BT45 standard rotation or reversed

Paawpabear

Ken Morse
Joined
Jul 13, 2008
Messages
68
Age
68
Location
Moore, Oklahoma
Bike
'06 ST1300
STOC #
7975
Please let me know which rotation direction you have installed your BT45 and why. I want to get mine mounted the best way the first time.

Sent from my XT1254 using Tapatalk
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
Seems to me that the tire maker puts those directional arrows on their tires for a very good reason, otherwise, like on some car tires still, there would be no arrow. Why anyone would question this logic is beyond me.
 
OP
OP
Paawpabear

Paawpabear

Ken Morse
Joined
Jul 13, 2008
Messages
68
Age
68
Location
Moore, Oklahoma
Bike
'06 ST1300
STOC #
7975
I only brought it up because some have said that it made a positive difference in the handling. I agree with you about the arrow, I just wanted to pick the other side's brain as to why they went the way they did.

Sent from my XT1254 using Tapatalk
 

T_C

Joined
Mar 8, 2012
Messages
4,341
Location
St. Louis, MO
Bike
2005 St1300
STOC #
8568
Forward rotation, as the design engineer made it.

Any improved mileage by reverse mounting is something they wanted to see.

Rubber is going to wear the same in the rotation. The tread is not affecting that. The tread just allows clearing of water and other foreign objects from under the tires contact patch. So when they design it with a rotation direction, it clears best in that direction.
 

970mike

Mike Brown
Site Supporter
Joined
May 6, 2008
Messages
6,167
Age
66
Location
Lompoc, California
Bike
07 & 12 ST1300A
SPOT
LINK
STOC #
8057
There is only one way to mount a tire when they have an arrow on them saying which direction of rotation.
 
Joined
Jun 3, 2006
Messages
3,512
Location
British Columbia
Bike
2021 RE Meteor 350
Another quirk to tire mounting showed up on a set of Pirelli snows we bought for the wife's Forester. They were marked such that only one side of the tire should face the outside. The inner half of the tread is substantially different than the outer side.
 

W0QNX

Blacksheep Tribal Member
Joined
May 30, 2006
Messages
3,311
Location
Pensacola, FL. USA
Bike
06/ST1300 19/R1250RT
2024 Miles
007437
My readings have led me to the belief that a rear tire on front should be mounted with the arrow backwards. The reason being rain evacuation out of the groove during braking on front. the grooves are opposite of back for rain traction. I've ran rears on front both ways and have found little difference. I normally mount them arrow backwards first and then rotate them when the scalloping gets bad.

I found this link (from Avon tires I think) that is a good read for my choice. From the link:

"If you are using a tire that has a directional arrow for rear rotation only and for some reason you want to put it on the front, make sure it is rotating in the opposite direction so you don’t aggravate the tread splice. Avon Tyres."

http://cyrilhuzeblog.com/2009/08/23/tires-directional-arrows-explained-by-avon-tyres/
 
Joined
Jul 8, 2009
Messages
1,307
Age
58
Location
Wallkill, NY
Bike
2016 FJR
STOC #
8541
I've tried both ways (tire direction that is) and noticed little difference. My tire guy still asks me which direction every time I drop of my wheel for new rubber. I tell him "surprise me" because I really don't care. More times than not he mounts them with the arrow in the direction of rotation.
 
OP
OP
Paawpabear

Paawpabear

Ken Morse
Joined
Jul 13, 2008
Messages
68
Age
68
Location
Moore, Oklahoma
Bike
'06 ST1300
STOC #
7975
I contacted Bridgestone about this when I spotted that half way through the life of my BT020s, the front tyre had been fitted the wrong way round.

The issue is nothing to do with the tread pattern or the wear life, it is to do with the way that the tyre is constructed. The 'rubber' compound is laid onto the carcass in a spiral, somewhat similar to the way that insulation tape is wound onto a roll. At some point there is an 'end' to the layer of compound. The direction of tyre rotation is set so that this presents a trailing edge to the road surface.

If the tyre is put on the wrong way round there is a chance that the end of the spiral layer of compound could get rubbed up.

I asked if I needed to have the tyre refitted. He said that it was up to me, but that I should keep an eye on the tyre in the meantime. I asked what I should be looking for.
He said that if the end does get rubbed up then the rubber compound will start breaking off in chunks. It will be very obvious.

I took it back and had the tyre refitted properly, not least because I wanted to point out to the people that did it that they had screwed up.
Very helpful. Thanks everyone for your input and help with this topic, I very much appreciate it.

Sent from my XT1254 using Tapatalk
 

W0QNX

Blacksheep Tribal Member
Joined
May 30, 2006
Messages
3,311
Location
Pensacola, FL. USA
Bike
06/ST1300 19/R1250RT
2024 Miles
007437
I contacted Bridgestone about this when I spotted that half way through the life of my BT020s, the front tyre had been fitted the wrong way round.

The issue is nothing to do with the tread pattern or the wear life, it is to do with the way that the tyre is constructed. The 'rubber' compound is laid onto the carcass in a spiral, somewhat similar to the way that insulation tape is wound onto a roll. At some point there is an 'end' to the layer of compound. The direction of tyre rotation is set so that this presents a trailing edge to the road surface.

If the tyre is put on the wrong way round there is a chance that the end of the spiral layer of compound could get rubbed up.

I asked if I needed to have the tyre refitted. He said that it was up to me, but that I should keep an eye on the tyre in the meantime. I asked what I should be looking for.
He said that if the end does get rubbed up then the rubber compound will start breaking off in chunks. It will be very obvious.

I took it back and had the tyre refitted properly, not least because I wanted to point out to the people that did it that they had screwed up.
Which is why a rear on front should be backwards. Maximum force against the splice joint is placed on the tire during heavy braking.
 
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
Which is why a rear on front should be backwards. Maximum force against the splice joint is placed on the tire during heavy braking.
Isn't the force applied to the front tire under heavy braking in the same direction as the force applied to the rear tire under heavy acceleration? Looking from the left side of the bike, I'm picturing the front tire rolling counter-clockwise, with braking forces opposing in the clockwise direction. Same with rear wheel acceleration, the pavement is providing a counter-force in the clockwise direction, which if overcome results in a rear wheel spin in the counter-clockwise direction. So it seems that the maximum force against the splice joint would be the same in both cases if the tire were mounted in the same direction for both cases.

I thought about this about long enough to type this reply, so please correct me where I'm wrong.
 

paulcb

- - - Tetelestai - - - R.I.P. - 2022/05/26
Rest In Peace
Joined
Jun 4, 2013
Messages
4,652
Location
Celina, TX
Bike
'97/'01 ST1100 ABSII
STOC #
8735
Which is why a rear on front should be backwards. Maximum force against the splice joint is placed on the tire during heavy braking.
That's why I mounted my BT45 backwards on the front of my ST1100.
 

W0QNX

Blacksheep Tribal Member
Joined
May 30, 2006
Messages
3,311
Location
Pensacola, FL. USA
Bike
06/ST1300 19/R1250RT
2024 Miles
007437
Isn't the force applied to the front tire under heavy braking in the same direction as the force applied to the rear tire under heavy acceleration? Looking from the left side of the bike, I'm picturing the front tire rolling counter-clockwise, with braking forces opposing in the clockwise direction. Same with rear wheel acceleration, the pavement is providing a counter-force in the clockwise direction, which if overcome results in a rear wheel spin in the counter-clockwise direction. So it seems that the maximum force against the splice joint would be the same in both cases if the tire were mounted in the same direction for both cases.

I thought about this about long enough to type this reply, so please correct me where I'm wrong.
Try imagining that the front is locked up and sliding. Now back to the rear, I picture the splice as a 45 degree cut going up from the pavement towards the back of the bike on the arrow forwards rear tire. During a "peel out" you would be swiping across the rear splice no problems. Now move that tire to the front (still arrow forwards) and lock it up while moving forwards. You're now sliding that tire with the 45 angle digging down towards the front which could make that 45 splice unwrap from the carcass. That's what I make of the whole arrow and rotation thing.

Also as I stated earlier I've ran them both ways way way longer then most would and couldn't find any sign of tire failure.
 
Last edited:
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
Try imagining that the front is locked up and sliding. Now back to the rear, I picture the splice as a 45 degree cut going up from the pavement towards the back of the bike on the arrow forwards rear tire. During a "peel out" you would be swiping across the rear splice no problems. Now move that tire to the front (still arrow forwards) and lock it up while moving forwards. You're now sliding that tire with the 45 angle digging down towards the front which could make that 45 splice unwrap from the carcass. That's what I make of the whole arrow and rotation thing.
That seems logical to me, but think of it another way. Elevate the front wheel and spin it. Then from below apply a frictional force to the bottom of the tire, which I think would be similar to the pavement forces being applied. As the tire rotates while slowing down, the swiping motion you described for the rear still applies to the front if mounted in the same rotational orientation. It goes across the splice. If reversed, the swiping would be against the splice.

Both scenarios potentially make sense to me, so I don't know what to think.
 

W0QNX

Blacksheep Tribal Member
Joined
May 30, 2006
Messages
3,311
Location
Pensacola, FL. USA
Bike
06/ST1300 19/R1250RT
2024 Miles
007437
Okay one more thought for you. If you apply the front brake and the tire is under enough friction to leave a skid mark as the tire turns which way will that skid mark go towards? The front tire tread force load under braking is opposite what you are picturing I think.

The tire rotates and slows and slides forward while the bike is forcing it's mass forward above the front contact point. The friction point at the bottom of the front tire is to the rear. Just like if you lock up the tire and drag the pavement under the front towards rear.
 
Joined
Mar 13, 2012
Messages
5,046
Location
soCal
Bike
'97 ST1100
STOC #
687
Okay one more thought for you. If you apply the front brake and the tire is under enough friction to leave a skid mark as the tire turns which way will that skid mark go towards? The front tire tread force load under braking is opposite what you are picturing I think.

The tire rotates and slows and slides forward while the bike is forcing it's mass forward above the front contact point. The friction point at the bottom of the front tire is to the rear. Just like if you lock up the tire and drag the pavement under the front towards rear.
To counter that argument, I would claim that the braking forces have to be opposite the direction of the wheel rotation, otherwise they'd make the wheel turn faster, not slower. And a skid is different from normal braking forces. If you crash, anything dragging along the ground is skidding, and the force is opposite the direction of travel, but its not due to braking.

What I'm not able to get my head around is how the brake pads and pavement combine in this force equation.
 
Top Bottom