Input please: strange behavior after tire change

[EricV]

Hi gang. I'm looking to the collective and more experienced DS crowd to try and solve a riddle that's driving me nuts, and it also concerns me (as to my safety, and the health of the bike.) It's a TE 630 w/ 2K on it- just did a rear tire change, as well as going to a 14T CS. The new tire is a T63, which was balanced.

The issue is that upon riding it, and entering the first very low speed turn (neighborhood), I noticed a very distinct "squishiness" as I turned. It's fine in a straight line- solid, but as I would turn it would feel just like (if you can imagine what this would feel like) riding on a rear wheel with all spokes very slightly loose (enough to keep wheel feeling fine straight) and then when leaning over slightly like the wheel would "give." Very disconcerting. Almost like it's sliding ever so slightly, enough to feel it through the handlebars. Hard to describe, but I hope you get what I'm trying to describe. No squishiness in a straight line, nor when I apply rear brake, or accel. So here's what I've done...the obvious stuff:

Checked/re-checked the wheel alignment, by measuring each side from center of swingarm pivot bolt to center of axle.

Ensured that wheel is true- it is. Again, no odd behavior in straight line.

Ensured that rear sprocket is true.

Ensured that rear disc is true.

Chain tension is proper.

Spokes twang right all around- tension seems fine and again wheel is true.

When on stand wheel turns normally...no warbling or anything amiss. Grabbing it side to side/top to bottom for to and fro play (such as bearings) yields nothing unusual.

This is driving me nuts...can't figure it out. In 35 years of riding I've never experienced anything like it.

Now I can't help but think that perhaps, just perhaps, it's the T63. It's a very rounded tire (which on the tarmac means it'll heel over super easy when turning) and it has pretty tall knobs, which I guess could give and create this squishiness sensation. I sure don't recall this sensation on the new Karoo though, granting it's a different beast.

Sorry to go long folks. If there's something bone-headed I'm overlooking please chime in. Thanks!!

Eric

 

[jtemple]

It could be tall flexy knobs and a new tire causing it. A tire that hasn't been scuffed in still has mold release agent on it, which is pretty greasy. If you do some searching around on the various sportbike forums, it is full of stories of people wiping out while turning on a new tire.

 

[JoiseyJanet]

Low tire pressure?

 

[1lunger]

I agree with jtemple. New tire with tall, soft knobs. I got that with the MT 16 when it was new. It slowed my ass down on the road! Give it a few heat cycles and it should feel better.

 

[SilverBullet]

Low tire pressure?

or properly torqued rear axle nut? If that sucker is not tight you'll get a feeling like this. It's not the T63, that's the best knobby for the pavement you'll find. Unless you got a defective one and if defective to that degree I'd think it wouldn't be able to be balanced.

_

 

[Fast1]

first off.. never..ever take a brand new tire into turns aggressively.. It will take 50 or so miles just to get the mold release compound off the tire and for it to grip properly... ok I see this has been mentioned and there are numerous stories from dealerships where a new bike (crotch rocket) is purchased by an unknowlegable noob and them hitting the ground within the first few aggressive turns.

Also a well worn DS tire will develop a squared off profile which will make laying the bike over difficult in comparison to a new rounded profile DS tire. This can sometimes be more apparent with the front tire than the back, especially in off-road situations.

 

[EricV]

Huge thanks gang, really.

Joisey: To start out, for road-going, it's currently at 28 psi. I may have to go lower, the tramlining effect seems to have increased. With such a rounded profile I don't want it over-inflated...w/ it's profile that would leave like a quarter sized contact patch.

SilverBullet: I need to look up the proper torque value, I'll admit, but if anything it's probably a tad tighter than it should be. I know it's where it was prior to the change as I'd put a paint signature mark on it when I had a flat towards the end of last season...and had no issues prior to this. You're right- the T63 has a rep for good road manners, which is part of why I bought it and why I'm perplexed. On that note thanks to all for contributions to the tire thread as that really helped me select a tire.

Jesse: Yeah, I keep going back to the tall knobs myself. You're absolutely right about the mold release agents..something I'm cautious about. In this case I don't think that's factoring in though as these are quite slow turns and I have (for troubleshooting and for sh*ts and giggles) laid on the throttle in these scenarios to see if it's a true slip or some other type of squirreling...and it's certainly the latter.

Lunger: Yeah, it may just be. I hope to ride it again this evening, keep double checking things, and perhaps some heat cycling/scrubbing may help.

Thanks again. If anyone has other thoughts please chime in and I'll be glad to let everyone know how this shakes out. If I don't get out on it tonight then my next chance is Saturday, and I should be able to really take it out for a long stretch and also try it out off-road, which I am dying to do.

 

[EricV]

first off.. never..ever take a brand new tire into turns aggressively.. It will take 50 or so miles just to get the mold release compound off the tire and for it to grip properly... ok I see this has been mentioned and there are numerous stories from dealerships where a new bike (crotch rocket) is purchased by an unknowable noob and them hitting the ground within the first few aggressive turns.

Also a well worn DS tire will develop a squared off profile which will make laying the bike over difficult in comparison to a new rounded profile DS tire. This can sometimes be more apparent with the front tire than the back, especially in off-road situations.

Thanks, as mentioned this is happening in low/slow speed situations...just neighborhood type riding taking the turns. Been riding many years- wouldn't think to hit a turn aggressively on a new tire. Point about squared off vs. rounded is spot on, and while this thing does heel over much more easily (as we'd expect) the definitive squishiness is more pronounced than anything I've ever experienced...to the point of re-checking everything ad nauseam and posting here. Thanks for the input.

 

[Fast1]

From you posts I can tell you are very cautious and just want to ensure everything is right. Not sure if you mentioned air pressure you run and is the new tire a different overall diameter, maybe causing a change in geometry a bit from the worn one?

You may just be experiencing the differences in DS tires and how road oriented the Karoo was. The T63 aired down for dirt might transform your TE into a 100% better dirt bike.

Did you change the front too?

 

[CJBROWN]

Sounds like a new-tire feeling, although I never experienced the same thing.
Pressure is good.
Tires are softer when new and harden up after some heat cycles, as mentioned, and will feel firmer with a few hundred miles on them.
The T63 has a very strong carcass and side wall, so with 28psi you really shouldn't feel sidewall flex. Knob squirm is probably more like it. This is a common complaint with the cheaper tires, like shinkos and kendas, like the K270. It's also the reason for the shorter knob height on the FIM conforming tires. Again, mine have been solid from day one, so I dunno.
Are you sure your air gauge is calibrated? When we air down for trails, like 18lbs or so, I have done 60 plus mph road runs with them low and still no handling issues. So even if your pressure is lower than you think you still shouldn't have any issues. I keep them about 25 for road for better wear. You might try 23-25 and see if they feel different. Could be just too much air pressure. Knobs don't generally run that high, not like a street tire.

Definitely cuold be you're feeling the difference from a very round profile compared to a squared-off used tire. My streetbike gets more floppy in turns as the tires get squared off.

Just a lot of off-the-head thoughts here, but I'll bet its too much air pressure. Try 25 and see how it feels. They buzz pretty good about 40-45mph, like a truck with mudder tires.

 

[EricV]

I do tend to be cautious and it is my nature to tune in on idiosyncrasies.

Nope- still on the stock front, though that should probably go also. Overall wear has been pretty good on that one, with the exception of slanty/stepped knobs (which is a me thing more than a tire thing as I tend to be aggressive w/ the front brake on streets.) Now Fast1 you have hit upon something I've been giving real thought to- the geometry change, even if slight. It is a 130/80 so yeah, there is that smaller diameter now which relates to the front and the feel, of course. CJ- also good advice, as always. I'll def try the 23-25 range and I did, btw, use two diff air gauges just in case.

In the end (or at least so far, and w/ your input) I'm thinking that it may indeed just be the most vivid feedback I've ever felt from all these combined variables at once: the tall knobs, pressure, the slight change of geometry, the roundness, heat cycling/hardening. It's just thrown me off as I've just never felt such an obvious squishiness before.

Thanks all- really appreciate the feedback and the forum. I swear this Internet thing is gonna be huge one day.

 

[mike54]

I had similar when I put a Stonemaster on my tiger. Playing with the psi (lowering it) cured it instantly.

 

[Travis Shrey]

The only thing you did was a tire change and now it feels funny. I think it is the tire (Occam's razor and all). I'm betting on the mold release.

Find a sand, dirt, or gravel road and do a couple of 20 foot burnouts. Dig a nice deep trench so that the side lugs get abraided as well.

I didn't know about the mold release with my last dual sport; I threw on a front and back pair of D606 and damn near dumped the bike just pulling out of my driveway at 5 mph

 

[EricV]

Thanks Travis. I agree w/ the Occam's approach on this, which is why it puzzled me so much. Now I know it's not the mold release agent as it's not a slide, per se...it's most certainly this squishiness feeling (but, being comfy enough w/ bikes, I've experimented w/ some added throttle as the feeling sets in to see if it's inclined to break loose further, and it's not.) So that, and playing w/ pressure, reinforces to me it's a knob flex issue. As mentioned previously I've never experienced anything so pronounced, which is why I posted. Also as mentioned I think it's exacerbated by the slight change in geometry, the roundness of the T63, etc. Last night I did go w/ CJ's recommended pressure (dropped it to 24) and that certainly helped...and I think w/ more heat cycling it's getting better. I like your suggestion also- because it's bound to bring the tire along further and it's just plain fun. I'm hoping the weather holds out tomorrow and I can get the thing off-road to really feel it out and have fun.

 

[CJBROWN]

I have heard the 'mold release' term is a bit of a misnomer as the majority of the tire manufacturers don't use anything any more, particularly for anti-air pollution regs. The molds are polished, or chromed, and the tires come out smooth and shiny, the way the end-buyer wants to see them on the rack. What they really need is a few heat cycles and some scrubbing in from road contact to make them stick better. Not sure how all this applies to offroad tires, but the surface of the knobs need that scrub in and the new rubber is more flexible. The term knob squirm seems to come from time to time. Some tires are more prone to it. It is also what makes some of the more aggressive offroad tires less desirable for on road use, like 606's, Motoz, etc. and most non-dot knobbies.

Here's some interesting responses on an inquiry made to several of the tire companies, from a sportbike forum:
http://www.gixxer.com/forums/showthread.php?t=176572

Eric, did you add a rim lock? If not then be careful of any hard dirt spinning with any pressure under 20lbs. If the tire spins on the rim it will pull the stem out of the tube. I know, you already knew that.

 

[EricV]

Thanks CJ. Good info and interesting reading. Yep- I do know about the risk/potential consequences of not using a rim lock and really waffled on doing it or not. Read many posts here and on ADV from those advocating for and those who have had no issues without. Ultimately, this time around, I opted to go w/out and hope I do not regret it. I'm one who keeps the tube/valve stem lock nut spun upwards so that it seats against the base of the valve cap- that way it affords me the opportunity to see if it has moved at all (which would result in it being slightly angled) and also slightly diminishes the odds of a sudden shear-off (granting that even w/ the lock nut spun upwards and away a fierce enough force would still shear, but you guys see what I mean.) I had a DRZ I didn't run a lock on but the reality is that w/ it's torque it wasn't a huge risk and w/ my old KTM I did run a lock.

 

[Travis Shrey]

I have heard the 'mold release' term is a bit of a misnomer as the majority of the tire manufacturers don't use anything any more, particularly for anti-air pollution regs. The molds are polished, or chromed, and the tires come out smooth and shiny, the way the end-buyer wants to see them on the rack. What they really need is a few heat cycles and some scrubbing in from road contact to make them stick better. Not sure how all this applies to offroad tires, but the surface of the knobs need that scrub in and the new rubber is more flexible. The term knob squirm seems to come from time to time. Some tires are more prone to it. It is also what makes some of the more aggressive offroad tires less desirable for on road use, like 606's, Motoz, etc. and most non-dot knobbies.

That may be true for road tires, but I know for a fact that D606 come with some kind of greasy, slippery coating on them. Like 'wipe your finger across a knob and then your finger is slippery' coating. Not sure about the T63.

 

[CJBROWN]

Michelin is one of the ones that said they do use a 'mold release' agent of some sort.

And yes, the angle of the valve stem is a good advanced warning on rim slippage. I always run one but not for possible slippage for normal running, but in the case you do get a flat and not realize it 'till it's run down enough to slip. Or if you have to run a ways on a flat.

On my 250 I run a trials tire, MT43, and it tends to slip even with a rim lock. I've got another one to add when/if it gets dismounted again. So far it has slipped the opposite way, from braking. But then I run 6-8lbs in that one.

A rim lock does make it more difficult to balance the wheel. This last time I tried adding wheel weights to the inside of the rim, in the valley, a couple of ounces to offset the lock. It worked out well but makes mounting just a tad more difficult as the weights fill up the valley some. Positioned between the spoke nipples they are really not much taller. I use duct tape instead of a rim strip, makes mounting and dismounting easier, especially getting the valve stem through. If the strip slips it's impossible to get everything lined back up. Doing it in the shop is one thing, in the field is another.