How would your tyre hit your crown?
On the thread about sticking a big wheel in a little fork people started saying the tyre could hit the crown. I have been jumping up and down on my handlebars while riding along to see if I acould make it happen and I can’t.
As you can see from the photo I have absolutely minimal tyre clearance but I still can’t see what is going to bend, twist, deflect or otherwise to make the tyre reach the crown.
Advice welcome as I am going to be riding this around Afan shortly and would like to know the likelyhood of needing an air ambulance.Posted 9 years agogusamcMember
Scientific theory clearly dictates that at high speeds centrifugal force will increase the tyre diameter, alos, higher altitudes with lower air pressure will cause the tyre to swell, however so will lots of pies.
I think you should let the air out of the tyre and turn the wheel upside down, then the flat spot will always be at the top – hence no problem.Posted 9 years ago
Okay, how will my tyre hit the brace or anything hit the crown?
There is even enough clearance for the tyre to miss the frame when the fork is fully compressed.
i don;t really understand technology but someone was convinced that something would hit soemthing else on the front of the bike and I would die horribly.Posted 9 years agoscaredypantsSubscriber
the allen key is between tyre and brace, not tyre and crown. what people mean by the crown (here) is the very bottom of the steerer tube
you’re right, the tyre can’t hit the brace but as the fork compresses the brace and tyre move upwards towards the crown. at full compression the brace will likely be above the level of the crown but that’s OK since the brace sits in front (or soemtimes behind) the crown. the tyre, on the other hand, is right under it.
If your chosen wheel and tyre has a bigger diameter than the fork was designed for then the tyre might foul the crown (or even the down tube). if it does, the wheel might stop dead and chuck you over the top, especially as this will be on a major compression so you’d be unbalanced
If you really want to know, try taking the spring (or air) out of the fork & see if you can get the tyre to make contactPosted 9 years agor6ymyMember
As wwaswas said, it depends on the design of your fork.Posted 9 years ago
If they’re air forks let the air and and see how close the tyre is to the crown at full compression. If it’s very close, you might get contact on big hits as there will usually be bump stops – either springs or elastomers, that could compress a bit more.
scaredypants – You have explained it in a way I understand. I now feel a bit stupid. I will go and have another try at crashing the wheel into the crown now I know what I am trying to achieve.
PS Anyone see why it would be a bad idea at Afan (assuming it doesn;t hit the crown)Posted 9 years agogusamcMember
? wasn’t this something to do with discs, qrs and torsional whatever force ?
I **seem** (so I may be balking tollocks) to remember reading something about this and the way that a bigger wheel delivers torque to the qr may be different ?? – so it may impact the ability of the qr to hold – which could be a problem.Posted 9 years agoWackoAKMember
My mate put a 2.5 Kenda on his bike with Revelations (older ones) for going to the Alps, it spun ok when fitted but in use it rubbed at the sides. I recon you’d be ok assuming you have enough sideways clearance which it looks like you do.
Personally if it were me I’d not chance it the way it is at the moment.Posted 9 years agoscaredypantsSubscriber
Given the minimal difference in over all diameter of the wheel … The wheel doesn;t touch the crown BTW … , why will this cause a problem for the fork
If that’s right, then you should be OK (as long as it can’t hit the down tube either) – until phiiiil’s stick gets you !
(TBH, I reckon it’d be a fairly kack fork design that allowed a tyre to fit under the brace but still foul the crown. downtube fouling depends on frame AND fork so more variable)
the wheel/tyre is significantly lighter than the 26″ set I had before, why will this cause a problem for the fork
light is no worry, as long as it’s strong enoughPosted 9 years agosinglespeedstuSubscriber
TBH, I reckon it’d be a fairly kack fork design that allowed a tyre to fit under the brace but still foul the crown.
I recon it’d be a good design to have the brace high enough to allow plenty of mud buildup on the tyre….. 😉
As said above measure the distance from the tyre to the crown then compare that to the length of travel. Or let the air out/take the springs out and see if it clears.Posted 9 years ago
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