Tyre Pressures

[WebTone]

Few questions been asked recently about tyre pressures for particular bike models. Caution guys & girls. If you don't have the type of tyres listed in the owners manual, these figures can be wildly inaccurate. The owners manual figures are a guide to optimum pressures and are usually taken as with a 12 stone rider. Some manuals will also give figures for high speed riding or regular pillion work.

Note that temperature will affect many tyre pressure settings and you should always look for the settings for your part of the world.

If you have anything other than standard tyres then check with the tyre manufacturer or the bike manufacturere or both.

If you have Bridgestone tyres then this guide may help you:


http://www.market-place-uk.com/Bridgestone_Motorcycle_Tyre_Guide.xls

[Lateshift]

It seems strange that this being my first post back for a while is to do with tyre pressures, however this is a subject quite close to my heart and one that i have been having quite a lot to do with over the last 2 weeks.

A bike manufacturer is obliged by law to state the "recommended" cold tyre pressure for both solo and pillion riding, they are also olbiged to list the tyre pressures that are recommended for the tyres that they have tested on that vehicle.

Whilst temperature can have a small part to play in the cold pressures, its often neglible once the tyre is warm, this is due in no small part to the fact that whilst the tyre manufacturer lists a maximum temperature there is quite a large amount of added room for manouevre in their limits.

Aprilia didnt have the decency to list the road going tyre pressures for the tyres they fitted to my new bike, only the track pressures, and so having spoken to Dunlop whilst at the BSB at Snetterton they advised me that nearly all radial tyres for modern sports bikes now are designed to run at 36/42 with the lighter sports bikes running in the region of 36/36

Now me being totally mystified by this statement i then checked on the web with Dunlop and found to my horror that Dunlop have a UK and a US website that list two totally different pressures, 1 at 31/36 and the other at 36/40.

And so in whilst in Wales last week i tried all 3 tyre pressures, the result being that 36/42 was dangerous beyond belief, 31/36 pretty much the same, and 36/40 again helping to put the bike nicely out of shape.

Having had to take an emergency stop to let air out, i later found that for the rest of the day i had been running on what is effectively track pressures at 29/31, for the most part the bike worked well to the point that i was overcooking the tyres and they were starting to look like they had done a day at Brands on the Welsh roads :)

However on every occassion that i checked the different tyre pressures the pressure was only rising by around 4psi for both front and rear, which is about right for a tyre running at road use.

If you take into account temperature of the tyre, tyres are designed to get very warm indeed, purely to allow the rubber compound to do its job and effectively stick to the road, whilst it plays an important part in what it can actually do to the psi in the tyre once running, it doesnt tend to make much of a difference to a road tyre that is cold unless you are living in a 30+ degree climate and the tyres live in the sun :)

The biggest tip for anyone wondering about tyre pressures is that they react differently for everyone, all tyres give feedback, whether you feel it or not is down to you and the bike and the way the bike is setup, however ultimately the amount of air that you put in the tyre will influence the amount of feedback that you get from the road/tyres.

The morale of that is test and adjust, and take what the manufacturer states as what they think is the optimum pressure for someone of an average weight build, take what the tyre manufacturer states as again what they recommend for the load placed on the tyre from the bike and rider.

And ultimately experiment with a few psi here and there to get the feel of the tyres so you know what they are doing and when :)

[WebTone]

A MASSIVE WECOME BACK M8:clap:clap:clap:clap:clap

Hope you had fun in Wales. Hope the new bike went as well as you hoped. Sounds a sod getting the pressures right for your motor. Too much conflicting advice.

I thought it worth while to trawl webby for this so that some are not totally bemused by my advice:

There are many individual causes of tyre troubles. However, the three abuses which will cause most problems, and the greatest costs, are under-inflation, overloading and speeding.

Under-inflation

Surveys by tyre service engineers show that at least 25 per cent of all tyres examined are under-inflated by more than 10 per cent. Neglect of inflation pressures is one of the principle causes of rapid wear, uneven tread wear and premature tyre failure and it is an abuse which surveys show to be on the increase. (NB: It should be stressed that over-inflation may also result in inferior handling, excessive tyre wear and premature failure.)

Overloading

Loading any vehicle above what they are designed to carry is illegal. It is also likely to put excessive strain on the tyres resulting in greater than normal deflection and overheating which, in turn, leads to more rapid wear, greater susceptibility to impact damage and the danger of premature failure. (NB: The Owner's Handbook will give increased inflation pressures for full load conditions.)

Speeding

Travelling for long distances on motorways at sustained high speeds and generally exceeding statutory speed limits imposes strenuous demands on tyres especially in terms of heat generation. Tyres in good condition and correctly inflated are designed to withstand the heat build-up at their maximum rated speeds. However, if inflation pressures are significantly below those recommended then excessive heat will be generated, and in consequence wear will be accelerated and deflection will be greater with the risk of premature, and sometimes catastrophic, failure.

What the law requires

It is important to understand what the law requires in regard to the condition and care of tyres. Regulations govern many aspects of tyre condition of which the following are the principal points:

Tyres must be suitable (ie of the correct type and size) for the use to which the vehicle is being put and must be inflated to the vehicle or tyre manufacturers' recommended pressures.

No tyre must have a break in its fabric or a cut deep enough to reach the body cords. No cut must be more than 25mm or 10 per cent of the tyre's section width in length, whichever is the greater.

4. There must be no lump, bulge or tear caused by separation or partial fracture of its structure, neither must any portion of the ply or cord structure be exposed.

[Lateshift]

Its becoming a common problem unfortunately, with more and more riders tending to use under inflated tyres in an effort to put a bigger footprint on the road for cornering, whilst it does serve a purpose amd help to an extent, it doesnt help with tyre life and as is the case normally the tyre can end up pulling itself off the rim because quite simply on the road you dont generate enough heat constantly.

With the pressures that i had to work with, i lost the front end of the bike twice at over 40mph going into a corner, on roads that would put some tracks to shame, on the lower pressures and given that it was doing 70mph plus and for over 50 miles at a time they worked well but after a 10 minute stop they were useless.

Fortunately (and after countless debates with others) i am going back to Pilot Power 2CT's this weekend, i dont rate the Dunlop 208RR's at all and its interesting that Aprilia are now putting Supercorsa's/Rennsports on both the RSVR and Factory, probably because the Dunlop literally rips apart on these bikes with as little as a 1000 miles on them.

One word of advice though, you wont get the full benefit from a tyre unless the suspension is working on song, and to be honest half of the problem with tyres is that the suspension settings are out and they cause the tyre to lose grip/skip etc etc

As with anything set the bike up properly and give yourself a fighting chance to start with :)

[WebTone]

...i lost the front end of the bike twice at over 40mph going into a corner, on roads that would put some tracks to shame, ...

Where did you go in Wales? I know the bits around Fishguard, Goodwick and all around there up to Swansea quite well (Inlaws country).

I'd be interested to know where your roads were so I can play this summer.

[Lateshift]

All around the Brecon/Llandovery/Builth Wells and Llandridnod wells area

I covered about 600 miles in 3 rides, no bumps all clean relatively new tarmac, 35-40 mile sections of mountain roads that really do make the TT course look easy, and best of all most of it in 3rd gear :D

That being said the week started on a downer due to the Sunday before i got there, the guy that i sold my ZX9R to, completely obliterated it (absolutely nothing left of it whatsoever) in a smash at over a ton, when he literally took off for 35 yards over the top of a humpback that had an immediate right hand bend after it, must have been going some to smash a telegraph pole thats for sure ;) :D

Fortunately he got away with concussion and some light scratches, he doesnt know how lucky he was/is ;)

However in the future i have an idea for a little jaunt down there, i know of a really nice cottage that sleeps 6, costs £270 a week self catering (its awesome) and is smack bang in the middle of them roads (and it has a fantastic view) so i may in the future look into booking it and having a ride down there :)

[WebTone]

Flip me. Matey was so lucky.

Seems I've done some of those roads, or so the boss here tells me.

Its all good down there and not at all like the north around Mold and the like. Too many cameras up there and a Chief Constable that hates bikers.

[Lateshift]

I have to say i didnt see 1 camera all week, and being from Chester and knowing North Wales well, i know exactly what you mean about up there :D