Intriguing tyre theory

I have posted my Trident T150V Special in the classic section . And it was Splatt that suggested that I rotate my front as it is / was back to front ~

I even marked the rim rotation for the bike dealership to get it right on the day but never checked their handy work till Splatt and another tripler pointed it out..


I just got back home after getting the tyre rotated on the front wheel at the local bike shop ~

While I was waiting I ducked down to the SS Bolt man’s shop for a yarn ~

During this session , the issue came up about whether a front tyre should in fact be fitted A about T on purpose. (Initially this theory was applied to Hurley D's.)

The theory came from an experienced tarmac road racer ~

His theory is that based on riding style ` that is higher speeds , he asked .. When do you / we need maximum handling ability ~

Answer when we brake ~~ particularly at speed ~ and even more so int he wet of course ~

And when one brakes your body weight and bike are forging forward... but you essentially want the tyre / wheel to retard in a motion equivalent of going backward..

Thus the front tyres essentially needs maximum grip !!! As stated even more so in the wet ..


So fit the front tyre A about T

BTW the way the receptionist at the bike shop was ever so apologetic ~ I said why , not you r fault... when I came back she is still apologising ....

I said not your fault... she said- well we fitted it!! No... It was fitted in Cairns... OH!!! How much... (Quoted me $30 yesterday ).. Ahh don’t worry about it ~

( So there is some reward for buying at the same outlets ... lol)

I always thought that the direction of a tire was in relation to how the cords were wrapped and running them the opposite direction was more likely to cause them to fail from a cord separation. You were supposed to have the maximum strength applied to stopping with the front tire and acceleration on the rear tire. ? Jim

Yes the tyre is basically a flat band that is rolled into a circle with one end overlapping the other.
As the tyre is forced in one direction under acceleration the overlap is pushed together.
Same tyre on the front has to be reversed so the braking force pushes the overlap together.
If a tyre is fitted the wrong way around probably nothing would happen, but in theory the tyre would be trying to pull the overlap apart.

Nothing to do with tread pattern.

Some tyres, especially skinny older type ones, are marked with arrows for fitment in opposite directions so the tyre can be fitted to the front or rear wheel.

Graeme

Of course this all depends on what the tyre manufacturer recomends. They know best.

BTW .. the tyre is an Avon Roadrunner ~ and actually has opposite arows for front and rear..

your friend should urgently warn Avon , Bridgestone , Dunlop , Michelin ... that they got it all wrong !..

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Ludwig

My sentiments exactly ~ but then I was rubbing shoulders here with Hurley Furguson riders.. I think I can rest my case .... after all they are ruthless.. immaculate and infallible machines ~ :shock:

I once fitted the front wheel on my mountain bike backward , it had a directional tyre, awsome steering down hill in gravel, until I hauled on the front brake, nearly no steering control, stopped straight away and rotated wheel, so now I only fit as the instructions .

Good call I am thinking Splatt ~

Tire tread pattern is also designed based on position on the bike. If you look at a modern sport bike with matched tires, you'll see the tread patterns are reversed - the front designed for maximum traction/water shedding under braking, the rear under acceleration.

I've also reasoned why rear tires wear out so much faster than front tires:
Both tires are exposed to rolling resistance and lateral friction loads when cornering, but the front is only exposed to high friction loads when braking. The rear is exposed to these loads whenever accelerating, engine braking, or rear braking. Even when cruising at a steady rate, the rear tire is exposed to more friction than the front, because it still has to push the bike through the wind, AND overcome its own rolling resistance plus the front tire's rolling resistance.

Even though the front tire on my Triumph is a 120/70 and the rear a 180/55, the rear lasts about 5000 miles, while the front goes over 9000.

On the Norton, the front is barely half gone after 10,000 miles, but the rear is finished with its second K81. I'm switching to Avon AM26s next week in hopes of a better ride over drawbridges and tarmac seams. I figure the radical difference in wear is the amount of work the rear tire does in acceleration, engine braking, and rear braking.

BillT said:

Tire tread pattern is also designed based on position on the bike. If you look at a modern sport bike with matched tires, you'll see the tread patterns are reversed - the front designed for maximum traction/water shedding under braking, the rear under acceleration.

I've also reasoned why rear tires wear out so much faster than front tires:
Both tires are exposed to rolling resistance and lateral friction loads when cornering, but the front is only exposed to high friction loads when braking. The rear is exposed to these loads whenever accelerating, engine braking, or rear braking. Even when cruising at a steady rate, the rear tire is exposed to more friction than the front, because it still has to push the bike through the wind, AND overcome its own rolling resistance plus the front tire's rolling resistance.

Even though the front tire on my Triumph is a 120/70 and the rear a 180/55, the rear lasts about 5000 miles, while the front goes over 9000.

On the Norton, the front is barely half gone after 10,000 miles, but the rear is finished with its second K81. I'm switching to Avon AM26s next week in hopes of a better ride over drawbridges and tarmac seams. I figure the radical difference in wear is the amount of work the rear tire does in acceleration, engine braking, and rear braking.

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Someone should do a thesis on this, I get the same results with a bicycle, I can go twice the distance on a front tire compared to what I can get on a rear, I always thought it was because there was more weight being carried by the rear (rider, bags...), even on motorcycles, while sitting one or two up, there is more weight on the rear than on the front no?

Jean

It takes pretty high load to make tire rotation matter and then unless racing the most it does in put a bulge distortion in tire to annoy and wear faster. Bicycles with higher load concentration on narrow tires would be more susceptible to this.
Wet or dry tire grooves on pavement have more to do with marketing appeal than functional purpose -basically though the less grooves the better all around. Cycle tire patches are canoe shaped to part water innately better than flat car tire.
Grooves may give .5 mph speed increase before hydro planing, in other words no real safe advantage to trust if hitting just a tad deeper layer - water skiing.
Not my opinion just restating much looking into this.

Of course rear wears faster with constant torque applied plus rear torque lifts loads off front. Front mostly wears from the slight slipping it must do in counter steering pointing it to outside of turn while rear tire is trying to go the right way around. Neutral handling bikes only need an instant of counter steep to help tip bike against the gryo forces then can. If you can lean bike by body english forks will straight steer automagically. Air balance front to back matters too, rear should be aired harder than front or front ends up doing more work and scrub.

To extend my rear tire life I mostly do slow to fast lane weaves when all by myself. Never use engine drag or rear brake on good surfaces and only accelerate much when leaned pretty good, often combined with above weaving which police don't like to see.

BillT

Avon AM26s next week in hopes of a better ride over drawbridges and tarmac seams.

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I think you will be impressed with the handling of the AM26s ~ I first used a t120 with Am26s fitted a Three day triples rally, leant by a mate from Sydney and I was blown away ! Afew people came up to me and made the comment that it looked like I was having an absolute ball on the Bonnie ~ lol

(All the Brit bikes I have owned or ridden sported Dunlops ~ )

This influenced me to putting Am26s on the Trident resto ~ the drawback I believe is that the puppies do not wear nearly as long as the Dunlops..

I've been through quite a few AM 26s now and what I do when the rear wears out I move the front to the rear and fit the new one to the front. Works for me. And you don't replace two tyres at once.