An interesting take on tyre pressures

[slofox]

Was in discussion re tyres t'other day and was told as follows:

"The reason back tyres square off is because riders use too low a tyre pressure. The user manual recommendations are not that good - the manufacturer of the bike doesn't care about tyre wear. A higher pressure will give the tyre better shape and it will wear longer. Go with the tyre manufacturer's pressures not the bike manufacturer's..."

So I've done a heap of reading about tyres in the last couple of weeks and have found the odd thread that might support this assertion. But opinion seems to be pretty evenly split - in fact miles apart at times and this from opposing "experts" claiming either a million years in the tyre industry or dealing with bike tyres. There ain't no agreement out there.

I suspect that the quote above may be at least partially true. But I also suspect that higher pressures may lessen grip to some extent. The only time I rode with a reeeeally high back tyre pressure the bike was all over the place.

I feel pretty sure that underinflation may well cause the tyre to lose its profile under certain road conditions. And that might lessen grip as well

Incidentally, I have not found any tyre makers' pressure recommendations to compare with the bike makers pressure recommendations despite trawling gazillions of websites. My own thoughts are that it must be nigh on impossible to cover the wide range of loadings any given bike may have and come up with a "correct" pressure...

So, I thought to draw upon the collective wisdom of KB, seeking out the opinions of all our local experts...

What say you?

Bike makers pressures too low?
Does this cause poor wear patterns?
How does this affect grip?
Etc etc etc?

[Grubber]

My 2c worth.
I run 190's on the rear of my Daytona and i usually run it at around the 40 to 42 psi when riding at a reasonable pace on road. If i decide to have a fast day out i tend to let it run around 36 to 38 psi.
Track day i run around 32 or 34 for obvious reasons.
I am around 11000k on this set and no rounding to speak of. Still seem to have a ton of grip too.

how's that for ya!

[yachtie10]

I Think it has more to do with the riding you do
obviously pressure has an effect on wear but if you spend a lot of time on straight roads then they will square off no matter what you do

Guys I know who just ride the twisties dont square off there tyres because they are worn out before that is an issue

[AllanB]

Interesting.

I run a lower pressure in the rear than the factory recommendation of 42 - I run 39 as I found 42 to be too harsh. Fronts fine at 36.

No issues with squaring off, though obviously a rear tyre will naturally wear quicker in the centre as you spend the greater % of your ride there and you tend to squirt more power through it when vertical.

However to clarify, most of my rides involve a good set of corners to fang around so the sides get a fair bit of use up and above someone who uses their bike as a daily commute.

Just fang it harder in the corners!

Back to the theory - on a car too high pressure will wear the centers of the tyre faster, unsure how I can apply this to a bike though.

interesting post.

[slofox]

Interesting.

I run a lower pressure in the rear than the factory recommendation of 42 - I run 39 as I found 42 to be too harsh. Fronts fine at 36.

No issues with squaring off, though obviously a rear tyre will naturally wear quicker in the centre as you spend the greater % of your ride there and you tend to squirt more power through it when vertical.

However to clarify, most of my rides involve a good set of corners to fang around so the sides get a fair bit of use up and above someone who uses their bike as a daily commute.

Just fang it harder in the corners!

Back to the theory - on a car too high pressure will wear the centers of the tyre faster, unsure how I can apply this to a bike though.

interesting post.

One of the things I read said that the maximum pressure on the tyre (42psi in your case) is NOT the recommended but the MAXIMUM pressure you can run it at. Should only be used when "fully laden" (whatever that means).
So if you are a lightish sort of person, and don't load up with luggage, you wouldn't run it at maximum.

I might try going maybe two psi higher on the next set of tyres and see what happens...

[Usarka]

Conti suggest that you follow the bike manufacturers guidelines.

http://www.conti-bike.co.uk/default.asp?pid=27 Probably a gigantic case of buck passing.....

[Gremlin]

It also depends from bike to bike.

The hornet sits at 36F 42R (honda recommendations), and tyres like PR2, Strada, etc, have all been happy, and excellent life, 15k or more from rear, more than that on front. Bike is used used almost entirely for commuting, motorways, so a lot of centre wear.

The KTM is recommended to be 31F 31R, I run on 32F 36R or thereabouts. Bike carries more weight than stock, too soft and it was ripping up the tyres. Too hard and they wouldn't grip properly. KTM does very little commuting and I wear the edges of the front tyre faster than even the centre of the rear. Usually turn the front triangular and wear away the edges of the blocks. Supposedly, its because the tyres are too soft... Mileage varies a little, but usually around 7500km for a set of Pirelli Scorpion Syncs. Going to try a set of Angels shortly and see how I go.

[Motu]

I'm a low pressure sort of guy...maybe riding around on trials bikes with 3 or 4 psi has distorted my thinking....low pressures to me mean traction,and I'm all for traction.I don't ride an expensive powerful bike with really expensive tyres,but I'm on a tight budget,and buying tyres hurts.

On my streettracker setup I use Dunlop K70's,a tyre from the '60's,and I run them at the pressures they used in the day - 25psi rear,20 front....recommended pressures for the bike are 36 and 32.They do wear fast,but I love the grip.I feel nervous using my standard tyres with standard pressures,the bike seems to be on a knife edge and runs wide.

A month ago,after not riding the bike for some time I went for a ride,after getting settled in I really enjoyed the ride,had great confidence in the bike,it never felt nervous or ran wide.Getting home I see there are no chicken strips,it's right down to the edge when I normally have 20mm.A check on tyre pressures show 8 psi in the rear.It takes all kinds - don't worry,I'm happy.

[Corse1]

I wrote a letter to spannerman a while ago re tyre pressures. I had recently wasted a set of pirelli diablo stradas on the ST4s in 10000km's. I was running the Ducati recommended pressurs of 32 front 36 rear.
The reason i had written the letter was that the triple came with Triumph recommended pressures of 36 front and 42 rear.

Didn't really get a straight answer, rather some questions re visual properties of the tyres to confirm his recommendations.

My own findings are that the 36/42 Triumph pressures work great on the triple and to let you know how I ride the PR2's on it now have 5500kms on them now with no squaring off at all and with a pretty much even wear with tread depth being between 2-3mm left all over the tyre. Now I am worried about getting 10k km's out of the set.

Now i am running higher pressures on the 4s ....about 35 front and 39 rear and the wear seems to be more even which would support the statement that higher pressures prevent square off on the rear.

What I have noticed however is that while the higher pressures on the lighter triumph give me full confidence at all lean angles, if the heavier bike has the same pressures the front end does not have the same grip and is a little nervous.

This seems to me to be the opposite effect of what I would think

Soooo there are a lot of variables involved such as suspension set up etc (heavier bike has higher quality suspension..??? go figure).......

All the tyres I run are more sport tour than sport. I can't get my head around 5000km replacement costs...i mean I cant get my wifes head around the costs.

Really i think kiwi roads are that rough that they will chew out tyres at alarming rates on any bike. Ameriacan riders get 10 m 15 thousand miles out of the same tyres I get 10k km's out of.

Back to the thread... i would recommend using pressures closer to the higher end than lower.
Track days yes I run 30 - 32 or 32-34 depending on temp and who gives a toss if they wear faster. But there are plenty of racers here to give you their advice.

Tyres tyres tyres tyres tyres .... al little bit like oil questions

[davebullet]

One of the things I read said that the maximum pressure on the tyre (42psi in your case) is NOT the recommended but the MAXIMUM pressure you can run it at. Should only be used when "fully laden" (whatever that means).

Fully laden = 2 to 3 pies.
Fully had it = missus in tow.

[HenryDorsetCase]

I was thinking about this the other day. I have been experimenting with the front tyre pressure on the Scrambler. New front tyre last week (Bridgestone DeathWing OEM size. Manuel says 30 psi, I am happily running 26.

rear recommended either 30 ir 32, happy at 28. I am light-ish, and usually ride solo, and I presume the recommendations are for two fat americans running flat out across Death Valley.

grip is fine, turn in good, no worries.

[Mishy]

So this is an interesting question - what pressures ? and why ?
I go entirely from a reccomendation supplied by the tyre manufacturer, and have found this to be pretty much dead right. They are also TUV approved, so this tells me that they have been tested outside the factory as well.

Having the correct tyre pressure in the rear tyre certainly has a huge impact on tyre life, and being a few psi off can have a much greater influence than most people think - as in 7% (roughly) less life 2 psi short of optimum, up to 15% less at 4 psi short, and 25% or more at 6 psi short.
Heat is what causes the extra wear, and a higher pressure keeps the heat build up in check.

Most Jap road bikes with radial tyre sizes would want 36 F, and 42 R as a start point. If you are carrying a load, then put 2 psi extra in, and if you are doing sustained high speed, then add 2 psi more !
All of this helps keep the heat down, and the wear in check when you have a bigger load on the tyre, or extra speed causing extra heat build up.

The "max load at 42psi" mark refers to the max load, not the max inflation pressure, and just tells you that to carry that load, you have to have at least 42 psi in the tyre.

I think that most manufacturers are reccomending pressures pretty close to what the tyre manufacturers are, so I would be surprised if there were many huge differences with large modern bikes - I'd interested to hear if anyone has come across an example.

[Corse1]

I am light-ish,

Be interested to see how your tyre wear progresses. Maybe your light but those are pretty low pressures.

Ok I am jealous

[Corse1]

Having the correct tyre pressure in the rear tyre certainly has a huge impact on tyre life, and being a few psi off can have a much greater influence than most people think - as in 7% (roughly) less life 2 psi short of optimum, up to 15% less at 4 psi short, and 25% or more at 6 psi short.
Heat is what causes the extra wear, and a higher pressure keeps the heat build up in check.

Most Jap road bikes with radial tyre sizes would want 36 F, and 42 R as a start point.

Yes I think my bad experience with the higher pressures was when I had the wife on the back . I am slowly getting the duc pressures back up to the 36-42. Not sure why the would have even recommended the 32-36 pressures.

[AllanB]

New front tyre last week Bridgestone DeathWing.

I'm not sure if that is the coolest name I've ever heard for a tyre or a scary nickname relating to it's grip!!!!