Tyre wear problem

[GSVR]

I was wondering what other racers have done when their tyres start wearing like the one on in this picture. Once this happens your tyre just gets worse and worse.

What causes it? What is the technical term for this kind of wear?

At the time this happend it was at Manfield on test days and my bike wasn't the only one it was happening to.

I will post my solution to the problem that I have stuck to for the rest of the time I was racing but recent ideas have me thinking there may be a better solution.

Any input greatly appreciated.

This was on my old SV650 with Std frontend with emulators and from memory a way to soft GSXR rear shock. The tyre was a fresh new Pirelli Diablo Superbike slick SC1. The track was Manfeild before any resealing work had been done.

[Clivoris]

Is it what happens when you leave the pub and give a cold tyre too much wrist?

[Ivan]

I was wondering what other racers have done when their tyres start wearing like the one on in this picture. Once this happens your tyre just gets worse and worse.

What causes it? What is the technical term for this kind of wear?

At the time this happend it was at Manfield on test days and my bike wasn't the only one it was happening to.

I will post my solution to the problem that I have stuck to for the rest of the time I was racing but recent ideas have me thinking there may be a better solution.

Any input greatly appreciated.

This was on my old SV650 with Std frontend with emulators and from memory a way to soft GSXR rear shock. The tyre was a fresh new Pirelli Diablo Superbike slick SC1. The track was Manfeild before any resealing work had been done.

Im Sure that is because you do not have enough preload on the suspension thats what myne looked like on my 125 before we adjusted the preload

[Sketchy_Racer]

Yeah looks like it's too saggy in the rear, possibly a bit of cold tear also (made worse by to much squat) raise preload, and up tyre pressure.

.... Sketchy_Racer doessss know what he's talking about [tui add here]

[GSVR]

Im Sure that is because you do not have enough preload on the suspension thats what myne looked like on my 125 before we adjusted the preload

Yeah looks like it's too saggy in the rear, possibly a bit of cold tear also (made worse by to much squat) raise preload, and up tyre pressure.

.... Sketchy_Racer doessss know what he's talking about [tui add here]

Great thanks for the replies. Tyre pressure helped in the past but not with this these tyres.

I'll add a bit more now.


At the same time Glen Williams had just started racing his Old SV650 and he had it set up with his old ZX10 rear shock and an USD frontend. His rear tyre was just like mine as well but much worse. I think this may have been before he sent it away to be revalved. His bike was not ideal but would have been miles better set up than mine.

Oh one more thing the wear/ damage for the righthanders was alot less than for the 2 lefthanders. 2 corners created more wear than the other 5? on Manfield.

[Ivan]

Great thanks for the replies. Tyre pressure helped in the past but not with this these tyres.

I'll add a bit more now.


At the same time Glen Williams had just started racing his Old SV650 and he had it set up with his old ZX10 rear shock and an USD frontend. His rear tyre was just like mine as well but much worse. I think this may have been before he sent it away to be revalved. His bike was not ideal but would have been miles better set up than mine.

Oh one more thing the wear/ damage for the righthanders was alot less than for the 2 lefthanders. 2 corners created more wear than the other 5? on Manfield.

YipCauseManfield is right handers the right hand sideof the tire stays hot but becuase of the 2 lefts you hardly get any heat in them tires that why Alot of guys bin it in these left hand corners as thetires are a shit load corner when you look at Manfield the rights are very long and flowing so you on the edge of the tire for a while putting alot of heat into it and then down the straight heats the center but the left during all this is cooling off then all of a sudden you back onto a left again slightly colder tire and possibly cold Tearing the tire as the tire is to cold?? Thats a guess as to why someone like Shaun Or Robert will know but Im just thinking from my opinion what it could be but im no expert at this

[Robert Taylor]

Yeah looks like it's too saggy in the rear, possibly a bit of cold tear also (made worse by to much squat) raise preload, and up tyre pressure.

.... Sketchy_Racer doessss know what he's talking about [tui add here]

Manipulating spring preload and tyre pressure will often get rid of and minimise the problem but it is usually not skinning the cat correctly.

Comments:

1) The motion ratio that the SV650 linkage imparts is sufficiently different to that in the ( K1 to K4 ? ) GSXR1000. Compared to the GSXR for any given distance of wheel movement the shock shaft is moved less on the SV. The linkage is less aggressive on the SV therefore the shock shaft moves at a slower speed. Damping in such shocks is velocity dependent, if you move it slower ( as in this case ) it has less damping. That is one of the compelling reasons the shock feels soft to you.

2) Has the shock ever been apart? Much like a car tyre lets its pressurised air migrate through the rubber over time exactly the same happens in these oem shocks that use a bladder. The nitrogen pressure migrates through the rubber into the oil. If it has never been apart it will well and truly be a ''milkshake'' by now, softer again and it will go off more quickly.

3) Even for the GSXR ( which has a more aggressive linkage ) that shock is too soft. We happen to have dyno'd these in the past. Compared to a well sorted racing shock the initial damping at very low shaft speed has a very lazy build up because there is too much bypass bleed through the main shaft. STOP RIGHT NOW thinking about closing off the low speed compression adjuster, that actually has very little influence over the first initial part of very slow speed shaft travel. You may fudge it a little, that is all. The compression adjuster works on shaft displacement only and is a bypass bleed for oil into the reservoir, that part of the damping mechanism accounts for only 12 to 13% of total damping force. On the main shaft the bypass jet is handling a much greater volume of total flow, but of course the shock has to be stripped to manipulate its size.

4) Allied with that the shim stack opens too early and allows it to squat too readily, this means that the rear end sinks into its stroke too readily pre compressing the spring too much. So there is more spring force, its engaging a little too early on the rising rate part of the linkage and that overloads the tyre.

5 ) The tyre is also a part of the suspension action but there is a fine window where it is going to work, it varies from track to track, temperature, gearing, all sorts of variables. Too hard suspension and the tyre is compressing too much and ''scrubbing the loaded contact surface. Too soft suspension and it squats and becomes hard ( oversimplistically ) delivering a similiar result.

6 ) Another cause of scewing tyres can be too much rebound damping and I dont mean just on the clicker I mean on the shim stack. THE CLICKERS are not some magical device that changes the character of the shock immensely. Kyle Key was stressing his front tyre at the Pukekohe Nationals, we analysed that it was happening while working low in its stroke through ( especially )turn 1. It was essentially being held down too aggressively instead of recovering as quickly as it should. That was causing harshness and was making the tyre do too much of the absorption action. ( I am glad he had Ohlins cartridges fitted rather than anything else because they are dramatically user friendly to make quick internal setting changes ) And anyway how do you know whether the rebound calibration in that GSXR shock is in any way suitable for the motion ratio that the SV linkage imparts on it? I hope you havent been misled by another forum?

7 ) I am guessing that your personal stats are roughly conversant with the spring rate on that GSXR. Many people would fit a firmer spring which is also often the wrong way to skin the cat and will result in harshness over the more abrupt bumps.

As I stated somewhere in another thread springs are more about position, damping is about controlling rate of change of position.............. the rate of change of position in that GSXR shock is clearly lacking, especially in compression.

Just for relevant information we will be up and running modifying standard shocks such as this very soon. As we have a huge database of Ohlins damping curves for popular models of bikes. So we have a huge helping hand in knowing what force curves are required / mods required. Whilst this sort of oem modification work wont attain the same performance as our beloveed Swedish stuff it is going to give great bang for buck for club riders.

[GSVR]

Yep. Well the conclusion was reached that the SC1 compound was too soft and I've been useing SC2s ever since and the wear is really good getting lots of riding out of a tyre. Becuase I'm so tight I even tried an SC3 but found it was abit slippery for even someone as slow as myself.

What I would like to know if anyone racing SVs has had any luck with soft compound tyres. I might get some new tyres soon so even changing brand is a possibility.

Or maybe an SC1 is usable with the right suspension and tyre pressure!

[GSVR]

Thanks for the reply Robert. I will read your post several times to get the most out of it.

[White trash]

Question Gary. What time of the year was it?

[TonyB]

My back tyre has developed a very similar wear pattern on the left hand side from riding at Ruapuna. A few people looked at it and said that the shock is bottoming out- though looking at Roberts answer its not likely to be quite that simple!

Nice pic BTW- its not all that easy to get a decent pic of wear like that

[Robert Taylor]

Yep. Well the conclusion was reached that the SC1 compound was too soft and I've been useing SC2s ever since and the wear is really good getting lots of riding out of a tyre. Becuase I'm so tight I even tried an SC3 but found it was abit slippery for even someone as slow as myself.

What I would like to know if anyone racing SVs has had any luck with soft compound tyres. I might get some new tyres soon so even changing brand is a possibility.

Or maybe an SC1 is usable with the right suspension and tyre pressure!

Not on every track! Teretonga ( for example ) is the worst track and there is a specific dynamic that is causing it.

[GSVR]

Question Gary. What time of the year was it?

I think it would have been between the 2nd and 3rd rounds of the Vic Club meetings in 2006. Funny how I still have the tyre.

With the Pirellis it seems you can go SC0 on the front no worrys but the SC2 was the softest compound that worked on the back.

[Robert Taylor]

I think it would have been between the 2nd and 3rd rounds of the Vic Club meetings in 2006. Funny how I still have the tyre.

With the Pirellis it seems you can go SC0 on the front no worrys but the SC2 was the softest compound that worked on the back.

You could actually get an SC1 to work but the shock and its spec has to be right on the money. Many tyre wear problems are blamed on the tyres when very often its a suspension and set up problem. But generally yes the SC2s are more forgiving re set up.

Its quite a good system really...we blame the tyre guys and the tyre guys blame us!

[White trash]

I think it would have been between the 2nd and 3rd rounds of the Vic Club meetings in 2006. Funny how I still have the tyre.

With the Pirellis it seems you can go SC0 on the front no worrys but the SC2 was the softest compound that worked on the back.

So bloody cold then? A contributing factor in conjunction with the incorrect suspension would have to be that the tyre wasn't anywhere near it's operating temperature.