Scrubbing In When It's Cold And Wet

[gyokota]

As y'all might imagine, it's cold and wet here in the SF Bay Area. I just spooned on a pair of brand new tires. I want to scrub them in, and I'd like to do so safely. I'm hoping for a dry spell , but the satellite and radar pics don't show much promise for dry, warm pavement any time soon. I can't imagine a worse set of circumstances, either... cold, wet, new tires. Until I get them scrubbed in, I'm stuck riding my Aprilia RS50/75 on my commute (fun, but slow).

 

I'm assuming that I can get more effective results (i.e. stay upright!) if I drop the tire inflation pressure, but how low? I recall Will saying that the school bikes were running 29psiF/27psiR when we ran on a very cold day at the Streets, and I'm thinking of using that as a starting point.

 

Any advice or warnings would be greatly appreciated!

[Balistic]

The reason I drop the tire pressure on cold days is that the time between when we check them and when we ride them 7am to 9am you can have a significant change in ambient temp. For every 10 degrees tire pressure will vary 1 pound.

 

At Streets when is still in the 30s at 7am and I know it will be in the 50s when we ride I will ask they be set a couple pounds low. The 208 ZRs work best on the track at 30 front 28 rear, a pound lower than the GPs.

 

As fare as scuffing them in, the correct pressure will be best. The tire when it's new is too smooth to have good grip and you just need to ruff the surface up. This can be tricky as too much lean before they are scuffed and boom. The thing I try to keep in mind is the tire will talk to you when is starting to slide, you need to be slow with turning to find this point. If you lean the bike through the turn and can feel when it is at the point of sliding you can have it scuffed in a few turns.

 

I learned this the hard way as have many others, so my advice to you would be take it slow and try to never lean the bike onto an entirely un-scuffed part of the tire. What that means is the tire will scuff out from the middle as you lean it and the first 20 degrees no issue, then you need to be cautious about adding lean slowly so part of the contact patch is always scuffed(1/2).

[JeF4y]

Heat is obviously key here. A lower pressure in the tire will allow the tire to flex more and heat up quicker. If you're talking riding on the street, I would say run your tires kinda low for a ride (like 32/32 or so). Go for a ride and be CAREFUL. Ride like it's wet and you're on bald tires. Give it 50 or 100 miles and you should be well. From there, adjust your pressure as required.

 

Disclaimer:

this is my method, it may not work for you. You may fall. I find it works quite well for me....

 

On the track, a tirewarmer to FULL operating temp, and then hard gas/hard brake while vertical. Go VERY easy through the turns, going a little lower on each corner. Within 1-2 laps they'll be scuffed all the way.

 

If you don't have tire warmers, figure 3-4 laps, and you can't do hard accelleration or braking for at least 1 lap.

[Balistic]

Heat is obviously key here. A lower pressure in the tire will allow the tire to flex more and heat up quicker.

There is one problem with this idea and that is how the tire cools. the tire is convecting heat the ground so if the ground is cold the last thing you want to do is give the tire more contact with the cold surface. True lower pressures will build more heat in the tire but on a cold day the result could be a tire that looses heat quicker than it is making it.

[JeF4y]

Absolutely agree. Good point Will. Really, it comes down to how you're riding, where you're riding, your experience & risk-taking level, and how quickly you need them broken in.

[acebobby]

I thought I would pull this old post up since winter is here!

I have just stuck a pair of dunlop qualifiers on my bike, and if its not wet its freezing here, need to get them scrubbed in!

[bll1184]

I'm glad you found this thread. I' have been looking for some info about this for the last day or so. I also just bought a new set of m3's and really debating whether or not to put them on or wait until spring. been thinking of lowering the preasure a little from the max preasure to see how that feels. I read in another thread that really only applies to two up riding is that correct?

[hubbard_28]

I just put my bike on a stand, whack the throttle, and hold some 100 grain sand paper up against it for about 15 minutes. Kidding. I ride street for about a week at least before putting it on the track, and my first few laps are cautious, but after that they're just fine. I ride Pilot Powers, and don't have tire warmers, so my first 2 laps in summer, and 3 laps in winter every session are dedicated to warming the tires.

The only time I've had a problem with Pilot Powers was on Firebird West after they had ATV trackday. They literally cover about half the track with dirt, and try to clean it off afterwards. It takes a while to get the track nice enough to really push it.

[acebobby]

ha ha thats funny, I have actually known of people that rough up the tyre with sandpaper! I will be doing all my riding on the steet as cant get winter track time here, its just finding a comfortable angle, as I had bags of confidence in the pilot power 2CTs and do not have the same confidence in the qualifiers. (came off at low speed), I should definately know better than too mix new tyres, lean angle, and cold slippery surface, there can only really be one outcome!

[acebobby]

I'm glad you found this thread. I' have been looking for some info about this for the last day or so. I also just bought a new set of m3's and really debating whether or not to put them on or wait until spring. been thinking of lowering the preasure a little from the max preasure to see how that feels. I read in another thread that really only applies to two up riding is that correct?

 

I am not sure about pressures, from what I can gather it seems to be a personal thing, I know that honda recomends that for my bike 42 psi rear whatever type of riding you do, but my friends GSX600R recomends 42 psi rear with a pillion and 38 psi solo, that seems more realistic to me, but then I read what will says about the tyre cooling quicker than it can heat up!

[Balistic]

The base track pressure for most all tires is 31 front and 29 rear.

 

The recommended pressures are for max load and speed the tire is rated for and have nothing at all to do with traction.

 

A radial tire at 38 psi on a sport bike single up might as well be a bias ply, it will not flex enough to realize any gain from the construction.

[bll1184]

The base track pressure for most all tires is 31 front and 29 rear. The recommended pressures are for max load and speed the tire is rated for and have nothing at all to do with traction.A radial tire at 38 psi on a sport bike single up might as well be a bias ply, it will not flex enough to realize any gain from the construction.If 31 front and 29 rear is a base track preasure; then what would be a good aggressive street riding base preasure? I run m3's if that makes any diff. on a 01 6r

[hubbard_28]

The base track pressure for most all tires is 31 front and 29 rear.

 

The recommended pressures are for max load and speed the tire is rated for and have nothing at all to do with traction.

 

A radial tire at 38 psi on a sport bike single up might as well be a bias ply, it will not flex enough to realize any gain from the construction.

On track I run 28/28. I was told that in the cold weather I need to get my rear down to 26. I haven't tried it in the cold yet, but the 28/28 works just fine.

Should I drop the front in the cold also?

[Jaybird180]

I thought I would pull this old post up since winter is here!

I have just stuck a pair of dunlop qualifiers on my bike, and if its not wet its freezing here, need to get them scrubbed in!

There's a recent article in Sport Rider mag about scrubbing tires. Seems credible to me.

[acebobby]

I thought I would pull this old post up since winter is here!

I have just stuck a pair of dunlop qualifiers on my bike, and if its not wet its freezing here, need to get them scrubbed in!

There's a recent article in Sport Rider mag about scrubbing tires. Seems credible to me.

 

What does the article recomend doing? I normally scrub in the way will said by gradually increasing lean angle untill the shiny surface is worn off!

The problem I have at the moment is that the weather here is now below freezing and the roads are all dirty and covered in salt!

[Jaybird180]

I thought I would pull this old post up since winter is here!

I have just stuck a pair of dunlop qualifiers on my bike, and if its not wet its freezing here, need to get them scrubbed in!

There's a recent article in Sport Rider mag about scrubbing tires. Seems credible to me.

 

What does the article recomend doing? I normally scrub in the way will said by gradually increasing lean angle untill the shiny surface is worn off!

The problem I have at the moment is that the weather here is now below freezing and the roads are all dirty and covered in salt!

IIRC That's basically it. It recommended against weaving too. You should read it.

[acebobby]

I thought I would pull this old post up since winter is here!

I have just stuck a pair of dunlop qualifiers on my bike, and if its not wet its freezing here, need to get them scrubbed in!

There's a recent article in Sport Rider mag about scrubbing tires. Seems credible to me.

 

What does the article recomend doing? I normally scrub in the way will said by gradually increasing lean angle untill the shiny surface is worn off!

The problem I have at the moment is that the weather here is now below freezing and the roads are all dirty and covered in salt!

IIRC That's basically it. It recommended against weaving too. You should read it.

 

 

unfortunately we dont get that mag here in the UK!

[Balistic]

The interesting thing about tire pressure is what it does to the tire. You want the tire to flex so it will generate heat and get to a temp in the 180 to 200 range. Too much flex and too much heat, you also may have a loss of feel. With the exception of the new low pressure tires (18 to 23 psi) there is a balancing between generating heat and disipating heat.

 

When you lower the pressure you expand the contact patch and that is how the tire convects heat out, so while you are getting more flex and heat by lowering the pressure you are also increasing the convection out of the tire, sometimes to a net loss of temp in the tire.

 

The most important thing is that you get the tire up to temp, at 38 psi it is unlikely you can get a rear tire up to temp.

[acebobby]

The interesting thing about tire pressure is what it does to the tire. You want the tire to flex so it will generate heat and get to a temp in the 180 to 200 range. Too much flex and too much heat, you also may have a loss of feel. With the exception of the new low pressure tires (18 to 23 psi) there is a balancing between generating heat and disipating heat.

 

When you lower the pressure you expand the contact patch and that is how the tire convects heat out, so while you are getting more flex and heat by lowering the pressure you are also increasing the convection out of the tire, sometimes to a net loss of temp in the tire.

 

The most important thing is that you get the tire up to temp, at 38 psi it is unlikely you can get a rear tire up to temp.

 

 

This is very interesting information, I should probably try to lower my pressures a few psi at a time to see and feel the difference. When you have a tyre at optimal temperature, 180 to 200 degrees, is this surface temperature we are talking about, sometimes when I stop I feel my tyres to see if there is much heat in them, if they were at optimal temp would they be unable to touch without burning my hand?

I like to understand how things work and why things happen and your descriptions have been really helpful to me in educating myself in how tyres perform,