Topic: Front tire on the back?

[Industrial Cafe]

I'm sure this has been discussed before, but i cant find it.
                              and mods, if you wanna delete it go ahead.

here's a question for whoever has an idea.

can someone explain to me the disadvantages of a front tire on the back of a bike. because my Russian bike rolls on 2 fronts, and it's perfectly fine... no problems at any speed.

  Keep in mind, I don't care to take turns at 85mph like my gixxer friends, and I'm not drag racing anyone.
I'm just riding to work and around the desolate back roads of central Florida.

about 1.5-4 hours of normal riding a day.

[Retro Rocket]

My old GPX750 Kawasaki was raced with a comp K Michelin 16x130 rear tyre on the front and once again everyone said it was a bad idea but i came third outright and first in its class in the last Castrol six hour race held at Oran Park Sydney Australia. This bike was the best handling bike i had ever ridden and i had a couple of well known local racers ride it and were very impressed, so i suppose there's no reason it shouldn't work.

Mick

[Industrial Cafe]

hmm...

[754]

HD used same front and rear for 50 years on FL,s..

Your rotational arrows may be oriented to this..9 could be wrong on this);

The arrow mounts the wheel so that the greater force works in the direction the cords are laid, or fabric if used.. the premise being the rear has the most strain under accelration, ther front does under braking..

Maybe I just dreamt it up, but I think i did read that..

[333]

Okay.  Many have done it without a problem.  But here is the difference.  The belts are laid differently to accomplish difference things.  A front tire is designed to corner and brake.  A rear tire is made to accelerate and brake.  If you use a front tire on the rear, you must put it on the opposite direction of the rotation arrow.  If you don't do this, the belts could bunch up and create lumps, and then be unbalanced.  The other issue is braking.  Many are taught to mainly use the front brake, and this is especially true when using a front tire on the rear.

While I have never used a front tire on the rear, I did have to learn that last lesson the hard way.

[Industrial Cafe]

both of those sound valid...
I thought the arrows were for directional tread tires, so you didn't have problems in wet conditions. at least thats the word on car tires...

   Depending on if the road is loose or not, I barely touch the back brake. (like 70/30)

[Retro Rocket]

From memory, the rear tyre on the front of mine was reversed.

Mick

[Industrial Cafe]

huh, interesting...

[crazypj]

HD used same front and rear for 50 years on FL,s..

Your rotational arrows may be oriented to this.. (could be wrong on this);

The arrow mounts the wheel so that the greater force works in the direction the cords are laid, or fabric if used.. the premise being the rear has the most strain under acceleration, the front does under braking..

Maybe I just dreamt it up, but I think i did read that..

 Nope, you read it.
 Old style Universal fitments were bias belted and didn't care which direction they went
 When directional tyres first appeared they sometimes had two arrows in different directions for front or rear fitment.
 They were still bias ply bu the angles had changed and there was also a small possibility of tread seperation if fitted backwards ( saw it happen a couple of times but never to a serious extent, looked more like a cut across the tread)
Not sure if the Avon Roadrunner universal still has front and rear fitment on same tyre? (anyone got them fitted?)
I've done it more than once when putting MX bikes on dyno (most are 19" rear)
Haven't had any problems even at 120mph and heavily loaded.
Just make sure direction arrow is pointed backwards if your front is on rear (? )
 PJ

[736cc]

  Few years ago I bought a sandcast that the previous owner had grafted the rear tire and rim on the front hub. And mounted a car tire on the back...used boat trailer rear signals.....cut an inch off the rear shocks and welded them back together....and a few other curious mods before it got toasted in a shop fire. Just another rescue.
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[Industrial Cafe]

very useful information.
This will help greatly on my 21 inch cafe idea.

[Geeto67]

one thing that should be added here is tread pattern. Some tires are designed to be reversible (used both front and rear) others are one direction only, meaning to put them on backwards the rain grooves will not channel water away and could create a more dangerous situation. a lot of it has to do with the tire design and the frame/suspension design.

During and post WWII there was a lot of rationing and shortages, espcially of rubber and metal. Bikes designed during this period (HD, BMW, etc) were designed so that you could potentially use the same tire front and rear in a pinch if you needed to. If they were different sizes you could at least be assured that the front on your bike might be a rear on a smaller bike and vice versa. The shortages in England continued well into the 1950s and you find that tires there like avon speedmasters were designed to work as both fronts and rears. Take a look at all the vintage treds on this page:

http://www.britcycle.com/Products/555/555_series.htm

almost all of them have rain grooves that work in either direction. Your Russian bike is most likely a copy of a WWII era bmw since the russians liberated all the manufacturing dies, toolings, etc during the war and continue to make knockoff BMWs to this day (the chinese do as well) so it is at home running the same tires front and rear.

With the advent of modern tread technology you get uni-directional tread patterns, patternd designed to push water and other slick road substances away from the contact patch. If you reverse this pattern you will find that the channel does not work as well or will actuall trap water at the center of the contact patch. Avon venoms or Metzler lazertechs are a good example of these, their grooves toward the edge of the tire but they only work if the center groove gets there first.

Some tread patterns behave differently when you mix them front and rear. For some reason cb750s need to have a ribbed tire on the front or the heads shake on deceleration, if you run a mismatched tread in the rear this could be made worse (or better - it is hard to say since the manufacturers do not test mix and match with other manufacturers tires). there is a lot of distortion in a tire (it grows the faster you spin it) and tires that distort at different rates or tread blocks that transfer strange forces to the front tread blocks can make the situation worse (or sometimes better).

[Geeto67]

My old GPX750 Kawasaki was raced with a comp K Michelin 16x130 rear tyre on the front and once again everyone said it was a bad idea but i came third outright and first in its class in the last Castrol six hour race held at Oran Park Sydney Australia. This bike was the best handling bike i had ever ridden and i had a couple of well known local racers ride it and were very impressed, so i suppose there's no reason it shouldn't work.

Mick

Comp Ks were exceptional tires for the time, extremely sitcky and just all around ahead of their time in terms of distortion and heat retention. I had a set on the 1986 1000r ninja and I wore them bald because they were so good. for some reasone kawasaki chassis's really liked them more than other bikes, a buddy had a set on his fzr1000 and he did not like them so much. I finally got rid of the Comp K on the ninja last year - well past its prime and it was still a great tire.

[Industrial Cafe]

that's what I was thinkin when I mentioned the directional tread on car tires.
backwards sucks in the rain. I had a guy at work make that mistake, he hydroplaned easily till we told him about it.

I've had that deceleration wobble on my bridgestone spitfires, I always wondered why, didn't think of the tire.
 I already figured on looking for a non directional tread pattern, cause I think I wanna go for a retro, steampunk look. (think autonomous clockwork robots with laser guns)