Bridgestone BT45 front tyre 'saw-toothing'

GregT said:
Too much pressure can cause this also ..
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Interesting thought, Greg.  I'll take a pocket gauge with me next time I'm out.

Xav said:
Is that the problem could be a bad agreement between the front and rear suspension ?
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Je pense pas, Xav, meme si je dois avouer que je ne suis pas expert dans le sujet  ::).  Tout semble fonctionner - plus ou moins -  ;) comme il faut/comme normal ... (On dit "Dents de scie"?  Merci! ?a peut m'aider ...) 

Grant said:
Is this with panniers on and loaded?
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No panniers, Grant, and normally solo (and I do up the pressures when riding two up).
 
Laverdalothar said:
Forget about Laverdas specifications, they were for different tires! Each tire has a different specification and you need to listen to the tire vendor ..
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Point taken, Lothar - it's why I use the manufacturer's spec  :D

Laverdalothar said:
Also please check if your tires are H-rated or V-rated.  I was told that the H-rated ones are not as stabile ...
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BT45s are V-rated.

Laverdalothar said:
In addition to that, Xavier's suggestion to check the suspension is a good one
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Yup, point taken. Everything seems to be working ok (standard 38mm Marzocchis up front, with new oil/seals etc, Konis at the back); but I gotta admit I'm no expert when it comes to suspension  :-X)

Laverdalothar said:
I think that this effect is influenced by several factors ...
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Well, maybe that's it - a combination of factors.  But I would prefer that the tyre manufacturer would work these things thru, not leave it to the individual owner to try and work them out!  But maybe I'am asking too much ...  ::)

 
How old is the tire? There is a number showing the production week and year. Maybe the new tire sat on a shelf for a long time before being sold.
 
Quote from: Paul Marx on November 13, 2013, 15:51
Turn the tyre around, it'll even up the wear.Yeah, I'd already had that thought, Paul ...  So, stupid question  : why do front tyres have a specified direction of rotation?


So as you don't put them on the back.
Paul
 
Maybe having to pump them up until they are as hard as wood contributes to the "wooden" feeling I get from the BT's. Find the Michelins much more compliant, like the old much missed Avon Super Venoms. Not really going to run out of grip on any modern tyre but how they make the bike feel is very important to me..


    Keith
 
Ventodue said:
Well, maybe that's it - a combination of factors.  But I would prefer that the tyre manufacturer would work these things thru, not leave it to the individual owner to try and work them out!  But maybe I'am asking too much ...  ::)
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Point is, they can not do that for each and every bike in the world in combination with suspension differences, load, temperature and other factors varying...

I assume you have the GFK mudguard and you are not using a fork brace, right? It might (!!!!) also have to do with a bit of a flex in the Marzocchi, as the loads to that fairly unsupported area is quite high when cornering.

what also can make an effect is if you are holding the handle bars to tight. this does force the front to go where you think is right, but not where the corner needs it to be

next point why sometimes this effect even lasts, when you increase the pressure: to stiff front fork. if the suspension is adjusted to a to hard level, the tire has to compensate the lack of travel of the fork. This results in a slight "hopping" of the tire, which causes this effect.

so - either to much oil, to strong spring or to heavy oil in the front or you haven't really relaxed the front enough so it is kind of sticky in its travel. I would check this first and adjust the settings of the fork to work perfectly with the load you put on the bike normally (only you up or with tank bag etc.).

to the point of direction for the front tire: the profile would change if you change the direction. The profile is designed this way to help the wheel run more straight. It might wobble if you put it on the wrong way...
 
I quite like the soft-walled nature of the BT45 at 'lower' pressures. I feel the tyre is able to distort properly to achieve a good contact patch, leading to a high degree of confidence in cornering. It's a nice smooth ride into the bargain. I don't even mind a little bit of sqirming. Pump em up and it all gets a bit hard and jittery on my suspension setup. If the Michelins offer this, they will be my next call.  [Keith +1]
 
a 30 year old bike can be made into a beaut, just needs a bit of attention to detail here and there...

Who wants the true '30 years ago' experience. Not me for sure.
 
fuck me-just ride the ass off the fuckin thing-see sawing :-\-fuckin hell its a 30 yr old bike
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I tried that once on my old Rocketlll with an Avon Skidmaster (Speedmaster) that had worn  in a saw tooth shape. I'd gone out for a blast with Dave Degens on his new Dresda Suzuki 500 twin.  I had noticed that the bike squirmed a lot when the front brake was applied - surprisingly it worked Ok as I'd had it attended to by Joe Dunphy who specialised in sorting out drum brakes. After Dave had run out of petrol on the Kingston by pass and I towed him to a garage with him hanging onto my rear carrier - he went extra loopy on the way back - my R3 was slower on acceleration but caught up rapidly at higher speed - I tried to jump on the brakes hard and late at a roundabout and the f----ing thing went totally out of control and sent the bike crashing into the concrete roundabout with me following on my arse - of course the next car round was the old bill. He said "you Ok son?" - I was - so he said that I'd had enough trauma and didn't need him to add to it - a good bloke! Dave returned and had a monster snigger  then trailered my bike back to his shop for repairs. I did get the tyre changed that very day! - Regards - Phil
 
mine cup up too-put it down to hard trail breaking-but never find this see sawing prob-on me bevel their still gripping hard when near bald-am going back to 45,s on the jota-the rear demon squares off too quick when hyway runnin
 
Laverdalothar said:
I assume you have the GFK mudguard and you are not using a fork brace, right?
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Correct.

Laverdalothar said:
.. what also can make an effect is if you are holding the handle bars too tight.
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Not guilty - I'm Keith Code trained, see  :D

Laverdalothar said:
.. too stiff front fork. If the suspension is adjusted to too a hard level, the tire has to compensate (for) the lack of travel of the fork. This results in a slight "hopping" of the tire, which causes this effect. So - either too much oil, too strong spring or too heavy oil
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Ok, I can see where you're coming from, Lothar - thanks for the thought.

The springs are standard originals (!) (well, to the best of my knowledge  :)).  The last oil change was November 2011, 300ml of 10 weight.

The wiring tie that I have on one of the fork legs tells me the forks are staying within the middle third of operation on compression; and they seem to be supple enough when bounced up and down in the garage.  But maybe they're not responsive enuf on the open road? ...  I shall try and see.

Laverdalothar said:
...to the point of direction for the front tire: the profile would change if you change the direction. The profile is designed this way to help the wheel run more straight. It might wobble if you put it on the wrong way...
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Thanks.  Advice from tyre specialists on Tinternet suggest it has much to do with wet weather traction.  For example:
"Directional tires are primarily about wet traction. As a general rule, directional tires will have an "arrowhead-like" tread pattern - it seems to point in the direction of travel.  If you mount a directional tire backwards, the only problem caused is wet (or snow) traction. It does not affect wear, pull, dry traction, ride, or any other characteristics."

And:
"Directional tyres disperse water that builds up in front of the tyre more effectively, reduce road noise, and improve directional stability.  They must rotate in the right direction and this will be clearly marked on the sidewall of the tyre.  If a directional tyre is fitted the wrong way round, the tyre won't be dangerous, but you won't gain any of the benefits of it's design."

Laverdalothar said:
Point is, they can not do that for each and every bike in the world in combination with suspension differences, load, temperature and other factors varying...
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Yes - but within limits.  If a tyre that a manufacturer sells for mounting on a specified make & model bike becomes - frankly - dangerous after 3,000 km of standard operation, than I reckon I'm in my rights to complain!
 
Had the same thing happen to the front BT45s on my FJ1100.
Got worse after I fitted new EBC discs and sintered pads.
2,500 miles out of a front 5,000 out of a rear.
Bridgestone rep at the Scottish show said brake earlier or slow down.
 
Craig,

As you well know, the RGS is no featherweight, especially with the factory panniers, even more so when laden... reckon it's well over 370kg with me on board.

0.2bar more on the rear 130/80 on the 3.5" rim.  Surprisingly, wear is not an issue with the rear tyre, usually get more than 8000km out of it.  Front is past its' best at 3000, needs replacing at 5000 latest.

Heavy braking will of course accentuate the saw-tooth effect, wonder what will happen once I up-rate the forks and brakes?  Incorrect suspension set-up will literally chew up the tyre (saw lots of those at the Classic Days in Spa :D), the saw-toothing would be the least of your problems.

piet
 
Paul,

Mounting direction of tyres has more to do with their construction than tread pattern.  Tyres meant for front and rear fitment will specify alternate fitting directions (TT100, Avon Roadrunner).

The outer layer of rubber has an end... this overlaps the layer beneath.  The direction of fitment avoids the end having a "leading edge" to the most expected load.  On the rear, the the edge will be facing against rotation so that acceleration forces on the tread do no unravel it, braking forces on the front tyre act in opposite direction, hence the different fitment.

Once fitted a Metzeler ME33 the wrong way round and was too lazy to correct it.  Always wanted to, but in the end I wore it out as it was, without the slightest issue, including wet weather riding. 

piet

 
I was talking to a bloke the other day that got booked for having the rotation arrow on his front tyre pointing the wrong way. He tried to explain to the cop that the arrow was labled "rear" and it should go the other way on the front. But the cop was having none of that rubbish, and slapped an unroadworthy sticker on the bike.  ::)

Cam
 
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