Tyre pressures and track temps

[TLR luva]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

[Shaun]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

Contact John Hepburn man at Timaru Metal recyclers

[Shaun]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

A lot of what you have asked depends on what year those tyres were made, the pressures for them changed radically over a 12 month period.

[TLR luva]

tyres brand new 6 weeks ago

[SWERVE]

AH yes............. brand new to you......... but manufactured!!!!!!!! Shaun will tell ya what numbers to look for on Pirelli.

[TLR luva]

Im pretty sure made in 2010

[CHOPPA]

SC2s tend to be a bit slippery, try 1s

[Robert Taylor]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

We have been monitoring the relationship between track temperature and tyre temperature for some time now. The relationship can be exponential. For example a drop in track temperature from 17 celsius to 11 celsius resulted in a drop in tyre temperature of around 20 celsius at both ends with a bike we were working with. That then needed manipulating upwards by slightly firmer suspension settings to work the tyres harder and generate more heat. To a degree the opposite applies at higher track temps.
The smooth tyres you were getting was partly because you needed softer suspension settings, especially in the rear. Given the warmer temps. Theres of course a lot more to it than that but a shift in track temperature changes everything.

[Grumph]

Timaru is something of an anomaly in NZ...been there the last two weekends and this spring is just the same as usual. Levels just does not get any track temperature until about early December. As I understand it the water table on Levels plain is quite high and doesn't drop until mid Summer.
Better to come up to an open hire day at Ruapuna for your setup testing - you'll get more consistent results.

[Robert Taylor]

Timaru is something of an anomaly in NZ...been there the last two weekends and this spring is just the same as usual. Levels just does not get any track temperature until about early December. As I understand it the water table on Levels plain is quite high and doesn't drop until mid Summer.
Better to come up to an open hire day at Ruapuna for your setup testing - you'll get more consistent results.

Then you've got a setup for Ruapuna and not Levels. Every track is different and requires a different setup for optimum performance, Throw in temperature shift and that also requires different setup, and often tyre compounds. Different brands of tyre also require different setup.

[discodan]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

I had the simlar problem recently when I was using a stock standard rear shock. From what I could tell, the shock was not working the tyre hard enough and it wasn't generating any grip. The SC2 tyres don't tear up as easily as the softer SC1s so maybe that is the reason for the 'glassey' effect.

It sounds like you have the same problem maybe, which means the shock is probably due for a service and possibly a revalve. Guys like Kerry Dukic and Robert Taylor would be able to do this for you and have a good idea of what would be suitable settings for you based on weight etc. You could also try Red Fenton who is closer in Chch.

Good luck getting it sorted!

[gixerracer]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

If those pressures you are using are hot off tyre warmers they should be fine. If they are cold then you will be a bit off.

[Robert Taylor]

You have to be extra careful when you hear the term ''REVALVING''. Many believe that revalving is a magic cure all when in fact its often only half the equation in getting a bike to work properly around a track ( or on road ) and to get the tyres to work properly.
First and foremost the spring rates and preload has to match your height and weight and the tyres you are using. AND the track. No amount of revalving is ever going to work if the spring rate is incorrect. I can remember one competitor during the last Nationals who was really struggling with the ''I can do it cheaper than CKT'' revalve when the spring rate and preload setting was miles off for him. Installation of a correct spring yielded laptimes 3 seconds per lap faster, and his tyres then began to work properly. Beware of greeks bearing gifts!
Bear in mind also that while a good many stock pistons are suitable for revalving also a good number are not. The GSXR750 piston is not the best one on the block but it is ok to revalve for a fairly decent result. Providing of course the guy doing the work has a solid and proven reputation revalving ( AND ITS NOT JUST REVALVING! ) the stock pistons with the said model. Success with another make / model is no guarantee of getting a solid result with your model, as its all very dependent on some solid testing.
Other issues................there is another issue with that model of shock that we easily know how to fix but Im not divulging that directly here as it has cost us time and therefore money to work it out.
As I said in my earlier post there are so many variables. You can have a bike setup perfectly for Levels and it will be average at Ruapuna. Teretonga requires a very different setup to make the rear tyre ''live'' because of stress in the loop at the end of the main straight. If there is a significant temperature shift the settings need changing.
Most of the time it seems that everything is subservient to getting temperature into the tyres to maximise grip but also to maximise their life. So you manipulate your chassis and suspension setup ( plus pressures and compounds ) to get within that magic window where everything works best.

[gixerracer]

Hi experts. I am running pirelli slicks on my k7 gsxr750, soft compound front and medium in the rear. my question is based around a recent test day at levels. over the winter my tyres get pretty balled up with rubber but not cold sheer. Have been running them at 30 psi front and 26 in rear. now last week I went testing, my bike seemed to be sliding around a fair bit and when come back to pits my tyres were as smooth as a babies ass. Track temp unknown but was a warm morning. So as the track temp gets warmer is it best to drop tyre pressures down a bit ? or am I just running the wrong pressures all together. Also I had run with more compression on shocks front and rear so would that change grip much. thanks for any suggestions.

Dont listen to Robert Taylor he dribbles more than a pre school child

[suzuki21]

Tyre wear is generally because of incorrect pressure, lack of grip is generally suspension related. Tyre pressures should be adjusted accordingly throughout the day, Craig is right - 30 26 is way too high if cold, aim for a 4-5 pound increase from cold to hot - depending on how you ride will determine the starting pressure.
You will need tyre warmers as the low pressures tyres demand now days when cold will otherwise feel like a flat tyre, and by the time they are warmed up they will be shredded.