Tire Pressure and SAG

[Burnall4]

What tire pressure should I run Cold and Hot for Mich' Pilot Powers?

Also I am attempting to set my SAG correctly and I am reading 40/38 mm front and 30/25mm in the rear to be a common setting for any sport bike. I have a 05 Honda 600rr and I am 5'9" @175 lbs. Is this the correct settings or should I look at a more specific setting for my bike and my build?

Thanks for your help!


Gray

[DeltaHotel]

For Pilot Powers on the track, I'd say about 30 rear and 31 front (cold pressure).

On the suspension sag... here's a general guideline... (you need a couple of friends to help out here)

NOTE: I assume your numbers (in your post) may refer to differences between Rider and Free Sag. But I'm not sure. In any case, perhaps you know all of this already. If that's so, please don't take offense. I decided to post a bit of the details in hopes it would not only answer your questions about optimal sag numbers, but may also be of potential benefit to others that have yet to tackle suspension setups for their bikes.

REAR:
First you need to measure Full extension. Without a center stand, you must support the bike by the rearsets or have friends lift the bike... you need for the swingarm to fall and extend freely and fully. Then, measure from a specific point on your axel nut to a specific point on your subframe or rear body work. Have the same person measure each time, and be very precise. Maybe put a piece of tape on the tail above the axel and mark a line on it so that you can measure from this same point.

Next, you need to measure Free Sag... which is the sag of the bike under it's own weight. You do this by taking two measurements and averaging the two. First, with the bike resting on it's own weight and someone supporting it in the front to keep it level, press down hard on the rear and let it up VERY gently until it settles. Measure now. Next, lift up on the tail and then let it settle back down VERY slowly and gently. Measure again. Average these two to get your Free Sag. Note the suspension will settle in different places due to stiction. It's critical you account for this. If the difference between your two measurements is more than about 5mm, that's too much stiction and you have the suspension serviced.

Finally, you need to measure Rider Sag. This is done just like you measured Free Sag, but with you sitting on the bike. Again, someone must support the front. Then have your measure-person take the two measurements to account for stiction. Again, be very precise.

Let's say your full extension was 400mm.
And then your measurements for Free Sag were 392mm and 388mm. So Avg = 390mm
And then your Rider Sag numbers were 368mm and 372mm. So Avg = 370mm

So your Free Sag = 400 - 390 = 10mm
And your Rider Sag = 400 - 370 = 30mm
And your stiction = 4mm... really a bit much, so less is better here (and again, >5mm is a red flag)

These are the numbers you want as an outcome... ~5-10mm Free Sag and ~30mm Rider Sag.
Of course, your actual measurements will differ, but that's the type of sag you want to see, in the end.

FRONT:
On your front forks, it's the same process. You'll want to measure from a fixed point on the fork (for USF) or the steering head. Use tape to mark a line, if it helps. And measure very precisely, just as you did for the rear.

On the front, you are shooting for ~15-20mm Free Sag.
And ~35mm Rider Sag.

And on the stiction, you would consider anything >10mm a red flag.
You'll have more stiction on the front, and that's normal. Exceptions are very high dollar suspension systems.

I hope that helps. :)

Don

[Burnall4]

Wow thanks Don that does help, that does help! and yes I was talking about free vs. rider sag!

[soxxerms]

i am running the bridgestone 002's

but im about 215lbs running a ninja zx10r

which i know has lots of power but i dont wont it to be a disadvantage and breaking the tire loose on turns. i was running about 36 front and rear and i found out that is to much but ya know it someone else's opinion.

i heard the pro's running about 20 lbs but they are doing and running twice the better tire etc and they are lighter in the seat than i.

i was figuring the 30lbs range might be good or 32 but just curious from those on the track and the cr's what you think before i hit the track.

[mugenej8power]

Great info!

[DeltaHotel]

i am running the bridgestone 002's ... i was running about 36 front and rear and i found out that is to much but ya know it someone else's opinion.

i heard the pro's running about 20 lbs but they are doing and running twice the better tire etc and they are lighter in the seat than i.

i was figuring the 30lbs range might be good or 32 but just curious from those on the track and the cr's what you think before i hit the track.

20 psi on a BT-002 ??? :confused:

I would not recommend that. Nor would I run it as high as 36psi (cold).

I'd go with about 30psi rear and 31psi front (cold).
Or if hot (right off the track), shoot for about 34psi front and rear.

Don

[07yzfr1]

Don, when you measure rider sag, does the rider need to tuck down on the tank as if they were running down a long straight or just sit straight up?

[DeltaHotel]

07yzfr1...

There's no need to worry much with an agressive tuck when measuring sag. Nor would I sit up or lean back in a position that is never where you'll be while actually riding. Not that you'll displace a huge amount of weight fore/aft anyway. But just sit comfortably with your hands on the bars.

Don

[BLARNEY]

07yzfr1...

There's no need to worry much with an agressive tuck when measuring sag. Nor would I sit up or lean back in a position that is never where you'll be while actually riding. Not that you'll displace a huge amount of weight fore/aft anyway. But just sit comfortably with your hands on the bars.

Don



Don, your first write-up was excellent. :agree:


This however...... :wow: you need to be in your normal riding stance to get it right.


Tom

[DeltaHotel]

Tom...

If we are trying to optimize suspension setup for track conditions, then our body position is going to vary depending on many factors (rider style aside, we tend to sit up when braking hard for corners, tuck very low on straights, low and far to the side on corners, etc.). So there is really no "normal" position, and I think for most riders the weight distirbution does vary a bit as they move around on the bike.

This is why I suggested to just sit with hands on the bars, comfortably (much like your position in your avatar). On any sport bike, that's going to put you in a forward leaning position. Yes, you could tuck all the way down, but again... that's not going to make much of a difference, and it's only going to represent one of the many positions you use on the track.

Am I missing something?

Don

[BLARNEY]

Best practice by every professional I have ever seen.

And I have seen and talked to many.

You are correct about the dynamic part of it..... however, during cornering you
are in a relatively specific position front / rear that seems to be best
approximated by sitting on the bike in a tuck.

Most professionals even have the bikes in their leathers as they all seem
to think that makes a difference as well.

Tom


Tom

[DeltaHotel]

Thanks for stepping in for the clarification, Tom.

Tucked it is then. Although... I think I'll go out and experiment a bit just to see how much of a difference I can measure (sag, front and rear) when tucked tight vs. a more relaxed position. Just curious. :)

And I agree on the leathers and gear... the weight of that stuff adds up. So that's a good point.

Thanks again! :cheers:

Don

[Burnall4]

Will anyone be at VIR, or will there be someone there you think that can help me adjust my SAG i have played with it and well I haven't been able to get it right. I know I am doing something wrong, yet it seems so simple...

Gray

[DeltaHotel]

Gray... I will be at VIR full on next Monday. Drop me a PM if you're planning to be there on that day. I'll be happy to help you out.