Tire Pressure

The 2010 WR250R that I recently acquired has tires that I believe are slightly oversized. On the rear is a Michelin T-63 130/80-18 and on the front a Michelin T-63 90/90-21. Initially not realizing they were not stock sizes I kept them at 18 psi front , 25 psi rear per the Owner's Manual.
Does anyone here know what they should be set at for pavement and off-road?

Off road pressures are around 10ish, there are variables like whether you have rim locks and what terrain you are on that should affect your psi.
On road I also run low pressure with good results, though most people don't recommend it. I run about 12psi front and rear on road, and haven't noticed any issues. What I have noticed is a reduction in the harshness of bumps in the road.
I would recommend you start with 16psi front and rear and go from there. I wouldn't recommend high pressure in the rear tire unless you have passengers or heavy luggage regularly which is what I assume yamaha is taking into account with their recommendations.

When you replace your rear tire you might want to consider downsizing, I have heard that a large rear tire hurts handling. I don't have personal experience with this, but I did look up what size tires offroad race bikes run and they stay with small tires so a bigger tire does not equal better.

There are a lot of threads on tire psi, if you search around you can find lots of information.

Your front is very close to stock size (it's the same T63 I run without issue).  130/80 rear is just slightly over stock size (I run 120/80 T63 on the rear).

IMO your pressures are way too high.  I run 15-17 PSI front & rear, finding it gives good all around street/dirt traction.  I often contemplate trying lower pressures (since I run UHD tubes with dual rim locks throughout), but have lots of sharp edged rocks around here so haven't dared yet  

beee wrote:

 I wouldn't recommend high pressure in the rear tire unless you have passengers or heavy luggage regularly which is what I assume yamaha is taking into account with their recommendations.

Surprisingly the WR250R Owner's Manual (and the sticker) says to inflate the rear tire to 29 psi when "loaded". However I'll bow to the collective experience and go with the lower pressures you guys have found work.
Thanks guys.

No surprise IMO.

The owners manual coarsely defines recommended tire pressures, basically one-up 0lb-198lb load as 25psi rear, or two-up 198lb-408lb load as 29psi rear.  Also remember they classify the bike as a street bike.

In dirt these pressures result in one slippery ride.  Real world psi numbers work much better.

I run 0 psi, but that's because I have tire balls.

keetmanaa wrote:

Surprisingly the WR250R Owner's Manual (and the sticker) says to inflate the rear tire to 29 psi when "loaded". However I'll bow to the collective experience and go with the lower pressures you guys have found work.

I think this subject is almost like "what oil should I use in my bike".

In my opinion, you have to find the tire pressure that works best for you - and that itself is dependent on what tires you're using, the "normal" riding conditions, etc.

I run the tire pressures as per the owner's manuals.  Did it with the original Trail Wings and all the freebee Wings I got when people were hurriedly discarding them, and now do the same with the Heidenau's I'm running.

My riding tends to be true 50/50 dual sport with lots of fun twisties as the slab portion as that's what the roads here are like.  The forestry roads and old exploration roads are all hard gravel or just plain old hard dirt.  My riding style is dirt road tourist - I'm usually puttering along soaking up the views, not charging along from one corner or obstacle to the next.  Mud is seldom encountered.  Very seldom any singletrack.  I often have fishing gear, camera gear, camping gear, etc riding in the Giant Loop, and I'm around 210 lbs dressed to ride.  

So under those conditions, recommended tire pressures work well for me.  If there was a lot of mud, roots, single track, aggressive riding, etc., then I'm pretty sure not only would different pressures be better, but different tires as well.

Bottom line: choose pressures that will fit your riding environment and style. Lower tire pressures should not necessarily be considered the default starting point, particularly if you ride anything like true 50/50 dual sport.

Topeak Mini Morph Bike Pump
http://www.amazon.com/gp/product/B000FICCQC/ref=oh_details_o00_s00_i02?ie=UTF8&psc=1

This is what I have. It is one of the lightest pumps that is easy to use. Its easy because it has that little hose that attaches to the stem, then you rest the pump on the ground allowing you to put your weight on it.

Please don't lump this in with oil. Oil will have no effect on bike performance, except maybe the placebo effect. Tires and tire pressure on the other hand will have the largest effect out of Anything you will change!

And don't get to wrapped up in psi. I went riding with this 60 year old guy from work. I learned something important. All ya do is push down on the tire with your hands. When it feels like its the right squishiness you are good to go.    Honestly at low pressure its probably more accurate then using a gauge because your hands take sidewall stiffness into account, measuring psi will not.

beee wrote:

Topeak Mini Morph Bike Pump
http://www.amazon.com/gp/product/B000FICCQC/ref=oh_details_o00_s00_i02?ie=UTF8&psc=1

This is what I have.  It is one of the lightest pumps that is easy to use.  Its easy because it has that little hose that attaches to the stem, then you rest the pump on the ground allowing you to put your weight on it.

Looks like a nice piece of kit.

But also won't fit in my flat repair fender bag kit, particularly with a couple of Motion Pro combo tire irons and spare tube already in there.  Which brings us back around to the gear you select for riding, whether it's tires, tank/tail bags, etc.  I have no doubt lots of people here say "It fits right in my ________".  In my case, for example, that pump doesn't but this does:



About half the length the pump that works for you, and gives the option of using CO2 cartridges as well.  Yep... smaller pump equals longer time to inflate tire via manual mode.  But for me, I'll take that to gain the compact size that fits my fender bag.

I think the takeaway is that what works for one rider - whether tires, inflation pressure, pump, etc - may not work very well at all for the next guy.

Quote :

Please don't lump this in with oil.

But I will.

There's almost as many opinions on best tire pressures as there are on oil.  You, for example, find squishy tire pressures work for you.  For my style of riding and where I ride, squishy tire pressures ain't a recipe for success.

Suggests to me that a thoughtful rider will spend a few hours in some representative terrain trying different pressures with the tires they are using to find what works best for traction and handling.  I'd say that's the way to go, rather than assuming that some unknown rider using some unknown tires in unknown conditions can give you the best pressures for your use.  Other riders experiences can give you a good place to start, and some factors to consider, but if a rider really wants to know what pressures work best for them, the best thing to do is go out and experiment until you find out for yourself.