[Kreylyn]

Ok Krey - I'll just nod and agree. Hopefully understanding will come later.

I'll add a little more info to help out with that...


Profile refers to the curvature of the tire from a cross sectional view. Like this...



Several pieces of information in this pic... the black curve is a sample of a tire profile with a closer to correct profile. The red is an example of a deformed profile from putting a tire too large for the rim on. The blue shows the section of the tire that can never touch pavement because it's pulled over way too far. The green lines are for referece for lean angle.

Tires flex as they are being used. This in part causes heat build up. The tires are designed with that in mind for the proper sized rim. When you start deviating from that proper fitment, the tire end up flexing more due to the mis-shapen profile. More flex= more heat build up and thus hotter tires. The hotter the rubber gets, the more it is likely to wear off.

Lean angle reference...



As you can see... there isn't much more room to go before your dragging hard parts.

So, for the situation of tires and rim matches...

Talking about the 4.5" rim.

The 150-170 seems to be the general range from minimal to maximal size for the 4.5" rim to keep with in the safe operational use. Each will have variable amount of heat build up with = use due to the change in profile. The profile will change between them because the rim always stays the same size, but the tire is wider the larger you go.

Now you also have tire aspect ratio to consider too. This is a number that specifies percentage of the width to = side wall height. Just changing aspect ratio can make a large difference because going smaller on the ratio makes the tread closer to the rim and makes the profile change more extream. Going larger on the ratio will allow for less distortion on the proper profile for the tire.

All of this is limited though with the tire sizes offered by manufactures. Sometimes the numbers will work out on being able to change the tire to another size, but the manufacture does not offer a tire in that size... so people "adjust" and then you run into the issues most people get by putting the wrong size tire on their bike.

Krey

[Omnivore]

I really want to give the Q2s a shot...but they're Dunlops...yech....

I really couldnt agree more with this comment. Dunlops were last on my list.... But I bit the bullet and bought Q2's anyway because of reports on them. I still am not a huge fan of Dunlop as a whole, wouldnt buy anyother Dunlop than the q2, but they sure made a great tire in the Q2. Q2's longevity sucks, but thats the price you pay for sticky ( I also drive the hell out of em). Normal summerish rain water pretty good traction still but REAL cold Mnt rain or cold standing water just the same as anything else, slippery!.

I'll add a little more info to help out with that...


Profile refers to the curvature of the tire from a cross sectional view. Like this...




Lean angle reference...





Krey

I see excel sheet app written all over this post lol

[TRPUT]

That second diagram had me pi$$ing myself Krey - remember the "failed senior physics" comment???

I get the first diagram - and have seen it posted up here before. And although I realise it is exaggerated to make the point, my 170 doesn't look much (if at all) out of profile, and I now have less unused rubber than on some previous 150s.

I put another 300 miles on them yesterday with the bike fully loaded. Getting closer to the edges and did touch down lightly with feet. No noticeable temp issue - in fact probably cooler than I've felt my previous 150. Will post photos when I have the chance to show what I'm talking about / dealing with.

But a huge THANKS for your time and explanations.

[05RedKat600]

Actually, not all that exaggerated.

[loudnlow7484]

That was based on the factory bias ply tires. Since it looks like you are running the RS, Dunlop happens to give recommended pressures... 36F 42R.

If you ever wander to Ohio, I owe you a beer.

I checked my pressure with a stick gauge instead of a dial (I should know better..... you just can't trust a dial after you've dropped it a couple of times)..... I had 31 up front, and maybe 33 in the rear. I bumped it up to 36/42, and now it's like a completely different bike! No more muscling through corners at all. I can't believe what a difference it made in making the thing lighter on its feet. I never would have tried setting the rear pressure that high if nobody had told me to. Factory sticker says 36 I believe, and the thought would never have crossed my mind to try it 6 psi higher than that.

I don't feel quite as confident that it's going to stick in the corners, though. Maybe that's normal, but it feels like little bumps/broken pavement that didn't upset it before are making it wiggle a bit now. Just how warm are the tires supposed to get? After a good long blast around some backroads, the tires are a little bit warm, but not hot by any means.

[thetable]

I checked my pressure with a stick gauge instead of a dial (I should know better..... you just can't trust a dial after you've dropped it a couple of times)

I've actually gone to all digital gauges and compare them against each other a couple times a year. After a couple years of use, they all still read within a few tenths of each other. The bourdon tube gauges don't stay accurate if abused at all, and it is hard to find a decent quality pencil gauge.

I don't feel quite as confident that it's going to stick in the corners, though. Maybe that's normal, but it feels like little bumps/broken pavement that didn't upset it before are making it wiggle a bit now. Just how warm are the tires supposed to get? After a good long blast around some backroads, the tires are a little bit warm, but not hot by any means.

The old rule of thumb is 10% expansion cold vs hot. Say you start out cold with 42, you should be seeing 46.2 hot. I would try dropping the rear pressure in 2PSI increments and see what you think. If it gets worse, then bump the pressure back up a pound.

Here is what I try to do:
Set tire pressures per manufacturers recommendations before the bike ever moves, making sure the tires aren't sitting in the sun or next to a heater or anything to make them warm.
Go ride for half an hour fairly aggressevely, hop off and try to check tire pressures as quickly as possible. Note pressure growth. If it's less than 10%, then drop a couple pounds, if it's less than 5% drop a few pounds.
Ride another half hour, adjust for feel, and repeat. I find it takes me almost a half hour of riding to get a good feel for the tire and changes to the pressure.
Now when you get home, park the bike, then check pressures the next morning, and now you have your cold pressure to aim for.

Oh one thing I did forget to mention, only adjust one thing at a time. Do the rear first, then the front. Bikes can be a bit tricky with what changes are doing what. Changes in the rear, can actually change the feel up front, so you can spend lots of time chasing a problem on the wrong end.

How warm is warm? How about just shy of uncomfortable?

It's nice to have mental confidence ... even if lacking in mental ability!

If there is a brief answer for someone who failed senior physics - can you explain why LONGER and HOTTER? (OD for the 150s and 170s is almost identical.)

I haven't forgotten about you, just working on coming up witha way to try to explain it that makes sense to anyone except me.

[loudnlow7484]

How warm is warm? How about just shy of uncomfortable?

No, more like kid-with-a-fever warm.

I'll try those methods the next time we have some riding weather..... and maybe I'll pick up a digi gauge while I'm at it.

[TRPUT]

I haven't forgotten about you, just working on coming up witha way to try to explain it that makes sense to anyone except me.

Thanks mate, but don't waste too much time and energy busting your brain. Krey managed to get through to a degree. And I'll post some pics when I get organised to at least show what I have is nothing like the 150 vs 180 profiles in Krey's first diagram.