from the insurance company is going to check your tyres. Get real guys.

 

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Tex
9 hours ago, pjm said:

Real world chances of an insurance company checking tyre pressures = zero. How would they be able to prove it did not deflate after the event?. Who from the insurance company is going to check your tyres. Get real guys.

 


Beat me to it, Peter. Guys, I saw dozens of insurance assessors in action (back when they were actual people) and I never, ever saw one check a tyre pressure. A cursory glance at the tyres to ensure they weren’t bald is as ‘in depth’ as they ever got. 
 

‘Actual people’? Yes, the days of an engineer being paid to drive around the country looking at crash damaged vehicles are (almost) done. It still happens, but much less often. The internet has killed that one. Nowadays the garage/repairer takes photos of the damage on his phone and emails them to the insurance company. Someone (presumably ‘technical’) looks at the pics and makes a decision. Cheap, quick, effective. 

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